    [From the U.S. Government Printing Office, www.gpo.gov]

      c~oas'tal  Lonedel Minlifurn
       Cent~er   ___    rricane
                      Resistsant

                      for thelTexas

    4iI

                           Property of cSC Library

       MODEL MINIMUM HURRICANE-RESISTANT BUILDING STANDARDS

                         FOR THE TEXAS GULF COAST

                            U. S. DEPARTMENT OF COMMERCE NOAA
                            COASTAL SERVICES CENTER
                            2234 SOUTH HOBSON AVENUE
                            CHARLESTON, SC 29405-2413

                                  CONDUCTED BY
                     THE TEXAS COASTAL AND MARINE COUNCIL

                    SENATOR A. R. "BABE" SCHWARTZ, CHAIRMAN
                      JOE C. MOSELEY II, EXECUTIVE DIRECTOR

                propeOrty of CSC Library

                             General Land Office of Texas
                             Bob Armstrong, Commissioner

    U. S. DEPARTMENT OF COMMERCE NOAA
    COASTAL SERVICES CENTER
    2234 SOUTH HOBSON AVENUE
    CHARLESTON, SC 29405-2413

                                 SEPTEMBER, 1976

         This study was funded in part through financial assistance provided by the Coastal Zone
    g 'L/Management Act of 1972, administered by the Office of Coastal Zone Management,
    ,.  National Oceanic and Atmospheric Administration.

     -~~~~3COASTAL AND MARINE COUNCIL

                         July 21, 1976

    Son. A. R. "Babe" Schwartz
                Chalvestn  The Honorable Bob Armstrong
                         Commi ssioner
        Richard Keith Arnold   General Land Office
                 Austin   Stephen F. Austin Building
    Truman G. Blocker, Jr., MD   Austin, Texas
               Galveston
                         Dear Commissioner Armstrong:
        John C. Calhoun, Jr.
            College Station   Enclosed is a copy of the report entitled, "Model Minimum Hurricane-
              Sen Ry Fraee Resistant Building Standards for the Texas Gulf Coast," that the
            Wichitay Fallse   Texas Coastal and Marine Council contracted to produce for the
                Wicit Fals General Land Office under the terms of IAC(76-77)717.
          James J. Flanagan
              Port Arthur   This report contains three principal efforts:

        Sen. Roy Harrington   a  An analytical procedure for determining the degree of
                   Port Arthurexposure to reasonably "probable" hurricane conditions
             Joe S. Harris       along the Texas coast.
    V  ~~~~~~   Austin
           Edward H. Harte    *  A model minimum building standard, in a building code
            Corpus Christi       format, that, if implemented as an adjunct to common
                                 codes--such as the Southern Standard Building Code--
         Mrs. J.W. Hershey       should reduce damages due to hurricane forces.  Application
                Houston          of these standards would raise the building cost only
        Rep. Joe A. Hubenalk     3-8%.
                   Rosenberg  A thorough discussion of the natural hazards of the
          Robert L. Massey       Texas Gulf coast.
                  I nez
             Rep Grg ontyaThe Council is also working on a similar effort Linder a mandate of
           R~~Elsrg~noa   the Texas Legislature (S.R. 268) to develop model minimum standards
                      Ela and to examine other related issues.  This report is due in about six
          Rep. Pike Powers   months.  We would appreciate receiving copies of any comments that
               Beaumont   you may receive on this report for incorporation into our report to
                         the 65th Texas Legislature. We are currently reviewing this
        George Fred Rhodes   document in detail with the affected professional groups (engineers,
              Port Lavaca   contractors, architects, insurance and local government) and
           Charles P. Turco   anticipate some revision.
               Beaumont
               JoeC. oseeyIf we can be of any further assistance on this matter, please let
          Executive Director m nw

                         Sincerely,

                            Jo .Moseley II, P.E."
                       POST OFFICE BOX 13407/AUSTIN, TEXAS 78711I/PHONE (512) 475-5849

                             TABLE OF CONTENTS

                                                                  Page

    Preface ..................................................... i

    Section I - INTRODUCTION - Countering the Hurricane Hazard
        with Special Building Practices ........................ 1-1

    Section II - NATURAL HAZARDS OF THE TEXAS COASTAL ZONE

        INTRODUCTION ........................................... 11-1

        HURRICANES ............................................. 11-4

        FLOODING ............................................... 11-16

        SHORELINE EROSION ...................................... 11-23

        LAND-SURFACE SUBSIDENCE ................................ 11-30

         FAULTING ............................................... 11-35

         CONCLUSIONS ............................................ 11-39

         SELECTED REFERENCES .................................... 11-40

    Section III - HAZARD ZONE DELINEATION FOR STANDARDS AND CODES 111-1

         Annex A - Computation of Hurricane Tides at the Open
           Coast ................................................ III-A-1

         Annex B - Conceptual Basis for Computing Inland Flooding III-B-1

         Annex C - Procedures for Computing Inland Flooding ..... III-C-1

    Section IV - MODEL MINIMUM STANDARD

         CHAPTER 1 - INTRODUCTION ............................... IV-1

         CHAPTER 2 - ADMINISTRATION ............................. IV-3

         CHAPTER 3 - DEFINITIONS OF TERMS ....................... IV-20

         CHAPTER 4 - HURRICANE HAZARD ZONES ..................... IV-24

         CHAPTER 5 - WAVE AND SCOUR ACTION ...................... IV-26

         CHAPTER 6 - BATTERING BY DEBRIS ........................ IV-32

         CHAPTER 7 - FLOODING ................................... IV-33

         CHAPTER 8- WIND ....................................... IV-65

         CHAPTER 9 - FOUNDATIONS ................................ IV-83

         CHAPTER 10 - MASONRY WALLS ............................. IV-85

         CHAPTER 11 - STEEL AND IRON                                ............................ IV-87

         CHAPTER 12 - WOOD ...................................... IV-89

         CHAPTER 13 - CONCRETE .................................. IV-91

         CHAPTER 14 - CLADDING AND GLAZING ...................... IV-93

         CHAPTER 15 - ROOF COVERING ............................. IV-95

    Selected References - HAZARD ZONE DELINEATION ............... IV-98

    Selected References - MODEL MINIMUM BUILDING STANDARDS . ..... IV-100

    Municipalities Using the Southern Standard Building Code .... IV-102

                               PREFACE

         Hurricanes have been a major threat to life and property
    along the Atlantic and Gulf coasts. Although catastrophic loss
    of life has been avoided since the 1900 Hurricane killed 6,000
    persons in Galveston, Texas, conditions are now developing
    which lead officials to fear another major killer. The contributing
    factors include the following:

         * Rapidly increasing development in low-lying coastal
            areas, many of which are reachable only over long
            stretches of exposed low highways.

         a Massive influx of persons from non-coastal areas
            who fail to appreciate how devastating a major
            hurricane can be. This problem is compounded by the
            fact that many persons have experienced a near
            miss or only a minor storm and thus have a casual
            attitude toward these storms.

         * Warning systems have improved much in recent years,
            contributing to complacency among both officials
            and the public. However, a plateau has been reached,
            and additional significant improvements are not
            anti ci pated.

         The best way--from a technical, political, and economic
    standpoint--to significantly reduce hurricane damage on a wide
    scale is through the use of hurricane-resistant building
    practices.

         If proper standards are developed and thoughtfully applied in
    a manner consistent with the exposure to hurricane dangers, damage
    can be greatly reduced at a modest cost. Since a substantial
    portion of the population inevitably refuses to evacuate during a
    warning, the use of stronger structures will obviously result in
    lower loss of life during the storms.

         This report was prepared to serve two purposes:

         1.  Develop for the Texas Coastal Management Program of
              the General Land Office hurricane-resistant building
              standards as part of their overall coastal management
              program effort.

         2.  Partially satisfy the requirements of S.R. 268, which
              calls for examination of hurricane hazards, develop-
              ment of hurricane-resistant performance criteria,
              drafting of a model minimum building standard, and

                                   i

              preparation of institutional alternatives for
              implementation.*

        While this procedure and these standards were developed with the
    Texas coast in mind, almost all elements are generally applicable
    for all coastal states from Texas to Maine.

        To accomplish the tasks set out in S.R. 268, a group of
    experts was assembled. Those persons, along with their principal
    responsibilities, are as follows:

         1.  Determination of Hazard Areas and Types of
              Destructive Forces Associated Therewith:

              Dr. Robert Simpson, consulting meteorologist,
              former director of the National Hurricane Center
              of the National Weather Service and world-renowned
              hurricane expert. Dr. Simpson was responsible
              for devising the overall methodology for
              delineating hazard areas. Dr. Robert Morton,
              Bureau of Economic Geology, University of Texas
              at Austin. Dr. Morton shared the responsibility
              for delineating hazard areas and provided
              guidance on geological conditions and development.
              Dr. John Freeman, director of the Institute for
              Storm Research, University of St. Thomas in Houston.
              Dr. Freeman, in cooperation with Dr. Simpson,
              developed the technique for determining the
              inland boundaries of surge distribution.

         2.  Drafting of Model Minimum Building Standards:

             Mr. Herbert Saffir, P.E., consulting engineer,
              Coral Gables, Florida, a well-known expert on
              hurricane resistant codes. Helped to set minimum
              standards and assisted with standards development.
              Dr. Charles Hix, P.E., consulting engineer and
              staff member of the Engineering Extension Service,
              Texas A&M University. Dr. Hix drafted the model
              standards. Mr. James A. Goldston, P.E., President
             of the Goldston Construction Company, Corpus
             Christi. Served in a consultative capacity to
              insure that decisions/actions were reasonable in
             view of construction practices and conditions
             along the Texas coast.

         3.  State government officials involved in the
             preparation of this report were: Mr. Art Eatman,
             P.E., of RPC, Inc., who served as project

     Follow-up work is continuing in a report of the other aspects
     that will be ready to submit to the Texas Legislature in
     January of 1977.

                                 ii

    officer for the General Land Office. Mr. Frank
    Cox and Mr. Ashley Eledge, Governor's Office,
    Division of Disaster Emergency Services, served
    as liaison with that office. The Division of
    Disaster Emergency Services is responsible for
    disaster planning. Dr. Joe Moseley, P.E.,
    Executive Director of the Texas Coastal and
    Marine Council, was responsible for overall
    conceptualization and management of the project.

                                           SECTION I

                                        I NTRODUCT ION

                        Hurricanes pose a very significant threat to lives
                   and property in coastal areas. Texas is hit by a hurricane
                   on the average of once every other year. Only recently has
                   attention in coastal management deliberations been focused
                   on hurricane hazards.

                        Development in Texas' coastal areas is increasing,
                   and this trend will continue. This is to be expected, as the
                   coast offers many economic and aesthetic amenities. Since
                   hurricanes are inevitable, it is desirable to develop hazard-
                   prone areas in a fashion that will (a) avoid as many hazards as
                   practical; (b) withstand those forces that cannot be avoided
                   when economically feasible; (c) absorb the inevitable losses;
                   and (d) most important, reduce the loss of life as much as
                   possible.

                        One viable way to accommodate growth in high-risk
                   areas is to develop and implement minimum building standards
                   that will reduce the hurricane risk to life and will reduce
                   the risk to property to an acceptable level and in an
                   equitable manner. Such action sounds deceptively simple
    *              ~~~~but requires a complex and controversial mix of scientific,
                   engineering, legal and political actions. This report
                   presents such an approach. Principal elements include:

                        * A discussion of the hurricane-related processes
                           impacting the Texas coast;

                        * A description of the nature and magnitude of the
                           destructive forces associated with the hurricane
                           process, and the synthesis of parameters for a
                           ''Texas Design Hurricane;`

                        * An analytical procedure, based upon accepted
                           scientific methods, for spatially delineating the
                           varying degrees of exposure to the design
                           hurricane's destructive forces in coastal areas--
                           i.e., establishing "hazard zones;"

                        * A set of minimum performance criteria for structures
                           in each of the hazard zones, and

                        * A draft minimum model building standard which
                           complements the Southern Standard Building Code
                           and which contains hurricane-resistant wind and
                           flood requirements which are compatible with
                           accepted design and construction practices and

                                             1-1

            economic realities. This model can be used to
            implement the performance criteria in each hazard
            zone.

    MODEL STANDARDS

         Actions by other entities, standard engineering practices,
    and experience were all heavily relied upon in an attempt
    to make the product--i.e., the MODEL HURRICANE BUILDING
    STANDARDS--as practical as possible. The result is a model
    code that is:

         *  Based on common design and construction practices
            with minimal modifications for wind-resistant and
            flood-resistant requirements (where applicable);

         a Readily usable by practicing architects and
            engineers with a minimum of special efforts;

         e  Very economical to the builder/consumer.   (Without
            any cosmetic frills,* it is estimated that the use
            of this standard, with its hurricane-resistant
            provisions, will add a maximum of 3-8% over the
            basic structural cost of the same building constructed
            to the Southern Standard Building Code now commonly
            used.**)

         *  In its present form, the Model Standard could be
            easily adopted by local governments, and, if they
            already use the Southern Standard Building Code,
            incorporation of these special provisions would be
            very simple.

    LEGAL AND INSTITUTIONAL CONSIDERATIONS

         Under Texas law, municipalities have the power to
    adopt ordinances, including building codes. With few
    exceptions, counties do not have this power. Thus, under
    existing law, implementation of building standards will

      *Opponents of any special hurricane-resistant codes often
       point to codes like that used in Coral Gables., Florida, and
       note that use of such a code may greatly increase the cost
       of a structure. However, such codes frequently contain many
       additional provisions for architectural appearance, etc.,
       that have nothing to do with hurricane resistance. A special
       analysis is underway which develops detailed cost estimates
       for common coastal structures, both using and not using these
       special hurricane-resistant standards. It will be ready by
       December, 1976.

     **Appendix C to Section IV contains a listing of Texas coastal
       municipalities using the Southern Standard Code, and other
       common Texas practices.

                             I-2

    generally fall to coastal municipalities. Legislative action
    could extend this power to coastal counties, if it were
    politically palatable. The state, although it has no general
    authority to set or enforce building codes, can do so in
    special hazard situations, such as under the disaster
    planning and special, high-risk insurance statutes.

         Hurricanes Carla and Celia caused many coastal residents
    to lose their insurance. As a result, the Legislature
    established the Texas Catastrophe Property Insurance Pool
    Act (passed in 1971) which requires all property insurers
    in the state to pool their resources and provide insurance
    in high-risk areas. Special rates may be charged in the
    high-risk areas, and upon approval of the Insurance Board,
    special building requirements may be imposed in such areas
    as a condition of insurability.*

         The 1973 Texas Disaster Act, which was updated in 1975,
    was the first of its kind in the nation, and brings a major
    new dimension to the state involvement with disasters.
    Previously, virtually all state disaster and civil defense
    activities had been oriented to rescue, relief and recovery.
    The new law stresses preventive measures by establishing
    a new policy and setting up new administrative and legal
    mechanisms. One provision specifically authorizes the
    governor to suspend any local building code or land use
    ordinance and place one of his own choosing in effect if he
    finds a disaster or a threat of disaster. This would include
    imposition of such requirements in areas where none now
    exist. Implementation is still in its infancy, and, since
    some of the preventive steps will be unpopular in many
    quarters, it is impossible to preduct the ultimate effective-
    ness of this law.

         In 1975 the Legislature passed a resolution (S.R. 268)
    which mandated the development of model minimum building
    standards for high-risk coastal areas. This report is part
    of the response to that mandate.

         The federal government has many programs and policies
    that relate to disaster exposure, risk and recovery. The
    Corps of Engineers has countless projects aimed at the
    construction of protective facilities to minimize damage
    from flooding and erosion. The nationally subsidized federal
    flood insurance program, which requires participation of any
    new construction utilizing federal guaranteed loans, requires
    local governments to adopt flood management programs. This
    has been unpopular in many quarters, and the ultimate effect
    is uncertain.

      *This provision has never been utiZized, although there is
       currently (Summer '76) an effort to apply it to mobile
       homes. Some believe this needs clarification.

                             I-3

         The Disaster Relief Act of 1974 constitutes a major
    change in the federal approach, shifting much emphasis
    from recovery to prevention. Relatively little has been
    done by the responsible agency, HUD, to implement this
    law. When such an attempt is made, there may be more
    protest than there was over the flood insurance program. Another
    well-known federal effort is the hurricane warning system
    headed by the National Weather Service.

         While strong governmental actions are theoretically
    possible--such as a construction moratorium in high-hazard
    areas or the direct establishment and enforcement of state
    building codes--they are unlikely. Such actions would
    raise Constitutional questions about the use of private
    property, and could severely restrict the opportunity of
    citizens to use and enjoy coastal resources. Considering
    the size and diversity of the Texas coastal area, such actions
    would be impractical to administer. More realistic avenues
    are available.

         * Increased public awareness of the potential
            hazards and actions that individuals can take
            to counter them is a first step. Two specific
            actions should be explored: (a) the current
            Hurricane Awareness Program should be continued
            for current coastal residents, and (b) a
            disclosure of potential hazards should be
            provided to all new residents. The purpose of
            the latter is not to "scare" potential buyers
            away, but to inform them of hazards and appro-
            pri ate countermeasures.

         * Insurance availability and cost should be tied
            to the strength of a given structure, and its
            exposure to a hurricane hazard. Currently, the
            Texas Catastrophe Property Insurance Pool Act
            has very nebulous provisions for basing rates
            on the strength of a structure and none on
            its degree of exposure except in the Pool area.
            The possibility of such an amendment should
            be examined.

         * The current mix of federal and state disaster
            related programs is very complex. In some cases,
            the laws and regulations seem to work against
            each other, or even to promote the creation of
            "disaster-prone" situations.* The state should
            make a careful assessment of the impact of these
            programs.

     *Assessment of Research on Natural IHazards, G.F. White
       and JT.E. Haas, MIT Press: 1975.

                              I-4

         These and other matters are still being considered by
    the Texas Coastal and Marine Council as part of its legislative
    mandate under S.R. 268. The report on this is due in December,
    1976.

    DELINEATION OF HAZARD ZONES

         A first step in developing a hurricane-resistant building
    standard is to spatially describe the physical forces of the
    hurricane in a quantitative manner. Much work has been done
    on the subject. A relatively simple procedure was developed
    to be used in conjunction with developing and applying minimum
    hurricane-resistant standards. This procedure utilizes a
    combination of analytical procedures and prima facie conditions*
    and draws heavily on existing practices.

         The result is four "zones," reflecting four different
    levels of exposure. They are:

         Zone A - Scour
                - Battering with Debris
                - Flooding
                - Wind (140 mph)

         Zone B - Battering with Debris
                - Flooding
                - Wind (140 mph)

         Zone C - Flooding
                - Wind (140 mph)

         Zone D - Wind (140 mph)

         Figures 1-1 and 1-2 illustrate the four zones and the
    type of destructive forces present in each. Section III
    is devoted entirely to how to determine the degree of
    exposure and Section II contains an extensive discussion of
    the processes involved. A brief discussion of a typical
    situation in each exposure zone is useful.

         e Zone A: An example of Zone A may occur on a
                     barrier island and near the beach. The
                     full fury of the storm's wind obviously
                     strikes here. Much of the area is likely
                     to be below 15 feet above sea level, and
                     flooding is very possible. The waters
                     could be moving at a velocity of several
                     knots and be topped with violent waves
                    of 5-10 feet. The water mass itself can
                     exert a significant force, but this is
                     compounded greatly with floating objects

      As used herein "prima facie conditions" refer to physical
       evidence, meteorological, geological, topographical, or
       hydrological, which may be in disagreement with the analytical
      results. In such cases, the specified prima facie evidence
      will govern.
                            I-5

                    such as boats, vehicles, parts of
                    other structures, etc. Few, if any,
                     residential structures could be expected
                     to survive the impact of a one-ton
                     object moving at 10 feet per second
                     (7 miles per hour). This violent water
                     action can also be a very effective
                     "ditch digger" and cause scour around
                     foundations, walls, etc., and undermine
                     structures that would otherwise survive.
                     Figure 1-3 shows what kind of damage
                     scour can do. While this condition will
                     usually occur on a barrier island or on
                     a Gulf-front area of the mainland where
                     there is no barrier island, it could also
                     occur on the shores of the major bays.

        o  Zone B:  The middle part of a barrier island, not
                    at an exceptionally high elevation, and
                    away from a washover channel would likely
                    fall into Zone B. Such a place would be
                     subject to the same destructive forces as
                    Zone A, except scour, and could be
                     located on the mainland near a bayshore.

        a Zone C:  This zone could occur on the mainland at
                     a considerable distance inland. Hurricane
                     Carla (1961) caused saltwater flooding
                     10-15 miles inland across the low-lying
                     coastal plain. Flooding is apt to occur
                     even further inland along the many bayous,
                     streams and other watercourses.

        *  Zone D:  Hurricane force winds (74 mph) may extend
                     hundreds of miles inland. However, the
                     extreme winds, i.e., 140 mph, begin to
                     reduce rapidly as the storm loses energy
                     as it moves over land. A procedure is given
                     in Section III for estimating this wind
                     reduction away from the water.

        These hazard zones are defined for a fairly narrow purpose:
    to enable a competent engineer to estimate the physical forces
    that are likely to be encountered at a specific building site.
    This information is then used to select the proper specifications
    from the model standard. When the specific parameters from the
    "Design Hurricane" are used in the analytical procedure, the
    result will be a location in one of these zones.

                             1-6

                          WIN
                          'tur

                               FIGURE I-1

    TYPES OF HURRICANE DAMAGE FOR DIFFERENT DEGREES OF EXPOSURE
          ~,"~.~ll~~l ~..,-,               ~.~,2  ,,---   --'--B-.. ..
              ~~~~~~~~~~~~~

           ...~.-~                                                    `

                     '-' b~~'-   -~"       ~~'~ - -'- '~.' ._~~---vc~'   -
                      ov~~IGR          I-1
       TYE F URCAN DgAMAG F O IFEET   ERESO XPSR

                                W(IN                  Zones
                                <T40 MpI

                                                    A.
                  I-  --          . - - N~WIND
                                                    FLOODING
                        j~~:~ ..ii.....ii .ii.i .......ii    BATTERING
             S    CO R   ::                          SCOUR

                                WIND
                                140 MPH
                              C--.--7               B.
                                                    WIND

                                       BA> X NBA-fTErIN6

                                 WIND
                                 140 MPH

                                                   C.
                             -                      WIMD
                                                    fLODDING

                                  WIND
                                 140- 0I0MPH
                                    <";            D

                                   .-~~~ v           WI ND

                        FIGURE I-2
                   (SAME AS FIGURE II-1)
    SCHEMATIC REPRESENTATION OF HAZARD ZONES A TO D IN
                   TEXAS COASTAL AREAS.

                            I-8

    ~~IAVE SC~~~~i~JR                                         STR~~UtTURES
            -AEN1M

                              SECTION II

       NATURAL HAZARDS
                        OF THE
    TEXAS COASTAL ZONE  --:

         L. F. Brown, Jr., Robert A. Morton, Joseph H. McGowen, Charles W. Kreitler, and W. L. Fisher

                                                              *CONTENTS.

    Introduction                         I                                   Shoreline erosion                                            23
        General statement                     I                                  General statement                                        23
        Natural hazards and land use                              3              Shoreline monitoring program                             23
        Natural hazards of the Texas Coastal Zone                 8              General methods and procedures                           23
        Acknowledgments                                           3                  Definition                                           23
    Hurricanes                                                    4                   Sources of data                                     23
        General statement                                         4                  Procedure                                            23
        Development of tropical cyclones                          4                  Factors affecting accuracy of data                   24
        Characteristics of hurricanes                             5                       Original data                                   24
        Related storm effects                                     7                           Topographic surveys                         24
             Changes in water level                               7                           Aerial photographs                          24
             Waves                                                7                       Interpretation of photographs                   25
             Development of washover (breach) channels            7                       Cartographic procedure                          25
             Rainfall                                             8                           Topographic charts                          25
             Wind                                                 S                           Aerial photographs                          25
        Generalized hurricane model                               S                      Measurements and calculated rates               25
             Storm approach                                       S                   Justification of method and limitations             26
             Landfall                                             S              Results of historical monitoring program                 26
             Hurricane aftermath                                  9                   Gulf shoreline erosion                              26
        Types of hurricanes                                       9                  Bay shoreline erosion                               27
             Hurricane Carla                                      9              Factors affecting shoreline changes                      27
             Hurricane Beulah                                    10                  Climate                                              27
             Hurricane Celia                                     11                  Storm frequency and intensity                        28
        Factors influencing severity of hurricane impact         11                  Local and worldwide sea-level conditions            28
             Nature of the storm                                 11                   Sediment budget                                     28
             Shoreline characteristics                           12              Factors aggravating erosion                              29
             Population density                                  14              Long-term trends in shoreline position                   29
        Prediction of severe hurricane damage                   14              Potential mitigation of shoreline erosion                29
            Mitigation of hurricane impact                       14          Land-surface subsidence                                      30
    Flooding                                                     16              General statement                                        30
        General statement                                        16              Cause and mechanisms of land subsidence                 31
        Flooding processes                                       17              Extent of land subsidence                               33
             Hurricanes and tropical storms                      17              Problems caused by land subsidence                       34
                 Storm-surge tides                               17              Mitigation of land subsidence and associated problems  34
                 Rainfall flooding                               17         Faulting 3
             Frontal-related storms                              17              General statement                                        35
        Flood-prone areas                    i          s                        Extent of active faulting                               35
             Storm-surge tidal flooding             i       s                    Identification of active faults                          35
             Stream flooding and ponding                         20    Gooi                          otoso   alig3
             Predicting flood-prone areas                        21              Gooi   otoso   alig3
         Mitigation and aggravation of flooding                  21               Methods of fault activation                             36
             Natural flood protection                            22              Mitigation of problems associated with faulting          38
             Land use and coastal flooding                       22          Conclusions                                                  39
             Flood prevention structures                         22          Selected reference                                           41

                      *   INTRODUCTION  *                               The  Texas  shoreline  is characterized  by  inter-
                                                                 connecting natural waterways, restricted bays, lagoons,
                                                                 and estuaries, low to moderate fresh-water inflow, long
                                                                 and narrow barrier islands, and extremely low astro-
                                                                 nomical  tidal  range.  Combined  with  these  natural
         The Texas Coastal Zone is marked by diversity in           coastal  environments  are  bayside  and  intrabay  oil
                                                    gIis richly   fields,  bayside  refineries  and  petrochemical  plants,
                   geogrphyresorcesclimte,  nd inustr. Itdredged intracoastal canals and channels, and satellite
    endowed with extensive petroleum reserves, sulfur and
    salt, seaports,  intracoastal  waterways,  mild  climate,       industries.  Exploration and  development  of offshore
    good  water  supplies, abundant  wildlife, rich agricul-        oil and gas resources are also under way.
    tural  lands,  commercial  fishing  resources,  unusual
    recreational  potential, and large tracts of uncrowded                     Tea  foastaliZon, hati        on, an    recre
                                                                 area for industrialization, urbanization, and recre-
    land. The  Coastal Zone, as herein defined, is a vast           ational development.  The zone is characterized by a
    area of about 18,000 square miles, including approx-
    imately 2,075 square miles of bays and estuaries, 367           chemic                       al  physical  concern and
                   mile   ofGulfcoatlin,  ad  1,00   ilesof   ay,  chemical  processes.  Of  critical  concern  to  Texans,
                                                                 however, are those natural processes which constitute
    estuary,  and  lagoon  shoreline  (table  1).  About  a         hazards, both to property and life in the Texas Coastal
    quarter of the State's population and a third of its            Zone. This atlas is dedicated to a better understanding
    economic  resources are concentrated  in the Coastal            of these natural hazards, their processes, impact, and
    Zone, an area including about 6 percent of the total            possible mitigation.
    area of the State.
                                                                      Texas is subjected to a diversity of natural haz-
                                                                 ards, most of which impact upon the dynamic Coastal
         Table 1. Statistical information for the area covered by   Zone and immediately adjacent inland areas. Principal
    the  Natural  Hazards Maps.  All data by Texas Bureau of        among these natural hazards are (1) shoreline erosion,
    Economic Geology, except areas of Hurricanes Carla and Beulah (2) land-surface  subsidence,  especially in the upper
    salt-water flooding and areas of Beulah rainfall flooding. After  Coastal  Zone, (3) frequent and damaging hurricanes,
    U. S. Army Corps of Engineers (1962, 1968).                     (4) flooding from streams and hurricane-tidal surges,
                                                                 and (5) active surface faulting. Each of these hazards
      Number of hurricane landfalls, 1900-1972           27         results  in  substantial  physical  and  monetary  losses;
      Area (square miles) of salt-water flooding, Hurricanes        hazards  such as flooding and  hurricane  impact  also
           Carla and Beulah                           3,164         have resulted in the loss of many  lives. In addition,
      Area (square miles) of fresh-water flooding, Hurricane        the areal extent of certain of the hazards,  such as
           Beulah                                     2,187         subsidence  and  active  faulting, is increasing  in size
      Area (square miles) of fresh-water flooding by hurricane      each year. In all cases, more extensive development in
           rainfall (floodplains), northern part of Coastal         the  Coastal  Zone  means  that there will be greater
           Zone only                                  2,073         impact  from  natural  hazards  in the  future  unless
      Area (square miles) below elevation of 20 feet (MSL):         adequate mitigation is undertaken.
           subject to salt-water flooding by tidal surge  5,787
      Number of active or potential hurricane washover                    The most effective and, in some cases, the only
           channels                                     137         mitigation of natural hazards and resulting damage is
      Number of miles of Gulf beach erosion: greater than 10        to avoid certain uses of hazard-prone lands. Mitigation
           feet per year (long term)                     47         by  selected  use requires, however,  that the extent,
      Number of miles of Gulf beach erosion: from 5 to 10 feet      frequency, and impact of natural hazards be known.
           per year (long term)                          50         The  basic goal of this atlas, "Natural Hazards of the
      Number of miles of Gulf beach erosion: from 0 to 5 feet       Texas Coastal Zone," is identification of the principal
           per year (long term)                         104         natural hazards of the Coastal Zone (fig. 1), delinea-
      Number of miles of bay and lagoon shoreline erosion  408      tion of hazard occurrence and distribution, recognition
      Area (square miles) of land subsidence: greater than 5 feet    227  of the natural and man-induced causes of these haz-
      Area (square miles) of land subsidence: from 1 to 5 feet   1,080  ards,  and  evaluation  of measures that  may  lead to
      Area (square miles) of land subsidence: from 0.2 to 1 foot   5,422  mitigation of hazard impact.
      Number of miles of known active surface faults     96
      Number of miles of Gulf shoreline                 367              The Bureau of Economic Geology, The University
      Number of miles of bay-lagoon shoreline          1,100 j      of Texas  at Austin,  has conducted a variety of re-
      Area (square miles) of bays and lagoons          2,075 [      search  programs  in  the  Texas  Coastal  Zone.  The
      Area (square miles) of land in map area         18,000        primary  program  has  been  the  preparation  of an
                                                                  extensive "Environmental Geologic Atlas of the Texas
                                                                  Coastal Zone." The Environmental Geologic Atlas is a

                               TEXAS                                                                      ORINGE

                                                                . HOUSTON                        , AHUR

                                  INDEX       COLORADO    9      sEAUMONT-
                                                      W      .   \      PRT ARTHUR AREA

                                                                                      ' ALVESTON-HOUSTON
                                                                           g \  m         ~~AVREA

                                     ./,CRX-   t    ~~~~~~~\BAY CITY-       I
                                    \_~~~ .' ' 9~ '~ J~ /BY CITY-FRMEEPORT
                              ARE I-  - ad                                  AREA

                                    RONVILL-                     0      0

                                         cto    /~PORT LAVACA
                             X1   \--~ K)H AREAIGEN       A

                           ."CO  H$ FRPU   S  CHRISTI
                         i  ,/I    CHRISTI  am    AREA

                              IONZ.

                                KINGSVILLE
                                  AREA

                   BROWNSVILLE
                              /   AREA                           '                     I
                  hiOALGO \      1             __<-W  0 HARIN GEN ,  Scale in Miles

                                  Figure 1. Index of Natural Hazards Maps of the Texas Coastal Zone.

    series of seven individual atlases designed to provide a      intervals using available, controlled aerial photographs
    comprehensive  inventory  of the  land,  water,  and          and coastal charts, along with surveyed beach profiles,
    natural resources of the Texas Coastal Zone. Further,         the historical rate of change of the Gulf shoreline and
    the 63d Legislature of the State of Texas, through a          related natural features has been determined. Recogni-
    special line appropriation,  directed  the  Bureau  of        tion of the major natural hazards of the Coastal Zone
    Economic Geology to conduct a program involving the           and  consequent  impact was an outgrowth of these
    historical monitoring of the Texas Gulf shoreline. By         investigations of shoreline change, as well as the result
    mapping the shoreline position at selected historical         of mapping and analysis as a part of the "Environ-

                                                          II-2

    mental Geologic Atlas of the Texas Coastal Zone."                 In this atlas, natural hazards are discussed in
    Various natural hazards in the Texas Coastal Zone            terms of distribution and occurrence, processes and
    have been evaluated in a number of reports already           causes, impacts, and mitigation and reduction. This
    published or currently in preparation. This report is        text, as well as the figures and tables, is intended to
    intended primarily to summarize in a general way the         provide a perspective which will enable the reader to
    current knowledge  of the distribution,  nature, and         better understand and interpret the maps of the atlas.
    impact of these natural coastal hazards.                     Inclusion of areas of coastal hazards, except for the
                                                                flood-prone areas of the upper Texas Coastal Zone, is
                                                                based on actual, recent occurrences that have been
          NATURAL HAZARDS AND LAND USE                          observed, monitored,  or measured. The hazards are
                      The  subject of land  use, and  especially any  defined on the basis of data available in 1974; addi-
     Tcnsideration       of land- use m anagement, is complex. In  tional information in the future certainly may permit
    consideration of land-use management, is complex. In
    the case of lands subjected to hazardous coastal pro-        improvement of the accuracy of the maps.
    cesses,  however,  the  application  of any  measures,
                                                                     The seven maps of the atlas (fig. 1) each contain
    whether voluntary  or obligatory, structural or non-       ae lend    as was o h                              convn
                                                                a descriptive legend, as well as other conventional map
    structural, that lead to the reduction and mitigation of     symbols.  The  base  map was    constructed  from  350
                                                                symbols. The base map was constructed from 350
    damage caused by these natural hazards, is beneficial.
                                                                U. S. Geological Survey 7.5-minute quadrangle maps
    Nevertheless, a number of problems are involved in
                   propvermitigti rs, ana umbe offrobemus  a r   by the cartography section of the Bureau of Economic
    proper mitigation. First, an adequate effort must be
                                                                Geology. The scale of the maps is 1:250,000 or 4
    expended  in delineating  hazard-prone  lands and  in
    determining the economic impact of selected use of           miles per inch. Sources of map data, as well as credits,
    determining the economic impact of selected use of
                                                                are listed in the legend of each map and are further
    hazard-prone  lands.  Second,  the economic  incentive       are listed in the  l egend of each map and are further
    for  mitigation is largely  negative;  it is unlike the      documented in the following text. Although this atlas
                                                                is the collective product of the listed writers, each
    positive incentives  for the effective management  of        individual writer assumed  principal responsibility for
    agricultural lands. Finally, the kinds of cost-to-benefit                  preparation of one or more secti ons: Introduction and
                                                                preparation of one or more sections: Introduction and
    ratios involved  for various, specific uses of hazard-       Conclusions-. L.  Fisher  and  L.  F.  Brown,  Jr.;
                                                                Conclusions--W. L. Fisher and L. F. Brown, Jr.;
    prone lands must be determined. In some cases,
    prone  lands  must  be  determined.  In  some  cases,        Hurricanes-J.  H. McGowen; Flooding-L. F. Brown,
    damages  and  losses  sustained  in  utilizing  certain      Jr     .       ; Shoreline Erosion-R.  A.  Morton; Land-Surface
                                                                Jr.; Shoreline Erosion--R. A. Morton; Land-Surface
    hazard-prone lands may be offset by significant eco-
    nomic  gain.  For  example,  the agricultural  use of        Subsidence--W. L. Fisher; and Faulting--C. W. Kreitler.
    nomic gain. For example, the agricultural use of
    floodplains may  result in periodic crop damage and
    loss by flooding, but the overall high yield from these           Information  and data for several of the natural
    fertile lands justifies their continued use. Clearly, a      hazards reported herein are available in more detailed
    different cost-to-benefit ratio exists in the use of         form and on more detailed base maps; these sources
    floodplains  for residential  development.  In another       are cited in this report. In addition, more detailed
    example, the use of ground water in the Coastal Zone         information on shoreline erosion exists on work maps
    results in substantial annual savings over the cost of       on file at the Bureau of Economic Geology.
    transport and treatment of surface water. The with-
    drawal df ground water, however, causes subsidence
                                                                               ACKNOWLEDGMENTS
    and some associated problems which result in property
    damage and land loss. Natural hazards and measures                Many staff members of the Bureau of Economic
    for reduction of losses should be considered logically       Geology contributed to the preparation of this report.
    in the context of both costs and benefits for specific       Cartographic preparation  of the maps was by R. L.
    uses of hazard-prone lands.                                  Dillon, Barbara Hartmann, and D. F. Scranton under
                                                                the direction of J. W. Macon, chief cartographer.
           NATURAL HAZARDS OF THE TEXAS                          Research assistance was  provided  by  the following
                      COASTAL ZONE                              staff members:  M.  Amdurer, J. L. Brewton, C. L.
                                                                Burton, A. C. Funk, M. K. Pieper, and P. M. Walters.
         Natural hazards in the Texas Coastal Zone and
                                                                The manuscript was typed by Sharon E. Polensky and
    immediately adjacent land areas can be classified into       Jamie L. Tillerson. The report was edited by Kelley
    two general categories. Some of these hazards are
                   two  general  categories.  Some  of these  hazards are  Kennedy, Elizabeth T. Moore, Leslie Jones, and Karen
    dynamic, relatively short-term events, such as hurri-        M. White. Camera-ready copy was prepared by Fannie
                                                                M. White. Camera-ready copy was prepared by Fannie
    canes and flooding; the more obvious impacts are
                                                                M. Sellingsloh and Dawn M�. Weiler.
    known,  even  if not always fully respected. Other
    hazards, such as shoreline erosion, land-surface subsi-           The manuscript was reviewed by E. G. Wermund
    dence, arid active surface faulting, are relatively long-    and M. K. Pieper, Bureau of Ecanomic Geology; R. 0.
    term processes; they are commonly less dramatic and,         Kehle,  Department   of  Geological  Sciences,  The
    for the most part, are neither widely recognized nor         University of Texas  at Austin; and J. C. Moseley,
    appreciated.                                                 Executive Director, Texas Coastal and Marine Council.
                                                          II-3

                     * HURRICANES 0
                                                                       Table 2. Beaufort scale of wind force. After Dunn and
                  GENERAL STATEMENT                               Miller (1964).

         Hurricane approach and landfall may drastically                Beaufort No.   MPH    Knots  ClassificatherBuea
    change the shoreline and damage or destroy man-made                                                  Casfcto
    structures. Large, steep waves riding the crest of a
    storm  surge  erode  beaches,  dunes,  and cliffed bay                   0         1      1
    shores  and  destroy  inadequately designed buildings.                    1        1-3    1-3          Light
    The storm surge inundates low-lying areas along Gulf                     2        4-7    4-6
    and mainland shorelines with salt water, and severe
    storm-surge flooding may destroy large areas of natural                  3        8-12   7-10          Gentle
    vegetation and agricultural crops. Fresh-water flooding                  4        13-18   11-16       Moderate
    produced by torrential hurricane rainfall may be par-                    5        19-24   17-21        Fresh
    ticularly destructive along natural drainage systems.
    Hurricane  winds may  damage  or destroy man-made                        6       25-31   22-27 Srn
    structures, with mobile homes particularly vulnerable                    7       32-38   28-33         Srn
    to wind damage. Because of the direct and pervasive
    relationship of hurricanes and many  natural coastal                     8        39-46   34-40 Gl
    hazards, an understanding of hurricanes is important.                    9       47-54   41-47          Gl

        DEVELOPMENT OF TROPICAL CYCLONES                                    10       55-63   48-55 WoeGl
                                                                            11      64-73   56-63       WoeGl
         A hurricane is a storm of tropical origin with a
    cyclonic  wind  circulation  of 74 miles per hour or                    12       74 or   64 or        Hurricane
    higher (Dunn and Miller, 1964). The cyclonic atmo-                                >74    > 64
    spheric system is characterized by decreasing baro-
    metric pressure toward the center and by surface
    winds. In the northern hemisphere, these surface winds
    spiral counterclockwise upward, lifting the air and
    eventually producing clouds and precipitation.                 strike  the  Texas  Coast  occur  most  frequently  in
                                                                   August and September (fig. 3). The mean storm track
         The hurricane is the devastating end member of           and  the  area of most frequent origin change from
    the tropical cyclone class of storms. The classification       month to month during the hurricane season. Storms
    that is commonly used in the Atlantic region (table 2)         spawned  at a particular time and place have a pre-
    is as follows: (1) tropical disturbance-rotary circula-        ferred landfall area (Dunn and Miller, 1964). The most
    tion slight or absent on the surface; no closed isobars        frequent landfall area for storms that develop in the
    (contours of equal pressure) or strong winds; common           northwestern Caribbean or the Gulf of Mexico in June
    throughout the tropics; (2) tropical depression-one or         is the Texas Coast. The Texas Coast is rarely struck by
    more  closed  isobars;  wind  equal  to  or  less than         hurricanes after the middle of September.
    Beaufort 7; (3) tropical storm-closed isobars; wind
    greater than Beaufort 7 but less than 12; and (4)
    hurricane-wind force of Beaufort 12, or 74 mph or
    greater.20 0lO   0   0900 30 0 000 0

         The  precise  details of physical  processes  that                       >
    produce  hurricanes  are not  well  understood.  It is          I                        j(     j70
    known, nevertheless, that the mechanism producing
    hurricanes must supply (1) low-level atmfospheric con--
    vergence of sufficient strength to lift the moist layer;                           > ~~J
    (2) high-level atmospheric divergence to remove accu-          o      -
    mulated air and yield a pressure drop at the surface;                             --
    and   (3)  energy  to  maintain  the  atmospherict-                                                     tj
    circulation.V1-                                                                                              t

         Conditions favorable for tropical cyclone develop-
    ment exist in the North Atlantic Ocean, the Caribbean            Figure 2. Areas of tropical cyclone development. After Dunn
    Sea,  and  the  Gulf  of Mexico  from  June  through           and Miller (1964).
    October (fig. 2). Tropical storms and hurricanes that

                                                              11-4

                                                                 hurricane vortex. The Intertropical Convergence Zone
     200-                                                        is the area where winds from the North and South
                                                                 Atlantic converge. When the ICZ moves north or south
     190-                                                        of the equator, the Earth's rotation imparts a spin to
    W)180-    TROPICAL CYCLONES                                   converging  currents,  thereby developing tropical cy-
    a, clones. In the North Atlantic this occurs near Cape
    .170-    HURRICANES                   '                       Verde. A  polar trough is a low-pressure zone which
                                OD0_    I                        migrates  from  west  to  east  within  the  prevailing
    -160-    HURRICANES THAT                                      westerles.  The  westerlies  lie north of the Azores-
              STRUCK THE TEXAS
    50U- TCOAST                            /                      Bermuda High. When the polar trough is very strong
                                       _150t-  /  \              or when the Azores-Bermuda High is weak, the trough
      40-                                                         may penetrate the tropics. Its influence on the devel-
     130 -                                                        opment of tropical cyclones is greatest either early or
             ~130 ~- |~~ tlate in the hurricane season.

     120-              -
    "l                                    /   I
        0-                               /                               100o      80      600      400      20�      0o

    0100-                                   '                                                             I

    <50                                                                     -
                                    IL

     40-                                                            10
                     zo~ 38~0-  r    I                                         t\k   I  ,a0�  4  81~~~~~� L;'?  61� ~~~~' B o 400  20
     720-                                                           Figure 4. Mean position of the Azores-Bermuda High during

       z0 -                                                       Dunnand Miller (1964).
                          m/ .10 00                                                                               1 /"X

                     MONTHS OF THE YEAR
                                                                      A hurricane runs on heat. Its formation and
      Figure 3. Frequency of Atlantic tropical       es and       maintenance  depend  upon en         -Bermuda High dring
    hurricanes and the number of hurricanes that struck the Texasr
    Coast between 1887 and 1958. Data from  Dunn and Miller       ocean  surface. Hurricanes  form  over comparatively
    (1964).                                                       warm  water with a temperature  above 79�F. Warm
                                                                 moist air moves  across the ocean  surface spiraling
                                                                 inward into the hurricane circulation. As it rises to
    hurricanes and the number of hurricanes that struck the Texas

         Atmospheric conditions or elements that directly         higher elevations, it expands under reduced pressure.
    or indirectly contribute to the formation of tropical         When  the air becomes saturated, moisture condenses
    cyclones are (1) the Azores-Bermuda High, (2) easterly
    waves, (3) the Intertropical Convergence Zone, and (4)        and  releases  heat  to  the  surrounding  atmosphere.
    polar troughs. The Azores-Bermuda High is a large             Energy is partly dissipated in the upper anticyclonic
    anticyclone extending from the Iberian Peninsula to           flow by surface and internal friction.
    the southeastern United States (fig. 4). It is the
    dominant atmospheric system for the Atlantic during
    summer and early fall when the High oscillates from                  CHARACTERISTICS OF HURRICANES
    north to south (Dunn and Miller, 1964). Persistent
    departures  from  normal  position  have a significant             The principal features of a hurricane are (1) the
    effect on hurricane frequency and paths. The easterly         eye, surrounded by convective clouds; (2) low-level
    wave is a low-pressure trough which is imbedded in            cyclonic winds; (3) upper level anticyclonic winds; and
    the easterly current lying south of the Azores-Bermuda        (4) a vertical circulation system in which air flows into
    High. A stable wave may move from east to west as             the eye at low  levels, flowing  upward  within the
    much as 3,000 miles without any change. Deviation             convective clouds, outward in the upper levels, and
    from the norm indicates that the wave is developing a         downward in the outer parts of the storm (fig. 5).
                                                           TT-5

                                                                                     Table 3. Hurricane classification. After Dunn and Miller
                                                         Y  -----  _50,000    (1964).
               '~~~~ ~~~~~~~~-- ~ ---------------

                                                                  opooo
                  .... . ' ,     -        -, -4 ....'-'-=     -- .0,000
                                                                      20,000 EClassification       Maximum winds    Minimum central pressure
                                                                  ;----20,000 ~Classification
                                                                                                         (mph)               (inches Hg)
                                                                  iO.000
                                                            ' (i)                     Minor          Less than 74         More than 29.40
           LEFT SIDE                    RIGHT SIDE

      Pr,-ory Energy Cell ( Hol Towers")  Coneecfive Clouds M Allootrls  Corrus     Minimal          74 to 100           29.03 to 29.40

       Figure 5. Hurricane model. The primary energy cell (convective
    chimney) is located in the area enclosed by the broken line. After               Major           101 to 135          28.01 to 29.00
    Carr (1967).

                                                                                      Extreme        136 and higher         28.00 or less

          The eye of the hurricane is a low-pressure area
    where wind velocities are only 10 to 20 mph. The eye
    may  be relatively small, only 4 miles in diameter, or                          Table 4. The nature of hurricanes striking the Texas Coast
    large, up to 25 miles in diameter. Average diameter is                   between 1900 and 1972. Dash indicates that data are unavailable.
    about 14 miles (Dunn and Miller, 1964).                                   Data from National Oceanic and Atmospheric Administration-
                                                                               National Hurricane Center (1900-1974). Note that data do not
                                                                               necessarily agree with that provided by U. S. Army Corps of
          Air  flows  from  high-pressure  areas  toward  the                Engineers (1962, 1968, 1971a).
    low-pressure storm center. The pressure differential
    results primarily from temperature differences.
    Strongest  hurricane  winds are near the storm  center   ....                                     r    ..         [.. ..
    because  this  is  the  area  with  the  steepest  pressure               .. No, .. 2.5 -o   270                    Or       50 000   6
                                                                                                    6a~~~~~~~~~~~~~~~~~~'Leon '
    gradient  (fig.  6).  Lower  level winds  have  sustained                     9.............
    velocities ranging from 74 to 200 mph; the velocity of                     [ III.. Coor.                                                ..
                                                                                    1510   Son,  70  lI  120  N  -p             ~ ~    a
    gusts  may  exceed  sustained winds  by  30  to 50  per-                      rrd
    cent.  Winds  are  stronger  on  the  right  side  of  the               N`..    . .10-    -. 00              .      ...
    hurricane  eye  (fig. 5) because the forward  motion of                ..........
                                                                                    O975      1 70  -7 orpo  b.ro  000G 6 S IC6~r  500000    rrr 21
    the storm is added to the rotational wind velocities.                      oI ]19o    Por                              o
                                                                                    0016   App 70   II mph6  730m~ -o 000 00'   Oor2 o Oolt~d~  07 00 0000  00
                                                                                  Nolrornd  PaOolodtre s oIn

                                  I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ol;~� l( .....
                                                                                    7070    Sop' 70  73 nor  700 oor  0799  70 Coo,- 2000 ro 000  ,

                                                                                  Noo1'oI-  0 0,0d 000
                  120 I

                                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I  Ip I      1 0    21 ll   5 Ir I SSoOno lal
          20 ...                                                                       .     ....... rr......r,      I
                                                                                    7002     00        h    0 1p0  Oro 61  2lon S, 5000000   00
                  lit 0                                                                   ,,19233  5ep     t 4-6  linpr  OOmph  0000  1 r,,.  012000000  40

                         ~~~~~~~~~~~CON                                         No1  name 35rawnswfico
                  ?0                                                                      6g 0mp0 0- 0p 08 8 " 2 la 1        aI   SI 500r00OpS
       80-   Al                    ESTHER                                        oo      or                             0 o
                             -  /   'P  \oo'\                                     7007~~~~~~~~~~~~~~~~~~~~~~14  sopt 03  1 3 mo  90-p  0007 2  3 1   '00  5  agn  6000 000  4

                       Rn~i 'L DOSTNC     NP IAL ...........
    UJ               N.                                                         Nrd         O

                          Figure 6, Wind profiles in Hurricanes Donna, 1960, Esther, ~ ~t ..~d  ~a Do~a 6.
                                                N~~~~~~~~~~~~                             ~~~~~~~~~~~~~ DONNA  754  4o  ~000  - ~   2 r78 ' 090  P 0,otliohoo  -l   5~000000

    UJl                                                                         ao An,  PS. ~, opn . 0,66a,
                                     u3  !  /   "~' ANNA             194S I
                          U )  .:N$ ~~~~~~~~~~~~~~~~~~~~~~~.S ~~~~~~O27                            Omh   10 p    2851 IS~olaa      20?133,000  3
       4 0 -4                                              -l. ....... ..,o~ Ia
    o G O 1    I 1'N                                  1900                               Aug 0~30  0~,r j4  770 ob  3070   Sabine Pa~  S20. 0 I000 I

                                                                                    9194    Oc  3   1 3ml  135 mb 28   I  10 Fre-ot  S6.o 1Ono0S
       20 1959                                                                           5oocoo
                                                                                                .,0.~~~~~~~~~~, 9 1 no   l 1r 00r9   Opool oIh   Slhrro'COOO-

                                                                                                     4 00         29 07   2 N8o' 000y00700  $oO

                                                                                    196o   Sep0    [    -  P3noh  [ 750" 'ooo L     5300,000    ,3
                        2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Cn 50700r    0'�o0n0,
                                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~70                          00       70or  I0  Io  I    000  I  Ira000,  6100303
                                                                                       9070000,~h 0p ro94o1    -          2Hg114i  1 700 9117700 3

                  20 40 60                8 -                                        OO 120        Oro. 00704.6   0201 ...6o.      . ....ooooo 0....
                   RADIAL  DISTANCE  (NAUTICAL  MILES)                           730 20                           80   0 I-         000 I0

       Figure 6. Wind profiles in Hurricanes Donna, 1960, Esther,                [s7,                     r      0                 000000
    1961, and Anna, 1961. After Col6n (1966).

                                                                       11-6

         Hurricane size is commonly expressed in terms of                                 Waves
    diameter of hurricane and gale winds or by diameter
    of the  outer  closed  isobar.  Average  diameters of             Principal  damage  to  man-made  structures and
    hurricane and gale winds are about 100 and 400 miles,        severe erosion of shorelines are produced by storm
    respectively.  There  is a wide  range  in the size of       waves superimposed on the storm surge. The power
    hurricanes. The Great Atlantic Hurricane of 1944 had         generated by a breaking wave can be visualized by
    hurricane winds with a diameter of 600 miles (Dunn           considering that a cubic yard of water weighs about
    and  Miller, 1964). Hurricane  Carla, in 1961, had            1,500 pounds and that waves may  be moving at a
    hurricane-force winds with a diameter of about 300           velocity of about 70 to 80 feet per second. Breaking
    miles (Colon, 1966; Hayes, 1967), and in 1970, Celia's       waves  alone  can  destroy many  buildings, but their
    hurricane wind diameter was about 80 miles.                  destructive potential is significantly increased by tree
                                                               trunks, pilings, and other debris that act as battering
         Hurricane  size and  intensity  are  not directly       rams. Appropriately designed structures, nevertheless,
    related. The most intense hurricanes are not neces-           can withstand flooding associated with the forerunner
    sarily the largest; for example, the diameter of cy-          and storm surge.
    clonic circulation tends to increase during the decaying
    stage (Colo'n, 1966). Low  barometric  pressure  and              The shoreline may  retreat several hundred feet
    relatively high wind velocity are common to all trop-        during a few hours when under attack by storm waves
    ical disturbances (table 3), and these parameters are         (Shepard,  1973;  McGowen  and  Brewton,  1975).
    more  suitable for classifying hurricanes  (Dunn and         Between hurricanes, accretion may  restore much  of
    Miller, 1964).                                               the shoreline lost during the storm.
                                                                    Maximum surge height is commonly associated
         Average fife of a hurricane, determined by time         with a storm which has a track perpendicular to the
    and place of origin and rate of forward movement, is         shoreline. It is also greatest along coasts, such as the
    about nine days. Most hurricanes move forward at a           Texas Gulf Coast, that are concave and adjacent to
    rate of about 12 mph. The forward speed of hurri-            wide, gently sloping shelves. If the hurricane landfall
    canes that have struck the Texas Coast in August and         coincides with the astronomical high tide, surge height
    September has averaged 8 to 12 mph. Hurricanes that          will be even greater.
    struck  the  Texas  Coast  between  1900  and  1972               The rare "hurricane wave" or seiche has caused
    exhibit a wide variety of characteristics (table 4).         some of the world's greatest natural disasters (Dunn
                                                               and Miller, 1964). It may result from resonance that
                                                               produces a huge wave, or it may be a rapidly rising
                RELATED STORM EFFECTS                            and abnormally high storm surge. The hurricane that
                                                               struck Galveston on 8 September 1900 may have been
         Hurricanes produce striking changes in the sea;         accompanied  by such a hurricane wave.  During the
    huge waves and storm tides are generated. Hurricanes         Galveston storm, water level rose steadily from 3:00
    also trigger heavy rainfall, create high-velocity winds,     to 7:30 p.m., at which time there was an abrupt rise,
    and spawn tornadoes.  As the storm approaches and            of about 4 feet in as many seconds (Dunn and Miller,
    makes  landfall,  each  of these  related  phenomena         1964).
    becomes increasingly more important because hurri-
    canes  have  the potential to alter the shoreline by              Development of Washover (Breach) Channels
    erosion or deposition, to flood low-lying areas, and to
    damage or destroy man-made structures.                            One of the principal effects of the storm surge is
                                                               the development of washover channels that breach
                   Changes in Water Level                       barrier islands or peninsulas. These channels readily
                                                               develop at the sites of eolian erosion (blowouts) or in
         A  slow rise in water level occurs when oceanic         areas with poorly developed  fore-island dune ridges
    swells  generated  by a distant storm  approach  the         and beach ridges. Tidal waters flow landward through
    coast. This rise in water level is known as the fore-        the channels, scouring sand and depositing the sedi-
    runner. A rise in water level of 3 to 4 feet, produced       ment  in washover fans within the adjacent bay or
    by the forerunner, can affect several hundred miles of       lagoon.  Following  passage  of  the  hurricane,  the
    coast (Dunn and Miller, 1964). Storm surge, on the           channels serve to return the elevated waters of the
    other hand, is a rapid rise in water level generated by      bays and lagoons to the open Gulf. The surge channels
    onshore  hurricane  winds and  decreasing barometric         are active only during the brief period of hurricane
    pressure. Maximum storm surge generally occurs 10 to         approach,  landfall, and immediate aftermath; storms
    20 miles to the right of the storm track, but it may         tend to reactivate the same wash-over channels. Marine
    occur  to the left of the storm if counterclockwise          shoreline  processes  close the gulfward  end  of the
    north winds stack water against an obstruction, such         channel within a few days. Water may stand in the
    as the back side of a barrier island.                        abandoned channel for months following the storm.

                                                         11- 7

         In  general, the density  of washover channels                             Storm Approach
    increases southwestward along the Texas Coast. This
    regional increase in channels results principally from            Storm  approach  (fig. 7B) is marked by rising
    the southwestward decrease in vegetational stability of      tides (forerunners) and increased wind velocities. When
    barrier islands and fore-island dunes. A total of 137        the  storm  strikes the coast, the storm surge and
    washover channel sites have been recognized and are          associated  waves  erode  the  normal  beach  and
                                                               asociaed waes eofr  roade lt he nrmcal beach an
    shown on the Natural Hazards Maps. The location of          foredunes to  form  a broad, flat hurricane beach.
    these sites is based on interpretation of aerial photo-      Storm-surge flooding often scours washover channels
                        low-level aerial reconnaissance, and field work  across barrier islands and peninsulas. Sediment is trans-
    graphs, low-level aerial reconnaissance, and field work
                   undertakenaspartoth "Envionmeported through the storm channels and is deposited on
    undertaken as part of the "Environmental Geologic
    Atlas            of  the Texas Coastal Zon e." Construction within  barrier flats and along bay margins as washover fans.
    Atlas of the Texas Coastal Zone." Construction within       Miln   hrlnsrciemdysdmn   hti
                                                               Mainland shorelines receive muddy sediment that is
    or immediately adjacent to hurricane breach or surge         deive  fm th a                          i
                                                               derived from the bay bottom and carried ashore by
    channels may lead to property damage in the event of   rie  foosStom-re d   are                                   y
    a hurricane landfall.                                       storm-surge  floods. Storm-surge tides are commonly
                                                               higher in the bays than on the Gulf beaches, although
                           Rainfall                             the flooding and the effects of the accompanying
                                                               waves are pronounced in both areas.
         Some of the greatest rainfalls recorded in Texas
    have resulted from hurricanes. Upon striking a land-                                Landfall
    mass and moving inland, the forward movement of a
    hurricane is reduced, and the rate of rainfall increases.        At landfall (fig. 7C), when the storm passes over
    Maximum  rainfall occurs in front of and along the           the shoreline, the direction of current movement and
    right side of slowly moving tropical storms. Rainfall is    wave approach shifts into compliance with the change
    equally distributed in the front and rear halves of         in wind direction. Highest intensity winds are felt as
    storms whose forward motion has stalled.                    the storm comes ashore. On the left side of the storm,
                                                               water and sediment are moved from the bays back
                            Wind                               into the Gulf through inlets and breaches in the island,
                                                               while water and sediment are still being pushed into
         Hurricane winds rank third behind waves and
                                                               the bays on the right side. Waves strike the Gulf
    rainfall flooding in destructive potential. Width of the     h      e a     o            the       side    the
                                                               shoreline at a low angle as the back side of the storm
    area of destructive winds may range from about 14 to
                   area of cile s (Duny  andlefr,     194Wd     v itisof  passes, creating currents that transport sediment north-
    300 miles (Dunn and Miller, 1964). Wind velocities of
                                                               eastward alongshore in the same manner that the
    100  to 135 mph  are common.  Severe storms have
                   velocities of  135  to160mph;front-edge winds and currents had moved materials
    velocities of 135 to 160  mph; the most violent    toward the southwest.
                                                               toward the southwest.
    hurricanes have wind velocities of 200 mph or greater.
    Damage  to structures results from  sudden pressure                                                            A
    changes associated with gusts. Damage begins when
    pressure reaches approximately 15 to 20 pounds per
    square foot (wind velocity of about 60 mph).

         The highest velocity winds associated with hurri-
    canes are contained in tornadoes having estimated
    velocities of 400 to 500 mph. Tornadoes may occur at
    any time during and immediately following hurricane
    passage; their most  frequent occurrence is in the .......
    forward half of the storm.

           GENERALIZED HURRICANE MODEL                                PHYSICAL FRAMEWORK, TEXAS COAST

         Historical records indicate that successive hurri-  ..
    canes may differ markedly (table 4). One hurricane            ~         .......... bo
    may  generate a large storm surge, another may  be             <    ...
    characterized by torrential rainfall, while exceptionally
    high wind velocities may define a third type. From
    these records and from previous studies, a general
    hurricane model (fig. 7) was developed (Price, 1956;
    Hayes,  1967;  McGowen  and  others,  1970).  The
    following is a description of a model hurricane as it
    approaches the Texas Coast,. makes landfall, and moves
                        ~~~~~~~~~inland.                         /~ ~HURRICANE APP                        H

                                                         ITT-

                                                                               TYPES OF HURRICANES

                                                                     During the past 70 years, most coastal areas in
           z/                                        _ = ~- .    Texas have experienced severe weather resulting from
                                                                direct impact or nearby passage of a hurricane. No
                                                                area, however, has experienced each of the hurricane
                             ,~  ~:   <   =t_;:'  < I   *types which can strike during the hurricane season.
                                                                 Using meteorological and hurricane data accumulated
                                                                over the past several decades, it is possible to rec-
                                         .=    . C..- �so~   ......... cC (x  ognize at least three general kinds of hurricanes and to
                                                                 predict their impact on different parts of the Texas
                                                                Coast (table 4). Predictability of hurricane effects is
                                                                based on  (1) bay-estuary shape, (2) Gulf shoreline
                                                                 configuration, (3) track of the hurricane relative to the
                    HURRICANE LANDFALL                           coastline, (4) nature and distribution of physical and
                                                                 biological environments, and  (5) population density.
                                                      D         Three  recent,  well-documented   hurricanes,  Carla,
                                                                Beulah, and Celia, illustrate the nature of hurricane
                                                                 variations (table 5; fig. 8). The reader should be aware
                                               //~  ~ ~__~DD    that observations such as storm-surge elevation, hurri-
                                                                 cane wind  velocity, and  pressure values, may  vary
                                                                 among observers. For this reason, the sources of the
                                                                 data are noted in this atlas; any inconsistencies in
                                                                 wind velocity or storm surge, for example, result from
                                                                 the use of several data sources.
                                          d  T n ~A;]orI' nnl................... Hurricane Carla
                                                                      Hurricane  Carla  was  spawned  in  the western
                  HURRICANE AFTERMATH                            Caribbean on or about 3 September 1961. She became
                                                                 a hurricane on 5 September and moved into the Gulf
      Figure 7. Schematic model of hurricane effects on the Texas  of Mexico between Cuba and the Yucatan Peninsula
    coastline. (A) Physical features characterizing the Texas Coast,  on 7 September (Hayes, 1967). Carla moved toward
    (B) Effect of approaching hurricanes, (C) Effect of hurricanes  the Texas Coast at about 9 mph, making landfall (fig.
    upon impact with coast, (D) Aftermath effects of hurricanes.  8) near Port O'Connor on 11 September (Port Lavaca
    After McGowen and others (1970).                              map).  Her travel time over the warm waters of the
                                                                 Caribbean and Gulf of Mexico was about nine days.
                     Hurricane Aftermath                         Maximum sustained winds at landfall were about 175
                                                                 mph, and pressure in the eye was about 931 millibars
         Hurricane aftermath (fig. 7D) is the period
    following passage of the storm inland from the coastal             Table 5. The characteristics of basic types of hurricanes
    area. As the storm moves inland, it becomes weaker            striking the Texas Coastal Zone. After McGowen and others
    and more diffuse, and commonly spawns numerous                (1970).
    tornadoes. Excessive water in the bays drains gulfward
    through storm breach channels and passes, depositing           Variables   Beeuah type  Carl type      Cea type
    sediment within the channels and in the nearshore
                                                                  Wind      Moderote       Moderate       High
    Gulf. Heavy rains that commonly accompany hurri-
                                                                  Storm-surge
    canes produce runoff of flood proportion, inundating           Stormsure   Moderate      Hgh            Low
    low-lying areas along stream courses and bay margins.          Rainfall    High         Moderate        Low
    The influence of strong winds and heavy rains may
    accompany   the  storm  inland  for  considerable               destructive  Medium     Large          Small
                                                                   destructive  Medium     Large          Small
    distances.                                                      core
                                                                  Length of
         Longshore currents begin to build bars that even-         aftermath    Extended    Intermediate   Brief
    tually close off the mouths of hurricane channels, and         effects
    waves  begin  to  restore  the  normal  beach  profile.        Character of  Port Mansfield:    Port O'Connor:    Port Aransas:
    Hurricane deposits are reworked by subsequent rains             coastline    poorly vegetated,   well vegetated,  moderate vegetation,
    and wind. Some of the sand that is exposed in breach            affected    low relief, broad   local relief to  local relief to 30 feet,
    channels is blown landward onto the barrier flal, and                     unrestricted bay    30 feet,  funnel-like
                                                                                            funnel-like   Nueces Bay
    washover fans are reworked by bay and lagoon waves                                       Lavaca Bay
    and currents.

                                                          II-9

                 .,,s.  \,,,4CAL ....................WsSTR / ILA \ EA
                                                                                                  s 'SEAUM

                        75

                                    8RA ~~~~S.F  Nfl l NS S25                                            SCA AjILE  <IN M ILES
                      IT                                                 8 <'  r -  '                       -
             I_1k  , 'O t   t    \

                                4/TW;-wt                                            z    1~~~~~~~~~~~~~~~~~~~~~~~~~~75MP
                        '   CA           RLA5 CELLA

                                  WNSV LLE                                               NSVILLE
             -.2' '- .        --~.~..~ '-4'.RRNS    A           T     ORNADOES

           i    The trc , f t  es                 . -i'vA  an Ce   a  the area covere  by     YTGt   Nwn          s
                                                   ICANE IN DS                  END T RNA
              i- ~S~p~                -     C .~,:i~~"i"(

                 , 7     r s::                      SCmE N~ MIS,)AES                     25SAEIsMS

                   A,(FAR,  �~i' 175 MPH

                                                                        !.. t [..�.rI.,TORNADOES

                                  NNVILLE

      Figure 8. The track of the eyes of Hurricanes Carta, Beulah, and Celia, and the area covered by hurricane-level winds, Texas Coastal
    Zone. Based on data from Cooperman and Sumner (1961), Orton and Condon (1970), Orton (1970), and U. S. Army Corps of Engineers
    (1968). After Texas Coastal and Marine Council (1974).

    (mb). The Galveston weather station was under effects               Carla's track across the  Gulf of Mexico  was
    of  gale-force  winds  for  49  hours  (Colo'n, 1966).         northwestward. After landfall, her course curved to
    Corpus Christi, only 50 to 60 miles from the storm             the northeast, and she crossed the United States and
    center, experienced peak gusts of 85 mph and pressure          entered Canada in the Great Lakes area.
    of 977 mb. Hurricane wind diameter was approx-
    imately  300 miles (fig. 8). Carla was probably the                               Hurricane Beulah
    largest Atlantic hurricane for which there are reliable
    data (Colon, 1966).                                                 Hurricane Beulah was spawned in the Atlantic,
                                                               becoming a hurricane on 7 September 1967 (Scott and
        Carla was characterized by extensive storm-surge         others, 1969). She moved west-northwestward into the
    flooding (fig. 9) and severe shoreline erosion. Surge          Caribbean, lost considerable energy in the mountains
    height in the Port O'Connor area was in excess of 10           of Haiti, re-formed and assumed  a more  westerly
    feet above mean sea level (MSL), and at Port Lavaca,           course crossing the Yucatan  Peninsula on  17 Sep-
    the surge reached a maximum of 22 feet above MSL    tember. She  made  landfall (fig. 8) in Mexico, just
    (U.  S. Army  Corps of Engineers,  1962). Parts of             south of Brownsville, on 20 September (Brownsville-
    Matagorda Peninsula were breached by storm channels,           Harlingen map). After becoming a hurricane, her travel
    anedshorelines  were  eroded  as much  as 800  feet            time over the Caribbean Sea and Gulf of Mexico was
    (She pard         n     Be, 1973; McGowen and Brewton, 1975). Dunes  13 days. Maximum wind velocity at landfall was 125
    on Mustang Island were eroded landward as much as              to  160  mph.  In Texas,  winds of hurricane force
    150 feet (Hayes, 1967).                                        extended from the     Rio Grande northward      approx-

                                                               the eye decreased in size by about 40 percent, and
                                                               wind velocity  increased from  90  to 130 mph  with
      20-"                                                        gusts  of  160  to  180  mph.  The  width  of Celia's
                     /iX S BAY                                   destructive path was about 15 miles, and her hurricane
                                         Om=OPEN GULF           winds  had  a diameter  of about  80 miles (fig. 8).
                w  /  ~   ~x                                     Celia's inland  path  was  west-northwest to Del Rio
              -'    /  IXx                                      where  her  progress  became  irregular.  The  storm
                                  X
                         I   RIGHT  SIDE                        expired in the mountains near Chihuahua, Mexico.
                         0
       a: - /
                       x XX
    0 1o-/                                                             Celia was  accompanied  by  high-velocity  winds
                0           XOO0                                and a few tornadoes. Rainfall was minimal and storm
           LEFT SIDE  0                                          surge was restricted to a very narrow zone. Maximum
    :D                                                x
                  /  I                                           surge (determined from debris lines and, therefore, not
           X ~ ~ ~
                     < )p                                       indicative of stillwater level) was about 9 feet along
                                                     X         the Gulf shore near the Aransas Pass jetties, 12 to 14
                                                *- 0
                                                               feet along the bay shore at Aransas Pass, and up to 9
       0                       I/ ~27 i i feet at Corpus Christi. Surge height in the North Pass
       PORT ISABEL   EYE   GALVESTON          MISSISSIPPI RIVER   and Corpus Christi Pass areas was Qnly 4 feet. Hurri-
                    oF
                 HURRICANE                                        cane Celia was characterized by her destructive winds;
                                                               storm-surge  flooding  and  rainfall  were  relatively
         SW                COASTLINE                 > NE         insignificant.
      Figure  9. Maximum  storm  surge that occurred during
    Hurricane Carla, 1961, at 14 bay and 10 open Gulf localities          FACTORS INFLUENCING SEVERITY
    along the northwest Gulf of Mexico. Note that the right side of             OF HURRICANE IMPACT
    Carla generated greater storm surge than the left side of the
    storm. Based on tide data collected by the U. S. Army Corps of
    Engineers, Galveston and New Orleans Districts, and presented by   The severity of hurricanes can be expressed in
    Cooperman and Sumner (1961) and Harris (1963). After Hayes    various terms, such as damage to man-made structures,
    (1967).                                                       monetary losses, and loss of human life. The nature of
                                                               the storm, population density, and shoreline charac-
                                                               teristics determine the number of lives lost, the extent
    imately 250 miles (fig. 8). Storm surge was about 10
    *  feet above MSL at Brazos Santiago, and tides were 6        of shoreline erosion, and damage to or destruction of
    to 7 feet between Port Mansfield and Port Aransas and         man-made structures. The nature of the storm dictates
    5 feet near Cedar Bayou (Behrens, 1969; Scott and             whether storm surge, fresh-water flooding, or wind will
    others, 1969).                                                be  the dominant  destructive  element.  The  loss of
                                                               human life and the amount of property damage is
         After  making  landfall,  Beulah  traveled  north-       directly  affected  by  population  density.  Shoreline
    northwestward inland into Duval County, changed her           characteristics will either amplify or diminish some of
    course to the southwest, and moved back into Mexico.          the hurricane processes.
    The long path overland slowed the storm, resulting in
    heavy  rainfall and  the generation  of at least 115
    tornadoes (fig. 8). Beulah was characterized by excep-
    tionally heavy rainfall; in some areas, rainfall was in             hree  destructive  potential,
                   exces  of  0 inhes  urin  the  our  r fie das of hurricanes. In order of decreasing destructive potential,
    excess of 30 inches during the four or five days of   te eae()somsreadatnatbekn
                   aftermath storms,                            ~~~~these  are  (1) storm  surge  and  attendant  breaking
                                                               waves,  (2)  fresh-water  flooding,  and  (3) wind.
                                                               Assuming a common point of landfall, Carla-type
                       Hurricane Celia                          hurricanes have the greatest destructive potential of
                                                               the three basic hurricane types, Beulah-type storms
         Hurricane  Celia was spawned  in the Caribbean          rank second, and Celia-type storms are the least de-
    Sea near Cuba. A tropical squall struck the western           structive. A Celia-type storm, nevertheless, can become
    part of Cuba on 31 July 1970. On the morning of i highly destructive when it strikes a highly developed
    August, the disturbance became a tropical storm, and          area (table 4).
    on the afternoon of 1 August, Celia became a hurri-
    cane (McGowen and others, 1970). Celia's course was                Large,  intense  hurricanes,  which  create  high
    west-northwest toward the Texas Coast, and her rate           storm-surge flooding with attendant wave erosion, can
    of forward movement was 10 to 15 mph. She made                be expected when  a storm moves slowly across the
    landfall at Port Aransas on 3 August (Corpus Christi          ocean without being impeded by landmasses en route
    map); her travel time over the Gulf of Mexico was             to the Texas shoreline (Carla-type hurricane). The path
    only three days. At about the time she made landfall,         that a hurricane takes after making landfall, the rate

                                                          II-ll

    of forward movement, and the topography of the
    landmass over which it moves have an effect on
    rainfall rate, which dictates the magnitude of fresh-                  E  AM
    water  flooding. A  long route over the ocean by a                                 SALT
    slowly moving storm significantly increases the mois-A
    ture content of the storm clouds. Slow forward move-
    ment overland, coupled with considerable topographic
    relief, is conducive to high rainfall rates (Beulah-type                         VEGETATED FLATMAS
    hurricane). A hurricane that is spawned in the Gulf of                      ;BAR                  A
    Mexico and travels rapidly across the open Gulf willB
    most  likely be accompanied by high-velocity wind,            SHOREFACE        FOREISLAND DUNES
    minimal  rainfall,  and  minimal  storm  surge.  These BC
    storms  are  generally  small, but intense  (Celia-type                  BESEACHED FLAT  DUNESI
    hurricane).

                   Shoreline Characteristics                     SHOREFACE
                                                                 Figure 10. Generalized profiles of types of Texas Gulf Coast
         The  Texas  Coast  is characterized by an outer         shorelines. (A) Headlands, (B) Peninsulas, (C) Barrier islands.
    Gulf shoreline and an inner bay shoreline (fig. 7A).
    Gulf shorelines exhibit -three principal morphological            Peninsulas, which resemble offshore islands, are
    types:  (1) deltaic headlands, (2) peninsulas, and (3)       elongate strips of sand and shell that are attached to
    barrier islands. Bay  shores consist of a variety of         headlands and extend in the direction of longshore
    shoreline types; among these are (1) relatively high         drift. Three peninsulas on the Texas Coast are Bolivar
    cliffs, (2) low-lying marshes, (3) bayhead deltas and        Peninsula,  Matagorda  Peninsula,  and  south  Padre
    river valleys, and (4) areally restricted sand and shell     Island.  A  generalized  profile across a peninsula  is
    beaches. The shoreline type determines, in many in-          illustrated in figure 10.
    stances, the extent of storm-surge flooding and wave
    erosion.                                                          Bolivar  Peninsula  (Galveston-Houston  map)  is
                       Deltic hadlads ocurbetwen SbinePassandabout 23 miles long, is densely vegetated, and consists
       BoiaDensltaic h   letIsandlands Bocubewen CaiedPass Cut,  chiefly of fine-grained  sand.  It is characterized by
    Boiand thenRinuaFot Islande and BraoswSntig Peass CThe  well-developed ridge-and-swale topography, and there
    twasendos theRoGandelands (BeaumosSnti-Por PAss.thuran is no evidence of recent storm erosion or breaching of
    Bay eastyreprnot heaplns) areaumontPrprholgcal siiar.        Boilvar Peninsula by storm washover channels. Max-
    BaysCity-Freeportubdivisionsmorphhesgicwolheadmilar          imum  elevation along  the  seaward  edge of Bolivar
    Pyincludehic  surbdivi   2)ersional oftescapentwo  hedands   Peninsula is about 10 feet above MSL. Several storm-
    (3) shell apron or ramp (fig. 10). A shell ramp, which   surgetatioon hasvprevented the peiscuring but chanselan
    is about 5 to 7 feet above MSL, is commonly backed           dvegeltonhspreenteof ative wscoverin ofcannes.an
    by  marshes  with  attendant  lakes and  tidal creeks.  d vlpeto  ciewsoe as
    These low-relief shoreline features are readily breached          Matagorda Peninsula (Bay City-Freeport map) is
    by storm surge and adjacent marshes are commonly             about 51 miles long. The eastemnmost three miles of
    flooded.  With the exception of part of the Modern           the peninsula is separated from the western segment
     Brazos delta, the Texas coastal headlands erode rapidly      by  Brown  Cedar  Cut,  a  tidal  pass created by  a
     under  normal  sea conditions  and  erode excessively        hurricane  breach channel. Greens Bayou, similar to
    during  storms.  Incipient  dunes  occur  along  the         Brown  Cedar Cut, is open only during and shortly
     headlands; most dunes are destroyed by storm surge           following the passage of hurricanes.
                    and breaking waves. ~~~~~The elevation of Matagorda Peninsula averages 5
         The  Rio  Grande deltaic headland  (Brownsville-        to 7 feet above MSL. Continuous low dunes, 8 to 12
    Harlingen map) is characterized by sand beaches and          feet above  MSL,  extend  from  the mouth  of the
    fore-island dunes. The vegetated dunes locally are 30        Colorado River eastward for about 8 miles, and from
    feet high. Breaks in the fore-island dune ridge may be       Greens Bayou westward to within a mile or two of
    a few hundred feet to a mile wide. The storm-tidal           Pass Cavallo. Storm washover channels are common
    surge commonly  breaches and scours the low areas            along the peninsula. Spring high tides and forerunner
    between dunes and floods the Rio Grande delta plain          tides associated with distant storms frequently over-
    and adjacent lowlands. Shoreline erosion is excessive        wash  beaches  adjacent to storm channels. Most of
    even under normal sea conditions, but under storm            Matagorda  Peninsula is overwashed by 5- to 7-foot
    conditions, shorelines may retreat a few hundred feet        storm surges. Continuous dunes with heights greater
    within a few hours. Post-storm processes may accrete         than about 10 feet afford some protection from storm
    the shoreline to its approximate prestorm position.          surge.

                                                          11-12

        During  major storms such as Hurricane Carla            feet with some peaks up to 30 feet above MSL. In
    (1961), two types of washover deposits are developed         historical times, hurricanes have not scoured washover
    along Matagorda Peninsula: shell ramps and washover          channels across the island, but because of the devel-
    fans. Shell ramps are long berms that parallel the           opment  of  several  blowouts  during  the  past few
    elongate peninsula. Individual ramps are a few miles         decades, breaching may occur in the near future.
    long and 180 to 2,180 feet wide. Washover fans are
    lobate sand-shell bodies that accumulate at the bay               St. Joseph Island (Corpus Christi map) also dis-
    terminus of storm channels that transect the peninsula.      plays  prominent  ridge-and-swale  topography.  Veg-
    Small storm surges reactivate the channels and some-         etation on the island is less dense, and blowouts are
    times construct a washover fan along the bay margin.         more numerous than on islands to the east. Average
    Large storms with 10 to 11 feet of storm surge cut           elevation of St. Joseph Island is slightly more than 5
    the peninsula into numerous small islands separated by       feet above MSL. Vegetated fore-island dunes average
    channels up to 1,700 feet wide. These same storms            about 15 feet above MSL; there are some dunes that
    also may erode the shoreline as much as 800 feet             extend  to  35  feet  above  MSL.  Active  washover
    (Shepard, 1973).                                             channels occur at the extreme northeastern and south-
                                                               western ends of the island (Price, 1956; Andrews,
         In South Texas, the gulfward part of the Rio            1970; Nordquist, 1972). North Pass was formed by a
    Grande delta grades northward into south Padre Island        major  hurricane  in  1919  (Price,  1956; Nordquist,
    (Brownsville-Harlingen  map).  South  Padre  Island,         1972). Approximately 9.3 million cubic yards of sedi-
    which originated as a peninsula, is now separated from       ment accumulated along the bayward terminus of the
    the deltaic headland of the Rio Grande by Brazos             washover  channel  as  a  consequence  of  hurricane
    Santiago Pass. South Padre Island is characterized by        activity,  beginning  with  the  1919  hurricane  and
    sand and shell beaches, sparse vegetation, and poorly        continuing through 1971.
    developed fore-island dunes. Its morphology is the
    product of combined wind and storm activity. There is             Mustang Island (Corpus Christi map) is a broad
    little natural defense to prevent breaching of south         barrier which has an average elevation of about 7 feet.
    Padre  Island by  storms of the magnitude of Carla           It does not display ridge-and-swale topography. Veg-
    (1961) and Beulah (1967). Flow across the island is          etated fore-island dunes have an average elevation of
    virtually unconfined during principal hurricanes; for        about 15 feet above MSL and a maximum elevation of
    example, south Padre Island was highly segmented by          about 50 feet above MSL. Vegetation is less dense on
    washover channels during Hurricane Beulah.  Active           Mustang  than  on  islands to the northeast; conse-
    dunes on south Padre Island range in height from 5 to        quently, blowouts, hurricane breaches, and washover
    25 feet above MSL, but they present little resistance        channels are more numerous. Two factors contribute
    to tidal flow once a storm breach has been opened.           to the increased frequency of storm channel breaching
    Width of storm breach channels ranges from about 0.2         on southern Mustang Island. First, there is a south-
    to 1.0 mile.                                                 westward decrease in vegetation along the Texas Gulf
                                                               Coast, and consequently, fore-island dunes are more
        Barrier islands are elongate, detached sand bodies      susceptible to blowouts by wind erosion. Second, a
    that are separated  from  the mainland  by  bays or          major tidal pass existed in the southern Mustang Island
    lagoons and from each other by tidal passes. The five        area until the early 1900's. Hurricanes tend to readily
    barrier islands of the  Texas  Coast are Galveston,          breach those barrier segments that are adjacent to, and
    Matagorda, St. Joseph, Mustang, and Padre. A  gen-           on  the upcurrent  (longshore current) side of, tidal
    eralized profile combining the features of Mustang           inlets such as North Pass on St. Joseph Island and
    Island is shown on figure 10.                                southern Mustang Island (Price, 1952, 1956).

         Galveston Island (Galveston-Houston map) is wide             Padre Island (Corpus Christi and Kingsville maps)
    and  densely  vegetated  and  is  characterized  by          is distinctively different from barrier islands of the
    numerous sand ridges and swales. Average elevation is        central and upper Texas Coast. Vegetation on Padre
    about  5  feet above  MSL;  maximum  elevation  of           Island is less dense, but fore-island dunes are generally
    poorly developed fore-island dunes is about 15 feet          well developed southward along north Padre Island
    above MSL. Hurricane erosion on Galveston Island is          almost to Mansfield Channel. Average dune elevation is
    confined primarily to beaches and dunes.                     about 15 feet above MSL; maximum elevations reach
                                                               about 50 feet above MSL. Near Mansfield Channel,
         Matagorda   Island  (Port  Lavaca  map)  like           fore-island dunes are low and discontinuous; hence,
    Galveston Island  is a broad, sandy island with well-        along  central  Padre Island,  storm-surge flooding is
    defined ridge-and-swale topography and more or less          virtually  unimpeded  and  many  breach or washover
    continuous  fore-island  dunes  (Wilkinson,  1974).          channels are concentrated in the area. Northern Padre
    Average elevation is about 5 feet above MSL. Fore-           Island beaches are generally low and broad and consist
    island dunes on Matagorda Island average about 10            of  terrigenous  sand.  Southward,  beaches  become

                                                        II-13

    shelly, narrow, and high. The height of back beaches          man-made structures in the populated Corpus Christi
    increases  to  about  7  feet  above  MSL,  thereby           region. In monetary terms, Celia was a severe storm.
    providing some protection to fore-island dunes during         Had  Celia made  landfall on deserted central Padre
    storms.                                                       Island and moved  westward over the sparsely popu-
                                                                lated eolian sandplain, there would have been very
        Bay  shoreline  and  in land  areas  are  severely      little loss of life or damage to man-made structures. In
    affected by storm-surge flooding, wave erosion, and           such a setting, Celia would not have been a severe
    fresh-water  flooding  from  hurricanes.  Severity  of        storm.
    storm-surge flooding and destruction of man-made and
    natural features by waves is chiefly a function of bay         PREDICTION OF SEVERE HURRICANE DAMAGE
    size and configuration, presence or absence of cliffs,
    and  location of hurricane landfall. Severity of fresh-            The most severe storm damage can be expected
    water flooding is determined by local topography and          when large hurricanes of the Carla type make landfall
    storm characteristics.                                        (1) where barrier islands or peninsulas are of low relief
                                                                (fore-island dunes are poorly developed or absent), (2)
         Storm-surge  flooding  and  wave  damage  are           where sands constituting barrier islands or peninsulas
    greatest along the shores of large, funnel-shaped bays        are relatively thin, (3) where elongate bays lie to the
    with relatively high cliffs at the bayhead, which lie to      right of the hurricane track, and (4) where the landfall
    the right of the landfall area. As onshore winds within       area is densely populated. Examples of situations (1)
    the right side of the hurricane strike the Coastal Zone,      and  (2) are Matagorda  Peninsula and  south  Padre
    storm-surge height increases toward the heads of bays         Island. Funnel-shaped or elongate bays that may be
    as the  surface  area of the bay decreases and cliff          the sites of extreme storm-surge flooding (situation 3)
    height increases.  Flooding along Matagorda Bay and           are Trinity, Galveston, Lavaca, San Antonio, Corpus
    Lavaca Bay shores during Hurricane Carla, 1961, is an         Christi, and Nueces Bays. Densely populated areas and
    example  of  hurricane  impact  within  funnel-shaped         areas  that  are  currently  experiencing  rapid  devel-
    Texas bays (Bay City-Freeport and Port Lavaca maps).          opment  (situation 4), which can be expected to be
                                                                severely damaged by a Carla-type hurricane, are the
         Bays that lie to the left of the storm track are         south Padre Island area, the Corpus Christi area (in-
    not as severely flooded by storm surge as those lying         cluding the smaller cities adjacent to the bays), the
    to the right because storm tides and waves are driven         Port Lavaca area, the Galveston-Houston area, and the
    toward the Gulf of Mexico on the left side of the             Beaumont-Port Arthur area.
    counterclockwise wind systems. In this situation, most
    of the surge and wave attack is directed toward the                The Beulah-type hurricane causes extensive flood-
    back side of peninsulas and barrier islands.                  ing. Man-made structures (i.e., residences, farm build-
                                                                ings, recreational facilities) situated on floodplains and
         Low-lying  areas, such as marshes, delta plains,        adjacent to creeks and rivers can be expected to be
    and river floodplains, are commonly flooded by storm          damaged  or destroyed. A  storm such as Beulah in
    surge. River floodplains and flat upland areas also may       1967, or Carmen in 1974, does not necessarily have to
    be extensively flooded by rainfall associated with a          make landfall along the Texas Coast to cause flooding
    hurricane that moves slowly inland. Unless these areas        along Texas creeks and rivers. For example, Carmen
    are inhabited, little damage occurs; salt to brackish         struck the Louisiana coastline during the first week of
    marshes are temporarily freshened.  Floodplains may           September in 1974. She was still influencing weather
    pond water for months.                                        in Texas as late as the second week in September,
                                                                triggering excessively heavy rainfall in the Coastal
                      Population Density                         Zone  between  Port Lavaca and Sinton. During the
                                                                early morning of 13 September 1974, up to 17 inches
         Storm-surge flooding, breaking waves, wind, and         of rain fell on the Papalote Creek drainage, a tributary
    fresh-water flooding may  cause considerable destruc-        to Aransas River. Flooding of Papalote Creek from
    tion in areas that are sparsely populated, but because        this heavy  rainfall  was  greater  than  the  flooding
    of the low population density, this kind of natural           experienced during the earlier Hurricane Beulah rains.
    damage does not significantly affect man. Perhaps the
    severity of a hurricane should, therefore, be measured              MITIGATION OF HURRICANE IMPACT
    in terms of its impact on man and man-made struc-
    tures or developments-according  to this viewpoint,               Hurricanes cost the people of Texas millions of
    the  greater  the  population  density,  obviously  the      dollars (table 6). Several methods have been employed
    greater the severity of the storm.                            to reduce the destructive potential of hurricanes. Miti-
                                                                gation of the hurricane hazard is in part accomplished
         Hurricane Celia was a small hurricane with high-         by (1) reliable forecasting and prediction, (2) formu-
    velocity  winds,  which  damaged  or destroyed many           lating evacuation procedures, (3) strengthening natural

                                                          11-14

    defenses  such  as fore-island dunes,  and  (4) erecting                               B. HURRICANE BEULAH
    rigid structures to withstand wave attack or to retard
    waves  and  prevent  storm-surge  flooding.  Another                              Tidal     Win ad    Stream faooding
    possible method of reducing the destructive potential               Type of loss   flooding   wind-driven    and pnndng
    of a storm lies in altering the storm itself. Finally, the                                    rain
    most  certain  means  of  reducing  storm  damage  is               Agriculture     0         6,835       31,019       37,854
    avoidance.   Need   for   mitigation   throughout   the             Commercial    2.241       1192         6,370        9,803
    Atlantic and Gulf coasts becomes  progressively more                Residential    615       21,457       25,463       47,535
    urgent since there was a 40-percent increase in beach               Services      2,097      12,781       35,474       50,352
    residents  between  1960  and  1970  (Frank,  1974).                Total         4,953      42,265       98.326      145,544
    Although  numerous  problems  arise from  such  rapid               Lives lost: 15 persons in Texas
    growth in the Coastal Zone, perhaps the most critical
    problem is the lack of hurricane experience of many
    of the new coastal residents.                                                           C. HURRICANE CELIA

         Forecasting and prediction are now  very sophis-               Type of loss     Wind damages    Tidal flooding   Total
    ticated.  Hurricanes  are carefully  monitored  by  elec-
    tronic methods,  by  air surveillance, and by weather               Agriculture          19220             13         19,233
    satellite. Residents in the vicinity of predicted landfall          Residential         199,652         3,523        203,175
    generally have sufficient time to evacuate the area. On             Commercial           44,375           917         45,292
    the other hand, the time may be approaching when it                 Industrial          75,980           8.705        84,685
    will be  impossible  to entirely evacuate some  coastal             Public               33,633           150         33.783
    areas, e.g., barrier islands. A mass exodus of hundreds             Transportation         540           1,186          1.726
    of thousands of people by automobile across con- Utilities21 2 2 8 7210
                                                                           Utilities     ~21,922           187         22,109
                                                                      Marine               3,100          7,029         10,129
    gested causeways may not be physically possible. Two                Automobiles          18,944           620          19,564
    alternatives may be considered in order to reduce the               Services            22,372          5,243         27,615
    number of people that would be required to flee the                 Total               439,738         27,573       467,311
    islands. First, with better forecasting, it may become               Lives lost: 13 persons
    possible to determine with even greater accuracy the
    "direct hit" and  "fringe" areas.  Evacuation  of resi-             Estimated losses from hurricanes since 1900: $1,271,983,000
    dents in the direct hit areas would be required; those            _
    in fringe areas would remain. A second alternative to             vegetation cover. Many dunes have been weakened or
    evacuation would be the utilization of specially struc-           destroyed through devegetation. This occurs naturally
    tured  high rises (hotels, motels,  condominiums,  and            during  droughts  and  as a result of man's activities.
    apartments) as vertical refuges (Frank, 1974).                    Attempts have been made to strengthen dunes through
         Fore-island dunes if present form the first line of          artificial  stabilization  by  increasing  the  vegetation
    natural  defense  against  storm  surge  and  breaking            density. Most notable of these ventures has been on
    waves.  The  ability of dunes  to withstand  hurricane            the  barrier  islands  of  North  Carolina  (Dolan  and
    attack is dependent  upon  the density  of stabilizing            Godfrey,  1973; Dolan  and  Odum, 1973). Artificial
                                                                    dune stabilization in North Carolina, however, has
         Table 6. Losses from recent hurricanes. (A) Hurricane        aggravated shoreline erosion.
    Carla, (B) Hurricane Beulah, (C) Hurricane Celia. Values in
    thousands of dollars. Data from U. S. Army Corps of Engineers
    (1962, 1968, 1971a). Note that data do not necessarily agree           The  Galveston seawall is an example of an engi-
    with  that provided  by  National  Oceanic and Atmospheric        neering approach to retard hurricane damage, but as a
    Administration (1900-1974).                                       result of stabilizing the shoreline, the beach has been
                        A. HURRICANE CARLA                           lost. The  seawall was  erected specifically to protect
      Type of loss         Tidal flooding   Wind and Rain    Total    the city against overflows from the sea (Davis, 1961).
                                                                   Sand, excavated from western Galveston Island, was
      Agriculture             19,544        41,314      60,858        used to fill part of the low area behind the seawall.
      Residential            105,779        66,441     172,220        Bulkheads and revetments are also commonly used to
      *  Commercial buildings  39,148       25,658      64,806        protect some bay shores from hurricane wave attack.
      and contents                                                   Other  proposed methods to alleviate potential storm
      Industrial plants       11,683         3,349      15,032        surge and wave damage to bay-shore property include
      Transportation           9,207         3,141      12,348
      Transportatility         1,27    3      ,11        2,3485       the use of breakwaters  constructed  within the bays
      Utility 1,198                          8,787       9,985
      Miscellaneous           13,636         6,801      20,437        specifically to reduce wave action, and the construc-
      Services                                -         52,604        tion of a system of locks which, in the event of a
      Total                  200,195       155,491     408,290        hurricane, could  close  off the tidal and  navigation
      Lives lost: 32 persons channels.

                                                            11-15

        Two  other means of lessening damage potential                              0 FLOODING   0
    are to avoid those areas that are prone to storm-surge
    and  fresh-water  flooding  and  to  enact appropriate                         GENERAL STATEMENT
    building codes; areas that have been flooded by storm
    surge and fresh water are shown on Natural Hazards                   Two principal types of flood hazards exist in the
    Maps. Buildings can be constructed to withstand the             Texas  Coastal  Zone:  storm-surge tidal flooding and
    high-velocity winds and sudden pressure changes asso-           fresh-water flooding. During the passage of hurricanes
    ciated  with  hurricanes.  Elevation  of  buildings  by         and tropical storms, storm-surge tides may flood low-
    utilizing  pilings can  eliminate  most  of the damage          lying coastal areas up to elevations above 20 feet (fig.
    from  storm-surge  flooding,  but  will  not  eliminate         7). Fresh-water flooding, on the other hand, results
    damage or destruction from breaking waves.                      from  hurricane-aftermath  rainfall,  as  well as from
                                                                severe thunderstorms and frontal-related storms. Fresh-
         Attempts have been made to alter the hurricane            water flooding may occur as stream flooding of flood-
    itself, and research is being conducted to determine            plains or as rainfall flooding of broad areas of the
    the feasibility of altering tropical storms (Dunn and           coastal plain. On the flat coastal plain, the runoff is
    Miller, 1964; Simpson, 1966). The object of hurricane           ponded  in  natural  depressions  or dammed  behind
    modification is to decrease the steep pressure profile          highways, railroads, and other man-made structures.
    (hence decrease the wind velocity) and to convert the
    hurricane to a tropical storm. Profiles through hurr-                Shoreline  erosion  and  land  subsidence,  both
    canes and tropical storms  (fig. 11) show that wind            natural  factors that can  be  accelerated  by  human
    velocity and pressure gradient are greatest near the eye        impact, are increasing the hazard of storm-surge and
    of a hurricane. The tropical storm, which has no eye,           fresh-water flooding in the Coastal Zone. As shorelines
    has a much  lower wind velocity than hurricanes. At             retreat, or as lands subside, greater areas of the Coastal
    present,  cloud  seeding  appears  to  be  a promising          Zone are exposed to storm-surge tides. Similarly, land
    method to reduce wind speed and eliminate the eye.             subsidence, whether due to natural compaction and
    The seeding method may never lead directly to useful            subsidence or to ground-water withdrawal, produces
    modification, however, because hurricanes are so large          broad irregular depressions that can pond substantial
    and their energy is so enormnous (Simpson, 1966). A            volumes of rainfall on the impermeable muddy sub-
    hurricane  with  moderate  strength releases as much            strates  of  much  of  the  lower  coastal  plain.  Ship
    condensation  heat energy  in a day  as the nuclear             channels,  irrigation ditches, and extensive dikes, re-
    fusion energy of four hundred 29-megaton hydrogen               lated both  to agriculture  and  industrial/commercial
    bombs. Significant modification of hurricanes may be           development, may also serve to aggravate the impact
    impossible.  It also may  prove to be undesirable to            of the storm-surge tide and to impede rainfall runoff.
    destroy a hurricane or to alter its course, since these
    storms supply a quarter to a third of the rainfall in                Those areas actually flooded by the storm-surge
    critical areas of the world.                                   tides that accompanied Hurricanes Carla and/or Beulah
                                                                (3,164 square miles) are shown on the Natural Hazards
      80 -                                                         Maps.  Likewise,  areas flooded by  Hurricane Beulah
                                                                aftermath rainfall (2,187 square miles) define the
                                                                extent of fresh-water flooding (stream flooding,
                                                                ponding, and dammi-ng) in the Texas Coastal Zone
      70 4between Bay City and Brownsville. Data on Hurricanes
       (3                                                          Carla and Beulah were obtained from the U. S. Army
                                                                Corps of Engineers (1962, 1968) and are based on
       -  v6,- -HURRICANE                                          aerial  photographs,  drift-line  observations,  and  a
     >.                                                             variety of recording gages. The reader is referred to
                   t    ~~~~~~~~~~~~~~the above reports, as well as to a report on Hurricane
     050                                                            Celia (U. S. Army Corps of Engineers, 1971a) and a
                    J   ~~~~~~~~~~~~~report on hurricane-surge frequency estimated for the
         W    0\
     >40 -        N,                                               Texas Coastal Zone  (Bodine,  1969). Maps and text
                                                                which were distributed as part of the Texas Hurricane
                     30-  -                                       ~~~~~~~~~~Awareness Program by the Texas Coastal and Marine
      20-         TRPCL-                   a'--   -  ._Council (1974) also provide information on flooding.
        20-        STORM
        306         9 0                   IS              8             In the  northeastemn part of the Coastal  Zone,
                          RADIUS (N. M.)                          where  adequate  hurricane-aftermath  flood  data  are
      Figure 11. Velocity profiles characteristic of hurricanes and  generally unavailable, areas of possible stream flooding
    tropical storms. After Simpson (1966).                         (2,073 square miles) shown  on the Natural Hazards
                                                                Maps are based upon the distribution of floodplain

                                                         11-16

    sediments and upon the geomorphic character of the           plain  (fig.  9). The  frequency  of storm-tidal  surge
    stream systems. Areas that will be flooded by ponding        greater than 10 feet is consistently and substantially
    of excessive rainfall were not delineated for the north-     greater for bays than for open Gulf beaches (fig. 12).
    eastern part of the Texas Coastal Zone because the
    necessary mapping of subtle topographic variations is                            Rainfall Flooding
    beyond the resolution of regionally available topo-
    graphic maps.  In addition, the degree of ponding is              Rains may  precede the landfall of a hurricane,
    also related to the efficiency of highway and railroad       but as the storm center moves inland, heavy rainfall,
    drainage systems, which may be blocked by driftwood          often accompanied by tornadoes, generally strikes the
    and other debris.                                            coastal plain (fig. 7). If the hurricane moves directly
                                                               inland, the period of heavy rainfall may be limited to
        The  flood-prone  areas  shown  on  the  Natural        three or four hours. If the storm moves parallel to the
    Hazards Maps are, therefore, based principally upon          coastline or repeatedly changes its forward direction,
    historical  or  geologic  evidence  and  not  upon           excessive rains may continue for many hours or even
    theoretical prediction and extrapolation methods.            several days. For example, in 1967 Hurricane Beulah
                                                               remained in the South Texas area for almost three
                  FLOODING PROCESSES                            days; up to 32 inches of rain fell in the region during
                                                               the five or six days following landfall (fig. 8). Stream
               Hurricanes and Tropical Storms                   flooding and ponding inundated 1.4 million acres of
                                                               land while only 630,000 acres were flooded by storm-
         As  previously  described,  the  most  destructive      surge tides (U. S. Army Corps of Engineers, 1968).
    aspect of hurricanes that have struck the Texas Coast
    (table  4) is the  impact  of  the storm-tidal surge;             Hurricane-aftermath rainfall is generally so exces-
    widespread forerunner tides of lesser magnitude may          sive that coastal streams inundate floodplains. Flood-
    precede the storm-surge tides. Storm surge, which is         waters are discharged  into  the various Texas bays,
    generated  within  the storm by the low barometric           which are already experiencing high tides. As a result,
    pressure  and  the  intense,  counterclockwise  winds,       combined  storm-surge  tides  and  overbank  stream
    strikes the coast as the storm  makes  landfall and          flooding may  devastate vast areas of the flat, lower
    spreads across the low coastal plain with lethal results.    coastal plains. As the hurricane moves inland, rainfall
    Most  property  damage  and,  more  critically,  most        runoff continues to flood drainage systems; streams
    deaths result from the surge of ocean water across           may  discharge floodwaters into bays for many days
    exposed, low-lying barrier islands and mainland shore-       following storm passage.
    lines (table 6). Nine out of ten deaths as a result of
    hurricanes are caused by drownings (Texas Coastal and             Ponding  of rainfall on  the coastal  plain may
    Marine Council, 1974). As the hurricane moves ashore,        inundate more area than stream flooding. Most of the
    floating debris propelled by the storm surge adds to         lower 50 miles of the coastal plain is underlain by
    the damage inflicted by the rising water and pounding        flat-lying, poorly drained, moderately to highly imper-
    waves. The greatest property losses result both from         meable sediments  (refer to "Environmental Geologic
    flooding and from the battering effect of water-carried      Atlas of the Texas Coastal Zone," Fisher and others,
    debris. The devastation imposed  upon Mississippi in         1972, 1973; also Fisher, 1973); rainfall runoff is high
    1969 by Hurricane Camille was caused principally by a        because of this relatively impervious substrate.
    storm surge of nearly 25 feet above MSL. Most
    seawalls  and  hurricane  protection  dikes  along  the           Although lives may be lost in hurricane-aftermath
    Texas Coast are less than 20 feet above sea level.           flooding,  more  commonly  the principal loss is to
                                                               property such as bridges, highways, and homes.
                       Storm-Surge Tides                        Thousands   of  persons  may   be  left  temporarily
                                                               homeless by the stream flooding and ponding; trans-
         A  general  model that illustrates the nature of        portation  systems  may  be  destroyed  or  blocked.
    storm-surge tidal flooding along the Texas coastline         Flooding also damages water and sewerage facilities,
    during approach and passage of a hurricane has been          leading to the threat of epidemic diseases.
    previously described (fig. 7). The elevation of the
    storm-surge tide generated by a hurricane is generally
    less on the Gulf shoreline (barrier islands, peninsulas,                     Frontal-Related Storms
    headlands) than along the shorelines of constricted
    bays  and  estuaries where storm-tidal surge may  be              Storms associated with more normal meteorologic
    significantly elevated. A storm surge greater than 10        circulation also produce flood hazards in the Coastal
    feet above  MSL, therefore, may  occur within con-           Zone.  Although thunderstorms are generated during
    stricted bays because of superelevation of the tide on       the summer  months  in the coastal region by con-
    the gently sloping bottoms and on the adjacent coastal       vection, most severe weather, excluding hurricanes and

                                                         11-1 7

    tropical storms, is related to frontal systems that move      MSL possible on the Gulf beaches and with more than
    eastward   and  southeastward   across  the  North            20 feet of storm tide possible within restricted bays
    American continent. In the winter, polar fronts may           (fig. 12), the potential flood-prone area of the Texas
    move rapidly into the coastal area suddenly bringing          Coast may be significantly greater than the net area
    low temperatures, rain, and strong northerly winds.          reported for Carla and Beulah flooding.
    These storms may last for two or three days, during
    which time some locally heavy rainfall can occur. The              A  total of 5,787 square miles of Texas coastal
    northerly  winds  may  generate flood  tides that in-        plain ties below an elevation of 20 feet above MSL
    undate wind-tidal flats and other low areas, especially       (table 1). Much of this land below an elevation of 20
    along the southern margins of the bays and the back           feet may  be flooded locally when maximum storm-
    sides of barrier islands. Wind-tidal flooding is slow, and    surge conditions are focused on the specific section of
    it does not present a serious hazard.                        the Texas shoreline.

         During spring and fall, when polar fronts diminish            In the Beaumont-Port  Arthur  map  area, Carla
    in strength, the cooler air mass of the frontal system is     floodwaters moved inland from the Gulf beaches for
    unable to maintain its momentum against warmer Gulf           15 to 20 miles and reached up the Neches River valley
    air; stationary fronts (sometimes called warm fronts)         to the vicinity of Beaumont. Tidal levels ranged from
    result. These broad fronts, which lift warm Gulf air          6.8 feet above MSL at Orangefield to 10.5 feet above
    aloft, may remain in the coastal region for many days         MSL  northwest of High Island. Flood levels reached
    while  generating  widely  distributed  rainfall. Serious     8.5 feet above MSL at the mouth of the Neches River,
    flooding of coastal streams may occur but rarely to           7.9 feet near Port Neches, 5.0 feet near Port Acres,
    the degree experienced during hurricanes and tropical         7.6 feet at Port Arthur, 9.4 feet along the northern
    storms.                                                       shore of Sabine Pass, 8.6 feet near Big Hill, and 8.9
                                                                feet at High Island.
                   FLOOD-PRONE AREAS                                  A total of 583 square miles of coastal lands in
                 Storm-Surge Tidal Flooding                      the Beaumont-Port Arthur map area were flooded by
                                                                Hurricane Carla. If the center of a Carla-level storm
         Between  1900 and 1972, 27 hurricanes (winds            struck  the  Sabine  Lake  area, tidal flooding might
    greater than 74 mph) and many less severe tropical            inundate areas up to elevations of 15 to 20 feet, hence
    storms (winds greater than 39 mph and less than 74            covering 20 to 30 percent more land than indicated on
    mph)  struck the Texas Coast (table 4), generally in          the Natural Hazards Map. Although only two hurri-
    August or September (fig. 3). This constitutes a rate         cane  washover  channels  have been  recognized near
    of one hurricane every 2.5 years. Very few areas of           High  Island, Hurricane Carla floodwaters apparently
    the Texas Coast have escaped hurricane impact during          crossed  the low-lying shoreline at many  points to
    this century. Each hurricane is a rather unique storm         flood  the  broad  marshlands  along the Intracoastal
    in terms of the nature and degree of winds, storm             Canal.
    surge, and aftermath rainfall. Every bay, barrier island,
    peninsula, and headland exhibits some unique physical              In  the  Galveston-Houston  map   area,  Carla
    variations which can serve to modify the impact of            flooding extended inland for 15 miles in the Angleton
    storm-surge tides.                                            area, covered most of Galveston Island and Bolivar
                                                                Peninsula, most of Smith Point area, and extended up
         Two  recent  well-documented  hurricanes (Carla,         the Trinity and San ,Jacinto river valleys. Flooding
    1961 and Beulah, 1967) have been used in this atlas          along the western side of Galveston Bay extended up
    to define known  limits of storm-surge flooding and           Dickinson Bayou and Clear Creek to Interstate 45. On
    aftermath-rainfall flooding (table 5). Flood-surge eleva-     the Gulf beaches, maximum  tidal levels of 9.6 and
    tions and area of flooding are based on studies by the        12.1  feet  above  MSL  were  recorded  on  Bolivar
    U. S. Army Corps of Engineers (1962, 1968); flood             Peninsula and central Galveston  Island, respectively.
    elevations are based on drift line and various gage           Tide levels reached 14.0 feet above MSL at Wallisville,
    measurements.  Although  Carla  and Beulah  flooded           13.4 feet at Anahuac, 9.8 feet at Smith Point, 14.1
    3,164 square miles, they probably do not represent            feet at Baytown, 15.0 feet at Morgan Point, 14.2 feet
    ultimate  hurricanes.  One  must assume, nevertheless,        at the mouth of Clear Creek, 12.7 feet at Dickinson,
                   thatstors sch a  Cara o  Beuah my eentully    11.0 feet at Texas City, and 14.7 feet at Chocolate
    strike other parts of the coast. For instance, should a       Byu
    Carla-type storm directly strike the Galveston area
    (such as the 1900 storm, table 4), the area of tidal               Hurricane Carla tidal waters flooded 694 square
    flooding  could  be  much  greater  than  the  actual         miles of the Galveston-Houston  map  area. If tidal
    flooding  that  occurred  when  Carla  struck  Port           flooding  were  to approach  15  to 20  feet in the
    O'Connor.  With storm  flood tides of 15 feet above           Galveston Bay vicinity as a result of the direct impact

    of the center of a Carla-level storm, perhaps 10 to 20         west side of Carancahua Bay, 20.1 feet at the State
    percent more land area would be flooded than indi-             Highway 35 bridge over the upper part of Carancahua
    cated on the Natural Hazards Map. Seven potential              Bay,  16.3  feet in Keller Bay,  17.3  feet at Point
    washover  channels occur on  Galveston  and  Follets           Comfort, 22.0 feet at Port Lavaca, 15.4 feet near Port
    Islands; other  channels  may  develop  during severe          O'Connor, 10.3 feet at the ship channel on Matagorda
    hurricanes.                                                    Peninsula,  12.3  feet  along  the  west  side of Pass
                                                                Cavallo, 12.1 feet at Matagorda Island Air Force Base,
         Continued   land  subsidence  centered  in  the           11.2 feet at Seadrift, 10.3 feet on the west side of San
    Baytown region is yearly subjecting greater areas to           Antonio Bay, and 7.3 feet at the State Highway 35
    potential tidal flooding. If the flood levels that oc-         bridge over Copano Bay. Hurricane Carla tidal surge
    curred in Galveston Bay during Hurricane Carla, in             flooded 495 square miles in the Port Lavaca map area.
    1961,  were  to  strike  Galveston  Bay  today,  it is         Tidal-flood levels generally coincided with the 20-foot-
    estimated  that  approximately  70  additional square          elevation contour line along and to the right of Carla's
    miles would be subjected to flooding because of land           landfall. Had Carla made landfall at St. Joseph Island,
    subsidence (Texas Coastal and Marine Council, 1974).           perhaps an additional 5 to 10 percent of the western
                                                                 part of the Port Lavaca area would have been inun-
         In the Bay City-Freeport map area, tidal flooding         dated by tidal floodwaters. Two hurricane washover
    by Hurricane Carla extended inland approximately 10            channels have been recognized near the western end of
    miles  from  the  Gulf  beach.  Most  of  Matagorda            Matagorda  Peninsula; Vinson  Slough  on  St. Joseph
    Peninsula and the Colorado River delta were inundated          Island is a major washover channel.
    and flood tides moved from 3 to 8 miles inland from
    the shoreline of east and west Matagorda Bay. Flood-                In the Corpus Christi map area, land inundated
    tidal levels were measured at 10.9 feet above MSL at           by tidal flooding by Hurricane Carla in 1961 slightly
    the mouth of the Brazos River and 5.2 feet above               exceeded the area flooded by Hurricane Beulah, which
    MSL at the Freeport channel; other levels include 13.8         made  landfall near the Rio Grande in 1967. Carla's
    feet above MSL at a site on the Brazos River about 7           tidal surge flooded most of southern St. Joseph Island,
    miles inland, 11.0 feet near the mouth of the San              Mustang Island, and northern Padre Island, except for
    Bernard River, 13.7 feet about 10 miles inland along           elevated areas comprising fore-island dunes and stabi-
    the San Bernard River, 14.1 feet on Lake Austin, 13.7          lized blowout dunes. Tidal flooding extended for 10
    feet along the Intracoastal Canal on the north side of         miles  up  the  Mission,  Aransas,  and  Nueces  river
    East  Matagorda  Bay,  15.3  feet near the town  of            valleys.  Low-lying  areas surrounding Port Bay were
    Matagorda, and 15.4 feet at Palacios.                          similarly  inundated.  Minor  tidal flooding  occurred
                                                                 along the landward sides of Corpus Christi Bay and
         Hurricane Carla tidal surge flooded 564 square
                                                                 northern Laguna Madre. Measured Carla tidal-flood
    miles of coastal lands in the Bay City-Freeport map
    area. The Bay City-Freeport map area was situated to           levels include 7.3 feet above MSL at the mouth of the
    area. The Bay City-Freeport map area was situated to
                                                                 Aransas River, 7.9 feet on the east side of Port Bay,
    the right of Carla's center when the hurricane made
    landfall. This location, relative to the hurricane's eye       7.5          feet       n      ear Key Allegro,  9.3 feet at Port Aransas,
    received some of the most intense winds and storm              and  5.9  feet at the  southeast  end  of  Lve Oak
    tides experienced along the entire coast. If tidal-flood       Peninsula near Ingleside. Measured  reulah tidal-flood
    levels were to approach 15 to 20 feet in the area,   elevations in the Corpus Christi map area include 8.0
    levels were to approach 15 to 20 feet in the area,
    perhaps 10 percent more land area would be flooded             feet above MSL on northern Mustang beach, 7.3 feet
                                                                 at Portland, 7.3 feet near the bay bridge at Corpus
    than indicated on the Natural Hazards Map. Numerous                                                 y      g
    hurricane  washover  sites  occur  along  Matagorda            Christi,  8.2  feet at  the Corpus  Christi Naval  Air
    Peninsula.                                                     Station, 6.8 feet at the Flour Bluff bridge, and 8.8
                                                                 feet in upper Oso Bay.
         The  eye of Hurricane Carla crossed the Texas
    coastline at Pass Cavallo, located in the Port Lavaca               The elevation of Carla's tidal surge significantly
    map  area.  Flood  tides  were  highly  elevated  in           diminished  southwestward  across the Corpus Christi
    Carancahua Bay, Keller Bay, and Lavaca Bay. Tidal              map  area; this region  was  located on  the left or
    waters moved from 10 to 18 miles up Garcitas Creek             low-intensity  side of Carla's storm  center  (fig. 9).
    and the Lavaca River, respectively. Most of the land           Hurricane Carla's tidal flooding inundated 203 square
    area between  Seadrift and Port Lavaca was flooded;            miles in the Corpus Christi map area; Hurricane Beulah
    very little of Matagorda  Island remained emergent.            flooded  only  slightly less area.  If the center of a
    Extensive  flooding  occurred  in  the  Green  Lake-           Carla-level storm made landfall at Port Aransas, tidal
    Guadalupe delta area, along Blackjack Peninsula, and           levels might reach 15 to 20 feet above MSL and an
    in the vicinity of St. Charles Bay.                            additional 10 to 15 percent of the land area would be
                                                                 flooded by the surge, particularly in the Port Bay and
         Measured  Carla  tidal-flood  levels  in  the  Port       Laguna Larga-Oso Bay areas. Broad hurricane washover
     Lavaca map area include 18.4 feet above MSL on the             channels occur at the southeastern end of St. Joseph

                                                             II-19

    Island  and  in  the  Packery-Newport-Corpus  Christi                        Stream Flooding and Ponding
    channel area on southern Mustang and northern Padre
    Islands.                                                             On the Natural Hazards Maps, flood-prone areas
                                                                resulting from rainfall associated with tropical storms,
                                                                hurricanes, and frontal systems are based on two
         Storm-surge tides generated by Hurricane Beulah
                                                                sources: (1) data on Hurricane Beulah flooding (U. S.
    in the Kingsville map area far exceeded Carla's tidal          Army  Corps of Engineers, 1968) served as a guide to
    flooding in the area. Hurricane Beulah storm tides             flood-prone  areas in South Texas between the Rio
    inundated  much  of Padre Island, all tidal flats and          Grande and the Lavaca/Navidad River system; and (2)
    low-lying  areas along  the landward side of Laguna            aerial photographs, topographic maps, and field obser-
    Madre, large areas adjacent to Baffin Bay, and the             vations were used to delineate flood-prone areas (based
    lower reaches of Olmos Creek, San Fernando Creek                on    eologc/eomorhc   evidence                      the
    and Petronilla Creek. Hurricane Beulah tidal flooding                                                 the
                                                                 Lavaca/Navidad River system and the Sabine River
    inundated 288 square miles in the Kingsville map area.
    Measured Beulah flood-tide elevations include 8.7 feet         where regional rainfall flood data are unavailable. The
    above MSL at Malaquite Beach (Padre Island National            use  of  Beulah  stream  floodig  and  pondig  data
    Seashore), 5.6 feet at Penascal Point at the mouth of          provides an actual historical example of flooded areas.
    Baffin Bay, 8.8 feet near Loyola Beach, and 10.9 feet          It  should be realized, however, that the fresh-water
    along the lower reaches of San Fernando Creek.                 flood area shown  on the Natural Hazards Maps is
                                                                 probably a conservative estimate below the maximum
                                                                 flood levels which can occur in the region. Northeast
         If the center of a Beulah- or Carla-level storm           of the Lavaca/Navidad River basin, flood-prone areas
    were to make landfall along north-central Padre Island,        are  underlain  by  floodplain  sediments,  which  are
    10  to  15  percent  more  land would  probably  be            geologic evidence of flooding.
    inundated by tidal flooding, especially in the Baffin
    Bay  region, on Padre Island, and within low areas                  In  the  south  coastalareas,  Hurricane Beulah
    associated with the extensive sand dune fields. Much           delivered approximately  30 inches of rainfall in less
    of Padre Island near the land-cut area was breached by         than one week. It is one of the best documented flood
    hurricane washover channels.                                   events in the region. Although Beulah-related rainfall
                                                                was general in the region, certain areas received anom-
                                                                alous quantities of precipitation. For this reason, one
         In the Brownsville-fIarlingen map area, Hurricane         must recognize that the fresh-water flood limits on the
    Beulah  tidal  flooding  inundated  most  of southern          Natural Hazards Maps are not based upon  uniform
    Padre  Island  and  all of  the  extensive  tidal flats,       rainfall within each stream system.
    particularly in the Arroyo Colorado area and in the
    vicinity of the  Brownsville ship channel. Hurricane                Every stream between the Rio Grande and the
    Beulah did not strike the south Texas Coast head-on,           Lavaca/Navidad   Rivers  experienced   flooding;  the
    but moved into the region from Mexico, almost par-             general limits of flooding are shown on the Natural
    allel to the coastline. For this reason, the Brownsville       Hazards Maps. Flooding inundated 2,187 square miles
    region may have experienced lower storm tides than it          (table 1). Extensive ponding occurred between Baffin
    would if the hurricane had moved directly westward             Bay and the North Floodway/Arroyo Colorado area,
    out of the Gulf of Mexico.                                     where stream drainage is essentially nonexistent within
                                                                the broad fields of sand dunes. Impervious substrates,
         Measured Beulah tidal elevations include 6.9 feet         which occur locally beneath the dunes, coupled with
    above MSL  at Port Mansfield, 3.5 feet on the Gulf             the hummocky sand ridges and blowout depressions,
    beach  south  of Mansfield jetty, 5.3 feet along the           ponded the rainfall and inhibited its runoff to the
    Intracoastal Canal at the mouth of Arroyo Colorado,            Gulf of Mexico.  Earthen embankments along State
    3.9 to 7.4 feet on southernmost Padre Island, 7.5 feet         Highway 77 and the Missouri Pacific Railroad locally
    on the Gulf beach at Boca Chica, 6.3 feet near Port            retarded runoff. Ponded water remained for months
    Isabel, and 8.5 feet along State Highway 48, halfway           before evaporation and slow percolation combined to
    between Boca Chica and Brownsville. Sugg and Pelissia          lower water levels.
    (1968) reported a high-water mark of 12 feet above
    MSL in a house at south Port Isabel. Hurricane Beulah               In  the  northeast  coastal  area  between  the
    tidal  surge  flooded   336  square  miles  in  the            Lavaca/Navidad Rivers and the Sabine River, Beulah
    Brownsville-Harlingen map area; much of this flooded           rainfall was insufficient to produce stream flooding
    area consists of low tidal flats. If the center of a           and  ponding.  Because  of the  absence  of regional
    Beulah- or Carla-level storm were to strike the south          historic rainfall data for the upper region of the Texas
    Texas Coast while moving westward or southwestward,            Coastal  Zone,  flood-prone  areas  on  the  Natural
    a significantly greater land area than indicated on the        Hazards Maps are based on geologic and geomorphic
    Natural Hazards Maps might be flooded.                         evidence. On the Natural Hazards Maps, these areas,

                                                            II-20

              which cover 2,073 square miles (table 1), are called           complex and variable bays. The variety of bathymetry,
              " potential areas of fresh-water flooding by hurricane         shoreline  configuration,   and  other  factors  make
              rainfall." The areas are underlain by floodplain sedi-         accurate prediction of surge within bays much more
              ments, which verify their flood potential. This flood          difficult. Estimates of the frequency of surge heights
              category is comprised chiefly of river or stream valleys       on the Gulf shore at Freeport and within Galveston
              and  adjacent  depressed,  poorly  drained  areas that         Bay at Baytown are shown on figures 12A and 12B3;
              occasionally may be flooded by overbank discharge of           figure 12C shows predicted Gulf beach tidal elevations
               the stream, as well as by intensive hurricane rainfall.        along the entire Texas Gulf Coast.
               Such flood-prone areas can be delineated with rea-
               sonable accuracy, but they do not represent flooding                Hurricane-tidal levels will be predicted with in-
               by a single, observed flood event similar to that caused       creasing accuracy, especially along the Gulf beaches,
               by Beulah rainfall.                                            Because of the variability of the Gulf hurricane, its
                                                                           path, and its interaction with the highly variable
                    Delineation of potential areas of ponding are not         configuration  of  Texas  bays,  precise  prediction  of
               included  for  the northeastern  part of the  Coastal          maximum flood levels will take many years to perfect.
               Zone. Ponding results from a complex  interplay of             In the meantime, the charting of observed flood events
               subtle topographic depressions, water-table elevations,        provides a valuable guide to flood-prone areas.
               man-made structures, and available drainage systems.
               For this reason, the precise limits of ponding can best
               be determined by actual experience. Ponding rarely             MITIGATION AND AGGRAVATION OF FLOODING
               leaves a distinctive geologic deposit that can be used
               to determine its limits.                                            Before man settled the Texas Coastal Zone, hurri-
                                                                           cane processes, along with all coastal and marine
                           Predicting Flood-Prone Areas                      processes,  were  generally  in  equilibrium  with  the
                                                                           natural coastal environments. Hurricanes are but one
                   Meteorologists  and  engineers  have   correctly          of a large number of natural phenomena that probably
               placed a high priority on learning to predict the level        have operated for tens of thousands of years in the
               of tidal surge caused by hurricanes. When enough is            Texas coastal region. Before man  arrived, the storms
               known about tidal levels, wind direction and intensity,        expended  much  of their great energy in the coastal
               atmospheric  pressure,  and other factors, it may  be          system and brought about, in a natural way, certain
               possible to  construct  reasonably  accurate hurricane         physical and biologic changes. The slow evolution of
               prediction models. Hurricanes strike Texas an average          the Texas Gulf Coastal Zone has been affected by the
               of once every 2.5 years. Meager quantitative data are          tropical cyclone.
               available on most of these storms, especially data at
               many  sites along  the Gulf beaches and within the                  Tropical  storms  and  hurricanes  have  effected
               bays. For this reason, insufficient data exist at this         certain  changes  in the  region;  barrier islands were
               time to develop a truly accurate and statistically valid       modified and, perhaps, even their origin was, in part,
               model (Bodine, 1969). A dense network of tidal gages           controlled  by  such  storms.  Bays  were  flushed and
               and other recorders are needed throughout the region.          supplied with marine nutrients; sediment was eroded
               Even  if such a data system were now  available, it            and  redistributed.  When  man  became  part  of the
               would take many years to sample a sufficient number            coastal system, however, hurricanes became disastrous
               of hurricanes  to generate  highly reliable prediction         because man  does not necessarily live in equilibrium
               models.                                                        with the natural environment. Hurricanes have become
                                                                           severe problems today because they strike man's habi-
                    By using a combination of observational informa-          tation and  development.  It is important during this
               tion  and  logic,  some  progress  has  been  made  in         period of growing population and development in the
               predicting  the level of storm-tidal surge. One  such          coastal region that man strive to live in harmony with
               method  (Bodine,  1969) is based on a hypothetical             the  hurricane,  while  at the  same  time  developing
               hurricane  with  a  central  pressure  index  frequency        safeguards to prevent loss of life and to minimize loss
               probability  of once  in  100  years  (fig.  12). This         of property.
    *          ~~~hypothetical hurricane is the Standard Project Hurri-
               cane  of the U. S. Army  Corps of Engineers, if it                  Many natural features of the coastal area tend to
               generates  maximum  surge  at  a  specific,  selected          mitigate  the  impact of hurricane flooding on man-
               location.                                                      made  structures and developments. In addition, man
                                                                           has attempted to alleviate the danger and destruction
                    Because the Gulf beaches are relatively straight          caused by the hurricane floods in a variety of ways,
               and offshore bathymetry generally uniform, estimates           most  of  which  involve  protective  structures.  It is
               of surge  elevations  are probably  significantly more         probable that man can significantly improve his safety
               accurate on the Gulf shoreline than within the highly          and can reduce storm damage by careful development

                                                                     I11-21

                                                              of building codes and construction methods. In some
                                                              areas, nevertheless, it may prove to be thoroughly
                                                              impractical for man to try to control the impact of
                                                              storm  surge. In these flood-prone areas, it may  be
                                                              more  profitable  to  avoid  a  potential  disaster by
     .........  utilizing the  areas for more  compatible  uses than
                     ~~~~~~~5 -   ~~~~~habitation.

       5 3          /      .. : :- : : iiiiiiiiiiiiiiiiil l..........               Natural Flood Protection

                                                                   In the coastal region, the first natural defense
                                                              against hurricane surge is the barrier island, which

             EXCEEDENCE  FREoUENCYt        ion
         :::-:::::-: :.: ..                                         constitutes a barrier to waves generated on the inner

                         EXCEEDENCE  FREQUENCY  PER  100 YEARS   element  which  allows  the  barrier  island to  block
                              A                                  effectively some of the storm-surge energy. The barrier
                                                              islands, however, are effective in absorbing some of
                                                              the storm's energy only if they are well stabilized by
                                                              vegetation. Along the shoreline of the bays, extensive
                    ~~~~~~20 -                                       ~~~~~marshes  and  shallow grassflats  provide a buffer or
                                                20~  _         baffle which dampens some of the erosive power and
         .. 15-                         Hi....:: ...wave  energy generated by tropical storms. Marshes,
      lO ....:....               ....           .                  lihke vegetated barrier islands, are resistant to storm
                                               -{ :::?:?::::erosion.  Elongate  oyster reefs, which grow upward
                                                              from the bay bottom to within 1 to 3 feet of the
       5-......... water surface, provide a natural baffling system that
                                                              aids  in  reducing  tidal surge and  that reduces  the
                                                              effective fetch of waves within the bays.

                                                                         Land Use and Coastal Flooding
       I............. - .....................;.;.;.
       99   95 90 80  60 40  20 10 5    1.0.5 0.1  0.01                 A number of man's activities may aggravate the
             EXCEEDENCE  FREQUENCY   PER  100 YEARS                destructive power of the storm-tidal surge and fresh-
                                                              water flooding. Any activity that destroys stabilizing
                              B                                  vegetation will weaken and subject a barrier island or a
                                                              bay shoreline to increased storm-tidal erosion. Addi-
                                                              tional hurricane washover  channels  may  develop if
      20-             a                         z                   fore-island dunes are destroyed. Navigation passes con-
      18-                     z                                    structed  through  barrier  islands  provide  additional
            F   ~16-   <      -o               >                   routes  by  which  storm-surge  tides  may  enter the
    ,I4-              z                                             restricted bays. Construction of channels, dikes, or any
                             ~,  o             b                 other modification which can serve to divert or focus
      12-  o00 YEARS                         _                     storm tides may lead to acceleration of natural shore-
      OYEAR                                           YEARS        line erosion.  Land subsidence resulting from use of
       w 8 �----------...                                           ground water exposes greater areas of the coast to the
    I 6-  0 YEARS                                                  impact of tidal surge and flooding. Modification of
       -4    5 YEARS                           - - -stream courses to provide better drainage can also lead
                                                              to accelerated erosion and, perhaps, even expose new
     v) 2-                                                          areas to stream flooding and ponding. Structures that
       O                          ..                 .cross stream courses may impede the flow of flood-
             50    100   150  200   250   300   350  400          waters; similarly, ponding may develop because runoff
                 DISTANCE A~LONG THE TEXAS COAST   (MI)
                                                              is impeded by man-made structures.
                              C
                                                                           Flood Prevention Structures
      Figlre 12. Estimation of storm-surge height and frequency,
    Texas Gulf Coast. Based on mathematical methods. After Bodine
    (1969). (A) Gulf beaches at Freeport, (B) Bay shoreline at           Under  the pressure of growing population  and
    Baytown, Galveston Bay, (C) Predicted tidal elevations (in terms  industrialization, man  has impinged  upon  more and
    of exceedence frequency) along entire open Gulf Coast.          more flood-prone areas; for example, homes and busi-
                                                              nesses are constructed within areas that have histor-

                                                        II-22

    ically flooded. Dikes, berms, levees, seawalls, groins,            The  first  effort  in this shoreline  monitoring
    and bulkheads have been constructed to protect life           program was an investigation of Matagorda Peninsula
    and property in flood-prone coastal areas.                   and the adjacent Matagorda Bay area, a cooperative
                                                               study by the Bureau of Economic Geology and the
        Every  reasonable  effort  should  be  made  to         General Land  Office of Texas. In this study, basic
    protect life and property from the threat of hurricane       techniques  of historical  monitoring  were developed
    flooding. Maximum use of premium coastal lands will           (McGowen and Brewton, 1975).
    require that more extensive flood protection structures
    be engineered and built. New and innovative methods               In 1973, the Texas Legislature appropriated funds
    of construction, along with improved building codes,         for the  Bureau  of Economic  Geology  to conduct
    should be an effective means of diminishing flood            historical monitoring of the entire 367 miles of Texas
    damage. It is important, nevertheless, to consider the       Gulf shoreline during the 1973-1975 biennium. Results
    rational limits on coastal construction aimed at flood       of tile project will be published ultimately in the form
    prevention.  More  importantly, at some  point, man          of detailed, cartographically  precise shoreline maps.
    must decide how far he can afford to go to eliminate         Work versions of these maps (scale 1:24,000) will be
    flooding in low-lying coastal areas. Areas that are          on open file at the Bureau of Economic Geology until
    repeatedly and severely flooded might best be utilized       publication. In advance of the final report and maps, a
    for activities that preclude extensive property damage       series of preliminary interim reports (e.g., Morton,
    and safety hazards.                                          1974; Morton and Pieper, 1975) is being published.

                                                                    GENERAL METHODS AND PROCEDURES
               * SHORELINE EROSION 0
                                                                                     Definition
                  GENERAL STATEMENT
                                                                    Historical Shoreline Monitoring is the documenta-
         Shorelines are in a state of erosion, accretion, or     tion of direction and magnitude of shoreline change
    equilibrium,  either naturally or artificially. Erosion      through specific time periods using accurate vintage
    produces a net loss in land, accretion produces a net        charts, maps, and aerial photographs.
    gain in land, and equilibrium conditions produce no
    net change. Shoreline changes are the response of the                            Sources of Data
    beach to a hierarchy of natural cyclic phenomena
    including (from lower to higher order) tides, storms,             Basic data used to determine changes in shoreline
    sediment supply, and relative sea-level changes. Time        position are near-vertical aerial photographs and mosaics
    periods for these cycles range from one day to several       and topographic charts. Accurate topographic charts
    thousand years. Most beach segments undergo both             dating from 1850, available through the Department of
    erosion  and  accretion  in response  to lower  order        Commerce, National Oceanic and Atmospheric Admin-
    events no matter what their long-term trends may be.         istration (NOAA),  were mapped by the U. S. Coast
    Furthermore, long-term trends can be unidirectional or       Survey using plane table procedures. Reproductions of
    cyclic; that is, shoreline changes may persist in one        originals are used to establish shoreline position (mean
    direction, either accretion or erosion, or the shoreline     high water) prior to the early 1930's. Aerial pho-
    may undergo repetitive periods of erosion and accre-         tography  supplemented  and  later replaced  regional
    tion. Shoreline erosion assumes importance along the         topographic  surveys  in the early  1930's; therefore,
    Texas Coast because of active loss of land, as well as       subsequent shoreline positions are mapped on individual
    the potential damage or destruction of piers, dwellings,     stereographic  photographs  and  aerial  photographic
    highways, and other structures.                              mosaics representing a diversity of scales and vintages.
                                                               These photographs show shoreline position based on the
          SHORELINE MONITORING PROGRAM                          sediment-water interface at the time the photographs
                                                               were taken.
         In 1972, the Bureau of Economic Geology
    initiated a program in historical monitoring for the                                Procedure
    purpose of determining, on a quantitative basis, long-
    term shoreline changes in the Texas Coastal Zone. The             The key to comparison of various data needed to
    recent acceleration in Gulf-front real estate and indus-     monitor shoreline variations is agreement in scale and
    trial  development  has  provided  the incentive  for        adjustment of the data to the projection of the selected
    adequate  evaluation of shoreline characteristics. Of        map base; U. S. Geological Survey 7.5-minute quad-
    special concern has been the documentation of those          rangle topographic maps (1:24,000 or 1 inch = 2,000
    shorelines undergoing erosion and accretion, as well as      feet) are used for this purpose. Topographic charts and
    those that are in equilibrium.                               aerial photographs are either enlarged or reduced to the

                                                           II-23

    precise scale of the topographic maps. Shorelines shown      factors, much less attempt to quantify the error they
    on  topographic  charts and  sediment-water interface        represent,'in general the accuracy of a particular survey
    mapped directly on sequential aerial photographs are         is related to its date; recent surveys are more accurate
    transferred  from  the topographic  charts and  aerial       than older surveys. Error can also be introduced by
    photographs onto the common base map mechanically            physical changes in material on which the original data
    with a reducing pantograph or optically with a Saltzman      appear.  Distortions, such as scale changes from ex-
    projector. Lines transferred to the common base map           pansion and contraction of the base material, caused by
    are compared directly and measurements are made to           reproduction and  changes in atmospheric conditions,
    quantify any changes in position with time.                   can be corrected by cartographic techniques. Location
                                                                of mean high water is also subject to error. Shalowitz
              Factors Affecting Accuracy of Data                 (1964, p. 175) states ". . . location of the high-water
                                                                line on the early surveys is within a maximum error of
         Documentation of long-term changes from avail-          10 meters and may possibly be much more accurate
    able records, referred to in this report as historical        than this."
    monitoring, involves repetitive sequential mapping of
    shoreline  position  using  coastal charts  (topographic           Aerial photographs.-Error introduced by use of
    surveys) and aerial photographs. This is in contrast to      aerial photographs is related to variation in scale and
    short-term  monitoring  which  employs beach profile         resolution, and to optical aberrations.
    measurements and/or the mapping of shoreline position
    on recent aerial photographs only. There are advantages            Use of aerial photographs of various scales intro-
    and disadvantages inherent in both techniques.               duces variations in resolution with concomitant varia-
                                                                tions in mapping precision. The sediment-water inter-
         Long-term  historical  monitoring  reveals  trends      face can be mapped with greater precision on larger
    which provide the basis for projection of future changes,    scale photographs, whereas the same boundary can be
    but the incorporation of coastal charts dating from the      delineated with less precision on smaller scale photo-
    1850's introduces some uncertainty as to the precision       graphs. Stated another way, the line delineating the
    of the data. In contrast, short-term monitoring can be        sediment-water  interface  represents  less  horizontal
    extremely precise. However, the inability to recognize       distance on larger scale photographs than a line of
    and  differentiate  long-term  trends  from  short-term       equal width delineating the same boundary on smaller
    changes is a decided disadvantage. Short-term moni-           scale photographs. Aerial photographs of a scale less
    toring also requires a network of stationary, permanent       than  that  of the  topographic  base  map  used for
    markers which are periodically reoccupied because they        compilation create an added problem of imprecision
    serve as a common  point from which future beach              because the mapped line increases in width when a
    profiles  are  made.  Such  a network  of permanent           photograph is enlarged optically to match the scale of
    markers and measurements  has not been established            the base map. In contrast, the mapped line decreases
    along the Texas Coast and even if a network was               in width when a photograph is reduced optically to
    established, it would take considerable time (20 to 30        match the scale of the base map. Furthermore, shore-
    years)  before  sufficient  data  were  available  for       lines mechanically adjusted by pantograph methods to
    determination of long-term trends.                            match the scale of the base map do not change in
                                                                width. Fortunately, photographs with a scale equal to
         Because the purpose of shoreline monitoring is to       or larger than the topographic map base can generally
    document  past changes in shoreline position and to           be utilized.
    provide basis for the projection of future changes, the
    method of long-term historical monitoring is preferred.           Optical aberration causes the margins of photo-
                                                                graphs to be somewhat distorted and shorelines mapped
                          Original Data                          on photographic margins may be a source of error in
                                                                determining shoreline position. However, only the
         Topographic   surveys.-Some   inherent  error           central portion of the photographs are used for mapping
    probably  exists in the original topographic surveys         purposes,  and  distances  between  fixed  points  are
    conducted by the U. S. Coast Survey [U. S. Coast and         adjusted to the 7.5-minute topographic base.
    Geodetic Survey, now called National Ocean Survey].
    Shalowitz  (1964, p. 81) states ". . .the degree  of              Meteorological conditions prior to and at the time
    accuracy of the early surveys depends on many factors,       of photography also have a bearing on the accuvacy of
    among which are the purpose of the survey, the scale         the documented shoreline changes. For example, devia-
    and date of the survey, the standards for survey work        tions from normal astronomical tides caused by baro-
    then  in  use,  the  relative  importance  of the area       metric  pressure,  wind  velocity  and  direction,  and
    surveyed, and the ability and care which the individual      attendant  wave  activity  may  introduce  errors, the
    surveyor brought to his task." Although it is neither        significance of which depends on the magnitude of the
    possible  nor  practical to comment  on all of these         measured  change.  Most  photographic  flights  are

                                                           11-24

    executed   during  calm  weather  conditions,  thus          and  reproduced  chart, previously  discussed,  require
    eliminating   most  of  the  effect  of  abnormal            adjustment; and (3) paucity of culture along the shore
    meteorological conditions.                                   provides limited horizontal control.

                  Interpretation of Photographs                      Aerial  photographs.-Accui~acy  of aerial photo-

         Another factor that may contribute to error in          graph mosaics is similar to topographic charts in that
    determining rates of shoreline change is the ability of      quality is related to vintage; more recent mosaics are
    the scientist to interpret correctly what he sees on the     more  accurate.  Photograph  negative quality, optical
    photographs.  The  most  qualified aerial photograph         resolution,  and  techniques  of compiling  controlled
    mappers are those who have made the most observations        mosaics  have  improved   with  time;  thus,  more
    on the ground. Some older aerial photographs may be of       adjustments are necessary when  working with older
    poor quality, especially along the shorelines. On a few      photographs.
    photographs, both the beach and swash zone are bright
    white (albedo effect) and cannot be precisely differ-             Cartographic  procedures  may  introduce  minor
    entiated; the shoreline is projected through these areas,    errors associated with the transfer of shoreline position
    and  therefore,  some  error may  be  introduced.  In        from aerial photographs and topographic charts to the
    general, these difficulties are resolved through an under-   base map. Cartographic procedures do not increase the
    standing of coastal processes and a thorough knowledge       accuracy of mapping; however, they tend to correct the
    of factors that may affect the appearance of shorelines      photogrammetric  errors  inherent  in  the  original
    on photographs.                                              materials such as distortions and optical aberrations.

         Use of mean high-water line on topographic charts
    and the sediment-water interface on aerial photographs                    Measurements and Calculated Rates
    to define the same boundary is inconsistent because
    normally the sediment-water interface falls somewhere             Actual measurements of linear distances on maps
    between high and low tide. Horizontal displacement of        can  be  made  to one-hundredth  of an  inch which
    the shoreline mapped using the sediment-water interface      corresponds to 20 feet on maps with a scale of I inch =
    is almost always seaward of the mean high-water line.        2,000 feet (1:24,000). This is more precise than the
    This displacement is dependent on the tide cycle, slope      significance of the data warrants. However, problems do
    of the beach, and wind direction when the photograph         arise when rates of change are calculated because: (1)
    was taken. The combination of factors on the Gulf            time intervals between photographic coverage are not
    shoreline which yield the greatest horizontal displace-      equal; (2) erosion or accretion is assumed constant over
    ment of the sediment-water interface from mean high          the  entire  time  period;  and  (3)  multiple  rates
    water are low tide conditions, low beach profile, and        (n 2_, where  n  represents  the number  of mapped
    strong northerly winds. Field measurements indicate          shorelines) can be obtained at any given point using
    that along the Texas Gulf Coast, maximum horizontal          various combinations of lines.
    displacement of a photographed shoreline from mean
    high-water level is approximately 125 feet under these            The beach area is dynamic and changes of varying
    same  conditions.  Because  the displacement of the          magnitude occur continuously. Each photograph rep-
    photographed shoreline is almost always seaward of           resents a sample in the continuum of shoreline changes
    mean high water, shoreline changes determined from           and it follows that measurements of shoreline changes
    comparison of mean high-water line and sediment-water        taken over short time intervals would  more closely
    interface will slightly underestimate rates of erosion or    approximate the continuum  of changes because the
    slightly overestimate rates of accretion.                    procedure  would  approach  continuous  monitoring.
                                                                Thus, the problems listed above are interrelated, and
                     Cartographic Procedure                     solutions require the averaging of rates of change for
                                                               discrete intervals. Numerical ranges and graphic displays
         Topographic charts.-The topographic charts are          are used to present the calculated rates of shoreline
    replete with a 1-minute-interval grid; transfer of the       change.
    shoreline position from topographic charts to the base
    map  is accomplished by construction of a 1-minute-               Where possible, dates when individual photographs
    interval grid on the 7.5-minute topographic base map         actually were taken are used to determine the time
    and projection of the chart onto the base map. Routine       interval needed  to calculate  rates, rather than  the
    adjustments are made across the map with the aid of the      general date printed on the mosaic. Particular attention
    1-minute-interval latitude and longitude cells. This is    is also paid to the month, as Well as year of pho-
    necessary because: (1) chart scale is larger than base       tography; this eliminates an apparent age difference of
    map scale; (2) distortions (expansion and contraction)       one year between photographs taken in December and
    in the medium (paper or cloth) of the original survey        January of the following year.

                                                           II- 25

           Justification of Method and Limitations               precise, -represents  the  best  method  available  for
                                                                investigating long-term trends in shoreline changes.
         The methods used in long-term historical moni-
    toring carry a degree of imprecision, and trends and
    rates of shoreline changes determined from these tech-              Limitations of the method require that emphasis
    niques have limitations. Rates of change are to some          be placed first on tr-end of shoreline changes with rates
    degree subordinate in accuracy to trends or direction of      of change being secondary. Although rates of change
    change; however, there is no doubt about the signif-          from map measurements can be calculated to a precision
    icance of the trends of shoreline change documented           well beyond the limits of accuracy of the procedure,
    over more  than 100 years. An  important factor in            they are most important as relative values; that is, do
    evaluating shoreline changes is the total length of time      the data indicate that erosion is occurring at a few feet
    represented by observational data. Observations over a        per  year  or  at  significantly  higher  rates. Because
    short period of time may produce erroneous conclusions        sequential shoreline positions are seldom exactly par-
    about the long-term change in coastal morphology. For         allel, in some instances it is best to provide a range of
    example, it is well established that landward retreat of      values such as 10 to 15 feet per year. As long as users
    the shoreline during a storm is accompanied by sedi-          realize and understand the limitations of the method of
    ment removal; the sediment is eroded, transported, and        historical  monitoring,  results of sequential shoreline
    temporarily  stored  offshore.  Shortly  after  storm         mapping  are significant and  useful in coastal zone
    passage,  the normal  beach  processes again  become          planning and development.
    operative and some of the sediment is returned to the
    beach. If the shoreline is monitored during this recovery           RESULTS OF HISTORICAL MONITORING
    period, data would indicate beach accretion; however, if                             PROGRAM
    the beach does not accrete to its prestorm position, then
    net effect of the storm is beach erosion. Therefore,                           Gulf Shoreline Erosion
    long-term trends are superior to short-term observations.
    Establishment of long-term trends based on changes in              Long-term  erosion  during  the  past 74 to 132
    shoreline position necessitates the use of older and less     years (table 1) has subjected 47 linear miles, or 13
    precise topographic surveys. The applicability of topo-       percent, of the Texas Gulf shoreline to severe erosion
    graphic  surveys  for these  purposes  is discussed by        and shoreline retreat (greater than 10 ft per year); 154
    Shalowitz (1964, p. 79) who stated:                           linear miles, representing 42 percent of the Texas Gulf
                                                                 shoreline, similarly has been affected by moderate
                "There is probably little doubt but that          long-term erosion and shoreline retreat (up to 10 ft
            the earliest records of changes in our coastline      per year). Long-term accretion has occurred along 35
            that are on a large enough  scale and in              percent of the Texas Gulf shoreline; 10 percent of the
           sufficient detail to justify their use for quan-Gufcatiehsbninlg-rmqiiru.
            titative study are those made by the CoastGufcatiehsbninlg-rmqiiru.
           Survey. These surveys were executed by
           competent and careful engineers and were                    Short-term erosion during the past 7 to 23 years
           practically all based on a geodetic network            has subjected 153 linear miles, or 42 percent, of the
           which minimized the possibility of large errors        Texas Gulf shoreline to severe erosion and shoreline
           being introduced. They therefore represent the        retreat (greater than 10 ft per year); similarly 101
           best evidence available of the condition of ourliermesrpeenng2prctofheTxsGf
           coastline a hundred or more years ago, and theliermlsrpeenng2prctofheTxsGf
           courts  have  repeatedly  recognized  their            shoreline, has been affected by moderate short-term
           competency in this respect             ....erosion and shoreline retreat (up to 10 ft per year).
                                                                 Only 13 percent of the Texas Gulf shoreline is under-
         Because of the importance of documenting changes         going short-term  accretion,  while  17  percent is in
    over a long time interval, topographic charts and aerial      short-term equilibrium.
    photographs have been used to study beach erosion in               TeGl   hrlna   rvosycasfei
    oHarri andJoeas. For 9eampl, Morga  and Larimore (1968),      composed of deltaic headlands, peninsulas, and barrier
    Branti  and Mcones   (1973), E-s     and Wtanles (1973),h    v islands.  Areas  undergoing  shoreline  erosion  can  be
                   Bryat ad Mcann(197),  nd Sapo  (193)  ave     related  to  this  physiographic  classification  on  a
    successfully used techniques similar to those employed        regional  scale. Deltaic headlands are comprised pre-
    herein. Previous articles describing determinations of        dominantly of mud with relatively low percentages of
    beach changes from aerial photographs were reviewed           sand, a factor that contributes to high rates of severe
    by Stafford (1971) and Stafford and others (1973).            shoreline  erosion.  Eroded  mud  is carried  seaward
                                                                 where it is deposited and, hence, removed from the
                                                                 sediment supply system. Brazos Island and south Padre
         Simply stated, the method of using topographic           Island of the Rio Grande delta (Brownsville-Harlingen
    charts and aerial photographs, though not absolutely          map) and the beach between San Luis Pass and Brown

                                                          11-26

    Cedar Cut of the Brazos-Colorado delta (Port Lavaca            Bays (Corpus Christi map), and Baffin Bay (Kingsville
    map) are Holocene deltaic headlands. The Gulf shore            map),  as  well  as  in  Laguna  Madre  (Brownsville-
    from  Sabine  Pass to  Rollover  Pass (Beaumont-Port           Harlingen  map). Similarly, northerly winds generate
    Arthur  map)  is developed  on a relict (Pleistocene)          waves that strike and erode southern and southwestern
    deltaic headland overlain by Modern marsh and strand-          shoreline  segments  in  Galveston,  Matagorda,  San
    plain sediments. Bolivar Peninsula (Galveston-Houston          Antonio, Corpus Christi, and Baffin Bays. Bay shore-
    map)  and  Matagorda  Peninsula  (Bay  City-Freeport           line erosion along Matagorda, St. Joseph, and Mustang
    map) are also undergoing erosion as a result of their          Islands  and  Matagorda  Peninsula  is also caused by
    close  association  with   the  sand-deficient  deltaic        waves and currents generated by northerly winds. Sand
    headlands.                                                     eroded from  bay shorelines is deposited within the
                                                                 bay; some mud derived from shorelines may reach the
         Barrier islands of the Texas Coast, which include         Gulf, but much of it gradually fills the bay.
    Galveston, Matagorda, St. Joseph, Mustang, and north
    and central Padre Islands (Galveston-Houston, Bay
    City-Freeport,   Port  Lavaca,   Corpus  Christi,  andFATRAFEINSHELECAGS
    Kingsville maps, respectively) are elongate bodies ofFATR AFE IN SH EL ECAGS
    fine-grained sand from 20 to 60 feet thick. Rates of                Studies indicate that shoreline changes along the
    shoreline  erosion  along  barrier islands are generally       Texas  Gulf  Coast  are  largely  the result of natural
    lower because of the increased availability of sand.           processes, although in some instances the changes may
    Apparently, the shoreline along central Padre Island           have  been aggravated by human  activities. Geologic
    (Kingsville  map)  is relatively stable because sand is        processes and, more specifically, coastal processes are
    supp lied to this segment of the coast by longshore            complex  dynamic components of large-scale systems.
    currents that converge in the general vicinity of 27           Coastal  processes  are dependent  upon  the intricate
    degrees North latitude (Lohse, 1955). Although con-            interaction of a large number of natural variables such
    siderable sand is removed from the beach by eolian             as wind velocity and duration, fetch, rainfall, storm
    processes along central Padre Island, sufficient sedi-         frequency and intensity, tidal range and characteristics,
    ment  to replenish  the losses is transported  by net          and littoral currents. It is difficult, therefore, if not
    longshore  currents  flowing  northward   from  the            impossible,  to isolate at this time  all the  specific
    southern  part of the coast and southwestward  from            factors causing shoreline changes.
    the upper part of the coast.

                    Bay Shoreline Erosion                                                  Climate

         Of the 1,100 miles of bay and estuarine shore-                 Climatic changes during the 18,000 years since
    line,  408  linear miles or  37  percent  of the  total        the end of the Pleistocene ice age have been docu-
    bay-estuarine shoreline is undergoing varying rates of         mented  by various methods.  In general, air temper-
    shoreline erosion  (table 1). At  present, research on         ature was lower and precipitation was greater at the
    precise rates of bay-shore erosion has not been com-           end of the Pleistocene than at the present; the warmer
    pleted; bay shorelines undergoing erosion have been            and drier conditions, which now prevail, affect other
    interpreted  qualitatively.  Bay  shoreline  erosion  is       factors such as vegetal cover, runoff, sediment concen-
    related principally to the dominant wind regimes of            tration,  and  sediment  yield.  Observations based on
    the region, but hurricanes and tropical storms may             geologic maps  prepared by the Bureau of Economic
    inflict bay  shores  with  severe  erosion  during brief       Geology ("Environmental Geologic Atlas of the Texas
    periods of landfall.                                           Coastal Zone")  confirm that many  rivers along the
                                                                 Texas coastal plain were larger and probably trans-
                                                                 ported greater volumes of sediment thousands of years
         Southeasterly winds persist throughout the spring,        ago  (early  Holocene).  This,  in  turn,  affected  the
    summer, and fall months, whereas northerly winds of            sediment  budget  of the  Texas  Coast  by supplying
    less duration but greater strength persist during the          additional sediment to the littoral drift system.
    winter months. Wind strength and duration, fetch,
    depth of water, and orientation of bay shorelines are                Severe  droughts  that  occur  periodically  are a
    some of the important factors controlling bay shore-           potential,  though  indirect,  factor  related  to  minor
    fine erosion. In areas where fetch is measured in miles,       shoreline changes because of the adverse effect of low
    the southwesterly winds generate waves and currents            rainfall on vegetation. Because dunes and beach sand
    that  impinge  and  erode  shoreline  segments  along          are stabilized by vegetation, sparse vegetation resulting
    northwestern bay margins; examples occur in Trinity            from droughts offers less resistance to wave attack.
    and   Galveston   Bays   (Galveston-Houston   map),             Regional  variations in rainfall and  wind dominance
    Matagorda Bay (Bay City-Freeport map), San Antonio             along   the  Texas   Coast   also  must  exert  some
    Bay  (Port Lavaca map), Aransas and Corpus Christi             differential effect on shoreline stability.

                                                           11-27

               Storm Frequency and Intensity                          Whether  the  beach  returns  to  its  prestorm
                                                                position depends primarily on the amount of sand
        The frequency of tropical cyclones is dependent         available. If net sand is lost, the beach profile will not
    on cyclic fluctuations in temperature; increased fre-        reestablish itself at the prestorm position; thus, net
    quency of hurricanes occurs during warm cycles (Dunn          shoreline erosion or retreat has occurred. The beach
    and Miller, 1964). Because of their frequent occur-           profile readjusts to normal prestorm conditions much
    rence,  devastating  force,  and  catastrophic  nature,       more rapidly than does the vegetation line. Generally
    tropical cyclones have received considerable attention        speaking, the sequence of events is as follows: (1)
    in recent  years.  The  significance of hurricanes as         return of sand to beach and profile adjustment (accre-
    geologic agents was emphasized by Hayes (1967) who            tion), (2) development of low sand mounds (coppice
    concluded that most of the Texas coastline experi-            mounds) seaward of the foredunes or vegetation line,
    enced the passage of at least one hurricane eye during        (3) merging of coppice mounds with foredunes, and
    this century. The general nature of tropical storms and       (4) migration of vegetation line to prestorm position.
    hurricanes,  as well  as their relationship  to  flood       The first step is initiated within days after passage of
    hazard, has been described in this report. The specific      the storm and adjustment is normally attained within
    relationship  between  these  storms  and  shoreline         several weeks or a few months. The remaining steps
    stability in Texas also is important in understanding        require  months  or  possibly  years  and,  in  some
    the nature of rapid changes in shorelines.                   instances, complete recovery is never attained.
         As previously described, high-velocity winds with
    attendant  waves  and  currents  of destructive  force              Local and Worldwide Sea-Level Conditions
    attendant waves and currents of destructive force
    scour and transport large quantities of sand during
    hurricane approach and landfall (fig. 7). The amount              Two  factors of major importance relevant to
    of damage suffered by the beach and adjoining areas          land-sea relationships are sea-level changes and compac-
    of damage suffered by the beach and adjoining areastinlsbdec.Spad190)icuedHoee
    depends on a number of factors including angle of            tional subsidence. Shepard (1960b) discussed Holocene
    storm approach, configuration of the shoreline, shape or post ice-age (Pleistocene) rise in sea level along the
    and  slope of Gulf bottom,  wind velocity, forward           Texas Coast based on C14 age determinations. During
    speed of the storm, distance from the eye, stage of          historical time, relative sea-level changes are deduced
    astronomical  tide, decrease in atmospheric pressure,        by geodetic engineers  who monitor mean sea level
    and  longevity  of the storm. Beach  profiles adjust         using tide observations to develop trends based on
    themselves to changing conditions in an attempt to           long-term measurements. This method, however, does
    maintain a profile of equilibrium; shorelines experience     not distinguish between sea-level rise and land-surface
    their  greatest short-term  changes  during and after        subsidence. A minor vertical rise in sea level relative to
    storms. Storm surge and wave action commonly plane           adjacent land in low-lying coastal areas causes a con-
    off preexisting topographic features and produce a           siderable horizontal,  landward  displacement of the
    featureless, uniformly seaward-sloping beach. Eroded         shoreline.
    dunes, wave-cut steps, and washover fans are common
    products of the surge; the sand removed by erosion is             Shepard and Moore (1960) speculated that coast-
    (1) transported and stored temporarily in an offshore        wise  subsidence  was  probably  an  ongoing  process
    bar, (2) transported in the direction of littoral drift,     augmented by sediment compaction. More recent data
    and/or (3) washed across the barrier island through          tend to support the idea that natural land subsidence
    hurricane channels. Sediment transported offshore and        is occurring  along the Texas Coast (Swanson  and
    stored in the nearshore zone is eventually returned to       Thurlow, 1973).
    the beach by bar migration under the influence of
    normal post-storm wave action. The processes involved
    in beach recovery are discussed by Hayes (1967) and                             Sediment Budget
    McGowen and others (1970).
                    ~McGowen and others (1970).                       Sediment budget refers to the amount of sedi-
         Foredunes  are  an  important  line of defense          ment in the coastal system and the balance among
    against wave  attack and, thus, afford considerable          quantity of material introduced, temporarily stored, or
    protection  against  hurricane  surge  and  washover.        removed from the system. Beaches are nourished and
    Dunes also serve as a reserve of sediment from which         maintained  by  sand-size  sediment  contributed  by
    the beach can recover after a storm. Sand that is            major streams, updrift shoreline erosion, and onshore
    removed from the dunes and beach, transported off-           movement of shelf sand by wave action. Sand losses
    shore, and returned to the beach, provides the material      are attributed to (1) transportation offshore into deep
    from which small coppice mounds and eventually the           water, (2) accretion along and against natural littoral
    large   fore-island  dunes  rebuild.  Dune  removal,         barriers and man-made structures, (3) deposition in
    therefore,  eliminates sediment  reserve, as well as a       tidal  deltas  and  hurricane  washover  fans,  (4)
    natural  defense  mechanism  established  for  beach         excavation for construction purposes, and (5) eolian
    protection.                                                  processes.

                                                         II-28

         Sediment  supplied  by  major  streams  is trans-         (3)  excavation  of  sand  from  barrier  islands  and
    ported along the shore by littoral currents. The Brazos        peninsulas,  (4) construction  of  dams  on  the  Rio
    River, Colorado River, and Rio Grande are the only             Grande  and  Brazos  River,  and  (5) artificial main-
    major Texas rivers that debouch directly into the Gulf         tenance  of the  current  position  of the  Mississippi
    of Mexico, but discharge data indicate that these rivers       River.
    currently contribute very little sediment to the littoral
    drift  system.  The  Mississippi  River was  a possible          LONG-TERM TRENDS IN SHORELINE POSITION
    source of beach sediment prior to its shift to the
    eastern part of the delta about 400 years ago.                      Shore erosion is not only a problem along United
                                                                States coasts but also is a problem worldwide. Even
         Van   Andel  and  Poole  (1960)  and  Shepard             though some local conditions may  aggravate erosion,
    (1960a) suggested that sediments of the Texas Coast            major factors affecting shoreline changes are sea-level
    are largely of local origin. Sands derived from pre-           variation,  including  compactional  subsidence,  and  a
    viously deposited sediment on the floor of the conti-          deficit in sediment supply. A deficit in sand supply
    nental shelf were apparently reworked and transported          may be related to climatic changes, human activities,
    shoreward  by  wave  action  during  the  post  ice-age        and the exhaustion of the shelf supply through sub-
    (Holocene) sea-level rise. McGowen and others (1972)           sequent burial of shelf sand by finer sediments to a
    also concluded that the primary source of sediment             depth below wave scour.
    for Modern sand-rich barrier islands, such as Galveston,
    Matagorda,   and   St.  Joseph   Islands,  was   local               A  logical conclusion  that can  be drawn  from
    Pleistocene and early Holocene sources on the adjacent         available information  is that shoreline position will
    inner shelf.                                                   continue to change, and landward retreat (erosion) will
                                                                 be the long-term trend. The combined influence of
           FACTORS AGGRAVATING EROSION                            interrupted  and  decreased  sediment  supply, relative
                                                                 sea-level rise, and tropical cyclones is insurmountable
         Shoreline changes induced by man are difficult to         except in very local areas such as river mouths. There
    quantify because human activities promote alterations          is no evidence to suggest that a long-term reversal may
    and imbalances in the sediment budget of the Coastal           occur in the foreseeable future to change the present
    Zone. Furthermore, ground-water withdrawal increases           trends of shoreline change.
    land subsidence. Construction of dams, erection of
    seawalls, groins, and jetties, artificial stabilization of                   POTENTIAL MITIGATION
    the Mississippi  River,  and removal of sediment for                         OF SHORELINE EROSION
    building purposes all contribute to changes in quantity
    and  type of beach material delivered to the Texas                  The best defense against the hazard of shoreline
    Coast. Even such minor activities as vehicular traffic         erosion is recognition and subsequent adjustment in
    and  beach  scraping  can  contribute  to the  overall         land  use.  Other  alternatives  include artificial beach
    changes,  although  they  are  in no  way  controlling         nourishment   or  artificial  stabilization  by   dune
    factors.  Erection  of impermeable structures and re-          vegetation and structures.
    moval of sediment have an immediate, as well as a
    long-term  effect, whereas a lag of several to many                 It should be noted, however, that dune stabiliza-
    years may be required to evaluate fully the effect of          tion, while appearing to be environmentally sound, can
    other changes such as river control, dam construction,         be counterproductive and may have a definite impact
    and subsurface fluid withdrawal.                               on  beach  steepness  and  erosion.  This  was  demon-
                       Jett costrutio alog te Teas oastwasstrated  on  the North Carolina coastline where veg-
    initiated in the late 1800's. These projects serve to          etae ue eitdsomwv taks elta
    alter natural processes such as inlet siltation, beach         the normal exchange of sand between the dunes and
                   eroion an huricne urg. Teireffct n soreinebeach was eliminated; increased beach steepness and
    changes is subject to debate, but it is an obvious fact   b ueac erosion resltd fromdhsefortosaiiey  1973)
    that impermeable structures interrupt littoral drift, and    dns( oa                  n    ofe,17)
    impoundment of sand occurs at the expense of beach                  The  shoreline  in Texas  could  be stabilized at
    nourishment  downdrift  of the structure. It appears           enormous  expense  by  a solid structure  such  as a
    reasonable to expect that any sand trapped by the              seawall. Any beach seaward of such a structure would
    jetties  is  compensated  for  by  removal  of  sand           eventually be removed unless maintained artificially by
    downdrift, thus increasing local erosion problems.             sand nourishment (a costly and sometimes ineffective
                                                                 practice). The U. S. Army Corps of Engineers (1971b,
         Factors which have contributed to the deficit in          p. 33) stated: "While seawalls may protect the upland,
    sediment budget include: (1) removal of sand from the          they do not hold or protect the beach which is the
    fore-island dunes, (2) dredging of sand from the Gulf,         greatest asset of shorefront property." Moreover, con-

                                                          II-29

    struction  of a single structure may  trigger a chain              The extent and amount of subsidence are well
    reaction  that will require additional structures and         defined  and  known  through  a series of elevation
    maintenance.                                                 benchmarks established and resurveyed or leveled at
                                                              selected intervals by the National Geodetic Survey
        When  development plans are being formulated,           (formerly the U. S.'Coast and Geodetic Survey) of the
    careful consideration must be given to the evidence          Department of Commerce. The first leveling program
    that shoreline erosion  will continue  into the fore-        was a first-order line from Smithville to Galveston
    seeable  future.  While  beach-front  property  may          surveyed in 1905 and 1906. In 1918, a first-order line
    demand the highest prices, it may also carry with it          was established from Sinton, Texas, to New Orleans,
    the greatest risks.                                          Louisiana. During the period between 1932 and 1936,
                                                              several other first- and second-order lines were estab-
           S  LAND-SURFACE SUBSIDENCE  0                         lished, and the two original lines were releveled. In
                                                              1942 and 1943, a large number of second-order lines
                  GENERAL STATEMENT                             were  established and  most of the older lines were
                                                              releveled.  Following  the  leveling  program  of
         Land-surface subsidence, primarily a consequence        1942-1943, subsidence in the Houston area was first
    of ground-water pumping and withdrawal that began            documented.  Subsequently,  releveling  surveys  were
    in the Texas Coastal Zone in the early part of this          completed  in  1951, 1953-54, 1958-59, 1964, and
    century, affects to varying degrees a substantial part of    1973. These surveys clearly establish the extent and
    the lower Texas coastal plain. Most serious subsidence       amount of subsidence in the lower Texas coastal plain.
    is in the Greater Houston area, where some localities
    show recorded subsidence up to 8.5 feet (Galveston-
    Houston  map).  Significantly, both the rate of land               Likewise, the cause of subsidence is well docu-
    subsidence,  in terms of lost land elevation, and the         mented, primarily through the extensive monitoring of
    area of impact are progressively increasing and have          water-well levels, which was started in 1929 by the
    increased dramatically in the past two decades (fig.          Water  Resources  Division of the U.  S. Geological
    13).                                                         Survey. Comparison of areas of water level and piezo-
                                                               metric decline with areas of land-surface subsidence
                                                               clearly shows that they are coextensive. Results of
                                                               monitoring by the U. S. Geological Survey have been
       o                                                         reported in several papers; refer especially to those
       0_
                                                              reports  by  Gabrysch  (1969, 1972), Gabrysch and
                                                              McAdoo (1972), and Gabrysch and Bonnet (1974) as
                                                               well as to reports by Marshall (1973) and Turner,
       0
                                                              Collie, and Braden, Inc. (1966). Portions of this
                                                              section  of the atlas have' been  drawn  from  these
                                                               previously published reports.
     _- o
       UJ
                                                                   Although  the principal  cause of subsidence  is
                                                              ground-water  withdrawal,  a minor amount  of sub-
    00  O_                                                       sidence  can  be  attributed to natural  compactional
                                                              subsidence, to tectonic subsidence, and locally, to the
                                                              withdrawal of oil, salt, and sulfur. Subsidence resulting
    W                                       O                    from mineral extraction has been restricted largely to
     < 0                                                         areas of production on and adjacent to certain coastal
                                                              salt domes. More than 3 feet of subsidence at the
                                                              Goose Creek oil field was caused by oil production,
                                                              resulting chiefly from poor production practice in the
                                                              early history of the field (Pratt and Johnson, 1926).

          I       --I-~    I        ,        ,        I              While  the extent, amount, and mechanisms of
          o')     o o      0        0        0        0          land-surface subsidence are well documented, methods
                                                              for mitigating the problem, short of massive curtail-
                                                              ment of ground-water pumping, are not evident. Varia-
      Figure 13. Area in the Texas Coastal Zone impacted by      tiof  indte pumposition ot   ev ident. as
    land-surface subsidence in excess of I foot between 1943 and  tions  in hydrologic                   behavior, s
                  1973.  Values  are  cumulative. ~well as local difference in hydrologic behavior, suggest
    1973. Values are cumulative.
                                                              that certain areas are more prone to subsidence than
                                                              are others.

                                                         11-30

    CAUSE AND MECHANISMS OF LAND SUBSIDENCE                            The  amount  of subsidence  that  will occur  is
                                                                directly related to the decline in piezometric level,
        Most  of  the  ground-water  production  in  the         which is a function of the volume of water withdrawn
    Texas coastal plain is from aquifers occurring from           from the aquifer. The amount of subsidence, however,
    near the surface to depths as great as 3,000 feet. The        will vary further depending upon the amount of clay
    geologic formations involved are composed of varying          within the aquifer section, the vertical distribution of
    amounts of alternating sands (the aquifers) and inter-        the clay, the compressibility of the clay, and  finally,
    stratified  clays.  Significantly,  the  clays  are  water    the degree  of undercompaction  of the  clay  in its
    saturated and undercompacted; clays nearer the sur-           natural state. The amount of clay in the aquifer and
    face  are  commonly  less compacted  than  those at           the number of clay beds within the aquifer sands, as
    greater depths. The aquifer sands and interbedded
    clays dip gently toward the coast; they crop out in a
    general coastwise-trending belt extending from about                  eP                    . o          P Susienh
                                                                   ,o,,10, Wner-     ln crese  in inter-   S b ie cm
    30 to 50 miles inland from the coastline. It is in the         groruor pr......    grasuror pressure
    zone of outcrop that the aquifers are recharged by                            r        ....
    infiltration of fresh water. Principal water production                                 stages
    is  from   the   Lagarto  and   Goliad  Formations                 T/               .......
    (Evangeline Aquifer), and from the Willis, Lissie, and                 s[ad
    Beaumont   Formations   (comprising  the  Chicot'.--
    Aquifer). Earlier authors referred to these two aquifers
    simply as the Principal Aquifer. Similarly, in certain                           (
    areas of the northeast part of the Coastal Zone, sands                /,~----                  o
    above the Principal Aquifer were referred to as the
    Alta Loma sands or the Alta Loma Aquifer.                                         /      __

         Prior  to  1900,  before  heavy  pumping  com-
    menced, water wells in the artesian aquifers flowed
    naturally; that is, the aquifers were under sufficient
    pressure  to force water to the land surface within             Figure 16. Effects of ground-water withdrawal on intergranular
    open wells. Subsequent pumping, especially in the past        pressure, with  consequent  volume  reductions  and  surface
    three decades, has resulted in a continuing decline in        subsidence. After Turner, Collie, and Braden, Inc. (1966).
    artesian pressure or piezometric surface over wider and
    wider areas. Geologists and engineers of the U. S.
    Geological Survey, who started monitoring water levels        well as the compressibility of the beds, vary areally;
    in  coastal  plain  wells  in  1929,  have  charted the       certain  areas  are  more  prone  to  subsidence  than
    long-term  decline  in the  pressure  levels. In  1943,       others, even with the same amount of ground-water
    maximum  decline of the water level was about 150             withdrawal  and  comparable  levels  of  piezometric
    feet; by 1954, the piezometric level had dropped to           decline.
    about 300 feet; by 1964, it had declined to about 350
    feet; and in 1974, it locally has declined to 400 feet.            Compaction of the clays and resulting subsidence
    Comparison of areas of pressure-level decline and areas       are nearly 100 percent irreversible (a small rebound
    of subsidence show clearly their coextensive nature           may be possible). Further, additional subsidence may
    (figs. 14, 15).                                               occur even if ground-water withdrawal is reduced and
                                                                the decline in piezometric levels is arrested. This is
         The   water-saturated  clays  that  occur  inter-        because of a lag between the addition of the load and
    stratified with the aquifer sands are compressible and        ultimate compaction  of the clays. Computations by
    become compacted when subjected to increased load.            Marshall (1973) indicated that additional subsidence
    This reduction in volume of the compressible clays is         after water-level  decline  ceases will be at least 50
    translated to surface subsidence. Reduction in artesian       percent and possibly as much as 150 percent of the
    pressure  from  pumping  causes  a  loss  of buoyant          subsidence experienced prior to that time. Gabrysch
    support to the granular structure of the aquifer sands        and Bonnet (1974) state that only 15 to 20 percent of
    (decreased pore pressure), and each layer is, therefore,      additional subsidence will occur. R. 0. Kehle (personal
    subjected  to  a  corresponding  increase  in effective       communication,  1974), however, suggests that sub-
    vertical pressure. This decreased pore-pressure effect is     sidence may stop immediately if piezometric decline is
    immediately transferred to the contact surface with           arrested. Variation in the percentage of eventual sub-
    interbedded  clays, but, because  of the low perme-           sidence, even after arrest of piezometric decline, is also
    ability of the clays, the clays drain more slowly (fig.       a function of the amount and nature of clays occur-
    16). The clay layers compress vertically and become           ring within and associated with the aquifer. Eventual
    thinner; consequently, the overlying sediments and the        subsidence,  therefore,  should  be  variable  and  will
    ground surface subside.                                       depend on the geologic nature of the aquifer.

                                                            11-31

                                                                           -   DECLINE iNJ PRINCIPAL AQ1UIFERf
                                                     \J                      --- ~~~~~DECLINE IN ALTA LOMA SAND        ,j

                                          A~i                                       I

                                        .. . . /   -       4.                                            .

                                                       "005.0CC   V  7 - -
                                                                        7~~~I  ii  a

                                                                                                             "j"~~~1"
                  r�,�.�.~~~~~~-~~--~k' i                                     C,-.�                  I IC
                                                   N,.�~r? C-C--

                              ~~~~~~~`�~~~~~~~~~~i~                                                           a~ Ce $

                        * 1  Scale in RiPe            C      /In                                        Scale in Miles \          0C

     LAND SUBSIDENCE (FT I C~  *CiCCCCCC. Aa~l                        I          ZOMETRIC DECLINE (FT   CSCCCO                     fC\C
                     C~~~~~~~~~~~~~~~~~~~~a A9614
                                                                       S                                              NELN  NPlCPLAIIE
                              C -    OCCCCCOCCCN  I    ~~---ECINEN~TALM'>N
                                              i.                                                                                 ,,,.,,_,,,,,iF
                                           /d

           b:~~~~~~~~~~~C   (          C                                                                CCC
                                                                                   8\~~~~~~~~\CQ <7CC,-i
                                                                4  I        CC                               '0~~~~~~~~~~~~1

                                                                           'Ci~~~~~~'

                                           s .   Y�.�-           P                                   -i          TB~~~ 5. 1906-195

                                                               t~~~~~~~~~~~~~~~~~~~~~~~                               CC

                                                                             I                                                    I~~~~~~~~~~~~~~~~~~
                                             CC: COCO   C .                                                                              r CC
              i,~~~~~~~~~~~~~~~~~~~1                                                                                                            C

                                                                     I                            NCCIN PRNIA  /(UIE

                                                         ���~~~~~~~~~~~~~~~~~~~~~~~~7   C/I���'
                                                                          �~~~~~~~~~~~~~~~~~~~~~~~~A  /C."

                                        7-~ ~                           ~                ~~~~~~~~~~~ O ~~zV~ ,JC\
                                   9                   >           c i                                                                         CC�

           LAD UBIENE    C    Scale in Mile                                       ZMTI  ELN  F I    OScCCC CC Mlp                        'C

                                                                    C1906-1964
      Figure 14. Land-surface subsidence and decline of piezometric (ground water) surface within Principal and Alta Loma Aquifers,
    1906-1963, Greater Houston area, Modified after Marshall (1973).

                                                                    II 32

                                               * '/ ' ,-~  I  ,   ------ DECLINE IN CHICOT AQUIFER
                    "I :   '               '       ,'~                DECLINE IN EVANGELINE AQUIFER

                                                                                                          4-A
                       I~ ,,\                                               4        /;

               > ~     ~       ~        I                            '                -    >',.,  9'',
                                            -~~~~~~> ,,_                                       ,      "     -
                 (-.  ,   -tb' 'K ,. .t :-.   ,-:4'-  /
                           /     '~~~i44   f,-,,/ ,--

                                                              ~,"~~~~~~~~~~~~~~~~~~~~~~~7
                                              N-,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-4

                                         .~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ... ....
                                        'C>   I'x,.  ~.~?, .'/'   II           ' -              ,.~.~, "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.,-141
                .............. I :-' .... '  ?                         . ..........  "'

                 EXETO AN                U S D N C                ByCtyFepr,   avso-Hutn n
                                           (I                          -.4,44,44444,'.~ ~ ~ ~ ~ ~ ~  ~ ~ ~ ~~~~~" 7
     LAND SUBSIDENCE (FT  I                                      PIEZOMETRIC DECLINE (FT )SacMc

                                                             1943 1973
      Figure 15. Land-surface subsidence and decline of piezomnetric (ground-water) surface within Evangeline and Chicot Aquifers,
    1943-1973, Greater Houston area. After Gabrysch and Bonnet (1974).

              EXTENT OF LAND SUBSIDENCE                          (Bay   City-Freeport,   Galveston-Houston,   and
                                                                   Beaumont-Port Arthur maps); this zone includes the
         Land subsidence, both in amount of land eleva-          critically impacted Greater Houston area; (2) a large
    tion  lost and  in area affected, has been increasing        part of Jackson County (Port Lavaca and Bay City-
    significantly during the past three decades. Coincident      Freeport maps); and (3) an area in Nueces and San
    with accelerating subsidence have been increases in the      Patricio Counties  centered  near the community  of
    volume of water withdrawn and decline of artesian            Odem  (Corpus Christi map). Maximum subsidence in
    pressure levels. In 1943, when releveling recorded the       the Corpus Christi area is in excess of I foot, with the
    first measurable subsidence, a little more than 140          distribution   of  subsidence  showing  a  pattern
    square  miles  of land  in  the  Houston  region  had        remarkably  similar to that of the Houston area in
    subsided I foot or more, with maximum subsidence of          1943.
    about 1.5 feet. By 1954, about 1,000 square miles of
    land had experienced subsidence in excess of I foot,
    with maximum subsidence up to 4 feet. In 1964, more               Subsidence values shown on the Natural Hazards
    than 1,800 square miles of land had subsided more            Maps were calculated with data derived from various
    than I foot, with maximum subsidence up to 6 feet.           releveling surveys conducted by the National Geodetic
    By 1974, more than 3,000 square miles of land on the         Survey. Periodic releveling data are limited; therefore,
    lower Texas coastal plain had undergone more than a          the boundaries between subsidence zones are approx-
    foot  of  subsidence,  and  maximum  subsidence  had         imate. Three subsidence zones, (1) 0.2 foot to I foot,
    reached 8.5 feet (Galveston-Houston map). The area of        (2) 1 foot to 5 feet, and (3) greater than 5 feet, are
    lands impacted by subsidence of 1 foot or more has           based on maximum recorded subsidence for any par-
    doubled approximately each decade for the past 30            ticular benchmark or level station. In some areas, the
    years. At the present time, about 230 square miles of        "total"  amount  of subsidence has been determined
    land, centering on Pasadena, has subsided more than 5        from elevation differences recorded at a benchmark
    feet.                                                        for relatively short periods of time (for example, 1951
                                                                   to 1973); in other areas with more data, the measured
         Measurable subsidence, defined herein as 0.2 foot       subsidence includes elevation differences recorded for
    and  greater, now  impacts three areas of the lower          longer periods of time (for example, 1905-1973). This
    Texas coastal plain: (1) an extensive area of the upper      approach of using net or maximum elevation variation
    Texas coastal plain extending from Bay City north-           at each  benchmark  provides  a  map  that displays
    ward into Louisiana and inland as much as 60 miles           maximum recorded subsidence.

                                                             II-33

         Land subsidence is minimal in the zone of
    0.2-foot to 1.0-foot subsidence and has progressed
    substantially in the zone defined by subsidence in the
    range  of  1  foot  to  5  feet.  Within  the  zone  of
    maximum subsidence (greater than 5 feet and, cur-
    rently, less than 8.5 feet), land subsidence is a factor                                                        '963- 913
    that requires careful consideration both in urban and               9      9-93
    industrial development and in maintenance of public'9-
    facilities. The three zones provide a perspective of the
    land-subsidence problem consistent with the map scale
    and goals of the Natural Hazards Maps. The reader
    may  wish to refer to specific studies on land sub-             3.
    sidence; e.g., Marshall (1973) and Gabrysch and
    Bonnet (1974).o                                                                              2
                                                                  Figure 17. Correlation of active faults with sharp breaks in
                                                               land-subsidence profiles. Elevation data from National Ocean
       PROBLEMS CAUSED BY LAND SUBSIDENCE                        Survey (formerly U. S. Coast and Geodetic Survey). Profile
                                                               parallels State Highway 3 south of Dickinson, Texas,
         The  most  obvious  consequences  of land sub-          Galveston-Houston map area.
    sidence in coastal areas are actual loss of lands in
    low-lying tidal areas and submergence of structures
    along these subsiding coastlines. Equally threatening is             MITIGATION OF LAND SUBSIDENCE
    the loss of ground elevation and the potential subjec-                   AND ASSOCIATED PROBLEMS
    tion of more land to the natural hazard of flooding,
    either  by  hurricane  surge  or  stream  runoff.  For             Although the withdrawal of ground water in the
    example, assuming an ultimate subsidence of 10 to 12          lower Texas  coastal plain is the principal cause of
    feet in the Greater Houston area, it is estimated that       subsidence and  associated  problems,  use of ground
    approximately 20,000 acres (about 31 square miles) of        water has proved to be a significant economic benefit.
    land may be lost by the year 2000; substantially more        At the present time, for example, about 650 million
    land could be lost if ultimate subsidence is greater.        gallons per day are withdrawn from aquifers in the
    Furthermore, if storm tides with the same surge height       Greater Houston area. The cost of ground water is
    as those generated by Hurricane Carla in 1961 were to        significantly less than the cost involved in transporting
    strike upper Galveston Bay today (1974), an addi-            and treating surface water. Ground water is, therefore,
    tional 70 square miles of subsiding lands, much of it        an important natural resource in the coastal area of
    extensively developed, would be flooded by hurricane-        the State and its use results in substantial savings to
    surge waters.                                                the  users.  A  recent report  on  the  economics  of
                                                                subsidence (Warren and others, 1974) suggests that the
         Depending upon original topography, subsidence          total cost of land loss and damage to structures may
    can result in change of land slopes, stream gradients,       exceed the cost difference between surface water and
    and stream drainage patterns. Changes and reversals in       ground water. The problems caused by subsidence and
    land  slope  can  and  have  caused  problems in such        ground-water  withdrawal  must  be evaluated  in the
    gravity transport systems as water and sewerage lines.       context of the economic alternatives.

         Although land subsidence is regic-..  in pattern             Land subsidence that has occurred in the Coastal
    and is regionally expressed as "bowls" of subsidence,        Zone  is irreversible and,  due  to  lag time  in clay
    recent studies by the Bureau of Economic Geology             compressibility, may continue to a substantial degree,
    indicate that, in detail, subsidence tends to occur in       even if pressure-level declines are arrested. Mitigation
    blocks. Such movements are shown by abrupt changes           of the impact already experienced and that which will
    in detailed land-subsidence profiles (fig. 17); a great      inevitably be experienced in the future can only be
    number of the downward-subsiding blocks shown on             accomplished either by vacating the impacted lands or
    these profiles are bounded by active faults. Such faults     by  constructing  protective  structures.  Of  principal
    are posing additional problems for areas of subsidence.      concern is the maintenance of lands subject tc water
                                                                encroachment, particularly those subject to flood inun-
         The  particular  hazard  of .~Surface faulting and      dation.  Construction  of protective structures is the
     associated  problems  is discussed  in  the  chapter,        only means of mitigating the problems of flooding in
    Faulting. Subsidence of shoreline lands along the open       areas already developed. Several dikes and levees have
    Gulf and  bay shorelines, which can measurably in-           already  been  built in critically impacted areas; the
    crease the already critical natural hazard of shoreline      elevation of many of these will have to be raised and
    erosion, has been discussed under Shoreline Erosion.         others  constructed.  The  U.  S.  Army  Corps  of

                                                          11-34

    Engineers  has  investigated  the  possibility  of  con-                         * FAULTING   *
    structing an extensive hurricane barrier system across
    the  southern  end  of Galveston  Bay; the  costs of                          GENERAL STATEMENT
    constructing and maintaining this system can be
    weighed  against  its  benefits  in  protection  from               Active surface faults in the Texas Coastal Zone
    flooding and inundation. For other areas where sub-            have become an important geologic hazard which daily
    sidence is occurring but where development has not             affects the economic well-being of the people in this
    yet taken place, nonstructural methods such as zoning          area. Active faults severely damage houses, apartment
    for certain uses might be more feasible.                       complexes,  and industrial plants. Some  city streets,
                                                                farm-to-market roads, and interstate highways must be
                                                                continually repaired because of fault damage; faults
                      Finalythemodiicaionof   te hstoicalpaternalso cross the runways of Hobby Airport and Ellington
      ofigond-ally, wthemdificaltion ofthe Texasoricsal platten   Air Force  Base. Active faults intersect the extensive
    can effectively mitigate subsidence and its associated        randlroadbnetwor atndvra plcesreakeing  raptnialso  ftures
    problems. Such a plan will necessarily involve signif-         anodbedanreatingamoentias. ftr
    icantly less withdrawal of ground water, but a variety drimns
    of other mitigating factors should be considered. Dif-EXNTOACIEFUIG
    ferent levels of subsidence arid associated problemsEX NTO ACIEFU IG
    may be tolerated; for example, subsidence is clearly a              Active  surface faults are relatively common  in
    much  greater problem  in low-lying, developed areas           parts of the Texas Coastal Zone. Most active faults
    than it is in less developed areas or in areas at higher       that have  been  recognized  occur in the Galveston-
    elevations. The aquifers, of course, are homogeneous           Houston  map area, where 95 linear miles of faulting
    neither  in  geologic  nor  in  hydrologic  character;         are shown on the Natural Hazards Map. Many other
    aquifers  with a minimum  of intercalated muds  can            active faults exist inland from the map area. An active
    sustain  more  withdrawal than aquifers containing a           surface fault about 4 miles long also occurs in the
    large number  of undercompacted  clay  beds.  Other            Corpus Christi map area. There are 96 miles (table 1)
    mitigating factors include the extent to which asso-           of known active faults in the entire area covered by
    ciated clays are compressible and the extent to which          this report; locations of the faults have been compiled
                   compesson ad cnsoldaton hve lreay tkenfrom studies by other workers  (Weaver and Sheets,
    place, both naturally and as a result of ground-water          1962; Van  Siclen, 1967; Sheets,  1971; Reid, 1973;
    production. Hydrologic variations indicate that certain        Clanton  and  Amsbury, 1974) and as the result of
    aquifers can sustain greater ground-water production           recent  mapping  in  this  region  by  the  Bureau  of
    with less severe declines in artesian pressure than can        Economic  Geology.  More  detailed  mapping  in the
    others. Accordingly, detailed analysis and mapping of          future  will  undoubtedly  locate  more  faults,  and
                   the eoloic ad th hydologc chractr ofthepossibly may discount some faults already mapped. In
    coastal aquifers might permit delineation of preferred         addition,  new  faults  may  be generated  in areas of
    production areas and pumpage levels (natural carrying          land-surface subsidence.
    capacity). This approach could provide the necessary
    base for determining the maximum amount of with-
    drawal and the density of producing wells that can                    IDENTIFICATION OF ACTIVE FAULTS
    exist within prescribed acceptable levels of subsidence.
    Ultimately, acceptable levels of subsidence or nonsub-               Active faults are defined as faults which have had
    sidence could be defined, depending on such factors as         movement since the end of the Pleistocene (ice age)
    present state of development and original or present           about 20,000 years ago. Most of the faults shown on
    topography or land elevation.                                  the Natural Hazards Maps, however, have moved in the
                                                                last 30 years.

         Ground water in the Texas coastal plain is and                 Four lines of evidence have been  used in this
    should be considered a very valuable natural resource.         atlas to identify active  faults:  (1) breaks in street
    Nevertheless, if subsidence and the several associated         pavements,  foundations,  highways,  airport  runways,
    problems  are to be mitigated, use of ground water,            and  swimming  pools  involving vertical displacement
    both  in  water volume  and  well density,  must  be           (cover photograph); (2) topographic scarps defined by
    adjusted to the carrying capacity of the aquifers. This        an abrupt steepening of land surface along uniform
    will require a modification of historical use patterns         slopes  or  flat areas; (3) sharp  breaks  in rates of
    and most certainly some reduction in the amount of             subsidence as determined from cumulative topographic
    ground  water used in given areas, but it need not             profiles; and (4) linear tonal anomalies on black-and-
    involve a complete curtailment of ground-water use             white  and  on  color-infrared aerial photographs.  All
    and withdrawal.                                                active faults shown on the Natural Hazards Maps have

                                                          11-35

    been verified by ground observation; most of these             are the Addicks fault in the Fairbanks oil field north-
    features  have  not  been  subjected  to  subsurface           west  of  Houston  (Van  Siclen,  1967)  and  the
    analysis.                                                      Clarksville fault in the Saxet oil field west of Corpus
                                                                Christi (Poole, 1940). Both of these faults can be
         The presence of cracks in highways and struc-             traced to depths of 7,000 feet. The Saxet fault is
    tures, coupled with evidence of continual repaving of          shown  on the Natural Hazards Map  of the Corpus
    highways  or repairing of buildings,  is an excellent          Christi area. The  Addicks fault occurs immediately
    guide for locating active faults. This type of evidence        northwest  of  the  Natural  Hazards  Map  of  the
    is considered the most reliable because it shows the           Galveston-Houston area.
    precise location of the surface expression of the fault
    and indicates that the fault is presently active. A fault           Several linear tonal anomalies, along which there
    crossing a parking lot at Ellington Air Force Base is          has been no perceptible fault movement, also correlate
    shown  on  the cover of this atlas; this fault also            with subsurface faults. Subsurface faults extrapolated
    extends  across the runways, causing extensive, con-           to the land surface in the Angleton oil field, the
    tinuing damage to the landing surfaces.                        Blessing oil field, and the West Columbia oil field
                                                                generally coincide with both location and orientation
         Changes in the elevation of survey benchmarks             of linear tonal anomalies.  The lack of detailed well
    can also be used to delineate location and amount of           control and seismic data, however, prevents a defin-
    movement  along  faults.  Topographic  profiles break          itive conclusion that, in these cases, the surface linea-
    sharply across active faults. A subsidence profile, based      tion and subsurface fault are in fact coincident.
    on cumulative, first-order topographic leveling data
    from  Virginia  Point  to  League  City  (along  State               The similarity in trend of surface and subsurface
    Highway  3 in Galveston  County), is one of several            faults indicates that most surface faults are probably
    such profiles that shows changes in topographic slope          genetically  related  either to long-trending coastwise
    at the intersections of level lines and faults (fig. 17).      fault systems extending upward from several thousand
    This technique  is capable of pinpointing very slight          feet below surface and/or to faults associated with the
    changes in differential subsidence; the only drawback          numerous salt domes of the area. Faults radiating from
    to the method is that the benchmarks are generally             salt domes may explain why some surface faults trend
    located a mile apart; this distance precludes a precise        perpendicular to the common coastwise trend. Where
    location of the active fault with the level profile.           verified,  the  association  between  surface and  sub-
                                                                surface faults indicates that some surface faults are
         Low  topographic  scarps may  show  the exact             products of natural geologic processes.
    location of a fault, but it is difficult to determine if
    the fault is presently active or inactive. The continua-            Faults of the Coastal Zone have been explained
    tion of such topographic scarps into a continually             by a number of processes: (1) deposition of sediments
    cracking  highway  pavement  nearby  does  confirm,            (Carver, 1968); (2) upward movement of salt masses
    however, the recent activity of the fault,                     to form salt domes (Quarles, 1953); (3) gulfward creep
                                                                of the coastal landmass (Cloos, 1968); and (4) bending
         The least confirmatory method for locating faults         of the landmass due to regional tectonics. Sediment
    is the  identification  of  linear tonal anomalies on          loading,  salt  movement,  and  gulfward  creep  are
    black-and-white  and  on  color-infrared  photographs.         probably the dominant causes for fault development in
    Nearly  all active faults can be identified on aerial          the  Coastal  Zone.  Sediment  accumulation  in the
    photographs,  but not all linear tonal anomalies are           present-day Gulf Coastal Zone, however, is occurring
    active faults. Aerial photographs are a very important         principally in the area of the Mississippi delta; there is
    tool, however, because they identify areas where more          little evidence to document continued growth in the
    intensive ground study should be conducted. Several            salt  domes   or  a  natural  gulfward  creep  of
    of the active faults on the Galveston-Houston area             unconsolidated sediments.
    map were initially identified by this technique and
    later substantiated by field work.                                     METHODS OF FAULT ACTIVATION

                                                                      Faults in the Texas Coastal Zone are products of
           GEOLOGIC CONTROLS OF FAULTING                           natural   geologic  phenomena.   Geologic  evidence
                                                                 suggests that fault activity today should be a relatively
         Mapped  surface faults and the surface trace of           minor  process. The frequency and activity of fault
    subsurface faults that are projected to the land surface       movement, nonetheless, is increasing. There are clear
    exhibit a strong parallelism. At this time, however,           indications that certain of man's activities, such as
    there are only a few cases for which sufficient data are       ground-water withdrawal and oil and gas production,
    available to reliably connect the surface-expressed fault      are causing this increase in fault activation. In the
    with a verified subsurface fault. Two such examples            Houston-Galveston-Baytown   area,  where  there  has

                                                           II-36

    been heavy withdrawal of ground water, oil, and gas                  The amount of land subsidence at any particular
    and extensive concomitant subsidence, several faults           point is also controlled by the amount of decline in
    have become active. Nearly all faulting has occurred in        the potentiometric surface, as well as by the amount
    areas where the potentiometric surface (piezometric            of mud within the aquifer system. If a fault acts as a
    surface) has dropped over 100 feet and where there             hydrologic  boundary  and  causes the potentiometric
    has been at least 1 foot of land-surface subsidence            surface to be at different elevations on either side of
    (Galveston-Houston map). Of course, these areas of             the fault, there will be different amounts of consolida-
    heavy ground-water usage are also the areas of greatest        tion that may be expressed as fault movement at the
    land use and, hence, the presence of active surface            land surface.
    faults and their effect is more likely to be noticed
    than in areas of less intense use.                                   Vertical displacement on the Eureka Heights fault
                                                                demonstrates fault activation by differential consolida-
                                                                tion of sediment (fig. 18). The rebound of vertical
         The monitoring of movement on the Long Point              displacement shown on the graph can be explained by
    fault and the Eureka Heights fault in western Houston
    shows a direct correlation between vertical fault dis-         the slight expansion of elastic sand bodies within the
    placement and change in the potentiometric (piezo-             aquifer on only one side of the fault. Rebound can
    metric) surface of the Chicot Aquifer (fig. 18). In            occur if there is a hydrologic boundary or if there is a
    March of each year, when the potentiometric surface            significant lateral change in the composition (facies) of
    begins to drop, movement along the Long Point fault            the aquifer.
    becomes more rapid. In October, when ground-water
    pumpage  decreases, the potentiometric surface rises                Faults may also be activated by increasing the
    and  the rate  of  fault  movement  decreases.  Some           overburden  pressures  (vertical  effective  stress), re-
    rebound even occurs on the Eureka Heights fault.               suiting in a landslide-type failure. If the Gulf Coast
                                                                sediments are treated as a large landslide, they are
                                                                unstable with a factor of safety less than 1.0 (Reid,
         Faults are being activated by natural as well as          1973).  The  Coastal  Zone  theoretically  should  be
    man-induced  phenomena.  The  Long  Point fault in             slowly sliding into the Gulf of Mexico. An increase in
    western  Houston  appears to be moving for normal              effective overburden pressures (analogous to loading at
    geologic  reasons and  because  of man-induced  phe-           the head of a landslide) should cause the unstable
    nomena.  A  topographic map with a 1-foot contour              mass of sediments to move more rapidly toward the
    interval, surveyed before 1920, shows a topographic            Gulf  of Mexico  and  initiate an  increase in active
    scarp coinciding with the location of the Long Point           faulting.
    fault (Van Siclen, 1967). The curve of the fault
    displacement  for the Long Point fault (fig. 18) at
               sectin                                      .An  increase in effective overburden  pressure is
    section a-a shows movement even though there is
                                                                accomplished by dropping the potentiometric surface
    decreased ground-water production and a rising poten-
                                                                in an artesian aquifer. The downward flow of water
    tiometric surface, possibly indicating a natural method        from  a  shallow,  unconfined  aquifer and  overlying
                                                                aquitards to the artesian aquifer transfers some of its
                                                                energy to the sediments through frictional lag, causing
         Man-induced fault movement may occur by two               an increase in the effective stress in the direction of
    different  mechanisms:  differential  consolidation  of        ground-water flow. This increase in stress is known as
    sediments and landslide-type failure caused by vertical        "seepage pressure." The effective overburden pressure
    seepage forces. Differential consolidation of sediments        in a static system  at any  particular point in the
    can occur (1) if there is more mud on one side of a            subsurface  is approximately  equal to the bouyant
    fault than on the other because of a facies change, or         weight  of the sediments.  The additional seepage is
    (2) if the fault acts as a hydrologic barrier to fluid         equal to the decline  in the potentiometric surface
    migration. The amount of land-surface subsidence by            times the unit weight of water (Lofgren, 1968). For
    consolidation of sediments depends, in part, on the            example, at a depth of 400 feet, the effective over-
    amount of compressible clay associated with a sand             burden pressure is equal to approximately 170 pounds
    aquifer. Many growth faults in the subsurface of the            per square inch (psi). A drop in the potentiometric
    Gulf Coast area are located at major facies boundaries,        surface of 200 feet will cause an additional effective
    separating, for example, prodelta muds from deltaic            overburden pressure of 86 psi or a 50-percent increase
    sands. If growth faults were active during the Pleis-           in the effective overburden pressures, which would be
    tocene, they may have caused appreciable facies varia-          the  same  as depositing  an  additional  200  feet of
    tions in the Chicot Aquifer. An equal lowering of the          saturated  sediment  over the Houston  and  Baytown
    potentiometric surface across a fault with different           area. In some places in the Houston area, the poten-
    clay-sand ratios (facies) on either side will result in         tiometric  surface has dropped  over 400  feet. This
    different amounts  of consolidation and  differential           increase in overburden  pressure may be enough to
    land subsidence.                                               activate some faults in the Gulf Coast sediments.

                                                          II-37

                                                                  ...........  .....o..
                                                                        Vertical displacement
                                                                          Long Point Fault
                                                                                                                - 200

            30 -

                                                          rtico  splacement
                                                         Eureko Heights Foult
               2-%
                                            .,,.I                                                               - 210
           20-                                                                                           --.,

          LU-.'A

                                     CL~~~~~~~~~~~~~~~~~~~~~~~~~
                              I'Drawdown                         /-

                                                                                                                   -20
                        '0~~~~~~~~~~~~~~~~~~~~~

          LU
                                                                                                                 -220

                                                                      Completion interval 488 - 850 ft

              0

                   I   I   I   I   I   I   I   I   I I   II   I  I   I   I   I     I   I   I[   I   I   I   I     I  I  I  I  I   I  I  I
                       1971                     1972                           1973                     1974
                                                                 YEAR
            Figure 18. Vertical displacement on Long Point and Eureka Heights faults in western part of Houston compared to
          drawdown of piezometric surface of Chicot Aquifer. Displacement data for April 1971 to April 1972 from Reid (1973);
          displacement data for May 1972 to January 1974 and drawdown data for piezometric surface for federal observation well
          LJ-65-13-408 from R. Gabrysch (personal communication, 1974).

         Natural movement, differential consolidation, and         where special care may be required in future develop-
    landslide-type failure are all important mechanisms for         ment.  It stands to reason that man-made structures
    fault activation; their relative importance in the Texas        should  be  built  with  full knowledge  of potential
    Coastal  Zone  has  not  yet  been  determined.  Fault          foundation problems.
    activation by oil and gas exploitation has also been
    documented  in  the  Texas  Coastal  Zone.  Pratt and                Another related problem is the distance a struc-
    Johnson (1926) observed fault activation in the Goose           ture should be built from a fault. Along some faults,
    Creek oil field. The Clarkwood fault west of Corpus             the  scarp  (the  topographic  expression)  is narrow,
    Christi, which exhibits a 4.5-foot scarp, was probably          perhaps less than 30 feet wide, such as the fault in the
    caused by oil production from the Saxet oil and gas             town of Hitchcock. Structures can be located safely in
    field. The extensive faulting over the Clear Lake oil           close proximity  to these kinds of faults, especially
    field also may have been caused by oil production.             when special engineering techniques are applied. Other
                                                                    faults have relatively wide scarps. For example, the
                 MITIGATION OF PROBLEMS                             topography in the area of the Long Point fault where
               ASSOCIATED WITH FAULTING                             it crosses Memorial Drive in western Houston appears
                                                                    to be altered up to 150 feet on either side of the fault
         One  of the purposes of including the trace of            (Reid, 1973). Construction of large, heavy structures
    active faults on the Natural Hazards Maps of this atlas        should  be  carefully  designed  for or perhaps even
    is to help  explain  the reason  for  continual repair         eliminated from this wide zone, whereas light struc-
    problems  in  particular  areas  (e.g.,  highways,  city       tures, such as houses, may not be adversely affected.
    streets, and train tracks) and to delineate those areas        The  width  of these  hazardous  zones  needs  to be

                                                              11-38

    evaluated for each fault. Because the coastal plain is so    prone lands and in attempting to explain, with current
    flat,  unlevel  land  adjacent  to  an  active  fault is     knowledge,  the  processes  leading  to  the  hazard.
    probably an indication that the area is being affected       Second, the present and projected use of hazard-prone
    by  recurring  fault movement.  Subtle variations in         lands needs to be determined and inventoried. Third,
    topography can best be determined by measuring the           hazard impact,  in terms of frequency, extent, and
    change in slope with surveying equipment. These slight       severity, can be assessed in terms of the relation of
    variations can also be determined by detailed analysis       costs  to  benefits.  Special  attention  needs  to  be
    of benchmark-level data.                                     directed to those natural hazards that may  pose a
                                                               threat to life or property. Cost-to-benefit analysis can
                                                               also be applied to determine whether it is feasible to
        The rate of movement along a Coastal Zone fault         undertake  technological  and  engineering  programs
    is another factor of importance to the people of the         aimed at mitigation.  For hazard-prone lands already
    region. The sudden movement along a California-type          developed,  the  construction  of  hazard  prevention
    fault produces earthquakes and does extensive damage          structures is the only recourse in hazard mitigation;
    to areas not even close to the active fault. Fault           for hazard-prone lands that have not been developed, a
    movement  in the Texas  Coastal  Zone, however, is           variety of alternative measures may prove to be both
    gradual,  and  earthquakes  are  not a  hazard.  The         economical and appropriate.
    amount of surface displacement that can be recognized
    on the Coastal Zone surface faults ranges up to as                In a recent study by the California Division of
    much  as 40 feet at the Hockley scarp northwest of           Mines and  Geology  (Alfors and others, 1973), the
    Houston. This accumulated displacement has, however,         total projected loss to the State of California from
    occurred over a long period of time predating man's          natural  hazards  over the period  1970  to 2000  is
    settlement of the Coastal Zone. Most fault scarps in         estimated to be $55 billion. While California has some
    the Coastal Zone are no more than a few feet high. In        hazards not common to Texas, such as earthquakes,
    Houston, the average rate of displacement has been           Texas experiences some natural hazards that do not
    estimated to be 1.3 inches per year (Reid, 1973). It is       occur in California. Importantly, the California report
    feasible to build structures across these faults as long     estimates that $38 billion of the $55 billion loss, or
    as they are designed so that engineering techniques can      about  70  percent,  can  be  prevented  by  applying
    compensate for differential offset.                          current state-of-the-art loss reduction or hazard mitiga-
                                                               tion measures. These measures include technological
                                                               and engineering approaches, as well as methods
         Faults of the Texas Coastal Zone need not be a
     pr oblem.   Future  T    constalcZon  needlt  cno be a      involving zoning and preventative planning. Further,
         prolem Fuureconstruction   on  faults  can  be
                                                               these hazard mitigation measures can be applied at a
    avoided, and where this is impossible, the awareness of      cs        $   iion   e  te          ape
                                                               cost of $6 billion over the 30-year period. A corn-
    faults will permit architects and engineers to design  b l l  over              t    eef   rio              om
                                                               parable overall cost-to-benefit ratio generally would be
    structures that can accommodate the low rates of
                                                               applicable in the Texas Coastal Zone. In addition to
    differential movement. Decreased ground-water usage           aiin  the   ee    o            as      l Zet  an
                                                               satisfying the need for increased public safety and
    may tend to deactivate many of the faults (fig. 18).
    Tehnically, this  method      of  tefault mitigation  is    fulfilling the social and political requirements, natural
    Technically,  this  method  of  fault  mitigation  is        hzr    euto    n    iiaini   ipygo
    possible. hazard  reduction  and  mitigation  is simply  good
    possible.buies
                                                               business.

                   * CONCLUSIONS *

         A number of natural hazards affect the Texas
    Coastal Zone. Some of these hazards are actually
    increasing in magnitude, but the impact of all hazards
    obviously becomes more critical with increased devel-
    opment in the Coastal Zone. The degree of impact and
    the damage and loss resulting from natural hazards
    depends upon the particular use made of hazard-prone
    lands. Mitigation of the impact of natural hazards can
    lead to significant reduction of losses currently
    sustained or likely to be sustained in the future.

         Clearly, the first step in mitigating the effects of
    natural hazards is adequate and comprehensive delinea-
    tion of hazard-prone lands and of processes that give
    rise to the hazard. "Natural Hazards of the Texas
    Coastal Zone" is a first effort in delineating hazard-

                                                        II-39

               *   SELECTED REFERENCES   e                                 Gabrysch, R. K., 1969, Land-surface subsidence in the Houston-
                                                                                Galveston region, Texas: Tokyo, Japan, InternaL
                                                                                Symposium on Land Subsidence, Proc. 1969, p. 43-54.
                                                                                   1972, Development of ground water in the Houston
    Alfors, J. T., Burnett, J. L., and Guy, T. E., Jr., 1973, Urban               district, Texas, 1966-69: Texas Water Devel. Board Rept
         geology master plan for California:  The  nature, mag-                     , 24 p.
                                                                          __    , and Bonnet, C. W., 1974, Land-surface subsidence in
          nitude, and costs of geologic hazards in California and                 the Houston-Gaveston region, Texas: U. S. Geol. Survey
         recommendations  for  their mitigation:  California Div.                op        en-file rept., 23 p
                                                                                open-file rept., 23 p.
         Mines and Geology, Bull. 198, 112 p.                                       , and McAdoo, G. D., 1972, Development of ground-
    Andrews,  P.  B.,  1970, Facies and genesis of a hurricane-                   water resources in the Orange County area, Texas and
         washover fan,  St. Joseph  Island, central Texas coast:                 Louisiana, 1963-71: Texas Water Devel. Board Rept. 156,
          Univ. Texas, Austin, Bur. Econ. Geology Rept. Inv. 67,                  47 p.
          147 p.                                                            Harris, D.  L., 1963, Characteristics  of the hurricane storm
    Behrens, E. W., 1969, Hurricane effects on a hypersaline bay, in              surge: U. S. Weather Bur. Tech. Paper No. 48, 139 p.
         Castanares,  A.  A.,  and Phleger, F. B., eds., Lagunas           Harris, W. D., and Jones, B. G., 1964, Repeat mapping for a
         Costeras, Un Simposio: Mexico, D. F., Universidad Nac.                  record of shore erosion: Shore and Beach, v. 32, no. 2, p.
          Autonoma de Mexico, UNAM-UNESCO,  Mem. Simposio                         31-34.
         Internat. Lagunas Costeras, p. 301-312.                           Hayes,  M.  O.,  1967,  Hurricanes as geological agents: Case
    Bodine, B. R., 1969, Hurricane surge frequency estimated for                  studies of Hurricanes Carla, 1961, and Cindy, 1963: Univ.
          the Gulf Coast of Texas: U. S. Army Corps Engineers,                    Texas, Austin, Bur. Econ. Geology Rept. Inv. 61, 56 p.
         Coastal Eng. Research Center Tech. Mem. 26, 32 p.                 Lofgren, B. E., 1968, Analysis of stresses causing land sub-
    Bryant, E. A., and McCann, S. B., 1973, Long and short term                   sidence:  U. S.  Geol.  Survey  Prof.  Paper  600-B,  p.
         changes  in the barrier  islands of Kouchibouguac Bay,                  B219-B225.
          southern Gulf of St. Lawrence: Canadian Jour. Earth Sci.,         Lohse, E. A., 1955, Dynamic geology of the modern coastal
         v. 10, no. 10, p. 1582-1590.                                            region,  northwest Gulf of Mexico,  in Finding ancient
    Carr, J. T., Jr., 1967,  Hurricanes affecting the Texas Gulf                  shorelines-a symposium:  Soc. Econ. Paleontologists and
         Coast: Texas Water Devel. Board Rept. 49, 58 p.                         Mineralogists Spec. Pub. 3, p 99-105.
    Carver,  R. F., 1968, Differential compaction as a cause of             Marshall, A. F., Jr., 1973, How much more will Houston sink?
          regional contemporaneous  faults: Am. Assoc. Petroleum                  The  disturbing  problem  of  land  surface subsidence:
         Geologists Bull., v. 52, no. 3, p. 414-419.                             Houston Eng. & Sci Society, The Slide Rule, v. 33, no.
    Clanton, E. S., and Amsbury, D., 1974, Open fissures associated               2 6 p.
          with subsidence and active faulting in the Houston area,          McGowen, J. H., and Brewton, J. L., 1975, Historical changes
          Texas (abs.): Geol. Soc. America, Abs. with Programs, v.                and related coastal processes, Gulf and mainland shore-
          6, no. 7, p. 688-689.                                                   lines, Matagorda Bay area, Texas: Univ. Texas, Austin,
    Cloos, E., 1968, Experimental analysis of Gulf Coast fracture                 Bur. Econ. Geology Rept Inv. 84
          patterns: Am.  Assoc. Petroleum Geologists Bull., v. 52,                   , Garner,  L. E., and Wilkinson,  B. H.,  1972, Sig-
          no. 3, p. 420-444.                                                      nificance of changes in shoreline features along Texas
    Colon, J. A., 1966, Some aspects of Hurricane Carla (1961), in                Gulf Coast (abs): Am  Assoc. Petroleum Geologists Bull.,
          Hurricane Symposium: Am. Soc. Oceanography Pub. No.                     v. 56, no. 9, p. 1900-1901.
          1, Oct. 10-11, 1966, Houston, Texas, p. 1-33.                             , Groat, C. G., Brown, L. F., Jr., Fisher, W. L., and
    Cooperman,  A. I., and Sumner, H. C., 1961, North Atlantic                    Scott, A. J., 1970, Effects of Hurricane Celia-a focus on
          tropical cyclones, September 1961: Climatological Data,                 environmental  geologic  problems of the Texas Coastal
          Natl. Summn, v. 12, no. 9, p. 468-477.                                  Zone:  Univ. Texas,  Austin, Bur. Econ. Geology Geol.
    Davis, A. B., 1961, Galveston's bulwark against the sea-history               Circ. 70-3, 35 p.
          of the Galveston seawall: U. S. Army Corps Engineers,             Morgan,  J. P., and  Larimore, P. B., 1957, Changes in the
          Galveston Dist, 19 p.                                                   Louisiana shoreline: Gulf Coast Assoc. Geol. Socs. Trans.,
    Dolan, R., and Godfrey, P., 1973, Effects of Hurricane Ginger                 v. 7, p. 303-310.
          on  the barrier islands of North  Carolina: Geol. Soc.            Morton,  R. A., 1974, Shoreline changes on Galveston Island
          America Bull., v. 84, p. 1329-1334.                                     (Bolivar Roads to San Luis Pass): Univ. Texas, Austin,
             , and Odum, W. E., 1973, Man's impact on the barrier                 Bur. Econ. Geology Geol. Circ. 74-2, 34 p.
          islands of North Carolina: Am. Scientist, v. 61, no. 2, p.       __        , and Pieper, M. K., 1975, Shoreline changes on Brazos
          152-162.                                                               Island  and  south Padre Island (Mansfield Channel  to
    Dunn, G. E., and Miller, B. I., 1964, Atlantic hurricanes: Baton              mouth of the Rio Grande): Univ. Texas, Austin, Bur.
          Rouge, La., Louisiana State Univ. Press, 377 p.                         Econ. Geology Geol. Circ. 75-1.
    El-Ashry, M. T., and Wanless, H. R., 1968, Photo interpretation         National Geodetic Survey, 1974, Report: 1973 releveling of the
          of shoreline changes between Capes Hatteras and Fear                    Houston-Galveston  area, Texas: U. S. Dept. Commerce,
          (North Carolina): Marine Geology, v. 6, p. 347-379.                     49 p.
    Fisher, W.  L,  1973,  Land-surface  subsidence  in the Texas          National Oceanic and  Atmospheric  Administration,  National
          Coastal Zone: Texas House of Representatives, testimony                Hurricane   Center,   1900-1974,  Various  sources  of
                                                                                Hurricane  Center,  1900-1974,  Various  sources  of
          presented to Committee on Natural Resources.
             , Brown, L. F., Jr., McGowen, J. H., and Groat, C. G.,               published data.
          1973, Environmental geologic atlas of the Texas Coastal           Nordquist, R. W., 1972, Origin, development, and facies of a
          Zone-Beaumont-Port Arthur area: Univ. Texas, Austin,                    young  hurricane washover fan on southern St. Joseph
          Bur. Econ. Geology, 93 p.                                               Island, central Texas Coast: Univ. Texas, Austin, Master's
             , McGowen, J. H., Brown, L. F., Jr., and Groat, C. G.,               thesis, 103 p.
          1972, Environmental geologic atlas of the Texas Coastal          Orton,  R.  B.,  1970,  Tornadoes  associated  with  Hurricane
          Zone-Galveston-Houston area: Univ. Texas, Austin, Bur.                 Beulah  on  September  19-23,  1967:  Monthly  Weather
          Econ. Geology, 91 p.                                                    Review, v. 98, no. 7, p. 541-547.
    Frank, N., 1974, The hard facts about hurricanes: Natl. Oceanic           __     , and Condon,  C. R., 1970,  Hurricane Celia, July
          and Atmospheric Adm., NOAA Mag., July 1974, p. 4-9.                     30-August  5:  U. S.  Dept   Commerce,  NOAA,  Envi-

                                                                   II-40

         ronmental  Data  Service,  Climatological Data, National                briefings, 1974: Austin, Texas, Texas Coastal and Marine
         Summary, v. 21, no. 8, p. 403-418.                                      Council, unpaged,
    Petitt, B. M., Jr., and Winslow, A. G., 1957, Geology  and              Turner, Collie, and Braden, Inc., Consulting Engineers, 1966,
         ground-water resources of Galveston County, Texas: U. S.                Comprehensive  study  of  Houston's  municipal  water
         Geol. Survey Water-Supply Paper 1416, 157 p.                            system for the City of Houston, Phase I, Basic studies,
    Poole, J. C., 1940,  Saxet oil and gas field, Nueces County,                  50 p.
         Texas: Am. Assoc. Petroleum Geologists Bull., v. 24, no.          U. S. Army  Corps of Engineers, 1962, Report on Hurricane
         10, p. 1805-1835.                                                      Carla 9-12 September 1961: U. S. Army Corps Engineers,
    Pratt, W. E., and Johnson, D. W., 1926, Local subsidence of the               Galveston Dist., 29 p.
         Goose Creek oil field: Jour. Geology, v. 34, p. 577-590.                   1968,  Report on  Hurricane Beulah 8-21 September
    Price, W.  A.,  1952,  Reduction  of maintenance  by  proper                  1967: U. S. Army Corps Engineers, Galveston Dist., 26 p.
         orientation of ship channels through tidal inlets: Houston,                1971a, Report on Hurricane Celia 30 July-5 August
         Texas,  Proc.,  2d  Conf.  Coastal  Eng.,  Chpt.  22,  p.               1970: U. S. Army Corps Engineers, Galveston Dist., 13 p.
         243-255. Reprinted  in Texas A&M  College, Contr. in                       1971b, Shore protection guidelines: Washington, D. C.,
         Oceanography and Meteorology, v. 1, no. 12, p. 101-113.                 Dept. of the Army, Corps Engineers, 59 p.
            1956,  North  Beach  study  for the City of Corpus             Van Andel, T. H., and Poole, D. M., 1960, Sources of Recent
         Christi: Corpus Christi, Texas, Zoning and Planning Dept.,              sediments in the northern Gulf of Mexico:  Jour. Sed.
         City Hall, Rept. on file, 120 p.                                        Petrology, v. 30, p. 91-122.
    Quarles, M., Jr., 1953, Salt-ridge hypothesis on origin of Texas        Van Siclen, D. C., 1967, The Houston fault problem, in Proc.,
         Gulf  Coast  type  of  faulting:  Am.  Assoc.  Petroleum                3d Ann. Mtg., Texas Sec., Am. Inst. Prof. Geologists, p.
         Geologists Bull., v. 37, no. 3, p. 489-508.                             9-29.
    Reid,  W.  M., 1973, Active fa-llts in Houston, Texas: Univ.           Warren, J. P., Jones, L. L., Griffin, W. L., and Lacewell, R. D.,
         Texas, Austin, Ph.D. dissert., 122 p.                                   1974, Cost of land subsidence due to groundwater with-
    Scott, A. J., Hoover, R. A., and McGowen, J. H., 1969, Effects                drawal: Texas A&M  Univ., Texas Water Resources Inst.,
         of Hurricane Beulah, 1967, on Texas coastal lagoons and                Tech. Rept. 57, 79 p.
         barriers, in Castaaires, A. A, and Phleger, F. B., eds,           Weaver, P., and Sheets, M. M., 1962, Active faults, subsidence,
         Lagunas  Costeras,  Un   Simposio:  Mexico,   D.  F.,                   and foundation problems in the Houston, Texas, area, in
         Universidad Nac. Autonoma de Mexico, UNAM-UNESCO,                       Rainwater, E. H., and Zingula, R. P., eds., Geology of the
         Mem. Simposio Internat. Lagunas Costeras, p. 221-236.                   Gulf  Coast  and  Central  Texas  and  guidebook  of
    Shalowitz, A., 1964, Shore and sea boundaries:  U. S. Dept.                   excursions:  Houston,  Texas,  Houston Geol. Soc. Field
         Commerce Pub. 10-1, v. 2, 749 p.                                        Excursion Guidebook, p. 254-265.
    Sheets, M. M., 1971, Active surface faulting in the Houston             Wesselman, J. B., 1972, Ground-water resources of Fort Bend
         area, Texas: Houston Geol. Soc. Bull., v. 13, no. 7, p.                 County,  Texas:  Texas Water Devel. Board Rept. 155,
         24-33.                                                                  176 p.
    Shepard, F. P., 1960a, Gulf Coast barriers, in Shepard, F. P.,          Wilkinson, B. H., 1974, Matagorda Island-the evolution of a
         Phleger,  F.  B.,  and  van  Andel,  T.  H., eds, Recent                Gulf Coast barrier complex: Univ. Texas, Austin, Ph.D.
         sediments, northwest Gulf of Mexico: Tulsa, Okla, Am.                   dissert., 178 p.
         Assoc. Petroleum Geologists, p. 197-220.                          Winslow, A. G., and Doyel, W. W., 1954, Land-surface sub-
            1960b,  Rise of sea level along northwest Gulf of                    sidence and its relation to the withdrawal of ground water
         Mexico, in Shepard, F. P., Phleger, F. B., and van Andel,               in the Houston-Galveston region, Texas: Econ. Geology,
         T. H., eds., Recent sediments, northwest Gulf of Mexico:                v. 49, no. 4, p. 413-422.
         Tulsa,  Okla.,  Am.  Assoc.  Petroleum  Geologists,  p.                    , and Wood, L. A, 1959, Relation of land subsidence
         338-344.                                                                to ground-water  withdrawals in the upper Gulf Coast
            1973,  Submarine  geology:  New  York,  Harper  and                  region,  Texas:  Am.  Inst.  Mining,  Metall.,  Petroleum
         Row, 517 p.                                                             Engineers Trans., v. 214, p. 1030-1034.
    ___ I , and Moore, D. G., 1960, Bays of central Texas coast,           Wood,  L. A., Gabrysch, R. K., and Patten, E. P., Jr., 1965,
         in Shepard, F. P., Phleger, F. B., and van Andel, T. H.,                Analog  model  study of ground water in the Houston
         eds., Recent sediments, northwest Gulf of Mexico: Tulsa,                district, Texas: Texas Water Comm. Bull. 6508, 103 p.
         Okla., Am. Assoc. Petroleum Geologists, p. 117-152.
    Simpson, J., 1966, Hurricane modification experiments, in
         Hurricane Symposium: Am. Soc. Oceanography, Pub. No.
         1, p. 255-292.
    Stafford, D. B., 1971, An aerial photographic technique for
         beach erosion surveys in North Carolina: U. S. Army
         Corps Engineers, Coastal Eng. Research Center Tech.
         Memo. 36, 115 p.
            , Bruno,  JR.  O.,  and  Goldstein,  H. M.,  1973, An
         annotated bibliography of aerial remote sensing in coastal
         engineering: U. S. Army Corps Engineers, Coastal Eng.
         Research Center Misc. Paper No. 2-73, 122 p.
    Stapor, F., 1973, History and sand budgets of the barrier island
         system in the Panama City, Florida, region: Marine
         Geology, v. 14, p. 277-286.
    Sugg, A. L., and Pelissia, J. M., 1968, The hurricane season of
         1967: Monthly Weather Review, v. 96, no. 4, p. 247.
    Swanson, R. L., and Thurlow, C. I., 1973, Recent subsidence
         rates along the Texas and Louisiana coasts as determined
         from tide measurements: Jour. Geophys. Research, v. 78,
         no. 15, p. 2665-2671.
    Texas Coastal and Marine Council, 1974, Hurricane awareness

                                                                    II-41

                           SECTION III

                   HAZARD ZONE DELINEATION

                   FOR STANDARDS AND CODES

         The principal purposes of the effort reported in this
    volume are to develop minimum performance criteria for structures
    located in high-hazard coastal areas and to draft a model building
    standard that can be readily incorporated into common existing
    building practices. From the beginning it was obvious that it
    would be necessary to define specific hazard zones on the basis
    of the degree of exposure to destructive processes, and to
    develop standard requirements for each zone.*

         The standards and model building code presented in the
    following section are designed to provide a reasonable chance
    for survival of buildings during the occurrence of a hurricane.
    Any structure built to the code is likely to survive, but an
    extra margin is provided for high-rise structures that could be
    used for safe refuge, i.e., vertical evacuation of residents.
    For high-rise buildings, specific requirements are given for the
    skin or cladding, since these are of utmost importance if the
    building is to be used for safe refuge.

    THE TEXAS DESIGN HURRICANE

         Before looking at the zone delineation process, it is
    necessary to determine what parameters are most likely to be
    associated with the occurrence of a "probable" hurricane.
    Many approaches exist for statistically estimating hurricanes
    of specific recurrence intervals, and for classifying them as
    minor, major, or great hurricanes. Section II, "Natural Hazards
    of the Texas Coast," contains a detailed discussion of these
    approaches. Some federal agencies have used the concept of
    standard, project or probable maximum hurricanes. These
    classifications differ among agencies, mostly because the different
    agencies have different missions and thus are concerned about
    different effects.

         For the purpose of this report--the development of model
    minimum building standards--a mixture of the likely forces taken
    from federal agencies' definitions of typical hurricanes, tempered

      Since this hazard zone delineation process is vital to correct
      application of the model standard, this entire section should
       be distributed with any copies of the model standard.

    by the judgment of a panel of experts, is combined to give
    the Texas Building Design Hurricane (TDH). This hurricane
    is severe enough to warrant consideration in building
    standards and occurs frequently enough to make the use of more
    rigid standards than those presently being used economically
    feasible. It is expected to generate the following sources of
    potential damage:

         *  WIND:  maximum windspeeds (fastest mile) up to
            140 mph at a height of 30 feet, increasing with
            height in accordance with the one-seventh power
            law to a maximum about 300 feet above the surface
            for open coastal areas. Peak gust speeds will
            exceed the sustain'ed values by varying percentages
            as given in the wind load section of the code.
            (In general, gust percentages will decrease with
            height increase.)

         a HURRICANE TIDES (three sources of potential damage):

            1. SCOUR due to currents and wave action, including
                washovers;

            2. BATTERING due to waterborne debris;

            3. FLOODING due to combinations of rises in sea
                level from storm surge and inland runoff from
                heavy rains and riverine discharges.

    HURRICANE HAZARD ZONES

         An analysis of the processes and forces associated with
    a hurricane; extensive examination of empirical damage data;
    and a thorough knowledge of the geological, hydrological, and
    topographical characteristics of the Texas coast leads to the
    identification of four distinct coastal hazard zones.* These
    are shown in Figure 111-1. Ranging from most to least severe,
    they are

         ZONE A: 1. 140 mph sustained winds;

                  2. scouring action affecting foundation
                        design;

                  3. battering due to waterborne debris.

      For further discussion of specific daimage mechanisms, see
       Section II of this report; U.S. Army Corps of Engineers
       Hurricane Dcmiage Survey Reports; and NOAIA's damage assessments.

                               111-2

                                WIND                   Zones
                                14O MPF~

                                                      A.
                                 BATMERIN             VD
                                                      WIND
                                                      FLO)DI NG

                                       WIND~~~~B~TrnI

                                 140 MPH
                                     BATT~...... .   WINDE!N

                                 140 MP14
                                                      FLooDING

                                   WIND
                                                     WID

                                -WIND

                        FIGURE 111-1
                   (SAME AS FIGURE i-2)
    SCHEMATIC REPRESENTATION OF HAZARD ZONES A TO D IN
                    TEXAS COASTAL AREAS,

                            111-3

                    4. flooding (still water levels from
                        expected hurricane inundation more
                        than one foot above building grade
                        level).

          ZONE B: Same as Zone A except without scour.

          ZONE C: Same as Zone A except without scour and
                   battering.

          ZONE D: 140 mph sustained winds at C-D boundary,
                   diminishing inland as an inverse
                   function of distance to 100 mph.*

    COMPUTATION OF HAZARD ZONES

          For regular coastlines without barrier islands, embay-
    ments or estuaries, the four hazard zones will comprise a
    family of narrow strips paralleling the coast. The inland
    extent of each is normally a function of the height
    of the storm tide hydrograph at the open coast, the topo-
    graphy of the coastal plain, and the rainfall runoff associated
    with the hurricane.

          When barrier islands and large estuaries are present
    the inland flooding and the disfiguration of otherwise uniform
    hazard zone strips is influenced by (1) barrier islands
    which impede volume transport of surge water inland, (2) the
    additional component of surge (wind setup) due to wind stresses
    on shallow water surfaces in estuaries which in turn is a
    function of (3) the bathymetry and geometry of the estuary,
    (4) the size and rate of movement of the hurricane, (5) the
    rainfall runoff and riverine discharges (fresh water), (6) the
    initial rise of salt water (1-3 feet) in the estuary (fore-
    runner tide), often arriving more than 24 hours ahead of
    the storm center, (7) the tendency for seiching action as
    the hurricane moves inland, and (8) the usually smaller incre-
    ments (on the Texas coast) contributed by astronomical tides and
    wave setup.

          There is no general two-dimensional model for use in bays
    or estuaries to compute numerically the total inundation

                  40
       VD = 100 + 1+-d ' where VD = wind speed in Zone D

                              d = distance inland from C-D boundary

                              III-4

     potential across inland bay shores.* Most models with enough
     physics incorporated to accomplish this are either adapted to
     the bathymetry of a single shallow estuary, or otherwise compute
     in one dimension the inundation along a single line or transect
     inland from the coast. To model, in two or more dimensions,
     the scope of inland flooding for a single bay area is a very
     expensive and time-consuming task, and the results apply only
     to that area. What is needed is a reasonable, conservative
     approximation procedure which can be used quickly and inexpensively
     by competent engineers, and which will always yield the same
     results.

          The method and alternative specific procedures described
     in Annex C meet these requirements. It is a general method,
     physically founded, that can be applied quickly and inexpensively
     by qualified engineers. It is sufficiently objective to yield
     repeatable results, and precise enough to use for determining
     the hazard zone of a particular structure and for establishing
     the appropriate building standard/code.**

     PRIMA FACIE FACTORS IDENTIFYING HAZARD ZONES***

          Irrespective of the flood levels computed for a building
     site using the procedures described in Annex C, the following
     physical exposures will be overriding in determining in which
     zone a particular site is located.

          I. ZONE A. Areas of washover and scour:

              a. Narrow, low segments of barrier islands and
                  peninsulas that are generally breached as a

     * A quasi-two-dimensional model has been applied to individual
        bays and estuaries of some portions of the Texas coast by
        the U.S. Army Corps of Engineers based upon work by Reid
        and Bodine (1970), and work is in progress on similar models
        elsewhere. However, each bay poses a separate modelling
        problem, and the output comprises only the surge component
        of tidal flooding, not the freshwater contributions or
        the initial rises, which on the Texas coast may be considerable.

    ** A technical paper by Drs. Simpson and Freeman, who developed
        the procedure, is available through the Texas Coastal and
        Marine Council for those wishing to explore the theory and
        mathematics of the procedure.

    ~** As used herein, "prima facie conditions" refer to physical
        evidence--meteorological, geological, topographical, or
        hydrological--which may be in disagreement with the analytical
        results. In such cases, the specified prima facie evidence
        will govern.

                                III-5

        result of elevated water levels during hurricanes
        or tropical storms will be classified as Zone A.
        Such areas include much of Bolivar Peninsula in
        the vicinity of Bolivar Bay, Matagorda Peninsula
        east of Green's Bayou, the southern end of
        San Jose Island, and South Padre Island. Other
        coastal areas having experienced or presently
        holding a high potential for washover (breaching)
        during a hurricane will also be classified as
        Zone A. Sources for the identification of such
        areas include the Bureau of Economic Geology, the
        University of Texas at Austin.

        b.   A zone extending between Gulf beaches and a
        line at least 300 feet inland from the maximum
        elevation immediately adjacent to the beach (e.g.,
        dune crest or crest of sand and shell ramp) will
        be classified as Zone A.

        c. A zone along low-lying (less than 10 feet) unpro-
        tected (nonbulkheaded) bay shorelines, extending
        at least 200 feet inland from the highest elevation
        near the shoreline will be classified as Zone A.

         d.   Areas within 200 feet of unprotected (non-
        bulkheaded) navigation channels on peninsulas and
        barrier islands will be classified as Zone A.

        e.  Areas with a sand substrate subject to
        hurricane flooding greater than 3 feet in depth
        and with expected water current velocities greater
        than 3 feet per second for one hour or more
        during the rise or fall of the surge will be
        classified as Zone A.

    1I. ZONE B. Battering:

         In the absence of washover channels and extensive
        scour, battering from waterborne debris will be
        expected to occur and will comprise the basis for
        defining Zone B under the following situations:

         a.  On barrier islands and peninsulas a zone of
        flooding extending inland from the most landward
        foredune or ridge line to the boundary of Zone C,
        or on low-lying bay shorelines having primarily
         clay substrates, a zone extending inland from the
         shoreline at least 500 feet regardless of building
         density.

                         III-6

          b.  In areas where hurricane flooding is expected
         to be greater than 4 feet, building density is not
         greater than one major structure per acre, and
         fetch is considered to be the distance a wind of
         constant direction travels without interruption or
         diversion over a water surface.

    III. ZONE C. Wetting:

          In the absence of the above conditions, but where still
         water hurricane flood levels are in excess of one foot,
         the area will be designated as Zone C.

     IV. ZONE D. Wind Only:

         Zone D is concerned only with wind forces on structures,
          primarily the dynamic loads. The problem in defining
          the inland extent of unusually severe hurricane winds
          and thus the width of Zone D is that the rate at which winds
         of design speed at the coast diminish is less a function of
          the roughness of the terrain than it is of the baroclinity*
          of the environment into which the hurricane moves as it
          passes inland. If a hurricane retains the barotropic**
          environment which attends it most of its life over ocean
          areas, the loss of energy flowing from sea to air will rob
          a hurricane of its hurricane force winds in a few hours after
          it crosses a coast. If, however, it encounters a baroclinic
          environment, especially one which accelerates the outflow
          at the top of the cloud system, it may retain winds of
          75-100 mph great distances inland--e.g., in Hurricane
          Hazel, 1954, and to a lesser degree, Hurricane Agnes in
          1972. However, there are no examples of hurricanes maintaining
          such extreme winds as 140 mph observed at ocean or bay
          shores more than a few tens of miles inland. Therefore,
          Zone D is arbitrarily defined as an area in which the wind
          at the C-D boundary is 140 mph, but diminishes to 100 mph
          as an inverse function of distance inland from the C-D
          boundary***, to a minimum of 100 mph. In this specification

      * Baroclinity - a property of the atmosphere characterized by
         large horizontal temperature variations. Energy from baroclinic
         sources sometimes succeeds in accelerating movement of air
         flowing out of the top of hurricanes, and thus the flow of
         air through the hurricane, keeping it strong after it loses its
         initial barotropic energy sources.

     ** Barotropic - a condition characterized by very small temperature
         gradients and one in which the sources for the development of
         storms depends primarily upon the release of heat from the
         growth of cumulus clouds. This condition is essential to the
         formation of hurricanes and for the growth which characterizes
         most of their life cycle.

    *** VD = 100 +-40 , where VD = wind speed in Zone D
                    l+-T          d = distance inland from C-D boundary

                                 111-7

             it is acknowledged that large variations around these
             figures will occur from hurricane to hurricane. In a
             few cases even small interior areas of barrier islands
             may be classified as Zone D where elevations are
              substantially above 20 feet MSL and the soil is
              stabilized from erosion.

    DOCUMENTATION OF HURRICANE-RELATED PROCESSES AND ATTENDANT DAMAGE
    IN ZONE A

          From the standpoint of coastal planning, Zone A is the
    most critical zone for building design. It is also the most
    readily identified hazard zone in the field and on aerial
    photographs because of the distinct alteration of the land-
    scape by strong currents and wave action. Extensive coverage
    of aerial photographs taken immediately following Hurricanes
    Carla, Beulah, and Celia provide sufficient information for
    the delineation of washover channels as defined above.

          The damage from Hurricanes Carla, Beulah, and Celia
    is well documented in other reports (U.S. Army Corps of
    Engineers, 1962, 1968, 1971; Brown and others, 1974;
    Hayes, 1967; McGowen and others, 1970), but the principal
    cause of damage from each storm (surge, aftermath rainfall,
    wind) exceeds the equivalent characteristics of the design
    storm used to determine the extent of hazard-prone areas.
    On the other hand, data on dune retreat and shoreline
    changes are available for other storms; for example, the
    1949 hurricane (aerial photographs) and Hurricane Fern
    (beach profiles). From these and other field data we can
    determine the maximum and average beach scour and dune
    retreat. These figures can then be used with other physical
    parameters to determine the projected limits of areas
    affected by hurricane-related processes.

          Several storms have caused beach erosion and dune
    retreat of 50 feet or more.   Maximum shoreline erosion
    documented on the Texas coast occurred during Hurricane
    Carla when a segment of Matagorda Peninsula retreated 600
    feet (McGowen and Brewton, 1975).

          Dune retreat and shoreline erosion produced by
    surge from Carla were of extraordinary magnitude in the
    area affected by the right semicircle of the storm.
    Fortunately, there was no residential or commercial
    development near the site of landfall on Matagorda
    Peninsula, for many buildings would have been destroyed.
    Recently, a storm less intense than Carla (Hurricane
    Eloise, September 1975) struck the Florida coast and
    caused extensive damage. Building foundations were
    undermined and superstructures collapsed as a result of
    beach scour and dune retreat (Morton, 1976).

                               I1I-8

         The fixed distance (300 feet) representing the landward
    boundary of Zone A was selected primarily for a pragmatic
    reason: the constant distance facilitates the hazard zone
    identification process. Otherwise, it would be necessary to
    develop a complicated procedure whereby the probability of
    storm occurrence for a given time period and coastal segment
    would be used with an average value of dune retreat per storm
    to determine, in conjunction with dune characteristics, a
    theoretical dune erosion value which then would be used with
    a margin for indeterminants to define the landward boundary
    of Zone A. In essence, the value of 300 feet represents an
    estimate of dune retreat that might be expected over a long
    period with the probability of a hurricane every 11 years, and
    the probability of a great storm every 29 years. Historical
    records indicate that the cumulative effect for a long period
    would be about 200 feet with a margin of safety of 100 feet.
    This does not suggest that scour will not occur 300 feet inland
    from the dune crest, but rather that the probability of
    such an event is rather low.

    ALTERNATIVE BOUNDARY SELECTION--ZONE A

         In many respects, the beach and washover areas described
    in preceding sections are similar to Zone V (velocity) on
    the FIA flood maps.* There are, however, minor differences
    in the boundaries. For example, the FIA maps exhibit
    straight line boundaries which do not conform to the
    topography. In contrast, the boundaries proposed for the
    hurricane hazard zones are controlled largely by the
    topography; therefore, mapped boundaries for Zone A would not
    be straight lines but would be dependent on the configuration
    of the dunes and washover areas. Another difference in
    approach is that the FIA maps emphasize elevation whereas
    the hurricane hazard zones emphasize distances on the ground.

    PEAK STORM SURGES

         A major input to the zone determination is an estimate
    of the peak storm surge and flooding levels at the open
    coast and at bay shores. Too often it is assumed or
    concluded that the highest surges always occur at the open
    coast directly exposed to the sea. Factually, the ratio of
    surge heights at the open coast to those on bay shores depends
    upon the speed, size and direction of approach of a hurricane.
    A severe slow-moving hurricane can cause much higher flooding
    at bay shores many miles from the open coast than at the

     *Those maps issued by the Flood Insurance Administration
       that define their categories of floodplain.

                               111-9

    coast itself. For example, in Hurricane Carla, 1961, the
    maximum surge height on the Gulf front of barrier islands
    was approximately 15 feet, but near Port Lavaca, 23 miles
    away, the surge exceeded 22 feet. On the other hand, a
    storm moving inland at moderate speeds may cause surges of
    equivalent height at both open beaches and bay shores far
    inland, and a rapidly moving hurricane will cause greater
    tides at the open coast. The selection of a design
    hurricane needs to provide an equitable balance between
    these possibilities, and the methodologies used to define
    the Texas Design Hurricane addressed this problem.

         The profile of peak open-coast surges for the Texas
    Design Hurricane is presented in Figure 11-2. The methods
    used and input parameters for computing this profile are
    contained in Annex A.

         The average surge level is 13.5 feet, with bimodal
    peaks of 15.4 feet and 17.7 feet at central Padre Island
    and near Orange, respectively. Minimum expected surges of
    12.0 feet and 11.5 feet occur at Port Isabel and Rockport,
    respectively. To these surge heights must be added the
    initial rise and astronomical tide stage to obtain the
    total hurricane tide. As explained in Annex A, this
    increment totals 3 feet to which the freshwater accumulations
    must be added to compute the total flooding potential.

    PROCEDURES FOR COMPUTING INLAND FLOOD LEVELS AND FOR
    DESIGNATING HAZARD ZONES

         The flood levels caused by open coast storm tides,
    the additional surges which develop over bays and inland
    water, the tidal maxima at bay shores, and associated
    inland flooding, are presented in the Annexes to this
    section.

         Annexes A, B, and C present the procedures for com-
    puting flood levels and other characteristics which are
    necessary to identify the hazard zones for a proposed
    building site in order to select the appropriate model
    building code.

         Annex A contains the background and results of
    computations of open coast storm tides to be expected
    from the Texas Design Hurricane.

         Annex B describes the methodology and conceptual
    basis for computing surge maxima at bay shores and the
    inland flooding these cause.

                              III-lo

                Houston

                                              LA.~ L ORER~~--_,

                            , ALVESTON

                             Texas Design Storm Surge
                     20 ~~~(Open Coast)

    ~~~~~~~PT. ISABEL  P.AA~S               FEPR  AVSO   EA-A

                            FIGURE~~~~~~~C 1411-2

               (See A-i f~ormdetaieelationPons)

                        III-11

         Annex C details the procedures to be used in
    computing inland flooding profiles and the design flood level
    at a specific location. Alternative methods for applying
    these Procedures, with sample computations, are
    presented. They include (1) the use of a nomogram for
    computing the series of hydrographs needed to construct
    flood level profiles, and (2) a program for use with a
    hand-held programmable calculator to accomplish the same
    purpose more rapidly. A listing of the program for the
    latter procedure is included. The results using either
    method are equivalent.

          Not presented here, but currently being developed,
    is a FORTRAN IV program which can be used with almost
    any modern time-share facility which has a FORTRAN
    compiler to obtain the same results very quickly.

          The time required for determining the design flood
    level at one location, using the nomogram is nominally
    6 hours; with the programmable calculator, 2 hours; and
    with the FORTRAN program, this can be done with a few minutes
    of man-time and then only a few seconds of computer-time.

    For references, see Appendices following Section IV.

                               III-12

                             ANNEX A

              COMPUTATION OF HURRICANE TIDES

                       AT THE OPEN COAST

         The hurricane tide at the open coast is a combination
    of several components, the principal one of which is
    storm surge. Other components include (1) the astro-
    nomical tide; (2) the "initial rise" or "forerunner tide"
    (occurring more than 24 hours prior to arrival of the
    hurricane with range of 1-3 feet); (3) wave setup,
    (rarely over 2 feet, but in some peculiar bathymetric
    configurations may be much larger; e.g., Eloise, 1975,
    where surge may have been only 9 feet, and wave setup
    4-6 feet); (4) wave runup (usually small); and (5) rainfall
    runoff. At two Texas coast locations wave setup may be
    important: (a) central Padre Island and (b) the Rockport
    area. Within computational error the open coast hurricane
    tide on the Texas coast is primarily a function of the
    computed surge height.

          The computations of storm surge profiles for the open
    coast of Texas have been made for a severe hurricane whose
    damage potential, in terms of characteristic strength,
    size, movement, and recurrence frequency, can be effectively
    and economically mitigated by building design measures.

          The climatology upon which the computations were
    based is taken from a recent study by Ho, Schwerdt, and
    Goodyear (1975).* The characteristics used in this study,
    a function of latitude, are listed in Table A-1 and vary up
    the coast as follows:

           1. Central pressure: 903mb at Port Isabel
              increasing to 937 at Orange.

           2. Radius of maximum wind: 14 miles.

           3. Hurricane movement at point of landfall:
              14 kts.
           4. Direction of hurricane approach: normal
              to the coastline.

       NOAA Tech. Report NWS 15 entitled, "Some Climatological
       Characteristics of Hurricanes and Tropical Storms, Gulf
       and East Coasts of the United States" (May, 1975).

                              III-A-1

                                      TABLE A-1

                    INPUT DATA FOR SPLASH II PROGRAM TO COMPUTE

                               SURGE HEIGHTS FOR THE

                          STATE OF TEXAS DESIGN HURRICANE

    Point      Landfall           Pmi      SPma       Rmax       C          Dir. of
                                 (mb)      (m)  ( mi)         (kt)          Storm

      1    Pt. Isabel:  30L        903       113       14       14              W

      2    Pt. Isabel:  0          904       112       14       14              W

      3    Pt. Isabel:  30R        910       106       14       14              W

      4    Pt. Isabel:  60R        915       101       14       14              W

      5    Pt. Isabel:  90R        920        96       14       14              W

      6    Aransas Pass: 12R    925           91       14       14             WNW

      7    Matagorda:  6L          928        88       14       14              NW

      8    Matagorda:  23R         930        86       14       14              NW

      9    Matagorda:   54R        931        85       14       14              NW

     10    Galveston:  15L         934        82       14       14             NNW

     11    Galveston:  15R         936        80       14       14             NNW

     12    Galveston:  45R         937        79       14       14             NNW

     13    Cameron, La.:  12L   937           79       14       14              N

                                          III-A-2

         This climatology is statistically founded without
    explicit dynamical constraints and as such may tend to
    overemphasize the gradient characteristics from southern to
    northern coastal areas. This may result in a slight under-
    estimate of computed surge heights in the upper coastal
    reaches. However, the differences are believed to be
    within the probable errors in distributing the water inland.

          The selection of a relatively small radius of maximum
    wind and fast approach to the coast was adopted as a most
    equitable compromise in obtaining realistic flood levels at
    the open coast and for inland reaches of estuaries and bays.
    A slower-moving storm would provide lower surge values at
    the open coast and high values for bay shores. A larger
    radius of maximum wind would be inconsistent with the very low
    central pressure adopted. The central pressures are those
    which have an expected return period of 100 years. Realistic
    values of flooding at bay shores have been built into the
    procedures for computing inland flooding as a function of
    wind setup on the inland water bodies described in Annexes
    B and C.

          The model used for computation of the surge profiles,
    known as SPLASH II, was developed by Jelesnianski (1972). The
    decision to use this model is supported by the report of a
    Panel on Coastal Surges appointed by the Building Research
    Advisory Board of the National Academy of Science.* This
    report reviews a number of dynamic prediction models and
    concludes that the Jelesnianski model is the best presently
    available for computing surges at the open coast.

          Computations were made at 13 positions, 30 miles apart
    for a hurricane approaching normal to the coastline and
    having the characteristics listed in Table A-1. The results
    are presented in Figure A-i, where the profile represents
    the envelope of peak surge values for the 13 computations
    made. In the procedures for computing the inland flooding,
     Annex B, the convention adopted is to assume that a pre-
    liminary rise of two feet exists both at the coast and on
    inland water prior to the initiation of rises due to surge.
    Then an increment of one additional foot due to astronomical
    tide stage is added to the computed peak storm surge for
    the Design Hurricane as a basis for deriving the surge
    hydrograph. This combination is approximately equivalent to
    the arrival of peak surge at time of spring high tide.

     *National Academay of Science, Panel of Hurricane Surges,
       1975, Washington, D.C.

                              111-A-3

                       100                    200                    300

                           TEXAS DESIGN STORM  SURGE

     20 2                                  (Onen Coas0                                  J      20

    I--is

    U10

               OPE                                           Rv MAX - 14m i

                                                  R  lO AT  14K.
           5se ~ ~ ~ ~ ~ Dtie  ine  fmFiue15

                         Pt. Aransas                   FrTexas-La.

                                             if _-_   - S lBo              rder
      0                     100                   200                     300
               OPEN COAST DISTANCE FROM PT. ISABEL LIGHT   (mi.)

                                   FIGURE A-1

                       SURGE ELEVATIONS AT OPEN COASTLINE
                           (Detailed inset from Figure II-2)

    HURRICANE HYDROGRAPH

         The Design Hurricane characteristics from Table 1 run on
    the SPLASH II program produce a hydrograph whose shape is
    essentially that of Figure A-2. Hydrographs were computed
    for the lower, middle and upper Texas coasts. Since the shape
    and size is very nearly conserved for constant radius of maximum
    wind (R) and forward speed (c), a normalization is feasible
    in which surge values for the design hydrograph are expressed
    in terms of percentage of peak surge value. Figure A-2, the
    design hydrograph, shows the rate of rise (and fall) of surge
    heights at the open coast and is the basis for computing the
    distribution of surges inland. It should be noted that the
    rate of fall implied is not real, however, since the retreat
    of inundation is more complex than the advance and involves
    in many uses additional water volume accumulations (rain and
    riverine discharges) and much larger bottom or frictional
    stresses. Therefore, the ebb rate will be distorted, usually
    (but not always) being slower than the computed rate.
    Figure A-3 is a schematic showing spatial distribution along
    the coast and vertical rise prior to landfall.

                            III-A-5

                                               LANDFALL
               HOURI5 BEFORi'E LANDFALL             TIME     HOURS ARER LAND:FALL
            -10     -8      -        -4      -2       T.      42      +4      +6
                     I   I   jI      I                        I

    \                         I

       ioo -

    -so
                                                                    Io/

                HURRICANE  TI           MACK

                                    ,8           ,/

    Z 150-

                                    FIGURE A,2
              TIME HISTORY OF OPEN COAST STORM SURGE HEIGHTS FOR DESIGN
              HURRICANE,  (THIS IS A NORMALIZED HYDROGRAPH
              SURFACE EXPRESSED IN TERMS OF PERCENTAGES PEAK SURGE
              ENVELOPE GIVEN IN FIGURE A,1)
                                    III-A-6

                                 f it~~~~~~~~~bi
                                    1J

                             ,9~~~~~~~~~~~~~~~N

                              FIGURE A-3
    SCHEMATIC SHOWING RISE OF SURGE ALONG OPEN COASTLINE BEFORE
    LANDFALL AND SPATIAL DISTRIBUTION ALONG COAST.

                               Ill-A-7

                            ANNEX B

     CONCEPTUAL BASIS FOR COMPUTING INLAND FLOODING

         The Texas coast comprises mainly a chain of barrier
    islands separated from the mainland by narrow shallow bays
    or lagoons, a few of which expand into larger, deeper bays
    or estuaries as in the Corpus Christi, Galveston and
    Matagorda areas. Tides from severe hurricanes will overtop
    portions, if not all, of-most barrier islands, combining with
    the wind-driven shoal waters of bays and estuaries to flood
    the lee shores. The routing of these floodwaters is
    accomplished by using a procedure designed by the Institute
    for Storm Research at Houston, Texas. This procedure
    requires as input:

           1. a hydrograph or chronology of the storm tide
               stages at the open coast for the period 10 hours
               before through 6 hours after hurricane landfall
               (see Figure A-2);

           2.  the hurricane wind field corresponding to the
               hydrograph values for the line of computation.
               This line, which is parallel to and 14 miles
               to the right of the hurricane track, passes
               through the position of tidal maximum at the
               open coast (see Figures B-la and B-lb).

           3. a topographic profile of ground (or bottom) levels,
               relative to mean sea level, extending inland normal
               to the open coast or bay shore (whichever is
               applicable) through the point (Q) for which the
               hazard zone is to be determined.

          The initialization selects the appropriate design surge
    maximum for the coastal point in question (Figure A-l).
    Hydrograph computations to complete Table B-1 are made in terms
    of a peak tidal value comprising the peak surge plus an
    astronomical tide of one foot MSL (2.1 feet MLW), considered
    to arrive at the coast or shoreline coincident with the
    surge maximum. To the computed hydrograph from Table B-1
    is added an invariant value of initial rise, 2.0 feet, to
    obtain the total tidal stage for each time step in the compu-
    tation of inland flooding.

          For flood routings across land, or over inland water
    surfaces less than 5.5 feet deep (MSL), the line of computation
    is positioned to pass through (Q) and to cross the open
    coast (P) at right angles (see Figure B-2).

                              III-B-1

                                 / --                                       - 20
                             t   4

            140 -     t             ~~~~TEXAS  DESIGN HURRICANE               -1
                                      Surface Wind and Inflow J
            s 120 Z  <  t              {Q~~~~~(uass-Stationary System )         1

     100 - |             \--10
     180                   I                                                   -18

         Z~~~~~~~~

     160                 1                                                       166
                       I
                      UI

      40 4

      2 0  Ife                                                                   2

             10   20   30  40       50    60   70   80    90   100  t11

                             RADIAL DISTANCE FROM CENTER R ( mi.)

                                   FIGURE B-1A
          COMPOSITE WIND FIELD FOR THE TEX AS DESI GN HURRICANE           FOR

        A QUASI-STATIONARY SYSTEM BASED UPON SPLASH II COMPUTATIONS.

        The actuaZ wind field (Figure B-lb) accounts for the hurricane movement
        by addition of a component of movement nC, where C is the vector of
                      U

            movement (down trfack)e Wind n is      a     ndt in  the SPLAS

        model.

                                      III-B-2
            -120-                      ~~~~~~~~(Ouasi- Stationary System)      - 01

                                                                            0
    L,                        10-'10 -L.3

     80'

                 I
                 I

         60-  2    0    3        0 5        07          0 9        0     1
                     ~~RAIAD I TNEFOCETR(m.

                      ~~~FIGUEB1
              CMOITWNDFEDFRTETXSDSGHURCEFR
          A QUAS~I-TTNAYSSEBAEUPNSLSIICOPTIN,
       40   cua   id  il F igr B-4bconsfrtehriaemvmn
          by add~itino      opnn   fmvmn ,weeCi h etro
          moemn (on  rck ndnisaemiilcofceninteSLH
            moe.
                     I~~~~~~~I--

                             (mph)

                           II
           � � - *+1' .....-' '3'1.
     � lomi.            *    .33 ' .

             . � � - ' * ' ......-:*. 39....    *-..
       .80'
                         .-- '42

                   l,�   i    5 ,                 .         ,     i,
                            Ioe
            .40               76. '.

                ,20'
        i   .'      X     ,      *-.        *'.      '.        *
                  .    .' . J    59 '.                 I

                               106

                            70

              --....,         .. 51

                            1  (mph)

                               FIGURE B-lB

    COMPOSITE WIND FIELD FOR THE LINE OF COMPUTATION USED IN

      THE TEXAS DESIGN HURRICANE MOVING INLAND AT 14 KNOTS.

                                   III-B-3

                           .  ~~~~~~~~~~4. & ........ . .
                                  ... *.d...

                                  ... ..+4 H."
                .... .......~~~~~~~~~~
                ... ...........~~~~~~~~
                   .. .......... .... .. ..... .... ..
                        ............ ...~~~~
                ............ ......
                      .................... .  ......
                .. ....... . ....
                  .... ...........2
             ...... ~ ~      I~  ............
              ..........~ ~        ............

                ..........~~~~~~~~~~~~
             .......  . ...L
              ..........14 mi.
          GULF...
             ........FGUR.B-
     ORENATONOFLIE  F  OMUTTIN  ORDITRBUIN  OE
    COAST. ...IAN  TIE.NADADOE  SOLILN   AEWY

                           Landfall11-8-

         For flood routings across bays or estuaries of
    greater depth, the tilting up of the water surfaces at lee
    shore due to wind setup may bring even larger inundations
    than at the open coast if severe hurricane winds operate
    on the water surface for 90 minutes or more. (In Carla
    inland flooding reached the 22 foot level, while tidal
    maxima at the coast were only about 15 feet.) Therefore,
    a special computation procedure is used for determining the
    surge maximum due to wind setupt. This surge maximum,
    physically determined, is a function of the water depth (MSL)
    and an optimal distance over which hurricane winds can operate
    on the shallow water basin. Procedures for these computations
    are contained in Annex C. A sample computation sheet is shown
    in Figure B-3.

         The computation procedure uses a chart similar to that
    in figure A-2. This is an x-t diagram where the x-axis
    is the line of computation directed landward. The t-axis
    extends from -10 hours (before landfall) to +6 hours. The
    initial input is based upon the expected peak surge value
    selected from Figure A-l, the computed hydrograph for the
    open coast (x=O, t=-10 to +6) from Table B-l, and the wind
    history accompanying the hydrograph (Table B-2). Hydro-
    graph points (for -10 H to +6H) are computed at 7.5, 15, or
    30-minute intervals depending upon the length of spatial
    steps on the x-axis. The spatial computation intervals
    used are a function of the distance inland of point Q and
    range from 1 to 4 miles.

    ROUTING OF RAINFALL RUNOFF

         The design hurricane expects a rainfall of 8 inches
    uniformly distributed over a semicircular area 28 miles
    in diameter extending landward from point P and occurring
    at a uniform rate during the 4-hour period prior to the
    arrival of the peak storm tide at point Q.

         It is assumed that initially river and stream levels
    are normal, that prior to the beginning of heavy rains
    (4 hours before the hydrograph peak is reached), the
    rainfall saturates and is largely absorbed by the soil, and
    that normal drainage systems are functional. During the
    last 4 hours, the rapid hydrograph rise due to saltwater
    intrusions blocks the urban and natural drainage systems
    for fresh water accumulating at point Q.

         For purposes of this computation, the contributions of
    riverine flooding over the short period of hurricane approach
    are considered small and thus incorporated in the value of
    the initial rise. The rainfall runoff cannot be dismissed

                              III-B-5

                                     TABLE B-1

                              TEXAS DESIGN HURRICANE

    The wind field lies along a line parallel to the track and passing through
    the tidal maximum, from 10 hours before until 6 hours after landfall. If
    this line is defined as the x-axis increasing downtrack, 0 is the angle which
    a wind vector observed on this line makes with the line, positive when
    measured counterclockwise from the x-axis. (Based upon hydrograph and
    computed winds from SPLASH II program [Jelesnianski, 1972], using TEXAS
    DESIGN HURRICANE parameters.)

                LANDFALL            SURFACE WIND          OPEN COAST TIDE

           Distance   Time    Speed        Track        Fraction  Hurricane
            D(mi)    (Hours)  W(mph)    Crossing         of Max      Tide
                                        Angle e (deg)               N(MSL)

            -140      -10.0      22         80.1          .00
            -133      - 9.5      23         81.0          .005
            -126      - 9.0      24         81.9          .01
            -119      - 8.5      25         82.7          .015
            -112      - 8.0      27         84.3          .02
            -105      - 7.5      29         85.5          .023
            - 98      - 7.0      31         86.5          .025
            - 91      - 6.5      33         87.3          .027
            - 84      - 6.0      36         88.4          .030
            - 77      - 5.5      39         89.2          .040
            - 70      - 5.0      42         89.7          .05
            - 63      - 4.5      47         90.1          .075
            - 56      - 4.0      51         90.5          .10
            - 49      - 3.5      59         89.7          .16
            - 42      - 3.0      66         88.2          .22
            - 35      - 2.5      76         85.1          .26
            - 28      - 2.0      85         79.1          .30
            - 21      - 1.5    103          68.0          .45
            - 14      - 1.0    123          50.2          .60
            -  7      -  .5    134          31.6          .85
               0        0.0    137           2.2         1.00
               7        0.5    134         -26.0          .85
              14        1.0    124         -43.7          .60
              21        1.5    106         -46.0          .40
              28        2.0      89        -46.3          .20
              35        2.5      81        -47.9          .12
              42        3.0      70        -49.3          .05
              49        3.5      63        -50.6          .025
              56        4.0      56        -51.6          .00
              63        4.5      51        -52.9        - .05
              70        5.0      46        -53.6        - .10
              77        5.5      43        -55.2        - .07
              84        6.0      40        -54.8        - .03

                                       III-B-6

                                                     TABLE B-2
                              WIND HISTORY FOR TEXAS DESIGN HURRICANE
    Based upon SPLASH II Stationary System Wind Field Corrected for Design
      Hurricane Movement.

                                                                                            MOVING
                                   QUASI-STATIONARY SYSTEM                                     SYSTEM

               R     W      6          D       t                 6'                    W               W
             (mi)  (Kt)  (deg)       (mi)  (hours)      tan   (deg)            s         s   (deg)   (Kt)
                                                    -(deg)           (tan + 6')  Kt

                4    78   0.44    -140    -10.0   85.1          13.3        98.4       22    80.1      22

                8   119   1.18    -133    - 9.5   84.8    13.7              98.5       23    81.0    23

               12   130   2.27    -126    - 9.0   84.6    14.2              98.7       24    81.9    24

               16   124   4.04    -119    - 8.5   84.2          14.7        98.9       25    82.7    25

               20   114   6.67    -112    - 8.0   83.9    15.3              99.2       27    84.3    27

               24   103  11.21      -105    - 7.5   83.5        15.9        99.4       29    85.5    29

               28    94  15.32    - 98    - 7.0   83.0    16.5              99.5       31    86.5    31

               32    85  17.77    - 91    - 6.5   82.5    17.0              99.5       33    87.3      33

               36    78  19.14    - 84    - 6.0   81.9    17.7              99.6       36    88.4      36

               40    71  19.88    - 77    - 5.5   81.1          18.4        99.5       39    89.2      39

               44    66  20.24    - 70    - 5.0   80.3          19.0        99.3       42    89.7    42

               48    61  20.34    - 63    - 4.5   79.2          19.5        98.7       47    90.1    47

               52    57  20.28    - 56    - 4.0   77.9    20.3              98.2       52    90.5      51

               56    53  20.10    - 49    -3.5   76.2    20.3               96.5       59    89.7      59

               60    50  19.87    - 42    - 3.0   74.1          20.2        94.3       66    88.2    66

               64    47  19.57    - 35    - 2.5   71.1          19.3        90.4       76    85.1      76

               68    44  19.22    - 28    - 2.0   66.8    17.0              83.8       84     79.1     85

               72    42  18.86    - 21    - 1.5   60.5          11.4        71.7      101    68.0   103

               76    40  18.46    - 14    - 1.0   49.4           3.4        52.8      119    50.2   123

               80    38  18.11      -  7    -0.5   30.3          2.9        33.2      128    31.6   134

               84    36  17.81          0       0       0        2.3         2.3      130      2.2   137

               88    35  17.43          7       0.5  -30.3       2.9      -27.4       128   -26.0   134

               92    33  17.07         14       1.0  -49.4       3.4      -46.0       119   -43.7   124

               96    32  16.71         21       1.5  -60.3    11.4        -48.9       101   -46.0   106

              100    31  16.36         28       2.0  -66.8    17.0        -49.8        84   -46.3    89

              110    28  15.51         35       2.5  -71.1      19.3       -51.8       76   -47.9    81

              120    25  14.73         42       3.0  -74.1      20.2      -53.9        66   -49.3      70

              130    23  14.00         49       3.5  -76.2      20.3      -55.9        59   -50.6      63

              140    22  13.32         56       4.0  -77.9      20.3      -57.6        52   -51.6      56

              150    21  12.83         63       4.5  -79.2      19.5       -59.7       47   -52.9    51

                                      70       5.0  -80.3    19.0        -61.3        42   -53.6    46

                                      77       5.5  -61.1      18.5      -63.6        39   -55.2    43

                                      84       6.0  -31.9    18.0        -63.9        36   -54.8    40

                                                      III-B-7

                         Hurricane Tidal Inundation
                           Computation Sheet

            +61    '  .

            +2    * : :    :         *   *   *   *   *

            +1 � � � � � � � � *

             O *   � � * 0  �   e�

          0 -1     * �   �   �   �   �   �   �   �
          o        �*   �   �   �   �   �   �   � �
          I  -2    �   �   �   �   �   �   �   �   �
          w         .   .   .   .   .   .   .   .   .

            -10    *   *   * �       *   *   * �   �

                             DISTANCE (Miles)
                  +20    4   8   12  16  20  24  28  32  36  40
            +20                                              +20

            +10                      .    . .-  +10
          -J
          U-
          0
          a- MSL                                             MSL
          w
          0

          U)
            -10                                              -10

            -20
                  4   8   12  16  20  24  28  32  36  40

                             FIGURE B-3

    BASIC COMPUTATION SHEET AND VERTICAL SECTION FOR CONSTRUCTING

    PROFILES OF MAXIMUM FLOOD HEIGHTS INLAND FROM THE OPEN COAST

                               III-B-8

    so easily, however. While this contribution is acknowledged
    as likely to vary appreciably with topography, for purposes
    of this computation the freshwater contribution is considered
    to be 0.7 feet. This value is added directly to the maximum
    saltwater depth computed for point Q to determine total
    flooding levels.

                              III-B-9

                             ANNEX C

        PROCEDURES FOR COMPUTING INLAND FLOODING

         Annex B explains the conceptual basis for computing the
    inland flooding due to storm surges. This annex sets forth the
    procedures which, if followed closely, will provide the
    computational results which are fundamental to the effectiveness
    of this program. These procedures draw upon many different
    sources of competence to compute flooding levels and identify
    in which hazard zone a proposed building site is located. The
    final determination of the hazard zone must combine the maximum
    computed flooding level at the building site (Q) with the prima
    facie factors identifying the hazard zones specified on
    pages III-5 through III-8.

          1. FORMULATION SUMMARY. The procedure for routing
    storm tidewaters inland computes the flux from the equation for
    steady-state flow. This includes the forces due to (1) wind
    stress on the water surface, (2) gravity action due to the mean
    slope of the water surface, and (3) bottom stresses given by
    Mannings formula. A hydrograph is computed for successive
    space steps, xl to xn, along an x-axis extending inland from
    the point of maximum storm tide at the beach or shore (P),
    passing through Q, the site in questions. The procedure solves
    the equation

                        NA = NB + K3 [P(C,R) - P(L,C)]               (1)

    where the tidal flux for a given time step is NA - NB. This
    computation derives from the function

           P(l,r) = /Kl(h'-hg)lU"/3(Nr-N1) + K2W2cosO(h'-hg)7/3       (2)

    expressed relative to the grid array

                              N1            Nr

                              0             0

                             hgl           hgr

    The total water depth (h' - hg) = (Nr - hgr + N1 - hgl)
                                          2          2

    Symbols and constants are defined on page III-C-16.

          In (2) if the quantity under the radical is defined as B,
    the convention is that P(l,r) = /B if B is positive
                                  = -vC-  if B is negative

                              III-C-1

         To simplify computations, it is assumed that all terrain
    is initially covered by 0.2' of water, so that for all time
    periods before surge waters have extended inland to a position
    xi, for which a hydrograph is being computed, the value of N
    (water level above MSL) is 0.2' greater than hg (terrain level
    MSL).

         The maximum storm tide at xi is obtained from the
    computed hydrograph for xi and plotted on a vertical cross
    section of Nmax vs. x to obtain the profile and inland extent
    of saltwater flooding. To the water depth at Q obtained from
    this profile is added the accumulation of fresh water from
    rain runoff, nominally 9.7 ft., to obtain the computed depth
    of flooding at Q. Finally, the design depth at Q is considered
    to be the computed depth if greater than that which would exist
    in terms of the floodplain level established by FIA. If lower,
    the design depth will be equal to that defined by the floodplain.

          2. CLASSIFICATION AND INITIALIZATION.

              2.1  Locate the building site Q on a coastal map.
                   Select a map preferably with a scale of
                   I"   2000 ft., but not smaller than
                   l" = 1 mile. Contours of elevation (and for
                   inland waters the bottom depths) should have
                   a resolution of not less than 5 feet.

                   2.11  Draw a line through Q normal to the bay
                         shore or coastline terminating at
                         point P, tne water's edge at MSL.

                   2.12  Measure the distance S from point P to
                         point Q in tenths of miles, and the
                         elevation H' (MSL) for point Q.

              2.2 Select the appropriate space and time increment
                   (Ax, At) for making computations.

                   2.21  If S is 12 (statute) miles or more, use
                         the following increments: Ax = 4 miles;
                         At = 30 min.

                   2.22  If S is greater than 6 miles, but less
                         than 12: Ax = 2 miles; At = 15 min.

                   2.23  If S is 6 miles or less:  Ax = 1 mile;
                         At = 7 1/2 min.

              2.3 Construct and label an appropriate computation
                   sheet following the example in Figure B-3.

                               III-C-2

    2.31  If P is located at a narrow barrier
          ridge or continuous line of dunes, the
          computation will begin with the time
          step at which the surge height N is
         just below the mean height of the ridge.
          Conceptually, the ridge is regarded as a
          sill over which surge waters upon
          reaching that height cross freely
          and quickly. For other circumstances
          the procedures in 2.32-2.34 apply.

    2.32  If Ax = 4 miles the computation will
          nominally be conducted for x = 0 to
          nAx, where n is the integer (S/Ax) + 1,
          and from t = -10 to +6 hours (unless
          started later due to terrain conditions
          in 2.321).

          2.321 If terrain rises rapidly at the
                 shore to a height of hg � 6 ft. MSL,
                 the computations will begin at
                 the hydrograph hour most nearly
                 corresponding to a tidal stage
                 equal to hgo - 0.5', where hgo is
                 the mean height of terrain
                 immediately adjacent to the shoreline.

    2.33 If Ax = 2 miles, the computation will be
          conducted for the time interval:

               -5 to +3 hours,
               or t(hg) to +3 hours

          whichever is shortest. Here t(hg) is
          the time the hydrograph at P reaches
          the height N(t) = hgo - 0.5'.

    2.34  If Ax = 1 mile, the computation will be
          conducted for the time interval:

               -3 to +1.5 hours,
               or t(hg) to +1.5 hours

          whichever is shorter. t(hg) is the time
          the hydrograph at P reaches a height of
          hgo - 0.5'.

    2.35  When a computation begins at a new time
          step the value of N for x1 to xn should

               III-C-3

                         SAY SHO2EINUN DAT ION

         .%.........

     .....~~~~~   * . .. .....  . **  . . .... .... .. .  .  .:~..
       .. ..... ...... *    U FAA...P..                                      ..
                         ..........~~~~~CA5  ....S............G.......

              ..........IGUR  .............................
    ORIENTATION....... ... ......... ... COPUATO  ... ROTIGCOSTLSUGE.NLN
      ACROSS LARGERBAYSJ.......  COMPTIN  BA  .HR  INNAIN......................
                                            III-C-4.... .......... ..

              not be less than

                    (a)  hg + 0.2', or

                    (b) 2 ft., MSL, or

                    (c) half the value of N at x = 0
                        whichever is largest.

    2.4  From Table B-2 record the appropriate values of 0
         and W to the left of each time step on the
         computation chart, Figure B-3.

    2.5  Compute the hydrograph for xo.  If P is at an
         inland shore where mean water depths across the
         bay are at least 5.5 feet MSL, proceed to 2.53;
         if P is at the open coast, proceed as follows:

         2.51  From figure A-1 determine the maximum surge
               height (feet and tenths) for the Texas
               Design Hurricane at the coastline
               position nearest to P.

         2.52  To this surge height add 1.0 feet (astro-
               nomical tide increment). Using the sum
               as the peak open coast tide (MSL) compute
               the hydrograph values for each time step
               in Table B-1. Proceed to step 2.54.

         2.53  Compute the equilibrium tilt of the water
               surface in the bay (see Figure B-2).

               2.531  Select a point at the open coast, 0,
                      which (1) maximizes the distance OP
                      (this line need not be normal to the
                      coastline), and (2) is centered in
                      a major pass connecting the ocean
                      with the inland waters, or alternatively
                      is centered on an 8-mile stretch of
                      coast where the barrier island, dunes
                      or stable terrain, offers the lowest
                      mean elevation to block movement of
                      the open coast surge.

               2.532  Compute the equilibrium height of
                      water surface Nx at point P as a
                      function of distance S' from 0 to P
                      and of mean water depth (below MSL) H.

                    III-C-5

                               Use the formula Nx(ft.) = l0.58S' + T
                                                          H + h
                               where h is the initial rise E 2 ft. MSL
                               and T, the astronomical tide E 1.0 ft.
                               MSL. H is taken as the mean depth MSL
                               for a strip 2 miles wide extending
                               from 0 to P.  Nx is the peak storm tide
                               at P.

                        2.533  Enter Table B-1 with the peak tide value,
                               Nx; compute the hydrograph values for
                               each time step. To this add the
                               initial rise 2.0 ft. and enter the sum
                               N(t) on the computation sheet. Proceed
                               to step 2.6.

                  2.54  Add the height of initial rise (2.0 feet) to
                        the hydrograph values computed in 2.52
                        and record the sum at each respective time
                        step for x = 0 on the computation sheet.

             2.6  Compute hg and N for each space step xj.

                  2.61  From the map contours (2.1) plot a profile
                        of terrain heights (or shoal water depths)
                        from P inland to a point at least one
                        space step beyond point Q where hg must be
                        more than 1 ft. above N at the previous
                        space step; or for very flat, low terrain,
                        at least 8 miles beyond Q.

                         hg should be representative values for the
                        area, nominally the mean hg's whose width
                        extends one half mile to either side of
                        the x-axis.

                  2.62  On the computation sheet at the initial
                         time step, record the value of hg for each xj.

                   2.63  Above each hg value record the value of N,
                        where N E hg + 0.2' except where hg + 0.2'
                         is less than the initial rise (2.0' MSL).
                         In the latter case N E 0.2'.

          3. COMPUTATIONS OF HYDROGRAPHS FOR SUCCESSIVE SPACE STEPS
    INLAND. The computation sheet, similar to figure B-3, now has
    appropriate initial values of W, 0, and N for x = 0 (point P) at
    each time step, and values of hg, and for N at the initial time
    step for each space step, x1 to x,.  The next step is to compute
    hydrograph values of N for each time step at xl, x2----xn.  Each

                              III-C-6

    computation uses the graphic convention below:

                                     NA

                              NL     NC      NR

         [tj, (W,O)j]        a       e e

                             hgL    hgc    hgR

                                     0

                                     NB

                                    (xi)

              3.1  Convention for computing NA from baseline data.
                   The initial computation, made at (to, xl) uses
                   values of NL, hgL, NC, hgc, NR, hgR already recorded
                   in the initialization. For this baseline compu-
                   tation NB is set equal to NC. Accordingly, the
                   resulting value of N'A must be adjusted so the
                   recorded value is:

                             NA = (NC + N'A)
                                      2

              3.2  Convention for computing successive NA'S for a
                   given time period. After computing NA for
                   position xl, move to the right (inland) computing
                   successive NA'S for the same time period, NR for
                   the first computation becoming NC for the second.
                   When a space step is reached where hgR is more
                   than a foot higher than NC, then for the space
                   step corresponding to this hgR set NA = NC and
                   proceed to the next time step.

              3.3  Compute NA using the HP-65 programmable calculator.

                   3.31  With the calculator "on" in the "RUN"
                         position, insert the program chip for the
                         appropriate space step: 1-, 2-, or 4- miles.

                   3.32  Key in the value of 0; STRIKE C.  Key in
                         the value of W; STRIKE R/S.

                   3.33  Key in NL and store in 2;

                         Key in hgL and store in 3;

                               III-C-7

          Key in NC and store in 4;

          Key in hgC and store in 5.

    3.34  STRIKE A.

    3.35  If hgR is more than one foot greater
          than NC, STRIKE D, then STRIKE B. Proceed
          to 3.37. (This is considered by the
          program as a "cliff effect" and sets
          P(R) E 0.) However, if (hg9R - NC) 5 1.0',
          then

    3.36  Key in NR and store in 4;

          Key in hgR and store in 5.

          STRIKE A (let it finish computing!)

          STRIKE B

    3.37  Key in NB

          STRIKE R/S

          The displayed value is NA.

    3.38  Compute the next NA to the right (inland).

          3.381  Let NR and hgR in 3.36 become NC
                 and hgC, then moving to the right
                 for a new NR and hgR:

          3.382  Key in NR and store in 4;

                 Key in hgR and store in 5.

                 STRIKE A (see 3.35 for exception)

                 STRIKE B

          3.383  Key in NB.

                 STRIKE R/S

                 The value displayed is the newNA.

          3.384 Continue to the right until
                 (hgR - NC) > 1.0 ft., then set NA = NC.

                III-C-8

        3.39 Go to the next time step, key in new values
              of 0 and W, and proceed as in 3.32 and 3.33.

              3.391 In order to maintain computational
                     stability:

                     3.3911 For time steps following t = 0,
                            when (NC - NA) becomes greater
                             than 1 ft., then for all succeeding
                             time steps the convention
                             requires that NA 5 NC.
    3.4 Compute the profile of saltwater flooding inland.

         3.41  Identify the highest value of N computed for
              each space step inland. This will come at
               positive time values (following t = 0) and
               at successively later hours for each succeeding
               space step.

         3.42  Plot values of Nmax for each space step on
               the N/x cross section at the bottom of the
               computation sheet (see Figure B-3) and draw
               the flood profile.

         3.43  From the profile read the inundation depth
               at Q due to saltwater inundation.

         3.44  To the above value add the design value of
               freshwater flooding, 0.7 ft. to obtain
               the total flood level D for point Q.

         3.45  Determine the legal floodplain height
               established by the Flood Insurance
               Administration (HUD) for Q.

               3.451 The flooding at Q due to F is
                      defined as D' = F - hgQ. If D' > D,
                      set D = D'.

               3.452 D 0 design flooding at Q.

    3.5 Compute NA using the ISR nomogram (figures C-2 and C-3).

         3.51 Using the lower portion of the nomogram,
               locate the intersection of the horizontal
               line for 0 values and the vertical line
               for W; designate this A.

                    III-C-9

                      100:~~~~~~~~~~~~~

       80-                            a                       j I
                               70-  * ~~~~~~   I  g II~~~~~~ *~~~  I  I   ' ~ ~     ~      ~     -4
                                        5 ~~~~~~~~~~~ ~ ~~~~~~~~~~~~~~~~~~~~~~~3            I I
       60-                      1               -        I
       50-    I     5 11 a
                 I               I                I-
       40-                                           -->                                                                        -
           3-                       .     ~      1       1    1-                     -

          20-   16~~    I8 20I    3 0 -

                  50-~~~~ -       It*I

           60 -

                                                                    '0 .

    either~~~ p s        or                        k                             %

                           N                           k-        'g,'A 'V".         'k
    ne.,a id-             II   \'uj~
      cated
                          2b 3 4       0      5        607  010          6 6 0
                             I  '~~~~~kot
                   +go-~~~~~~~~Il

                                     S? I ~         lc                                                   S         C                                                             S)          S OD~m

    '(hR(-hL) feet                 0                'S:v                        -:

                                                 I     I      I*  I                                 s  :-
                                                  I    I   I         I Ii          I            I         *B
                                     100-       * L                 I   ,         I               I
                                          100-  1      I    II    I    *  3151             I        I     I
                                             -   S        I   I 5   I II                   I        I      I
                                      80- :           a    a   ,   a    a   I                      u      s
                                      70-       1     I    I   *  Urn  ,                           I
                                      60-       I     I    I   a   I~ ~I                  I        I      I
                                      60-      ~      S    I S' 5
                                                 I     I    I       1  I  I  g             I        I      I
                                      40-             ~,                 *
                                            I0         I    UI      Ilg                    I--    I        I

                                      30-       *        I   I    II  a            I               I      I  -
                                                -I     I    I   I  Ii  *I   -                       I    -I
                                      20-       I            I  I  II     I               I        I

                                           -     I     I

                                                 -       -                                                                                                                             0 -   a - L L   1  -  I

                                                             I            I ~II         tI          I           I� -
                                                 -     I    .4   1   I                           '.       '      .  4(

                                                                            S~ ~ ~~~~~~ ~~~~~~~          ~   ~~ ~   ~~~~. .4~ ..~.4 .4 .....
                                                       4- ~ ~ ~ ~   ~    ~    ~    ~ ~ ~ ~ ~ ~ ~ .
                                               10:~~~~~~S 1_  �               �;          I   -
                                       3-_               .      .        .4'    .           I     '5        .4        -5

                                                           ~~I-.                      --1~~~~~~~~ i  ;-    ~~~~~~-csP-~S  .
                                       5-

                                               2 0---3.-                I 12   .                                                                                                       '0
                                             3-             1   I~~~~~            ~~~ 1~               ..       .. I
                                                           6c -~I

                                               W~~~~.\ ~                       S\\4-                    ~         5.xu              -NMGA    O    FIGURE C-3
                                        80-                   A -

                              Angles can be                              '     \"                                       "      .

                              either po.oIL   45    .a..                                                                 S      5
                              neg., as  indi-                          "     \
                                                        I  ~~~~~~.'                 55  'S '' S. ~I                                 .4

                                   cated                       2        '
                                                                   2b      30    40    0  6'0 7080   10        10 0 0200        300   4'00

                                                                                        knots

                                             �901

               3.52  Following the slanting lines upward to
                     the left from A to the horizontal line
                     representing the base of the upper
                     nomogram, mark the intersection B and
                     construct the vertical line BC from
                     bottom to top of the upper nomogram.

               3.53  From the computation format in 3.0, compute:

                           (a) (h' - hg)L = (NL - hgL) + (NC - hgc)
                                                       2
                           (b) (NL - NC)

               3.54  On the vertical axis at the center of the
                      upper nomogram, locate the value of (a).
                     Mark this D. Draw a horizontal line DE to
                      the intersection of BC.

                3.55  From E follow the diagonal thin lines to
                      point F on the prominent horizontal line
                      located one third the distance from B to C.

                3.56  At the top of the upper diagram locate the
                      value of (NL - NC); mark this G. Drop
                      vertically to the line DE (extended if
                      necessary) and mark the point H.

                3.57  From H move diagonally and parallel to the
                     white stripes to the intersection of the
                      vertical white stripe. Mark this point J.

                3.58  Move horizontally from point J and vertically
                      from point F to the intersection. Mark this
                      P(L). Read the value of P(L) from its
                      interpolated position between those hyperbolas
                     which extend from left to right sloping
                      downward to intersect the base of the upper
                      nomogram where their values are recorded.*

                3.59  From the computation format in 3.0, compute

                           (a) (h - hg)R
                           (b) NC - NR

                      With these values repeat the computations in
                      3.54 and 3.58 to determine the value of P(R)

    If P(L) lies on the left side of the split nomogram (negative
    values) then interpolate its value between the hyperbolas which
    extend from right to left curving downward to intersect the
    baseline.
                           III-C-12

                   3.60 Compute:

                              NA = NB + K3(PR - PL)

                   3.61 Continue computing successive NA'S to
                         the right (inland) for the same time step
                        as in 3.2.

                   3.62 Complete the profile of saltwater flooding
                         as in 3.4.

                   3.63 Add the freshwater accumulation to the salt-
                        water flooding in 3.62 to determine the
                        total flooding, D. Proceed as in 3.45 to
                        obtain the design flood depth.

         4. SAMPLE COMPUTATION OF NA. From the computation sheet
    values in figure B-3, the following is a sample computation of NA
    for the step t = -0.5 hours, x = 4 miles.

             4.1 The array of known values (Figure B-2) is:

                                    NA = ?

         0 = 31.6�      NL = 11.04'   NC = 5.26   NR = 8.7'

        W = 134 mph   hgL = 2.0'    hgc = 2.0'  hgR = 8.5'

                                    NB = 4.18'

         (At   30 min.; Ax = 4 mi.)

             4.2 Compute NA using the HP-65 program.

                  4.21 With HP-65 "on" and in "run" mode, insert
                        the program chip for x = 4 mi.

                  4.22 Key in 6 = 31.6�

                        STRIKE C--------(read 0.85)

                  4.23  Key in W = 134

                        STRIKE R/S-----(read 3.06)

                  4.24  Key in NL = 11.04, store in 2;

                        Key in hgL = 2.0, store in 3;

                        Key in NC = 5.26, store in 4;

                        Key in hgC = 2.0, store in 5.

                              III-C-13

              STRIKE A-----.(read 2.00)

         4.25  Since (NR - NC) > 1.0' (cliff effect)

              STRIKE D---.- (read 0.00)

        4.26  Key in NB = 4.18

               STRIKE R/S -----(read 7.17')

              This is the value of NA.

    4.3 Compute NA using the nomogram.

         4.31 From the computation format in 4.1, compute:

               (h' - hg)k = (NL - hgL) + (NC - hgC)
                                       2
                          = 9.04 + 3.26 = 6.15'
                                  2

                (NL - NC) = 5.78'

         4.32  Locate 0 = 31.60 on the vertical axis,
               lower nomogram. Draw a line horizontally
               to the right. Locate W = 134 on the
               horizontal axis, lower nomogram; draw a
               vertical line upward to intersect the 0
               value at A.

         4.33  Move diagonally to the left from A parallel
               to the slanting lines to B, the base of the
               upper nomogram. Draw a vertical line BC to
               the top of the upper nomogram.

         4.34  Locate (h - hg)L = 6.15 on the vertical axis
               at center of the upper nomogram. Mark this
               D and draw the horizontal line DE to intersect
               BC.

         4.35  Follow the diagonal thin lines downward to F,
               the intersection with the prominent horizontal
               line 1/3 the distance from B to C.

         4.36  Locate NL - NC = 5.78' on the horizontal line
               at top of the upper nomogram. Mark this G,
               and draw GH vertically downward to the
               intersection of DE.

         4.37  From H move diagonally to the right parallel
               to the white stripes to J, the intersection
               with the vertical white stripe.

                    III-C-14

    4.38  From J move horizontally and from F
          vertically to the intersection K.

    4.39  Now following the family of hyperbolas
          enclosing K moving from left to right and
          sloping downward to the base of the upper
          nomogram; interpolate the value of K to
          be 17.5 P(L).

    4.40  Since (hgR - NC) > 1.0 ft., P(L)   0.

    4.41  (NA - NB) = K3(0 - 17.5)
                    = -.17(-17.5) = +2.98

    4.42  NA = NB + 2.98

             = 4.18 + 2.98 = 7.16'

                  III-C-15

                   DEFINITION OF SYMBOLS

    N: height of water above MSL

    hg: elevation of terrain above MSL (+), or bottom depth below
         MSL (-)

    Subscripts C, A, B, L, R, referred to N and hg, represent values
          centered, one step above, below, and to the left and right
          of a given time and space step, respectively.

    Subscripts 1, r refer to any left and right grid points later
          referred to as L, C, and R

    xi: a computation point on the x-axis from x = 0 to x = n

    0: the angle which the wind vector makes with the x-axis measured
          counterclockwise from the axis

    (h' - hg): total water depth

    S: distance inland of the building site

    S': distance across an inland body of water from the open coast,
          point 0, to the bay shore, P

    H': elevation of point Q MSL

    H: mean depth of an inland body of water over a strip 8 miles wide
          along the line OP

    h: initial rise defined as 2.0 feet MSL

    T: astronomical tidal component at time of max surge, defined as
          1.0 feet MSL, 2.1 ft. MLW

    CONSTANTS

    K1 = -.02

    K2 = +.001

    K3 = -.17

                              III-C-16

    COMPUTATION OF HYDROGRAPH TIME STEPS NA WHERE At = 30 min.;
    Ax = 4 mi.

    Program listing for HP-65:

    STEP NO.           KEYS                     STEP NO.            KEYS

        1              LBL                         26               (-)

        2              A                           27              RCL 3

        3              RCL 8                       28               (x)

        4              STO 7                       29               (.)

        5              RCL 2                       30              0

        6              RCL 3                       31              4

        7              (-)                         32              CHS

        8              STO 6                       33               (x)

        9              RCL 4                       34              STO 2

       10              RCL 5                       35              RCL 6

       11              (-)                         36              2

       12              RCL 6                       37               (.)

       13              (+)                         38              3

       14              2                           39              3

       15              ()                          40

       16              STO 6                       41              5

       17              3                           42              RCL 1

       18              (.)                         43              X

       19              3                           44              RCL 2

      20              3                           45              (+)

      21              [1                          46              STO 3

      22              5                           47              [g-

      23              STO 3                       48              6

      24              RCL 4                       49             E

      25              RCL 2                       50              9
                                III-C-17

    STEP NO.           KEYS                     STEP NO.            KEYS

       51              STO 2                       76              C

       52              RCL 3                       77             E

       53              RCL 2                       78              5

       54              (.)                         79              STO 1

       55              STO 8                       80              R/S

       56              RCL 4                       81              ENTER

       57              STO 2                       82              (x)

       58              RCL 5                       83              (.)

       59              STO 3                       84              0

       60              RTN                         85              0

       61              LBL                         86              0

       62              B                           87              2

       63              RCL 8                       88              (x)

       64              RCL 7                       89              RCL 1

       65              (-)                         90              (x)

       66              (.)                         91              STO 1

       67              1                           92              RTN

       68              7                           93              LBL

       69              (x)                         94              D

       70              STO 6                       95              RCL 8

       71              R/S                         96              STO 7

       72              RCL 6                       97              0

        73              (-)                         98              STO 8

        74              RTN                         99              RTN

        75              LBL                        100              il NOP

                                 III-C-18

                         SECTION IV                - ?7,

                MODEL MINIMUM STANDARD    S              .

                        CHAPTER 1

                       INTRODUCTION

    SECTION 1.1 PURPOSE

    1.1.1 APPLICATION: This document is intended to serve as an
    amendment to the City Building Code in Hurricane Hazard Areas.
    The provisions contained herein, along with the legally adopted
    City Building Code shall constitute the minimum building
    standards and requirements. In case of conflict between the
    two documents, the most severe requirement, in the judgement
    of the building official, shall control.

    SECTION 1.2 OUTLINE

    1.2.1 ADMINISTRATION AND DEFINITIONS: Chapters 2 and 3 define
    terms and describe implementation procedures including permits,
    inspection, notice of hurricane hazard, and classification and
    posting of buildings. Classification and posting of a building
    declares if the building is safe refuge. In applying for a
    permit for construction, the owner states the type of hurricane
    floodproofing desired (from completely floodproof to non-floodproof),
    and the completed building will be posted accordingly. Due to
    construction requirements, some of these buildings may be
    designated and used for safe refuge for vertical evacuation.

    1.2.2 DEFINITION AND DELINEATION OF HURRICANE HAZARD ZONES:
    Chapter 4, along with Annexes A, B and C, defines the various
    hazard zones and sets out computational procedures for the
    determination of the zones.

    1.2.3 DESIGN PARAMETERS: Chapters 5, 6, 7 and 8 set out the
    specific design requirements for each hazard zone.

                   Chapter                      Item

                      5                   Wave and Scour
                      6                   Battering by Debris
                      7                   Flooding
                      8                   Wind

    1.2.4 STRUCTURAL INTEGRITY: Chapters 9 through 15 set out
    specific requirements for various types of construction.

                   Chapter                       Item

                      9                   Foundation
                     10                   Masonry
                     11                   Steel and Iron

                                IV-1

                                                      SUBJECT TO RK  iIO'
                   Chapter                        Item

                     12                    Wood
                     13                    Concrete
                     14                    Cladding and Glazing
                     15                    Roofing

    SECTION 1.3 USE: In summary, if one wanted to construct a building,
    the following steps would be required:

    1.3.1 Refer to Chapters 2 and 3 for application information and
    legal procedures.

    1.3.2 Refer to Chapter 4 to determine the hazard zone for the
    particular location.

    1.3.3 Refer to Chapters 5, 6, 7 and 8 for design requirements
    depending upon hazard zone:

                    Zone                Design Requirements

                                              Chapter

                                        5     6     7     8
                      A                  X     X     X      X
                      B                        X     X      X
                      C                              X      X
                      D                                     X

    1.3.4 Refer to Chapters that cover specific construction materials:

    Type of Bldg.           9     10      11     12      13     14     15

    Light-Gauge Metal
      Building              X             X              X       X      X
    Frame House             X                     X      X       X      X
    Concrete Block
      Building              X      X                     X       X      X

    SECTION 1.4 CONTINUING UPDATE OF CODE:  This document is not a
    perfect work. A continuing effort will be made to keep the
    requirements in line with new knowledge and actual experience.
    Therefore, the user is urged to continually update the provisions
    of this code as information is documented.

                             CHAPTER 2         UJ

                         ADM IN ISTRAT ION              Ii

    SECTION 2.1 PURPOSE

    2.1.1 APPLICATION: The provisions contained herein shall
    constitute the minimum building standards and requirements that
    are applicable to safeguard life or limb, health, property and
    public welfare by regulating and controlling design, construction,
    and quality of materials of all buildings and structures which
    are or will be located in all lands shown within the Hurricane
    Hazard Area(s). Hereinafter these provisions will be referred to
    as the "Hurricane Regulations" part of "The Building Code," or in
    short as "these Regulations."

    2.1.2 REGULATORY FLOOD DATUM: For the purpose of these Regulations,
    the Regulatory Flood Datum, hereinafter referred to as the
    "RFD," is hereby declared and established for use as the reference
    datum for determining the elevation above mean sea level to
    which flood-proofing protection shall be provided.

    2.1.3 HURRICANE HAZARD AREAS: For the purpose of these Regulations,
    the Hurricane Hazard Areas, as further described in Chapter Four,
    and the RFD are hereby declared and established for use in
    determining Building Code requirements.

    2.1.4 HURRICANE PRECAUTIONS: During such periods as are designated
    by the National Weather Service as being a hurricane warning or
    alert, the owner, occupant or user of a property shall take
    precaution for the securing of buildings and equipment. Canvas
    awnings and swing signs shall be lashed to rigid construction,
    tents shall be taken down and stored or lashed to the ground, and
    such other precautions shall be taken for the securing of buildings
    or structures or equipment as may be reasonably required.

    SECTION 2.2 SCOPE

    2.2.1 APPLICATION: These Regulations shall apply to the construction,
    alteration, and repair of any building or parts of a building or
    structure in the Hurricane Hazard Area(s) of the        (city, town,
    village, etc.)    . Additions, alterations, repairs, and changes of
    use or occupancy shall comply with all provisions for new buildings
    and structures as otherwise required in "The Building Code," except
    as specifically provided in these Regulations.

    2.2.2  NONCONFORMING USE:  A structure or the use of a structure or
    premises which was lawful before the passage or amendment of
    the ordinance but which is not in conformity with the provisions
    of these Regulations may be continued subject to the following
    conditions: (1) No such use shall be expanded, changed, enlarged

                               IV- 3

    or altered in a way which increases its nonconformity. (2) No
    structural alteration, addition, or repair to any conforming
    structure over the life of the structure shall exceed 50 per cent
    of its value at the time of its becoming a nonconforming use,
    unless the structure is permanently changed to a conforming use.
    (3) If such use is discontinued for 6 consecutive months, any
    future use of the building premises shall conform to these
    Regulations. The assessor shall notify the zoning administrator
    in writing of instances of nonconforming uses which have been
    discontinued for a period of 6 months. (4) If any nonconforming
    use or structure is destroyed by any means, including Hurricanes,
    to an extent of 50 per cent or more of its value, it shall not be
    reconstructed except in conformance with the provisions of these
    Regulations. (5) Uses or adjuncts thereof which are or become
    nuisances shall not be entitled to continue as nonconforming uses.
    (6) Except as provided in "The Building Code," any use which
    has been permitted as a special exception shall not be deemed
    a nonconforming use but shall be considered a conforming use.
    (7) Any alteration, addition, or repair to any nonconforming
    structure which would result in substantially increasing its
    hurricane damage or hurricane hazard potential shall be protected
    as required by these Regulations. (8) The Building Official shall
    maintain a list of conforming uses, including the date of becoming
    a nonconforming use and the nature and extent of nonconformity.
    This list shall be brought up to date annually. (9) The Building
    Official shall prepare a list of those nonconforming uses which have
    been hurricane-proofed or otherwise protected in conformance with
    these Regulations. He shall present such list to the Board of
    Adjustment, which may issue a certificate to the owner stating that
    such uses, as a result of these corrective measures, are in
    conformance with these Regulations.

    SECTION 2.3 ALTERNATE MATERIALS AND METHODS OF CONSTRUCTION

    2.3.1 APPLICATION: These Regulations are not intended to prevent
    the use of any materials or methods of construction not specifically
    prescribed herein or by "The Building Code," provided any such
    alternate has been approved and its use authorized by the Building
    Official prior to its incorporation or use in the construction, in
    accordance with methods and procedures set forth in this code for
    approval of new materials and special systems of design or construction.

    2.3.2 APPROVAL. The Building Official may approve any such
    alternate, provided he finds the proposed design is satisfactory
    and complies with the provisions of "The Building Code" and that the
    material, method, or work offered is, for the purpose intended, at
    least equivalent to that prescribed in "The Building Code" in
    quality, strength, effectiveness, fire resistance, durability, and
    safety. The Building Official shall-require that sufficient
    evidence or proof be submitted to substantiate any claim that may
    be made regarding its use. If, in the opinion of the Building

                                 I V-4

    Official, the evidence and/or proof is not sufficient to justify
    approval, the owner or his agent may refer the entire matter to the
    Board of Appeals.

    SECTION 2.4 TESTS

    2.4.1 PROOF OF COMPLIANCE: Whenever there is insufficient
    evidence or proof of compliance with the provisions of these
    Regulations, or evidence that any material or any construction
    does not conform to the requirements of these Regulations, or in
    order to substantiate claims for alternate materials or methods
    of construction, the Building Official may require tests or test
    reports as proof of compliance. Tests, if required, are to be
    made at the expense of the owner or his agent by an approved
    testing laboratory or other approved agency, and in accordance with
    approved rules or accepted standards as prescribed in "The Building
    Code."

    2.4.2 ABSENCE OF APPROVED RULES: In the absence of approved rules
    or other accepted standards, the Building Official shall determine
    the test procedure or, at his election, shall accept duly authenticated
    reports from recognized testing authorities or agencies in respect
    to the quality and manner of use of new materials.

    2.4.3 RECORDS: Copies of such tests, reports, certifications, or
    the result of such tests shall be kept on file in the office
    the Building Official for a period of not less than three years
    after the approval and acceptance of the completed structure for
    beneficial occupancy.

    SECTION 2.5 ORGANIZATION AND ENFORCEMENT

    2.5.1 RULES AND REGULATIONS: The Building Official is hereby
    authorized and directed to enforce the provisions of these Regulations
    as part of "The Building Code." For such purpose he shall have the
    powers of a police officer.

    2.5.2 DEPUTIES: The Building Official may appoint such number of
    officers, inspectors, and assistants as required. He may deputize
    such employees as needed to perform the functions of the Building
    Department.

    2.5.3 OFFICIAL RECORDS: The Building Official shall establish and
    maintain an official record of all business and activities of the
    department relating to these Regulations, and all such records
    shall be open to public inspection. He shall keep a permanent,
    accurate account of all fees and other monies collected and received
    under these Regulations. The Building Official shall, at least once
    a year, submit a report to the proper city official covering the
    work of the Department during the preceding period. Said report shall
    include detailed information regarding the administration and
    enforcement of these regulations.

                               I V,_ 5

                                       SUBJEO A RO ISOM

    2.5.4 RIGHT OF ENTRY: Whenever it may be necessary to make an
    inspection to enforce the provisions of these Regulations, the
    Building Official or his authorized representative may enter such
    building or premises at all reasonable times to inspect all parts
    that are or may be subject to flooding or where the potential for
    hurricane damage exists.

    2.5.5 STOP WORK ORDER: Whenever any building work is found to
    be done contrary to these Regulations, the Building Official
    shall order the work stopped by notice in writing to the person
    doing the work.

    2.5.6 BOARD OF APPEALS: In order to determine the suitability
    of alternate materials and methods of construction and to provide
    reasonable interpretations of the provisions herein, there shall
    be and is hereby created a Board of Appeals of ___members.  Each
    member of the Board shall be a licensed professional architect or
    engineer, or a builder or superintendent of building construction,
    with at least ten years experience, for five years of which he shall
    have been in responsible charge of work. At no time shall there
    be more than two members from the same profession. At least one
    of the members shall be a licensed structural or civil engineer with
    architectural engineering experience. The Board shall adopt
    reasonable rules for its investigations and shall render written
    decisions to the Building Official.

    2.5.7 VALIDITY: It shall be unlawful for any person, firm, or
    corporation to erect, construct, enlarge, alter, repair, move, improve,
    remove, convert, or demolish any building or structure in the
    Hurricane Hazard Area(s), or cause the same to be done, contrary
    to or in violation of any of the provisions of these Regulations
    and/or "The Building Code."

    2.5.8 VIOLATIONS AND PENALTIES: Any person, firm, or corporation
    violating any of these provisions shall be deemed guilty of a
    misdemeanor, and upon conviction thereof shall be punished by a fine
    or by imprisonment as provided in the laws of the municipality for
    such misdemeanor, or as specified in "The Building Code."

    SECTION 2.6 PERMITS

    2.6.1 STATEMENT OF INTENTION TO IMPROVE: The Owner or any
    registered architect or licensed professional engineer authorized
    to represent the Owner shall, before preparing final plans for any
    improvement in the Hurricane Hazard Area(s), file with the Building
    Official a Statement of Intention to Improve, including a brief
    description of the type of improvement being considered and giving
    its precise location, on a form provided by the Building Official.
    The Building Official shall note on two copies the Hurricane Hazard
    Zone and the elevation of the RFD at the location of the proposed
    improvement. One copy of the Statement of Intention to Improve
    shall be retained by the Building Official until a permit for

                              IV-6

    improvement on the site is approved or one year has elapsed;a
    second copy shall be returned to the Owner for his use in final
    siting and design of his improvement. Assignments of the Hurricane
    Hazard Zone and the RFD elevations at all locations shall be as
    described in Chapter Four. This information shall be open to
    public examination at all reasonable times.

    2.6.2 PERMITS REQUIRED: No person, firm, or corporation shall erect,
    construct, enlarge, alter, repair, remove, convert, or demolish any
    building or structure or any .part thereof, or make any other improve-
    ment within the Hurricane Hazard Area(s), or cause same to be done,
    without first obtaining a separate building permit for any such
    improvement from the Building Official. Ordinary minor repairs
    may be made without the approval of the Building Official without
    a permit, provided that such repairs shall not violate any provision
    of these Regulations or of "The Building Code."

    2.6.3 APPLICATIONS: To obtain a permit, the applicant shall first
    file an application therefore which shall consist of: (1) A descrip-
    tion of the work to be covered by the permit including a list of
    all spaces affected by these Regulations giving flood-proofing
    class, elevation of RFD, Hazard Zone, floor elevations), proposed
    uses and contents, and references to drawings and specifications
    which explain the flood-proofing measures that apply to each space.
    The description shall include an estimate of the total value
    of the improvement. This description shall be made on a form provided
    by the Building Official (Figure 1).  (2) __  sets of complete
    plans and specifications, in addition to plans and specifications
    required by "The Building Code," except that plans and specifications
    for any and all proposed improvements in the Hurricane Hazard Area(s)
    shall be prepared by an engineer licensed by the State to practice
    as such. All drawings and specifications shall bear the name of
    the author thereof in his true name, followed by such title as he
    may be lawfully authorized to use. All plans and sections shall be
    noted with the proposed flood-proofing class of each space below the
    RFD including detail drawings of walls and wall openings.  (3)___
    copies of the Owner's Contingency Plan, which shall describe in
    detail all procedures for temporary placement and removal or contingent
    protection proposed for items in spaces affected by these Regulations
    including: a. Plans and schedules for items to be removed and locations
    of places above the RFD to which they will be removed if these
    contents violate restrictions associated with the flood-proofing
    class of the space in which they are placed temporarily, including
    specific organizational responsibilities for accomplishing this
    removal. b. Procedures, material and equipment for protecting items
    required to have protection by their flood-proofing class but for
    which this protection is proposed to be provided contingently,
    including specific organizational responsibilities for accomplishing
    this protection. Waivers of restrictions implicitly requested by
    submission of the Owner's Contingency Plan may be granted by the
    Building Official as provided by _____.  (4)  Any other information
    as reasonably may be required by the Building Official, including
    computations, stress diagrams, and other data sufficient to show
    the correctness of the plans.
                               IV-7

                                                                                         SI-Et) ro, F!E I7

    Supplementary                                BUILDING OR STRUCTURE IN FLOOD HAZARD AREA
    Application                                 (To Accompany Application for Building Permit)

    City or Town                                                            County
    Location
    Intended Use                                                                                             Value Of Improvement S ____
    Type of Construction                                                                                 No. of Stories__________
    Owne r                                                                  Address
    Exsit.Ground Elee.   *...MSL; Fin.Ground Elso.              MSL; Reg.Flood Datum Elev.at Sits            MSL; RFD Veiocity..........Ft/See
    .....Fioor Elev.        _ ML:  Proposed Use                          g.......Floor Eiev.        - SL,  Pro posed Use
      -Floor Ely             - dSL:  P roposed Use                      ;Floor  Elev.   _    M...,..SL,,  Proposed Use
    Maximuis Loading on Walls:                                              Ilydrostatip (Uplift) Pressure on Floor Slabs(MaximumL_?...SF
    Non Flood Load                                                    PSF  Foundation Type(s)
    Hydrostatic Load                                                  PSF  Lowest Foaotr Elen. (Bottom)                                   MSL
    Hydrodynamic Load                                                 psF  Savage Disposal, ...Septic Tank,....Pub.Syst.,........ther(Explain)
    impact Load                                                       PSF  Potable Ietsrt I...ndivldual Weill -..Pub.Syst.,-...Other(Explaln)
    Total Flood Load                                                  PSF
    Exterior Wall Construction Type(s):                                     Floor Construction Type(s)-.
    Above ______Floior                                                                 Floor

    Above           Floor           F        l        o        o        r        ____

    A bove   ~        Floor                                                ______f loor
    Types of Waterproofing
    Type(s) of Joints; Wells_______ Floors                   f          eeaos~als(ye)   als                              Floor_______
    Sump Location                                                           Sump Typo
    All Tanks and/or Bouyont Equipment Are                               Are Not                              Anchored To Prevent Flotation
    Alternate Power Source Is                              151.11t                          Provided For Emergency Operation Of Surcp Puimp
    Sanitary. Drainage & Water Supply Facilitlim Are....._........Are Not -___ Protected From Contamination & Back Flow by Flood Water
    Retaining Wall(s) Are                                      Ara Not                                  Used To Protect 801ilding/StrUCt~lr
    intentional Flooding is                                     Is Not                                 Planned For This Bui IdIn2/S tructure
    Temporary And/Or Emergency Flood Proof ing is                          Is Not __________Planfefl For This Building/Structure
    Building Structure Is                                  Is Not                                 Protected Against Erosion By Flood Flows
    Sits Is                                          Is Not                                       Protected Against Erosion By Flood Flows
    Classification of Building/Structure:  F........................,Primary      .         Secondary               . F lood Hazard Arma
    SPACES:   List below all spaces of the building or structure below the Regulatory Flood Datum Including their name, room num~-
    bar, and proposed flood-proofing claastioiatlon (i.e. WI, 12 etc.). List 311 contents of each space (see Chapter 10 of the
    Flood-Proofing Regulations). Mark all Items whIch oer to be either protested contingently or removed to safe refuge upon
     receipt of a flood warning with an asterisk (0); all such items must be mentioned in the owner's Contingency Plan. Attach
    additional sheets if necessary.

          The applicant hereby certifies that the above information Is correct and that the plans submitted herewith conform to
    thais submitted for occupancy permit application. The applicant agrees to comply with the provisions of the Zoning Ordi-
    nance, the Building Code and all other laws and ordinances affecting the construction and occupancy of this proposed build-
    ing.
    Signature Of Architect/Engineer                                         Address
                                                                         The undersigned will supervise the construction of the work
                                                                         above.

                                                                               Signature

    SEAL                                                                         TItle.

                                                                               Address

                                                                          (signature)
    Clerk                                                                               APPROVED FOR COMPLIANCE WIhi  BUILDING CODE
                                                                                 Date

                                                                  Figure I

    2.6.4 ACTION ON PERMIT APPLICATION: The complete application
    filed by an applicant for a flood-proofing permit, including all
    of the above listed items, shall be checked by the Building
    Official. Such plans may be reviewed by other Departments of the
       (city)     to check compliance with the laws and ordinances
    under their jurisdiction. The Building Official shall determine
    that the RFD elevation and Hazard Zone noted in the application
    are correct in accordance with the Statement of Intention to
    Improve and that all requirements for the flood-proofing classes
    selected by the Owner are met.  If the Building Official determines
    that for any space affected by these Regulations, any requirement
    for particular flood-proofing class, Hazard Zone, or any other
    requirement of these Regulations has not been met, he shall so
    indicate on the drawings and a permit shall not be granted. If
    the Building Official is satisfied that the work described in all
    parts of the application conforms to the requirements of these
    Regulations and "The Building Code" and other pertinent laws and
    ordinances, and that the fees specified in "The Building Code"
    have been paid, he shall issue a permit therefore to the applicant.
    When the Building Official issues the permit, he shall endorse in
    writing or stamp on ___sets of descriptions, plans and
    specifications, and the Owner's Contingency Plan "APPROVED"
              (name and date)               .___sets of the complete
    application as approved shall be retained by the Building Official
    for a period of not less than two years after the approval or
    issuance of a certificate of occupancy for the completed improvement.
      ___sets of the complete application as approved shall be returned
    to the applicant, of which one set shall be kept at the building
    site and available for review by the Building Official at all
    reasonable times.

    2.6.5 ISSUANCE OF PERMIT: The Building Official shall not issue a
    permit for the partial execution of any improvement until the complete
    application for the entire improvement has been submitted and
    approved. The issuance or granting of a permit or approval of an
    application shall not be construed to be a permit for, or approval
    of, any violation of these Regulations or of "The Building Code."
    The issuance of a permit based upon an approved application shall
    not prevent the Building Official from thereafter requiring correction
    in such application or any part thereof or from preventing work
     related to the execution of any improvement from being carried on
    thereunder when in violation of these Regulations, "The Building
    Code" or of any other ordinance of the         (city)

     2.6.6  EXPIRATION:  Every permit issued by the Building Official
     shall expire by limitation and shall become null and void if the
    work authorized by such permit is not commenced within 90 days
     after issuance date of such permit, or if the work authorized by
     such permit is suspended or abandoned at any time after the work
     is commenced for a period of 120 days. Before such work is re-commenced
     a new permit shall first be obtained, and the fee therefore shall
     be one-half the amount required for the original permit for such
     work; and provided, further, that such suspension or abandonment has

                               IV-9

                                         SUBJEU 10 REVISION

    not exceeded one year, after which, a new application for permit
    must be submitted and the permit fee shall be based on the total
    value of all construction work for which the permit is issued.

    2.6.7 REVOCATION OF PERMIT: The Building Official may revoke a
    permit or approval issued under these Regulations in case of any
    false statement or misrepresentation of fact in the application
    or on the plans, whenever the permit is issued in error, or whenever
    the permit is issued in violation of any ordinance or regulation,
    "The Building Code," or these Regulations.

    2.6.8 PERMIT FEES: Building permit fees shall be paid to the
    Building Official as required and set forth in "The Building Code,"
    and in accordance with the determination of value or valuation under
    any provision of these Regulations that shall be made by the
    Building Official.

    2.6.9 POSTING OF PERMIT: The building permit shall be posted at
    the site of operations in a conspicuous place open to public
    inspection during the entire time of prosecution of the work and
    until completion of the same.

    SECTION 2.7 INSPECTIONS

    2.7.1 INSPECTIONS REQUIRED: All construction or work for which a
    permit is required shall be subject to inspection by the Building
    Official.

    2.7.2 PERIODIC INSPECTIONS: Buildings or structures and parts thereof
    that contain or utilize contingent or emergency (temporary) type
    hurricane-proofing elements or devices shall be subject to inspection
    by the Building Official at intervals of three (3) years or less.
    The Owner or his agency shall be notified at least 10 days in advance
    of inspection date and shall be present at the inspection. He
    shall be responsible for demonstrating the availability, installation,
    and proper functioning, anchorage and support of all closure assemblies
    and other contingent or emergency (temporary) hurricane-proofing
    items. All necessary correction of deficiencies shall be performed
    within 90 calendar days of the inspection date and at the Owner's
    expense. Failure to perform the required work within the prescribed
    time shall be a violation of these Regulations and the applicable
    part(s) of "The Building Code."

    2.7.3 MAN DATORY INSPECTIONS: (a) The Building Official, upon
    notification from the permit holder or his agent, shall make the
    *following inspections and shall either approve that portion of the
    work completed or shall notify the permit holder or his agent
    wherein the same fails to comply.

         2.7.3.1 FOUNDATION INSPECTION: To be made after necessary
    excavations have been made, forms erected and reinforcing steel placed.

                               IV-10

         2.7.3.2  PILE INSPECTION:  To be made during the driving of
    the piles and after all piles are driven and forms and reinforcing
    steel are in place and tied, and before placing any concrete. (Refer
    to 2.7.7 SPECIAL INSPECTOR.)

         2.7.3.3 REINFORCING INSPECTION: To be made after any
    reinforcing steel is in place and before placing concrete.

         2.7.3.4 FRAME INSPECTION: To be made at each floor level and
    after all framing, fire blocking, furring and bracing are in place,
    and plumbing and electrical work are roughed in.

         2.7.3.5 ROOFING INSPECTION: To be made after anchor sheet
    or sheets have been tincapped and before cap sheet is mopped on.

         2.7.3.6 CURTAIN WALL INSPECTION: To be made at each floor
    level after curtain walls are installed and before curtain-wall
    attachments are concealed.

         2.7.3.7 STORE FRONT INSPECTION: To be made after store fronts
    are installed and before store front attachments are concealed.

         2.7.3.8 WINDOW AND GLASS DOOR INSPECTION: To be made after
    windows and glass doors are installed and before attachments and
    connections to the building frame are concealed except that for
    one and two-story buildings this inspection shall not be required.

         2.7.3.9 LATHING INSPECTION: To be made after lathing and
    before plastering, where plastering is a requirement for fire
    protection, or where suspended overhead.

         2.7.3.10 PLUMBING INSPECTION: To be made of the ground work
    and at each floor. All plumbing work shall be left uncovered and
    convenient for examination until inspected and approved. Floors
    shall be left up in all bathrooms and elsewhere above all sanitary
    plumbing, water-supply and gas-supply piping and other plumbing
    work until it shall have been examined, tested and approved.

         2.7.3.11 ELECTRICAL INSPECTION: To be made at each floor
    level; and no conduit boxes, panels or other electrical
    appurtenances shall be covered or concealed until approval shall
    have been received from the Building Official.

         2.7.3.12 SPECIAL INSPECTIONS: To be made of all mechanical
    installations, signs and awnings immediately upon completion and
    at such intervals during the progress of the work as the Building
    Official or this Code may require.

         2.7.3.13 OTHER INSPECTIONS: To be made as the owner or con-
    tractor or Building Official may reasonably request.

                               IV-11

        2.7.3.14  FINAL INSPECTION:  To be made after thie work is
    completed and the structure ready for use or occupancy.

    2.7.4 No work shall be done on any part of a building or structure
    or any plumbing, electrical or mechanical installation beyond
    the point indicated hereinabove for each successive inspection
    until such inspection has been made and the work approved and the
    inspector has so indicated on the approved plans or permit card
    at the job site.

    2.7.5 No reinforcing steel or structural framework of any part
    of any building or structure shall be covered or concealed in any
    manner whatsoever without the approval of the Building Official.

    2.7.6 Inspection requests shall be made to the office of the
    Building Official and shall provide reasonable time for such
    inspection to be made. Rejection or refusal to approve the work
    for reasons of incompleteness, Code violation or inadequacy shall
    nullify that request for inspection. This work shall be made to
    comply and the request for inspection repeated as outlined herein.
    It shall be assumed that the responsible individual or individuals
    in charge of the work shall have themselves inspected the work
    and found it to be in compliance with Code requirements before
    request for inspection is made.

    2.7.7 SPECIAL INSPECTOR: (a) The Building Official may require
    the owner to employ a special inspector for the inspection of the
    structural framework, or any part thereof, as herein required:
    1. Buildings or structures or parts thereof of unusual size, height,
    design or method of construction and critical structural connections.
    2. Pile driving. 3. Windows, glass doors and curtain walls on
    buildings over two stories. (b) Such special inspector shall be
    an Architect or Professional Engineer or a duly accredited
    employee representing either. The special inspector shall be
    responsible for compliance with this Code and shall submit progress
    reports and inspection reports to the Building Official. (c) At
    the completion of the work or project, the special inspector shall
    submit a Certificate of Compliance to the Building Official,
    stating that the work was done in compliance with this Code and
    in accordance with the approved plan or plans; and his duties shall
    end with the submission of such certificate. Final inspection shall
    be made by the Building Official before a Certificate of Occupancy
    is issued.

    2.7.8 INSPECTION REPORTS: The Building Official shall keep records
    of inspections, Certificates of Compliance, results of tests, plans,
    surveys and Certificates of Occupancy for a period of not less
    than seven years. Such records shall become a part of the public
    record and open to public inspection, except as may be elsewhere
    specifically stipulated.

                                IV-12

    2.7.9 SPECIAL HURRICANE INSPECTIONS: (a) During such periods of
    time as are designated by the National Weather Service as being a
    hurricane alert, all furniture, awnings, canopies, display racks,
    material and similar loose objects in exposed outdoor locations
    shall be lashed to rigid construction or stored in buildings.
    Orders shall be oral or written and shall be given to any person
    on the premises most logically responsible for maintenance and such
    orders shall be carried out before winds of hurricane velocity are
    anticipated. (b) After winds of hurricane velocity are experienced
    and have subsided, the Building Official shall investigate to
    determine if damage has occurred to buildings or other structures.
    (c) No building or other structure or assembly or part thereof
    which was damaged or collapsed or out of plumb or line shall be
    repaired or altered or otherwise returned to its original position
    without inspection and approval by the Building Official.

    SECTION 2.8 CERTIFICATE OF USE AND OCCUPANCY

    2.8.1 NEW BUILDINGS AND STRUCTURES: No building or structure
    hereafter constructed in the Hurricane Hazard Area(s), or any portion
    thereof, shall be used or occupied until the Building Official
    shall have issued a certificate of use and occupancy.

    2.8.2 BUILDINGS OR STRUCTURES HEREAFTER ALTERED: No building or
    structure in the Hurricane Hazard Area(s) hereafter enlarged,
    extended or altered, or any portion thereof, shall be used or
    occupied, and no change in use or occupancy shall have made, until
    the Building Official shall have issued the certificate of use and
    occupancy, except that the Building Official may permit lawful use
    or occupancy to continue upon the submission of evidence that
    the hurricane hazard or vulnerability of any occupied portions of
    the structure and its contents will not be increased during the
    execution of the improvements.

    2.8.3 EXISTING BUILDINGS AND STRUCTURES: The Building Official
    shall issue a certificate of use and occupancy for an existing
    building or structure located in the Hurricane Hazard Area(s)
    upon receipt of a written request from the Owner, provided:
    (1) There are no violations of law or orders of the Building
    Official pending. (2) It is established after inspection and
    investigation that the alleged use or occupancy of the building or
    structure has heretofore existed. (3) There is a positive showing
    that the continued use or occupancy of a lawfully existing
    building or structure in the Hurricane Hazard Area(s),
    without requiring alterations, rehabilitation or reconstruction,
    does not endanger public safety and welfare. The Building Official
    shall refuse to issue a certificate of use or occupancy for any
    existing building or structure in the Hurricane Hazard Area(s) when-
    ever it is found that the building or structure, or any portion
    thereof or appurtenant thereto, is in an unsafe condition and/or
    would be potentially unsafe when subjected to floods up to the RFD.
    He shall, in writing, so notify the Owner, lessee, tenant, occupant

                               IV-13

         and/or agent thereof describing said condition and ordering
         abatement thereof within a reasonable length of time. Failure to
         comply with the order of the Building Official shall be a violation
         of these Regulations and the applicable part(s) of ".The Building
         Code."

         2.8.4 CONTENTS OF CERTIFICATE: When a building or structure is
         entitled thereto, the Building Official shall issue a certificate
         of use and occupancy that shall certify compliance with the
         provisions of these Regulations and "The Building Code." Issuance
    Sl    ~of a certificate does not assign liability to the community.

         SECTION 2.9 PUBLIC NOTICE OF HURRICANE HAZARD

          2.9.1 PROCEDURE: On or about the first day of May, the Building
          Official shall alert the public of the existing Hurricane hazard
          of the      (city)        . He shall publish or cause to be
          published a public notice which shall indicate the recorded
          maximum wind velocity and the elevation of the flood of record
          together with depths and approximate area(s) of inundation (if
          known). Said public notice will also contain similar information
          about the RFD that is established for purposes of these Regulations.

          2.9.2 OTHER INFORMATION: The public notice shall emphasize the
          necessity for maintenance and repair of all contingent hurricane-
          proofing measures and the probability of occurrence of a hurricane
          that would cause floods to reach elevations higher than the RFD.
          It shall advise owners and/or occupants to operate all mechanically
          and manually operated closure assemblies for doors, windows and
          utilities openings, emergency electrical generating units, sump
          pumps, etc., and to check the availability and condition of all
          temporary closure panels, gaskets and anchorage devices, etc. All
          organizational, volunteer or assistance groups having responsibilities
          to act at time of hurricane emergencies shall be advised to review
          their state of readiness for effective mobilization and implementation
          of the hurricane emergency plan.

          SECTION 2.10 CLASSIFICATION AND POSTING OF BUILDINGS AND STRUCTURES

          2.10.1 GENERAL: For administrative purposes of coordination of
          zoning regulations, inspection of structures, and conduct of
          emergency public safety operations, all buildings or structures in
          the Hurricane Hazard Area(s), whether existing or hereafter erected,
          shall be classified and posted in accordance with this Section.
          Classification of buildings and structures (FPI, FP2, etc.) is
          shown in Table I and is based upon the flood-proofing classifications
          of the constituent spaces (WI, W2, etc.) of the structure below
          the RFD (see Chapter 4) and the means by which these classifications
          are achieved. Posting shall be accomplished by placards mounted
          on internal walls at building entrances. For public safety
          operations, an identification symbol, e.g., FP1, shall be placed
          on the outside of the building above the RFD so as to be readily
          visible.

                                      IV-14

                                            TABLE 1I

                          CLASSIFICATION OF BUILDINGS AND STRUCTURES
    Building or                             SPACE CLASSIFICATION
    Structure           WI                W2       I    W3        1   W4              W5
    Classifi-    Completely Dry  Essentially Dry  Flooded with  Flooded with  Non-Flood-
    cation       w/o HI*  w/HI*   w/o HI*  w/HI*  Potable Water  Floodwater        Proofed

     FP1           X                 X

     FP2           X         X       X         X

     FP3           X                 X                    x              x

     FP4           X         X       X         X          X              X

     FP5                                                                             x

       Human Intervention

                 2.10.2 STRUCTURE DESIGNED FOR WIND AND COMPLETELY FLOOD-
                 PROOFED (FP1, FP2):

                      2.10.2.1 FP1 -- Any building or structure located in
                 Hurricane Hazard Area(s) designed in accordance with these
                 Regulations and with no space below the RFD or in which all en-
                 closed spaces below the RFD are classified WI or W2 without
                 employing any contingent closure, removal, protection, or other
                 measure which requires human intervention for effectiveness in
                 a flood event to obtain those classifications shall be known as
                 a Completely Flood-Proofed Structure and classified FP1. It
                 shall be posted by the Owner with a Type 1 placard, which shall
                 be fastened securely to the structure in a readily visible place.

                      2.10.2.2 FP2 -- Any building or structure located in a
                 Hurricane Hazard Area designed in accordance with these Regula-
                 tions and with any space below the RFD and in which all such
                 spaces are classified WI or W2, but for which at least one or
                 more of the spaces employs any contingent closure, removal,
                 protection, or other measure which requires human intervention
                 for effectiveness in a flood event to obtain those classifica-
                 tions shall be classified FP2. It shall be posted by the Owner
                 with a Type 2 placard, which shall be fastened securely to the
                 structure in a readily visible place above the RFD.

                 2.10.3 STRUCTURES DESIGNED FOR WIND AND PARTIALLY FLOOD-
                 PROOFED (FP3, FP4):

                      2.10.3.1 FP3 -- Any building or structure located in a
                 Hurricane Hazard Areadesigned in accordance with these Regula-
                 tions and which contains a combination of spaces below the RFD
                 that are classified W1 or W2 which is achieved without human

                                             IV-15

                                                              TABLE 2

                                                    SPACE CLASSIFICATION CHART

                                            FLOOD-PROOFING CLASSIFICATION OF SPACES
                                                          MINIMUM REQUIREMENTS
    Flood-                                   Closure    Internal                  Walls
    Proofing       Water-      Structural   of          Flooding &                and
    Classes        Proofing   Loads          Openings   Drainage      Flooring   Ceilings   Contents   Electrical   Mechanical

       W1
    Completely
      Dry           Type A       Class 1     Type 1                    Class 1    Class 1    Class 1

       W2
    Essentially
      Dry           Type B       Class 1     Type 1  Class 2    Class 2    Class 2

        W3                                                  o
    Flooded                                                 *
      with Pota-                                               4     4
     able Water     Type A       Class 2     Type 3         V          Class 3    Class 3    Class 3
                                                        W                                                              a)
        W4                                                                                                     a)
    Flooded with
      Flood Water   Type C       Class 3     Type 4                    Class 4    Class 4    Class 4

        W5
    Non-Flood-
      Proofing        --           --        Type 5                    Class 5    Class 5    Class 5

                                                             IV-16                                    "'%

                                            F-177n "flT'' 7

    intervention, and one or more spaces that will be flooded
    internally (W2 and/or W4), shall be known as a partially flood-
    proofed structure and be classified FP3. It shall be posted
    by the Owner with a Type 3 placard which shall be fastened securely
    to the structure in a readily visible place above the RFD.

         2.10.3.2 FP4 -- Any building or structure located in the
    Hurricane Hazard Area designed in accordance with these
    Regulations and which contains a combination of spaces below
    the RFD that are classified WI or W2 which is achieved with
    human intervention, and/or one or more spaces that will be
    flooded internally (W3 and/or W4), shall be classified FP4. It
    shall be posted by the Owner with a Type 4 placard which shall
    be fastened securely to the structure in a readily visible place
    above the RFD.

    2.10.4 STRUCTURES DESIGNED FOR WIND BUT NON-FLOOD-PROOFED (FP5):
    Any existing building or structure located in a Hurricane Hazard
    Area which contains one or more spaces below the RFD that are not
    flood-proofed (W5) shall be known as a Non-Flood-Proofed Structure
    and classified FP5. It shall be posted by the Owner with a Type 5
    placard which shall be securely fastened to the structure in a
    readily visible place.

    2.10.5 SAFE REFUGE AREAS: Buildings or structures located in
    the Hurricane Flood Hazard Area that are provided with area(s)
    of safe refuge shall have said area(s) posted by the Owner with
    a Type 6 placard, which shall be securely fastened to the structure
    in a readily visible place.

    2.10.6 PLACARDS: All placards shall be furnished by the Building
    Official and installed by the owner and shall be replaced
    immediately if removed, or defaced.

    2.10.7 PLACARD TYPES: Placards shall be white rigid plastic or
    other non-water-susceptible material, _        inches long and
    wide, and shall have printed thereon in black letters the in-
    formation shown in Figure 2.

    2.10.8 VIOLATIONS: Failure to comply with the requirements of
    this section shall be a violation of these Regulations and the
    applicable part(s) of "The Building Code".

                                IV-17

                          PLACARD TYPES    "           Ci'i,7

               COMPLETELY FLOOD-PROOFED BUILDING
    This building is completely flood-proofed to withstand
    flooding to the expected high water level of        feet MSL.

    Floor elevation at this point        feet MSL.

                             Type 1

                   FLOOD-RESISTIVE BUILDING
    This building contains areas below the expected high water
    level of       feet MSL which require implementation of
    pumps or other devices to maintain the required degree of
    protection.

    Floor elevation at this point        feet MSL.

                             Type 2

               PARTIALLY FLOOD-PROOFED BUILDING

    Structural integrity during floods to the expected high water
    level of       feet MSL will be maintained by internal
    flooding of       spaces when flood water reach        feet MSL.

    Floor elevation at this point        feet MSL.

                             Type 3

               PARTIALLY FLOOD-RESISTIVE BUILDING

    Structural integrity during floods to the expected high water
    level of       feet MSL will be maintained by internal flooding
    of       spaces when waters reach        feet MSL.  Some
    areas require implementation of pumps or other devices to
    maintain the required degree of protection.

    Floor elevation at this point        feet MSL.

                             Type 4

                            IV-18

                  NON-FLOOD-PROOFED BUILDING
    This building is not flood-proofed. Expected high water
    level is        feet MSL.

    Floor elevation at this point         feet MSL.

                             Type 5

                      AREA OF SAFE REFUGE
    This space is above the expected high water level of
    feet MSL, and is authorized as an area of safe refuge for
          persons.

    Floor elevation at this point         feet MSL.

                             Type 6

                            CHAPTER 3vrI~"r~

                     DEFINITIONS OF TERMS
                                                      i "~

    SECTION 3.1 SCOPE

    3.1.1 PURPOSE: For the purpose of these Regulations, certain
    abbreviations, words, and their derivatives, shall be construed
    as set forth in this Chapter.

    SECTION 3.2 DEFINITIONS

    3.2.1 GENERAL: The terms defined in this Chapter have been
    grouped in accordance with their main uses under the headings
    Administrative, Physical, and Regulatory.

    3.2.2 ADMINISTRATIVE:

         3.2.2.1 ACCESSORY USE OR STRUCTURE -- a use or structure
    on the same lot with, and of a nature customarily incidental and
    subordinate to, the principal use or structure.

         3.2.2.2 BUILDING OFFICIAL -- the officer charged with the
    administration and enforcement of the Building Code and these
    Hurricane-proofing Regulations or his regularly authorized deputy.

         3.2.2.3 HURRICANE HAZARD ZONES -- As defined in Chapter 4.

         3.2.2.4 FREEBOARD -- a factor of safety usually expressed
    in feet above a design flood level for flood protective or control
    works. Freeboard tends to compensate for the many unknown factors
    that could contribute to flood heights greater than the height
    calculated for a selected size flood and floodway conditions such
    as wave action, bridge opening and floodway obstructions, and the
    hydrological effects of urbanization of the watershed.

         3.2.2.5 HABITABLE ROOM -- a space used for living, sleeping,
    eating or cooking, or combination thereof, but not including bath-
    rooms, toilet compartments, closets, halls, storage rooms, laundry
    and utility rooms, basement recreation rooms and similar spaces.

         3.2.2.6 NONCONFORMING USE -- a building or structure, or the
    use thereof, which was lawful before the passage or amendment of
    the (ordinance, resolution, act) but which is not in conformance
    with the provisions of these Regulations.

         3.2.2.7 OWNER -- any person who has dominion over, control
    of, or title to an artificial or natural obstruction.

         3.2.2.8 REGULATORY FLOOD -- a flood which is representative
    of large floods known to have occurred generally in the area or
    reasonably characteristic of what can be expected to occur in a
    particular hurricane. This hurricane is generally being recognized
    and accepted nationally by Federal and non-Federal interests as one
    with an average frequency of occurrence on the order of once in
    100 years.

                                  IV-20

                       3.2.2.9  REGULATORY FLOOD DATUM (RFD)  --established plane
    *             ~~~~of reference from which elevation and depth of flooding may be
                  determined for specific locations of the floodplain. It is the
                  Regulatory Flood plus a freeboard factor of safety established
    *             ~~~~for each particular area which tends to compensate for the many
                  unknown and incalculable factors that could contribute to greater
                  flood heights than that computed for a Regulatory Flood.
                       3.2.2.10 SUBDIVISION -- the partitioning or dividing of a
                  parcel or tract of land.

                  3.2.3 PHYSICAL:

                       3.2.3.1 ARTIFICIAL OBSTRUCTION -- any obstruction whi~ch is
                  not a natural obstruction.

                       3.2.3.2 CHANNEL -- a natural or artificial watercourse of
                  perceptible extent, with definite bed and banks to confine and
                  conduct continuously or periodically flowing water. Channel flow
                  thus is that water which is flowing within the limits of the
                  defined channel.

                       3.2.3.3 FILL -- the placing, storing, or dumping of any
                  material, such as (by way of illustration but not of limitation)
                  earth, clay, sand, concrete, rubble, or waste of any kind upon
                  the surface of the ground which results in increasing the natural
                  ground surface elevation.

                       3.2.3.4 FLOOD -- an overflow of lands adjacent to a river,
                  stream, ocean, lake, etc., not normally covered by water. Other-
                  wise it is normally considered as any temporary rise in stream
                  flow or stage that results in significant adverse effects in the
                  vicinity. Adverse effects may include damages from overflow of
                  land areas, backwater effects in sewers and local drainage channels,
                  creation of unsanitary conditions, soil erosion, deposition of
                  materials during flood recessions, rise of ground water coincident
                  with increased stream flow, contamination of domestic water supplies,
                  and other problems.

                       3.2.3.5 FLOOD CREST -- the maximum stage or elevation
                  reached by the waters of a flood at a given location.

                       3.2.3.6 FLOODPLAIN -- the area, usually low lands, adjoining
                  the channel of a river, stream or watercourse or ocean, lake, or
                  other body of standing water which has been or may be covered by
                  floodwater.

                       3.2.3.7 FLOOD-PROFILE -- a graph or a longitudinal profile
                  showing the relationship of the water surface elevation of a
                  flood to location along a stream or river.

                                             IV-21

         3.2.3.8 FLOOD-PROOFING -- a combination of structural
    changes and/or adjustments incorporated in the design and/or
    construction and alteration of individual buildings, structures
    or properties subject to flooding primarily for the reduction
    or elimination of flood damages.

              3.2.3.8.1 PERMANENT FLOOD-PROOFING -- permanent
    protection shall be provided against the flood which does not depend
    upon any judgment, flood forecast, or action to put flood
    protection measures into effect.

              3.2.3.8.2 CONTINGENT (OR PARTIAL) FLOOD-PROOFING --
    contingent measures shall not be effective unless, upon receipt
    of a warning or forecast, some minimal action shall be required
    to make the flood-proofing measures operational.

              3.2.3.8.3 EMERGENCY (OR TEMPORARY) FLOOD-PROOFING --
    emergency measures shall be, upon receipt of a warning or forecast,
    either improvised just prior to or during an actual flood or
    carried out according to an established emergency plan of action.

         3.2.3.9 NATURAL OBSTRUCTION -- natural obstruction shall mean
    any rock, tree, gravel, or analogous natural matter that is an
    obstruction and has been located within the floodway by a
    nonhuman cause.

         3.2.3.10 REACH -- a hydraulic engineering term to describe
    longitudinal segments of a stream or river. A reach will generally
    include the segment of the floodplain where flood heights are
    primarily controlled by man-made or natural floodplain obstructions
    or restrictions. In an urban area, the segment of a stream or
    river between two (2) physically identifiable points on the
    stream centerline would most likely be designated as a reach.

         3.2.3.11 STRUCTURE -- anything constructed or erected on the
    ground, or attached to the ground, including but not limited to
    the following: docks, dams, fences, mobile homes, sheds and buildings.

         3.2.3.12 UNDERCLEARANCE -- the lowest point of a bridge or
    other structure over or across a river, stream, or watercourse
    that limits the opening through which water flows. This is
    referred to as "low steel" in some regions.

         3.2.3.13 WATERCOURSE -- any natural or man-made depression
    with a bed and well-defined banks two feet or more below the
    surrounding land serving to give direction to a current of water
    at least nine months of the year or having a drainage area of one
    square mile or more.

    3.2.4 REGULATORY:

         3.2.4.1 BUILDING CODE -- the regulations adopted by a local
    governing body setting forth standards for the construction,
    addition, modification and repair of buildings and other structures
    for the purpose of protecting the health, safety, and general
    welfare of the public.
                               IV-22

        3.2.4.2 SUBDIVISION REGULATIONS -- regulations and standards
    established by a local unit of government with authority granted
    under a state enabling law, for the subdivision of land in order
    to secure coordinated land development, including adequate
    building sites and land for vital community services and facilities
    such as streets, utilities, schools and parks.

                                IV-23

                             CHAPTER 1

                    HURRICANE HAZARD ZONES
    SECTION 4.1 DEFINITION OF THREAT AND HAZARD ZONES: A severe
    hurricane will pose several classes of hazards along the Texas
    coastline and extending inland distances which vary with coastal
    configuration.

    4.1.1 WIND: maximum windspeeds (fastest mile) up to 140 mph
    at a height of 30 feet, increasing with height in accordance with
    the one-seventh power law to a maximum several hundred feet above
    the surface. Peak gust speeds will exceed the sustained
    values by variable percentages. These gusts are considered in the
    tables in Chapter 8.

    4.1.2 STORM SURGE: (three sources of damage potential) (1) Scour
    due to currents and wave action, including washovers; (2) Battering
    due to waterborne debris; and (3) Flooding due to combinations in
    rises in sea level from storm surge and inland runoff from heavy
    rains and riverine discharges.

    4.1.3 In terms of these threat classes, the following coastal
    hazard zones are defined as the basis for the design of applicable
    model building codes:

         ZONE A:  (1)  140 mph sustained winds
                  (2) scouring action affecting foundation design
                  (3) battering from floating debris
                  (4) flooding (still water levels from expected
                       hurricane inundation more than one foot above
                       building grade level)

         ZONE B:  Same as Zone A except without scour

         ZONE C:  Same as Zone A except without scour and battering

         ZONE 0:  140 mph sustained winds at C-D boundary, diminishing
                  as an exponential function of distance* to 100 mph
                  at inland boundary

    SECTION 4.2 COMPUTATION OF REGULATORY FLOOD: The Regulatory Flood
    may be computed by adding the peak storm surge elevation and the
    inland rainfall backwater curve elevation as further described in
    this section. Refer to Annex A, B, and C.

    *VD = 100 +          where VD = wind speed in Zone D
                  I+-'T~
                               d = distance inland from C-D boundary

                                IV-24

    SECTION 4.3 GEOGRAPHICAL IDENTIFICATION OF HAZARD ZONES

    4.3.1 ZONE A: Area of washover and scour.

         4.3.1.1 Narrow, low segments of barrier islands and
    peninsulas that have been, are presently or have a high potential
    of being reached as a result of elevated water levels that
    generally exist during storms. (Ref: Bureau of Economic
    Geology, University of Texas.)

         4.3.1.2 A zone extending between Gulf beaches and a line
    of at least 300 feet from the maximum elevation immediately
    adjacent to the beach (e.g., dune crest or crest of sand
    and shell ramp).

         4.3.1.3 A zone along low-lying (less than 10 feet)
    unprotected (nonbulkheaded) bay shorelines extending at least
    200 feet inland from the highest elevation from the shoreline.

         4.3.1.4 Areas within 200 feet of unprotected (nonbulkheaded)
    navigation channels on peninsulas and barrier islands.

         4.3.1.5 Areas with sand substrate subject to hurricane
    flooding of greater than 3 feet with current velocities greater
    than 3 feet per second for one hour or more during the rise and
    fall of the surge.

    4.3.2 ZONE B: In the absence of washover channels and extensive
    scour, battering from waterborne debris will be expected to
    occur and will comprise the basis for defining Zone B.
         4.3.2.1 On barrier islands and peninsulas, a zone extending
    inland from the most landward foredune line or line of highest
    elevation and on low-lying shorelines with primarily clay substrate,
    a zone extending inland from the shoreline at least 500 feet
    regardless of building density.

         4.3.2.2 In areas where hurricane flooding is expected to
    be greater than 4 feet, building density is not greater than one
    major structure per acre, and effective wind fetch of greater than
    one mile.

    4.3.3 ZONE C: In the absence of the above conditions but where
    "still water" hurricane flood levels are in excess of one foot.

    4.3.4 ZONE D: This zone is concerned solely with wind forces on
    structures. Zone D is a strip beginning at the boundary with
    Zone C and extending inland to a point where the sustained hurricane
    winds are expected to reach 100 mph using the inverse relationship:

         VD = 100 + +-40, where VD = wind speed in Zone D

                               d = distance inland from C-D boundary

                               IVW25

                             CHAPTER5

                      WAVE AND SCOUR ACTION

    SECTION 5.1 GENERAL: Buildings and other structures shall not be
    constructed in Hazard Zone A unless positive provision is made
    either (a) to prevent movement or scour of underlying soil, or
    (b) to safeguard the structure in the event that such movement
    does occur.

    5.1.1 PREVENTION OF SOIL MOVEMENT: Prevention of underlying soil
    movement may be accomplished by retaining structures
    or bulkheads adequately designed to resist, in addition to the
    vertical loads acting thereon, incident lateral earth pressures,
    surcharges and hydrostatic loadings corresponding to the maximum
    high-water level.

    5.1.2 SAFEGUARDING STRUCTURE WHEN SOIL MOVEMENT OCCURS: In areas
    where scour and soil movement can occur if retaining structures or
    bulkheads are not provided, the structure shall be designed to be
    supported by properly designed pile foundations with due
    consideration being given to column action of piling in the event
    of scour, lateral loads on piling, and uplift capacity of piling
    when subjected to uplift loads by water or wind action.

    5.1.3 SOIL INVESTIGATION: All plans for new structures shall
    bear a statement as to the nature and character of the soil under
    the structure. Where the capacities of the soil are not known,
    examinations of subsoil conditions by borings or other tests
    may be required and evaluation of such soil investigations shall
    be made by a Professional Engineer. (Ref: Sec. 9.2)

    5.1.4 DESIGN OF FOUNDATIONS, RETAINING STRUCTURES, AND BULKHEADS

    All pile foundations, retaining structures and bulkheads in coastal
    areas subject to wind, wave and tidal action shall be designed by
    a Professional Engineer registered in the State of Texas. Records
    of penetration and bearing of all piles during installation
    shall be kept by the special inspector or Professional Engineer
    supervising the pile driving operations, bulkhead, or retaining
    structure installations. Copies of these records shall be submitted
    to the authority having jurisdiction.

    SECTION 5.2 STRUCTURAL REQUIREMENTS

    5.2.1 GENERAL: All buildings and structures shall be designed
    and constructed to resist the erosive and corrosive effects of the
    elements and where applicable to withstand the horizontal and
    vertical forces or loads required by "The Building Code" and, in
    addition, all loads prescribed in this section, without exceeding
    the prescribed allowable stresses.

                               IV- 26

    5.2.2  LOADS:                                MiL'4~1 TO MGM~ii

         5.2.2.1 WATER: As specified in Section 7.3.3.

         5.2.2.2 WAVES: The maximum wave force shall be calculated
    by using the maximum period. The most critical wave force, so
    determined, shall be used in the design. In case the natural
    period of vibration of the structure exceeds three seconds, dynamic
    analysis shall be performed to determine whether a resonance
    with the exciting wave forces is possible.

              5.2.2.2.1 WAVE DESIGN INFORMATION: Wave force
    design assumptions and calculations shall be submitted to the
    Building Official.

         5.2.2.3 BATTERING: As specified in Section 6.2.

         5.2.2.4 WINDS: As specified in Chapter 8.

    5.2.3 ALLOWABLE STRESSES: Allowable stresses for structural
    design shall be in accordance with the Building Code.
    5.2.4 STRUCTURES - LOCATION, TYPE, GENERAL SPECIFICATIONS

         5.2.4.1 LOCATION: Structure location must conform to other
    local, county, state and federal building and zoning regulations
    as well as these regulations.

         5.2.4.2 GENERAL: If the proposed type (material and geometry)
    or method of construction does not have an experience record
    sufficient to justify approval, the Building Official may require
    special tests or demonstrations 'I-o prove the acceptability of
    the project.

         5.2.4.3 BULKHEADS AND SEAWALLS

              5.2.4.3.1 LOCATION: In order to obtain uniformity of
    the shoreline, bulkheads should be located so as not to interfere
    with the requirements of the Texas Open Beaches Act. Locations
    of bulkheads other than along the official bulkhead line may
    be approved to meet proper land use requirements and if it
    is shown that no detriment to adjoining property will result.
    In no case shall the actual bulkhead alignment differ
    more than two inches from the approved alignment. In no
    case shall a bulkhead project seaward beyond the official
    bulkhead line except within the above-stated tolerance. Bulkheads
    proposed between two properties where bulkheads already exist
    shall be designed' to connect such bulkheads. Bulkheads proposed
    adjacent to property not bulkheaded shall be designed to return
    along the side property line a distance sufficient to protect the
    backfill and prevent damage to adjacent property, but not less
    than 25 feet along the ocean and bay or 10 feet along canals,

                               IV-27

    rivers, and other water areas. The return wall shall be
    protected from erosion by riprap or slope pavement.

              5.2.4.3.2 TYPE OF WALLS: The use of vertical face
    bulkheads will normally be limited to the bay front or inland
    waterways. Seawalls on the front and walls along sand beaches
    subject to wave action are to be an approved sloping high energy
    absorbing type, or vertical with energy-absorbing rubble mound
    on the face subject to wave action. The toe of the wall should
    be located sufficiently landward of the mean high-water line to
    prevent any immediate erosion of the foreshore area, and not
    less than 200 feet from the mean low-water shoreline on Gulf
    beaches subject to the Open Beaches Act; otherwise not less than
    50 feet from same. Whenever the beach in front of an existing
    vertical wall has eroded to such extent that water reaches the
    bottom of the wall at mean high tide, a rubble mound shall be
    placed in front of the wall; and existing vertical walls along
    sand beaches, when in need of major repairs, shall not be replaced
    unless a rubble mound be constructed in front of them.

              5.2.4.3.3 GENERAL SPECIFICATIONS: All bulkheads
    shall have a concrete cap designed to withstand the various loads
    placed upon it. The cap shall be large enough to provide no less
    than four inches of concrete cover between the piles, panels or
    masonry and nearest exterior face of cap. The elevation of the
    top of the cap shall be above the official flood criteria. (Such
    criteria provide for a minimum fill elevation, but not for
    storm wave heights.)  Other cap elevations may be approved but
    only when land usage, proximity of buildings, and effect on
    adjacent property have been considered. Safety curbs or guardrails
    shall be provided for bulkheads adjacent to roadways. Handrails
    shall be provided for bulkheads adjacent to walkways. Cables or
    steel rods used in tiebacks must be protected by at least three
    inches of concrete encasement if the cable or rod is less than
    one inch in diameter. Tiebacks not encased in concrete are to
    be protected by coating and wrapping with bituminous or other
    corrosive-resistant material. Anchors for tiebacks, whether piles
    or other types, shall bear on undisturbed or well compacted soil
    and shall be designed to provide adequate horizontal support.
    Precast concrete panels of tee-pile and panel bulkheads shall have
    the foot of the panels placed in a manner that will prevent under-
    mining of the backfill material. Fill material placed on the water
    side of a bulkhead shall not be considered to offer any passive
    resistance when such fill is subject to erosion. Gravity type
    bulkheads of stone and concrete combination will be permitted,
    provided they are constructed of no less than 40 percent cast-in-
    place concrete by cross sectional area and volume.

         5.2.4.4 PIERS AND DOCKS

              5.2.4.4.1 LOCATION: Piers and docks at right angles to
    the shoreline, or nearly so, shall be located not closer to the
    side property line, or said line extended, than a distance equal to

                                IV-28

                  the length of the pier or dock itself, provided however, no such
                  distance shall be less than 10 feet. Where the zoning is residential
                  or where the area is subdivided into tracts smaller than one
                  acre each, piers and docks are to be located within the middle
                  one-half of the water frontage.

                            5.2.4.4.2 TYPES: Structures such as piers which are to
                  project beyond the bulkhead line, if allowed, shall be of an
                  open type construction. Wharves, piers, or docks of solid fill
                  construction will be approved only where such construction will not
                  extend seaward of the approved bulkhead line.

                            5.2.4.4.3 GENERAL SPECIFICATIONS: In areas where the
                  zoning is residential or in areas where no tract is larger than one
                  acre, piers and docks shall be no more than 30 feet wide. In
                  no case shall piers or docks obstruct navigation or interfere
                  with drainage facilities. The projection of a pier or dock into
                  a restricted waterway such as a canal, river, creek or basin
                  shall be no greater than 10 feet or 20% of the waterway width,
                  whichever is smaller, but shall comply with any other laws or
                  regulations that may exist. Furthermore, the General Land Office's
                  approval may be given for piers projecting into open water areas
                  such as bays and sounds provided the projecting pier does not
    -             ~~~~obstruct navigation or encroach upon the rights of adjacent
                  property owners.

                       5.2.4.5 GROINS

                            5.2.4.5.1 LOCATION: Groins are to be located so that
                   the entire system of groins will provide the maximum benefit without
                  adverse effects. Groins shall be anchored sufficiently landward
                  to prevent flanking.

                            5.2.4.5.2 TYPES: Groins shall be either very low
                   impermeable nonadjustable or impermeable adjustable, designed and
                  maintained in adjustable condition for their entire life. The
                   use of permeable groins shall be limited to special conditions.

                             5.2.4.5.3 GENERAL SPECIFICATIONS: Groins may be used
                   to stabilize the beach if adjoining beaches are not adversely
                   affected. Groins shall be impermeable, and adjustable to meet
                   variations in natural conditions, and to produce the desired
                   elevation of the beach. Adjustable groins shall be maintained
                   at elevations in accord with actual beach needs and development of
                   desirable changes of the beach profile, and so as to avoid damage
                   to adjacent beaches. In no case shall the top of such groins be
                   set higher than 2 feet above the beach profile. Impermeable,
                   nonadjustable groins shall not extend seaward beyond the mean low
                   water line, and their top elevation shall not be higher than 6
                   inches above the beach profile. Groins must be constructed or
                   adjusted low enough to provide pedestrian access across them.
                   Consideration of the degree of beach protection to be provided by
                   proposed groins, and the acceptability of such installations, will

                                             IV-29

    be based primarily on the following factors: Direction and Volume
    of Littoral Drift; Wave Force and Direction; Wind Force and
    Direction; Land Usage; Type of Bulkhead; Type of Groin; and Spacing
    and Length of Groins. A complete coastal engineering study
    may be required before approval is given to the number, type, and
    location of groins.

         5.2.4.6 BEACH NOURISHMENT: Artificial nourishment of sand
    beaches or creation of new beach area are treated as construction
    projects. Typical profiles for such projects consist of a 50-foot
    level berm at elevation 6 ft. MSL; a I on 20 slope from there to
    MLW; and a I on 30 slope seaward to existing bottom. Special
    agreement between the upland owner proposing such a project and
    the building official may be required in order to adequately
    protect and permanently safeguard any public rights at the proposed
    site.

         5.2.4.7 JETTIES AND BREAKWATERS: Jetties and breakwaters
    shall be designed in accordance with the latest issue of the
    U.S. Army Corps of Engineers' Technical Report No. 4 entitled
    "Shore Protection, Planning and Design."

         5.2.4.8 MOORING PILES AND BUOYS: All mooring piles and buoys
    shall be placed within the limits of the owner's water frontage
    and shall be located in a manner not to interfere with navigation.
    Outer mooring piles and buoys shall not obstruct a navigable
    waterway except as permitted by the appropriate agency having
    jurisdiction over the waterway.

         5.2.4.9 BOAT SLIPS AND BOATHOUSES: Boat slips and boathouses
    to be located on private property require approval and permit
    from the Building and Zoning Department. Bulkheads proposed to be
    constructed for retaining the banks of the boat slip shall meet
    the requirements of this section of the manual. The location of
    boat slips shall conform to the same requirements as for piers
    and docks. Boathouses may be constructed over boat slips or
    as a separate structure subject to the following conditions:
    (a) The boathouse is not used as a dwelling, guest house or
    servant's quarters unless specially constructed as such to the
    requirements of the Building and Zoning Department; (b) The boathouse
    does not extend into a water area a distance greater than that
    permitted for a dock or pier; and (c) The overall size of the
    boathouse does not exceed 25 feet in width, 45 feet in length, or
    18 feet in height, except commercial marinas and drydocks may be
    permitted larger boathouses constructed in compliance with
    applicable zoning and building regulations.

    5.2.5 INFORMATION REQUIRED ON AND FOR THE PREPARATION OF CONSTRUCTION
    PLANS: Construction plans must be prepared by an engineer registered
    in Texas. Plans shall be arranged and numbered as a set and contain
    all (or applicable portions) of the following: (1) Plan, elevation,
    and sections showing the complete structure; (2) Details of
    structural components including precast members, structural connections,
    steel reinforcement, and expansion joints; (3) Complete description
    of all materials to be used; (4) Design loading and minimum
                                IV-30

    penetration of piles; (5) Location control: a. Horizontal control
    referred to a section line, road, or permanent landmark, and including
    property lines and the Official Bulkhead Line. b. Vertical
    control referred to U.S. Coast and Geodetic Survey Datum (MSL)
    including elevations landward, soundings in water areas, and the
    mean high water line; and (6) Graphical representation of test
    borings or soil profile parallel to and within five feet of
    proposed structures.

                                 IV-31

                             CHAPTER6                W

                       BATTERING BY DEBRIS

    SECTION 6.1 GENERAL: Buildings and other structures constructed
    in Hazard Zone B shall be designed in accordance with the provisions
    of this regulation and the "Building Code."

    6.1.1 Buildings designated as "Safe Refuge" and constructed in
    Hazard Zone B shall be designated for special battering loads.
    All other structures, except as noted, in Hazard Zone B shall
    be designed for normal battering loads.

    SECTION 6.2 BATTERING LOADS

    6.2.1 NORMAL BATTERING LOADS: Normal battering loads are those
    which relate to isolated occurrences of floatable objects of normally
    encountered sizes striking buildings or parts thereof. The normal
    battering load shall be considered as a concentrated load acting
    horizontally at the RFD or at any point below it, equal to the
    impact force produced by a 1,000 pound mass traveling at a
    velocity of 10 feet per second and acting on a one-square-foot
    surface of the structure.

    6.2.2 SPECIAL BATTERING LOADS: Special battering loads are those
    which relate to large conglomerates of floatable objects, either
    striking or resting against a building, structure or parts thereof.
    Where special battering loads are likely to occur (as in Hazard
    Zone B), such loads shall be considered in the design of buildings
    designated "Safe Refuge." Unless a rational and detailed analysis
    is made and submitted for approval by the Building Official, the
    intensity of the load shall be taken as 500 pounds per foot acting
    horizontally over a one-foot-wide horizontal strip at the RFD or at
    any level below it. Where natural or artificial barriers exist
    which would effectively prevent these special battering loads from
    occurring, the loads may be ignored in the design.

    6.1.3 EXTREME BATTERING LOADS: Extreme battering loads are those
    which relate to large floatable objects and masses such as runaway
    barges or collapsed buildings and structures, striking the
    building, structure, or component under consideration. It is
    considered impractical to design buildings having adequate strength
    for resisting extreme battering loads. Accordingly, except for
    special cases when exposure to these loads is highly probable
    and the resulting damages are severe, no allowances for these loads
    need be made in the design.

                                 IV-32

                             CHAPTER 7              L Lf Lj L~~IO

                             FLOODING

    SECTION 7.1 FLOOD-PROOFING CLASSIFICATION OF SPACES BELOW THE
    REGULATORY FLOOD DATUM

    7.1.1 SCOPE

         7.1.1.1 GENERAL: The flood-proofing classification of a
    space is determined by the degree of protection required under these
    Regulations to permit its intended use. The flood-proofing
    class of a space for which temporary placement or contingent
    protection measures are approved assumes that these measures are
    in effect during a flood and defines the resulting relationship
    of protection to use.

         7.1.1.2 ASSIGNMENT OF FLOOD-PROOFING CLASSES: Assignment
    is made by the Owner at the time of application for a permit and
    is subject to the approval of the Building Official. Every space
    of an improvement in a Flood Hazard Area which impinges in whole or
    part upon the RFD shall have a flood-proofing class assigned to
    it, and all requirements associated with a flood-proofing class
    shall be met by the space to which they apply in addition to all
    other requirements of these Regulations and the Building Code.

    7.1.2 DESCRIPTIONS OF FLOOD-PROOFING CLASSES

         7.1.2.1 CLASSIFICATIONS: The following descriptions of the
    five flood-proofing classes are approximate and general; more precise
    specification of the requirements associated with each class is
    given in Table 2 of the following section.

         7.1.2.2 COMPLETELY DRY SPACES (WI): The spaces shall remain
    completely dry during flooding to the RFD; walls shall be impermeable
    to passage of water and water vapor. Permitted contents and
    interior finish materials are virtually unrestricted, except for
    high-hazard type uses or human habitation. No portion of the
    building or structure that is below the RFD, regardless of structure
    or space classification, shall be used for human occupancy or for
    storage of any property, material, or equipment that Might
    constitute a safety hazard when contacted by flood waters. Structural
    components shall have capability of resisting hydrostatic and
    hydrodynamic loads and the effects of buoyancy.

         7.1.2.3 ESSENTIALLY DRY SPACES (W2): These spaces shall
    remain essentially dry during flooding to the RFD; walls shall be
    substantially impermeable to water, but may pass some water vapor
    or seep slightly. Contents and interior finish materials are
    restricted when hazardous or vulnerable under these conditions.
    Structural components shall have capability of resisting hydrostatic
    and hydrodynamic loads and the effects of buoyancy.

                                  IV-33

                                            VV- I r '

         1.1.2.4  SPACES INTENTIONALLY FLOODED WITH POTABLE WATER (W3:
    These spaces will be flooded internally with potable water
    provided by the Owner in order to maintain the building's structural
    integrity by equalizing pressures on structural components during
    flooding to the RFD; walls shall be sufficiently impermeable to
    prevent the passage, infiltration, or seepage of contaminated
    floodwaters. Contents and interior finish materials are
    restricted when hazardous or vulnerable under intentional flooding
    conditions.

         7.1.2.5 SPACES FLOODED WITH FLOODWATER (W4): These spaces
    will be flooded with floodwater (contaminated) by automatic means
    or are otherwise partially exposed to the unmitigated effects of
    the flood. Although there are minimal structural requirements
    for walls and other structural components, contents and interior
    finish materials are restricted to types which are neither
    hazardous nor vulnerable to loss under these flooding conditions.
    (Most spaces in existing buildings would have this classification
    if provided with a suitable automatic flooding system. Carports,
    loading platforms, open crawl spaces, porches and patios would
    generally fall into this classification.)

         7.1.2.6 NON-FLOOD-PROOFED SPACES (W5): A non-flood-proofed
    space in an existing building or structure is defined as a space
    which fails to meet the requirements of any of the above-described
    classifications.

    7.1.3 THE SPACE CLASSIFICATION CHART

         7.1.3.1 GENERAL: Table 2 indicates the various degrees of
    protection required to permit uses of spaces for each flood-proofing
    class. Although spaces must meet the requirements shown for
    each element of flood-proofing, the chart in itself shall not
    be construed as being exhaustive with respect to all requirements
    imposed by these Regulations. In disputes arising over the
    interpretation of this chart, the written provisions of these
    Regulations shall be considered as definitive.

         7.1.3.2 SEPARATION OF SPACES WITH DIFFERENT FLOOD-PROOFING
    CLASSIFICATIONS: Any two adjacent spaces below the RFD having
    different flood-proofing classes shall be separated by a barrier
    meeting the requirements for the space with the lower-numbered
    classification. In addition, any opening below the RFD between two
    adjoining spaces shall be provided with a closure meeting the
    requirements for the space with the lower-numbered classification.

    SECTION 7.2 WATERPROOFING

    7.2.1 SCOPE

         7.2.1.1 PURPOSE: This section shall govern the design, use
    and methods of construction and materials with respect to obtaining,

                                IV-34

    for a given space, the degree of protection against water, water
    vapor, and waterborne contamination determined by the
    vulnerability or hazard potential of the contents and interior
    finish materials to meet its flood-proofing classification.

         7.2.1.2 PERFORMANCE STANDARDS: Three types of waterproofing
    are defined herein as to the degree to which they satisfy a
    standard of dryness. If any material or method of construction
    meets the functional performance standard defining a type of
    waterproofing construction it shall be considered as satisfying
    the requirements of the section. For the purpose of these
    Regulations, the detailed specification of Type A waterproofing
    construction, as contained in this section, shall be interpreted
    as a guide to measures which are reasonable prerequisites for
    attaining this standard of dryness.

    7.2.2 TYPE A CONSTRUCTIONS

         7.2.2.1 PERMEABILITY: Type A waterproofing constructions
    are completely impermeable to the passage of external water
    and water vapor under hydrostatic pressure of flooding to the
    RFD. Type A waterproofing construction shall consist of either
    a continuous membrane satisfying paragraph 7.2.2.2, integrally
    waterproofed concrete satisfying paragragh 7.2.2.3, or a
    continuous interior lining satisfying paragraph 7.2.2.4.

         7.2.2.2 TYPE A MEMBRANE CONSTRUCTION: Type A membrane
    waterproofing forms a continuous external impervious lining to
    protect a structure with a concrete floor slab and concrete or
    reinforced concrete masonry unit walls. It shall comply with
    the following requirements for structural prerequisites, materials,
    and installation.

              7.2.2.2.1 STRUCTURAL PREREQUISITES:

                   7.2.2.2.1.1 CONTINUITY OF STRUCTURE: Structural
    slabs below the grade shall be continuous under perimeter walls
    to prevent differential settlement and shall be designed to act
    monolithically with the walls; reinforced concrete masonry unit
    walls shall be connected rigidly to slabs with reinforcing steel.

                   7.2.2.2.1.2 PRO~JECTION OF SLAB: Where a slab is
    continuous under perimeter walls, it shall project not less than
    six (6) inches beyond the outside of the wall in order to provide
    space for joining horizontal and vertical membranes.

                   7.2.2.2.1.3 COLUMNS: Where columns occur, there
    shall be no vertical discontinuity or abrupt change in slab
    cross sections. Where slab thicknesses change, they shall do
    so gradually, and the effects of pressure distribution on the
    thinner portions of the slab cross section shall be considered.

                                    IV-35

                   7.2.2.2.1.4 PROTECTION: All membranes shall
    be installed on exterior surfaces of perimeter walls. For floor
    slabs, the membrane shall be installed between the structural
    slab and wearing surface or otherwise placed on a nonstructural
    concrete sub-base at least two (2) inches in thickness to protect
    the membrane and insure its flatness; in the latter case (Figure 3)
    a two (2) inch thick sand-cement screed shall be placed over
    the membrane before laying reinforcing steel for the structural
    slab. If a floor membrane is sandwiched between two structural
    slabs, the membrane shall be positioned at a location that will
    not subject it to excessive overstress conditions.

                   7.2.2.2.1.5 PILE FOUNDATIONS: When spaces
    are supported on pile foundations, the pile shall be positively
    connected to the member which it supports (column, wall, beam, etc.)
    in order to prevent overturning or displacement of the building.
    The penetration required for this positive connection must be
    protected by keyways, asphaltic bitumen pocket, or other accepted
    engineering design. A reinforced concrete sub-slab of not
    less than four (4) inches thick shall be provided over the entire
    area in order to receive the membrane. If the weight of the
    structure is such as to prohibit overturning and displacement of
    the structure thereby permitting complete separation between
    the pile caps and the floor slab, the pile caps shall be inter-
    connected with stabilizing beams, cast monolithically with the
    sub-slab.

              7.2.2.2.2 MATERIALS: For the purpose of these
    Regulations, a membrane shall be any layered sheet construction
    of tar/asphalt bitumen and felts, at least 3-ply in thickness
    neoprene-coated nylon fabric, other approved sheet material, or
    multiple applied hydrolithic coatings of asphaltic bitumens.
    All applicable ASTM standards shall apply to Type A membranes and
    their component parts.

                   7.2.2.2.2.1 PERMEABILITY: Type A membrane shall
    permit passage of no more than three (3) pounds of water per 1,000
    square feet in 24 hours at 40 psi.

                   7.2.2.2.2.2 PLASTIC WATERPROOFING MATERIALS:
    Various plastic materials, including, among others, polyethylene,
    PVC, polyurethane, and polyisobutylene, shall be permitted in
    sufficient thicknesses in sheets or coatings. In certain cases
    the Building Official may require less protection beneath plastic
    than the concrete sub-base required in paragraph 7.2.2.2.1.4.

              7.2.2.2.3 INSTALLATION:

                   7.2.2.2.3.1 APPLICATION: All Type A membrane
    waterproofing shall be applied by a certified roofing or water-
    proofing contractor.

                                IV-36

                   7.2.2.2.3.2 TURNS: Turns at corners, both
    vertical and horizontal, shall be made with chamfers and fillets
    of not less than two (2) inches dimension on any side.

                   7.2.2.2.3.3 SEAMS: Membrane seams or overlaps,
    if any, shall be thoroughly interleaved and protected in accordance
    with accepted practice, but in no case shall seams or overlaps
    be less than two (2) inches in any direction.

                   7.2.2.2.3.4 PIPES: Points where pipes or ducts
    penetrate waterproofed construction shall be designed to be
    watertight in accordance with accepted engineering practice.

                   7.2.2.2.3.5 JOINTS: Membranes shall be continous
    across expansion, control, and construction joints, which shall
    have waterstops of rubber, copper, plastic, or other suitable
    materials.

                   7.2.2.2.3.6 PROTECTION: Membranes on walls
    shall extend at least three (3) inches above the RFD of the
    protected space and shall be attached with a reglet or covered with
    protective masonry at its upper termination. To protect all
    wall membranes during backfill operations, protection of not
    less than 1/2-inch thickness of cement parging, plastic sheets, or
    other rigid non-cellulose material, installed in a workmanlike
    manner, shall be provided; however, in large projects or where
    the protection required above may not be adequate, the Building
    Official may require protection by some other means.

                   7.2.2.2.3.7 EXCAVATION: Excavation preceding
    construction shall extend a minimum distance of 24 inches beyond
    the exterior wall lines to facilitate construction operations.
    In built-up areas where this requirement cannot be met, excavation
    limits will be as designated by the Building Official.

         7.2.2.3 TYPE A INTEGRALLY WATERPROOFED CONCRETE CONSTRUCTION:
    Type A integrally waterproofed concrete construction shall comply
    with the following requirements for structural prerequisites,
    materials, and installation.

              7.'2.2.3.1 STRUCTURAL PREREQUISITES:

                   7.2.2.3.1.1 CONTINUITY OF STRUCTURE: Structural
    slabs shall be continuous under perimeter walls. Slabs shall be
    designed to act monolithically with perimeter walls, or otherwise
    shall carry them non-rigidly in a recess with mastic V fillings
    and waterstops. (Figure 4.)

                   7.2.2.3.1.2 DEFLECTIONS: To prevent increases
    of permeability in tension zones, the maximum deflection of any
    structural slab or perimeter wall shall not exceed 1/500 of its
    shorter span.

                              IV-37

                                                            7-L1b ,L  , ]L    ;' , , n   -

                                         Reinforced Concrete Column

                Reinforced Concrete
                Structural Floor 1

                                      l   "~/-;  * Membrane Waterproofing

    2" Protective Sand     ,.            :   .; -
    & Cement Screed     -*        .

             Concrete Sub-Base      Angle Fillets

                    TYPE "A" MEMBRANE WATERPROOFING IN FLOOR SLABS

                                        IV-38

                   (a)                (b)

    NON-RIGID PERIMETER WALL AND FLOOR SLAB CONNECTIONS

                           IV-39

                                                 SU~%   10REVISION
                   7.2.2.3.1.3 COLUMNS: Where columns occur, there
    shall be no vertical discontinuity or abrupt change in slab
    cross section. Where slab cross sections change, they shall do
    so gradually, and the effects of pressure distribution on the
    thinner portions of the slab cross section shall be considered.

              7.2.2.3.2 MATERIALS:

                   7.2.2.3.2.1 STRENGTH: All Type A integrally
    waterproofed concrete shall have a seven-day compressive strength
    of at least 3,000 psi and a 28-day compressive strength of 4,000 psi.

                   7.2.2.3.2.2 WATERPROOFING ADMIXTURES: If an
    approved waterproofing admixture is used, the cement content
    required to achieve the strength specifications may not be
    reduced by more than 10%. Approved admixtures shall not reduce
    the compressive strength of the concrete and shall act as a
    densifier and/or to increase workability.

                   7.2.2.3.2.3 JOINTS: Expansion joints shall be keyed
    and provided with waterstops. Construction joints shall be
    provided with waterstops and shall be thoroughly roughened and
    cleaned before continuation of concrete placement.

                   7.2.2.3.2.4 PROTECTION OF FRESH CONCRETE: When
    potentially aggressive groundwater conditions exist, the Building
    Official may require the protection of fresh concrete from contact
    with groundwater for a minimum of 14 calendar days. Protection
    shall be accomplished either by the removal of groundwater or
    by the application of a temporary membrane or surface coating
    (e.g., bitumen or tar emulsion) which, however, need not meet
    standards for permanent protection.

         7.2.2.4 TYPE A INTERIOR LININGS: A Type A interior lining
    forms a continuous internal impervious barrier to protect a structure
    with a concrete floor slab and concrete or reinforced concrete
    masonry unit walls. All Type A interior linings shall conform
    to the following requirements for structural prerequisites,
    materials and installation.

              7.2.2.4.1 STRUCTUAL PREREQUISITES:

                   7.2.2.4.1.1 CONTINUITY OF STRUCTURE: Structural
    slabs below grade shall be continuous under perimeter walls to
    prevent differential settlement and shall be designed to act
    monolithically with the walls; reinforced concrete masonry unit
    walls shall be connected rigidly to slabs with reinforcing steel.

                   7.2.2.4.1.2 COLUMNS: Where columns occur, there
    shall be no vertical discontinuity or abrupt change in slab cross
    sections. Where slab thicknesses change, they shall do so gradually,
    and the effects of-pressure distribution on the thinner portions
    of the slab cross section shall be considered.

                               IV-40

                   7.2.2.4.1.3  DEFLECTIONS:  To prevent cracking
    of the interior lining, the maximum deflection of any structural
    slab or perimeter wall to which the lining is applied shall
    not exceed 1/500 of its shorter span.

              7.2.2.4.2 MATERIALS: For the purpose of these
    Regulations, an interior lining shall be any continuous coating,
    parging, or rendering of a cementious or other approved water-
    proofing material or compound with adequate structural strength
    and impermeability to serve its intended purpose. All relevant
    ASTM standards shall apply to Type A interior lining materials.

                   7.2.2.4.2.1 PERMEABILITY: Type A interior
    linings shall permit the passage of no more than three (3) pounds
    of water per 1,000 square feet in 24 hours at 40 psi.

              7.2.2.4.3 INSTALLATION:

                   7.2.2.4.3.1 APPLICATION: All Type A interior
    lining waterproofing shall be applied by a certified roofing or
    waterproofing contractor.

                   7.2.2.4.3.2 TURNS: Turns at corners, both vertical
    and horizontal, shall be made with fillets of not less than two (2)
    inches dimension on any side.

                   7.2.2.4.3.3 PIPES: Points where pipes or ducts
    penetrate waterproofed construction shall be designed to be
    watertight in accordance with accepted engineering practice.

                   7.2.2.4.3.4 ~JOINTS: Interior linings shall be
    continuous across expansion, control and construction joints, which
    shall have waterstops of rubber, copper, plastic, or other
    suitable material.

                   7.2.2.4.3.5 VERTICAL EXTENT: Interior linings on
    walls shall extend at least 3 inches above the RFD of the
    protected space.

              7.2.2.4 EXISTING SPACES: Spaces in existing buildings
    or structures which become subject to these Regulations may be
    approved as having Type A waterproofing upon submission by
    the Owner of plans and specifications for these spaces prepared
    by a licensed architect or engineer; however, the Building Official
    shall make a thorough inspection of actual site conditions and
    may require that tests be made to demonstrate the adequacy of
    the work before granting this approval.

    7.2.3 TYPE B CONSTRUCTIONS

              7.2.3.1 PERMEABILITY: Type B waterproofing constructions
    shall be substantially impermeable but may pass water vapor and seep

                               IV-41

    slightly during flooding to the RFD. Large cracks, openings,
    or other channels that could permit unobstructed passage of
    water shall not be permitted. In no case shall there be permitted
    the accumulation of more than four (4) inches of water depth
    in such a space during a 24-hour period if there were no devices
    provided for its removal. However, sump pumps shall be required
    to control this seepage.

         7.2.3.2 UPGRADING EXISTING SPACES: Spaces with Type B water-
    proofing construction may be upgraded to Type A through the
    installation of a continuous exterior or interior lining or a
    combination of both, which the Building Official may approve as
    meeting the requirements for permeability of Type A waterproofing.

              7.2.3.2.1 INSPECTIONS: The Building Official shall
    make inspections prior to and upon completion of this work before
    approving the completed work as meeting Type A waterproofing
    requirements. The Building Official may require that tests be
    made to demonstrate the adequacy of the work before granting this
    approval.

    7.2.4 TYPE C CONSTRUCTIONS

         7.2.4.1 NON-WATERPROOFED: Type C waterproofing
    constructions are any which do not satisfy the requirements for
    Type A or B in 7.2.2 and 7.2.3 respectively.

         7.2.4.2 UPGRADING OF SPACES: Non-waterproofed spaces may
    be upgraded to Type A or B waterproofing when the Building
    Official shall approve such work as meeting the standard for
    Type A or B in 7.2.2 and 7.2.3.

              7.2.4.2.1 INSPECTIONS: The Building Official shall
    make inspections prior to, during, and upon completion of this
    work before approving the improvement as Type A or B waterproofing,
    and may require tests be made to demonstrate the adequacy of the
    work before granting this approval.

    SECTION 7.3 STRUCTURAL REQUIREMENTS

    7.3.1 SCOPE

         7.3.1.1 GENERAL: All buildings and structures covered by
    these Regulations and all parts thereof shall be capable of resisting
    all loads required by "The Building Code" and, in addition, all
    loads prescribed in this section, without exceeding the prescribed
    allowable stresses.

    7.3.2 CLASSES OF LOADS

         7.3.2.1 CLASS I LOADS: Reflect the probable effects of
    flooding on structures which are waterproof (WI or W2). These loads

                               IV-42

                                                           lie

    shall be calculated in complete accordance witn t I~ section
    and shall include all water, impact, and soil loads specified
    herein.

         7.3.2.2 CLASS 2 LOADS: Reflect the probable effects of
    flooding on structures which include internal flooding as a means
    of structural protection and which shall be so flooded in accordance
    with Section 7.5. These loads shall be calculated in accordance
    with this section except that only hydrodynamic and impact loads
    must be considered when the interior and exterior water levels are
    equal.

         7.3.2.3 CLASS 3 LOADS: Apply to buildings or structures
    which are to be flooded with floodwater either internally by
    automatic means or externally in partially exposed areas. For
    such internal flooding, Class 3 loads shall coincide with those of
    Class 2. For partially exposed spaces, however, any dependent
    or supporting structural components shall be designed for Class I
    or 2 loads if they are also structural components of any adjacent
    enclosed space, whichever is required; isolated or free-standing
    columns or walls shall meet all criteria of 7.3.9.2.3.

    7.3.3 WATER LOADS

         7.3.3.1 TYPES: Water loads, as defined herein, are loads or
    pressures on surfaces of the buildings or structures caused and
    induced by the presence of floodwaters. These loads are of two
    basic types: hydrostatic and hydrodynamic.

         7.3.3.2 HYDROSTATIC LOADS: Hydrostatic loads are those caused
    by water either above or below the ground surface, free or confined,
    which is either stagnant or moves at very low velocities, or up
    to five (5) feet per second. These loads are equal to the product
    of the water pressure times the surface area on which the pressure
    acts. The pressure at any point is equal to the product of the
    unit weight of water (64 pounds per cubic foot) multiplied by the
    height of the water above the point or by the height to which
    confined water would rise if free to do so. Hydrostatic pressures
    at any point are equal in all directions and always act perpendicular
    to the surface in which they are applied. For the purpose of these
    Regulations, hydrostatic loads are subdivided into the following
    types:

              7.3.3.2.1 VERTICAL LOADS: These are loads acting
    vertically downward on horizontal or inclined surfaces of buildings
    or structures, such as roofs, decks, or floors, and walls, caused
    by the weight of flood waters above them.

              7.3.3.2.2 LATERAL LOADS: Lateral hydrostatic loads are
    those which act in a horizontal direction, against vertical or
    inclined surfaces both above and below the ground surface and tend
    to cause lateral displacement and overturning of the building,
    structure, or parts thereof.

                               IV -43

                                                             Lid~

              7.3.3.2.3 UPLIFT: Uplift loads are those which act
    in a vertically upward direction on the underside of horizontal
    or sloping surfaces of buildings or structures, such as
    basement slabs, footings, floors, decks, roofs and overhangs.
    Hydrostatic loads acting on inclined, rounded or irregular
    surfaces may be resolved into vertical or uplift loads and lateral
    loads based on the geometry of the surfaces and the distribution
    of hydrostatic pressures.

         7.3.3.3 HYDRODYNAMIC LOADS: Hydrodynamic loads, for the
    purpose of these Regulations, are those induced on buildings
    or structures by the flow of floodwater moving at moderate or
    high velocity around the buildings or structures or parts thereof
    above ground level. Such loads may occur below the ground level
    when openings or conduits exist which allow free flow of floodwaters.
    Hydrodynamic loads are basically of the lateral type and relate
    to direct impact loads by the moving mass of water, and to drag
    forces as the water flows around the obstruction. Where application
    of hydrodynamic loads is required, the loads shall be computed or
    estimated by recognized and authoritative methods.

              7.3.3.3.1 CONVERSION TO EQUIVALENT HYDROSTATIC LOADS:
    For the purpose of these Regulations, and for cases when water
    velocities do not exceed 10 feet per second, dynamic effects of
    the moving water may be converted into equivalent hydrostatic
    loads by increasing the depth of water to the RFD by an amount dh,
    on the headwater side and above the ground level only, equal to:

                              dh = a V2 Where
                                    2'

         V is the average velocity of the water in feet per second;
         g is the acceleration of gravity, 32.2 feet per second per
           second;
         a is the coefficient of drag or shape factor. (The value of
           a, unless otherwise evaluated, shall not be less than 1.25.)

    The equivalent surcharge depth dh shall be added to the depth
    measured between the design level and the RFD and the resultant
    pressures applied to, and uniformly distributed across, the vertical
    projected area of the building or structure which is perpendicular
    to the flow. Surfaces parallel to the flow or surfaces wetted
    by the tailwater shall be considered subject to hydrostatic
    pressures for depths to the RFD only.

         7.3.3.4 INTENSITY OF LOADS:

              7.3.3.4.1 VERTICAL LOADS: Full intensity of hydrostatic
    pressures caused by a depth of water between the design level and
    the RFD applied on all surfaces involved.

                               IV -44

             7.3.3.4.2 LATERAL LOADS: Full intensity of hydrostatic
    pressures caused by a depth of water between the design elevations)
    and the RFD applied over all surfaces involved, both above and
    below ground level, except that for surfaces exposed to free water
    the design depth shall be increased by one foot.

             7.3.3.4.3 UPLIFT: Full intensity of hydrostatic pressures
    caused by a depth of water between the design level and the RFD
    acting on all surfaces involved, unless provisions are made to
    reduce uplift intensities as permitted in 7.3.8.

              7.3.3.4.4 HYDRODYNAMIC LOADS: Hydrodynamic loads,
    regardless of method of evaluation, shall be applied at full
    intensity over all above-ground surfaces between the ground level
    and the RFD.

         7.3.3.5 APPLICABILITY: For the purpose of these Regulations,
    hydrostatic loads shall be used in the design of buildings and
    structures exposed to water loads from stagnant floodwaters for
    conditions when water velocities do not exceed five (5) feet per
    second, and for buildings and structures or parts thereof not exposed
    or subject to flowing water. For buildings and structures, or
    parts thereof, which are exposed and subject to flowing water
    having velocities greater than five (5) feet per second, hydrostatic
    and hydrodynamic loads shall apply.

    7.3.5 ALLOWABLE SOIL PRESSURES

         7.3.5.1 APPLICABILITY: Under flood conditions, the bearing
    capacity of submerged soils is affected and reduced by the buoyancy
    effect of the water on the soil. For foundations of buildings
    and structures covered by these Regulations, the bearing capacity
    of soils shall be evaluated by a recognized acceptable method.
    Expansive soils should be investigated with special care. Soils
    which lose all bearing capacity when saturated, or become "liquified,"
    shall not be used for supporting foundations. If a detailed soils
    analysis and investigation is not made, and if bearing capacities
    of the soils are not evaluated as required above, allowable
    soil pressures permitted in "The Building Code" may be used,
    provided those values are reduced 50%.

    7.3.6 STABILITY

         7.3.6.1 OVERTURNING: All buildings and structures covered by
    these Regulations and all parts or elements thereof shall be proportioned
    to provide a minimum factor of safety of 1.50 against failure by
    sliding or overturning when subjected to flood-related loads or
    combined loads. The required stability shall be provided by the
    normal resistive loads allowed by "The Building Code," such as
    frictional resistance between the foundations and the soil, passive
    earth pressure, batter and vertical piles and permanent anchors
    which may be provided. For the purpose of providing stability, only

                               IV-45

                                                    r,7-'

    the dead load shall be considered effective. No use shall
    be made of any resistance, either as weight or frictional or
    passive, from soils which could be removed or displaced by
    excavation, scour or other causes. Similarly, no use shall be
    made of frictional resistance between the foundation and the
    underlying soil in the case of structures supported on piles.

         7.3.6.2 FLOTATION: The building or structure, and all
    appurtenances or components thereof not rigidly anchored to the
    structure, shall have enough weight (deadload) to resist
    the full or reduced hydrostatic pressures and uplift from flood-
    water at the RFD with a factor of safety of 1.33. For provisions
    governing reduced uplift intensities, see 7.3.7. In cases when
    it is not practical to provide the required factor of safety
    against flotation by weight alone, the difference shall be made
    up by providing dependable and permanent anchors that meet the
    approval of the Building Official. Elements which depend on
    anchorage to other portions of the structure shall be anchored to
    a portion or portions of the structure which have the required
    factor of safety against flotation from all contributing elements
    subject to uplift. Apportionment of uplift and resisting forces
    shall be made by a recognized method of structural analysis in
    accordance with accepted engineering practice.

         7.3.6.3 ANCHORAGE: Any building and structure as a whole
    which lacks adequate weight and mass to provide the required factors
    of safety against overturning, sliding, and flotation shall be
    dependably and permanently anchored to the ground. In addition,
    all elements of a building or structure, such as wall, floor slabs,
    girders, beams, columns and other members, shall be dependably
    connected or anchored to form an adequate structural system to
    support the individual members and all the applied loads. Provision
    of adequate anchorage is also essential and required for all tanks
    and vessels, sealed conduits and pipes, lined pits and sumps and
    all similar structures which have negligible weight of their own.

    7.3.7 REDUCTION OF UPLIFT PRESSURES

         7.3.7.1 GENERAL: Uplift forces, in conjunction with lateral
    hydrostatic forces constitute the most adverse flood-related
    loading on buildings and structures and elements thereof. Their
    combined effect determines to a major extent the requirements
    for weight and anchorage of a structure as a whole to assure its
    stability against flotation, sliding and overturning. When uplift
    forces are applied to structural elements of a building or structure,
    such as footings, walls, and particularly basement slabs, they
    generally constitute the critical loading on such elements. In
    the interest of providing economical solutions to the basic
    problem of structurally flood-proofing buildings and structures,
    it is permissible under these Regulations to make provisions for
    effectively reducing uplift forces acting under the structure. The
    plans and design data submitted to the Building Official for
    approval shall show complete and detailed procedures, assumptions,

                               IV-46

    analyses and design information, and specific provisions to
    be incorporated in the work for accomplishing the proposed
    reduction in uplift. Data and design procedures shall be based
    on recognized and acceptable methods of foundation drainage and
    waterproofing. Such provisions shall include, but are not
    limited to, the following items, used alone or in combination,
    as conditions will dictate.

         7.3.7.2 IMPERVIOUS CUTOFFS: Impervious cutoffs are barriers
    installed below the ground line and externally to the perimeter
    of the building or structure for the purpose of decreasing
    seepage quantities and/or reducing existing gradients. Such cutoffs
    must, in all cases where floodwaters will rise above the ground
    level, be connected by suitable impervious blankets or membranes
    to the walls of the building or structure. Cutoffs may consist
    of interlocking steel sheeting, compacted barrier of impervious
    soil, grouted or injected cutoffs, impervious wall of interconnected
    concrete piles or panels, and similar seepage barriers, used
    alone or in combination.

         7.3.7.3 FOUNDATION DRAINAGE: Where impervious cutoffs are
    provided or where suitable foundation conditions exist, effective
    drainage and relief of uplift pressures under buildings and structures
    can be achieved. These foundation materials must be free-
    draining and have the desired degree of permeability. For the
    purpose of these Regulations, foundation drainage is intended to
    consist of the provision of drainage blankets, trenches, and, in all
    cases, drain tiles or perforated drainpipes adjacent to footings
    and under floor slabs. Other methods of foundation drainage,
    such as by means of sumps, well points, or deep wells can be used
    for special applications. Drainpipes shall discharge into a sump
    or suitable collection structure, where the water is collected and
    ejected by sump pumps.

         7.3.7.4 SUMPS AND PUMPS: Spacing, sizing and determination
    of depth of sumps shall be consistent with and correlated to the
    intended drainage system, the estimated amount of seepage and
    drainage yield.

    7.3.8 REQUIREMENTS FOR OTHER FLOOD-PROOFING METHODS

         7.3.8.1 METHODS: A building shall be considered as being
    completely flood-proofed if the lowest elevation of all space(s)
    within the building perimeter is above the RFD as achieved by:
    (1) building on natural terrain beyond the RFD limit line on natural
    undisturbed ground, (2) building on fill, (3) building on stilts, and
    (4) protection by dikes, levees and/or floodwalls. These methods
    may be used alone or in combination to achieve the required degree
    of flood-proofing. Data and design procedures shall, in all cases,
    be based an recognized and acceptable methods of the applicable
    disciplines involved, and the following additional requirements.

                               IV-47

                                                         U 11

         7.3.8.2 FLOOD-PROOFING BY ELEVATING THE BUILDING

              7.3.8.2.1 NATURAL TERRAIN: In addition to the
    requirements of "The Building Code," the building shall be located
    not less than 50 feet back from the line of incidence of the RFD
    on the ground, foundation design shall take into consideration
    the effects of soil saturation on the performance of the foundation,
    the effects of floodwaters on slope stability shall be investigated,
    normal access to the building shall be by direct connections
    with areas above the RFD and all utility service lines shall be
    designed and constructed as required to protect the building and/or
    its components from damage or failure during a flooding event to
    the RFD.

              7.3.8.2.2 BUILDING ON FILL: The building and all parts
    thereof may be constructed above the RFD on an earth fill. Prior
    to placement of any fill or embankment materials, the area upon
    which fill is to be placed, including a five-foot strip measured
    horizontally beyond and contiguous to the toe line of the fill, shall
    be cleared of standing trees and snags, stumps, brush, down timber,
    logs and other growth, and all objects including structures on and
    above the ground surface or partially buried. The area shall be
    stripped of topsoil and all other material which is considered
    unsuitable by the Building Official as foundation material. All
    combustible and noncombustible materials and debris from the
    clearing, grubbing and stripping operations shall be removed from
    the proposed fill area and disposed of at locations above the RFD
    and/or in the manner approved by the Building Official. Fill material
    shall be of a selected type, preferably granular and free-graining,
    placed in compacted layers. Fill selection and placement shall
    recognize the effects of saturation from floodwaters on slope
    stability, uniform and differential settlement, and scour potential.
    The minimum elevation of the top of slope for the fill section shall
    be at the RFD. Minimum distance from any point of the building
    perimeter to the top of the fill slope shall be either 25 feet or
    twice the depth of fill at that point, whichever is the greater
    distance. This requirement does not apply to roadways,
    driveways, playgrounds, and other related features which are not
    part of the building proper. Fill slopes for granular materials
    shall be no steeper than one vertical on one and one-half horizontal,
    unless substantiating data justifying steeper slopes are submitted
    to the Building Official and approved. For slopes exposed to
    flood velocities of less than five (5) feet per second, grass or
    vine cover, weeds, bushes and similar vegetation undergrowth will
    be considered to provide adequate scour protection. For higher
    velocities, stone or rock slope protection shall be provided.

              7.3.8.2.3 BUILDING ON "STILTS": The building may be
    constructed above the RFD by supporting it on "stilts" or other
    columnar type members, such as columns, piers, and in certain
    cases, walls. Clear spacing of support members, measured
    perpendicular to the general direction of flood flow, shall not be less
    than eight (8) feet apart at the closest point. The "stilts"
    shall, as far as practicable, be compact and free from unnecessary

                                IV- 48

    appendages which would tend to trap or restrict free passage of
    debris during a flood. Solid walls, or walled-in columns are
    permissible if oriented with the longest dimension of the member
    parallel to the flow. "Stilts" shall be capable of resisting
    all applied loads as required by "The Building Code" and all
    applicable flood related loads as required herein. Bracing,
    where used to provide lateral stability, shall be of a type that
    causes the least obstruction to the flow and the least potential
    for trapping floating debris. Foundation supports for the "stilts"
    may be of any approved type capable of resisting all applied loads,
    such as spread footings, mats, piles and similar types. In all
    cases, the effect of submergence of the soil and additional
    floodwater-related loads shall be recognized. The potential of
    surface scour around the stilts shall be recognized and protective
    measures provided, determined by a registered Professional
    Engineer.

         7.3.8.3 PROTECTION BY DIKES, LEVEES, AND FLOODWALLS: The
    building shall be considered a floodproofed type when it is pro-
    tected from floodwaters to the RFD by means of dikes, levees, or
    floodwalls, either used alone or in combination, as necessary.
    This protection may extend all around the building where all
    surrounding ground is low, or on one or more sides where high
    ground (above the RFD) exists on the remaining sides. Regardless
    of type and method of construction, dikes, levees, and floodwalls
    shall be designed and constructed in accordance with recognized
    and accepted engineering practice and methods. They shall have
    adequate strength and stability to resist all applied loads and
    shall provide an effective watertight barrier up to the RFD.

              7.3.8.3.1 DIKES AND LEVEES: Dikes and levees shall
    be constructed of suitable selected material, placed and compacted
    in layers to a section that has the required stability and imper-
    meability. Prior to start of placement operations, the area on
    which the dike or levee is to be constructed shall be prepared
    as required in 7.3.8.2.2. In cases where underlying materials
    are highly pervious, it may be necessary to provide impervious
    cutoffs. A filter blanket, drainage ditch and/or trench shall be
    provided along the interior toe of the construction to collect
    seepage through the dike or levee. All seepage and storm
    drainage shall be collected at a sump or sumps where it may be
    pumped out over the dike. Normal surface runoff within and into
    the diked area during nonflood periods may be discharged through
    appropriate drainage pipes and culverts through the dike. Such
    culverts shall have a dependable flap, slide gate, or backflow
    preventing device which would close either automatically or
    manually to prevent backflow during a flood. Scour protection
    measures for dikes and levees shall comply with the requirements
    of 7.3.8.2.2. Clearance from the toe of the dike or levee to the
    building shall be a minimum of 20 feet or twice the height of the
    dike or levee above the interior finished grade, whichever is greater.

                               IV-49

              7.3.8.3.2 FLOODWALLS: Floodwalls may be constructed
    of concrete, steel sheet piling, or other suitable structural
    materials. Regardless of type, the wall shall have adequate
    strength and stability to resist the applied loads. The provisions
    of 7.3.8.3.1 shall be followed, as applicable, regarding removal
    of unsuitable materials, provision of impervious cutoffs,
    provision of seepage and storm drains, drainage ditches, sumps and
    sump pumps, and the minimum clearances from the floodwall to the
    building. It shall be recognized in the drainage provisions that
    substantial amounts of leakage may occur through the interlock of
    a steel sheet piling wall. Adequate expansion and contraction
    joints shall be provided in the walls. Expansion joints will be
    provided for all changes in wall direction. Contraction and expansion
    joints in concrete walls shall be provided with waterstops and
    joint sealing material both in the stem and in the base. Steel
    sheet piling walls may be encased in concrete for corrosion
    protection or shall be coated with a coal tar epoxy coating system
    and periodically inspected and maintained. Steel sheet piling
    walls may be used as the impervious core of a dike.

    SECTION 7.4 CLOSURE OF OPENINGS

    7.4.1 SCOPE

         7.4.1.1 GENERAL: Openings in exterior and interior walls of
    buildings or structures in a Flood Hazard Area which are wholly
    or in part below the RFD shall be provided with waterproof
    closures meeting the requirements of this section.

    7.4.2 TYPES OF CLOSURES

         7.4.2.1 CLASSIFICATION: Closures shall be classified into
    five types according to their compatibility with the waterproofing
    standards of the various flood-proofing classes.

              7.4.2.1.1 TYPE I CLOSURES: Shall form a complete
    sealed barrier over the opening that is impermeable to the passage
    of water at the full hydrostatic pressure of a flood to the RFD.

              7.4.2.1.2 TYPE 2 CLOSURES: Shall form essentially
    dry barriers or seals, allowing only slight seepage during the
    hydrostatic pressure conditions of flooding to the RFD.

              7.4.2.1.3 TYPE 3 CLOSURES: Shall form barriers or seals
    that are impermeable to the passage of waterborne contamination
    under equalized pressure conditions.

              7.4.2.1.4 TYPE 4 CLOSURES: Shall form barriers to
    the passage of flood-carried debris and the loss of floating items
    from the interior, but are not required to form impermeable seals.

              7.4.2.1.5 TYPE 5 CLOSURES: Are those of existing
    spaces which do not meet the requirements of any of the above
    described types, but are in use as required by "The Building Code."

                              IV-so

    7.4.3  REQUIREMENTS

         7.4.3.1 DESIGN STANDARDS FOR CLOSURE ASSEMBLIES: The
    structural capacity of all closures shall be adequate to support
    all flood loads acting upon its surface. Closure assemblies may
    be fabricated of cast iron, steel, aluminum, or other adequate
    and durable structural material, provided with a continuous support
    around its perimeter, and shall be attached to the building or
    structure at its immediate location of use, i.e., hinged, or slides,
    or in a vertical recess. The closure device shall be capable
    of being set in place with minimal manual effort. Seals, where
    required, shall be gasketed pressure types permanently anchored
    or attached to the structure or to the closure assembly. Closures
    designed to lift into vertical recesses for storage when not in
    use, and/or located so that the open position of the assembly
    will not impede fire exit or the functioning of a fire closure
    assembly, shall be supported in the open position by auxiliary
    supports of safety latches that can be released at times of flooding.
    In the closed position the closure assembly shall engage fixed
    wedging blocks that will force the closure into a tight sealing
    position. The entire closure assembly should be inspected by the
    owner annually and suitably maintained to preserve its waterproof
    and structural quality, or be replaced as required.

          7.4.3.2 FRAMES FOR OPENINGS: Each opening below the RFD shall
    have a metal frame suitable for providing an adequate sealing
    surface and for supporting the flood-proofing closure assembly.
    The frame shall be connected to the adjacent walls and floors and
    provide adequate bearing surface and anchorage to transfer the
    panel loading into the wall. It shall be supported upon adjacent
    walls and support shall be provided around the opening in the
    concrete or masonry wall to transfer the panel load to such inter-
    sections as required.

          7.4.3.3 OPENINGS IN SHAFTS: All buildings or structures
    which have inclosing walls, decks, or shafts with horizontal or
    inclined openings at the top that are at or below the RFD and which
    would inundate WI or W2 spaces shall be provided with Type I
    closure assemblies that can be readily positioned and secured to
    prevent entrance of flood waters. Construction of such openings
    shall provide for permanently affixed doors, wall extensions, gates,
    panels, etc., that are either hinged or on slide tracks to
    facilitate prompt and positive sealing or openings with only
    minimal manual effort. Windows, grilles, vents, door openings, etc.,
    in the side walls of a shaft and below the RFD shall be provided
    with flood-proofing closures meeting the requirements of 7.4.2.

          7.4.3.4 FIRE RESISTIVITY OF CLOSURE ASSEMBLIES: All flood-
    proofing closure assemblies shall have a fire-resistive rating that
    conforms to the requirements of "The Building Code" and the
    particular fire protection requirements for the occupancy group
    and building type of the structure.

                              IV-51

    7.4.4 SPECIAL APPLICATIONS OF CLOSURE ASSEMBLIES

         7.4.4.1 APPLICABILITY: Residences, firms, businesses or
    institutions with fewer than 10 permanent employees, or spaces
    which are or would be unoccupied and unattended in their foreseeable
    normal operation for periods of greater than 72 hours, shall not
    have any window, doorway, or other such opening any part of which
    is below the RFD unless at least one of the following conditions
    is met: (1) Type I and 2 closures are utilized and are fully
    automatic types, (2) Manually installed closure devices meeting
    requirements of the appropriate flood-proofing class are provided
    and are installed in their protective position by the Owner at
    any time in the season of high flood danger during which the space
    will be unoccupied and unattended for periods of longer than
    eight (8) hours. This requirement shall be considered in the
    Owner's Contingency Plan and noted by the Building Official on
    the permit and Certificate of Occupancy. (3) Watertight exterior
    walls, dikes, levees, or floodwalls of adequate design (Section 7.3)
    are constructed to prevent flood waters up to the RFD from
    entering the structure or space.

    SECTION 7.5 INTERNAL FLOODING AND DRAINAGE

    7.5.1 SCOPE

         7.5.1.1 GENERAL: The provisions of this section shall
    apply to the intentional flooding of buildings, structures, and
    spaces with water from potable or floodwater sources for the
    purpose of balancing internal and external pressures to protect
    a structure and/or its components from damage or failure during
    floods up to the RFD.

    7.5.2 INTENTIONAL FLOODING WITH POTABLE WATER

         7.5.2.1 APPLICABILITY: Spaces to be intentionally flooded
    (W3 spaces) to maintain a balanced internal and external pressure
    condition shall be filled automatically with potable water from
    a source provided by the Owner as required by 7.5.2.2 and approved
    by the Building Official. This level of filling shall be equal
    to that of the external flood surface unless a reduction in
    the internal flooding level is requested in writing by the Owner,
    and such approval is granted by the Building Official. The Owner
    shall, together with the written request, submit sufficient evidence
    that full internal flooding is unnecessary to protect the
    structure. The potable water flooding system shall activate and
    operate automatically and completely without human intervention
    and shall act independently of the emergency flooding system
    utilizing floodwaters as required for these spaces by 7.5.2.3.
    An automatic drainage system shall also be provided that will
    assure positive drainage of the space(s) at a rate comparable to
    the reduction of exterior flood height when floodwaters are
    receding.

                               IV-52

         7.5.2.2 POTABLE WATER SOURCES: At any location where
    disruption of water supply service from a public utility may
    occur or such service may be deemed inadequate, the Building
    Official shall require the Owner to provide an independent source
    of potable water that will be stored at the location of the
    improvement.

         7.5.2.3 SAFEGUARD AGAINST FAILURE OF POTABLE WATER FLOODING
    SYSTEM: Where intentional flooding with a potable water flooding
    system is used for maintaining the structural integrity of buildings,
    structures, or spaces during flood events to the RFD. an emergency
    (backup) flooding system utilizing floodwaters shall be provided
    and maintained in a state of readiness for automatic implementation
    in event of failure of the primary potable water flooding system.
    The emergency flooding system shall comply with all requirements
    of 7.5.3.

    7.5.3 AUTOMATIC FLOODING WITH FLOODWATER

         7.5.3.1 APPLICABILITY: Spaces to be intentionally flooded
    with floodwater (W4) shall be provided with the necessary
    equipment, devices, piping, controls, etc., necessary for automatic
    flooding during the flood event and drainage of the space(s) when
    floodwaters recede. The automatic flooding and drainage system(s)
    shall utilize approved piping material and have sufficient
    capacity for raising or lowering the internal water level at a
    rate comparable to the anticipated rise and fall of a flood
    that would reach the RFD. These pipe systems shall be
    directly connected to the external floodwaters to maintain a
    balanced internal and external water pressure condition. Provisions
    shall be made for filling the lower portions of the structure
    first and for interconnections through or around all floors
    and partitions to prevent unbalanced filling of chambers or parts
    within the structures. All spaces below the RFD shall be provided
    with air vents extending to at least __feet above the elevation
    of the RFD to prevent the trapping of air by the rising water
    surface. All openings to the filling and drainage systems shall
    be protected by screens or grills to prevent the entry or nesting
    of rodents or birds in the system.

    7.5.4 EMERGENCY FLOODING OF WATERPROOFED SPACES

         7.5.4.1 APPLICABILITY: Spaces which have been waterproofed
    (WI or W2) to the RFD shall be provided with an automatic internal
    flooding system meeting all requirements of 7.5.3 to maintain
    structural integrity during floods which exceed the RFD elevation.
    Inverts shall be located at the RFD elevation unless an increase
    in invert elevation~s) above the RFD is requested in writing by
    the Owner and approval is granted by the Building Official.
    Approvals shall not be granted by the Building Official until
    sufficient evidence has been furnished by the Owner that automatic
    internal flooding at the RFD elevation is not necessary to maintain
    structural integrity. Outlets for the drainage of water from

                                 IV-53

    waterproofed spaces shall be located properly to drain the
    water from all parts of the spaces. To prevent the inflow of
    water at flood levels below the RFD each exterior drainage
    outlet shall be provided with a device for preventing backflow
    of water (flood) through the drainage system. Auxiliary outlets
    shall be provided as required to evacuate all water from upper
    floor levels before draining the lower spaces. All watertight
    walls shall be designed for an internal hydrostatic pressure
    equal to at least two (2) feet of differential head to provide
    for unknown factors that may cause malfunction of the
    required drains.
    SECTION 7.6 FLOORING

    7.6.1 SCOPE
         7.6.1.1 GENERAL: This section shall govern the design and
    use of floor systems and their constituent materials for buildings
    and structures located in a Flood Hazard Area.
         7.6.1.2 BASIS FOR RESTRICTION: Floor systems and flooding
    materials are restricted according to their vulnerability to
    floodwater. For the purpose of these Regulations, vulnerability
    of a given floor or floor material may result from one or more
    of the following: (1) Normal suspended-floor adhesives specified
    for above grade use are water-soluble or are not resistant to
    alkali or acid in water, including ground seepage and vapor.
    (2) Flooring material contains wood or paper products. (3) Flooring
    material is not resistant to alkali or acid in water. (4) Sheet
    type floor coverings (linoleum, rubber, vinyl) restrict
    evaporation from non-WI slabs. (5) Flooring material is impervious
    but dimensionally unstable.
    7.6.2 FLOORING CLASSIFICATIONS
         7.6.2.1 CLASSES OF FLOORING: Floor systems and flooring
    materials are divided into five classes according to their degree
    of vulnerability. Class 1 floorings require conditions of
    dryness provided by WI spaces. Class 2 floors require essentially
    dry spaces which may be subject to water vapor and slight seepage
    that is characteristic of W2 spaces. Class 3 flooring may be
    submerged in clean water during periods of intentional flooding
    as provided by W3 spaces. Class 4 floorings may be exposed to and/
    or submerged in floodwaters in interior spaces and do not require
    special waterproofing protection. Class 5 floors are permitted
    for semi-inclosed or outside uses with essentially unmitigated
    flood exposure.
              7.6.2.1.1 Floors of a given class may be used in any
    application for which a lower-numbered class is permitted by
    these Regulations unless specifically restricted by notation in the
    following chart. For example, concrete (a Class 5 floor) may be
    used whenever floors of Classes 1, 2, 3, 4 or 5 are permitted.

                               IV-54

                                              -u A "'i o SiiaG

              7.6.2.1.2 CLASSES OF TYPICAL FLOORING MATERIALS: The
    following chart is intended as an aid to the Owner, Architect/
    Engineer and the Building Official in assessing the vulnerability
    of typical materials with respect to the criteria stated in
    7.6.1.2. In disputes arising over the merits of particular
    materials or methods of construction, the Building Official shall
    be guided by and decide on the basis of those criteria.

                                                    Class

    Asphalt tiles (A)                                  1
         with asphaltic adhesives                     3
    Carpeting (glued-down types)                      1
    Cement/bituminous, formed-in-place                4
    Cement/latex, formed-in-place                     4
    Ceramic tiles (a)                                 1
         with acid and alkali-resistant grout         3
    Chipboard                                         1
    Clay tile                                         5
    Concrete, precast or in situ                      5
    Concrete tile                                     5
    Cork                                              1
    Enamel felt-base floor coverings                  1
    Epoxy, formed-in-place                            5
    Linoleum                                          1
    Magnesite (magnesium oxychloride)                 1
    Mastic felt-base floor coverings                  1
    Mastic flooring, formed-in-place                  5
    Polyurethane, formed-in-place                     5
    PVA emulsion cement                               1
    Rubber sheets (A)                                 1
         with chemical-set adhesives (B)              5*
    Rubber tiles (A)                                  1
         with chemical-set adhesives (B)              4
    Silicone floors, formed-in-place                  5
    Terrazzo                                          4
    Vinyl sheets (homogenous) (A)                     1
         with chemical-set adhesives (B)              5*
    Vinyl tile (homogeneous) (A)                      1
         with chemical-set adhesives (B)              4
    Vinyl tile or sheets (coated on cork or
         wood product backings)                       1
    Vinyl-asbestos tiles (semi-flexible vinyl) (A)   1
         with asphaltic adhesives                     4
    Wood flooring or underlayments                     1
    Wood composition blocks, laid in cement
         mortar                                       2
    Wood composition blocks, dipped and laid
         in hot pitch or bitumen                      2

    * Not permitted as Class 2 flooring

                               IV-55

    Notes:  (A) Using normally-specified suspended floor (i.e., above-
            grade) adhesives, including sulfite liquor (lignin or
            "linoleum paste"), rubber/Asphaltic dispersions, or
            "alcohol'" type resinous adhesives (cumar, oleoresin).
            (B) e.g., epoxy-polyamide adhesives or latex-hydraulic
            cement.

    SECTION 7.7 WALLS AND CEILINGS

    7.7.1 SCOPE

         7.7.1.1 GENERAL: This section shall govern the design and
    use of wall and ceiling systems and their constituent materials for
    buildings and structures located in a Flood Hazard Area.

         7.7.1.2 BASIS FOR RESTRICTION: Materials treated in this
    section are those which constitute interior walls and ceilings
    including their finishes and structural constructions upon which
    they depend such as sheathing and insulation, and are restricted
    according to their susceptibility to flood damage. For the purpose
    of these Regulations, susceptibility of a given interior material
    or construction is dependent on one or more of the following:
    (1) Normal adhesives specified for above-grade use are water-soluble
    or are not resistant to alkali or acid in water, including ground
    seepage and vapor. (2) Wall or ceiling material contains wood,
    wood products, gypsum products, or other material which dissolves
    or deteriorates, loses structural integrity, or is adversely affected
    by water. (3) Wall or ceiling material is not resistant to alkali
    or acid in water. (4) Material is impervious but dimensionally
    unstable. (5) Materials absorb or retain water excessively after
    submergence.

    7.7.2 WALL/CEILING CLASSIFICATIONS

         7.7.2.1 CLASSES OF WALL/CEILING: Wall and ceiling systems and
    materials are divided into five classes according to the degree
    of vulnerability. Class I materials require conditions of dryness
    provided by Wl spaces. Class 2 materials require essentially
    dry spaces which may be subject to water vapor and slight seepage
    that is characteristic of W2 spaces. Class 3 wall and ceiling
    materials may be submerged in clean water during periods of intentional
    flooding as provided by W3 spaces. Class 4 materials ma~y be exposed
    to and/or submerged in flood waters in interior spaces and do not
    require special waterproofing treatments or protection. Class 5
    wall and ceiling materials are permitted for semi-inclosed or outside
    uses with essentially unmitigated flood exposure.

              7.7.2.1.1 Materials of a given class may be used in any
    application for which a lower-numbered class is permitted by these
    Regulations. For example, concrete (a Class 5 wall/ceiling material)
    may be used whenever materials of Classes 1, 2, 3, 4 or 5 are
    permitted.

                               IV-56

                                              RAMU~SON

         7.7.2.2 CLASSES OF TYPICAL WALL/CEILING MATERIALS: The
    following chart is intended as an aid to the Owner, Architect/
    Engineer and the Building Official in assessing the vulnerability
    of typical materials with respect to the criteria stated in
    7.7.1.2. In disputes arising over the merits of particular
    products or of materials not listed below, the Building Official
    shall be guided by and decide on the basis of those criteria.

                                                  Class

    Asbestos-cement board                              5
    Brick, face or glazed                              5
         Common                                        2
    Cabinets, built in
         Wood                                          2
    Metal                                              5
    Cast stone (in waterproof mortar)                  5
    Cal kboards
         Slate, porcelain glass, lucite glass          5
         Cement-asbestos                               2
         Composition, painted                          2
    Chi pboard I
         Exterior Sheathing Grade                      2
    Clay tile
         Structural glazed                             5
         Ceramic veneer, ceramic wall tile-
           mortar set                                  4
         Ceramic veneer, organic adhesives             2
    Concrete                                           5
    Concrete block                                     5
    Corkboard                                          2
    Doors
         Wood, hollow                                  2
         Wood, lightweight panel construction          2
         Wood, solid                                   2
         Metal, hollow                                 5
         Metal , Kailamein                             2
    Fiberboard panels, Vegetable types
         Sheathing grade (asphalt-coated or
          -impregnated)                               2
         Other I
    Gypsum products
         Gypsum board                                  2
         Keene's cement on plaster                     2
         Plaster, otherwise, including
           acoustical                                 2
         Sheathing panels, exterior grade              2
    Glass (sheets, colored tiles, panels)              4
    Glass blocks                                       5
    Hardboard
         Tempered, enamel or plastic-coated            2
         All other types                               2

                               IV-57

                                                    Cl ass

    Insulation
         Foam or closed cell types                    4
         Batt or blanket types                        1
         All other types                              2
    Metals, non-ferrous (aluminum, copper or
      zinc tiles)                                     3
         Ferrous                                      5
    Mineral fiberboard                                1
    Plastic wall tiles (polystyrene, urea
      formaldehyde, etc.) with waterproof
      adhesives, painted with waterproof grout        3
         Set in water-soluble adhesives               2
    Paint
         Polyester-epoxy and other waterproof
           types                                      4
         All other types                              1
    Paperboard                                        1
    Partitions, folding
         Metal                                        4
         Wood                                         2
         Fabric-covered types                         1
    Partitions, stationary
         Wood frame                                   4
         Metal                                        5
         Glass, unreinforced                          4
                reinforced                            4
         Gypsum, solid or block                       1
    Rubber, mouldings and trim with epoxy-
      polyamide adhesive or latex-hydraulic
      cement                                          4
         All other applications                       1
    Steel, (panels, trim, tile) with waterproof
      applications                                    5
         With non-waterproof adhesives                2
    Stone, natural solid or veneer, waterproof
      grout                                           5
    Stone, artificial nonabsorbent solid or
      veneer, waterproof grout                        5
         All other applications                       2
    Strawboard
         Exterior grade (asphalt-impregnated
           kraft paper)                               2
         All other types                              1
    Wall coverings
         Paper, burlap, cloth types                   1
    Wood
         Solid (boards, sheets, or trim)              2
         Plywood
              Exterior grade                          2
              Otherwise                               1

    SECTION 7.8 ELECTRICAL

    7.8.1 SCOPE

         7.8.1.1 GENERAL: Where buildings or parts of buildings
    and structures extend below the RFD, the electrical materials,
    equipment and installation shall conform to the requirements of
    this section of the Regulations.

    7.8.2 REQUIREMENTS AT LOCATIONS ABOVE AND BELOW THE RFD

         7.8.2.1 MAIN POWER SERVICE: The incoming main commercial
    power service equipment, including all metering equipment, shall
    be located above the RFD. Whenever a building or structure is
    not accessible by a bridge, walkway or other connecting means
    except by boat during periods of flooding to the RFD, a disconnecting
    means for the incoming main commercial power service shall be
    provided at an accessible remote location above the RFD.

         7.8.2.2 STATIONARY AND PORTABLE EQUIPMENT: Switchgear,
    control centers, transformers, distribution and main lighting
    panels in addition to all other stationary equipment shall be
    located above the RFD. Portable or movable electrical equipment
    may be located in any space below the RFD provided that
    equipment can be disconnected by a single plug and socket
    assembly of the submersible type and rated by the manufacturer
    as submersible for not less than 72 hours for the head of water
    above the assembly to the RFD. All disconnect assemblies shall
    be provided with submersible seals attached to the disconnect
    assembly by means of a corrosion resistant metal chain for
    immediate use when needed to insure safety to all personnel during
    a flood. All portable or movable equipment should be de-energized
    and/or moved out of potentially flooded spaces at time of flood
    warning and prior to floodwaters reaching floor levels where
    such equipment is located.

         7.8.2.3 NORMAL AND EMERGENCY LIGHTING CIRCUITS: All circuits,
    except emergency lighting circuits, extending into areas below
    the RFD shall be energized from a common distribution panel located
    above the RFD. All emergency lighting circuits into areas
    below the RFD shall be energized from an independent distribution
    panel also located above the RFD. Each distribution panel shall
    have the capability of being de-energized by a separate single
    disconnecting device.

         7.8.2.4 EMERGENCY LIGHTING REQUIREMENTS: All areas of the
    building or structure that are below the RFD, where personnel
    may be required to conduct emergency operations or work with water
    present on the floor of the area during a flood, shall be pro-
    vided with automatically operated emergency lighting facilities
    and automatically operated electrical disconnect equipment to
    insure that all electrical circuits into these areas, except
    emergency lighting circuits, are de-energized prior to personnel
    working in water. The electrical circuits shall be de-energized

                               IV-59

    prior to the presence of any water on the floor of the affected
    area. All components of emergency lighting systems installed
    below the RFD shall be so located that no component of the
    emergency lighting system is within reach of personnel working
    at floor level in the areas where emergency lighting systems are
    utilized unless the emergency lighting circuits are provided with
    ground-fault circuit interrupters having a maximum leakage
    current to ground sensitivity of five (5) milliamperes. The
    energy for emergency lighting may be furnished by a storage
    battery(s), prime mover-generator system, a separate commercial
    power supply system, the same commercial power system, or a
    combination thereof, subject to the following provisions of this
    section.

              7.8.2.4.1 STORAGE BATTERY (including battery-operated
    lighting units): Battery-operated lighting units shall be completely
    self-contained and shall indicate the state of charge of the
    battery at all times. Lighting units shall automatically provide
    light when the normal source of lighting in the areas is de-
    energized. A sufficient number of emergency lighting units shall
    be provided to enable personnel to perform their assigned
    emergency tasks and to permit a safe exit to areas above the RFD.

              7.8.2.4.2 SEPARATE COMMERCIAL POWER SUPPLY SYSTEM: This
    source of energy shall have a degree of reliability satisfactory
    to the Building Official. A system fed from a substation other
    than that used for the regular supply and not on the same poles
    (except service pole) as the regular supply is deemed to have
    the required degree of reliability. A secondary circuit fed from
    the same primary network circuit as the regular supply shall be
    regarded as a separate system.

              7.8.2.4.3 SAME COMMERCIAL POWER SUPPLY SYSTEM: The system
    shall be an underground secondary network system and a separate
    service shall be connected on the line side of the service switch
    or breaker of the regular service.

         7.8.2.5 LIGHTING CIRCUITS BELOW REGULATORY FLOOD DATUM:
    Lighting circuit switches, receptacles and lighting fixtures
    operating at a maximum voltage of 120 volts to ground may be installed
    below the RFD, provided that these circuits shall be de-energized
    as noted in 7.8.2.4. Should any switch, receptacle or lighting
    fixture be flooded, its particular circuit shall not be re-energized
    until such circuits and devices and/or any part thereof, have been
    disassembled and thoroughly checked, cleaned or replaced, and
    approved for use by qualified personnel.

         7.8.2.6 SUBMERSIBLE EQUIPMENT: Except for the switches,
    receptacles and lighting fixtures noted herein, all other electrical
    equipment permanently installed below the RFD shall be of the
    submersible type rated by the manufacturer for submergence for not
    less than 72 hours for a head of water above equipment to the RFD.

                               IV-60

         7.8.2.7 SUBMERSIBLE WIRING REQUIREMENTS: All electrical
    wiring systems installed below the RFD shall be suitable for
    continuous submergence in water and shall contain no fibrous
    components. Only submersible type splices will be permitted in
    areas below the RFD. All conduits located below the RFD shall be
    so installed that they will be self-draining if subject to flooding
    conditions.

         7.8.2.8 ELEVATORS: All electric power equipment and
    components of elevator systems shall be located above the RFD.
    Automatic type elevators shall be provided with a home station to
    which the elevator will automatically return after use, with home
    station located above the RFD.

         7.8.2.9 ELECTRIC HEATING EQUIPMENT: Electric unit heaters
    installed below the RFD shall be capable of disconnection and removal
    in the manner described for portable electrical equipment in 7.8.2.2.
    Electric controls on gas and oil furnaces located below the RFD
    shall not exceed 120 volts to ground and the control circuits shall
    be automatically de-energized prior to the presence of any water
    on the floor of the affected area in accordance with 7.8.2.4.

         7.8.2.10 SUMP PUMP INSTALLATION: Buildings and structures
    utilizing sump-pumping equipment of any type to keep areas
    within the structure free of water shall be provided with float-
    operated warning alarms that shall act independently of any other
    float- actuated devices used to start and stop pumping equipment.
    All buildings or structures utilizing sump-pumping equipment
    shall be provided with automatic starting standby electrical
    generating equipment located above the RFD. The standby generating
    equipment shall be capable of remaining in continuous operation for
    a period of 125% of the anticipated duration of the design flood.

    SECTION 7.9 MECHANICAL

    7.9.1 SCOPE

         7.9.1.1 GENERAL: All mechanical systems, including heating,
    air conditioning, ventilating, plumbing, sanitary, and water
    systems, in or serving buildings or structures in a Flood Hazard
    Area, shall be designed and installed to comply with the requirements
    of this section.

    7.9.2 HEATING, AIR CONDITIONING AND VENTILATION SYSTEMS

         7.9.2.1 APPLICABILITY: Heating, air conditioning, and
    ventilation systems, including all appurtenances, in buildings or
    structures in a Flood Hazard Area shall be designed and installed
    to comply with the requirements of these Regulations.

         7.9.2.2 LOCATION: Heating, air conditioning, and ve~ntilating
    Equipment should, to the maximum extent possible, be installed in
    areas and spaces of buildings that are above the RFD. When not

                               IV-61

                                        SUSIE~

    feasible, said equipment shall be located in WI or W2 spaces
    (below the RFD) with direct access provided from a location above
    the RFD and shall conform to all requirements of this Section.

              7.9.2.2.1 Heating systems utilizing gas- or oil-fired
    furnaces shall have a float operated automatic control valve
    installed in the fuel supply line which shall be set to operate
    when floodwaters reach an elevation equal to the floor level of
    the space where furnace equipment is installed. A manually
    operated gate valve that can be operated from a location above
    the RFD shall be provided in the fuel supply line to serve as a
    supplementary safety provision for fuel cutoff. The heating
    equipment and fuel storage tanks shall be mounted on and securely
    anchored to a foundation pad or pads of sufficient mass to overcome
    buoyancy and prevent movement that could damage the fuel supply
    line. As an alternate means of protection, elevation of heating
    equipment and fuel storage tanks above the RFD on platforms or
    by suspension from overhead structural systems will be permitted.
    All unfired pressure vessels will be accorded similar treatment.
    Fuel lines shall be attached to furnaces by means of flexible
    or swing-type couplings. All heating equipment and fuel storage
    tanks shall be vented to an elevation of at least 3 feet above
    the RFD. Air supply for combustion shall be furnished if
    required for systems installed in WI or W2 spaces, and piping
    or duct work for such purpose shall be terminated at least
    3 feet above the RFD.

                   7.9.2.2.1.1 All duct work for warm air heating
    systems which is located below the RFD shall be provided with
    emergency openings for internal flooding and drainage of the
    ducts with all openings having covers with gravity operators for
    closure during normal operation. Where duct work must pass
    through a watertight wall or floor below the RFDJ, the duct
    work shall be protected by a mechanically operated closure assembly
    and shall be provided with the operator control position above
    the RFD. The closure assembly in its open position shall not impede
    the normal function of the heating system.

                   7.9.2.2.1.2 Steam or hot water heating pipes
    located below the RFD shall be provided with shutoff valves
    sufficient to isolate the piping system when warning of flooding
    to the RFD is received.

                   7.9.2.2.1.3 Electric heating systems, where
    utilized in Flood Hazard Areas, shall be installed in accordance
    with requirements of Section 7.8.

              7.9.2.2.2 Air conditioning and ventilation systems that
    will be located below the RFD shall be installed in WI or W2 spaces
    only. All installation, piping, duct work, connections, and
    safety features shall conform to the same requirements stated for
    Heating Systems in paragraph 7.9.2.2.1.

                              IV-62

              7.9.2.2.3 Where heating, air conditioning, or ventilating
    systems (as defined in 7.9.2.2) are installed in other than WI or
    W2 spaces, all bearings, seals, shafts, gears, clutches, valves,
    or controls which are not capable of withstanding water or silt
    damage or hydrostatic or hydrodynamic loading shall be provided
    with suitable protective waterproofing enclosures as may be
    required by the Building Official, unless they are considered
    expendable.

              7.9.2.2.4 All fuel supply lines that originate either
    outside of WI or W2 spaces or pass through areas that would be
    flooded shall be equipped with automatic shutoff valves to
    prevent loss of fuel in the event of a line breakage. The wall
    opening shall be made flood-proof by use of imbedded collars,
    sleeves, waterstops, or other means as may be approved by the
    Building Official.

              7.9.2.2.5 Electrical connections to all mechanical
    systems covered by this section shall conform to the requirements
    of Section 7.8.

    7.9.3 PLUMBING SYSTEMS

         7.9.3.1 APPLICABILITY: For the purpose of the Regulations,
    plumbing systems shall include sanitary and storm drainage,
    sanitary facilities, water supply, storm water and sewage disposal
    systems.

              7.9.3.1.1 Except as otherwise provided herein, nothing
    in these Regulations shall require the removal, alteration, or
    abandonment of, nor prevent the continued use of, an existing
    plumbing system.

              7.9.3.1.2 No plumbing work shall be commenced until a
    permit for such work has been issued by the Building Official.
    Application for plumbing permits, denial of permit, time limitation
    on permits, and inspections shall be in accordance with requirements
    of the Building Code.

              7.9.3.1.3 Plumbing materials shall be selected with due
    consideration given to the hydrostatic, hydrodynamic and chemical
    actions of floodwaters on the interior of piping systems, of the
    soil, fill or other materials on the exterior of piping systems,
    on joints, connections, valves, traps, seals (and caulking), and
    fixtures.

         7.9.3.2 BELOW RFD: Sanitary sewer and storm drainage systems
    that have openings below the RFD shall be provided with automatic
    backwater valves or other automatic backflow devices that are
    installed in each discharge line passing through a building exterior
    wall. In WI spaces, manually operated shutoff valves that can be
    operated from a location above the RFD shall also be installed in

                                IV-63

                                         rf-i '      8t

    such lines to serve as supplementary safety provisions for
    preventing backflow in case of automatic backflow device failure
    or line break between the space(s) and the device.

              7.9.3.2.1 Spaces in buildings that are to be protected
    from floodwaters by implementation of the Owneris Contingency
    Plan may utilize standpipes attached to floor drains, cleanouts,
    and other openings below the RFD, and/or manually operated
    shutoff valves or closure devices.

              7.9.3.2.2 Where the state of dryness of a space is
    dependent on a sump pump system, or where the stability of a
    structure during a flood event depends on the relief of uplift
    pressures on building components, all interior storm water drainage
    or seepage, appliance drainage, and underslab drain tile systems
    shall be directly connected to a sump (pump) and discharged at an
    elevation at least 2 feet above the RFD.

              7.9.3.2.3 Sanitary sewer systems, including septic
    systems, that are required to remain in operation during a flood
    shall be provided with a sealed holding tank and the necessary
    isolation and diversion piping, pumps, ejectors and appurtenances
    required to prevent sewage discharge during the flood. The holding
    tank shall be sized for storage of at least 150% of the anticipated
    demand for the duration of a flood to the RFD.

                   7.9.3.2.3.1 All vents shall extend to an elevation
    of at least 3 feet above the RFD.

                   7.9.3.2.3.2 All pipe openings through walls below
    the RFD shall be flood-proofed to prevent floodwater backflow
    through spaces between pipes and wall construction materials.
    (See 7.9.2.2.4.)

                               IV-64

                                  CHAPTER8s a

                                     WIND

         SECTION 8.1 GENERAL: Buildings and structures and every part
         thereof shall be designed to withstand the forces of wind
         pressure assumed in any direction. No allowance shall be made
         for the effect of shielding by other structures. As further
         described in these Regulations, the floor, roof or other
         horizontal bracing system shall be designed and constructed to
         transfer horizontal forces to the parts of the structural frame
         designed to carry the forces to the ground. Where horizontal
         or vertical shear-resisting elements are used to transfer wind
         forces through diaphragm action, the analysis shallI include the
         design of chord members at or near the extremities of the diaphragm
         and the connections used to transfer the forces to the resisting
         elements.  The total shear in any horizontal plane shall be
         distributed to the various elements of the lateral force-resisting
         system in proportion to their rigidities, taking into consideration
         the rigidity of the horizontal bracing system or diaphragm.
         Where roofs or floors are constructed of individual units and
         the transfer of forces to the building frame or foundation is
         totally or partially dependent on such units, the unit and
         attachment shall be capable of resisting applied loads in both
         vertical and horizontal directions.

         SECTION 8.2 VELOCITY PRESSURES:

         8.2.1 WIND SPEED: The basic wind speeds to be used in design
         of buildings and structures shall be as follows:

                                       Basic Wind Speed in MPH at
              Hazard Zone                  30 Feet Above Ground

                   A                                140
                   B                               140
                   C                               140
                   D                               140 at C-D boundary,

         diminishing to 100 mph at inland boundary in accordance with the
         following:

                   VD = 100 +  I40 , where VD =wind speed in Zone D
                              1 +dY
    *                                      ~~~~~~~~~~~~d =distance inland from. C-D boundary

         8.2.2 VELOCITY PRESSURES FOR ORDINARY BUILDINGS AND STRUCTURES:
         Velocity pressures for ordinary buildings and structures are given
         in Table 8-1. These velocity pressures are to be multiplied
         by the pressure coefficients as described in 8.3. The effective
         velocity pressures take into account the dynamic response to gusts

                                  M-'65

                                      TABLE 8-1

                            Effective Velocity Pressure
                       for Ordinary Buildings and Structures
                              in Pounds Per Square Foot

                                                  Wind Speed
        Elevation            100         110         120         130         140
      Less than 30'           26          32          39          45           52
        30 -  40              33          40          48          56          65
        40 -  75              38          46          54          64          74
        75 - 125              44          53          63          74          86
       125 - 175              48          58          69          81          94
       175 - 225              51          62          74          86         100
       225 - 275              53          65          77          90         104
       275 - 325              56          68          80          94         109
       325 - 375              58          70          83          97         112
       375 - 425              59          72          86         100         116
       425 - 475              61          74          88         103         119
       475 - 525              62          75          90         105         122
       525 - 575              64          77          92         108         125
       575 - 625              65          79          94         110         128
       625 - 675              66          80          96         112         130
       675 - 725              67          82          97         114         132
       725 - 775              68          83          99         116         135
       775 - 800              70          85         101  118                137

    To find wind pressure at speed not shown in Table:

                                     Vn     V2
                     where Pvn = pressure not shown in Table

                           Vn = velocity not shown in Table

                           Pv = pressure shown in Table

                           Vn = velocity corresponding to Pv

                  of ordinary buildings and structures in a direction parallel
                  to the wind and should be considered as a minimum. They do not
                  provide for the effects of vortex shedding or instability due
                  to galloping or flutter. For buildings whose height exceeds
                  five times the least horizontal dimension, and for buildings
                  whose dynamic properties tend to make them wind-sensitive, a
                  detailed analysis shall be required.

                  8.2.3 VELOCITY PRESSURES FOR PARTS AND PORTIONS: For parts and
                  portions of structures, such as girts, purlins, windows, doors,
                  curtain walls and cladding, etc., and tributary areas less than
                  200 sq. ft., the velocity pressures given in Table 8-2 shall
                  be used. These values shall be multiplied by the pressure
                  coefficients described in Tables 8-4, 8-5, or 8-6 and 8-7. For
                  tributary areas from 200 to 1000 sq. ft., the values may be
                  reduced linearly to the values in Table 8-1.

                  8.2.4 INTERNAL VELOCITY PRESSURES: Internal velocity pressures
                  are given in Table 8-3. These are to be used with internal
                  pressure coefficients listed in Table 8-8. The pressure is
                  assumed to be uniform on all internal surfaces at a given
                  building height.

                  SECTION 8.3 PRESSURE COEFFICIENTS:

                  8.3.1 GENERAL: In the following sections, pressure coefficients
                  are given for various building shapes and for various building
                  element locations and configurations. These coefficients are
                  to be multiplied by the appropriate velocity pressures given
                  in Section 8.2. (Unit wind load = velocity pressure x pressure
                  coefficient.) In the calculation of design wind loads on
                  buildings and structures or elements thereof, the pressure
                  difference between opposite faces shall be taken into account.
                  Where more than one coefficient is specified, each shall be
                  considered in determining the maximum stresses. The total
                  design wind load on a building or structure may be obtained by
                  calculating the vector sum of the resultant forces that act on
                  its elements.

                  SECTION 8.4 DESIGN OF BUILDINGS AND OTHER ENCLOSED STRUCTURES:

                  8.4.1 GENERAL: All buildings and other enclosed structures
                  shall be designed to withstand the sliding and overturning
                  effects of wind, allowing for the wind that is normal to any wall.
                  The pressure distributions shall be determined by employing the
    *             ~~~~appropriate pressure coefficients specified below.

                  8.4.2 PRESSURE COEFFICIENTS: The pressure coefficients given
                  in this section apply to typical rectangular buildings and other
                  enclosed structures that have vertical walls which may have doors,
                  openable windows, etc. The positive and negative coefficients
                  indicate positive pressure and suction pressure, respectively.

                                          IV-"67

                                                        O~bj'L   &&i 'iff'i1

                                    TABLE 8-2

                   Effective Velocity Pressure for Parts and
                     Portions of Buildings and Structures
                          in Pounds Per Square Foot

                                              Wind Speed
      Elevation            100         110         120         130         140
    Less than 30'           38          46          55          64          74
      30-  75               42          51          61          72          84
      75- 125               49          59          70          82          95
     125- 175               53          65          77          90         104
     175- 225               57          69          82          96         111
     225 - 275              59          72          86         101         117
     275 - 325              61          74          88         104         121
     325 - 375              64          77          92         108         125
     375 - 425              66          80          95         111         129
     425 - 475              67          81          96         113         131
     475 - 525              69          84          99         117         136
     525 - 575              70          85         101         119         138
     575 - 625              72          87         104         122         142
     625 - 675              72          88         104         123         143
     675 - 725              74          90         107         126         146
     725 - 775              76          91         109         128         148
     775 - 800              76          92         110         129         150

                                   11V8B

                                                   SUb~Ij  jU a*2Eb

                                   TABLE 8-3

       Effective Velocity Pressures for Calculating Internal Pressures
                           in Pounds Per Square Foot

                                            Wind Speed
        Height            100        110         120         130        140
    Less than 30'          26         31          37          43         50
      30 -  75             30         36          43          50         58
      75 - 125             36         44          52          61         71
     125 - 175             40         49          58          68         79
     175 - 225             44         53          63          74         86
     225 - 275             47         57          67          79         92
     275 - 325             49         60          71          83         96
     325 - 375             51         62          74          87        101
     375 - 425             54         65          77          90        104
     425 - 475             55         67          80          93        108
     475 - 525             57         69          82          96        111
     525 - 575             59         71          84          99        115
     575 - 625             60         73          87      102           118
     625 - 675             61         74          88         104        121
     675 - 725             63         76          91         106        123
     725 - 775             64         77          92         108        125
     775 - 800             65         79          94         110        128

                                  IV-69

                                   TABLE 8-4                            vu

                       External Pressure Coefficients
                                   for Walls

            Location of Wall                   Pressure Coefficient

    Windward wall                                          0.8
    Leeward wall, both height-
      width and height-length
      ratios of building > 2.5                           -0.6
    Other buildings                                       -0.5
    Side walls                                            -0.7

                                   TABLE 8-5

                       External Pressure Coefficient for
                                 Arched Roofs

                  Rise to Span       Windward         Center       Leeward
                      Ratio           Quarter          Half        Quarter

    Roof on         0 < r < 0.2           -0.9       (-0.7 - r)       -0.5
    elevated      0.2 < r < 0.3   (1.5r - 0.3)*    (-0.7 - r)         -0.5
    structure    0.3 < r < 0.6   (2.75r - 0.68)   (-0.7 - r)          -0.5

    Roof          0 < r < 0.6       1.42r             (-0.7 - r)     -0.5
    springing
    from ground
    level

    * When the rise-span ratio is (0.2 < r 0.3), alternate coefficients
       given by (6r - 2.1) shaZZll also be used for the windward quarter.

                                  IV-70

                                                               i r.   'I'!: ',  ''    r    '6-,  -.- ~:

                                           TABLE 8-6

                         External Pressure Coefficients for Windward
                                     Slope of Gabled Roofs

     h/w     10�-15�      200     250     30�      350     400     450    500    60�

    < 0.3    0.01 0*    0.2      0.25    0.3      0.35    0.4     0.45   0.5    0.01 e
      0.5   -1.0       -0.75   -0.5    -0.2       0.05    0.3     0.45   0.5    0.01 0
      1.0   -1.0       -1.0    -0.8    -0.55   -0.3    -0.05    0.2    0.45   0.01 a
    > 1.5   -1.0                -1.0    -0.9    -0.6    -0.35   -0.1    0.2    0.01 e

    *  Except for roofs rising from ground level (h/w = U), a coefficient of -1.0
       shall be used when 10� < 0 < 15�, 0 = slope in degree, from horizontal,
       h = wall height at eave, w = least width of building normal to ridge.

                                         IV-71

                                             TABLE 8-7

                                   Local Peak External Pressure
                                      Coefficients for Roofs

        Roof Slope                         Ridges and
       6, Degrees*                           Eaves                          Corners

     0- 30                                    -2.4                         (0.1 e - 5.0)
     Greater than 30                          -1.7                             -2.0

    * For arched roofs, 0 shall be taken as the angle between the horizontal and
       the tangent to the roof at the springing.

                                             TABLE 8-8

                          Internal Pressure Coefficients for Buildings

                                                         Openings Mainly In =
              ~* ~ Openings Uniformly           Windward        Leeward        Side
              fl*~  ~      Distributed            Wall           Wall         Wall(s)

     0 to 0.3                  +� 0.3          (0.3 + 1.67n)   (-0.3 - n)   (-0.3 - n)
     Greater than 0.3           + 0.3              0.8             -0.6          -0.6

    * n = ratio of open area to solid area of waZll having majority of openings

                                           IV-72

    8.4.3  EXTERNAL PRESSURE COEFFICIENTS:  The average pressure
    coefficients, listed in Table 8-4, shall be used for calculating
    pressures on external surfaces of buildings.

         8.4.3.1 WALLS - LOCAL PRESSURE COEFFICIENTS: A pressure
    coefficient of -2.0 shall be used at the corners of all walls.
    The pressure shall be assumed to act on vertical strips of
    width 0.1 w, where w is the least width of the building, and the
    computed pressure shall be applied outward. These local pressures
    shall not be included with the net external pressure when
    computing overall loads.

         8.4.3.2 ROOFS:

             8.4.3.2.1 GENERAL: For buildings with a ratio of
    wall height to least width less than 2.5, an external suction
    coefficient of -0.7 shall be used for the roof and the computed
    pressure shall be assumed uniform over the entire roof area.
    For buildings in which the height-width ratio is 2.5 or greater,
    a value of -0.8 shall be used for the entire roof area. These
    coefficients allow for wind parallel to the surfaces of flat,
    arched, and sloped roofs.

             8.4.3.2.2 ARCHED ROOFS: For wind perpendicular to
    the axis of the arch, the coefficients of Table 8-5 shall be used.

              8.4.3.2.3 GABLED ROOFS: For wind perpendicular to
    the ridge of gabled roofs, a pressure coefficient of -0.7 shall
    be used for the leeward slope, together with a coefficient
    for the windward slope which depends on the roof slope and the
    height-width ratio of the building, as given in Table 8-6. These
    coefficients may also be used for shed and other sloped roofs
    of buildings.

             8.4.3.2.4 LOCAL PRESSURE COEFFICIENTS: The pressure
    coefficients given in Table 8-7 shall be used at the ridges,
    eaves, cornices and 90-degree corners of roofs. The pressure shall
    be assumed to act on strips of 0.1 w and the computed pressure
    applied outward at these locations along the ridge, eaves and
    cornices; w = least width of building normal to ridge. These
    local pressures shall not be included with the net external
    pressure when computing overall loads.

             8.4.3.2.5 OTHER LIVE LOADS ON ROOFS: In no case shall
    any roof be designed for less than 20 pounds per square foot live
    load.

    8.4.4 INTERNAL PRESSURE COEFFICIENTS: Pressure acting on the
    interior surfaces of walls and roofs of buildings shall be
    computed by multiplying the velocity pressure obtained from
    Table 8-3 by the internal pressure coefficient obtained in Table 8-8.

                             IV-73

    Both positive and negative coeffients shall be considered in
    calculating the maximum stresses.

    SECTION 8.5 ROOFS OVER NON-ENCLOSED STRUCTURES:

    8.5.1 NET PRESSURE COEFFICIENTS: The net pressure coefficients
    for horizontal or inclined flat roofs over non-enclosed structures,
    such as open-air parking garages, shelter areas, outdoor arenas,
    stadium and theaters, shall be as given in Table 8-9 in which "a"
    is the angle between the wind direction and the plane of the roof
    and `X" is the ratio of the length of the windward edge to the
    distance between the windward and the leeward edges (aspect ratio).

    8.5.2 INWARD AND OUTWARD LOADS: The net pressure coefficients
    given in Table 8-9 are to be used in computing the resultant load
    normal to the surface. The resultant load may act either inward
    or outward.

    8.5.3 ANGLE OF ATTACK: In computing the angle between the wind
    direction and the plane of the roof, the wind shall be assumed to
    deviate by plus or minus 10 degrees from the horizontal.

    8.5.4 VARIATION OF PRESSURE: Pressures will be higher at the
    windward edge than at the leeward edge. To allow for this
    difference, the resultant load shall be assumed to act at the
    center of pressure X/C, as given in Table 8-10, where X is the
    distance to the center of pressure from the windward edge of the
    roof arnd C is the distance between the windward and leeward
    edges.

    SECTION 8.6 CHIMNEYS, TANKS, AND SIMILAR STRUCTURES: Net pressure
    coefficients for chimneys, tanks, and similar structures shall
    be as given in Table 8-11. These coefficients apply to the projected
    area of the structure on a vertical plane normal to the wind
    direction. For slender structures such as flagpoles, a minimum
    net pressure coefficient shall be used if dv'q- < 2.5.

    SECTION 8.7 SIGNS AND OUTDOOR DISPLAY STRUCTURES:

    8.7.1 GENERAL: For the purpose of determining wind loads, all
    signs shall be classified as either open or solid. Signs with
    openings greater than 30% of the gross area shall be classified
    as "1open" signs. Those with openings less than 30% of the gross
    area shall be classified as "solid" signs. The effective velocity
    pressures of Table 8-2 shall be used in calculating design loads.

    8.7.2 SOLID SIGNS:

         8.7.2.1 HEIGHT ABOVE GROUND: Solid signs are classified as
    being at the ground when the ratio g/h is less than 0.25; otherwise,
    they are classified as being above ground (g = distance between the
    bottom of the sign and the ground, and h = the vertical dimension
    of the sign).

                             IV -74

                                     TABLE 8-9                       i-

                          Net Pressure Coefficients for
                                    Flat Plates

     a      1/5       1/3       1/2       1         2         3         5

    100     0.2       0.25      0.3      0.45      0.55      0.70      0.75
    150     0.35      0.45      0.5      0.68      0.83      0.88      0.83
    200     0.5       0.6       0.75     0.92      1.0       0.96      0.9
    250     0.7       0.8       0.95     1.14      1.1       1.04      0.95
    30�     0.9       1.0       1.2      1.32      1.2       1.1       1.0

                                   TABLE 8-10

                    Location of Center of Pressure, X/C, for
                                   Flat Plates

     a               1/5 to 1/2                   1                   2-5

    100                 0.35                    0.30                0.30
    15�                 0.35                    0.30                0.30
    200                 0.35                    0.32                0.32
    25�                 0.35                    0.36                0.40
    30�                 0.35            1       0.30                0.45

                                    IV-75

                                    TABLE 8-11

                          Net Pressure Coefficients for
                               Chimneys and Tanks

                                                               h/d

         Shape                 Type of Surface             1      7     25

    Square (wind              Smooth or rough              1.3   1.4   2.0
    normal to a face)

    Square (wind              Smooth or rough              1.0   1.1   1.5
    along diagonal)

    Hexagonal or              Smooth or rough              1.0   1.2   1.4
    octagonal
     (dv > 2.5)

     Round                     Moderately smooth            0.5   0.6   0.7
     (dVq > 2.5)               Rough (d'/d   0.02)         0.7   0.8   0.9
                              Very Rough
                               (d'/d   0.08)               0.8   1.0   1.2

    NOTE: h = height of structure in feet
           d = diameter or least horizontal dimension in feet
           d'= depth in feet of protruding elements such as ribs and spoilers
           q = the effective velocity pressure in psf from Table 8-1

         8.7.2.2 NET PRESSURE COEFFICIENTS:

             8.7.2.2.1  NORMAL WIND INCIDENCE:  The net pressure
    coefficients, Cf, for solid signs at ground level and above
    ground level, for wind normal to the surface, shall be as given
    in Table 8-12 in which H is the height-to-width ratio of the
    surface, a is the greater dimension, and b is the smaller
    dimension. The computed load shall be assumed to act uniformly
    over the entire sign area.

              8.7.2.2.2 OBLIQUE WIND INCIDENCE: To allow for winds
    oblique to the surfaces of solid signs, the net pressure normal
    to the surfaces shall be assumed to vary linearly from a maximum
    of the windward edge to a minimum of the leeward edge, in
    accordance with the following equations:

                        Max Cf = 1.6 K Cf
                        Min Cf = 0.4 K Cf

    where Cf is the net pressure coefficient for normal incidence,
    and K is a factor depending upon the orientation of the sign
    relative to the wind. The values of K for signs at, and above,
    ground level shall be as follows: K = 1.0 for rectangular signs
    having the shorter edge upwind; K = 1.15 for rectangular signs
    having the longer edge upwind and for square signs.

    8.7.3 OPEN SIGNS: For open signs the net pressure coefficients
    given in Table 8-13 shall be applied to the projected area normal
    to the wind of all exposed members and elements (excluding
    appurtenances and supports which shall be accounted for separately
    by using the appropriate net pressure coefficients for these
    individual elements). Table 8-13 gives net pressure coefficients
    for lattices that are comprised of flat-sided or rounded elements,
    where q is the ratio of the solid area to the gross area, d is the
    diameter in feet of a typical element, and "qi is the velocity pressure
    in psf. Weighted average coefficients may be used for signs with
    both flat-sided and rounded elements.

    8.7.4 APPURTENANCES AND SUPPORTS: The wind loading on appurtenances
    and supports shall be accounted for separately by using the
    appropriate net pressure coefficients. Allowances may be made
    for the shielding effect of one element or another.

    SECTION 8.8 SQUARE - AND TRIANGULAR - SECTION TRUSSED TOWERS:

    8.8.1 TOWERS WITH FLAT-SIDED MEMBERS: The net pressure coefficients
    to be applied to Table 8-1 for square- and triangular-section
    towers with similar faces comprised of structural angle or similar
    flat-sided members, and with the wind normal to a face, shall be as
    given in Table 8-14. Here, p is the ratio of the solid area to
    the gross area of the face and the net pressure coefficient
    applies to the solid area of the face. For square towers, the

                             IV-77

                                    TABLE 8-12

                       Net Pressure Coefficients for Signs
                          At and Above Ground Level, Cf

                                  At Ground Level

    H          < 3        5         8       10        20       30    2 40
    Cf         1.2      1.3     1.42      1.52      1.75     1.84      2.0

                                Above Ground Level

    a/b        � 6       10        16       20        40        60    > 80
    Cf         1.2      1.3     1.42      1.52      1.75     1.84      2.0

                                    TABLE 8-13

                           Net Pressure Coefficients for
                              Latticed Frameworks, Cf

                            Flat-Sided                 Rounded Members
               cP�~   ~      Members
                                                  dVq < 2.5        d,/ > 2.5

    Less than 0.1              2.0                    1.2              0.8
       0.1 to 0.3              1.8                    1.3              0.9
       0.3 to 0.7              1.6                    1.5              1.1

                                   IV48;

                  coefficients do not allow for any unmasked (outstanding)
                  lacing on the side faces; such lacing shall be accounted for
                  separately by using the appropriate net pressure coefficients
                  for these elements and by neglecting the interference effects
                  of the other parts of the tower.

                  8.8.2 TOWERS WITH ROUNDED MEMBERS: For square- and triangular-
                  section towers with round members, and with wind normal to a
                  face, the net pressure coefficients shall be determined by
                  multiplying the above coefficients for towers with flat-sided
                  members by the factors in Table 8-15 for corresponding values
                  of p. Weighted average coefficients may be used for towers
                  with both flat-sided and rounded members.

                  8.8.3 OBLIQUE WIND INCIDENCE:

                       8.8.3.1 SQUARE-SECTION TOWERS: To allow for the maximum
                  horizontal wind-load on square-section trussed towers, which occurs
                  when the wind is oblique to the faces, the wind for normal wind
                  incidence shall be multiplied by a factor of (1.0 + 0.75 cp)
                  (for c~ < 0.5) and shall be assumed as acting along a diagonal.

                       8.8.3.2 TRIANGULAR-SECTION TOWERS: For oblique incidence,
                  the wind force on triangular-section trussed towers (although
                  lower than for normal wind incidence) shall be assumed to be
                  the same as for normal incidence.

                  8.8.4 TOWER APPURTENANCES: The wind-loading on tower appurtenances,
                  such as ladders, conduits, lights, elevators, etc., shall be as
                  calculated by using the appropriate net pressure coefficient
                   for these elements and the effective velocity pressures of Table 8-2.
                  The contribution of these elements to the tower wind-loading
                   shall be based on the effective velocity pressures of Table 8-2.
                  Allowance may be made for shielding effects.

                   8.8.5 TOWER GUYS: The minimum net pressure coefficient for
                  wind normal to the chord of tower guys shall be 1.2. For oblique
                  wind incidence, the net pressure coefficients shall be as given
                   in Table 8-16 in which B is the angle between the wind direction
                   and the chord of the guy, CD is the drag coefficient which defines
                   the horizontal component of the wind forces in the direction of the
                  wind, and CL is a lift coefficient which defines that component
                   acting normal to the wind and in the plane containing the angle B.
                   The coefficients apply to the exposed area of the guys, Ld, L
                   being their chord length and d their diameter. The coefficients
                   shall be used in conjunction with the effective velocity pressures
    *              ~~~~of Table 8-1.

                   8.8.6 PATTERNS IN WIND LOADS: For guyed towers, a reduction of 25%
    *              ~~~~of the design pressure in guy span between guys, shall be made for
                   the determination of maximum and minimum moments and shears. The
                   cantilever portion shall be designed for 125% of the design pressure.

                                            IV-79

                                   TABLE 8-14

              Net Pressure Coefficients for Square - and Triangular -
                               Section Towers, Cf

                               Square Towers           Triangular Towers

      Less than 0.025           4.0                       3.6
      0.025 to 0.45             4.13 - 5.18 ~             3.71 - 4.47 p
      0.45 to 0.7               1.8                       1.7
      0.7 to 1.0                1.33 + 0.67 p             1.0 +

                                   TABLE 8-15

                  Ratio of Drag on Towers with Rounded Members
                    to Drag on Towers with Flat-Sided Members*

                                                         Factor

         Less than 0.3                                2/3
         0.3 to 0.8                                   (0.66 p + 0.47)
         0.8 to 1.0                                   1.0

    *  For drq < 2.5, where d = typicaZ member diameter in feet and
       q = velocity pressure in psf

                                   MIN-80

                                    TABLE 8-16          -

                        Wind-Loading Coefficients for
                                      CD and CL

              100    200    300    40�    50�    600    700    800    900

    CD       0.05   0.1    0.2    0.35   0.6    0.8    1.03   1.16   1.2

    CL       0.04   0.15   0.27   0.36   0.45   0.43   0.33   0.18   0

                                     IN ~s8

    SECTION 8.9 OVERTURNING AND SLIDING:

    8.9.1 OVERTURNING: The overturning moment due to the wind load
    shall not exceed 66-2/3% of the stabilizing moment of the building
    or other structure due to the dead load only, unless the building
    or other structure is anchored so as to resist the excess
    overturning moment without exceeding the allowable stresses for
    the materials used. The axis of rotation for computing the
    overturning moment and the moment of stability shall be taken as the
    intersection of the outside wall line on the leeward side and the
    plane representing the average elevation of the bottoms of the
    footings. The weight of the earth superimposed over footings
    may be used in computing the moment of stability due to dead load.

    8.9.2 SLIDING: When the total resisting force due to friction
    is insufficient to prevent sliding, the building or other
    structure shall be anchored to withstand the excess sliding force
    without exceeding the allowable stresses for the materials used.
    Anchors provided to resist overturning moment may also be
    considered as providing resistance to sliding.

                              IV,82

                                            CHAPTER 9~'

                                          FOUNDATI ONS

                  SECTION 9.1 GENERAL: All buildings and structures constructed
                  within Hurricane Hazard Zones A, B, C or D shall conform to these
                  regulations (with special reference to Chapter 5) and the Building
                  Code.

                  SECTION 9.2 SOIL INVESTIGATION:

                  9.2.1 GENERAL: The classification of the soil at each building
                  site shall be determined when required by the Building Official.
                  This determination is to be made by a Professional Engineer registered
                   in the State of Texas.

                  9.2.2 INVESTIGATION: The soil investigation shall be carried out in
                  accordance with the recommendations of the Soil Mechanics and
                   Foundation Section of the American Society of Civil Engineers.
                  As a minimum requirement for a single family residence, or similar
                   structure, one test hole to a depth of at least 25 feet shall be
                   drilled and penetration tests (or other approved tests) shall be
                   performed to determine the density and bearing capacity of the
                   foundation material. In a residential subdivision planned by a
                   Professional Engineer, adequate tests may be performed to indicate
                   the condition of the foundation material for all of the lots without
                   requiring one test hole per lot, if approved by the Building Official.

                   9.2.3 REPORTS: The soil classification and design-bearing capacity
                   shall be shown on the plans. The Building Official may require
                   submission of a written report of the investigation which shall
                   include, but need not be limited to, the following information:
                   (1) plot showing the location of all test borings and low excavations;
                   (2) description and classification of the materials encountered;
                   (3) elevation of the water table encountered; (4) recommendations
                   for foundation type and design criteria including bearing capacity,
                   provisions to minimize the effects of expansive soils, and the
                  effects of adjacent loads; and (5) expected total and differential
                   settlement.

                   SECTION 9.3 DESIGN REQUIREMENTS:

                   9.3.1 GEN4ERAL: All foundations shall be designed in accordance with
    *              ~~~~the structural requirements of the Hazard Zone in which they are
                   constructed.

                  9.3.2 HAZARD ZONE A: In Hazard Zone A the foundation of all
                  buildings and structures will be designed to resist scour and soil
                  movement, unless positive protection against scour and soil
                  movement are provided. In addition, the foundation must be designed

                                              IV-83

    to safely transfer to the underlying soil all loads due to wind,
    water, dead load, live load, and all other loads (including
    uplift due to wind and water).

    9.3.3 HAZARD ZONE B: Same as Hazard Zone A except no requirement
    for scour or soil movement.
    9.3.4  HAZARD ZONE C:  Same as Hazard Zone B except no battering
    forces.

    9.3.5  HAZARD ZONE 0:  Same as Hazard Zone C except no flooding.

    9.3.6 CONCRETE FOUNDATIONS:

         9.3.6.1  PROTECTION OF REINFORCING STEEL:  In Hazard Zones A,
    B, and C all concrete foundations shall be designed, detailed and
    constructed to provide a minimum of three inches (3") of concrete
    cover.

         9.3.6.2 POSITIVE CONNECTIONS: All foundations shall be
    designed, detailed and constructed to provide positive connections
    between all members, pieces, and parts. These connections shall
    safely transmit all forces (compression, tension or shear) and
    moments required by the design. If reinforcing steel is to be
    welded, a test report must be submitted to prove that the steel is
    weldable.

    SECTION 9.4 CONSTRUCTION REQUIREMENTS:

    9.4.1 GENERAL: All foundations constructed in Hazard Zones A, B,
    C, and D shall be built in accordance with good Engineering practice.
    When required by the Building Official, a Professional Engineer
    registered in the State of Texas shall supervise the construction
    of the building or structure and shall submit periodic construction
    reports to the Building Official.

    9.4.2 INFORMATION REQUIRED DURING CONSTRUCTION: The design
    engineer may be required to furnish to the Building Official any
    portion of the following information during construction: (1) a
    complete pile-driving log; (2) a report on the manufacture of all
    precast members including the stressing operation of prestressed
    members; (3) test reports from a certified laboratory on all
    concrete used, including precast members; and (4) mill certificates
    for structural and reinforcing metals used.

    9.4.3 INFORMATION REQUIRED BEFORE FINAL ACCEPTANCE: When the
    structure is complete, and prior to final acceptance, the design
    engineer shall furnish the Building Official a complete set of
    As-Built drawings, together with his certification that the structure
    has been built in accord with the approved plans and specifications.

                              IV-84

                                          CHAPTER 10                    '
              V~~~~~~~~~~~~~~~~~~~~~~u i41tuI
                                         MASONRY WALLS

                  SECTION 10.1 GENERAL: All masonry walls of buildings and
                  structures within Hazard Zones A, B, C, or D shall be designed,
                  detailed, and constructed in accordance with the Building
                  Code and these regulations.

                  SECTION 10.2 STRUCTURAL INTEGRITY:

                  10.2.1 GENERAL: All masonry walls shall be designed to resist
                  all loads or combination of loads which are applicable in the Hazard
                  Zone in which the structure is located. The walls shall safely
                  transfer these loads to the supporting structure without disintegration
                  or other structural failure.

                  10.2.2 TIE COLUMNS:

                       10.2.2.1 TIE COLUMN SPACING: Concrete tie columns shall be
                  required in exterior walls of unit masonry. Concrete tie
                  columns shall be required at all corners, at intervals not to
                  exceed 20 feet center-to-center of columns, adjacent to any corner
                  opening exceeding four feet in width, adjacent to any wall
                  opening exceeding nine feet in width, and at the ends of free-
                  standing walls exceeding two feet in length. Structurally
                  designed columns may substitute for the tie columns herein
                  required.

                       10.2.2.2 TIE COLUMN DIMENSIONS: Tie columns shall be not
                  less than 12 inches in width. Tie columns having an unbraced
                  height not exceeding 15 feet shall not be less in thickness than
                  the wall nor less than a nominal eight inches, and, where exceeding
                  15 feet in unbraced length, shall be not less in thickness than
                  12 inches. The unbraced height shall be taken at the point of positive
                  lateral support in the direction of consideration or the column
                  may be designed to resist applicable lateral loads based on
                  rational analysis.

                       10.2.2.3 TIE COLUMN REINFORCING: Tie columns shall be
                  reinforced with not less than four #5 vertical bars for 8" x 12"
                  columns nor less than four #6 vertical bars for 12" x 12" columns
                  nor less reinforcing steel than 0.01 of the cross sectional area
    *              ~~~~for columns of other dimensions nor less than may be required to
                  resist axial loads or bending forces. Vertical reinforcing shall
                  be doweled to the footing and splices shall be lapped 30 bar
                  diameters. Columns shall be tied with #2 hoops spaced not more
                  than 12 inches apart.

                                           IV-85

                                                    S~~~~~~~A ~ ~ i

         10.2.2.4 CASTING TIE COLUMNS: In load-bearing walls tie
    columns shall be cast only after masonry units are in place.
    Where masonry walls of skeleton frame construction are laid up
    after the frame has been erected, adequate anchorage designed by
    a Professional Engineer shall be provided. Where structural
    steel members are made fire-resistive with masonry units, the
    panel walls shall be bonded to the fire-resistive materials.

    10.2.3 TIE BEAMS:

         10.2.3.1 TIE BEAM LOCATION: A tie beam of reinforced concrete
    shall be placed in all walls of unit masonry, at each floor or
    roof level, and at such intermediate levels as may be required
    to limit the vertical heights of the masonry units to 16 feet.

         10.2.3.2 TIE BEAM SIZE AND REINFORCEMENT: A tie beam shall
    be not less in dimension or reinforcing than required for the con-
    ditions of loading nor less than the following: A tie beam shall
    have a width of not less than a nominal eight inches, shall have
    a height of not less than 12 inches and shall be reinforced with
    not less than two #5 reinforcing bars in the top and two #5
    reinforcing bars in the bottom of the beam.

         10.2.3.3 CONTINUITY OF TIE BEAM: The tie beam shall be
    continuous. Continuity of the reinforcing in straight runs shall
    be provided by lapping splices not less than 18 inches or by
    adding two #5 bent bars which extend 18 inches each way from the
    corner. Continuity at columns shall be provided by continuing
    horizontal reinforcing in the columns or distance of 18 inches.

         10.2.3.4 TIE BEAM AT GABLE END AND SHED END WALLS: A tie
    beam shall follow the rake of a gable or shed end.

         10.2.3.5 TIE BEAM BOND: The concrete in tie beams shall be
    placed to bond to the masonry units immediately below and shall not
    be separated therefrom by wood, felt, or any other material which
    may prevent bond. Felt paper no wider than the width of the
    cells of the block may be used provided that it is depressed a
    minimum of 2 inches in one cell of each block.

         10.2.3.6 PARAPET WALLS: Masonry parapet walls shall be not
    less than eight inches thick, shall be reinforced with minimum
    tie columns and shall be coped with a concrete beam not less than
    64 square inches in cross section, reinforced with two #4
    reinforcing bars. A parapet wall exceeding five feet in height
    above a tie beam or other point of lateral support shall be
    specifically designed to resist horizontal wind loads.

                              IV -86

                                          CHAPTER 11        i

                                         STEEL & IRON

                  SECTION 11.1 GENERAL: Steel and iron members of buildings and
                  structures constructed in a Hurricane Hazard Zone shall be
                  designed, detailed, and constructed in accordance with the
                  Building Code and these Regulations.

                  SECTION 11.2 COLUMNS: Tubular columns and other primary compression
                  members, excluding secondary posts and struts not subject to
                  bending and whose design load does not exceed 2,000 pounds, shall
                  have a minimum least dimension of 2-112 inches and a minimum wall
                  thickness of 3/16 of an inch.

                  SECTION 11.3 WELDING:  Welding in the shop or field may be done
                  only by persons who have been tested and certified by an approved
                  testing laboratory for the welds to be performed, in accordance
                  with the American Welding Society Standards.

                  SECTION 11.4 INSPECTION: A special inspector shall inspect the
                  welding and high-strength bolting on buildings exceeding 10,000 sq. ft.
                  in area or 3 stories in height or as required by the Building Official
                  because of special conditions.

                  SECTION 11.5 OPEN-WEB STEEL JOISTS:

                  11.5.1  Where the net uplift force is equal to or greater than the
                  load of construction, all web and bottom chord members shall have
                  a minimum slenderness ratio of 200 and be proportioned to accommodate
                  the maximum compression and tensile stresses.

                  11.5.2  The ends of every joist shall be bolted, welded or embedded
                  at each bearing to provide not less resistance in any direction
                  than 50 percent of the rated end reaction.

                  SECTION 11.6 COLD-FORMED STEEL CONSTRUCTION:

                  11.6.1  GENERAL:  All structural members and connections shall be
                  designed, detailed, and constructed to resist the loads applicable
                  to the Hazard Zone in which it is constructed.

                   11.6.2 CONNECTIONS: All connections shall be by welding, riveting,
                  bolting or other approved fastening devices or methods providing
                  positive attachment and resistance to loosening. Metal screws shall
                  not be used without positive provision for resistance to loosening.
    *             ~~~~Fasteners shall be of compatible material, with consideration given
                  to avoiding possible electrolysis.

    *             ~~~~11.6.3  STRUCTURAL SHEETS:

                       11.6.3.1 Decks and panels properly supported by and attached
                  to the building frame, including but not limited to those having

                                                 IV-87

    an approved fill material on their top surface, may be considered
    to act as diaphragms in resisting lateral forces where designed
    as such subject to the other limitations of the Building Code and
    these Regulations, except that metal without fill of less thickness
    than 22 gauge shall not be considered to have diaphragm value.

         11.6.3.2 Poured fill on roof and floor decks shall not be
    assumed to have any structural value to support or resist vertical
    or lateral loads or to provide stability or diaphragm action
    unless so designed.

         11.6.3.3 Positive attachment of sheets shall be provided
    to resist uplift and diaphragm forces. Attachment shall be as
    set forth in Paragraph 11.6.2 and not less frequently than the
    following maximum spacings or as required based on rational analysis
    and/or tests: (1) One fastener shall be placed near the corner of
    each sheet or at overlapping corners of the sheet; (2) Along each
    supporting member, the spacing of fasteners shall not exceed
    8 inches on centers at ends of sheets nor 12 inches on centers at
    intermediate supports; (3) The spacing of edge fasteners between
    panels, and between panels and supporting members parallel to
    the direction of span, where continuous interlock is not other-
    wise provided, shall be not more than 12 inches on centers; and
    (4) Poured lightweight concrete fill will be acceptable as
    continuous interlock.

         11.6.3.4 Wall panels shall be attached as set forth in
    sub-paragraphs 11.6.3.3(1), (2), and (3) preceding.

    11.6.4 NONSTRUCTURAL SHEETS: Steel sheet sections not suitable
    by rational analysis for self-supporting structural sheets shall
    be termed roofing and siding. Roofing and siding shall be used
    only over solid wood sheathing or equivalent backing. Attachment
    shall be as set forth in Paragraph 11.6.3.3 except that connections
    shall not be more than 12 inches on center each way, and except
    that attachment may be by 8d nails or by No. 6 wood screws, in
    accordance with the standards of the National Forest Products
    Associ ati on.

    11.6.5 PROTECTION OF METAL: Steel sheets used in Hurricane Hazard
    Zones shall be protected by being galvanized in accordance with
    ASTM A525 and have a minimum of 1.25 oz. class coating or be
    of an approved alloy or be otherwise coated to provide equal
    durability and protection. Abrasions or damages to the protective
    coating shall be spot-treated with a material and in a manner
    compatible to the shop protective coating.

    11.6.6 WELDING: The fusion welding of structural members and
    structural sheets less than 22 gauge in thickness shall be through
    weld washers not less than 14 gauge in thickness and one inch in
    diameter, contoured if necessary to provide continuous contact, or
    through an equivalent device.

                                IV-88

                                           CHAPTER 12

                                              WOOD

                   SECTION 12.1 GENERAL:  Wood members and their fastenings shall
                   be designed by methods admitting of rational analysis according
                   to established principles of mechanics. All members shall be
                   framed, anchored, tied and braced to develop the strength and
                   rigidity necessary for the purposes for which they are used and
                   to resist the loads imposed as set forth in the Building Code and
                   these regulations.

                   SECTION 12.2 ALLOWABLE UNIT STRESSES:

                   12.2.1 Lumber used for joists, rafters, trusses, columns, beams,
                   etc., shall be of a stress grade not less than 1000 psi nominal
                   extreme fiber stress in bending.

                   12.2.2  Lumber used for studs in exterior walls and interior
                   bearing walls shall be of a stress grade not less than 625 psi
                   nominal extreme fiber stress in bending.

                   12.2.3  Lumber used for studs in interior non-bearing walls shall
                   be of a stress grade not less than 225 psi nominal extreme fiber
                   stress in bending.

                   SECTION 12.3 ANCHORAGE: Anchorage shall be continuous from the
                   foundation to the roof and shall satisfy the uplift requirements
                   of the design wind and/or flood.

                   12.3.1 Sills and base plates, where provided in contact with
                   masonry, shall be of an approved durable species or be treated with
                   an approved preservative and shall be attached to the masonry
                   with 1/2 inch diameter bolts spaced not over 4 feet apart and
                   embedded not less than 7 inches in the masonry.

                   12.3.2 Columns and posts shall be framed to true end bearing and
                   shall be securely anchored against lateral and vertical forces.
                   The bottoms of columns and posts shall be protected against deteriora-
                   tion.

                   12.3.3 Joists fire-cut into a masonry wall shall be anchored to
    *              ~~~~the concrete beam on which they bear.  Such anchors shall be spaced
                   not more than four feet apart and shall be placed at opposite ends
                   across the building on the same run of joists.

                   12.3.4 Joists shall be nailed to bearing plates, where such plates
                   occur, to each other where contiguous at a lap, and to the studs
                   where such studs are contiguous; and ceiling joists shall be nailed
                   to roof rafters where contiguous.

                                              IV-89

    12.3.5  Every roof rafter and/or roof joist shall be anchored
    to the beam or studs on which they bear, and roof rafters
    opposing at a ridge shall be anchored across the ridge as set
    forth in subsection 12.3.7.

    12.3.6 Anchors securing wood to concrete shall be not less than
    1"t x 1/8" steel strap embedded in the concrete and nailed with three
    16d nails to wood members. In lieu of such straps, anchorage
    may be as approved by the Building Official when designed by a
    Professional Engineer.

    12.3.7 Anchors securing wood to wood shall be of I" x 1/8" steel
    strap, nailed to each member with three 16d nails, or shall be a
    commercial anchor approved by the Building Official anchoring each
    member. All anchors and relative nails exposed to the weather
    shall be galvanized.

    SECTION 12.4 STORM SHEATHING: Exterior stud walls shall be sheathed
    to resist the racking load of wind. Tightly fitted, diagonally
    placed, boards not less than 5/8 inch thickness, shall be nailed
    by three 8d common nails to each support for I" x 6" boards and
    four 8d common nails for I" x 8" boards. Plywood wall sheathing,
    1/2 inch thickness, may be used in lieu of boards.

    SECTION 12.5 CANTILEVER ROOF JOISTS: Roof joists may cantilever over
    exterior walls as limited by the allowable stress, but the length
    of such cantilever shall not exceed the length of the portion of
    the joist inside the building, and where the cantilever of tail
    joists exceeds three feet, the roof joist acting as a header shall
    be doubled.

                             IV-90

                                          CHAPTER 13                 .

                                            CONCRETE

                  SECTION 13.1 GENERAL: All concrete members of buildings and
                  structures constructed within Hazard Zones A, B, C, or D shall
                  be designed, detailed, and constructed in accordance with the
                  Building Code and these Regulations.

                  SECTION 13.2 CONCRETE PROTECTION FOR REINFORCEMENT:

                  13.2.1 MEMBERS IN CONTACT WITH GROUND AND BELOW RFD: Concrete
                  members which are constructed against the ground and members which
                  are at or below the RFD shall have not less than three inches of
                  concrete between the steel reinforcment and the concrete outer
                  surface.

                  13.2.2 PRECAST UNITS: Concrete coverage of reinforcement in
                  precast units shall be as set forth in the appropriate standard
                  except that precast cement mortar units may have less cover than
                  otherwise set forth, but not less than 1/8 inch providing:
                   (1) The units are manufactured under the control, certification,
    *             ~~~~and supervision of a Professional Engineer.  (2) Reinforcing shall
                  be galvanized, stainless steel or approved equal. (3) To insure
                  exact final location of the steel, positive and rigid devices
                  for that purpose are employed in the manufacturing process.
                   (4) Cement mortar density shall be not less than 155 pounds per
                   cubic foot, including reinforcing, and the minimum strength
                   shall not be less than 5000 psi in 28 days. (5) Cement mortar
                   shall not contain less than I part cement, by volume, for each
                   two parts of fine aggregate. (6) Fine aggregate shall have a
                  maximum size of 4.76 mm. (7) No coarse aggregate shall be used.
                   (8) Units shall be cast on vibrating forms. (9) Members shall
                   not be in contact with the ground or standing water. (10) Where
                   required, fire-resistivity concrete cover requirement will control.

                   SECTION 13.3 PRECAST UNITS:

                   13.3.1 All precast structural items shall be designed by a
                   Registered Professional Engineer.
                   13.3.2 Only the materials cast monolithically with the units at the
                   time of manufacture shall be used in computing stresses unless
    *             ~~~~adequate and approved shear transfer is provided.

                   13.3.3 The Building Official may promulgate and set forth in
                   writing such reasonable rules for requiring tests to be made by an
    *             ~~~~approved laboratory as he may consider necessary to insure
                   compliance with this Regulation and the Building Code.
                   13.3.4 The Building Official or his representative shall have free
                   access to the plant of any producer at all hours of normal operation,

                                              IV-91

                                                        ri, F

    and failure to permit such access shall be cause for revocation
    of approval.

    13.3.5 All connections shall be designed, detailed and constructed
    to safely transfer all wind, live and dead loads to the supporting
    structure without disintegration or structural failure.

                               I�-92

                                        CHAPTER 14

                                 CLADDING AND GLAZING

               SECTION 14.1 GENERAL: All cladding and glazing of buildings and
               structures constructed within Hazard Zones A, B, C, and D shall
               be designed, detailed and constructed in accordance with the
               Building Code and these Regulations. All exterior cladding,
               wall covering, windows, doors, glass and glazing shall be designed
               to resist loads (including suction) due to the applicable wind
               speeds and to meet requirements of flooding if located below the
                RFD. Connections for these elements must be designed to safely
               transfer the design loads to the supporting structure without
               disintegration or structural failure.

               SECTION 14.2 LIMITS OF SIZE OF GLASS: Regular plate and sheet
                glass used in exterior walls shall not exceed the areas set forth
                in Table 14-1. The table applies for width-to-length ratios from
                2:10 to 10:10. The allowable area of glass other than regular
                plate and sheet used in exterior walls shall not exceed the areas
                obtained by multiplying the areas in Table 14-1 by the following
                factors:

                          Tempered Safety Glass                    4.0
                          Insulating (double glazed)               1.5
                          Rough Rolled Plate                       1.0
                          Lami nated                               0.6
    *                     ~~~~~~~Wire Glass                         0.5
                          Sandblasted or Etched                    0.4

                SECTION 14.3 DOORS AND OPERATIVE WINDOWS IN EXTERIOR WALLS: The
                design and approval of operative windows, sliding doors and
                swinging doors, including their support members in exterior walls
                shall be based on the proposed-use height above grade in
                accordance with Chapter 8 of these Regulations. Maximum glass
                sizes shall comply with Table 14-1.

                                           IV-93

                                           TABLE 14.1        .~,,iK   ( [ ,
                                                                 SILrL' T- \ ,  (:,jtUhf

                               MAXIMUM AREA OF GLASS IN SQUARE FEET
                       Wind Velocity Taken as 140 MPH at 30 Feet Above Grade
                                           Glass Thickness (Inches)
      Height
      Above              1/8 &  3/16 &
      Grade        S.S.  D.S.   13/64  7/32   1/4       5/16      3/8    1/2      5/8      3/4

      0'-5'        7.3   11.4   22.0   27.2   33.8    47.0    60.1    88.2   119.8   150.6
      5'-15'       6.0    9.2   17.6   22.0   27.2    38.2    49.2    72.0    97.7   124.2
     15'-25'       5.0    7.6   15.4   17.6   22.8    31.6    41.1    60.0    80.8   101.4
     25'-35'       4.3    6.8   13.2   16.2   19.8    27.9    36.0    52.9    71.3    89.6
     35'-55'       3.9    6.1   11.8   14.0   17.6    25.0    32.3    47.0    63.9    81.6
     55'-75'       3.5    5.4   10.7   12.9   16.1    22.8    28.7    41.9    57.3    72.7
     75'-100'      3.2    4.9    9.7   11.8   14.7    20.6    26.4    38.9    52.9    66.9
    100'-150'      3.0    4.6    8.8   10.8   13.2    19.1    24.2    35.3    48.5    61.0
    150'-250'      2.6    4.0    7.7    9.4   11.8    16.2    21.3    30.9    41.9    52.9
    250'-350'      2.3    3.5    6.8    8.3   10.4    14.0    19.1    27.2    37.5    47.0
    350'-550'      2.1    3.1    6.1    7.4    9.2    12.9    16.9    24.2    33.1    41.9
    550'-750'      1.8    2.8    5.4    6.6    8.3    11.6    15.4    22.0    30.1    38.9
    750'-1000'     1.7    2.6    5.0    6.1    7.6    10.7    14.0    19.8    27.2    34.5
    over 1000'    1.6    2.5    4.8    5.9    7.3    10.3    13.2    19.1    26.5    33.8

                                             IVA14

                                          CHAPTER 1                 77    ~~

                                         ROOF COVERING

                  SECTION 15.1 GENERAL: All roof covering of buildings located
                  within Hazard Zones A, B, C and D shall be designed, detailed,
                  and constructed in accordance with the Building Code and these
                  Regulations. The roof coverings and the connections to the
                  supporting sheathing, deck, or structural roof member will be
                  such as to provide for safe transfer of all applicable loads to
                  the supporting structure without disintegration or structural
                  failure. In general, all roof coverings shall resist the
                  uplift forces given in these standards with at least a safety
                  factor of 2.

                  SECTION 15.2 PREPARED SHINGLE ROOF COVERINGS:

                  15.2.1 Wood roof decks to which prepared shingles are applied shall
                  be solidly sheathed. Sheathing shall be well seasoned and dry.
                  Sheathing boards shall be at least 1 inch nominal dimension boards
                  not over 6 inches wide. Plywood sheathing shall be at least
                  5/8 of an inch thick.

                   15.2.2 Attic spaces shall be vented with vent openings so placed
                  as to circulate air in all parts of the attic.

                   15.2.3 Nails shall be of sufficient length to extend through the
                  roof deck (sheathing).

                   15.2.4 Thick-butt asphalt shingles shall be nailed in the thick
                   portion of the shingle.

                   15.2.5 All butts or tabs of asphalt shingles shall be securely
                   spotted or tabbed with a plastic, fibrous, asphaltic cement or
                   anchored by clips or locks, and all edges at eaves and gables shall
                   be set in such cement 3 inches back from the edge.

                   15.2.6 Metal drip edges shall be nailed to the roof deck with nails
                   not less than 10 inches on centers.

                   SECTION 15.3 BUILT-UP ROOF COVERINGS:

                   15.3.1 For built-up roof coverings cant strips shall be provided
                   at the angle of roof and vertical surfaces.

                   15.3.2 Built-up roof coverings shall be carried at least 6 inches
                   above the cant strip to a reglet in the parapet and covered with
    *              ~~~~flashing caulked into the reglet.  The reglet may be omitted at
                   parapet walls, provided two layers of felt or the equivalent are
                   carried across the top of the parapet under coping and down the para-
                   pet to the lower edge of the cant strip. The said layers are to run
                   vertically, being properly lapped and cemented to the parapet.

                                              IV-95

    15.3.3 All resinous places in the wood roof deck shall be
    covered with sheathing paper or unsaturated felt.

    15.3.4 The first layer or anchor sheet shall be not less than
    30-pound felt nailed 6 inches on center along a 2-inch lap and nailed
    12 inches on center both ways, in the area between laps with tin
    caps and 1-inch nails; or shall be not less than two layers
    of 15-pound felt lapped 18 inches and nailed through both sheets
    on 6-inch centers along the lap and on 12-inch centers in the
    area between laps with tin caps and 1-inch nails; or, where the
    underside of the roof sheathing is to be exposed and its appearance
    considered, the first layer shall be not less than a 30-pound felt
    or two layers of 15 pound felt nailed 6 inches on centers along the
    rafters with tin caps and 1-1/4-inch nails, and nailed 12 inches
    on centers, both ways, between rafters, with tin caps and 3/4 inch
    nails.
    15.3.5 Each additional sheet above the anchor sheet shall be
    thoroughly mopped between layers with a bituminous compound so
    that no layer touches an unmopped layer. Bituminous compound for
    mopping plys together shall be air-refined asphalt or coal tar
    pitch but shall not be any type of emulsion, cold or cutback
    liquid cement, oil or grease.
    15.3.6 Gravel stop and drip strips, and eave and gable drips
    shall be not less than No. 26 guage galvanized metal, 16 ounce
    copper or 0.024 inch aluminum, with not less than 3-inch flange
    on roof and nailed with not less than 3/4 inch nails spaced not
    more than 6 inches apart.
    SECTION 15.4 ROLL ROOFING:
    15.4.1 Roll roofing shall be applied only over a smooth surface.
    Roll roofing shall not be applied over shingle roofs.
    15.4.2 Roll roofing applied in a single layer shall be spot
    mopped and applied by concealed nail method with a minimum 3-inch
    head lap and a minimum 6-inch end lap properly cemented. Nail
    spacing shall be not less than 4 inches on centers.
    15.4.3 Nails that secure roll roofing to the roof deck shall be
    driven at least 3/4 of an inch from the edge of the sheet.
    SECTION 15.5 TILE ROOFING:

    15.5.1 Tile roofing shall be laid over not less than one layer of
    30-pound asphalt felt securely fastened by nailing with tin caps.
    15.5.2 All tile shall be thoroughly watered with a hose before
    application.
    15.5.3 Every tile shall be laid full length in portland cement
    mortar and, in addition, the first three horizontal courses shall
    be nailed. Under certain conditions additional nailing may be

                               IV-96

    required to prevent tile from slipping. Mortar shall be not
    less than one part cement and three parts sand and not more than
    twenty-five per cent lime by volume.

    15.5.4 All nails for flashing and tiles shall be copper.

    SECTION 15.6 CORRUGATED METAL ROOFING, PROTECTED METAL ROOFING,
    CORRUGATED AND FLAT ASBESTOS CEMENT ROOFING:

    15.6.1 When roofings of the above types are applied to wood roof
    decks they shall be secured with drive screws of sufficient
    length to extend through the roof deck. When applied directly
    to purlins and other roof members, they shall be secured with
    bolted strap fasteners, bolts or stud fasteners. Properly
    designed clip fasteners that are approved may be used in accordance
    with the conditions of such approval. Drive screws at least
    4 inches in length may be used to secure these roofings directly
    to wood purlins.

    15.6.2 Aluminum roofing when fastened to steel roof structure
    shall be insulated against electrogalvanic action.

    SECTION 15.7 INSULATED STEEL DECK ROOFING: Insulated steel deck
    shall be secured by spot welding of clips or spot welding the
    sheets to the steel purlins.

                              IV-97

                          APPENDIX A                      iO

          SELECTED REFERENCES - HAZARD ZONE DELINEATION

    Bodine, B. R., "Storm Surge on the Open Coast: Fundamentals and
          Simplified Prediction." U.S. Army Corps of Engineers
          CERC Tech. Memo 35. 1971.

    Bretschneider, C. L. and J. I. Collins, "Prediction of Hurricane
          Surge: An Investigation of Corpus Christi and Vicinity."
          National Engineering Science Co., Tech Report SN-120:
          Pasadena, California. 1963.

    Cry, Geo. W., "Tropical Cyclones of the North Atlantic Ocean:
          Tracks and Frequencies of Hurricanes and Storms 1871-1963."
          Technical Paper No. 55, Weather Bureau, Department of
          Commerce; 148 pp. 1965.

    Frank, Neil L., "The Hard Facts About Hurricanes." NOAA Magazine,
          No. 4; Pages 4-9. 1974.

    Freeman, J.C., L. Baer, and G.H. Jung, "The Bathystrophic Storm
          Tide." Journal of Marine Research, Vol. 16; pp. 12-22. 1957.

    Ho, Francis P., R.W. Schwerdt, and H.V. Goodyear, "Some Climatological
          Characteristics of Hurricanes and Tropical Storms, Gulf
          and East Coasts of the United States." NOAA Tech. Report
          NWS 15. 1975.

    Hargis, Wm. J. et al., "Methodology for Estimati~ng the Characteristics
          of Coastal Surges from Hurricanes," Technical Report of
          Panel on Coastal Surges from Hurricanes. National Academy
          of Sciences; 34 pp. 1975.

    Jelesnianski, C.P., "Bottom Stress Time-History in Linearized
          Equations of Motion for Storm Surges." Monthly Weather
          Review, Vol. 98, No. 6; pp. 462-478. 1970.

    Jelesnianski, C.P., "Numerical Computations of Storm Surges with
          Bottom Stresses." Monthly Weather Review, Vol. 95, No. 11;
          pp. 740-756. 1967.

    Jelesnianski, C.P., "SPLASH: Landfall Storms," NOAA Tech. Memo
          NWS TDL-46. 1972.

    Miller, B. I., "On the Filling of Tropical Cyclones Over Land."
          National Hurricane Research Project Report No. 66. Dept.
          of Commerce, Weather Bureau. 1963.

    Myers, V. A., "Joint Probability Method of Tide Frequency Analysis."
          ESSA Tech. Memorandum WBTM HYDRO--ll. 1970.

    Reid, Robert 0. and B.R. Bodine, "Numerical Computation of Tide and
          Storm Surges in Galveston Bay." ASCE Journal of the Waterways
          and Harbors SCIV. 1968.

                              IV-98

    Riehl, Herbert,  Tropical Meteorology  (New York, N.Y.:  McGraw-
         Hill Book Co.; 392 pp.) 1954.
    Simpson, R.H., "Hurricane Prediction: Progress and Problems."
          Science, No. 181; pp. 899-907. 1973.

    Simpson, R.H., "Hurricane, Yes or No." NOAA Magazine, Vol. 1,
          No. 3. 1971.

    Simpson, R.H., et al, "Evacuation of Coastal Residents During
          Hurricanes." Report of Miami Federal Executive Board Hurricane
          Shelters Committee to Office of Management and Budget,
          Washington, D.C.   1973.

    Simpson, R.H. and John C. Freeman, "Coastal Hazard Potentials,"
          Proceedings Technical Conference on Coastal Hazards, September
          1976, American Meteorlogical Society, Boston, Massachusetts.
          1976.

    Simpson, R.H. and Roger Pielke, "Hurricane Development and
          Movement: A Survey Paper." Applied Mechanics Reviews,
          May, 1976; pp. 601-609. 1976.

    Simpson', R.H. and J. Simpson, "Hurricanes: Structure, Development,
          Movement and Mitigation." Encyclopedia of Science, Vol. 6
          (New York, N.Y.: McGraw Hill) 1976.

    Simpson, R.H. and J. Simpson, "Why Experiment on Hurricanes."
          Transactions N.Y.  Academy of Sciences 28, No. 8; pp. 1045-1062.
          1966.

    Thom, Herbert C.S., "New Distributions of Extreme Winds in the
          United States." Journal of the Structural Division, Proc.
          ASCE, Vol. 94: ST7; pp. 1787-1801. 1968.

    White, Gilbert F. and Eugene Haas, Assessment of Research on
          Natural Hazards (Cambridge, Mass.: MIT Press; 487 pp.)
          1975.

                               IV-99

                                                             Li!

                           APPENDIX B                   J

     SELECTED REFERENCES - MODEL MINIMUM BUILDING STANDARDS

    ANSI A58.1 Building Code Requirements for Minimum Design Loads
          in Buildings and Other Structures (New York, N.Y.:
         American National Standards Institute) 1972.

    Bahamas Building Code (Nassau, Bahamas: Ministry of Works and
          Utilities).

    Basic Data for the Design of Buildings, Chapter V "Loading"
          (London, England: British Standards Institution).

    "Concrete Shore Protection" (Skokie, Illinois: Portland
          Cement Association).

    Coral Gables Bulkhead Ordinance (Coral Gables, Florida: City
          Commission of Coral Gables).

    "Floodproofing Regulations" (Washington, D.C.: Corps of
          Engineers) 1972.

    "Hurricane Camille Report, August 1969" (Mobile, Alabama:
          Corps of Engineers) May, 1970.

    Hurricane Carla (Denton, Texas: Office of Civil Defense) 1961.

    ICBO Code (Pasadena, California: International Conference of
          Building Officials)

    "Loads, External Forces, and Design Stresses," Japan Building Standard
          Law Enforcement Order; 1959.

    National Building Code (New York, N.Y.: American Insurance
          Association).

    Saffir, Herbert S., "Effects of High Wind on Glazing and Curtainwalls,
          and Rational Design Methods for Glazing and Curtainwalls,"
          presented at USA-Japan Research Seminar on Wind Effects on
          Buildings; Kyoto, Japan. 1974.

    Saffir, Herbert S., "Glass and Curtainwall: Effects of High Winds,
          Required Design Criteria," presented at 4th International
          Conference on Wind Effects on Buildings; London, England. 1975.

    Saffir, Herbert S., "Housing Construction in Hurricane Prone Areas,"
          for United Nations (New York, N.Y.: United Nations) 1971.

    Saffir, Herbert S., "Hurricane Camille - Data on Storm and
          Structural Damage," presented at 3rd International Conference
          on Wind Effects on Buildings; Tokyo, Japan. 1971.

    Saffir, Herbert S., "Hurricane Exposes Structural Flaws," Civil
          Engineering; February, 1971.

                                 IV-100

    Saffir, Herbert S., "The Nature and Extent of Structural Damage
          Caused by Hurricane Camille," for NOAA (Washington, D.C.:
         NOAA) 1972.

    Saffir, Herbert S., "Report on Hurricane Eloise Damage," for
          Texas Coastal and Marine Council (Austin, Texas: Texas
          Coastal and Marine Council).

    "Some Climatological Characteristics of Hurricanes," NOAA Technical
          Report NWS 15 (Washington, D.C.: NOAA).

    South Florida Building Code (Miami, Florida: Board of County
          Commissioners).

    Southern Standard Building Code, Revised (Birmingham, Alabama:
          Southern Building Code Congress).

    Swiss Engineers and Architects Association Shape Factors, 1951,
          as revised by Herbert S. Saffir.

                                   IV-101

                           APPENDIX C

    The following Texas cities have adopted the Southern Standard Building
    Code (1) without modification:

          Beaumont                       League City

          Bridge City                    Orange

          Brownsville                    Nederland

          Clear Lake Shores              Port Aransas

          Friendswood                    Port Arthur

          Groves                         Port Lavaca

          Hitchcock                      Port Neches

          Kemah                          Pear Ridge

          Lakeview                       Texas City

          La Marque                      Webster

    The City of Galveston has adopted the Southern Standard Building
    Code with increased wind pressures as follows:

               Height                    Wind Pressure

           Less than 30'                     30 psf
           31' - 50'                         42 psf
           51' - 99'                         54 psf
          100' - 199'                        60 psf
          All elevations south               75 psf
            of seawall

    The City of Corpus Christi has adopted the Southern Standard
    Building Code with the following modifications:

          1. Added paragraphs concerning "Hurricane Precautions"
              and "Special Hurricane Inspection."

          2. Increased wind loads:

               Height                    Wind Pressure

           Less than 30'                     30 psf
           31' - 50'                         40 psf

          3. Established minimum lumber grade (1200 psi).

                                 IV-102

                         4.  Added requirement for continuous anchorage in
                             timber construction.

                         5. Established requirements for mobile homes.

                         6. Established more restrictive requirement for roof
                             coverings.

                   The town of South Padre Island has a "Building Requirement" which
                   apparently requires:

                         1. A wind load of 45 pounds per square foot at 30
                             feet above existing grade.

                         2. 35-foot piles on the Gulf side, 25 foot piles on
                             the Bay side, and pile penetration of 5' below
                             mean high tide under concrete slabs (no required
                             penetration otherwise).

                         3. Anchorage continuous from foundation to roof.

                   Galveston County, in accordance with legislation concerning
                   National Flood Insurance, has adopted the Southern Standard
    V   ~~~~Building Code as a part of its building regulations.  This
                   document defines flood hazard areas and requires the lowest
                   floor level of all new construction to be above the 100 year
                   flood or 18 inches above natural ground, whichever is higher.
                   Part V of the regulation includes some requirements for
                   structural design and material use.

                   The City of Baytown requires compliance with the Southern
                   Standard Building Code for commercial construction and FHA 300
                   Code (2) for residential construction.

                   Rockport requires compliance only with electrial and plumbing
                   codes.

    �              ~~~~The above information is taken from a survey made by Dr. Charles
                   Hix. This information is included only as a general reference,
                   as in only one instance was the response to the survey provided
    *              ~~~~by a person familiar with building codes and construction
                   practices. Only four of the respondents to the survey furnished
                   copies of ordinances adopting the standard code. In one instance
                   the written response indicated that the standard code was in use
                   without modification and a telephone call to a building official
                   indicated that important modifications had been made to the
                   standard code.

                                               IV-103