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

                                         Appendix M

                                                 AUTOMATED COASTAL FLOOD
                                                   MONITORING NETWORK AND
                                                              WARNING SYSTEM

                                                              Feasibility Analysis
                                                                               and
                                                       Design Recommendations

                                                                        April 19W

                                                                     IMP          I I ro
                                                                     QUO - al L

                     ,nwa@

                                                                      Prepared For:

                                                           CONNECTICUT  DEPARTMENT

                                                      OF ENVIRONMENTAL  PROTECTION

                                                         NATURAL RESOURCES CENTER
                                             ,7

                                                                        Prepared  By:

                                                          L.R. JOHNSTON ASSOCIATES

                                                                                       low
                                                                       Westport,  CT

                  B
                 1
                    9.2
                 -3
                 A88
                 1986

               COVER PHOTOGRAPH:   Clinton, Connecticut, September 27, 1985
                                   during Hurricane Gloria.
                                   Taken by Howard Sternberg, Connecticut
                                   Department of Environmental Protection,
                                   Natural Resources Center

                                                       AUTOMATED COASTAL FLOOD
                                                         MONITORING NETWORK AND
                                                                      WARNING SYSTEM

                                                                   Feasibility Analysis
                                                                                       and
                                                            Design Recommendations

                                                                              April   1986

                                                                             Pro0ared For:

                                                                CONNECTICUT DEPARTMENT

                                                           OF ENVIRONMENTAL PROTECTION

                                                              NATURAL RESOURCES CENTER

                                                                              Prepar*d By:

                                                                L.R. JOHNSTON ASSOCIATES

                                                                              W*stport, CT

                                                         ABSTRACT

                      This study was initiated by a Connecticut interagency Committe6 on Automated
                  Flood Warning to: (1) develop specifications for establishing an automated coastal
                  flood monitoring network which would be compatible with the existing statewide
                  automated riverine flood warning system; and (2) evaluate the feasibility of establishing
                  a State, coastal flood forecast and warning system.

                      There are currently five automated gages in operation along the Connecticut
                  coast that measure and record tide and storm surge levels. At present, data from
                  only one of these gages (Bridgeport) is used as input into the National Weather
                  Service's (NWS) forecasts and warnings. There are no automated wave gages or
                  other long-term measurements of waves along'the Connecticut coast.

                      All coastal flood forecasts and warnings are provided by the NWS, and most of
                  these are based -on meteorological data from large scale weather systems -and
                  specific storms (such as hurricanes). NWS has developed a state-of-the-art numerical
                  model for forecasting storm surge during hurricanes and tropical storms, and this
                  model has recently been applied in Long Island Sound. In contrast, NWS techniques
                  for forecasting wave heights and storm surge in Long Island Sound during extratropical
                  storms are based on limited data and simple statistical models. NWS forecasts and
                  warnings usually are not site specific,, and may apply to the entire Connecticut
                  coast, to all of Long Island Sound, or to a large subarea such as eastern Long
                  Island Sound or western. Connecticut.

                      While it is technically feasible for the State of Connecticut to develop its own
                  models for wave and extratropical, storm surge forecasts, such an approach would
                  be expensive and duplicate NWS responsibilities. This report recommends that the
                  State work with and encourage NWS to upgrade its forecast techniques for wave
                  heights and extratropical storm surge. It also recommends that the State supplement
                  NWS regional forecast data with real-time, site specific storm surge and wave
                  collected data through a network of automated coastal gages.

                      A low cost network of automated, real-time gages to measure tides and storm
                  surge could be deployed that would be compatible with the existing automated
                  riverine flood warning system. Adding wave measurement capability to the network
                  would significantly increase the cost of the system. The addition of wave data
                  also would require some compromi       se in either the compatibility of the coastal
                  monitoring network with the existing riverine system or the type of wave data
                  collected.   Further work is needed.to detail the specific system design if wave
                  data is to be collected as part of the coastal monitoring network.

                      A series of automated tide     and storm surge gages at five permanent s       ites is
                  recommended, along with two additional "roving" gages that can be used to correlate
                  data at many other coastal locations with data collected at one or more of the
                  permanent sites. Three of the permanent gage locations and the two "roving"
                  gages could be used for wave measu,rements.
                      Development of the coastal monitoring network can improve'NWS coastal forecasts
                  and warnings, provide State and local emergency. management personnel, with
                  needed site specific data on actual storm surge and wave conditions, and benefit
                  other potential users such as coastal researchers and recreational and commercial
                  boaters.

                                                                       v

                                                                  CONTENTS

                     ABSTRACT
                     CONTENTS                                                                                        v
                     LIST OF ILLUSTRATIONS                                                                           vii
                     ACKNOWLEDGEMENTS                                                                                ix.
                                                  1.0 INTRODUCTION AND SUMMARY

                     1.1   INTRODUCTION                                                                              1-1
                     1.2   METHODS                                                                                   1-2
                     1.3   FINDINGS                                                                                  1-3
                           1.3.1   Existing   Tide,  Storm   Surge and    Wave   Measurements                        1-3
                           1.3.2   NWS Storm Surge and Wave Height             Forecast and                          1-4
                                        Warning Procedures
                           1.3.3   Connecticut Coastal Flood* Warning          Procedures                            1-4
                           1.3.4   Available and Emerging Technology                                                 1-5
                           1.3.5   Potential Uses of Data from Monito ring,, Network                                 1-7
                           1.3.6   Costs and Benefits                                                                1-7
                     1.4   CONCLUSIONS AND RECOMMENDATIONS
                                                                                                                     1-10
                           1.4.1 Conclusions                                                                         1-10
                           1.4.2   Recommendations                                                                   1 13
                     1.5   RECOMMENDED MONITORING NETWORKS                                                           1-14
                           1.5.1 Number: and Location of Gages                                                       1-14
                           1.5.2   Optional Monitoring Network Designs                                               1-14
                                    2.0 TIDES"AND TIDAL           FLOODING     IN LONG     ISLAND SOUND

                     2.1   TIDAL DATUMS                                                                              2-4
                           TIDAL VARIATION IN LONG ISLAND SOUND                                                      2-3
                     2.3   RELATIVE SEA LEVEL RISE                                                                   2-4
                     2.4   TIDE, STORM SURGE, AND WAVE CHARACTERISTICS IN LONG ISLAND                                2-9
                           SOUND
                           2.4.1 Waves                                                                               2-9
                           2.4.2 Tides and Storm Surge                                                               2-11
                     2.5   COASTAL. FLOODING IN CONNECTICUT                                                          2-20
                           2.5.1   Hurricanes and Tropical Storms (Tropical           Cycldnes),                     2-22
                           2.5.2   Extratropical Storms                                                              2-28
                           2.5.3   Mapping of Coastal Floodplains                                                    2-30.
                           2.5.4   Flood Damages                                                                     2-31

                                    3.0 FLOOD FORECASTS, AND WARNINGS IN CONNECTICUT

                     @3.1  RIVERINE FLOOD FORECASTS'AND WARNINGS                                                     3-1
                           3.1.1 National Weather        Service ALERT      Systems                                  3-1
                           3.1.2 Connecticut Automated, Flood, Warning System                                        3-3
                     3.2   COASTAL FORECASTS AND WARNINGS FOR'CONNECTICUT AND LONG                                   3-4
                           ISLAND SOUND
                           3.2*1 NWS Procedures                                                                      3-4
                           3.2.2 State of Connecticut Procedures                                                     3-10
                           3.2.3 Municipal Procedures                                                                3-10

                                                                     v

                                                      CONTENTS (Contd)

                             4.0: REVIEW OF AVAILABLE TECHNOLOGY AND PROGRAMS

                  4.1    STORM SURGE AND WAVE MODELS                                                              4-1
                         4.1.1 Storm Surge Models                                                                 4-1
                         4.1.2 Wave Forecasting/Hindeasting Models                                                4-7
                  4.2    INSTRUMENTATION                                                                          4-8
                         4.2.1 Tide and Storm Surge Measurements                                                  4-9
                         4.2.2 Wave Measurements                                                                  4-14
                         4.2.3 Meteorological Measurements                                                        4-17
                         4.2.4 Data Transmission, and Processing                                                  4-17
                  4.3'   C0&rAL M0NrI`OR[NG, FORBCAST AND WARNING PROGRAMS                                        4-18
                         4.3.1 Federal Programs Activities                                                        4-19
                         4.3.2 Real-Time Monitoring Networks                                                      4-23
                         4.3.3 Long Island Sound Water Quality Program                                            4-31

                                      5.0: FLOOD MONITORING NETWORK DESIGNS

                  5.1    DESIGN CRITERIA                                                                          5-1
                  5.2    NUMBER AND LOCATION OF GAGES                                                             5-2
                         5.2.1 Tides and Storm Surge                                                              5-2
                         5.2.2 Waves                                                                              5-3
                  5.3    ALTERNATIVE NETWORK DESIGNS                                                              5-5
                         5.3.1  Cautions on Cost Estimates                                                        5-6
                         5.3.2  Tide and Storm Surge Measurements: ASERT Compatible Network                       5-6
                         5.3.3  Tide, Storm Surge and Wave Measuremenst: ASERT Compatible                         5-14
                         5.3.4  Tide, Storm Surge and Wave Measurements% Two Networks                             5-19
                         5.3.5  Tide, Storm Surge and Wave Measurements: Independent from
                                     ASERT                                                                        5-25
                  5.4    IMPLEMENTATION OF MONITORING NETWORK                                                     5-24
                         5.4.1 Establishment of Gage Stations                                                     5-24
                         5.4.2  Getting Information to Users                                                      5-25
                  5.5    MAIN]rENANCEPFCGRAM                                                                      5-26
                         5.5.1 Maintenance Program                                                                5-27
                         5.5.2 Maintenance Schedule                                                               5-29
                         5.5.3  Maintenance Costs                                                                 5-31

                                      6.0 CONCLUSIONS AND RECOMMENDATIONS

                  6.1    EXISTING MONITORING, FORE)CAST AND WARNING SMUM                                          6-1
                         6.1.1 Planned Improvements to Existing Technology and Programs                           6-1
                         6.1.2 Opportunities to Further Enhance Existing Programs                                 6-2
                         6.1.3 Achievement of State Objectives Through Existing Programs                          6-3
                  6.2    NEW PROGRAMS AND ADDITIONAL IMPROVEMENTS TO EXISTING PROGRAMS                            6-4
                  6.3    REAL-TIME COASTAL FLOOD, MON1710RING NErWORK                                             6-5-
                         6.3.1 Type of Monitoring Network                                                         6-5
                         6.3.2 Use of Data from Real-Time Monitoring Network.                                     6-6
                  6.4    FORECASTS AND WARNINGS FOR SIORM SURGE AND WAVES                                         6-6

                                                          APPENDICES

                  APPENDIX A: SPECIFICATIONS FOR ASERT SYSTEM
                  APPENDIX B: STORM SURGE AND WAVE MODELS
                  APPENDIX C: GLOSSARY OF ABBREVIATIONS
                  APPENDIX D:        REFERENCES

                                                                 vi i

                                                      LIST OF ILLUSTRATIONS

                    Figure  2.1     Relative Heights of Several Tidal        Datums (Semidurnal Tide)         2-2
                    Figure  2.2     Tidal. Ranges Along the Connecticut Coast                                 2-5
                    Figure  2.3     Mean Sea Level Rise for Northern East Coast                               2-6
                    Figure  2.4     Yearly Mean Sea Level Recorded at Long Term Tide
                                    Gages in Long Island,Sound                                                2-6
                    Figure  2.5     Wave Characteristics                                                      2-10
                    Figure  2.6     Existing Recording Tide Gages in        Long Island Sound                 2-14
                    Figure  2.7     Typical NOS Tide Station Instal      'lation                              2-15
                    Figure  2.8     Typical Analog-to-Digital Recorder                                        2-16
                    Figure  2.9     Recording Tape Showing Time Divisions and Binary-Coded,
                                    Digital Punch Out                                                         2-16
                    Figure  2.10    Typical Bubbler Gage Installation                                         2-18
                    Figure  2.11    Typical Tide Record from Analog Recorder                                  2-18
                    Figure  2.12    Tracks of Seven Selected Hurricanes Crossing or
                                    Approaching Long Island Sound                                             2-24
                    Figure  2.13    Tropical Storms and Hurricanes        Passing Near
                                    Long Island Sound                                                         2-25
                    Figure  2.14    Expected Number of Tropical Storms and Hurricanes
                                    per 100 Years Impacting the Long Island Sound Region                      2-26
                    Figure  2.15    Selected Storm Surges at Stamford Harbor,
                                    Stamford, Connecticut                                                     2-29
                    Figure  2.16    FEMA Flood Insurance.Rate Maps for Section of
                                    the Milford Coastline                                                     2-32
                    Figure  3.1     Sample Storm Surge Forecast Guidance: Teletype Message
                                    to Weather Service Forecast Offices                                       3-7
                    Figure  3.2     Forecast for Hurricane Gloria, Showing Probabilities
                                    of Landf all                                                              3-9
                    Figure  3.3     Connecticut Communities with NAWAS and COLLECT Systems                    3-11
                    Figure  304     Connecticut Warning Flow Chart                                            3-12
                    Figure  4.1     Comparison of Forecast Vs. Observed Storm Surge at
                                    Stamford, Connecticut                                                     4-3
                    Figure  4.2     SLOSH Basins Along the Gulf of, Mexico and Atlantic.
                                    Coastlines                                                                4-6
                    Figure  4.3     Typical Pressure Transducer Type Tide Recorders                           4-12
                    Figure  4.4     Acoustic Type Tide Gage                                                   4-13
                    Figure  4.5     Typical Wave Measurement Gages                                            4-15
                    Figure  4.6     Sample Analysis of Wave Parameters                                        4-16
                    Figure  4.7     National Ocean Service NGWLMS System                                      4-22.
                    Figure  4.8     Sample Display of Tidal Data from New York Harbor
                                    Tidal Gage System                                                         4-26
                    Figure  4.9     Sample Display from Tidal Gage in San Francisco'Bay;
                                    ALERT Type Network                                                        4-28
                    Figure  5.1     Locations of Permanent Gage Stations          for Tide and Storm
                                    Surge Measurements                                                        5-9
                    Figure  5.2     Typical Gage Station Installation                                         5-11
                    Figure  5.3     Radio Telemetry Network                                                   5-12
                    Figure  5.4     Locations of Permanent Gage Stations          for Tide, Storm
                                    Surge, and Wave Measurements                                              5-15
                    Figure  5.5     Examples of Monthly Wave Data, West           Coast Measurement
                                    Network                                                                   5-22
                    Figure  5.6     Examples of Yearly Wave Data, West Coast Measurement
                                    Network                                                                   5-23

                                                             v

                                              LIST OF ILLUSTRATIONS (Cont'd)

                   Table 1.1      User Benefits from a Real-Time Coastal Monitoring
                                  Network                                                               1-9
                   Table  2.1     EPA Scenarios of Future Sea Level Rise                                2-8
                   Table  2.2     National Ocean Service Subordinate      Tide  Gage Locations
                                  in Long Island Sound                                                  2-21
                   Table  2.3     Saffire/Simpson Hurricane Scale                                       2-23
                   Table  2.4     Structures Located in V-Zone                                          2-33
                   Table  5.1     Summary of Alternative Network Designs                                5-7
                   Table  5.2     Sample Maintenance Schedule                                           5-32
                   Table  5.3     Estimated Maintenance Costs                                           5-32

                                                         1X

                                                ACKNOWLEDGMENTS

                    The authors wish to thank the many individuals in Federal, State and local
                 agencies and private organizations who provided information for this report.
                 Special thanks are extended to the members of the subcommittee on Coastal
                 Flood Warning-who supervised this project:

                    Ted Hart, Connecticut Department of Environmental Protection, Water Resources
                         Unit
                    Ralph Lewis, Connecticut Department of Environmental Protection, Natural
                         Resources Center
                    Todd Mendell, National Weather Service, Northeast River Forecast Center
                    Tom Oullette, Connecticut Department of Environmental Protection, Coastal
                         Area Management
                    Cynthia Rummel, Connecticut Department of Environmental Protection, Natural
                         Resources Center
                    Allan Williams, Connecticut Department of Environmental Protection, Natural
                         Resources Center

                    Principal authors of this report are Larry R. Johnston, L. R. Johnston
                 Associates, and David G. Aubrey, Ph.D., Woods Hole Oceanographic Institution.
                 Additional assistance was provided by Wayne Spencer of WHOI and Stanley Humphries,
                 consulting coastal geologist.

                    Funding for this  project was provided by the Federal Emergency Management
                 Agency, State Assistance Program., under a Cooperative Agreement with the
                 Connecticut Department of Environmental Protection, The substance and findings
                 of this work are dedicated to the public. The author and. publisher are solely
                 responsible for the accuracy of all statements and interpretations.             Such
                 statements and interpretations do      not necessari ly reflect the views of the
                 Federal government.

                    Mention of commercial enterprises or brand names does not constitute endorsement
                    or imply preference by the authors, publisher, or Federal government.

                                           1.0s INTRODUCTION AND SLIMMARY

                  Ll INTRODUCTIO

                        Automated flood warning systems were originally developed           by the   National
                  Weather Service (NWS) during the late 1970's in order to in.cre           ase the   amount
                  of warning time available to people          who live and work in      the floodplains of
                  rivers subject to flash floods. This       NWS system, known as       ALERT (Automated
                  Local Evaluation in Real-Time), relies on recent advances in microprocessor
                  and computer technology to provide        accurate, real-time information on precipi-
                  tation amounts and stream level rises      within a river basin.

                        The Connecticut Department of Environmental Protection (DEP) became convinced
                  of the, potential value of an ALERT system in Connecticut, and in 1982 it formed
                  an interagency Committee on Automated          Flood Warning (CAFW). This        committee
                  developed a Master Plan for a, statewide        automated flood warning system known
                  as ASERT (Automated State 'Evaluation        " in Real-time), to    be devel Ioped jointly
                  with local,ALERT systems. The initial phases. of the        ASERT system are currently
                  being installed, along with two     pilot ALERT systems.

                        Within each river basin that is    part of the Connecticut ASERT/ALERT system,
                  a series 'of automated precipitation gages @- and stream - gages collect ifif ormation
                  on rainfall amount and intensity and. amount          and rate of rise    in river levels.
                  This data is telemetered by VHF radio to NWS, State and local receiving            stations
                  equipped with a microcomputer and software for         analyzing, displaying and storing
                  the information. The system has. the capability to combine the rainfall and
                  streamflow data     with a, hydrologic model of      each basiN and to automatically
                  predict ex'pected   'flood levels  and  time .s.'  Informat.i.on on predicted f.lood levels
                  can be compared to maps which           delineate  the  areas   that will be innundated
                  as flood waters reach       different   heights.   Appropriate warnings may then be
                  issued for specific areas   at risk.

                        Although the ASERT/ALERT          system  was  designed   for  application  in river
                  basins, DEP officials began to consider whether this same concept                could be

                                                       1-2

                applied to coastal flood warnings. Unable to identify a similar coastal system
                in operation elsewhere, DEP submitted a proposal to the Federal Emergency
                Management Agency (FEMA),      and in 1985 received a grant to carry out a study
                with two primary objectives:

                (L)  develop specifications for establishing an automated coastal flood monitoring
                     network which is compatible with the statewide ASERT system, and

                (2)  evaluate the    feasibility of establishing a coastal flood warning system
                     utilizing information from the monitoring network.

                L2, METHOW

                     In order to    design the monitoring network and evaluate the feasibility
                of a warning system, it was necessary to evaluate the following:

                (1)  Existing tide, storm surge and wave monitoring systems in use          along the
                     Connecticut shore.

                (2)  Existing NWS forecast and warning procedures for storm surge            and wave
                     heights.
                (3)  The current status of coastal flood warning procedures in Connecticut.

                (4)  Available technology that could be employed to collect flood data and
                     improve existing flood forecasts and warnings.

                (5)  Other potential . uses of information generated by a coastal monitoring
                     network.

                     Costs and benefits of impleme     nting a State operated monitoring network
                     and warning system.

                     Investigation of the se 'and other issues resulted in findings which permitted
                the formulation and evaluation of numerous alternative monitoring networks;
                more detailed design of selected networks,, each with different            capabilities
                and degree of compatibility with the ASERT system; and recommendations for
                providing coastal flood warnings. The major findings are highlighted in this
                summary, and a full discussion is included in the main body of the report.

                                                        1-3

                 Ja FINDINGS

                 1.3.1 Existing Tide, Storm Surge and Wave Measurements

                      Staff, gages which    can be read visually'.are located at many locations
                 along the Connecticut coast, primarily at ports,, marinas and Coast Guard stations.
                 These staff gages do not provide a. continuous or permanent record of actual
                 tide levels.

                      Recording tide gages are   presently operated at five sites along the'Connec-
                 ticut coast.   These gages. record the    actual tide and storm     surge levels on
                 either a continuous basis or at selected  short intervals.

                 (1)  3:hames River estuacy at New London Owned and        operated by  the National
                      Ocean Service (NOS).

                 (2)  Pgquonock River estuaty in Groton Owned and operated by the U.S. Geological
                      Survey (USGS), in cooperation with DEP.

                 (3)  Mouth of the Connecticul River at Old      Saybrook    Owned  and operated by
                      the USGS in cooperation with DEP.

                 (4)  Bridgeport Harbor, Owned and operated by the NOS. The Bridgeport Weather
                      Service Office (WSO) also uses this gage.

                 (5)  Stamford Harbor     Owned by    the U.S. Army Corps of Engineers (COE) and
                      operated by the USGS.

                      Presently, only the NWS recordings from the NOS     gage in Bridgeport Harbor
                 are actually used as input to any storm   surge forecasts and warnings.

                      There are no wave gages permanently operating.along the Connecticut coast.
                 Wave gages have been installed for short periods as part of research projects.

                 1.3.2 NWS Storm Surge and Wave Height Forecast and Warning       Procedures

                      The NWS is. responsible fo  r issuing all coastal storm forecasts and flood
                 warnings. In large part, these forecast s and warnings are based on meteorological
                 and oceanographic data generated by national and regional NWS -data collection
                 systems.   Locally generated data of ten provide only a - minor , input to these
                 forecasts and warnings. The NWS uses four different procedures for preparing

                                                     1-4

               storm surge and wave height forecasts and issuing warnings for the Connecticut
               coast and Long Island Sound,, depending upon the type of weather condition.

               (1)   For hurricanes, surge forecasts and warnings are prepared by the National
                     Hurricane Center WHO in Miami. Hurricane forecasts and warnings are
                     not modified by local NWS offices, although Ahey may be supplemented
                     with local information that is more geographically specific. No separate
                     wave height forecast is prepared.

               (2)   For tropical storms, surge forecasts and warnings are prepared by the
                     NHC, but may be modified by the Weather Service Forecast Office (WSFO)
                     in New York City, if warranted by local conditions, as well as supplemented
                     with more detailed information.      No separate wave height forecast is
                     prepared.

               (3)   For extratropical storms, s -torm surge forecasts are prepared    by the NWS
                     National Meteorological Center (NMC) in Silver Springs, Maryland. The
                     New York WSFO reviews these surge forecasts and modifies them, as appro-
                     priate, based on local observations of actual wind, pressure and storm
                     surge conditions. The New York WSFO also prepares a separate wave height
                     forecast, and issues a coastal marine forecast and warning for Long Island
                     Sound (LIS).

               (4)   Wave height forecasts for non---,torm conditigns are also prepared by the
                     New York WSFO and routinely issued as part of the coastal marine forecast.

               1,3.3 Connecticut Coastal Flogd Warniing Procedures

                     NWS forecasts and warnings for storm surge and wave conditions in LIS
               are disseminated by a combination of NWS, Coast Guard, State agencies, local
               officials, and news media.    NWS warnings are provided directly to the Coast
               Guard, Connecticut Office of Civil Preparedness (OCP), Connecticut State Police
               (CSP), some municipalities, and major news media through official emergency
               communications links of the National Warning System (NAWAS) and NOAA Teletype.
               State officials in turn relay NWS warnings through the State warning network
               directly to all municipalities and to selected news media.

                     NWS forecasts and warnings reach the general public through the          NOAA
               Weather Radio (NWR), Coast Guard marine radio (for mariners) and, most importantly,
               through the 'news media, especially T.V. and radio.       More specific warnings,
               such  as evacuation notices -for residents of vulnerable coastal areas, are
               provided by local officials through such means as sirens, public address systems,
               car-mounted loudspeakers, door-to-door notification, telephone calls, and

                                                        1-5

                 neighborhood associations. In some communities, local cable T.V. and radi            o
                 stations may -issue specific information provided by the municipal civil          pre-
                 paredness off ices.

                 1.3.4 Available and Emerging TechnolQ=_

                 NUMERICAL MODELS         Complex numerical models for-predicting storm surge and
                 wave action have become feasible with the availability of massive data processing
                 capability of modern computers. An NWS model for predicting storm surge during
                 hurricanes and tropical storms, called SLOSH (Sea, Lake and Overland Surge
                 from Hurricanes), recently became operational for LIS. No equivalent models
                 for predicting storm surge during extratropical storms (northeasters), or
                 for predicting wave action, are presently operational for LIS.

                 INSTRUMENTATION. The recent availability of powerful            microprocessors has
                 opened up new possibilities for real-time and near real-time data collection,
                 transmission and processing. The miniature size and low power requirements
                 of these microprocessors permit large amounts of data to be collected almost
                 insta ntaneously at remote locations, including subsea sites.            Sophisticated
                 electronics have also enabled development of water level measurement sensors,
                 such as pressure transducers and acoustic devices, that do not have moving
                 parts and do not require contact with the water surface. Data may be processed
                 at field locations or transmitted via telephone lines, VHF and UHF radio,
                 and satellite for processing at central receiving stations.

                       Unfortunately, many of the recent technological. advances which permit
                 real-time collection and transmission of data are not based on in'dustry-wide,
                 uniform standards. Therefore, not all available systems and instrument components
                 are compatible with one, another.        Efforts have just been initiated at the
                 federal level to establish instrument standards. with which           future federal
                 procurements in this field must 'comply. The present lack of          standardization
                 complicates the design of a coastal flood monitoring network for Connecticut,
                 and the study requirement to design 'a monitoring. network compatible with the
                 existing ASERT system somewhat limits the instrumentation that can be con-
                 sidered and the capabilities of an ASERT compatible system.

                                                    1-6

               PROGRAM& Federal, state and local governments have developed programs which
               utilize the new modeling and instrumentation technology for navigation, weather
               forecasting, flood warnings, research and other purposes. The following federal
               agency programs will have a direct impact on coastal flood data and warnings
               in LIS and along the Connecticut shore:

               (1)  The NWS, FEMA, and COE jointly, in cooperation with coastal states, are
                    using the SLOSH model to estimate storm surge heights for any likely
                    track and intensity of a hurricane along the Atlantic and Gulf coasts.
                    Maps are prepared delineating coastal areas that will be flooded during
                    diff erent hurricanes.

               (2)  The NOS is planning  to upgrade its entire network of permanent tide gages
                    to permit acquisition of real-time tide and storm surge data and to make
                    this data available to NWS and other users.

               (3)  While the new NOS system is being developed and installed, the NWS is
                    temporarily installing new telemetry equipment at selected NOS tide gage
                    sites which will permit near real-time transmission of tide and storm
                    surge elevations to NWS offices responsible for weather forecasts and
                    warnings.

                    The NOS upgrade of its tide gage network is still in a program development
               and testing phase, and lack of a final choice by NOS for the total system
               configuration and instrumentation to be used makes it unclear if a Connecticut
               system will ultimately be entirely compatible with future NOS and NW technology.

                    Other programs developed by federal, state and local governments, often
               in concert with private industry, provide valuable experience for evaluating
               the feasibility of a Connecticut flood monitoring network and warning system.
               The following programs which use real-time data are particularly relevant:

               (1)  New York Harbor Tidal Gage Syste      This system of four automated water
                    level gages in New York Harbor is designed primarily as a navigation
                    aid, but is also used by the NWS to help prepare local forecasts for
                    LIS.

               (2)  Delaware Bay Navigation Projecl      Similar to, but more ambitious than
                    the New York Harbor system, this project incorporates a numerical model
                    of tides and currents in Delaware Bay, and is capable of predicting tide
                    levels and currents up to 12 hours in advance.

                                                                 1-7

                    (3)     West Coast Wave Monitoring kletwork              A-network of offshore wave buoys
                            and nearshore pressure gages along the west coast of the U.S. (and one
                            off the coast of North Carolina) provides data for evaluating *Iongshore
                            sediment transport and coastal erosion. Data is also used by, the NWS
                            to develop wave forecasts and provide real-time wave information in marine
                            weather bulletins. The system, is operated by the Scripps Institute of
                            Oceanography (SIO),, and it would be possible for Connecticut to link
                            up with this network for processing of LIS wave data.

                    1.3.5   Potential Uses    of Data from Monitoring Network.

                            The primary intended     uses of data from a.coastal monitoring network are:

                    (1)     to improve both the     extent and tim.01iness     of  the data base used to prepare
                            coastal storm forecasts and warnings, and

                    (2)     to provide local communities with near -real-time information on actual
                            storm surge and wave heights compared to forecasts.

                            Otherpotential uses were also, identified, including:

                            aid to navigalion       Real-time tide and wave data available during both
                            storm and norr-storm periods could benefit pleasure boaters and commercial
                            shipping interests', particularly harbor pilots.               Accurate, tide data is
                            also useful for dredging projects and hydrographic surveys.

                    (2)     research @ Storm surge and wave data are needed for research on coastal
                            processes within Long Island Sound, including circulation patterns needed
                            for understanding movement of pollutants.
                    (3)     co@stal e     ,ieerin     Empirical data on storm         surge and waves'are also
                            needed to improve the design and- construction of coastal structures,,
                            includi*ng protective structures such as groins, jetties, breakwaters,
                            and seawalls, and others such as             marinas,, docks,     and residential and
                            commercial buildings.

                    1-3.6   Costs 6nd'Benefitn

                    COSTS      Development     of  a coastal   flood monitoring network        will  be more costly
                    than a comparable ASERT/ALERT             system operating within a         river basin. Many
                    coastal network components are            relatively more expensive         because they must
                    be capable of. withstanding the harsh coastal environment.                  In addition, initial
                    installation costs will be greater than           in a riverine Setting,       and maintenance
                    must be performed more frequently and             at  greater costs. Depending upon the
                    final design selected, the coastal network may be able to utilize some existing

               radio repeaters and base station components     of the ASERT system and existing
               recording tide gages, thereby holding down costs. Estimated initial costs
               of a coastal monitoring network range from about $50,000 for a network that
               measures only tides and storm surge and makes maximum use of existing instrumen-
               tation, to over $400,000 for a network that also measures full wave characteristics
               and employs all new instrumentation.

                    The State of Connecticut may be able to reduce significantly its costs
               of installing and operating a coastal monitoring network by entering into
               cooperative agreements' with other agencies such as NWS, NOS,, COE, and USGS
               that have an interest. in the information to be produced by the network. It
               may also be possible to spread the costs among more than one State agency.
               Depending upon the final design. of the network,, the Bureau of Waterways of
               the Department of Transportation (DOT) and the University of Connecticut (UCONN)
               may derive significant benefits from the data, and could be approached for
               sharing the costs of initial network installation and/or operation and main-
               tenance. It may also be feasible to charge user fees for access to data by
               private groups such as harbor pilots, dredging operations, researchers, design
               engineers, etc.

                    The costs of developing a suitable extratropical storm surge model for
               LIS will be substantial. Modification of an existing model and model verification
               can be accomplished for a cost of between $50,000 and $100,000. Development
               of a large set of scenarios to, predetermine areas to be innundated from a
               particular storm may cost an additional $150,000 or more.          Development of
               a suitable numerical wave model may cost about $30,000.

               BENEEITS, Because of the large number of potential users (Table 1.1), benefits
               from a monitoring network andnear real-time dissemination of data will be
               substantia4 though difficult to quantify.

               (1)  Co astal flood warnings can be enhanced, permitting reductions in property
                    losses and unnecessary, evacuations:

                    (a)  The availability of More precise  and timely data from several locations
                          along the coast should enable the NWS to improve the accuracy and
                          timeliness of forecasts and warnings

                                                                   1-9

                                                                                              13IRNRPITS

                             coastal residents and                            Surge and wave height data for design
                             property owners                                  purposes.
                             Municipal agencies                               Actual conditions for storm surge
                                                                              and wave heights

                             Office of Civil Preparedness                     Actual conditions for        storm surge
                                                                              and wave heights

                             DEP, Natural Resources Center                    Data for Inclusion in        its natural
                                                                              resources invEintory

                             DEP, Water. Resources Unit                       Hydrologic studies of        the coastal
                                                                              reaches of river basins; revisions
                                                                              to Flood Insurance Studies

                             DEP, Water    Compliance Vnilt                   Water quality studies of LIS, includinr-
                                                                              currents, movement of pollutants,
                                                                              circulation patterns, etc.

                             DEP, Coastal. Area Management                    Longshore sand transport, - coastal.
                                                                              erosion, evaluation of. coastal structures

                             University of Connecticut    and                 Short- and long-term research -studies
                             educational institutions                         on coastal processes, circulation,
                                                                              currents, etc.

                             National Weather Service                         Storm surge forecasts and present
                                                                              levels; wave height forecasts         and
                                                                              current conditions;. verification
                                                                              of forecast models.

                             Federal Emergency Management Agency              Revisions to Flood Insurance S      tudies;'
                                                                              Hurricane Preparedness Studies

                             Corps of Engineers                               Hurricane Preparedness Studies;
                                                                              dredgi,ng of federally maintained
                                                                              channels; port and harbor studies;
                                                                              other coastal studies

                             National  Ocean   Service                        Short- and long-term sea level variation

                             Coast Guard                                      Sea  surface and weather conditions,
                                                                              tide levels

                             Harbor pilots and marine        Industries'      Accurate tide'' levels for      movement
                                                                              of vessels in and out of harbors

                             Pleasure boaters and marina owners-              Timel information    on wave    conditions

                                                                              Storm   surge and     wave energy and
                             Coastal engineers                                spectral  .'data for  design of coastal
                                                                              structures

                         TABLE 1.1:        User Benef its     from a Real-Time Coastal Monitoring, Network

                                                       1-10

                     (b)   The availability of accurate, real-time data for specific coastal
                           locations should enable community officials to supplement regional
                           NWS forecasts and warnings with more precise local warnings.

                     (c)   The benefits of     improved warnings can be increased still further
                           if the information on storm surge and wave heights is combined with
                           appropriate inundation maps.

                (2)  Navigation improvements:

                     (a)   Commercial shippers    can save money by loading vessels to capacity,
                           reducing waiting time for harbor entry or exit, and avoiding groundings.

                     (b)   Commercial fishermen can locate best fishing areas and avoid groundings.

                     (c)   Pleasure boater and marina operators can make more informed decisions
                           about safe boating conditions and channel depths.

                (3)  Research data:

                     (a)   Surge and  wave data for improved engineering design of coastal struc-
                           tures.

                     (b)   Improved understanding of sand movement and beach erosion.

                     (C)   Tide, surge and wave data for improved understanding of water, quality,
                           including movement of oil spills and other pollutants.

                JA CONCLUSIONS AND RECOMMENDATIONS

                1.4-1 Conelugions

                     The present system of issuing      fi2recasts and warnings for coastal storms
                and f lo oding is less than oDtimal   Although existing warning procedures appear
                adequate to avoid loss of      life and serious injury, improved warnings which
                provide more precise information on the timing, location, and extent of flooding
                would allow further reductions in property losses and avoid some unnecessary
                evacuations. There is room for improvement in most aspects of the total system
                and at every level of government, including:
                     (a)   quantity and quality of data used   in preparing forecasts
                     (b)   timeliness of data 'availability

                     (c)   use.of additional data in  forecast models

                        (d)  use of new and improved models for forecasting storm surge a        nd wave
                             heights

                        (e)  methods of disseminating forecasts and warnings to local communr
                             ities

                        (f)  development of innundation maps     that can be used with flood warnings

                        W    metbods   of 'providing warnings and instructions to residents of coastal
                             f loodplains

                        Although              ents in  'each of these              e certainly possible.,
                  not all are eQual.ly teasible at the  present time, Nor will golential improvements
                  in each area yield egual results in   reduciiiii, flood losses
                        (a)  Only limited improvements appear feasible to the existing NWS forecast
                             and warning system for hurricanes and tropical storms.               Because
                             hurricane warnings are already conservative (i.e. attempt to warn
                             of the most severe likely impact), the limited improvements will
                             probably have little effect on reducing flood losses, especially
                             in Connecticut where the coastal flood zone is relatively small.

                        (b)  More significant improvements     in storm forecasts and flood warnings
                             appear possible for extratropical storms (northeastets).

                        (c)  The most significant improvements should result from supplementing
                             NWS regional forecasts with more precise information for particular
                             geographic areas.

                        The  primary responsibili4 fgr providing       stol:m, storm surge, and
                  forecasts   and 'warnings should remain      with the XWS. Historically, issuance
                  of coastal   storm forecasts 'and Warnings have been the exclusive province of
                  the NWS. Technological advances have         now made It possible for other levels
                  of government and private concerns        to prepare forecasts and issue 'warnings,
                  although they must still rely upon       the  NWS for much of the essential data.
                  This ability makes it attractive to      seek ways of supplementing or replacing
                  NWS procedures that do not take advantage of the latest         technology or do not
                  provide the desired site specific information.. Nevertheless, there are compelling
                  reasons  to continue reliance upon the NWS as      the primary   provider of forecasts
                  and warnings.

                        (a)  The  NWS has a long'. history. of providing reasonably  accu rate forecasts
                             and credible warnings.

                                                     1-12

                    (b)   Current and planned improvements in the programs of NWS and other
                          federal agencies will make possible improvements in NWS forecast
                          capabilities.

                    (c)   It would be very expensive for the State to develop and operate
                          its own coastal storm forecast system.

                    (d)   Even if the State did develop its own forecasting system, the NWS
                          would still issue its own forecasts and warnings.

                    (e)   There is need for consistency of information during emergencies.
                          Conflicting information coming from different sources during emergencies
                          has long been recognized as a major cause of improper response or
                          lack of response by those located in areas at risk.
                    1he   State Can initiate several actions w'hich wi-11 result       i
               foreelLsts and warning,% State activities should
                    (a)   enhance the capabilities of fe  'deral agencies to perform   data collec-
                          tion, forecast and warning responsibilities; and

                    (b)   supplement the federal agencies' regional forecasts and warnings
                          with more detailed information in specific geographic areas regarding
                          the extent and timing of anticipated flooding.

                    To avoid unnecessary expenditures, public confusion over differing messages,
               and conflicts with federal agencies, the State should not:
                    (a)   duplicate federal programs and responsibilities, or
                    (b)   issue information that confliCts with NWS warnings.

               Q1   12evelopment of a coastal flood monitorinLy network for real-time measurement
               of tide and storm surge levela and which would be compatible with the existing
               ASRRT system is feasible and would provide recognizable benefits, both Quantif iahlc
               and ngn-Quantifiable.,
                    (a)   Improved. flood forecasts and warnings.
                    (b)   Improved navigation.
                    (c)   Improved data for design of coastal structures.

                    Collection of wave dat   a, while providing im@Qrtant information for flood
                          and othgr            Id not be completely compatible with the ASERT
               aystem.
                    (a)   Collection of wave data can be made compatible with ASERT, but requires
                          some compromises on the quality of wave data and/or the ASERT system.

                    (b)   A separate wave data network could be established to supplement
                          the ASERT compatible tide/storm surge network.

                                                                1-13

                          (c)   A tide/storm surge/wave network could be 'established that would
                                be completely, independent of ASERT.

                   1.4.2. Recommendations

                   (1)    The Stfite -.q,hould proceed with develoDing a coastal flood monitoring network
                   Important aspects of this network include:
                          (a)   Utilize the    exist .1 ing network of tide ga'
                                                                                ges in LIS, including planned
                                improvements, to the extent possible.

                          (b)   Add new tide, storm surge, and wave measurement stations where needed.

                          (c)   Make data from the State network av             ailable to local communities,
                                the NWS and other users.

                          (d)   Make decisions on which optional network (described in 1.5 below)
                                should be implemented, ba.sed on budgetary and other considerations.

                   (2)    The State should tr         local officials   in the  proper use of the monitoring
                          network,

                          (a)   Use and maintenance      of local  receiving  (base)  stations.

                          (b)   Intrepretation of tide, storm      surge, and wave data from the monitoring
                                network and how to use the data to             supplement NWS forecasts and
                                warnings.

                   (3)    At  the present time,      the State     shotild not devel6p' its own storm 'surL7 a
                   or wave   models for Lang Island Sound          Instead, it should:

                          (a)   Work with   the NHC, FEMA, and the'COE to ensure that the SLOSH model
                                for LIS is used most effectively.

                          (b)   Encourage   the NWS to develop a numerical storm surge model for             extra-
                                tropical storms for LIS.

                          (c)   Encourage   the   NWS   to develop an improved wave forecast model for
                                LIS.

                                                   1-14

               1,5 RECOMMENDED MONITORING NETWORKS

               1.5.1- Number and Locatign of Gagres

                    Empirical data suggest that storm surge along the coast can be adequately
               monitored with five stations:
               (1)  Stonington - New London reach: area of historical uncertainty.
               (2)  Waterford - East Haven reach: constant slope in storm surge.
               (3)  New Haven area: local maximum in storm surge.
               (4)  Milford - Bridgeport reach: low point in storm surge.
               (5)  Stamford - Greenwich reach: area of highest surge.

                    .Wave hindcasting techniques suggest that at least three wave stations
               should be established:
               (1)  Madison - Old Lyme reach:      subject to both easterly swells and local
                    winds.

               (2)  New Haven area: mid-coast; subject to long fetch winds from both east
                    and west.

               (3)  Stamford - Greenwich area: mostly local winds; complex shoreline and
                    offshore bathmetry; subject to long easterly fetch.

               1.5.2. Optional Monitoring Nptwork Degigll&

                    In addition to the number and location of gage stations,, the optional
               designs for a monitoring network reflect consideration of:       type of water
               level and wave sensors; compatibility with ASERT,- utilization of existing
               equipment, programs and procedures; uses of data in addition to. stor m warnings;
               costs of establishing and maintaining the system.

               ASF,RT COMPATIBLE NETWORK

                    Three principle options for an ASERT compatible network are available.

               (A)  Tide and Storm Surge Measurements On4: Use existing recording tide
               gage stations at:

                                                          1-15

                  (1) Stamford Harbor
                  (2) Bridgeport Harbor
                  (3) Mouth of Connecticut River (Old Saybrook)
                  (4),Thames River (New London)

                        Add a new station at:
                  (5) New Haven.Harbor.
                        In addition, two "roving" gages          should be   temporarily (approximately
                  one year) installed at various locations along the coast to provide g        ood corre-
                  lation with the permanent stations. These roving gages could be placed in
                  harbors and other easily accessible locations.

                  (B)   Tide, S torm Surge and Wave Measurements           Use existing    recording tide
                  gage stations at:
                  (1) Bridgeport Harbor
                  (2) Mouth of Connecticut River (Old Saybrook)
                  (3) Thames River (New London)

                        New stations should be added at:

                  (4) Stamford Harbor Breakwater
                  (5) New Haven Harbor Breakwater
                        As with the previous option, two       roving gages    should also. be    installed
                  at various locations along the. coast.        However, . the  roving gages should be
                  installed at Jocations along the open        coast to permit. measurement of wave
                  characteristics. Because installation in     open water locations.is more expensive
                  and wave characteristics are highly variable, these gages . should remain in
                  each location at least two years or until a good set of wave 'data are obt      .ained.

                        Because ASERT/ALERT accepts data on a random or eve          nt reporting basis,
                  in order. to collect wave data and still have the network. be. compatible with
                  the ASERT system                                   lity must be compromised:
                                       wave data or system reliabi
                  (1)   only average wave height and wave length are obtained instead of the
                        usual significant wave heightq significant wave period, and wave spectral
                        data.

                  (2)   Significant wave height, significant -wave period, and wave        spectral data
                        can be obtained, but only processed data can be sent to ASERT      base stations,
                        and the raw wave data (useful for research. and verification purposes)
                        may be losti

                  (3)   Multiple transmissions of wave data are sent     to the base station, increasing
                        the chance of that data getting through, but     crowding the airways.

                                                    1-16

               (C) Separate Storm Surge and Wave Networks To collect uneompromised wave
               data and still utilize the ASERT microcomputer and software (some ASERT software
               modifications will be needed for any of the alternatives considered), a separate
               data transmission system is needed for wave data. Two options exist: a one-
               way communications network (like ASERT), and a two-way communications network
               that would permit changing sampling frequency of wave sensors from the base
               station. If the ASERT transmission system is not used, wave directional data
               could also be included providing a proper wave gage is installed. Another
               option would be to link the wave data transmission system to the Scripps Institute
               of Oceanography (SIO) co   mputer via telephone lines for processing of wave
               data by SIO.

               DATA COLLECTION NFrWQRK INDEPENDENT OF ASFRT If the State decides that ASERT
               compatibility is less important than collecting the full range of wave data,
               a totally independent monitoring network with two-way communications could
               be established that also utilizes a separate computer and specialized software
               for processing wave data.

               COSIS   Costs for the least expensive alternative (ASERT compatible, no wave
               data) would be approximately $50,000 and range upward to more than $400,000
               for the independent network.

               DATA AVAILARTLITV All data will be transmitted by VHF radio to       existing base
               stations at the Northeast    River Forecast Center (NERFC) in Bloomfield and
               the State DEP offices in Hartford. In addition, it is ree    ommended that new
               base stations be established at the Bridgeport WSO and Hartford WSO, and at
               the two State warning points (OCP and CSP) in Hartford. Each local community
               that desires to participate in the system would need    to purchase its own base
               station. Arrangements should be made so that data can also be accessed by
               modem and telephone lines by users who do not need a base station.

                                                         2-1

                             2.0e TIDIE AND TIDAL FLOODING IN LONG ISLAND SOUND

                       In order  to design a coasta I flood monitoring network which will accurately
                 measure storm surge and wave action along the Connecticut shore, it is necessary
                 to understand bow normal, tidal fluctuations. and storm induced flooding occur
                 in Long Island Sound. "This       section  r,eviews available information on tides,
                 storm surge and waves in Long       Island  Sound  and along the Connecticut coast.

                       TIDAL  DATUMP

                       Storm surge, heights of  structures, soundings, and other coastal measurements
                 must have    numerical values above or     below  some reference   base. The logical
                 choice for the base is the ocean surface.          But, since the ocean (and land)
                 surface moves up and down,At must         be 11 ixed" in order to   become a suitable
                 reference base.      The result of mathematically fixing the ocean.surface in
                 terms of an observed tidal phenomenon is called a tidal datum.      (1)

                       Many. tidal datums are in' use and are often confused'by coastal residents
                 and   others.    The 'official tidal datums for the U.S. are established by the
                 NOS   (2). The tidal datums and related   terms most relevant to a flood monitoring
                 network are defined below and illustrated in Figure 2.1.

                 National Tidal Datum     Epoch - The specific 19-year period adopted by the NOS
                 as the official time segment over which tide observations are taken and reduced
                 to obtain mean values for tidal datums. It is necessary for standardization
                 because. of periodic and nonperiodic trends in sea level. The present National
                 Tidal Datum Epoch is 1960 through 1978.

                 Mean *Low Water (MLW) -- The. average. of all the low water heights observed
                 over the National Tidal Datum Epochl.

                 Mean Lower Low Water (MLLW) -- The         average of the lower low water height of
                 each tidal day observed over the National Tidal Datum Epoch. Mean Lower Low

                  IFor stations with shorter series, simultaneous observational comparisons
                 are made with a control tide station       in order to derive the equivalent datum
                 of the National Tidal Datum Epoch. (2)

                                                      2-2

                        MHW
                        MSL                                      Aihhhh
                       WGVD                                       TVVYVYYV
                        MLW
                       HLLW
                             1        5        9        13       17       21        25       29 DAYS

                             MHW    Mean High Water
                             KSL    Mean Sea Level
                             NGVD   National Geodetic Vertical Datum (1929)
                             MLW    Mean Low Water
                             14LLW  Mean Lower Low Water

                     FIGURE.2.1: Relative          Heights of Several Common Tidal Datums
                                       (Semidiurnal Tide)

                                                          2-3

                  Water is the tidal  datum for soundings and depth c    ontours on nautical charts2.
                  Mean High Water (MHW) -- The aver e of all the@high water heights observed
                  over the National Tidal Datum Epoc;y. Mean High Water is the reference base
                  for structure heights, bridge clearances, etc. The shoreline on USGS quadrangle
                  maps is approximately MHW.

                  National Geodetic Vertical Datum (NGVD) of       1929      A fixed reference adopted
                  as a standard geodetic datum for elevations determined by leveling. The datum
                  Was derived for survey from a general adjustment of the first-order leveling
                  nets of both the United States *and Canada. In the adjustment, mean sea level
                  was held fixed as observed at 21 tide stations in the United States and 5
                  in Canada. NGVD (formerly referred to-as Mean Sea Level, and shown as such
                  on older USGS quadrangle maps) is the standard datum of elevations throughout
                  the U.S. Because there are many variables affecting sea 'level, and because
                  the geodetic datum represents a best fit over a broad area, the relationship
                  between the geodetic datum and local mean sea level is not consistent from
                  one location to another in either time or space. For this reason, NGVD should
                  not be confused with mean sea level.

                       All other elevations are referenced to NGVD, which has an elevation              of
                  0.0.  For example, a value- for MHW of 3.0 feet means that MHW is 3.0 feet
                  above NGVD. An increase in relative sea level such that MHW increases 0.4
                  feet from one National Tidal Datum Epoch to another would mean that MHW had
                  risen 0.4 feet with respect to NGVD, and the adjusted value of MHW would be
                  3.4 feet. The elevation of flood levels on coastal flood maps are given as
                  elevation above NGVD.

                  Mean Sea Level (MSQ - The arithmetic mean of hourly heights observed over
                  the National Tidal Datum Epoch. Shorter series are specified in the name;
                  e.g., monthly mean sea level and yearly mean sea level.

                       TIDAL VARIATION I     N LONG ISLAND SOUND

                       Tides in Long Island Sound are semidiurnal with two high tides and              two
                  low  tides occurring each tidal (lunar) -day (5).       A tidal day is the time. of
                  rotation of the earth with respect to the moon, and its mean value is approximately

                  2NOS recently changed,tbe tidal datum for the Atlantic coast from m            ean low
                  water to mean lower low water, which        'is the datum in use on the Pacific and
                  Gulf coasts. Although new nautical charts will have the chart datum lowered
                  from mean low water to mean lower low water, actual sounding figures, isobath
                  and other information will not be changed due to: a), offsetting effects of
                  rising sea level with change from 1941-1@59 datum to 1960-1978 datum; b) thickness
                  of lines on nautical charts and bathymetric maps;- and c) roundoff procedures
                  and accuracies in, datum determinations, hydrographic,- surveying, and nautical
                  charting. (3)

                                                    2-4

               equal to 24.84 hours. (2) Hence, each high tide follows the previous high
               tide by approximately 12 hours and 25 minutes.

                    Because   of the Sound's size and shape,     it amplifies the oceanic tide,
               and the tidal  range in the western Sound is     larger than the tidal range in
               the east.   At Greenwich, for example, the average tidal range is about 7.2
               feet while at  Stonington the range is only about 2.5 feet (6). High and low
               tides also occur at different times throughout the Sound. High tide at Greenwich
               occurs approximently two hours later than high tide at Stonington (7). Figure
               2.2 shows the variation in normal tide ranges at selected points along the
               Connecticut coast.

                    Just as' Long Island Sound affects the timing and amplitude of oceanic
               tides, the bays and estuaries along the Connecticut coast also modify the
               timing and amplitude of local tides within the Sound. Along most of the coast
               these local effects are minor, but become significant in ihe upper tidal reaches
               of the Connecticut and Thames rivers. (7)

               Ll RlPY.ATTVF SFA TYVEL RISE

                    Relative sea level has been rising over the past 15,000 years as the
               earth's climate has warmed, and as the earth has undergone tectonic activity.,
                From tide measurements, the NOS has developed trends in the relative rise
               of yearly mean sea level for the period 1940 through 1980. The average for
               the entire . U.S. coast is 1.3 mm/year. , For the northern east coast the rate
               is considerably higher at 2.6 mm/year (see Figure 2.3).         Figure 2.4 shows
               the increase in yearly mean sea level for the two long-term gages on the north
               shore of Long Island Sound. (1), These stations and other data for northern
               Long Island Sound show relative sea level to have increased about 20-25 cm.
               over the past 100 years (a rate of 2.0-2.5'mm/year). (8)

                    Recent research    (102,103) has found that   relative sea-leVel rise   along
               the  U.S. northeast coast is due not only to      global- increases in sea level,
               (due to thermal expansion of the 'ocean surface and melting of glaciers in
               response to heating of the earth's surface), but also to a large effect from

                                                                                               *.........

                                                                                                      ae            1%

                                  %%

                                        %%

               .00,
                                                  SOURCES: U.S. Army Corps of Engineers. 1980. Tidal Flood Profiles, Ne
                                                           England. Hydraulics and Water Quality Section, New England Divis
                                                           and
                                                           National Ocean Service. 1984. Tide Tables: 1985 High and Low
                                                           Water Predictions, East Coast of North and South america, Incl
                                                           Greenland. NOAA, U.S. Dept. of Commerce.

                                                                                         MEAN

                                                         kMNAL GEODETIC VERTICAL QATUM Or 1929

                                                               MEAj Low wATER

                                        FIGURE    2.2: Tidal Ranges Along the Connecticut Coast

                                                                                      2-6

                                                             7.0-

                                                             6.8-

                                                             6.5-

                                                             L2-

                                                                  ;940            tim               3im               lira               3M
                                                                                                   YM

                                                  SOURCE:         Hicks, Steacy D. 1983. Sea Level Variations
                                                                  for the United States, 1855-1980. National Ocean
                                                                  Service, NOAA, U.S. Dept. of Commerce.

                                    FIGURE 2.3: Mean Sea Level Rise for Northern East Coast

                                          YERRLY MEAN SEA LEVEL                                                 YEARLY MEAN SEA LEVEL
                                            STATION NO. 8516990                                                   STATION NO. 8461490
                                             WILLETS POINT, NY                                                        NEW LONDON, CT

                                    7.7
                                      ISIS* Sin tim tin Ito = I" t= two no                                   SIM I= silo Uin Sim Him 11;w loin Hiv I&
                                                               YEM                                                                   Tw

                                              YEARLY MEAN SEA LEVEL                                        &JI.  YEARLY MEAN        SEA LEVEL
                                               STATION NO. 8518750                                                 STATION NO. 8467150
                                          NEW YORK (THE BATTERY],             NY                                       BRIDGEPORT, CT

                                                                                                           11A.

                                     LI                                                                    LIS

                                     4,3                                                                   4J
                                       fm lifis Him Uis tin tin 4w aim' 'Sim' 'aim                                      d@11' UiS ING Ii2lt 40 1%- -IIiF0 dill
                                                                                                                                      YERR
                                                                          - V-- V@

                                                        w tm@

                                  SOURCE:         Hicks, SteaCy D. 1983. Sea Level Variations for the United States,
                                                   1855-1980. National Ocean Service, NOAA, U.S. Dept. of Commerce.

                           .FIGURE 2.4: YearlyMean Sea Level Recorded at Long Term Tide
                                                          Gages in Long Island Sound

                                                        2-7

                  -isostatic adjustment.   As the North American glaciers melted over the past
                  10-15 thousand years, land previously covered by glaciers has adjusted to
                  removal of the weight of the glacial mass. Land which       was formerly depressed
                  below the glaciers is now rebounding; so relative sea level has been falling.
                  Along the edges of the glacial mass, which includes the Long Island Sound
                  region, land was elevated somewhat, and has been falling, so relative sea
                  level has been rising. Thus, Connecticut relative sea      levels are a combination
                  of global processes and localized response to retreat of.the glacial mass.

                       This relative. rise in sea level is     expected to continue over the next
                  century, and, the rate of increase    is anticipated to increase, but     the future
                  rate of relative sea level rise is uncertain. Recent reports by the Environmental
                  Protection Agency (EPA) in 1984 (9) and   the National Academy of Sciences (NAS)
                  in 1983 (10) examined the effect of atmospheric concentrations of carbon dioxide
                  and trace gases (methane, chlorofluorocarbons, etc.) on relative sea level
                  rise. Increased concentrat  ions  of these gases may act to trap the long-wave
                  radiation re-radiated from the earth's surface, resulting in heating of the
                  atmosphere     commonly known     as the. greenhouse' ef f ect. This heating of the
                  atmosphere in turn would warm the ocean's surface, c       ausing it to expand and
                  produce a relative sea-rlevel rise, and perhaps melt the glaciers (this effect
                  is much more uncertain),

                       Although W cannot -be asserted with any confidence        what  'the effects on
                  sea level will be, there are several estimates of these effects. The NAS antic-
                  ipates a rise in sea-level of 70,cm (2.3 feet) would occur over the next century,
                  given plausible models of atmospheric warming. EPA, provides several estimates
                  of global sea level rise to the year 2100 (Table 2.1).n Under EPA's high scenario,
                  sea level would rise 345 cm (11.3 feet) by 2100.          Under their conservative
                  scenario, sea level would rise 56 cm (1.9 feet) by 2100.         EPA f eels that a
                  global sea level rise between 144 cm (4.8 feet) and 217 em (7 f eet) by the
                  year 2100 is most likely.    By the year 2000, EPA's more likely estimates are
                  that sea level will rise between 8.8 em (0.29 ft) and 13.2 cm (0.43 ft).
                  EPA also estimates that along most of the Atlantic and Gulf coasts of the
                  U.S, the rise will be 18 to 24 em (0.6 to 0.8 feet) more than the global average.
                  The greatest changes will not occur until after, the. turn of the century.
                  All projections are significantly higher than current trends in sea level

                                                        2-9

                                          SCENARIOS OF FUTURE SEA LEVEL-RISE
                                                       (centimeters)

                                                                     Year

                                              2000        2025         2050          2075,       2100
                       Scenario

                       High                   17.1        54.9        116.7.       211.5        345.0

                       Mid-range high         13.2        39.3.        78.9        136.8        216.6

                       Mid-range low           8'.8       26.2         52.6          91.2
                       Low                     4.8        13.0         23.8          38.0        56.2'

                       Current Trends       2.0-3.0      4.5-6.8 7.0-10.5 9.5-14.3            12.0-18.0

                        SOURCE: Hoffman, John S., et. al.    1983. Projecting Future Sea
                                 Level Rise: Methodology,    Estimates to the Year 2100,
                                  and Research Needs. U.S. Environmental Protection Agency.

                          TABLE 2.1: EPA Scenarios of Future Sea Level Rise

                                                      2-9

                rise.

                M TM               SURGE, AND WAVE MEASUREMENT'S IN LONG ISLAND SOUND

                            Waves

                WAVE   CHARACTERISTICS       Waves, created - by wind blowing over the surf ace of
                the water, are the major factor in determining the geometry and composition
                of beaches, and cause most.of the damage in coastal areas, including coastal
                erosion and damage to structures. Waves.are usually defined by their height,
                length, and period (Figure 2.5), which are determined by the fetch (the distance
                the wind blows over the sea in generating'the waves), the wind speed, the
                length of ' time.. the wind blows, and the decay distance (the distance the wave
                travels after leaving the generating area).     Generally, the longer the fetch,
                the stronger the wind; and the longer the wind blows, the larger the waves.

                     Wave" action is    extremely complex.   The   wind simultaneously generates
                waves of many heights, lengths, and periods as it blows over the water. -In
                areas of shallow water, the water depth also affects the size of waves. Waves
                are subject to refraction (bending), depending    on the wavelength in relation
                to water depth; diffraction (energy transfer      along the crest   of the wave);
                and reflection (as they encounter natural and     'manmade barriers. As a wave
                moves toward shore, it reaches a depth of water so shallow that the wave collapses
                or breaks. This depth is equal to about 1.3 times the wave height.

                     Because of bottom friction and wave scattering, there is considerable
                alongshore variability in wave behavior. This variability is obvious to anyone
                who ha s observed waves breaking on the shore. The variability exists in both
                space and time.    The time-variability reflects the development of the storm,
                including the wind speed, wind direction, and location of the storm center
                or front. The spatial variability reflects the dissipation and scattering
                of waves as they travel towards shore.      As an example, the sheltered areas
                behind Fishers Island will experience distinctly different waves than the
                shoreline not in the lee of the island.

                                                         2-10

                                                                          Direction of Wove Travel

                                                        Lz Wove length
                           Wove Crest                             ,,H =Wove Height
                              @--Crest Length                          Wove Trough
                                       Region            Trough Length---@         I @'.lwoter  Level
                                                            Region             d z Depth

                        Ocean Bottom

                       SOURCE:   U.S. Army Coastal Engineering Research Center. 1977. Shore Protection
                                 Manual, Volume I. Corps of Engineers, Dept. of the Army.

                                        FIGURE 2.5: Wave Characteristics
                                           ength
                                                                       W
                                           0n
                                                         Trou gh Length---7

                                                       2-11

                      For modeling and engineering design purposes, the "significant wave height"
                 and "significant wave period" are often used, and may be considered to represent
                 the average height and period of the dominant'waves. More complex measurements
                 of the "energy spectral' and "directional spectra"    of waves take into account
                 the many different types and directions of waves that occur at any particular
                 t im e. Because of their h.ighly technical -nature, no further description, of
                 these. quantative measures of wave characteristics is provided in this report. (11)

                 WAVE MEASUREMEN     TS There are no long-term measurements       of wave character-
                 istics for Long Island Sound. , No wave buoys.or other instruments for measuring
                 wave characteristics have been 'permanently installed in the Sound.           In its
                 1976 study,,(12) of the effects of coastal, storms on the Connecticut coastline,
                 the Corps of Engineers (COE) found that no wave measurements or statistical
                 wave data were available for the area. Limited wave measurements for specific
                 locations and for short durations have been obtained as part of coastal research
                 studies performed at the Universi  ty of Connecticut (13) and the State University
                 of New York at. Stony Brook (14). As input, to its LIS,Marine. Weather Bulletin, the
                 NWS may receive reports from Coast Guard stati    ons and ships concerning observed
                 wave heights (15).

                      The COE (12) has estimated, that the maximum height         of waves breaking
                 at exposed locations along the Connecticut- shor      eline with  tides three feet
                 or more above mean high water ranges from about three to           eight feet, with
                 the possibility of larger waves during very high tides. As part of the recent
                 update of Flood Insurance Studies, FEMA contractors found that for a. storm
                 surge with a.  @return frequency of 100   years, wave heights would range from
                 5.5 to 6.5 feet above the stillwater level, at exposed locations. The maximum
                 wave crest' was determined to be 18.   feet above  NGVD at Greenwich..      Predicted
                 wave heights  were  about one foot higher in    the western portions of   the Sound,
                 than in the east. (16)

                           Tides and Storm Su.

                 STORM SURGE. Storm surge is      defined as the difference between the observed
                 water level and that which would have been expected at the same place in the
                 absence of the storm. Surge height during a particular storm depends primarily

                                                     2-12

               on the following processes, although other factors also exert some influence: (6)

                    (1) Atmospher'               differences. The sea    level surface is elevated
               in response to the low pressures associated with storms. In the open ocean,
               a pressure drop of 33.86 millibars (one inch) will lead theoretically to a
               13 inch rise in sea surface elevation (7).

                    (2)   Wind set=UD. Wind stress on the water surface will cause water
               levels to increase along the fetch in a downwind direction. Wind stress,
               and hence, wind setup are proportional to the square of the wind velocity-
               Wind set-up is also enhanced by decreasing depth. (18)

                    (3) Wave set-Up, Breaking waves create turbulance and actually move
               water nearer shore, resulting in increased height of the water level surface
               in this area. Wave set-up may account for as much as 3.3 to 6.4 feet of storm
               surge height at a beach. (19)
                    (4) Rainfall     Intense rainfall  can lead to an increase of water 'levels,
               especially in estuaries.

                    (5)   Storm motion effects       The intensity of the storm, the speed of
               storm movement, and the angle of the storm track at the shoreline can affect
               storm surge (11,17).

                    (6) Shoreline configuration and basin bathymelly. In general, configurations
               which favor an increase in the, range of astronomical tide will also favor
               an increase of storm surge heights (11).

               .TIDE AND STORM SURGE MEASUREMENTS. As described below, considerably more
               data is available on tide and storm surge levels for LIS than for wave characer-
               istics.

                    Staff Gages, Coast Guard stations and many marinas and port terminals
               have installed tidal staff gages that can be read visually. The COE has installed
               a tide  staff gage in the ports of New London, New       Haven, and Bridgeport, and
               in Stamford Harbor at the Hurricane Barrier. Most        of these gages are located
               on a pier or dock in a protected portion of the          harbor.  Readings are not
               usually taken at regular intervals, and records of       readings are not generally
               maintained. Often, temporary tide staff gages are installed for special projects,
               such as dredging. (20,21,22,23,24,25)

                                                               2-13

                          Recording Gages          Recording tide gages are presently in operation at
                   five locations along the, Connecticut Coast (Figure 2.6):

                   (1)    Thames River estuary at New London Owned and                operated by the National
                          Ocean Service (NOS).-

                   (2)    P uonock River estuary in Groton. Owned and operated by the U.S. Geological
                          Survey (USGS) in cooperation with DEP.

                   (3)    Mouth of tb   e Conaecticut River at Old Saybrook'. Owned and operated by
                          the USGS in cooperation with DEP.

                   (4)    Bridgeport Harbor, Owned and operated by the NOS. The Bridgeport Weather
                          Service Off ice (WSO) also uses this gage.

                   (5)    Stamford Harbor       Owned by the U.S. Army Corps of Engineers (COE) and
                          operated by the USGS.

                          National Ocean Service. The NOS owns               and operates the tide gages at
                   New London and Bridgeport (NOS has an additional recording gage in                 Long Island
                   Sound at Willets Point on the north shore of Long Island (7)). These stations
                   are part of the NOS network of stations,known as NWLON (National Water Level
                   Observation Network), which includes 225 permanent gage stations. The New
                   London station is located at State Pier No. 1 in the Thames River (Figure
                   2.6 (1)). It has been in operation since 1938. The Bridgeport gage is located
                   at Hitchcock Marina in Bridgeport Harbor (Figure                2.6 (4)).   It was originally
                   installed in 1932, but data is not available for the            entire period. (7,26,27,28,29)

                          Figure 2.7 illustrates a typical. NOS station            installation.    Each station
                   inc ludes a primary recording gage. and a reference             staff gage.     The ref erence
                   staff is connected by precise leveling to. nearby bench                   marks.     Generally,
                   the station also includes a backup recording' gage.

                          The' primary gage is an elect ro-m echanic al            Analog-to-Digital Reco      .rder
                   (ADR) (typically a Fisher          Porter or Leupold & Stevens type) which measures
                   water level by means of a float and wire attached to a spring-loaded drive
                   (Figure 2.8).      As the water rises and falls, the drum rotates and turns a
                   shaf t.    A mechanical pin assembly, driven by a timer, converts the analog
                   signal to a digital reading by punching            the elevation into a time sequenced
                   paper tape (Figure 2.9).          Water levels are recorded every six minutes. To

                                                                     N
                                                                                           ------- ....

                                             <
                                     A-,
                                          \px"A.--N@

                                                                                                 5,,, lid

                                  %

                          IIc                                                   Thaman RivAr pnt-Ijary at Now London.   owned and op
                                                                                the National Ocean Service (NOS).
                            5                                              (2)  Poquonock River Pa1*11ary in Grotgn. Owned and operat
                                                                                U.S. Geological Survey (USGS) in cooperation with.DEP.

                                                                           (3)  Mouth of the Connecticut River at Old Saybrook.
                                                                                operated by the USGS in cooperation with DEP.

                                                                           (4)  ArtAgpport HaLbnz. Owned and operated by the NOS. The
                                                                                Weather Service Office (WSO) also uses this gage.

                                                                           (5)  5 t a m f e5 zA-1L&Lb=. Owned by the U.S. Army Corps of
                                                                                (COS) and operated by the USGS.

                                  FIGURE 2.6: Existing Recording Tide Gages in Long Island Sound

                                                             2- 15

                          AN Gage
                         (6 min. sampling Interval)

                                            Observer
                                             (gage-stsff observations daily)     Survey Rod

                                Instrument
                                Shelter

                                                       Pier                      Leveling Instrument
                                                                                (station typically
                                                                                 leveled semiannually)
                                                              Water Line                             Bench
                                                                                                      Mark

                                                  0

                                                      Tide Staff

                                Orifice

                                Float

                               Stilling Well

                       SOURCE:    Deibel, Lawrence E., and Barbara A.' Zumwalt. 1085. Next Generation
                                  Water Level MeaBurement SyStem Program. By the mitre Corporation
                                  for National Ocean Service, NOAA, Dept. of Commerce.

                         @.FIGURE 2.7: Typical NOS Tide                 Station Installation

                                                                                                             2-16

                                                        FIGURE-2.8: Typical Analog-to-Digital Recorder

                                                                                                                                 04, 93  -ater level
                                                                                                                                 04.97
                                                                                                                                 03 -01
                                                                                                                                 .1.07

                                                                                                                                    sprocket drive  holes

                                                                                                                                    clock time

                                                                                                                        -translator o1iinmerif holes

                                                                                                           daily serial number

                                                                   SOURCE:              Coast and Geodetic Survey. 1977. manual
                                                                                        of Tide Observations. Publication 30-1,
                                                                                        U.S. Dept. of Commerce.

                                                  FIGURE             2.9: Recording Tape Showing Time Divisions
                                                                                      and Binary-Coded Digital Punch Out

                                                         2-l' 7

                  reduce wave eff ects on the reading,   the float and wire are mounted in a vertical
                  pipe with a small orifice at the bottom, referred to as a stilling well.
                  Water level heights are recorded with a resolution of 0.001 foot, and an accuracy
                  of about 0.01 foot.

                       An analog recording    pressure gage (bubbler   gage) is often used to provide
                  backup data (Figure 2.10). , These gages rely        on changes in water pressure
                  to indirectly measure the rise and fall      of water level.     Nitrogen is bubbled
                  through an underwater tube, and the pressure,       encountered activates a bellows
                  which in turn moves a pen across a sheet of recording paper mounted on a rotating
                  drum (Figure 2.11). Accuracy ranges from              0.1 foot in low range. areas
                  to +/- 0.5 foot in high range areas.

                       Five times' per week, local     NOS tide observers check      the tide stations
                  and compare the gage readings with visual water readings           on the reference
                  staff.  The observer enters the staff reading into a special log form, and
                  also marks the correct time      directly on the . recording charts. The punched
                  paper tapes, analog recordings, and comparative staff readings are mailed
                  to NOS headquarters at the end of each month by the tide observer. Data are
                  analyzed and recorded by NOS and permanently retained. ,         Anyone may request
                  (purchase) tidal :records for these stations from NOS.           Data are generally
                  not available until at least three months after. it has         been transmitted to
                  NOS headquarters.     NOS annually publishes a set of tide       tables (7) for these
                  and other NOS stations that provide predicted high and low       tides.for the entire
                  year. NOS    also prepares hourly tide level predictions for      the two   permanent
                  stations, which can  be obtained for any month of the    year. (27,3Oi3l)

                       National Weather    Service. The NWS. does not      operate   an
                                                                                       y tide gages of
                  its own in Connecticut. It does, however, obtain data from. the- NOS gage at
                  Bridgeport. The NWS,     has installed   a connection (Bristol    Metameter)- to the
                  NOS ADR gage which transmits tide levels automatically to the Bridgeport WSO
                  by telephone, where they are, recorded on a continuous strip chart. The strip
                  charts are retained only a few months by the Bridgeport WSO, but daily high
                  and low tides and hourly tide levels are manually transferred from the strip
                  chart to printed forms, which are retained   for several years. (32,33,34)

                                                                                  2-18

                                                                                                 R-d.,

                                                                                                                                  C" cylindw

                                                                                                                                 M.-mete,

                                                                                                                  4.4

                                                                                        PIGS tube
                                                                                           Ik

                                             FIGURE 2.10': Typical Bubbler Gage Installation

                                               SOURCE: Bridgeport Weather                    Service office, Stratford, CT.

                                     FIGURE 2.11: Typical Tide                                  Record          from Analog Recorder

                                                        2-19

                       Corps   of Engineers/U.S. Geological Survey. Recording tide. gages are
                 also located   in Stamford Harbor. These gages are owned by the COE for use
                 in conjunction with operation, of the Stamford Hurricane Barrier. The gages
                 are maintained by the USGS as      part of a cooperative agreement. One gage is
                 located outside the hurricane barrier and another inside the barrier to record
                 differences    in tide levels when the barrier is closed.         Both are pressure

                 '
                 gages of the bubbler type, similar to the backup gages used by NOS. USGS
                 records the data at 15 minute intervals on punched paper tape.          .The tape is'
                 collected by USGS personnel approximately every six weeks and processed for
                 inclusion in annual reports of water. records in C          onnecticut.    Unpublished
                 data are available at the USGS office in Hartford.            Records are available
                 since October .1972. The COE records tide levels on a continuous strip -chart
                 within the station house. Charts are stored at the Stamford off ice for . three
                 years. The Stamford, gage is equipped with a Stevens Telemark unit which transmits
                 a coded tide level reading by telephone. The telephone number is unlisted,
                 and is used primarily by the. USGS and the. COE. NOS provides the COE with
                 predictions of hourly tide levels at Stamford Harbor. (25,35,36,37,38,39)

                       The COE   used  to operate tide gages. at Block Island and the Bridgewater
                 Lighthouse at   Old Saybrook in an attempt to correlate tides and.storm surge
                 at those locations    with tides and storm surge at Stamford, and to provide
                 increased warning time for operation of the hurricane barrier.. These gages
                 operated from approximately 1972 - 1977. Tide levels were recorded at three
                 hour intervals and did not record high and Jow tides. The COE found poor
                 correlation with the tide levels at Stamford, and because the gages offered
                 no prediction capability, they were removed. The data have not been retained.
                 (39,40)

                       U.S. Geological Survey/State of Connecticut. Under its cooperative agreement
                 with the   State of Connecticut to collect streamf low, records, the USGS owns
                 and operates two water level gages in tidal locations: at the mouth            of  the
                 Poquonock River in Groton (Figure      2.6 (2)), and in Old Saybrook at the     mouth
                 of the Connecticut River (Figure 2.6 (3)).         Both gages are of the' bubbler
                 type and can record a 35 foot tidal range. In Old Saybrook, the gage      is mounted
                 off the Saybrook Breakwater, and       a digital recorder (punched paper tape) is
                 located in the Coast   Guard's outer lighthouse. In Groton, the gage is mounted

                                                    2-20

               off a pier, and   both a digital and analog recorder are located in a former
               Coast Guard building now owned by the University of Connecticut. Neither
               of these two gages is equipped with a Telemark unit for 'remote transmission
               of data. (36,37,38)

                    Records for the Poquonock River gage are available since January 1973,
               and for the Connecticut River gage since October 1979 (data available from
               June 1976 to February 1978 at a different location 0.6 miles north).@          The
               USGS collects, maintains and publishes data from these two stations in the
               same manner it does for the gage at Stamford Harbor. (35,36)

                    NOS Subordinate Stations,     The long-term records of -the NOS stations
               at New London, Bridgeport and Willets Point serve as reference marks for other
               locations.   At 38 "subordinate" locations along the Connecticut coast (and
               7 on the north shore of Long Island), NOS installed temporary tide gages and
               made simultaneous tide observations at the temporary station and either the
               New London or Bridgeport permanent station (Table 2.2). The approximate time
               and height of tides at each of these locations can be determined by using
               the relationships developed by NOS. Included in' the NOS annual tide tables
               is a tide table that provides the time and height relationship of each subordinate
               stations to a primary station. (4,7,30,41)

               La COASTAL                IN CONNECTIQU

                    Flooding  of coastal areas in Connecticut may result      from both @coastal
               and inland storms. Storms that deposit excessive rainfall over upland watersheds
               may cause rivers and streams, to overflow in lowlying coastal areas. This
               type of flooding may be particularly serious when'the peak flood runoff coincides
               with high tide or storm surge that slows the discharge of floodwaters into
               Long Island Sound, causing additional backup and overflow of floodwaters.
               Lowlying  areas right along the coast may be flooded directly by storm surge
               and wave action.

                                                                                                           2-2    1

                                                                                                              POSITION                             DIFFERENCES                           RANGES,
                                                                                                                                            Time                  Height                                 Mean
                                   NO.                                         PLACE                          Lat.     Long.                                                          Mean Spring        Tide
                                                                                                                                       high        Low      High            Low                         Level
                                                                                                                                       water       water     water       water

                                                                                                                                       h.          h. 0.       ft           ft          ft        it        ft
                                                                                                              N           W,

                                                                               CONNECTICUT, Long Island Sound                               on     NEW LONDON

                                1187       Stonington. Fishers Island Sound                 ........       41     20   71     S4       -0   32     -0 41      *0.1          0.0       2.7         3.2       1.3
                                1189       Noank, Mystic River entrance              ............          41     19   71     59       -0   22     -0 08      -0-.3         0.0       2.3         2.7       1.2
                                1191       West Harbor, Fishers Island, M. T                 .......       41     16   72     00       0    00     -0 06      -0.1          0.0       2.5         3.0       1.2
                                1192       Silver Eel Pond, Fishers Island, k. T                   ...     41     15   72     02       -0   16     -0 04      -0.3          0.0       2.3         2.7       1.1
                                           Thames River
                                1193                                           NEW LONDON, State Pier .............. 41 22 72 06              Daily predictions                       2 6         3 0       1 3
                                1195                                           Smith Cove entrance ................. 41 24 72 06       0    00     +0 10      -0.1          .0.0      2:5         3:0       1:2
                                1197                                           Norwich .............................. 41 31 72 05      +0   13     +0 25      +0.4          0.0       3.0         3@6       I.S
                                1199       Millstone Point                     ..........................  41     18   72     10       +0   09     +0 01      *0.1          0.0       2.7         3.2       1.3
                                           Connecticut River
                                1200                                           Saybrook Jetty ...................... 41 16 72 21       +1   11     +0 45      *0.9          0.0       3.5         4.2       1.7
                                1201                                           Saybrook Point ...................... 41 17 72 21       +1   11     +0 53      *0.6          0.0       3.2         3.8       1.6
                                1202                                           Lyme, highway bridge ................ 41 19 72 21       -1   25     #1 10      +O.S          0.0       '@.I        3.7       1.5
                                1203                                           Essex ............................... 41 21 72 23       *1   39     +1 38      +0.4          0.0       3.0         3.6       1.5
                                           Connecticut River
                                1204                                           Kadlyoe Ill.-- .....        41     11   12     26       *2   19     -1 23      +0*1          0*0       1*7         3*1       1,3
                                1205                                           East Haddam ......................... 41 27 72 2e       +2   42     +2 53      +0.3          0.0       2.9         3.5       1.4
                                1206                                           Haddam 0> .......................... 41 29 72  30       42   48     -3 08      -0.1          0.0       .2.S        3.0       1.2
                                1207                                           Higganum Creek ...................... 41 30 72 33       *2   55     +3 ?S        0.0         0.0       2.6         3.1       1.3
                                1209                                           Portland 0> ........................ 41 34 72  30       +3   51     +4 28      -0.4          0.0       2.2         2.6       1.1
                                1211                                           Rocky Hill 0> .... .................. 41 39 72 38       +4   44     45 44      -0.6          0.0       2.0         r2.4      1.0
                                1213                                           Hartford (7> ........................ 41 46 72 40       #5   30     +6 52      -0.7          0.0       1.9         2.3       1.0

                                                                                                                                            on     BRIDGEPOqT,

                                1214       Westbrook. Duck Island Roads                                    41     16   72     28       0    24     -0 32
                                                                                                                                                   0          :2:7             a      4 11        4 7       2
                                1215       Duck Island                         .................           41     15   72     29       :0   26     - 35        2 3          00:0      4:S         S:2       2:2
                                1217       Madison                             ............                41     16                                                                  4.9         5.6
                                                                               :....................                   72     36       -0   21     -0 30      -2.9          0.0                             2.4
                                1219       F:lkneer Island.                                                41     13   72     39       -00  14     -0 25      -1.4          0.0       5.4         6.2       2.7
                                222   0    S ch a Need                         .........                   41     IS   72     42       -    12     -0 is      -1.4          0.0       5.4         6.2       2.7
                                1221       Money Island                        ............................ 41    15   72     4S       -0   12     -0 23      -1.2          0.0       5.6         6.4       2.8
                                1223       Branford Harbor                     .........................   41     16   72     49       -0   08     -0 is      -0.9          0.0       5.9         6.8       2.9
                                122S       New Haven Harbor entrance              ...............          41     14   72     SS       -0   09     .-0 14     -0.6          0.0       6.2         7.1'      3.1
                                1227       New Maven (city dock)               ...................         41     10   72     55       +0   01     -0 01      -0.8          0.0       6.0         6.9       3.0
                                1229       Milford                                                         41     13   73     003      -00  0      -0 10      -0:2          0:0       6:6         7:6       3:3
                                123   1    Stratford,                          Nou                         41     11   73     7        .    2:     .1 Ol      -1 3          0 0       5 S         6 3       2 7
                                2233       Shelton. Housatonic River              .........                41     19   73     05       +1   3S@    +2 44      -'-a          0.0       S.0         S.8       2.5
                                1235       BRIDGEPORT                          ........................  :::::: 4110   73     11              Da   ily predictions                    6.8         7.7       3.4
                                1237       Black Rock Harbor entrance             ..............           41     09   73     13       -0   04     -0 03      +0.1          0.0       6.9         7.9       3.4
                                2239       Saugatuck River entrance            .......... .....            41     06   73     22       -0   02     +0 01      +0.2          0.0       7.0         8.0       3.S
                                1241       South Norwalk                       .....................: ..... 41    06   73     2S       +0   09     +0 15      40.3          O.'V      7.1         8.2       3.S
                                1243       Gre  en                             ,Led 9e .......... .................. 41 03 73 27       -0   02     -0 01      *0.4          0.6       7.2         8.3       3.6
                                124S       Stamford                            .................................. 41 02 73    33       +0   03     40 08      +0.4          0.0       7.2         8.3       3.6
                                1247       Cos Cob Harbor                      ..........................  41     01   73     36       +0   OS     +0 11      *0.4          0.0       7.2         8.3       3.6
                                1249       Greenwich                           ............................... 41 01   73     37       +0   01     *0 01      +0.6          0.0       7.4         B.S       3.7
                                1251       Great Captain Island                .....................       40     69   73     37       a    00     +0 01      40.S          0.0       7.3         8.4       3.6

                                                                               NEW YORK                                                     on.WILLETS   POINT.
                                                                               Long Island Sound. North Side

                                12S3       Port Chester                        ............................ 42    00   73     40       -0   03     .0 14      40.1          0.0       7.2         B.S       3.6
                                1254       Rye Beach.@                         .............................. 40  58   73     40       -0   22     .0 31      *0.1          0.0       7.2         8.4,      3.6
                                12SS       N:mar n:ck                                                      100    S1   13     41       -0   02
                                                                                                                                                   :0 13      -0:2          0                     1,        6
                                                                                                                                                                            0:00      7:1         1:        3:
                                12S7       k . R:c                                                         4      54   73     47       -    is     0 19       *0 1                    7 2         a6        3 6
                                1259       Davids Island                       ........................... 40     53   73     46       #0   04     -0 09      +0.1          0.0       7.2         6.5       3.6
                                1261       City Island                         ............................. 40   51   73     47       +0   03     -0 Os      40.1          0.0       7.2         9.5       3.6
                                1263       Throgs Neck                         ............................. 40   48   73     48       *0   08     +0 12      -0.1          0.0       7.0         6.2       3.5

                                       SOURCE: National'Oceah Service. 1984. Tide Tables4 1985 High and Low
                                                                               Water Predictions, East Coast of North and South America, Including
                                                                               Greenland. NOAA, U.S. Dept. of Commerce.

                               TABL      E 2.2: National Ocean Survey Subordinate Tide Gage Locations
                                                                               in Long Island Sound, Showing Tidal Differences and
                                                                               Other Constants

                                                    2-22

               2AU        Hurricanea and Tropical Storms (Tropical Cyclones)

                    The   term tropical cyclone applies to atmospheric systems which develop
               in the tropical and subtropical zones and have a counterclockwise rotation
               of winds (in the northern hemisphere), with the lowest barometric pressure
               located at th e center of the vortex. To develop, they      require surface water
               temperatures above about 26 C (79 F), and are maintained by energy from.conden-
               sation of water vapor drawn from the warm ocean surface. Consequently, most
               tropical cyclones- occur in August, September and October (the official tropical
               cyclone season   is from June 1 through November 30). They dissipate quickly
               as they pass over land masses or cold water and are deprived of the warm,
               moist air that supplies energy.

                    Tropical cyclones range in diameter from 50 to more than 500 miles.
               Several categories of tropical cyclones are recognized according to their
               intensity and degree of o rganization:

               (1)  tropical disturbance (little or no rotary circulation at the surface
                    and no strong winds);

               (2)  tropical depression (winds equal to or less than 38 mph);

               (3)  tropical storm (winds of 39 mph or more); and

               (4)  hurricane (winds of 75 mph or more).

                    Tropical storms and hurricanes are of major concern as causes of severe
               coastal flooding.   Hurricanes are further divided into five categories (Saffir/
               Simpson Hurricane Scale) according to their central pressure and maximum sustained
               winds (Table 2.3).

                    In hurricanes, atmospheric pressure and    wind  speed  increase rapidly with
               distance outward from the center, or eye, of the storm (not necessarily the
               geometric center) to a zone of maximum.wind speed which may be anywhere from
               4 to 60 nautical miles from the center. From the zone of maximum wind to
               the edge of the hurricane, pressure continues to increase, but wind speed
               decreases. The atmospheric pressure within the eye (central pressure index)

                                                                 2-23

                                      CATBGORY           CENTRAL PRESSURE                WINDS
                                                         (Inches Mercury)                (mph)

                                          1                    >28.94                    74-95
                                          2              .28.50-28.93                    96-110
                                          3              27.89-28.49                   111-130

                                          4              27.18-27.88                   131-155

                                          5                 <27.17                        >155

                                      TABLE 2.3:     SAFFIREISIMPSON HURRICANE SCALE

                   is the best single index          for estimating the        surge potential' of a @hurricane.
                   Hurricanes may also be characterized by the                 radiu's of maximum winds, which
                   is an index of the size of the storm, and the speed of forward motion of the,
                   storm.

                         The path of an individual storm              is  determined by its. point of origin,
                   and by the relative position and strength                of low and high pressure centers
                   located in the westerly wind belt and over              the Atlantic Ocean. From 1886-1985
                   nine hurricanes (including Hurricane -Gloria in September 1985) have passed
                   over or near Long Island Sound (50 mile, radius of the center of Long Island).
                   The tracks of six selected hurricanes are. shown in Figure 2.12. During this
                   same period, 15 tropical storms have hit the area. The tracks of all hurricanes
                   and tropical 'storms are shown in Figure 2.13.                 Prediction of the path which
                   a pa rticular   hurricane or tropical storm'@will take is very.        imprecise. (11,42,  43)

                         Utilizing statistical data on the motion of tropical              storms in    t.he Atlantic
                   area, Neumann a        .nd Pryslak (44) calculated the expected number of                   tropical
                   storms and hurricanes per 100-year period impacting locations along the U.S. coast-
                   line.    Figure 2.14* shows the grids that encompass the Connecticut coastline.
                   The data in Figure 2.14 show that tropical storm occurrence in Grid 518, which
                   includes. the eastern portion of Long Island --Sound, is greater than in Grid
                   517, which includes the western part              of, the Sound.     Based on actual tropical
                   storm occurrence and movement data, the expected number of tropical storms

                                                       2-24

                       74.                                 70,                er                to-

                                                                                       23 SEPT. 1815
                                                      CAROL!
                                                    11 AUG. 1954                       'IDONNA'
                                                                                    12-13 SEPT. Igoe

                                                                                          NEW

                                                                                      DRUM SWI C`X

                            21 SEPT 1936

                                                                                   14-15 SEPT 1944@

                                                46

                                                                tM A I N E
                                                                                            ...East

                                     LOR4A"
                                  2-7 sepr. i9w&S

                                    V

                      44.

                          bs-
                                         A S  S.

                                                      OF
                                                R. L
                                 1c,   N

                           j                 SOURCE: Adapted from Corps of Engineers, New England
                                                       Division. 1982. Regulations Manual, Stamford
                                                       Hurricane Barrier, Stamford, CT. Corps of
                                                       Engineers, Dept. of the Army.

                     FIGURE 2.12:         Tracks of     Seven Selected Hurricanes             Crossing
                                          or Approaching Long Island Sound

                                                                                      2-25

                                                                                                                            0
                                                                              12

                                                                                                                                                               Is

                         40                                                                 Storm      Starting                  Sto;m     Starting                   40
                                                                                           Track I       Date      Name       Track 0        Date     Name
                                                                                                1      6/1811886      -          12       9/1011938     -
                                                                                                2      8/1411888      -          13       91911944      -
                                                                                                3      9/611888       -          14       10112/1944    -
                                                                                                4      10/8/1888      -          15       8125/1954   Carol
                                                                                                5      8/1511893      -          16       8/7/1955    Diane
                                                                                                6      101111894      -          .17      7/28/1960   Brenda
                                                                                                7      9/2011897      -          18       8/2911960   Donna
                                                                                                8      10/811900      -          19       911211961     -
                                                                                                9                     -          20       8120/1971   Doria
                                                                                               10      6/411934                  21       6/14/1972   A@nes
                                                   1                  22                       11      915/1934       -          22       8/6/1976    Belle
                                                                                                                                 23       9/27/86     Gloria
                         35
                            so                                75                                70                               65                               60

                                   SOURCE: Adapted from Long Island Regional                             Planning- Board. 1984. Hurricane
                                                 Damage Mitigation Plan for the South Shore                            of Nassau and Suffolk
                                                 Counties, New York- Long Island Regional Planning Board,
                                                  Hauppauge, NY.

                                     FIGURE 2.13: -Tropical Storms and Hurricanes Passing
                                                                    Near Long Island Sound

                                                                                                                                              J

                                                             Grid 517                                                                   Grid 518
                                                                                               Massachusetts

                                                   new

                                                       York
                                                                                                                              rh
                                                                                        connecticut                           islanS

                                                    new
                                                                                                                                                       Probability    Probability Of 0.
                                                 jersey                                                                Expected Me.     Expected       Of At Least    At Least Orw
                                                                                                                        of Tropical       Nb. of      On@ Tropical      Hurricane
                                                                                                                        stormalloo      Hurricanoof   Stem Over a        Over A
                                                                        row                            44      Grid       Years         100 Years     10 Year Period '10 Year Period
                                                                                                                             19              7             0.85           0.50

                                                                                                                             31             18             0."            0.00
                                                                                                              F5 -,a I    -                                         I
                                                                                                               Emommum I                                           I

                                                           SOURCE: Neumann, C.J. and M.J. Pryslak.                                1981. Frequency and Motion of
                                                                          Atlantic Tropical Cyclones. NOAA Tecbnical Report NWS 26. National
                                                                          Hurricane Center, Coral Gables, FL..

                                                FIGURE 2.14: Expected Number of Tropical Storms and Hurricanes
                                                                               per 100 Years Impacting the Long Island Sound Region
                                                                                                                                 :C]

                                                           2-27

                  entering Grid 518 per 100 years is     31;  16 of these storms would be hurricanes.'
                  In Grid 517, 19 tropical. storms per        100 years would be expected, of which
                  seven would be hurricanes. The probability that at least one tropical storm
                  will impact the Connecticut coastline       over the next 10 years ranges from 0.85
                  to 0.96.   The probabilities that at least one hurricane will impact this area
                  over the next 10 years are slightly less, ranging from 0.50 to'0.80. (45)

                        Since hurricane winds move -in. a counterclockwise spiral, the winds 'in
                  the right quadrants of this spiral are    more or less parallel with, and reinforced
                  by, the translational (forward) movement of the           storm. . This reinforcement
                  can be of considerable magnitude,         as hurricanes   have travelled at forward
                  speeds of over 50 kn   bts. The Winds to the left of      the storm track are weaker
                  than those to the right, because the winds blow' in directions opposite to
                  the translational movement of the storm. Consequent         ly, winds and 'storm surge
                  are normally at a maximum in. the northeast @ quadrant of hurricanes. (11,42,43)

                        South-facing coasts, like      Connect icut's, that are aligned perpendicular
                  to most storm, tracks, receive       the full impact of -the reinforced      winds. and
                  wave set-up. Howeve    r, Long Island Sound and Connecticut are somewhat protected
                 -by Long Island, which blocks ocean--generated waves from reaching most of the
                  Connecticut coast, and which may cause a hurricane           to weaken as     it passes
                  over the colder land mass.' In general,      fast moving hurricanes have peak storm
                  surges   that are. higher than slower moving storms.         However, slower moving
                  storms  can cause a higher surge in estuarine areas,       such as Long Island Sound,
                  because there is more time for water to     flow into the Sound. (11,45)

                        Figures B.1 and B.2 (Appendix,B)      display data on actual storm surge levels
                  recorded during the 1938 and 1954' hurricanes,      along with  projected storm    surge
                  profiles for 100, 50 and 10-year frequencies (6,46). The        100-year flood   prof ile
                  shows the highest flood level in western Connecticut' (12.2      feet NGVD)9 lowering
                  to 10 feet by Stratford. From        Stratford east the level rises to about 10.7
                  feet at East Haven,   followed by a gradual decrease to about 10.0 feet at Waterford.
                  At New London the level is 10.0 feet NGVD. To. the           east, of New London the
                  fl ood level increases from about 10.0 feet to 10.8 feet   at Stonington.
                        Storm surge is seen to increase dramatically within -the Thames River
                  Estuary.    According to the COE 1980 (12) study, storm surge increased from

                                                    2-28

               9.5 feet to 14.3 feet NGVD at the 100-year level as the distance from the
               mouth of the Thames increased. The 1938 hurricane surge ranged from 9.8 feet
               at New London up to 15.2 feet in Norwich.         Figure 2.15 shows tidal surges
               compared  to the predicted normal tide levels at Stamford Harbor for the 1938,
               1944 and 1954 hurricanes. (47)

               2.51Z     EXtratropical Storms

                    Extratropical storms are weather s    ystems that develop in mid-latitudes
               in the fall, winter and spring (most commonly November through April), in
               response to the interaction of warm and cool air masses along a weather front.
               They occur much more frequently than tropical cyclones, and may be more than
               1000 miles in diameter -- two or    three times the size of a tropical cyclone.
               Extratropicall storms also form a counterclockwise spiral directed toward a
               center of low barometric pressure,  but the maximum winds are of lower velocity
               than tro pical cyclone winds. Some gusts of hurricane velocity may occur with
               extratropical storms.

                    Extratropical storms that occur along the   northern part of the east coast
               of the U.S. accompanied by strong winds blowing from the northeast quadrant
               are called. northeasters.      Northeasters may s  tall off the southeast coast
               of New E ngland and produce high tides that persist for several days. An example
               of this is the storm of October 1955 when high tides continued from 14-16
               October. (11,45,48)

                    A study of northeasters affecting the Atlantic coastal margin of the
               United States during the   period 1921-1962 (48) found that during the 42 year
               period of record, 34 extratropical storm events occurred that resulted in
               water-related damage, i.e., damage due to wave action and tidal flooding.
               The recurrence interval of such storm events is 1.24 years. Stated in another
               way, a storm of this nature has an 81% chance of occurrence in a given year,
               based on the observed data.(45)

                    Wind directions from extratropical storms at a particular area depend
               on the relative position of the storm track      When a storm center passes to

                                                         HURRICANE WE                                                       0
                                                                                                                                                                  ME

                                                                                                                                                           E L. 5.2'

                                                                                                                       POOL -LEV.

                          I                             1    -0,                                                          %L                         I
                                                EL. 3. 3,                                                   Of                                                                                              FAST BRANCH
                                                                                                                                                                                                             POOL ELf
                                                rAsr oRANav
                                                 MCI. ELEV.

                                t--PftEDtcrEa NDE                                                                                                                                                4__,RED1creo rIDE

                                                                                                                WAN SEA LtVft--_
                                                                                                                                                                                 OF

                                                                                                                                                                                 Of

                                    CA      O$rV                                                                    We.                                                                                              CLOSED
                                                                                                                            CLOSED
                    _141A@                                                                  6PK            SPN.           IOPK          1Z TADT          2 A K                 84,M.           OA M,       1z woo"          2
                                                                                                   EASTER       N         8 T A N D A R 0          T I M E

                                    21 SEPTEMBER 1938                                                    14-15 SEPTEMBER 1944                                                                      31 AUGUST          1954

                          NOTEI                                                             NOTE:                                                                            NOTE:

                                 1.* 0 willq ftit. N., .0 &4#ww,  .,..p      Vaek'o                                     Mkv
                                                                             ft-/Y           ra"       Pwd..f'_ bt.t . 0-0 '958                                            C_.'     Mftrd 1. V.-ftt
                                                                                                                                                                                r", 6wo  0".1-          d'
                              I.C.10.1f .1 affaw"   Y.1k.                                 .1h ft."Caft IM                                                                      hftey '01"ta        .? 8"0#.P.F'

                     SOURCE: New England Division. 1982. Regulation Manual, Stamford Hurricane
                                      Barrier, Stamford, Connecticut. U.S. Corps of Engineers, Waltham, MA..

                                FIGURE 2.15: Selected.Storm Surges at Stamfor                                                                        d Harbor,                     Stamford, Connect

                                                   2-30

              the wes  t of Connecticut, winds blow initially from the east or southeast.
              As storm movement progresses, the winds shift to south and then west. This
              type of storm results in onshore winds, leading to increased wave height and
              wind set up. If, on the other hand, the storm center passes to the east of
              Connecticut,  the initial winds will blow from the northeast. Later the winds
              will veer to the north and northwest. This type of storm produces offshore
              winds and a smaller storm surge due to reduced effects of waves and wind set
              up. (45)

                   The effect of northeasters on shoreline       areas often depends on their
              speed of forward movement.      If the storm progresses rapidly, variable wind
              directions over a given fetch length prevent the buildup of large storm waves.
              However, if storm progress is delayed by ridges of high pressure, winds from
              a particular direction have time enough to act on a given wave group, to produce
              waves of maximum height for a specific wind velocity and fetch. Prolonged
              wave action during successive high tides can lead to erosion and damage to
              shoreline development. (45)

                         Mapping of Coastal Floodplains

                    Coastal areas (a*s well  as riverine floodplains) subject to flooding have
              been identified on Flood, Insurance' Rate Maps (FIRMs) prepared by FEMA and
              its contractors. These FIRMs delineate areas with a one percent or greater
              chance of being flooded each year (commonly referred to as the one-percent
              f lood, 100-year flood and base flood). The 1938 hurricane produced flooding
              approximately equal to the one-percent flood over much of the Connecticut
              coastline (see Figure B.1).

                    Coastal floodplains subject to damaging wave action      (waves three feet
              or higher) are designated on FIRMs as V-zones3. Areas         subject to flooding
              from storm surge, but with no wave action or waves less than three feet, are

               3A three-foot high wave was selected for determination of the V-zon      e based
              on data compiled by the COE, which indicated that a three-foot wave was capable
              of causing structural damage. (51)

                                                        2-il

                 designated as A-zones.     (49,50,51) Figure 2.16- shows   a portion of the coastal
                 floodplain in the Town     of Milford as delineated on     a recently adopted FIRM.

                       FIRMs provide a good basis for designating areas subject to floodplain
                 regulations    and flood-related building code     requirements. However, because
                 the different flood zones delineated on FIRMs have not been correlated with
                 particular storm characteristics, these maps cannot be used to acurately estimate
                 which areas will be flooded 'during a developing hurricane or other storm.
                 Nevertheless, they provide the only information presently available on which
                 to base  evacuation notices in coastal areas.

                 2..5A      Flood Dam&=

                       Five hurricanes. (including Gloria in 1985) and several nortbeasters have,
                 caused damaging coastal flooding An         this century. The hurricanes of 1938,,
                 1944 and' 1954 caused the most damage.       Unfortunately, very limited information
                 is avai lable on the dollar  amount of damages caused by these. and other storms,
                 particularly the smaller storms.         In 1976 the COE estimated. that, in 1975
                 dollars, a recurrence of the 1938 hurricane would cost $111,500,000 in losses
                 from tidal flooding, and.a recurrence of the 1954 hurricane would cause losses
                 of $72,0'00,000. (12)   No. updated estimate has been made since that time.
                 However, it is likely that due to increased development along the coast, the
                 losses in 1985 would    be more than double the amount estimated in 1976.@ As
                 an indication of the amount of property at risk, Table 2.4 lists the number
                 of structures located in V-Zones for each of the coastal towns. (52)

                                                                                                                                                       2-32

                                                                                  KEY TO MAP                                             ZONE
                                                        $WVm r lood BooMmy                                                                    B
                                                        lwv- I " B-Am'                                                                                                                            COASTAL BASE FLOOD ELEVATIONS
                                                        I- Dopmloo.- W                                                                                                               1              APPLY ONLY LANDWARD OF THE
                                                                                                                                                                                                    SHJRELINE SHOWN ON THIS MAP.

                                                        IUD Yom F@
                                                        SWV- I lood B-mdv
                                                        0- 1 - I k."- L'oo
                                                        wah ILI--- 1. f I..
                                                        am,           .1.1                        MI. 987)
                                                        Who,,         W.1hi, Imo-                                              @0
                                                        LkIlliom 110  ...... M.&                   RM7X
                                                                                                                               X,
                                                        Rv&.' M'.

                                                        --Rd
                                                                      d 1. 11m Na@ Gtolom, Vo-J 0-1 a 1929                     VL
                                                                                                                               UE
                                                        -EXPLANATION OF ZONE DESIGNATIONS

                                                        IONS                      EXPLANATION
                                                        A             Mo. W 100-, floool; b- 6.4 k-i- -d
                                                                      floml @.d I= .. d.-oml.
                                                        AO            A,m ad 10   *Aom Itodow whom dpft
                                                                      IN,         ww da..       3j..'. _'w dopo.
                                                                                  Om..,         flood I-ool I-                                                                z                                 BAY.
                                                                      _
                                                                      .U-,L
                                                                      k-
                                                        AN            A.. ol 100-1 @AW. II.W.8 oo. OWOo
                                                                      wo tm- om, (I I mul thoo, 13) fni; boo flood
                                                                      ,loudoos me sloo,on, low sm Uwd hmmd I-
                                                                      doe-ioet                                                                            ZONE
                                                        41-AM         A,- of 10&- 11.0; 6mo fi-W Wimn mod                      lkli                           B
                                                                      floool hmad Imlon Uftmomwd.
                                                        AN            A,- W lQOv- floml Im bo   Pm,Mc ed DV Iked
                                                                                  o,olm                  boo Ilmod                                                                 'A
                                                                      do.o.- -d Wool hood I--- moo dm-wol.
                                                        If            Also Imloom fienift of IM IODvm food a" 500-
                                                                      W.. lk*d; . -@ mom, N.. . 2011@vow F-d.
                                                                      N, .10 -qp dopft k. Ihm ow 4 1) k- . h-                                                                              T,
                                                                      tho cW*W.S d,..W mo. I. No lkwo - =
                                                                      ..; . moo   ciallbVisoonfroadmime                                                                              n@
                                                                      boo d-M.Ki
                                                        C             A,- of minimai floodiall. iflohadw4l
                                                        0             Alm of mmilautob". boo Powiloo. flimool lm@omd&
                                                        v             ". .1 100@- comial Good Mo olmAv I.-
                                                                      w1w); boo nwo 'b"Alwo a" now hood fogooi
                                                                      - d.._mmL
                                                        V1420         A... of 100@y- -1ol Flood I* Ikv
                                                                      NmL
                                                                      oldb        0.0 olwd- mod "U..W k.-.d I.-

                                                                                  NOTES TO USER

                                                        m- mo Im om mmm-dmom4amn Amod VI
                                                        mo b. WoMebod bV Road go*UW UPKIMNI6
                                                                                                                               0                 0
                                                        Tbi. NoP I& lot flood I--- Powomo, odr; It dm omi oo,m,
                                                        ..'my doo. A no. subim so flooolog I. doo cowwoMly or
                                                        plawkwok I-um cooh W@W flood bumd w-.                                                 0
                                                        I. mlPows map pmvd@ " "Pameliv Pdowd ftwoo To map
                                                        P..&
                                                        Lom,a " Rood dm4dw Ibino cm Nok mv looloin 0,                                                               P;,
                                                        Co." boo flood W.A1001 Nolft MV 1100.0111 .9 No 0holl-
                                                        foo_ mo Mb
                                                                      dk_

                                                                      INITIAL IDENTIFICATION:                                                                                     Y

                                                                                                                                                                                                                         ONE B
                                                        FLOOD IRAZARD BOUNDARY MAP RAVISIONS:                                                                                                                            ONE B

                                                        FLOOD INSURANCE *AVE MAP EFFECTIVE:                                         L
                                                                                                                                                                                             N'll
                                                                                                IlkV11,901%,                                                                                                                                     00
                                                                                                                                                                                                 J;Nll I
                                                                                                                                                                                          AV(    Nl)!,,@
                                                                                                                                            42
                                                                                                                                                                                           '<@A @@Ci;
                                                                                                                                                          L'r
                                                                                                                                                                r
                                                                      41 I@ I---     _lAA` . 1h. -ooft'.                                                                                                                                                                          Ift
                                                                                                   Flowl lm-
                                                                      IX) 614 "20.

                                                                                                                                    SOURCE:                   National Fl                     ood Insurance Program, Federal
                                                                                                                                                              Emergency Management Agency. 1983.
                                                                                                                                                              Flood Insurance Rate Map (Panel 6),
                                                                      APPROXIMATE SCALE                                                                       City of Milford, Connecticut.

                                                                                  FIGURE 2.16: FEMA Flood Insurance Rate Map for
                                                                                                                                    Section of Milford, Connecticut

                                                   2-33

                                            Residential    Commercial/Industrial          Total

                       .Greenwich                207                   1                   208
                      Stamford                    10                   0                    10
                      Darien                     125                   1                   126
                      Norwalk                    145                   2                   147
                      Westport                   275                   0                   275
                      Fairfield                   98                   i                   100
                      Bridgeport                  24                   3                    27
                      Stratford                  229                   16                  245
                      Milford                    615                   8                   623
                      West Haven                 240                   6                   246
                      New Haven                   50                   1                    51
                      East.Haven                 349                   4                   353
                      Branford                   388                   3                   391
                      Guilford                   174                   0                   174
                      Madison                    270                   5                   275
                      Clinton                     95                   0                    95
                      Westbrook                  126                   0                   126
                      Old Saybrook.              234                   1                   235.
                      Old Lyme                   131                   1                   132
                      East Lyme                     4                  1                      5
                      Waterford                   12                   0                    12
                      New London                  35                   13                   48
                      Groton                      16                   6                    22
                      Stonington                  15                   0                    is

                          TOTAL                 3,867                  74                 3,937

                    SOURCE:. Rummel, Cyn thia J., and G.J. Hudak. 1984-1985. Flood Vulnerability
                             Assessment (for 24 coastal Connecticut municipalities). Natural
                             Resources Center, Department of Environmental Protection,
                             Hartford, CT.

                                TABLE 2.4: Structures Located in V-Zones

                                                      3-1

                                    OOD
                             _0  FT.     FORECASTS AND WARNINGS IN CONNECTICUT

                      The procedures   used by federal, state and local governments to *prepare
                 and disseminate coastal flood forecasts and warnings must be understood in
                 order to evaluate the feasibility of developing an improved flood warning
                 system.

                 11. RIVERINE FLOOD FORECASTS AND-WARNINGS

                      Although a   coastal flood monitoring network and warning -system would
                 not be  comparable in all respects to an automated riverine flood forecasting
                 and warning system, a coastal system would share many similarities. It was
                 the development of an automated riverine flood    warning system for Connecticut
                 that led State officials to consider the possibility of also establishing
                 a compatible. coastal flood monitoring network and warning system. (53)

                 ad.1      National Weather Service ALERT Syste

                      For years the NWS has maintained cooperative flood warning systems in
                 many communities through   out the U.S.    These cooperative systems rely, upon
                 a network of community vol    unteers to make regular observations of rainfall
                 and/or  river levels and to telephone their observations to the appropriate.
                 NWS office, The NWS uses the data gathered by the volunteers, along with
                 its own data on soil moisture conditions and precipitation forecasts, to run
                 a hydrological model of the river basin and predict the time and level of
                 flooding. While very effective in some communities, these programs'have inherent
                 limitations.   Most notably, observers ar     e not always available to collect
                 and report -data on precipitation and      river levels, particularly during@ the
                 night and at remote. locations.

                      In recognition. of these limitiations,  in the late 1970's  the NWS began
                 developing an automated flood warning system. The automated system was designed
                 to take advantage of technological advances that permit real-time collection

                                                    3-2

              and transmittal   of meteorological and hydrological data from. remote locations
              to populated areas with people and property at risk.

                   The resulting system was called ALERT (Automated Local Evaluation in
              Real Time). The ALERT system does not rely upon volunteer observers; it is
              entirely automated. The major components of the ALERT system are: precipi-
              tation gages, river gages, radio transmitters, radio receivers, data encoders
              and decoders, a microcomputer, and specially designed software to process
              the data. Remote rain gages automatically collect data on amounts and rates
              of rainfall and transmit this information via VHF radio to a base station.
              Similarily, stream gage stations transmit. data on the rise in river levels.
              Generally, data collection and transmittal from remote locations is battery
              powered. Because the system is designed for "event reporting" (data transmitted
              only when there is a predetermined amount of rainfall or change in stream
              level), batteries can last a year or more without recharging.

                   .When predetermined critical       precipitation and/or stream level values
              are reached, an alarm is triggered at the base stations and personnel are
              placed -on alert to monitor the situation closely.          Using the rainfall and
              river rise  information, combined with precipitation forecasts and a hydrologic
              model of the stream, NWS personnel are able to accurately forecast floods
              and provide. downstream officials and residents with increased warning time.
              Since the information is also received at a local base station, local officials
              can, if   necessary, initiate flood warnings without, waiting for a forecast
              from the  NWS. . The increase in warning time afforded by the automated system
              is often  sufficient to permit emergency actions which can save lives and greatly
              reduce p roperty losses.

                    ALERT systems were initially used in the western US where sudden rainstorms
              in the remote, upper portions of watersheds can cause flash floods in lower
              portions of the watershed where no rain may have fallen. ALERT systems have
              now been, successfully installed in more than two dozen locations throughout
              the U.S., and many more are now under development. The original ALERT system
              was developed by the NWS, but several private firms have now developed similar
              systems.. ALERT type systems have found wide acceptance on large and remote
              river basins in countries other than the U.S. (54955,56957,58959,60961962)

                                                         3-3

                             Connecticut Automated Flood Warning S@stem
                       In '1982 Connecticut and NWS officials began examining the possibility
                  of a statewide automated flood warning system for small watersheds subject
                  to flash floods. An interagency Committee on Automated Flood Warning (CAFW)
                  was established to oversee development of the statewide system.           Particularly
                  important to CAFW was the technical assistance provided by the NWS and technical
                  and financial assistance from the Soil Conservation Service (SCS).

                       A statewide system was designed in 1983 and called     ASERT (Automated State
                  Evaluation in Real Time). ASERT is in-tended to be operated in cooperation
                  with local communities, and the combined system. is sometimes referred to as
                  ASERVALERT' The initial phase of the A.SERT system is now being installed
                  and consists of 20 automated rain gages, 6 weather stations (including precipi-
                  tation gages)9 6 radio signal repeaters, and 2 base stations. Each base station
                  includes a radio receiver, data. decoder, microcomputer, ALERT software, and
                  an uninterruptable power supply backup. The base stations are located at
                  the Northeast River Forecast Center (NERFC) in Bloomfield and the DEP offices
                  (Water Resources Unit) in Hartford.

                       Concurrently with installation of the ASERT system, community ALERT systems
                  are being installed on a 'pilot basis in the City of         Norwich (Yantic River
                  basin) and the Town of Southington (Quinnipiac River basin).            Each. ALERT
                  system includes an automated river gage and a base station. The City of Stamford
                  has also installed its own ALERT system (63).

                       The initial  ASERVALERT system should be operational in           1986, and the
                  State expects the, system, to be expanded into other river basins as   local commun-
                  ities recognize the benefits of the program. CAFW has prepared         a master plan
                  tha t projects an additional 85 precipitation gages, 24 repeaters, 40 river.
                  gages, and 28 base stations will be added to the system over the next 10 years.
                  This system design may change as CAFW continues its work and experience with
                  the initial installations is obtained. Important aspects of the ASERT system
                  that are still   evolving include procedures for archiving data and providing
                  maintenance.

                                                     3-4

                     The CAFW master plan also includes a coastal component. The purpose
                of this present study is to design the coastal monitoring network and evaluate
                the feasibility of a coastal w*arning system as part of the ASERT/ALERT system.
                Specifications for the ASERT components that may be used by the coastal network
                are provided in Appendix A. (53,64,65,66,67)

                     COASTAL FORECASTS AND WARNINGS FOR CONNECTICUT AND LIS

                     Currently, all official weather forecasts (including storm surge and
                wave heights) and coastal flood warnings for Connecticut and     Long Island Sound
                are provided by the NWS. The procedures used by NWS for preparing these forecasts
                and warnings and then disseminating them to other units of government and
                to the public are described in the following sections.

                          NWS Procedures

                     Different NWS offices are involved with forecasts and warnings. depending
                upon the type of weather   system and flood component involved.
                Forecasts and warnings for coastal Connecticut can be complicated            because
                the Connecticut shorelin  e forms. the border between the areas served by the
                Boston Weather Service Forecast Office (WSFO) and the New York WSFO. (32,68,69,75)

                MARINE WEATHER FORECASTS AND WARNINGS The New York WSFO is responsible for
                marine forecasts and warnings for LIS, to Watch Hill, Rhode Island and Montauk
                Point on.L"ong Island. The Bridge Iport WSO prepares marine bulletins for Fairfield,
                New Haven and Middlesex counties using the New York WSFO forecast supplemented
                with information.on local conditions. The Hartford WSO prepares similar bulletins
                for New London County.      Marine weather bulletins are routinely issued over
                NOAA VHF-FM Weather Radio (162.400 MHz, Meriden; 162.475 MHz, Hartford; and
                162.55 MHz, New London and.New York). These same weather bulletins are transmitted

                1
                 The Boston WSFO    is responsible for forecasts and warnings for the New,England
                area, including all land areas of Connecticut. Wind forecasts by Boston WSFO
                for Connecticut and  by New York WSFO for LIS sometimes differ, requiring consul-
                tation among the New York and Boston WSFOs and the Bridgeport and Hartford
                WSOs. (32,68975)

                                                         3-5

                  over the NWS teletype to selected government agencies and print and broadcast
                  media. -In addition to-NWS teletype and NOAA Weather Rad      io, warnings of severe
                  weather conditions, including flood watches and warnings, are            issued   over
                  the National Warning System (NAWAS).

                       NWS off ices' at Bridgeport, and    New York can be telephoned to receive
                  the latest marine forecast or warning. Every six hours, the Bridgeport WSO
                                                                                   7
                  prepares an.updated tape of marine forecasts and warnings, including a report
                  on local weather conditions -at the Bridgeport WSO.          If the  Bridgeport WSO
                  observes local conditions significantly different from the marine forecast
                  issued by. New York WSFO, it contacts the New York WSFO. The Coast Guard stations
                  at New Haven and New London also broadcast NWS marine forecasts and warnings
                  over its ...radio frequencies, and maintain day and night visual warnings for
                  mariners at several locations along the Connecticut coast. (15v32,68,69970,76)

                  WAVE  HEIGHT    FORECASTS Forecasts of wave heights are developed- by the New
                  York  WSFO, which has forecast responsibility from Watch Hill, RI to Manasquan,
                  NJ, including Long Island Sound west of Watch Hill. These forecasts are made
                  rout*inely every six hours for use in the LIS marine       -forecast. The forecasts
                  of wind waves are prepared using information on present wind speed, wind duration,
                  and fetch length, or,forecast wind speed. According to information supplied
                  by the New York WSFO, it uses at least two sets of wind wave forecast charts,
                  both of which were developed for predicting waves in open seas2. In applying
                  these procedures to wave forecasts in LIS, the meteorologists make adjustments
                  based on their experience. Information on wind speed which Js used in the
                  wave'forecasts is obtained from meteorological instruments along the Connecticut
                  shore. (Bridgeport, New. Haven airport, Groton airport), at several locations
                  on Long Island (La Guardia airport,     Islip airport, Farmingdale airport, Suffolk.
                  airport, Plum* Island, and Montauk Point), and from reports -of ships at sea.
                  The wave height forecasts are intended for mariners and reflect average wave
                  conditions in open coastal waters. They are not intended to indicate breaking
                  wave heights in coastal areas. (20,32,69,74,145)

                  2
                    See Section 4.1.2  and Appendix   B for a discussion of  wave, forecasting/ bind-
                  casting models.

                                                     3-6

               EXTRATROPICAL STORMS Weather forecasts for extratropical storms are prepared
               by the New York WSFO for LIS and by the Boston WSFO for inland Connecticut.
               Both the New York and Boston WSFOs use data and forecast guidance from the
               NWS National Meteorological Center (NMC) in Silver Springs, Maryland. (15,71,72,75)

                    Using an automated statistical model, the NMC prepares storm surge forecasts
               twice daily, projected for a 48-hour period.         This information is provided
               to the regional WSFO, at New York City as guidance (Figure 3.1). The New York
               WSFO may modify the forecast, if needed, based on observations of local conditions
               and using a manual version of the statistical storm surge modeI3. The New
               York WSFO, receives reports of actual storm surge conditions from the Bridgeport
               WSO (every 6 hours) and from four stations in New York Harbor (every 6 minutes),
               which may be used in revising storm surge forecasts. (15,71,73)

                    There is no established procedure for verifying the accuracy of storm
               surge or wave forecasts. There is no instrumentation to record actual wave
               heights and no systematic observations of wave heights are made.(20,32)

               HURRICANES T    he National Hurricane Center (NHC) in Coral Gables, Florida issues
               all forecasts and storm warnings for hurricanes, including storm surge forecasts
               generated, by a numerical model called SLOSH (Sea, Lake and Overland Surges
               from Hurricanes). A separate wave height forecast is not prepared for hurricanes
               since the SLOSH4 model indirectly incorporates waves into its storm surge
               prediction. NWS Regional WSFOs and local WSOs do not modify the NHC forecasts
               and warnings, although they may supplement them with up-to-date reports on
               local conditions, including wave heights, and provide additional warnings
               for  particular geographic areas. Local weather conditions are provided to
               the NHC over a Hurricane Hotline by NWS offices in the affected areas, and
               used by the. NHC is developing its hurricane forecast. (20932,68,69,72)

                3See Section 4.1.1 and Appendix B for a      discussion of the  NWS storm surge
               models for extratropical storms.

                4
                 See Section 4.1 and Appendix,B    for more  complete descriptions of the SLOSH
               model.

                                                              3-7

                              FZUS3 KWBC 021200
                              STORM SURGE FCST FEET INVALID FOR TROPICAL STORMS

                                        12Z     18Z   OOZ 06Z 12Z 157, OOZ '06Z 12Z
                              PwM        0.1    0.4    0.5    0.7    0.7   0.9    0.8    0.9   0.7
                              BOS        0.1    -0.2.  0.3    0.4    0.4,  0.5    0.4    0.6   0.3
                              NWP        0.8    1.0    1.1    1.2    1.2   1.3    1.1    1-1   0-9
                              S FD       1.0    1.1    1.2    1.2    0.9   0.7    0.6    0.1   0.0
                              LGA        1-0    1.0    1.0    1.3    1.2   1.0    1-0    0.8   0.7
                              NYC        1.2    1.3    1.4    1.4    1.3   1.2    1.0    0.9   0.7
                              ACY        0.8    0.9    1.0    0.9    0.9   0.9    0.8    o.8   0.7
                              BWH        1.1    1.1    1.2    1.0    OA    0.9    0.7    0.7   0.6
                              BAL        2-4-   2.5    2.6    2.8    2.8   2.6    2.4    2.0   1.9
                              ORP        0.9    o.8    o.9    o.8    o.8   o.8    0.7    o.6   o.9

                              PWM    Portland,.Maine
                              .BOS   Boston, Massachusetts
                              NWP    Newport, Rhode Island
                              SFD    Stamfordj. Connecticut
                              LGA    Willets Point, New York.,
                              NYC    New York, New York
                              ACY    Atlantic City, New Jersey
                              BWH-   Breakwater Harbor, Delaware
                              BAL.   Bal 'timore, Maryland
                              ORF    Hampton Roads, Virginia

                              (Note:   Forecast time   in 24  hour time.)

                          SOURCE: Pore, N.A.,     et. al. 1974.      Forecasting Extratropical Storm Surges
                                     for the Northeast Coast of the U.S. NOAA Technical Memorandum
                                     NWS.TDL-50. Washington, D.C.

                  FIGURE      3.1:    Sample Storm Surge Forecast Guidance:. Teletype Message
                                      to Weather Service Forecast Offices

                                                        3-8

                     Hurricane forecasts are u     pdated by the NHC every six hours. Forecast
                preparation is initiated at 2 am, 8 am, 2 pm, and 8 pm EDT. When Hurricane
                Watches or Warnings5 are not in effect, Public Advisories based on these forecasts
                are issued at 6 am, Noon, 6 pm, and 10:30 pm EDT6. Once the NHC issues a
                Watch or Warning for a particular area, Public Advisories are issued every
                three hours, and the 6 am, Noon, 6 pm and Midnight EDT advisories are based
                on the new forecasts.

                     Public Advisories include: an updated report on the position and track
                of the hurricane, forecast position, barometric pressure at the center, maximum
                sustained winds, wind,gusts, areas subject to a Hurricane Watch or              Warning,
                the predicted wind speeds and storm surge expected in those areas, and the
                probability of the hurricane reaching landfall at specific locations.            Forecast
                positions are given for 12, 24t 369 48, and 72 hours beyond the time the         forecast
                is made.

                     Beginning with the 1983 hurricane season, the NHC began including in
                the Advisory the probability of the hurricane reaching landfall at specific
                locations.   Probabilities are defined as the chance in percent that the center
                of the storm will pass within approximately 65 miles of a stated location.
                Probabilities are issued in tabular form, as shown in Figure 3.2. (77)

                     As was shown clearly during Hurricane Gloria, the NHC, as well as regional
                and local NWS offices, provide close coordination with local T.V. and radio
                stations serving areas within the projected track of a hurricane.

                TROPICAL    STORMS @-.The RHC also prepares forecasts and warnings for tropical
                storms, and uses the SLOSH model to predict storm surges generated by tropical
                storms. As    with hurricanes, no separate wave height is predicted. The New
                York WSFO may modify.the tropical storm forecast and warning for LIS based

                5A Hurricane Iyatch is  issued for a coastal area when   there is a threat of hurricane
                conditions within 24-36 hours. A Hurricane Warning is issued when hurricane
                conditions are expectd in a specified coastal area in 24'hours or less. (77)

                6
                 Except for the 10:30 pm advisory, the forecast preparation begins four hours
                before the advisory time.       The 10:30 pm advisory is issued earlier in order
                that it may, be available  for the evening television news broadcast. (77)

                             MIATCPAT3                                                                                         ADVISORY NUMBER 48 HURRICANE GLORIA PROBABILITIES
                             TTAA88 XNHC 262136                                                                                  FOR GUIDANCE IN HURRICANE PROTECTION PLANNING
                             BULLETIN                                                                                                 BY GOVERNMENT AND DISASTER OFFICIALS
                             HURRICANE GLORIA ADVISORY NUMBER 48
                             NATIONAL LEATHER SERVICE MIAMI FL                                                               CHANCES OF CENTER OF GLORIA PASSING UITHIN 65 MILES 0
                             6 PM EDT THU SEP 26-1985                                                                        LISTED LOCATIONS THROUGH 2 PM EDT SUN SEP 29 1985

                             UPGRADE GALE WARNINGS TO-HURRICANE WARNINGS   MOM OF CAPE HENRY    TO                                  CHANCESI EXPRESSED IN PER CENT'...TIMES EDT
                             PLYMOUTH MASSACHUSETTS INCLUDING CAPE COD. A HURRICANE WATCH IS    IN                                                     ADDITIONAL PROBABILITIES
                             EFFECT NORTH OF PLYMOUTH THROUGH EASTPORT rAIME.                                                                   2 PM FRI    2 AM SAT    2 PM SAT
                                                                                                                     COASTAL          THRU          THRU       THRU       THRU
                             HURRICANE WARNINGS ARE NOU IN EFFECT FROM LITTLE RIVER INLET To                         LOCATIONS.       2PM F,R 1 2  AM SAT   2 PM SAT    2 PM SUN   2
                             PLYMOUTH MASSACHUSETTS. ALL WARNINGS HAVE BEEN DISCONTINUED SOUTH    OF
                             LITTLE RIVER INLET.                                                                     WILMINGTON NC      31             X          X          X
                                                                                                                     MOREHEAD' CITY MCI 82             X          X          x
                             -GLORIA IS MOVING TOWARDS THE NORTH 20 MPH AND IS EXPECTED TO   CONTINUE                CAPE HATTERAS  MC  ?8             X          X          X
                             NORTHWARD AND ACCELERATE ITS FORWARD MOTION TONIGHT.                                    MORFOLK,VA         66             x        'X           X
                                                                                                                     -OCEAN CITY MD     5a,            I          X          X
                             THE EFFECT OF GLORIA THROUGHOUT THE WARNING AREA CRITICALLY     DEPENDS                 ATLANTIC CITY  NJ  39             4          X          X
                             UPON ITS PRECISE TRACK. IF THE CENTER OF THE HURRICANE REMAINS INLAND                   NEW YORK CITY.MY   23             14         X          x
                             AFTER MOVING OVER EASTERN NORTH CAROLINA ... ONLY GALES WILL se                         MONTAUK POINT MY      6           is         X          X
                             EXPERIENCED NORTHWARD TO NEU ENGLAND. IF GLORIA SKIRTS THE COAST                        PROVIDENCE RI         3           Is         X         @@x
                             ... HURRICANE CONDITIONS WILL BE EXPERIENCED IN THE HURRICANE WARNING                   NANTUCKET MA          1           9          1          X
                             AREA. IF THE CENTER OF THE HURRICANE REMAINS OFFSHORE ALONG THE MID                     HYANNIS MR            1           13         x          x
                             ATLANTIC COAST ... ONLY GALES WOULD BE EXPERIENCED ALONG THAT COAST                     BOSTON MA             2           28         x          x
                             AND A MORE SERIOUS HURRICANE COULD AFFECT-LONG ISLAND AND NEW                           PORTLAND ME           X           20         1          X
                             ENGLAND. HURRICANE FORECASTING SKILLS ARE NOT SUFFICIENT TV PREDICT                     BAR HARBOR ME         x           It         3          x-
                             WHICH OF THESE POSSIBILITIES WILL OCCUR. THEREFORE ... THE COURSE OF                    EASTPORT ME           X           6          5          X
                             LEAST REGRET IS TO EXTEND HURRICANE UARNINGS NORTHWARD TO MASSACHUSETTS.                ST JOHN MB            x           4          4          1
                                                                                                                     MONCTON He            X           2          5          1
                             TIDES OF 8 TO 12 FEET ABOVE NORMAL WILL OCCUR HEAR AND TO THE RIGHT                     YARMOUTH NS           X           3          2          X
                             ,OF WHERE THE CENTER CROSSES THE-.COAST AND RANGE UP TO 6 FEET ABOVE                    HALIFAX MS            x           I          I          X
                             NORMAL ON THE OUTER BANKS. DETA(iLs ON ACTIONS TO BE TAKEN ARE INCLUDED                 SYDNEY NS             X           X          I          I
                             IN STATEMENTS BEING ISSUED BY NATIONAL WEATHER.SERVICS OFFICES AND                      EDDY POINT NS         X           X          I          I
                             LOCAL GOVERNMENT OFFICIALS. EVACUATION FROM OFFSHORE ISLANDS SHOULD                     PTX BASQUES NFLD      X           x          z          3
                             BE HEARING COMPLETION OVER EASTERN 'NORTH CAROLINA.                                     BURGEO MFLD           X           X.         1          2

                             AT 9 PM EDT ... 220OZ ... THE CENTER OF GLORIA WAS HEAR LATITUDE 32.6                           X MEANS LESS  THAN ONE PERCENT
                             NORTH LONGITUDE 76.4 LEST. THIS POSITION IS 198 MILES SOUTH OF
                             CAPE HATTERAS NORTH CAROLINA.

                             A HOAA PLANE REPORTS THE WINDS ARE STILL 13a MPH   AND THE CENTRAL
                             PRESSURE IS 942 MILLIBARS ... 27.82 INCHES.

                             GALE FORCE WINDS EXTEND  208 MILES TO THE  NORTH AND  150 MILES TO THE
                             SOUTH OF THE CENTER.

                             SMALL CRAFT NORTH OF  PLYMOUTH THROUGH MAINE SHOULD  NOT VENTURE FAR
                             FROM PORT.

                             REPEATING THE 6 PM EDT POSITION ... 32.SN...76.4W.

                             THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER
                             AT 9 PM EDT.                                                                                      SOURCE:       Bridgeport Weather Service
                                                                                                                                             Stratford, CT.
                             FRANK

                                              FIGURE 3.2:               Forecast for Hurricane Gloria, Showing.Probabilities
                                                                        of Landfall

                                                        3-10

                on local conditions, and both the New York WSF0 and the Bridgeport and Hartford
                WSOS will supplement the forecast and warning with a report on loca         1 conditions.
                (20,68,69)

                           State of Connecticut Procedures

                     Offices of two Connecticut State agencies, identified as the State Warning
                Points, are responsible for receiving and disseminating emergency warnings.
                The primary State Warning Point is located in th           e Communication Division,
                Connecticut State Police (CSP), in Hartford. This location is manned continuously
                by full-time civilian radio, dispatchers. The alternate State Warning Point
                is located at the Connecticut. Office of Civil Preparedness (OCP) in Hartford.
                This office is manned     during normal work     ing days from 8:00 am to 4:00 pm.
                The OCP handles warning messages during working hours only. After hours,
                the CSP initiate warning activities.

                     Both Connecticut State. Warning Points     receive  their information via NAWAS,
                NWS Teletype, and. NOAA-VHF radio. Upon receipt of a weather watch or warning,
                the State Warning Point activates the state NAWAS and COLLECT (Connecticut
                On7Line Law    Enforcement Communications Teleprocessing) systems to distribute
                the warnings to each regional OCP office and appropriate officials in each
                municipality.  Towns not equipped with either NAWAS or COLLECT systems (Figure
                3.3) must be    reached through the fanout system JFigure 3.4). Connecticut
                State Police Troups located in coastal areas may assist local officials in
                observing flood conditions, alerting residents, and taking -other actions,
                such as blocking flooded roadways. (78,79,80,81,82,83)

                           Municipal Procedures

                     Local cities  and towns receive weather warnings through        the   State  warning
                system, directly  from NOAA Weather Radio, and from T.V. and radio             stations.
                According to local officials, flood warnings are often received from NOAA
                Weather Radio and local media before they are received through the State         Warning
                System.    This may reflect, in part, that coastal flood conditions               develop
                over a period of time and the regular weather forecasts usually provide some

                                                                                  0            0
                                           0
                                                                                   0
                                                                     0
                                                                                  0
                                                                                               0
                                                                                     0
                                                 o5                             0

                                                                                    0

                                                             0 0

                                                                                            ....... . ..
                                                     0   -1,  -10            - -------
                                                     4
                                                                                    A
                                             01                 0                                        01            0
                                                                   0        2   0
                                               0                             0
                                                           0
                                                 0
                                                                                         O'COMMUNITIES WITH THE COLLECT..SYST
                                              0
                                                                                          19 COMMUNITIES WITH THE NAWAS SYSTEM
                                         0
                                                                                            COMMUNITIES WITH BOTH COLLECT AND
                          0                                                              A REGIONAL OR COUNTY FIRE RADIO
                                     SOURCE:   Office of  Civil Preparedness.               OFFICE OF CIVIL PREPAREDNESS REGI
                                               1981.  Emergency Operations Plan.
                                               CT Office of Civil Preparedness,
                                               Hartford, CT.

                             FIGURE 3.3-.      Connecticut Communities with NAWAS and COLLECT Systems

                                                               3-12

                                                                     Warning
                                                                     sources

                                   State Police   ......
                                  (State Warning
                                      Point)                                                    War

                                                                          Network
                                                                 22       Control
                                                                          (Tolland)
                                                               NAWAS                                state
                                                                                                   Aqenci
                                                               Drops         For                         es
                                                             Including       State
                                                                             Fire
                                                                             Radio               r'--
                                                                                                        a::
                                                                                                    pr',v@
                                                                                                   Agnc

                                      Private                                  te
                                                                Local        Sta
                                      Agencies                               Fire
                                                              Fanout         Radio
                                                            169 Towns
                                                                         ILocations

                                                                      ESS
                                                                    WTIC/WDRC   - - - - - - -
                                      CSP                           (AM & FM)
                                    Troops

                                       National                      P lic                         LEGEND
                                       Weather                                          -----After Duty Hours
                                       Service                                          -     24 Bouts
                                                                                        ---Duty Hours Only
                                                                                        *Authorized to initl
                                                                 NNOAA       VHF        statewide xMWAS warning
                                                                 weat"r Radio
                                      Subscribers              (Tolland. Meriden
                                                                   Montvillal

                           SOURCE:    Office  of Civil Preparedness. 1981. Emergency Operations Plano
                                      CT Office of Civil Preparedness, Hartford, CT.

                                   .FIGURE 3.4: Connecticut Warning Flow Chart
                                                                                                 _'C
                                                                                                   (Alte@;..te
                                                                                               Wr.1          t)

                                                           @61                 @te

                                                                      ub

                                                          3-13

                  indication  that a weather watch or warning will be forthcoming well before
                  it is actually issued.

                        Local officials generally do not rely entirely upon official flood warnings.
                  They also make their own observations of storm surge levels, and make decisions
                  based on these observations combined with their knowledge of areas prone,to
                  f looding.   Local observations and decisions are particularly important for
                  winter storms. During hurricanes, as indicated during Hurricane Gloria, NWS
                  warnings may affect local decisions more than local observations of flood
                  conditions.

                        Once a f lood w    arning  is received at the local level and confirmed by
                  observations, officials utilize several methods of notifying local residents
                  of specific actions, such as evacuation, that should be taken. The most common
                  methods of disseminating information locally are: areawide sirens, areawide
                  public address systems, car mounted loud speakers, and door-to-door notification.
                  Some towns also use local beach associations and telephone calls to notify
                  area residents., In some towns the local civil preparedness office establishes
                  direct contact with a local T.V. or radio station. Many local civil preparedness
                  officials also maintain telephone contact with the Bridgeport WSO to ensure
                  that they are informed of the latest conditions and forecasts. (32,78,79,80,81,
                  82,84,85,86,87t88,1699170)

                                                           4-1

                              4.0.- REVIEW OF AVAILABLE TECHNOLOGY AND PROGRAMS

                      This section examines available techniques and programs which may be           applied
                  to develop a    Connecticut coastal flood 'monitoring network and warning          system.

                  Ll       STORM    5URGE AND

                      Theoretical   models can be used. to'@'predict storm surge levels associated
                  with storms. All-theoretical models involve some assumptions and approximation
                  of the actual physics involved in storm surge generation. The simplest models
                  are statistical, and, correlate    observed storm surge with other meteorological
                  or oceanographic phe       rnomena. With the widespread availability of         powerf ul
                  computers in the 19601s, more complex 'numerical models were formulated to
                  predict storm surge. A summary of" applicable statistical 'and numerical storm
                  surge models is provided below, and a fuller discussion is presented. in Appendix
                  B.

                           Storm'Surge   Models

                  STAT15TICAL STORM SURGE STU121ES FOR LIS         There have been three major statistical
                  @tudies of' storm    surges along the coast of Connecticut.          The f irst, in 1973,
                  was published by.   the New England Division       of the COE (89). The COE revised
                  this work in 1980 (6) during a second study        using tide-gage data from stations
                  at  Willets Point,   NY, and Stamford, Bridgeport, New London, and Stonington,
                  Connecticut.     A  major decision in the 1980 study- was to eliminate the 1938
                  hurricane data from the statistical model,' thereby lowering the 100-year flood
                  estimates, particularly in eastern Connecticut (Figure B.1). (46)

                      The most recent study was       perf ormed in   1982 by Dewberry and Davis, Inc,
                  under contract to FEMA        (46)9 and was essentially a review of the 1980          COE
                  study.   The major difference was                 'of the 1938 hurricane data in     their

                                                    4-2

               statistical model f it, particularly in eastern Connecticut where the 1938
               surge was highest. FEMA adopted the 1980 COE surge profiles, except in the
               New London area where they were increased to fit the 1938 hurricane data.
                The resulting profiles (Figure B.2) were used by FEMA in updates to coastal
               flood insuranc e studies.

               NWS STORM SURGE MODF1. FOR EXTRATROPICAL STORMS In the early 1970's, at the
               request of the NWS Eastern Region Headquarters at Garden City, Long Island,
               the NWS Techniques Development Laboratory (TDL) developed an empirical model
               for predicting storm surge during . extratropical storms at 12 locations along
               the U.S. east coast.     Separate regression equations were derived for each
               station by relating observed storm surge at each station to sea level pressure
               at six-bour intervals at selected points along the east coast and. over the
               Atlantic Ocean. Two versions of the model are available: an automated model
               that uses sea level pressure data at several locations directly from a . NMC
               computerized database, and a manual one that can be used       at WSFOs based on
               observed sea level pressure. (15,32p7l973990,69)

                  Stamford, Connecticut is one of the 12 locations for which regression equations
               were developed. Review of observed vs. forecast surges, as provided by the
               NWS (Figure 4.1), indicates that the model consistently over-estimates storm
               surge at  Stamford. The COE, which uses NWS storm surge forecasts as an aid
               in operating the Stamford Hurricane Barrier, reported that predicted surges
               are usually higher than recorded surges.      No systematic records of predicted
               vs. recorded storm surge at Stamford have,been maintained to measure the forecasrt
               accuracy over a long term period. The models have not been recently updated.
               (39t7l,73,75)

               hJUMERICAL STORM SURGE MOD-=To predict, the storm surge associated             with
               a particular storm, statistical storm surge summaries are inadequate, and
               a realistic model of the effects of winds and barometric pressure on the surface
               of the water of a    particular basin is needed. These more realistic numerical
               models are complex and require powerful computers. They generally use as
               input some representation of the storm, including central pressure index,
               wind distribution and speed, storm track and forward speed, and a representation

                                                                                                                 &7
                       4                  3.4                                                 4
                                                                                                       LJ_
                                                                       0 HOUR
                       -2                                              ANA LYSIS              -12

                                          3.4                                                 4

                                                                       06-AND 12-HR
                       -2:                                             FORECASTS              -2

                z

                                          3.4
                       4                                                                      4
                LU                                                                            2[
                       2
                                                                       18-AN'L) 24-HR
                                                                       FORECASTS.

                                          3.4
                       4                                                                      4
                       2                                                                      2
                                                                       30-AN'D 36-HR
                       -2                                              FORECASTS              -2
                       -4

                                                                                              FEN 17. 1972 Is     19      20
                        FEB 2. 1972 3      4                a

                                                                                       SOURCE:   Pore, N.A.F W.S.   Richardson,
               Forecasts  of storm surge based on  sea-level pressure forecasts                  Perrotti. 1974.. Forecasting
               are shown  by dots. Solid curves indicate observed storm surges.                  tropical Storm Surges for the
               Arrows indicate times of astronomical high tide. The date of                      Coast of the United.States.
               each day is placed at the 1200 EST position. Maximum value                        Technical Memorandum NWS TDL-
               of observed surge is placed near peak of each curve.                              Washington, D.C.

                                FI,GURE 4.1: Comparison of Forecast Vs. Observed Storm Surge
                                                   at Stamford, Connecticut

                                                   4-4

              of the basin, including topography and batbmetry.

              NUMRRICAL TIDE AND STORM SURGE MQDELS USED IN LIS Many numerical tide and
              storm   surge  models have been developed for application in different areas
              and to  achieve specific purposes. A few of these models, or portions of larger
              models, have been used in Long Island Sound. However, only the NWS SLOSH
              model is presently operational in a Long Island Sound version. The SLOSH
              model and one additional set of numerical models potentially applicable to
              LIS are briefly reviewed below, and in more detail in Appendix B.

                 NWS SLOSH    Model -- SLOSH (Sea, Lake, and Overland,Surges from Hurricanes)
              is a numerical model developed for real-time forecasting of hurricane storm
              surge along the continental shelves, including large estuaries and. bays.
              It was adapted from an earlier model used by NWS, SPLASH (Special Program
              to List Amplitudes of Surges from Hurricanes), which did not apply to large
              embayments like Long Island Sound. The SLOSH model includes a storm wind model,
              which is fed by several time-dependent meteorological storm variables:

                 (1)  Latitude and longitude of storm positions, at 6-hour intervals, for
                      a 72-hour storm track. This begins 48 hours before the storm's nearest
                      approach, and ends 24 hours after the nearest. approach.

                 (2)  Storm central pressure at 6-hour intervals.

                 W    S torm size (center to region of maximum winds) at 6-hour intervals.

                 Winds are computed independently by, the mode4 and   are not input parameters.
               Only initial still-water elevations at the boundary regions of the model
              are required; actual storm surge levels are not input parameters after the
              model begins running.

                 The  SLOSH model   does not include a tide model within it, because of the
              uncertainty in timing of tropical cyclones with respect to the surface tide,
              and because the SLOSH model is also used in a forecast, or "atlas" mode, where
              the storm surge is simply added to the corresponding tide (see Section 4.4.1).
              (91992,93,94)

                                                          4-5

                      The SLOSH model is being applied to 22 basins, covering most of the Gulf
                  of Mexico and Atlantic coastal areas, as shown in Figure 4.2. The NWS can
                  run the SLOSH model for a basin as the hurricane approaches within-six hours
                  of landf all.  As a hurricane or tropical storm moves up the Atlantic coast,
                  the SLOSH model can be run for successive basins. The computers and data
                  input for ru nning the SLOSH model are located at NWS offices in Silver Springs,
                  but output from the model is routed to the NWS National Hurricane Center WHO
                  at  Coral Gables, Florida.

                      NWS estimates that the SLOSH. model will predict storm surge levels with
                  an error of about +/-20% (e.g.,, an acceptable predicted range of 8-12 feet
                  f or an act ual surge of 10 feet at a specific location). Of Pourse, achieving
                  the 20% accuracy level requires that the input parameters be accurate: the
                  basin must be properly described, initial still-water levels at the boundaries
                  must be accurate, and the storm itself must perform in accordance with forecasts
                  (pressureq track, forward speed, etc.)      The 20% accuracy level has    been verif ied
                  for many coastal locations (including large embayments such as Galveston Bay
                  and Chesapeake Bay), using observed data from historical storms. For real-time
                  applications of SLOSH, achieving a 20% accuracy level.is more difficult, because
                  the storm surge estimates are related to storm track and forward speed, which
                  often vary from forecasts.

                      Two of the SLOSH basins      Narragansett/Buzzards Bays      2), and New York/Long
                  Island Sound 0 3)       cover LIS and coastal Connecticut. The New York/Long
                  Island Sound  SLOSH basin became operational only within the past        year f ollowing
                  input of required bathymetry and topographic data at grid coordinates. The
                  model was first used operationally for the Long Island Sound area in September,
                  1985 for  Hurricane Gloria. Because the storm took a more easterly track than
                  forecast, the predicted storm surge in LIS from Hurricane Gloria was significantly
                  greater than the surge that actually occurred.

                      Although the SLOSH model -is now operational for LIS.and was used in a real-
                  time mode during Hurricane Gloria,'it has not yet been verified using historical
                  storms that crossed over or near LIS. The shallow water in LIS, effect of
                  Long Island on dissipating storms, and other factors peculiar to LIS may adversely
                  affect the accuracy of SLOSH storm surge predictions in LIS. (72,93v95p96097,98)

                                                              4-6

                       lot

                                           SLOSH BASINS

                             1. BOSTON BAY               12. FLORIDA BAY
                             2. NARRAGANSETT/            13. CHARLOTTE HARBOR                                      -4d,
                                 BUZZARDS BAYS           14. TAMPA BAY
                             3. NEW YORK/                15. PENSACOLA  BAY                                       2
                                 LONG ISLAND SOUND       16. '24OBILE BAY
                             4. DELAWARE BAY             17. LAKE PONTCHARTRAIN/                            3
                    4e       5. CHESAPEAKE BAY               NEW ORLEANS                                  4
                             6. PAMLICO SOUND            18. SABINE LAKE
                             7. CHARLESTON HARBOR        19. GALVESTON BAY
                             8. SAVANNAHMILTON HEAD      20. MATAGORDA BAY                               5
                             9. BRUNSWICK                21. CORPUS CHRISTI BAY
                             10. LAKE OKEECHOBEE         22. LAGUNA MADRE
                             11. BISCAYNE BAY

                                                                                                         6

                                                                                                                     re

                                                                                            7

                                                                                          &

                                                                                         9

                   3cr-

                                                    17    16     15     14         10
                                       19
                                    20
                                   21                                  @13
                                   22

                                                                                       12
                                                      se

                      SOURCE: Jelesnianski, C.P,, J. Chen, W.A. Shaffer            and A.J. Gilad. Undated.
                                 SLOSH - A Hurricane Storm Surge Forecast Nodel. Techniques Development
                                 Laboratory, National Weather Service, NQAA, Silver'Spring, MD.

                          FIGURE 4.2: SLOSH Basins Along the Gulf of Mexico and
                                              Atlantic Coastlines

                                                       4-7

                     Spaulding Models          The Spaulding Models are 2-dimensional, vertically
                 integrated finite difference models.        Although primarily tidal models, they
                 could be adapted easily to -include    storm surge effects. The models appeared
                 to work well on tidal time scales important for coastal flooding.

                     Since. storm surge effect's have not been included 'in the models as      applied
                 to  LIS, there was no -wind stress term, and the time history of development
                 of  a wind field could not be included.       In a later application of the model
                 for the North Sea,, wind- stress (or surface stress) was included in the formulation
                 using boundary fitted coordinates.    Any future 'application of the Spaulding-type
                 models must include. a storm model for generating vector wind fields. Costs
                 of converting these models to include storm surge effects, including verification,
                 are estimated at between $50,000 and $100,000. If developed, this model could
                 be applied to extratropica-1 storms.      Preparation of a series of innundation
                 maps based on multiple storm scenarios (similar to procedures used with the
                 SLOSH model),    would probably cost well in excess of $100,000.       (999100,101,174)

                          Wave ForecastinrjHindcasting Models

                     Wa ve forecasting and hindeasting is accomplished by app roximating  the physics
                 of  wave generation and wave transformation using models., In general, wave
                 models can be considered discrete or* parametric, although hybrid models have
                 recently emerged.     The discrete models are complex, and attempt' to directly
                 simulate the wave energy balance or transport equation.           In contrast, with
                 parametric. wave. models' the major features of a wave are derived more simply,
                 and require less computation (often relying upon: nomograpbs). There is cdnsid-
                 erable debate over which.type of model is most appropriate for shallow water
                 conditions, such- as exist in LIS.

                 COE WAVE HINDCAST MODELThe COE has historically used a parametric model
                 as described in the Shore Protection Manual (104). for wave hindcasting.
                 This method is commonly used for generating data on. wave characteristics         for
                 use  in designing coastal protective structures, when empirical wave data is
                 unavailable. More recently, the COE has developed a discrete wave         model for
                 use in shallow water.

                                                   4-8

               FEMA WAVE HEIGHT ESTIMATES The National Academy of Sciences,developeda metho-
               dology for use by FEMA in estimating wave crest elevations associated with
               any frequency storm. This model is used in the preparation of Flood Insurance
               Studies and FIRMs. The method includes means for taking account of varying
               fetch lengths , barriers to wave transmission, and the regeneration of waves
               likely to occur over flooded land areas. It assumes a high correlation between
               wave heights and still-water level for a given frequency still-water level. (171,
               172,173)

               NWS WAVE FORECAST MOnFT-The National Weather Service uses a wind-wave
               forecast for generalized offshore wave conditions.        This wave forecast is
               of the parametric type, based largely on empirical relationships between the
               size of waves generated by specific winds. Three parameters required to use
               these nomographs are wind speed, fetch length, and wind duration. There is
              @no procedure for collecting actual wave height information for comparison
               with wave forecasts. (20,42,69)

                  For the NWS purposes of providing marine forecasts for mariners, genera-
               lized wave forecasts may be adequate. However, since these nomograph techniques
               ignore all details of wave scattering and dissipation, they are not ideal
               for providing coastal flood warnings to coastal residents.

               NUMERICAL WAVE FORECAST MODELS For best results, a numerical wave forecast
               model is required, which includes the full effects of dissipation and scattering.
               Several s.hallow-water, wind-wave models appropriate for providing LIS wave
               forecasts are available. Costs of adapting one of these models to LIS are
               estimated to be on the order of $30,000. (174)

                       INSTRUMENTATION

                  Instruments for automatically measuring and recording water levels in the.
               ocean environment have been in use for over 100 years, and for measuring wave
               characteristics for more than 20 years. A major improvement in recent years
               has been the re placement of mechanical devices that must actually be in contact
               with the water surface with "remote" instruments that need not be in contact

                                                            4-9

                  wi,th the water     surface., Typically, these "remote" instruments are mounted
                  on the bottom of    the ocean. (27)

                     Another major    advance- is the use of microprocessors and other microelectronics
                  to provide rapid    sampling and processing of data at remote locations. These
                  data may be stored (typically on magnetic tape cassettes) 'at the remote site
                  for periodic retrieval, or transmitted to another location            by telephone lines,
                  UHF or @HF radio, or satellite.             Although initial capital and installation
                  costs of this new generation of instruments is usually higher than the older
                  technology, it has generally proved more accurate and reliable,              requires less
                  maintenance, and can be deployed in locations unsuitable for most             of the older
                  generation of instruments.

                     Reliability    and maintenance requirements          are particularly    important for
                  instruments used     to obtain oceanographic data.           'Instruments placed in the
                  ocean must    be' much more durable than those used in rivers          and lakes in order
                  to withstand corrosion, biological fouling, abrasion from. sand scouring, and
                  damage: from. wave forces. The following sections provide an introduction to
                  the principal- types of instruments available for obtaining tide, storm surge,
                  and  wave measurements.

                           Tide  and  Storm Surae Measurpments

                  PRIESURE SENSORS Pressure sensors measure water level' indirectly.              The actual
                  measurement , is,  of  hydraulic 'pressure.   Some sensors also 'measure atmospheric
                  pressure,   and  this  portion of the -total pressure must be removed in order
                  to obtain   an, accurate measurement of water level' (corrective procedures are
                  often  incorporat ed within the sensor). @ Pressure gages do not require a stilling
                  well.   Still-water level is normally determined by rapidly taking many samples
                  over  a fixed time period and -averaging the results. Three types of pressure
                  gages are available to measure tide and storm surge levels: bubbler gages,
                  strain gage pressure sensors and quartz pressure sensors.

                     Bubbler Prave      Bubbler gages, of     the type   now   in use in   LIS by NOS and
                  USGS, use compressed air released through a.           bubble orif ice at the end of a
                  length of tubing     on the ocean floor.. The changing head (water level) above

                                                      4-10

                the bubble orifice causes a corresponding pressure change, which is reflected
                in a manometer, which is usually connected to an           elect ro-m ecbanical chart
                recorder or some type of transmitter. Bubbler gages do not require a stilling
                well, and the bubble orifice can be placed several hundred feet from the compressed
                air source and  recording/transmitting equipment. A typical bubbler gage instal-
                lation is shown in Figure 2.10. (107,108)

                   Strain Lra     pressure sensor;    Strain gage pressure sensors utilize some
                type of variable resistance sensor (e.g. hydraulic, semiconductor, or conductivity)
                in combination with an electrical circuit. As pressure from the water (and
                atmosphere) column changes, resistance changes (voltage varies). Voltage
                ch ange is the actual measurement. Sensitivity of strain, gage pressure sensors
                may vary considerably depending upon the specific type and quality of gage,
                but a typical gage may have a resolution of .1% and an accuracy of .5% of
                the total measurement range (e.g. for a measurement range of 30 feet, a resolution
                of about 1/2. inch and an accuracy of about 2 inches). Strain gage pressure
                sensors are usually highly temperature sensitive, and readings must be temperature
                corrected  (tbermistor often included in gage to permit automatic correction).
                Strain gage pressure sensors may vary in cost from as low as $'200 to about
                $2,000.

                   Quartz @ pressure sensor.-  Quartz pressure sensors utilize a quartz crystal
                with a frequency   of oscillation that is a function of pressure. The frequency
                of oscillation is the measurement method. Quartz pressure sensors are much
                less temperature  sensitive, and have lower power requirements than strain gage
                pressure s ensors. They are also more sensitive and a typical reso          lution is
                .005% with an accuracy of .01% of the total measurement range. Quartz pressure
                sensors cost in the range of $2,000 or slightly more.

                  Tide gages using    either strain gage or quartz     pressure sensors incorporate
                electronics packages that control the sampling rate,   length of sample (integration
                time), and aver aging of samples to filter out the effects of waves. For example,
                to obtain one water level sample, the instrument might average all instantaneous
                water level readings over a 60-second period in order to filter out wave action.
                Most instruments  have variable sampling rates.

                                                      4-11

                    Strain. gage and quartz pressure sensors are housed in a water-tight casing
                 (such as plastic or aluminum), and mounted near the ocean floor. Some units
                 are completely self-contained, and store data on magnetic tape within the
                 gage. Tapes must be periodically retrieved and replaced.         Other gages are
                 connected by underwater cable to data recording and/or transmitting units
                 located in nearby instrument houses.(109,110)       Some typical pressure gages
                 are shown in Fi gure 4.3.

                 ACOUSTIC SENSQ :, Acoustic sensors measure the time it takes for acoustic
                 pulses or "shock waves" to move between the water surface and calibrated reference
                 points. The system described here is one developed by Bartex, Inc. A pulse
                 frequency genera tor/transmit ter/ transponder unit sends acoustic pulses through
                 a small sounding tube which is mounted on a pier or other structure and extends
                 from above the water level into the water to the lowest level to be measured
                 (35 feet maximum range). A reference source is contained within the sounding
                 tube. As the pu  lse travels down the tube, it is reflected first by the reference
                 source and then by the water surface. The transducer converts the reflected
                 acoustic pulses (echos) to electrical pulses. An electronics package measures
                 the return time. for each pulse reflected by the water surface compared to
                 that from the reference source, and the water level is determined. This system
                 has a resolution of .01 foot and an accuracy of about .09 foot over the 35
                 foot maximum range. Measurements may be automatically initiated at intervals
                 of one to 99 minutes, or the unit may be interrograted at any time. Output
                 data is compatible with various telemetry methods. The Bartex gage has been
                 selected by NOS for initial use and testing in its next generation of water
                 level stations (see Section,4.3.1). The Bartex gage, including digital interface,
                 costs approximately $2,600., (109911191129113vll4)     The Bartex acoustic gage
                 is shown in Figure 4.4.

                           IPFUR 01F CAGES Several other types of water level   measurement gages
                 have been developed, including:     float and counterweight (see Section 2.4.2);
                 resistance wave staff; microwave radar; capacitance type probes; and optical
                 devices that read a staff gage floating within a stilling well. (109,110)

                    For various reasons, none of these gages are as well suited to measuring
                 tide and stor m surge levels as the pressure and acoustic gages described above.

                                                 4-12

                              Sierra-Kisco Model 5050LL-PT
                              Liquid Level@Sensor
                              (Sierra-Misco, Inc., Berkeley, CA)

                                           SEA DATA

                                                      Sea Data Model 635-6 Tide Recorder
                                                      (Sea Data Corporation, Newton, MA)

                       InterOcean Model STG 7500 Tide Gauge
                       (shown outside of casing)
                       (Inter0cean Systemst Inc., Safi Diego,tA)

                  F1    E.4.3:    Typical Pressure      Transducer Type.Tide      Recorders

                                                         4-13

                                                                                      A
                                                                                        k

                                      Aquatrak.LG-110 Series Acoustic
                                      Water Level Measurement Instrument
                                      (Bartex, Inc., Annapolis, KD)

                                     FIGURE 4.4: ACOUSUC Type Tide Gage

                                                        .4-14

                         Wave Measurements

                   There   are many ways to measure waves in the ocean, and a vast literature
                on measurement techniques exists. Central requirements are reduced maintenance,
                little drift   in instrument calibration, ease of maintenance or replacement,
                accuracy, reliability, and ease of adaption to this long-term gaging task.
                Different instrumenta   tion may be chosen depending upon whether waves are to
                be measured in deep water offshore, or shallow water nearshore, and               whether
                measure ments are to include wave directional as well as energy characteristics.

                WAVE BUOYS       Wave buoys are commonly used to measure waves (and tides) in
                deep water offshore lo   cations. Typical modern wave buoys are floating spheres
                that follow the movement of the water surface. Contained inside the sphere
                is an accelerometer whichmeasures the vertical             'acceleration of the buoy,
                yielding data on wave height and wave frequency. * Buoys are normally moored
                to the ocean bottom. Buoys may record data on magentic tape for periodic
                retrieval,, or may transmit data by       radio frequency or    satellite. (110)    Figure
                4.5 illustrates typical wave buoys.

                PRESSURE GAGES . Bottom-mounted strain gage and quartz pressure sensors may
                be used to measure wave characteristics as well as tide and storm surge levels
                (see Figure. 4.5).    For measuring wave characteristics, sampling is generally
                based upon "burst,"   rather than continuous sampling. Determination of sampling
                frequency depends upon several factors, including depth of water, and commonly
                ranges from 1-2 Hz (1-0.5 cycle/second). To obtain spectral wave characteristics,
                a fourier' trans  formation is performed on time series data,, commonly based
                on sample sizes in multiples of two. Standard sample sizes, or bursts, are
                1,024,  2,048, etc.    A 1,024 point sample at 1 Hz results in approximately
                17 minutes of data.     Analysis of data yields values for significant wave height,
                significant wave periodp total wave energy, and the fraction of total energy
                within each period, as illustrated in Figure 4.6.

                   Wave gages may be self-contained, with all necessary data processing electronics
                and data storage capability built into the gage. Other options include internal
                data processing, with transmission to a near shore station by underwater cable;
                or data collection only, with all data processing occurring at a shore station

                                                       4-15

                                             MR,

                                                                                                  Ib@.Pq

                      Sea Data Model 635-9
                      Directional Wave Recorder
                      (bottom mounted, shown
                      in mooring tripod)
                      (Sea Data Corporation,
                      Newton, KA)
                                                       NEA Model WBU-1 Wavecrest Wave'Pro-fil ing Buoy
                                                       (NBA (Controls) LTD., Parnborough, England)

                                FIGURE 4.5:. Typical Wave MeaBurement-Gag-es

                                                                                                                                           4-16

                                                                                                 IMPERIAL BEACH ARRAY.EMERGY
                                                                                                 EEC 1965
                                                                                                                                                                             PERCENT ENERGY IN BAND
                                                                                                                                                         (VITAL ENERGY INCLUDES RANCE 2046-4                  SECS)
                                                                                                                 PST SID. HT TOT. EN                                         BAND PERIOD LIMITS (SECS)
                                                                                             DAY'TIME            (CH.)      (CH.80)        22-           22-18               26-16 16-14 14-12 12-10       10-0      G-6       6-4
                                                                                             26                  0901 867   469.6          4.1                               3 742 920.:    9 6            t72.3     5@O       1.3
                                                                                             2                   180  2     401.9          3             *@                  2              1                        , 4
                                                                                                                 140  a                                  .1 . 7              1@13 34' 30.   6'    0                            1*6
                                                                                             2&&                 2001 77 .3 373.8          3.4           0.3                 4.0 38.' 134.3 7'6            6'. :     3.1       1.1

                                                                                             27                  0201 80.3  401*           92.0          0.3                 1.7 .*4   A    21*   .        .2                  0.
                                                                                             27                  080, 71.2  316            .2 .          .                   1.9 26 S37 5   17    It       '7',                I.
                                                                                             27                  1401 59.11 223@3          4@ 7          1 @ 16              3.2 213 38: 8  II'S           0.9       4         2.0
                                                                                             27                  2001 66.3  276.1          3.0           1.0                 3.4 19@ 440.7  20.3           6.4       4.3       1.1
                                                                                             28                  0201 64 1  257            2:4           3 &                 6-7 27 136 6   14.1           4.6       3.1       2.2
                                                                                             28                  090, 71@ 9 323: *'        3             33'6                11.2 42'6 20@2 10.9           4.1       2.9       1.7
                                                                                             28                  1401 76.2  362.5          3.3           2*2                 12.5 21:2 39.5 14.4           2.2       3.2       1.6
                                                                                             28                  200105.0   431.9          2.3           4.3                 7.8 22.7 40.3  13.8           2.6       2.9       1.6

                                                                                             29                  0201 7&. a 367.1          4.2           1.5                 9.0 33.7 30.3  13.9           3.7       Z 9       1.2
                                                                                             29                  0001 72. 6 329.0          5.6           1.0                 5.9 26.5 41.2  13.1           3.4       2         1.4
                                                                                             29                  140172.3   326.6          5             -51.0               7.I13     0    1              3.7       1: :      1.1
                                                                                                                                                                             4'  1          9* 6           *                   0
                                                                                             VW                  2001 643. 42". a          4.1           1.1                 16. T14.1 38.7 16.3           .0        2.4       .6
                                                                                             30                  0201 63.7  233.9          A. 1          7.2                 14.9 6.7 33.6  19.9           6.2       2,0       1-0
                                                                                             30                  0901 78.7  387.3          6 0           13.6                4.7 11.5 26,2  24.3           9.7       2.9       1.
                                                                                                                 1                         7                                           0                   1         2
                                                                                             30                  140 80.1   400.           10            13.7                14.2 6: 614    29.4           1.3       2.7       3 20
                                                                                             30                  2029 91.7  529. 'F        3.6           7.3                 33.7to1   9: 3 12,9           IZ 3      7.        4'
                                                                                             31                  020, "@ 06 1: 1,          2             5.1                 .:7 10.3 14.1  12.2           8.0       7.4       5.9
                                                                                             31                  0801113    797 6          4::           ,-0                 28 614 619.0   9.3            10.1      6- 1      3:1
                                                                                             3                   140 93.8   549.8          5.1           3.7                 23 .019@ a12.7 9.6            9.3       7         6 5

                                                                                             IMPERIAL BEACH ARRAY.ENERGV
                                                                                                 DEC             1905

                                                                                                                      PERSISTENCE
                                                                                                                 CONSECUTIVE DAYS (I OR "ME) SIGNIFICANT
                                                                                                                 WAVE HEIGHT               is -*- METERS OR LEBO

                                                                                                                 METERS                    DAVS
                                                                                                                 0.5                       1.
                                                                                                                 1.0
                                                                                                                 1.3                       1: 13: '0.    37:
                                                                                                                 2-0                       2, 29.
                                                                                                                 2'S                       31.
                                                                                                                 3.0                       31
                                                                                                                 .*.                       31:
                                                                                                                 4 0                       31,
                                                                                                                 4@ 3                      31;
                                                                                                                 5.0                       31
                                                                                                                 5'.                       3':
                                                                                                                 4.0                       31,

                                                                                             MAXIMUM             DAILY SIGNIFICANT WAVE HEIGHT FOR                           DEC 1903

                                                                                             D^ft I              VKC)       1              2             3                   63        6          7

                                                                                             810. "T             (M.  1.6                  0.8           2.4 1.6             1.6 1.7        1.5

                                                                                             DATE                I DEC)     9              9             10                  it 12     12         14

                                                                                             SIG. "T (Ff.)            1.8                  1.7           1.4 0.9             1.2 1.5        1. 2

                                                                                             DATE                DEC)       is             16            17                  is 19     20         22

                                                                                             519.KT              (M. 10.9                  0.5           0.6 0.0             0.9 0.4        O@ 7

                                                                                             DATE, t DEC)                   22             23            24                  23 26     27         20

                                                                                             910. HT (M.              1.0                  1.1           1.6 1.0             0.9 0.0        0.9

                                                                                             DATE                DEC)       29             30            31

                                                                                             SIC. my tn. )            0.0                  0.9           1. 1

                                                                SOURCE: U.S. Army Corps of Engineers, and                                                                              California Department
                                                                                        of Boating and Waterways. 1986.                                                                Coastal Data Information
                                                                                        Program, Monthly Report, December                                                              1985. Monthly Summary
                                                                                         Repor                   t No. 119.

                                                                      FIGURE 4.6: Sample Analysis of Wave Parameters

                                                       4-17

                 (data transmission by underwater cable). (110)

                    Several pressure gages may be arranged in an array         to obtain directional
                 wave data. Directional wave recorders are also available' that measure wave
                 direction by means of an electromagnetic flow sensor. (110,115)

                          Meteorological Instruments

                    An enormous variety of meteorological instruments is available for automatically
                 sampling a wide range of meteorological conditions. Meteorological parameters
                 most applicable to a coastal flood monitoring network and warning system are
                 wind speed and direction and barometric pressure. No review of the different
                 types of instruments available is provided in this report.

                          Data Tran            id Processing

                    Microprocessor  technology has greatly increased the speed of data processing
                 and has made real-time data collection,. transmission, and processing practicable.
                 With the availability of microcomputers in the early 19801s, this real-time

                             is now av
                 capability i            ailable to small scale users at a reasonable cost.        In
                 the simplist terms, this technology involves iransformation 'of. raw date into
                 a digital format for processing *and transmission; transmission by telephone
                 lines, radio frequency, or satellite; and transformation of processed data
                 into appropriate statistical data, engineering terms, graphics, or other appro-
                 priate forms.   Unfortunately, there is a great lack of standarization in the
                 technology- by which data are collected, transmitted and processed. Consequently,
                 specific applications such as a Connecticut flood monitoring network generally
                 cannot be deployed simply by assembling individual components from different
                 vendors. Almost. inevitably, some off-the-shelf components will not be fully
                 compatible with others,- requiring that some  hardware and/or software components
                 be customized.

                    As an example, the Connecticut ASERT system is not compatible with some
                 other real-time meteorological, hydrologic and oceanographic systems, particularly
                 some wave measurement systems. One limitation'ls that ASERT is a one-way
                 communications system; it transmits data only from the remote field- stations

                                                    4-18

               to a   base station. The field units may not be queried (interrogated) from
               the base station (with ASERT the user may interrogate the base station unit
               for data stored in the computer memory). By contrast, some storm surge and
               wave measurement systems are based on: two-way communications,. A user, at the
               base station may directly interrogate the field station to obtain the most
               recent measurements.     If the sensor and related electronics package permit,
               the user may also reprogram the sensor to change sampling rate or perform
               other modifications. Two-way communications systems are more expensive than
               a one-way communications system. A two-way system would not be compatible
               with the radio repeater stations used with ASERT.

                  ASERT is also an event reporting system: field stations transmit rainfall
               and streamflow data at random times whenever a sample differs from the previous
               sample by a predetermined amount (meteorological measurements are transmitted
               on a timed basis).    Because transmission time of a single piece of data is
               brief less than .25 second) very few individual transmissions will be lost
               due to interference.    Lost data units (such as may occur, during an intense
               rain storm) are not critical to overall data quality since all data is transmitted
               in equal units (e.g. 1.0 mm of rainfall), and the data coding and software
               permit all data transmissions to be accumulated even if individual units are
               lost. Wave data are normally transmitted on a timed basis to avoid interference
               and loss of data. Unlike rainfallo streamflow, and storm surge, every piece
               of.wave data is required in order to obtain wave spectral parameters. Conse-
               quently, measurements of full wave characteristics cannot be sent over the
               same radio frequencies or use the existing radio repeaters and base station
               receivers that are part of ASERT without compromising the wave data. (61,110,116,
               117,174)

                       COASTAL MONITORING, FORECAST AND WARNING PROGRAMS

                  Several significant developments are underway or planned which may influence
               the way in which a Connecticut coastal flood monitoring network and warning
               system should be designed and operated.       In addition, several existing real-
               time monitoring and warning networks provide, useful information for design
               considerations.

                                                      4-19

                         Federal Program Activities

                EEMAHURRI!QANEPRFPAREnNESSPROGRA FEMA, in cooperation with NWS, the COE
                and coastal states, has underway a Hurricane Preparedness Program. Among
                the objectives of this program is the development of special evacuation elements
                for inclusion  in state and local emergency operations plans, in response to
                the approach of hurricanes in bigb-@risk, bigh-population areas. A complete
                Hurricane Preparedness Study for a region may require 3-5 years to complete
                and cost on the order of $2,000,000. The studies are federally funded with
                contributions from FEMA, NWS, and COE. State and local officials contribute
                staff time to work with federal agencies.

                   One of the first elements of a Hurricane Preparedness Study is performance
                of a Hurricane Hazard Analysis. This is an analysis of the expected hazards
                that would require the temporary emergency relocation of some portion of the
                population. The results of the analysis form the basis for determining vulnerable
                areas that require evacuation. The principal tool used in the hazard analysis
                is the NWS SLOSH model. Instead of running SLOSH in a real-time mode, it
                is used to run a      series of simulations of possible hurricanes.        Normally,
                the five storm intensities of the Saffir/Simpson scale are simulated. Three
                hundred or more simulation runs may be performed, representing various combinations
                of burricaneintensity, track, size, and forward speed.

                   Each hypothetical hurricane simulated by SLOSH would confront      an area with
                one of many distinct hazard scenarios which, in turn, ultimately      make up the
                evacuation scenarios, or levels. The output of the SLOSH model        provides four
                major types of information on the effects of the simulated hurricanes. They
                are: 1) Surface envelope of highest surges above mean sea.level; 2) Time histories
                of surges at selected gages or grid points; 3) Computed wind speeds at selected
                gages or grid points; and 4) Computed wind directions at selected gages or
                grid points. The results of individual surge mo     Idel simulations (and/or groups
                of common intensity/track types, termed Maximum Envelopes of Water - MEOWs),
                will provide predicted storm surge elevations.        Innundation maps based on
                these predicted storm surge elevations will indicate vulnerable coastal areas
                and will form the basis for several distinct' evacuation levels.

                                                     4-20

                   According to FEMA a nd NWS personnel, current plans are, to begin the Hurricane
                Hazard Analysis, including running hurricane simulations for the Narrangansett/-
                Buzzards Bay SLOSH basin (Figure 4.2 and     B.3),, in the latter part of calendar
                year 1986.    A definite schedule for beginning a Hurricane Hazard -Analysis
                for the New York/Long Island Sound SLOSH basin (Figure 4.2 and B.4).has not
                yet been established, but it may begin in FY 87. The start. date will depend
                upon available funding and . priorities among basins.        Once the simulations
                for these basins have been run and MEOWs developed, the MEOWs will.form the
                basis for evacuation notices; not the forecast storm surge from a real-time
                SLOSH run. 'Although NWS will continue to run SLOSH in a real-time mode as
                a hurricane approaches, it will base all public warnings for evacuation purposes
                on the MEOWs applicable to the forecast track, intensity and forward speed
                of the hurricane. The accuracy of the MEOWs relative to the actual storm
                surge will largely depend upon the accuracy of the hurricane forecast.

                   As indicated in Section 4.1 and Appendix 13@ the SLOSH model may have some
                limitations as applied to LIS. Connecticut (as well as New York and Rhode
                Island) officials should work closely with the FEMA, NWS and COE in the application
                of the model to LIS to ensure the most favorable results. (71972,93296p979118p
                119,1201, 121,122)

                NOS KGWLMS PROGRA The NOS operates and maintains the National Water Level
                Observation Network (NWLON) to accomplish its mission requirement for measuring
                and disseminating tides and water level data.       Because the technology used
                to support the NWLON is aging and obsolete, NOS will replace it with a modernized
                system,, the Next Generation Water Level Measurement System (NGWLMS). NGWLMS
                is a fully integrated system encompassing new technology sensors and recording
                equipment, multiple data transmission options, and an integrated data processing,
                an alysis and dissemination system.,

                   NOS has, selected an acoustic gage (manufactured by Bartex, Inc., and described
                in Section 4.2) for measuring tides and storm surge, with a pressure gage
                as backup. The acoustic gage will receive further . evaluation during initial
                installations, so its selection   'is not entirely assured for the entire new
                system.  NOS apparently has, no plans to measure wave characteristics (most
                NOS gage stations are located in areas at least partially protected from wave

                                                          4-21

                  action).    Information will be collected and transmitted in near real-ti             me.
                  The primary means of data transmission will be by GOES Satellite. Radio and
                  telephone telemetry       is also planned.      Figure 4.7 illustrates the proposed
                  system. NOS plans to      make available to interested users a software program
                  (floppy disk for-use in   a microcomputer) which will enable the users to obtain
                  both actual (near real-time) and predicted (as in published tide tables) tide
                  levels by connecting with any NOS gage through a telephone modem.

                     NOS hopes to have NGWLMS fully op       erational  in the late 1.980s or early 1990s.
                  However, the schedule for upgrading tide stations has not been finalized and
                  will depend upon several factors such as need for equipment replacement, geographic
                  spread of initial installations to be used for continued testing and evaluation,
                  and available budget. NOS has indicated that it would invite interested states
                  to enter into cooperative agreements for early installation of gages in their.
                  area (in Connecticut one of the two NOS gages could potentially be included
                  as an early installation). (27v98,123, 1241,125)

                  NWS  TRLFMRTRY JJPDATE       The NWS generally does not own and operate its own tide'
                  gage stations. But at many NOS gage stations, such as Bridgeport, the NWS
                  does  operate a tide level recording unit off of the NOS primary gage. The
                  existing equipment (Bristol Metameter) is old and no longer reliable, so the
                  NWS is now installing new telemetry instrumentation (Ha        ndar, Inc., Model 540A)
                  at selected NOS gage stations. This new instrumentation is intended to provide.
                  near real-time data to the NMC in Silver -Springs to improve NWS forecasting
                  ability, as well as continue      to have real-time data available in local NWS
                  offices. Use of this new equipment is intended to be temporary: as NOS upgrades
                  its NWLON system with the new gages and telemetry, NWS will remove its Handar
                  instruments. and. redeploy them in riv    erine areas. A Handar unit is expected
                  to be installed by NWS at the Bridgeport NOS gage in the very near future
                  (unit already available at Bridgeport WSO office). One disadvantage to the
                  Handar equipment is that it will not provide a continuous display and chart
                  record of tide levels as the present Bristol equipment does. Instead, local
                  NWS personnel    must interrograte the gage to obtain tide levels. (32,33,34,98,117,
                  1239124,125t126v127)

                                                                                                                                000
                                                                                                                                  GOES
                                                     Optional Telephone Link
                                                     to Real Time Users                                                                                                 N::r.Real Time
                                                                                                                                                                               a  Academic Instl
                                                                                                                                                                               a  NWS
                                                                          CRT                                                                                                  a  Marine boundar
                                                                                                                                                                                  Programs
                                                                                                                                                                               a  Others
                                                     a Pilots
                                                     a Shipping Companies
                                                     a Port Authorities
                                                     a Vessel Traffic Control
                                                     6 KWS                                                                                                  F--DQA
                                                     a Others                                       4@
                                                                                                         S

                                                                                                                                            Satellite Down
                                                                                                                                            Link               Master Collection
                                   Optional Radio Link                                                                                                         computers
                                   to Real Time Users

                                                                                            Optional                     n
                                                                                            Telephone ink
                                                                                 A
                                                                                                    Level
                                                        Miccoprocansd            I

                                                           DQ
                                                                                 u                                                                                             Data
                                                                                 z                                                                                            processing
                                                                                                                           ionsor Referenced                                  Computer
                                                                                                                           to bench mark System

                                                                                                   Tide Staff for
                                   G                                                               Periodic Chocks
                                   ,;neral Navigation
                                    drography
                               a Dredging                                              Air Acoustic or Non-contact Sensor
                                                                                       in ecotective/Stilling Well

                                                                                   Other Sensors as Required
                                                           Optional                 (i.e.. water temperature.   salinity,
                                                                                     currents. irul direction   and speed,
                                                           Pressure                 air temperaturej barometric pressure, etc.)
                                                           Sensor

                           SOURCE: Deibelp Lawrence E., and Barbara A. Zumwalt.                                       1985. Next Generation
                                          Water Level Measurement System Program. By The Mitre Corporation
                                          for National Ocean Service, NOAA, Dept. of Commerce.

                                                           FIGURE 4.7: National Ocean Service NGWLMS System

                                                      4-23

                 FEDERAL INURAGENCY STANDARDS COMMITTEE In response to the lack of standarization
                 in the equipment manufactured for. measurement,, transmission and analysis of
                 meteorologic, hydrologic and oceanographic data, a-federal interagency standards
                 committee was formed in the summer of 1985. The first meeting of the committee
                 was scheduled for October, 1985. (98,128)

                 FEMA IRMIS PROGRA FEMA-has developed an Integrated Emergency Management
                 Information System (IEMIS) that is intended to allow FEMA headquarters, training
                 center and regional offices,. and state and local governments to perform data
                 sharing, joint planning, exercising and - potentially -- operational coordina-
                 t ion. Currently, the system is on-line at the FEMA headquar        ters, regional
                 officesi and training center. IEMIS uses a 'standard national map for display
                 of information. The system originated with FEMA's Radiological Emergency
                 Preparedness Program, and future de. velopments are planned to include adaptations
                 for hurricane evacuation and evacuations below failed dams, among others.

                    Currently; FEMA is cooperating with the NWS and City of Tulsa, Oklahoma
                 in development- of, an operational flood warning system on IEMIS. FEMA indicated
                 that it is seeking other states, localities and private contractors to participate
                 in pilot projects. Other states actively' involved with IEMIS include Louisiana
                 and Massachusetts. Connecticut is not presently pursuing operational invo   lvement
                   ith IEMIS.- Although IEMIS program goals are ambitious, it is unclear at
                 this time whether there is a real need or opportunity for a Connecticut coastal
                 w

                 flood monitoring network and warning system to be operationally compatible
                 with IEMIS.'(1219129913091319132,1339 134)

                 4=      Real-Time  Programs

                 COA5TAL              RNING PROGRAMS

                    Tsunami Warning   TheNWS,'in cooperation with NOS, operates a tsunami,warning
                 system An the' Pacific Ocean. Wave data is telemetered to a central receiving
                 station. When an earthquake occurs or wave characteristics indicate the potential
                 for a tsunami, the gages are signaled to increase their sampling rate. (27)

                                                    4-24

                  Harrison County, Mississippi Water Level Monitoring System The Harrison
               County, Mississippi Office of Civil Preparedness (Gulfport area) is currently
               developing a real-time.flood warning system. This system is very similar
               to the Connecticut ASERTIALERT system, and will include 3 river and 3 coastal
               sites. Data will be transmitted by VHF radio to the Civil Preparedness office.
               Officials feel this system will provide them with accurate information on
               storm surge without having to send out observers under dangerous conditions.
               Wave characteristics will not be measured, nor is any predliction of storm
               surge planned. (163,164)

                  Thamgs River Fs  tuary. England An operational system in the Thames River
               Estuary provides the Canterbury City Council with real-time data on tide and
               wind conditions. One station (pressure transducer) in the harbor at Whitstable,
               transmits tide and wind data at regular intervals by dedicated telephone line
               to the Council offices in Canterbury. A similar station out in the estuary
               transmits data by radio frequency. The receiving station is. equipped with
               a modem and a speech synthesizer, so that it may be accessed from any location
               and a synthesized voice will report tide and wind conditions. (165)

                  Ganges River/Buy of Bgngral Flood J%arning Network In cooperation with the
               National Aeronautics and Space Administration (NASA), the government of Bangladesh
               has installed a network of 10. tide gages along the Ganges 'River and a fully
               equipped meteorological buoy in the,Bay of Bengal. Data are transmitted through
               the ARGOS Satellite System to a ground station in Dacca, the capitol of Bangla-
               desh. Early warnings provided by this system were credited with saving numerous
               lives during the disastrous May 1985 cyclone which struck the Bay of Bengal.
               (166,167)

               NAVIGATION PROJECTS

                  New York Harbor Tidal Gage System The "New York Harbor Tidal Gauge System"
               is a cooperative effort between NOS, New York Department of State and the
               Maritime Administration of the, Port of New York (MAPONY). It provides real-time
               water level data from four NOS tide gages., The system is oriented primarily
               towards navigation, but can also be used for other purposes, including input
               to weather forecasts. Tide level data from the four gages are available via

                                                           4-25

                   telephone telemetry to a microcomputer (IBM PC) at MAPONY offices, the New
                   York WSFO and system subscribers. Data are available on a computer terminal
                   display or paper printout (See Figure 4.8).         No provision has been made for
                   permanent data storage.

                      System installation costs' of $250,000 were provided by   the New York Department
                   of State. Anyone may subscribe to the system with a $100 connection fee and
                  .$100 monthly charge. A compatible microcomputer or terminal and a modem are
                   all that is required to access the system.          The system was intended to be
                   financially selfsupporting through subscriber fees, but there are currently
                   only three paid subscribers and the possibility exists that the system may
                   be shut down. Although reportedly providing accurate and useful information,
                   the system has suffered reliability problems because of difficulties with
                   the telephone lines.

                      The primary users of the information are the NWS and the Sandy Hook Pilots
                   Association (movement of ships in and out of New York Harbor). The New York
                   WSFO, uses data from the system as input to its weather and stor      m surge forecasts,
                   including data during Hurricane Gloria.         Altb ougb proponents of the. system
                   (including NOS and MAPONY) speak of the tremendous financial savings available
                   to ship owners by being able to move ships sooner or more fully loaded, most
                   ship owners apparently remain unconvinced. and have bee         n unwilling to provide
                   financial support for the system.

                      The Ne  w York WSFO reported that        it found real-time information from the
                   network to be of great value during         Hurricane Gloria. One station was not
                   operational during Hurricane Gloria because of problems with the telephone
                   lines, another gage was operational during only part of the storm, and two
                   gages were operational through           the entire storm. (22J25913944091419142J43,
                   1449146tl47,148,149,153)

                      Delaware Bay Navigation     Project     NOS has funded a      special  Delaware Bay
                   Program which incorporates      a numerical    model of tide    levels and   currents in
                   the Bay. The model, combined with four acoustic           tide  gages, several current
                   meters, and meteorological instruments provides real-time and predicted data
                   on currents and tide levels     in Delaware Bay. This information is telemetered

                                                                   4-26

                          -----------------------------------------------------------------------------
                           PORT OF NEW YORK TIDE TELEMETRY SYS-EM                MAP 01
                                        SAMPLE     TIDE        6IND          WIND       WIND        DATA       SYSTEM
                          -<EMOTE         TIME     LEVEL      tPEED        DIRECT       GUST       OUALITY     STATUS
                          STATION       CEST3      EFEET]     [ K.',107S    .-DEG-T.-. fKt.'r-.'TS] CoCrE      ncdob
                          -------------------------------------------------------------------------------

                          SANDY HOOK    09:18      +00.6         09          260
                          BATTERY       09:18      +00.5         oc
                          BERGEN PNT    09:18      +00.8                     224
                          iT: @ =--
                                        OF:18      +02.7

                                  HOOK  0?:24      +00.6         09          258
                          BATTERY       09:24      +00.5
                          BERGEN PNT    09:24      +00.7         05          225
                          WILLETS       09:24      +02.6

                          SANDY HOOK    09:30      +00.5         09          257
                          BATTERY       09-30      +00.5
                          BERGEN PNT    09:30      +00.7         05          227
                          WILLETS       09:30      +02.5

                          SANDY HOOK    09:36      +00.5         09          258
                          BATTERY       09:36      +00.5
                          BERGEN PNT    09:36      +00.7         07          200
                          WILLETS       0.9:36     +02.4

                          ANDY HOOK     09:42      +00.5         09          258
                          BATTERY       09:42      +00.5
                          BERGEN PNT    09:42      +00.6         08          203
                          WILLETS       09:42      +02.3

                          SANDY HOOK    09:48      +00.5         04          258
                          BATTERY       09:48      +00.5
                          BERGEN PNT    09:48      +00.6         06          216
                          WILLETS       09:48      +02.2

                          SANDY HOOK    09:54      +00.6         04          258
                          BATTERY       09:54      +00.4
                          BERGEN PNT    09:54      +00-6         08          208
                          WILLETS       09.54      +02.1

                          SOURCE:     Maritime Administration of the Port of New York, New
                                      York, New York

                           FIGURE 4.8: Sample Display of Tidal Datafrom New York
                                                Harbor Tidal'Gage System

                                                       4-27

                 via VHF radio t'o several       computer terminals, including portable terminals
                 for use on ships by Delaware Bay Harbor Pilots. 'The numerical model has been
                 kept on-line by NOS at a cost of several thousand dollars per month. Recently,
                 the system was taken off-line because of costs.        Although the model predicts
                 water levels up to 12 hours in advance, it was not. designed to provide an
                 accurate prediction of storm surge (does. not include all necessary wind stress
                 f ields). (124,125,150,151)

                    Addi tional NOS Supported Navigation Projects NOS has also helped develop,
                 in cooperation,  with the COE, a real-time navigation system in the Columbia
                 River, Oregon; recently entered into an agreement with the Port of Miami;
                 and is discussing agreements with ports at Charleston, South Carolina and
                 Baltimore and Annapolis, Maryland in Chesapeake Bay. Although NOS indicated
                 that it can no longer provide funding for pilot projects, it will enter into
                 cooperative agreements with states and other jurisdictions to provide technical
                 assistance in the development of real-t     ime navigation systems. (27,124,125,153)

                    Othe r Real-Time NaMigration PrograM Other real-time navigation 'programs
                 are in operation   around the country, including two privately operated systems
                 .in San Francisco  Bay. One of these    (apparently no longer operating) consisted
                 of seven tide stations     transmitting every six minutes.     It was designed to
                 be self-supporting, charging users a.   fee of $25 for each ship transit. Another
                 private firm operates a single tide gage at the San Francisco Bay Bridge.
                 Since this gage is tied to an ALERT type system'. a typical graphic display
                 from this  gage  is shown as Figure 4.9. Many tide gages        with real-time data
                 transmission are used by dred    ging operations in the Great Lakes and other
                 locations. (61,154,155,156,157)

                    National Academ@ of Sciences Report The NAS, National          Research Council,,
                 Marine -Board ha's established a-Committee on Information for Port and Harbor'
                 Operations to examine the potential for real-time navigation in ports and
                 harbors. The committee report is due out approximately       April, 1986. N6 infor-
                 mation is currently available from NAS. (143v152)

               Colden Gate Stream Gage
                  6.0      1  f

                  5.4
                                 A
                e 4.8
                                      v
                  4.2                               N',

                  3.6

                  3,0.
                HOUR 12 a  I'll- 0 120 12    12     1.20
                 DAY 94 10-)  11+   19?,4

                  FIGURE 4.9: Sample Display from Tidal Gage in San Francisco
                           Bay; ALERT Type Network
                                       Lv-

     MM@MMMMM MINN MWWWM MMM

                                                          4-29

                  RESEARCH PROJECTS

                     Other real-time *tide, storm surge and wave measurement programs 'are in
                  operation. Two major projects are described below.

                     West Coast Wave Measurement NetWork The COE and the California Department
                  of Boating and Waterways have funded a Coastal Data Information Program for
                  the collection of wave data along the west coast of the U.S. The system was
                  designed and is operated by the !Scripps Institute of Oceanography (SIO).
                  The primary purpose 'of the progr     am is to improve understanding of the wave
                  climate along the west coast. Knowledge of the wave climate *helps with under-
                  Standing the potential for'"sedimient'    transport and coastal erosion, which are
                  of major concern on the west coast.        Major, users of 'the information are SIO,
                  the COE, coastal engineers, and more      recently the, NWS and U.S. Navy.

                     The complete network consists of' about       20 gages, including wave     buoys and
                  wave directional stations in deep water and pressure gages near shore. The
                  near shore sites use bottom mounted strain gag        e pressure sensors.    Data from
                  each gage are telemetered to a field station (by VHF radio from deep water
                  wave buoys, and by cable from near shore pressure gages), where time series
                  wave data! are 'stored in a buffer. At preset intervals,, the central station
                  computer at Scripps calls up the field stat     ions, receives data from the buffer,
                  performs validity checks, analyses the data, and stores the data in a
                  During major storms, more frequent measurements can be taken. Data are available
                  in near real-Aime to all 'system subscribers, who may acce        Iss the system using
                  a microcomputer or terminal and a modem. Historical data are also available
                  orr-line. Raw data are stored by the COE, Coastal Engineering Research Center
                  (CERC) office in Vicksburg,, Mississippi.

                     Date on significant wave length andperib'd (wave spectral         dat a is not   sent)
                  are transmitted from the SIO central station computer by telephone lines to
                  the NWS computer in San Diego. There the data are entered into the NWS AFOS
                  system (Automation of Field Operations and Service), transmitted to the NMC
                  in Silver Springs, Maryland, and then. sent back out over the AFOS system every
                  three hours to NWS offices in California, Oregon and Washington. These NWS
                  offices use the data in preparing forecasts and to report actual surge and

                                                    4-30

               wave conditions in their routine weather bulletins released over NOAA weather
               radio.  This information is apparently very useful for fishermen and other
               mariners. The NWS reports that it has had good success in obtaining and using
               data from the SIO network. Even when the NWS AFOS system is temporarily down,
               the NWS can call into the SIO computer system using an IBM PC microcomputer.
               Recently the U.S. Navy has begun using the SIO network as part of a tsunami
               warning system.

                  In addition to the west   coast network, the SIO system includes one station
               at the COE,   CERC research station at Duck, North C       arolina. SIO personnel
               indicated that they are interested in adding other stations to their network,
               possibly including a future Connecticut network of storm surge and wave gages.
               Data from the local stations would be input to the SIO computer, analyzed
               and them sent back out to the local area. Only a terminal and modem are needed
               to connect with the SIO system. SIO charges private users a subscription
               for participating in the system, and would *make it. available to a government
               user with an appro  priate contribution (the State of California presently con-
               tributes $50,000/year, and is expected to increase their support to $100,000/-
               year). SIO could also assist with installation of gages and telemetry. SIO
               publishes a monthly and annual report which summarize the data collected by
               the system. A subscription costs $95.00/year. (115,135,136913791389175)

                  Florida Monitoring    Network    The University of Florida at Gainsville, in
               cooperation with the COE, CERC has developed a coastal storm surge and wave
               monitoring system off the Florida coast. This system is designed to collect
               data for engineering design and research purposes, and is not used for forecasting
               storms or surge. A network of approximately nine pressure transducer gages
               is installed on the ocean bottom at a depth of about 10 meters around the
               Florida coast, approximately one-half mile offshore. Under normal conditions,
               the system transmits data via underwater telephone cable to the receiving
               unit at the University. During major storms, the system (two-way communications)
               is switched to an internal mode, and data are recorded on tape stored within
               the gages. (1589159,16091619162)

                                                     4-31

                         Long Island Sound Water Quality Program

                    The State of Connecticut recently began work on a new program to investigate
                 water quality and marine living resources in Long Island Sound. Efforts will
                 be focused on the western part of the Sound, where sewage effluent and other
                 pollutants from New York City enter LIS through the East River. The program
                 is expected. to include long term monitoring of nutrient input, productivity,
                 and circulation, which may involve tide and current meters at selected areas
                 in LIS. At a recent workshop, participants suggested that a two-dimensional,
                 vertically integrated, numerical circulation model of the Sound be developed.
                 Development costs for the model were estimated at more than $500,000. Start-up
                 funding may be available in FY 1987. (177,178,179)

                                                                          5-1

                                               5.0: FLOOD MONITURINQ NETWORK D

                          This   section describes the general design                  of four different flood monitoring
                      networks.        Each network design provides a                  different degree of compatibility
                      with the Connecticut, ASERT system, as well as variations in the type and quality
                      of data     to be collected. Variations and enhancements to each network design
                      are also indicated. The final choice of a preferred network design depends
                      upon a number of factors, including: State budget, funding levels for federal
                      programs directly related to flood monitoring and warning; how dependent the
                      State network should be on other federal, state or private programs; and user
                      needs to be met.

                                 DESIGN     Q

                          An optimal flood monitoring network would possess the following characteristics.
                      (1)     Accurate measurement of tides, storm surge, and wave spectral character-
                              istics.
                      (2)     Sufficient number and placement of stations to measure all significant
                              variation in tide, storm.surge and wave action along. the CT coast.
                      (3)     Accurate measurement of wind speed, wind direction, and barometric pressure
                              at each gage station.
                      (4)     High reliablility, including continued operation under severe storm
                              conditions.
                      (5)     Ability to. increase sampling frequency during storms, or at other times
                              as needed, from the central receiving station.
                      (6).    Data available in real- or near real-@-time to potential users,                           including
                              State emergency officials., municipal officials, NWS, navigation interests,
                              and researchers..
                      (7)     Audible alarms           when storm surge and wave conditions exceed critical
                              levels.
                      (8)     Processing and display of data to             'permit easy interpretation and use.
                      (9)     Archiving of data for research a             Ind verification purposes.
                      (10)    Low equipment and installation costs.
                      (11)    Low maintenance costs, including long life.for                   equipment.
                      (12)    Fully compatible with ASERT.

                          No    single network design appears to meet all of these                             criteria.     In the
                      following sections, several network designs                  are, presented, each        of which requires
                      some compromise on one or more.of tbe,criteria.

                                                    5-2

                       NUMBER AND LOCATI N OF GAGF-q

                       Tides and Storm Surga

                  To measure tidal action and storm surge affecting coastal communities,
               gages should be placed at a near-shore location, outside the breaker zone.
               Although tides and storm surge are affected. by shoreline configuration and
               the presence of manmade and natural obstacles, this affect in LIS is relatively
               small. (6.7,46) Therefore, gages may be placed along the open coast or within
               a protected harbor with confidence that the measured tide and surge will not
               vary greatly from nearby locations.

                  No projected storm surge data from numerical models is available for        the
               Connecticut coast to provide guidance for placement of storm surge gages along
               the coastlinel. Therefore, empirical data gathered from storm surge observations
               and statistical studies of storm surge must be used to suggest the placement
               of gages. These data indicate that a reasonable measu     rement of storm surge
               along the Connecticut can be obtained by locat ing gages in five areas.

                       Stonillgton to New London     Storm surge decreases from Stonington to
                       New London where it reaches a local minimum. The large amplification
                       of storm surge in the Thames River also makes this area important
                       for measurement.

               (2)     Waterford to East Haven      This reach has a  n almost constant upward
                       slope in storm surge from east to west. A point about midway along
                       this reach should permit determination of surge along the entire area.

               (3)     Nfijm Haven area: A local maximum in storm surge occurs in the area
                       of New Haven, and should be measured.

               (4)     Milford to Bridveaark-      A significant and rapid decrease in storm
                       surge levels occurs in this area. It is also the lowest point for
                       storm surge along the Connecticut coast.

               (5)     Greenwich/Stamford area: Storm surge is largest in western Connecticut,
                       and this is also an area with complex offshore batbymetry and offshore

                iThe N WS SLOSH storm surge model is now operational, but projected storm surges
               from theoretical hurricanes have not yet been prepared. Storm surge estimates
               for the Connecticut coast prepared during Hurricane Gloria were not available
               from the NWS for this study. There Are no other operational storm surge models
               that cover the entire Connecticut coast.

                                                            5-3

                            islands.

                      Measurement of storm surge at these five areas should permit a reasonable
                  estimation of storm surge at other coastal areas.               However, the choi    ce of
                  these five areas is based on historical statistical studies that minimizes

                  local variations and differences associated with individual storms. To           determine
                  just  how extensive local variations in storm surge may be, it is                suggested
                  that, in -addition to establishing 'permanent measurement stations at these
                  five sites, additional gages be placed at critical points along                  the coast
                  for temporary      periods.   These' temporary stations can be used to correlate
                  storm surge at intermediate locations with adjacent permanent                    stations2.
                  To account for seasonal variations, these temporary stations should remain
                  in place at least one year.

                  L=        Waves

                      Two major   options  are available for   the placement of   wave gages:

                  (1)       Wave  gages may be placed in adeep water offshore, beyond the zone of
                            major shoaling.     Data from offshore gages, although not specific to
                            any single location,, can then used in a wave model (including wave
                            refraction, diffraction, reflection) to obtain wave estimates closer
                            to shore.    As discussed.in Appendix B@ the ability of models to shoal
                            waves accurately is limited, and if the wave data are sufficiently
                            far offshore that wave generation continues between the gaging site
                            and the shore location, the shoaled wave estimates will be incorrect.
                            The primary advantage of offshore gages is that a few gages can be
                            used as representative of a large section of coastline.

                  (2)       Wave gages can be placed very close to shore, such that the waves
                            measured are those that impinge directly onto the shoreline. The advantage
                            is that accurate, site-specific information is available for the local
                            shoreline.    The disadvantage is that the wave data cannot be used
                            for adjacent coastal sites, without expensive and often inaccurate
                            modeling efforts which estimate offshore     waves from the inshore measure-
                            ments,, then shoaling of these offshore waves into the candidate site.

                    2
                     This  would be similar -to    NOS procedures     of placing temporary, subordinate,
                  tidal stations at many points along the coast to establish tidal correlations
                  with its  two permanent tidal stations in Connecticut.

                                                      5-4

                  Because waves in much of LIS are primarily generated by local winds rather
               than offshore swells, and the need for site-specific data, near-shore gage
               stations are suggested, even' though the wave data may not always be used to
               estimate wave action at ungaged, nearby locations.

                  From a theoretical standpoint, there is no single optimum spacing of wave
               gages along the Connecticut shoreline.          Waves will develop differently in
               LIS, depending on the wind speed, direction, and orientation of the coastline.
                For instance, winds moving along the maximum east-west fetch of LIS will
               exhibit large alongshore gradients in the spectral wave characteristics, i.e.,
               wave height and peak wave period will grow continuously with distance down
               the Sound. Local effects such as sheltering by offshore islands, or refraction
               by shoals, will cause significant local variability.          This sheltering and
               refraction will affect different parts and lengths of the coast according
               to wind speed and wind direction.

                  Optimally', some guidance in locating gage stations would come from previous
               studies of waves within LIS, either in situ measurements or numerical modeling..
                As is typical for much of the east coast of the United States, little direct
               measurement of waves has been made in LIS, and no comprehensive, long-term
               monitoring gage   records exist.   Most records are very short, and of uncertain
               quality, and do   not warrant use in setting the spacing and location of wave
               stations.

                  Visual observations of waves have been made at a number        of locations along
               the coast of Connecticut as part of the Beach Erosion Project established
               following the Ash Wednesday storm of 1962 (181). These data are of questionable
               quality, since visual observations are known to be biased and inexact. Although
               these data were examined to try to establish      a sound basis for locating gages,
               this effort proved unsuccessful.

                  Calculation of wave development in LIS using empirical hindeast techniques
               suggests that at a minimum three wave gages should be located along the shore.
                In the eastern part of the     Sound, waves are ne   arly those of the more open
               coastal waters of the Atlantic. I Further west, in the middle regions of LIS,
               the waves become more typical of a sheltered embayment, while to the far west,

                                                           5-5

                   the wave  s are almost entirely shallow-watert locally generated waves.

                      The combination- of the alongshore gradients in wave action and the complex
                   nearshore bathymetry results in a *recommendation to place three                permanent
                   wave gages al. ong the Connecticut shoreline.

                   (1)      Eastern Connecticut, One gage        should be located in the eastern part
                            of the sound, along a section        of shoreline exposed to both locally-
                            generated waves and more distantly generated ocean swell (but outside
                            the immediate influence of Fisher's Island.

                   (2)      Mid-State.     Another gage is suggested near mid-state, offshore of
                            New 1-faven.    Waves in this area are, predominantly locally generated
                            within the Bound, having a large fetch during both westerly and easterly
                            winds. Although somewhat sheltered from westerly winds by the shoals
                            off Bridgeport, it is exposed fully to the brunt of an easterly wind.

                   (3)      West ern ConnecticuL Another gage should 'be located near Stamford
                            or Greenwich. This location is representa        'tive. of . much of the western
                            part of the State, with its crenulated shoreline, and variable offshore
                            batbymetry.     This area is subject to only a minor westerly fetch,
                            but the long easterly fetch could potentially generate large waves..

                      Because of local topography and offshore islands, these three sites will
                   not be representative of all sbore points. For example, they will not permit
                   determination of wave action in Fisher's Island Sound. Because the communities
                   in this reach of coastline (Stonington,        Groton, New London, Waterford, and
                   East Lyme) have few structures in the.V-Zone             (ref er to Table 2.4), absence
                   of a wave gage here is not critical. A         permanent gage     can be added in this
                   area later if needed. To      determine if additional permanent gages are needed
                   and to attempt statistical correlation         of wave beh    avior between the sites
                   with permanent gages and nearby ungaged sites, it is recommended that two
                   additional  wave gages be used to temporarily measure sites at various locations
                   along the   coast. Because    wave climate during, a variety      of weather conditions
                   is desired, .and   to reduce   installation and removal costs, it is recommended
                   that the roving    wave gage stations remain       at each'temporary location for at
                   least two  years.

                                      ME NRTWORK DEEIGNS

                      Based on the     desi gn criteria given in   Section 5.1 and the recommendations

                                                     5-6

               for number and location of gages in Section 5.2, this section     describes several
               alternative network designs. Network designs which are ASERT compatible are
               presented, as required by the initial study objectives. However, since -these
               designs must either omit or compromise wave data (or compromise reliability
               of the ASERT system), other network designs are also presented. One set of
               alternatives involves a wave network separate from the ASERT compatible storm
               surge network. Another alternative describes a network -totally independent
               of ASERT.     The - major alternative network designs, with possible variations
               on each, are described below and summarized in Table 5.1.

               5,3,1   Cautions on Cost Estimates

                  Cost estimates for equipment, software development and installation are
               provided for each alternative described. These estimates must be used with
               great caution.   Although several vendors were contacted for cost estimates,
               most were reluctant to provide estimates without a detailed set of specifications.
               Those estimates provided by vendors were not always comparable because they
               made varying assumptions regarding instrumentation needs. Some vendors provided
               estimates for a  complete monitoring network, while others provided only costs
               of individual components. Costs of similar equipment can vary greatly depending
               .upon quality and design standards. The equipment cost estimates in this report
               were developed by the contractor based on information provided by vendors
               and past experience with vendors and equipment at WHOI and elsewhere. The
               estimates should be considered more as relative values than as absolute cost

               ,estimates.

                   Similarily, cost estimates for installation are approximate, and should
               be considered  relative rather than absolute. Installation costs do not include
               surveying to establish reference elevations.

                       Tide and Storm Surge Measurements* (ASERT Compatible Network)

               GFNRRALDESr,RTPTI0 An ASERT compatible network that measures tidal movement
               and storm surge can be established that relies heavily on use of existing
               recording tide stations.

                                      ALTERNATIVE NE  .TWORK DESIGNS         ASERT COMPATIBILITY                SAGE STATIONS                   TYPE OF SAGE             APPRO
                                                                                                                                                                              COE

                                   TIDE AND STORM   SURGE                                                  Existing stations at New
                                   (ASERT Compatible).                                                     London, Old Saybrook,
                                                                                                           Bridgeport, and
                                   i-a Maximum Use of Existing             Pully Compatible                Stamford. New Station          Existing gages fitted          51,000
                                        Instrumentation                                                    at New Haven. Two              with interface. Strain
                                                                                                           roving stations                gage pressure sensor at
                                                                                                                                          Now Haven and roving
                                                                                                                                          stations.

                                   1-b Upgraded Instrumentation            Fully Compatible                                               Strain gage pressure           58,500
                                                                                                                                          sensor or NOS gage

                             2.    TIDE, STORM SURGE AND.WAVE                                              Same as Alternative I          Top-of-the-line strain
                                   MEASUREMENTS                                                            except for a new station       gage pressure sensor or
                                   (ASERT Compatible)                                                      at Stamford Harbor             quaVtz pressure     sensor.
                                                                                                           Breakwater to replace
                                   2-a  Simplified Wave Data               Some  wave data may be          existing Stamford Harbor                                      100,00
                                                                           lost  due to.interference       gage, and relocation of
                                   2-h  Field Station Processing                                           Old Saybrook gage site
                                        of Spectral Wave Data                                              to open water side of
                                                                                                           breakwater.
                                        2-b.1 Transmittal of               Higher  percentage   of                                                                       115,00
                                                processed spectral         wave data loss due"to
                                                data                       longer transmission
                                                                           time,  and overall    higher
                                                                           ratio  of signal
                                                                           interference

                                        .2-b.2 Store spectral data         Some wave data may be                                                                         I 18'00@
                                                at field station           lost due to interference

                             3.    TIDE, STORM  SORGE AND WAVE             @Only 2 stations                Same as Alternative 2          Top-of-the-line strain
                                   MEASUREMENTS                            (Bridgeport and New                                            gage pressure sensor or
                                   (Two Networks)                          London) are-ASERT                                              quartz pressure sensor.
                                                                           compatible. Stations
                                   3-a  One-way Communications             with wave gages are an a                                                                      158,00
                                                                           separate network                                                                              2018,00

                                   3-b  'Two-way Communications                                                                                                          280,00
                                                                                                                                                                         330,00

                                   3-c  Linkage to SIO Wave,                                                                                                             163,00
                                        Monitoring System                                                                                                                335.00

                             4.    TIDE, STORM SURGE AND WAVE              No t compati ble                Same as Alternative 2          Quartz pressure sensor         440,00
                                   MEASUREMENTS                            entirely separate system
                                   (Independent from ASERT)

                                                              TABLE 5.1: Summary of Alternative Network Designs

                                                     5-8

                  Station Locations For this netw  ork, five permanent and two temporary "roving"
               stations are recommended (Figure 5.1).
                                               EXISTING STATIONS

               (1)      NOS station in the Thames River at New London.
               (2)      USGS/DEP station at Saybrook Breakwater at, the mouth of the Connecticut
                        River.
               (3)      NOS station in Bridgeport Harbor.
               (4)      COEIUSGS station in Stamford Harbor.

                                                  NEW STATION

               (5)      New Haven Harbor. A new station would be located at the West Breakwater
                        at the entrance to New Haven Harbor.

                                                ROVING STATIONS

               (6)      At sites to be selected
               (7)      At sites to be selected

                  Station Description    Each station would be equipped with water level and
               meteorological sensors (wind speed and direction; barometric pressure). Water
               level (stillwater) would be determined and transmitted at 5, 6, or 15 minute
                           and meteorological data would be transmitted on an event basis.
               intervals3
               Each station would be equipped with ASERT compatible encoding and radio trans--
               mission instruments.

                        At the four existing  stations, the transmitter and other instrumentation
               would be located within the   existing instrument housing (NOS instrument housing
               at New London and Bridgeport; Coast Guard lighthouse at Old Saybrook; and
               COE Hurricane Barrier offices at Stamford). For the new station at New Haven
               Harbor, instrumentation would be housed in a Coast Guard lighthouse tower
               located on the breakwater. The antenna and meteorological instrumentation
               could be mounted  to the, tower. Commercial power is available.

                3A measurement frequency of once every       six minutes (10/hour; 125/tidal cycle)
               would be compatible with NOS stations. A     measurement frequency of once every
               15 minutes (4/bour; 60/tidal cycle) would be  compatible with the USGS maintained
               stations.   Existing USGS equipment would permit sampling frequency at the
               USGS stations to be increased to every five minutes (12/hour; 150/tidal cycle)
               (38), which would permit improved graphic display of tide levels.

                                                       j

                                                                       ----------

                                                  0

                                                                                     Thame
                          %                                                         at Ne
                                                                   Old Saybrook
                                                       -Harbor
                                              New Haven             Breakwater

                              Bridgeport Harbor

                                                      Lost
                 Stamford Harbor

               FIGURE 5.1:. Locations oU Permanent Gage Stations     for Tide and Storm S
                            Measurements

                                                     5-10

                  A good quality strain gage pressure sensor is recommended for water level
               measurements4, The pressure sensor would be placed on the ocean bottom, approx-
               imately 100 feet beyond the south edge of the breakwater. The suggested mounting
               for the sensor is a steel pipe tripod, with concrete weights. Cable from
               the sensor should be buried in the sediment and secured against the breakwater.
               (182,183) Figure 5.2 illustrates a typical installation.

                  Data T-            i and Processing,  Data would be telemeteted by VHF radio
               to the existing base stations in Hartford and Bloomfield.          It is anticipated
               that radio signals from all stations could reach the base stations with existing
               ASERT re  peaters, as shown in Figure 5.35. New repeaters would be installed
               if required to get a signal through to the base stations.

                  Receiv ed data  could be processed by the existing Enhanced ALERT software
               (61).  Stillwater   levels could be treated similar to stream level data6
               It is recommended, however, that a new software module be developed for the
               Enhanced ALERT software to process the tide and storm surge data. This module
               would include predicted tide levels for each station using NOS data (Stamford,
               Bridgeport and New London) or NOS procedures for determining tide levels (Old
               Saybrook and New Haven stations) by correlation with the New London or Bridgeport
               stations.   Programming should include triggering an audible alarm whenever
               actual water levels exceed predicted tide levels by a specified amount (such
               as one or   two feet). A graphic display, as well as tabulations, of predicted
               vs. actual water levels should also be included.          Costs of developing this
               module are  estimated at $@,000 to $10,000 (assume $8,000). Archiving of processed
               data would  depend on procedures developed for archiving data from the ASERT
               system. These procedures have not yet been finalized (184).

                4The accuracy   .required from a top-of-the-line strain gage pressure sensor
               or quartz .,pressure sensor is not essential for stations used to measure only
               tide and storm surge.
                5This configuratio .n for signal transmission is based on information from topo-
               graphic maps. No field checks have been made to confirm signal transmission.
                6See for example, Figure.4.9, which is a printout of water level data from
               a tide gage in San Francisco Bay, prepared with the Enhanced ALERT software
               (61).

                                             5-11

                                                 DIPOLE ANTENNA

                                                 WEATHER-TIGHT ELECTRONICS BOX

                                                 STEEL TOWER
                                                 PIER                 20'

                                                                      30'
                                                      TRIPOD MOUNT

                          FIGURE 5.2: Typical    Gage StationInstallation

                                           R- t
                                                                         Z.
                                                                                _UA6

                                                                                                                      SR- I

                                                           AX3
                                                                                                            R- 1

                                                                                             .2

                                                  SR-4
                                                                   12%

                                                                                                            9bamoo &Lear. see Leffides

                                                                13                         old Saybrook Breakwater

                                                               Nov Novas larbor

                                                  ItUloport 14rbor                REPEATER STATIONS IN ASERT SYSTEM

                                                                              SR-1    Mohawk Mountain Observation Tower
                                                                              SR-4    Oxford Fire Tower
                                Stamford lowbor                               SR-8    Jobn Tom Mountain
                                                                              .SR-14  Fire Tower on Ekouk Hill
                                                                              AR-1    Fire Department Radio Tower, Plain Nil
                                                                              AR-2    DOT Antenna site. Mt. Parnassus
                                   C3 Tide/Storm Gage Station                 AR-3    DOT Tower, Meriden Road
                                      Radio Path (not field checked)              A   Base Station

                                               FIGURE 5.3: Radio Telemetry Network

                                                       5-13

                 ALTERNAT13LF DMIGNS

                     Maximum Use of Existinv'    Instrumentation: Alternative 1-a- One alternati
                                                                                                    ive
                 maximizes the use of existing   instrumentation at the four recording tide stations
                 which would be incorporated     in the system. Presentlyp these stations 'employ
                 either bubbler gages or float gages. These same' gages could continue to be
                 used by installing a mechanical drive to interface the gage with an ASERT
                 compatible transmitter. The new gage station at New Haven Harbor and the
                 two roving gages would employ a pressure transducer gage as recommended above.
                 These gages would require an analog connector to an ASERT compatible transmitter
                 (176).

                    Equipment   costs for  existing stations  are estimated at   approximately $5tOOO
                 each, including interface units, transmitter, back-up          power supply, cable
                 and antenna, and meteorological sensors with conditioning electronics and
                 cable. Costs for new- stations (permanent and roving7) are estimated at approx-
                 imately $6,500 each,, including the above equipment plus a pressure gage, gage
                 mounting, and    underwater cable. Total equipment cost       for the 5 p   ermanent
                 and 2 roving gage stations in this option is approximately $39,500. Including
                 software costs, the total equipment 'cost, of this option is approximately $47,500.
                 Installation costs would be approximately   $39500.

                    Upgraded Instmmentatione Alterniltive 1-b A second alternative is to replace
                 the existing water level sensors with new pressure transducers8. Each station
                 would be   equivalent  to the new stations described in Alternative 1-a, with
                 equipment costs of about $6,500/ station, and a total equipment cost. for the
                 seven stations of about $45,500.        Including software, total equipment cost

                  7Does not include costs of instrument housing for roving stations, since the
                 location of these gage stations has not been selected and the.-possible availability
                 of existing instrument housing is unknown.
                  8 Replacement of existing equipment will require approvals and coordination
                 with the agencies that own the tide stations.. Agreements will have to be
                 reached with NOS for the New London and Bridgeport gages, COE and USGS for -
                 the Stamford gage, and USGS for the gage at Old Saybrook. Agreements will
                 also have to be reached with these same agencies for adding interfaces to
                 the existing gages, and adding the additional meteorological and transmitting
                 equipment.

                                                     5-14

               of this   alternative   is about $53,500.     Installation is estimated at about
               $5,000.

               L=       Tide, Storm Surge and Wave Measurements& ASERT Compatiblg
               GENERAL NETWORK DIECRIPTIO The addition of wave measurements requires modifi-
               cations to gag e station locations, sampling sensors, field station data processing,
               data transmission, and data processing. This section describes these changes
               as they would apply to, an ASERT compatible network.

                  Station Lo cations If wave measurements are added to the monitoring network,
               a new station must be added at Stamford Harbor (the exis     ting station in Stamford
               Harbor would 'be dropped from the network)9, and the sensor at the Old Saybrook
               station relocated.    The new -Stamford station would be located on the West
               Breakwater at the entrance to Stamford Harbor. Installation would be similar
               to the New Haven station, utilizing an existing Coast Guard lighthouse tower
               and mounting a pressure sensor on the ocean.bottom off the south (open water)
               side of the breakwater. (182,183)        The Old Saybrook station presently has
               a bubbler gage located on the protected side of the breakwater (30). The
               bubbler gage would be replaced10 with a pressure sensor and relocated to the
               open water side of the breakwater.         Figure 5.4 shows the location of this
               monitoring network.

                  Instrumentation Collection of wave data requires a        higher quality   pressure
               sensor than is needed for tide and storm surge measurements. A top-of-tbe-
               line strain gage pressure sensor or quartz pressure         sensor  is recommended.
               Wave data also. requires more complex. conditioning        electronics at the field
               station in   order to handle the burst samplings required for wave spectral
               data in addition to averaged data for stillwater levels.

                  To obtain the most complete i      nformation, wave directional spectra could
               also be measured. This would require the installation of wave gage arrays

                9
                 The existing station at    the Hurricane Barrier in Stamford Harbor could also
               be included in the network, but two stations in the same area are not necessary,
               and for purposes of network design and cost estimating it is not included.
                1OThe bubbler g age could be kept in operation if desired.

                                                                      -----------

                                                        Ir

                                          V'.

                    \6,                                                              Thamc
                                                                                    at N 6
                                                                   Old Saybrook
                                              New Haven
                                                        Harbo.r
                                                                    Breakwater

                              Bridgeport Harbor

                                                      L'Vaj
                 Stamford Harbor

                FIGURE 5.4% Locations of   Permanent Gage Stations for Tide, Storm S
                             and Wave Measurements

                                                        5-16

                (three or four gages at one station) or      wave gages with built-in wave direction
                measurement instrumentation. Because         ASERT poses limitations on wave data,
                the designs for an ASERT compatible wave network assumes            wave gages without
                directional capability.

                   Data Transmission and P                  The ASERT system was not         designed to
                handle wave information, and there are no existing installations using ASERT/ALERT
                type systems that collect wave data.          Nonetheless, it would be possible to
                develop a wave monitoring network utilizing the ASERT system, providing certain
                compromises in data and/or system quality can be tolerated.

                   The principal limitation of the. ASERT system to collecting wave data is
                the event reporting feature. ASERT/ALERT includes both event and timed reporting.
                Relative humidity, temperature, and soil moisture are transmitted on a timed
                basis (currently set at once every six hours). Each relative humidity, tempera-
                ture, and , soil moisture sensor at all field stations is set to transmit at
                a predetermined time, with each sensor transmitting at a different time to
                avoid signal interference and loss of data. (67)

                   Precipitation,    streamflow, and wind       speed and direction are transmitted
                on an event basis   (data transmitted only when a reading differs from a previous
                reading by a predetermined value). Because event reported data is transmitted
                at random times, signal interference may occur at either a repeater station
                or a base station.        Statistically, the short transmission time (about 1/4
                second) for each signal will result in, very few lost units of data, even for
                a network with many more sensors that ASERT/ALERT presently has. During storm
                events, with strong winds, heavy precipitation and rapid increases in streamflow,
                the number of data units lost due to signal interference may significantly
                increase.   However, signal coding 'and data processing procedures permit all
                signals (received or. lost) to be accumulated. Therefore,' total precipitation
                and stream, level increase can still be determined, as well as the rate of
                occurrence, and little or no, loss of significant data occurs.                  Similarly,
                tide and storm surge, data would. be accumulated, and loss of some              individual
                data units would not be critical.

                                                        5-17

                     Wave data presents at least three serious      conflicts, with the ASERT system.
                  First, any loss of wave spectral data would mean total loss of useful data
                  for that sample. Each sample of wave data         is largely independent of others
                  and is not accumulated like rainfall or even      storm surge. Second, wave data
                  requires a much longer transmission A im e than   other information on the system.
                  Third, wave data is normally not collected with 'great frequency (usually only
                  once every 3 to 6 hours), but during storm periods, an increase in frequency
                  of measurement is desirable. ASERT has only one-way communications, making
                  a change in sampling frequency impossible (except by changing at. the field
                  site, which is not very practicable).

                     Any  design that  adds wave measurements to the ASERT system will          require
                  a new  software module for the Enhanced ALERT software. Costs for             writing
                  this wave module would varydepending on the type of wave data received at
                  the base station and the form of display desired. For cost estimating purposes,
                  a software development cost of $25,000 is assumed.

                  ALIERNATIVE IIESIGNS

                     Simplified wave data* Alternative 2-a     One way to utilize the ASERT system
                  is,to collect simplified wave data. Conditioning electronics' at gage stations
                  could be programmed    to sample waves in a different manner than-is normally
                  done.' For example, the averag  e wave  height and wave period over a   given period
                  of time could be 'mathematically determined.       Transmission of this simplified
                  data would I require about the same    time (less  than 1/4 second) as 'other' data
                  transmissions on the ASERT/ALERT       system, reducing chances of interference.
                  Loss of a data,unit would still mean total loss of wave information for that
                  time period.

                     Costs for this alternative are estimated at about $10,000/station for a
                  total equipment cost of about $70,000.   Including sof tware costs, this alternative
                  would total-about $95,000. Installation costs are estimated at about $5,000.

                     Field station                of spectral  MInve data., Alterl]ative 2-h Another
                  procedure (Alternative 2-b.1) for including wave data on the ASERT* system
                  would be to collect the     full' wave spectra data, but instead of transmitting

                                                    5-18

               the full data stream, the data could be processed at the field site. Transmital
               of processed data would require a much shorter transmission time, reducing
               chances of interference. To verify accuracy of the data, some portion (1/8tb)
               of the raw data should also be transmitted. Because the data would be processed
               at the field station, raw data would not be arcbived for research purpose.
               Data transmissions   experiencing interference would still be completely lost,
               and the transmission time would be longer than otberr?ASERT/ALERT transmissions.

                  Costs for this alternative would be higher than the previous alternatives
               due to the more sophisticated electronics required. An estimate of $12,000/station
               is used for a total equipment cost of about $85,000. Including software develop-
               ment, this alternative would cost about $110,000.          Installation costs are
               estimated at about $59000.

                  A variation on this procedure (Alternative 2-b.2.) would be to collect full
               wave spectral data, transmit only significant wave height and significant
               wave period (along with stillwater level), and store wave spectral data on
               Pagnetic tape at. the gage station. Several wave measurement systems permit
               data storage on magnetic tape, and customizing of the conditioning electronics
               should permit tape storage as well as radio transmission of stillwater level
               and wave height and period. No information was received on a wave gage collec-
               tion/storage/transmission unit that performs according to this description,
               but customizing of existing units should make this configuration possible.
               Storage of wave spectral data on magnetic tape for periodic retrieval would
               not adversely affect the flood monitoring network. Spectral data are primarily
               useful for research and design purposes, which do not normally require real-
               time data.

                  Costs for this alternative are estimated at about $15,000/station, for
               a total equipment cost of about $105,000. Software development should be
               less since only water level, wave height and wave period will be provided,
               and is estimated at $8,000, for a total cost of $113,000.. Installation costs
               would also be about $5,000.

                  FreQuent Sampling Rate/Multiple Trg              Alternative 2-c Still another
               procedure to enable. wave data to be included on the ASERT system is to increase

                                                      5-19

                 the sampling rate  or to provide multiple transmissions of the same wave'sample.
                 Either procedure to reduce the consequences of lost data units creates additional
                 problems by- providing unnecessary data for processing and/or archiving, and
                 increasing the number of data transmissions, thereby increasing the, overall
                 rate of interference.

                    Costs should be about the same as Alternative 2-b.1: $85,000 for equipment
                 and $25,000 f6r software for a        total cost of $110,000.    Installation costs
                 would be about $@,000.

                         Tide, Storm Surge and Waye Measurements*     Two'Networks

                    Wave data is highly.. desirable for both flood    warning and other purposes,
                 but most alternatives for including wa   ve measurements on the ASERT -system
                 require substantial compromises in either the quality of the wave data or
                 the overall   reliability of the ASERT system. Therefore, another       . alternative,
                 'was explored that would provide wave data and still be partially compatible
                 with the :ASERT' system. This' alternative requires two separate monitoring
                 networks: an ASERT compatible tide and storm surge network, and a wave network.
                 Three options are presented.

                 GENERAL NETWORK DESCRIPTIO Each option would include an ASERT compatible
                 tide and storm surge network consisting of only two stations: New London
                 and Bridgeport.    If these two stations are equipped with pressure sensors,
                 the cost for this portion of each option would be about $13,000, plus $9,000
                 for software development, for a subtotal of $21,000. The wave network in
                 each option would include permanent stations at Stamford Harbor Breakwater,
                 New Haven Harbor Breakwater, and Old Saybrook Breakwater, and two roving stations.

                 ALTERNATIVR DESI*GNS

                    One-Way Communications System* Alternative 3-a A separate one-way communi-
                 cations system could be   established which would include new repeater stations
                 (possibly at the same 'sites as ASERT repeaters), a new decoder/receiver unit
                 at the base station, and additional radio frequencies. This separate network
                 would enable transmission of   wave' data timed to avoid interference among the

                                                      5-20

                different gage stations.

                   Each   wave gage station, including pressure sensors with all electronic
                conditioning to collect water level and wave data, transmitter, antenna, cables,
                meteorological sensors and backup power supply could range from about $12,000
                to more than    $30,000 depending upon the specific equipment and whether or
                not directional wave gages are selected.          Repeaters for this system could
                range between $7,000 and $11,000, and a receive   r/decoder would be approximately
                $6,000. For comparative purposes (assuming three repeaters are      'needed), assume
                a cost of $130,000 for non-directional wave stations and $180,000 for directional
                wave stations (directional gages; not arrays).        The total for both networks
                (surge and wave) would range from about $150,000 to $200,000.              Installation
                costs are estimated at about $8,000.

                   Two-Way Communicationa System., Alternative 3-b Installation of a two-way
                communications system would permit operators at the central receiving station
                to reprogram wave gages to increase or decrease sampling frequen       cy as desired.
                This would permit maximum utilization of the wave network during storms.
                Costs for this wave network could range from about $250,000 for non-directional
                wave stations to    .$300,,000 for wave directional stations (directional gages;
                not arrays).    The total for both networks would range from about $270,000
                to $3209000.    Installations costs are estimated at about $10,000.        The total
                for both networks could be as much as $340,000.

                   Linkage  to SIO Wave Monitoring Systemo Alternative 3-c Another alternative
                is for the  State of Connecticut not to process wave data itself, but to tie
                into the SIO wave data collection network. To establish the linkage with
                SIO,, wave data would be transmitted over a separate communications system
                (as with Alternatives 3-a and 3-b) to the Hartford base station.              Received
                data would be routed to a microcomputer (or other microprocessor unit with
                buffer memory sufficent to temporarily store data from all wave stations)
                which is link ed by ,modem to a dedicated phone line. At preset times, the
                SIO computer would initiate a, telephone call to the Hartford base station
                to receive the most recent data from each wave station and initiate data
                processing.    Data on significant wave height, significant wave period and
                wave spectra would be available to Connecticut users in a few minutes by calling

                                                            5-21

                  the SIO   computer via a modem connection. Processed data              would be published
                  monthly   by SIO, and additional data processing performed and published annually
                  (See Figures 5.5 and 5.6).

                      Although    it was not specifically investigated, it is probably feasible
                  to use the existing ASERT computer and a new module to the enhanced ALERT
                  software to store data for SIO processing.            Presumably, the software module
                  could also extract water level, significant         wave height and significant wave
                  period data for immediate input into the ASERT system, while passing spectral
                  data on to the SIO computer for processing. Equipment costs would be about
                  the same as the two previous alternatives, depending upon choice of one-way
                  or two-way communications, directional wave gages and other                  variations in
                  equipment type and quality:
                  - One-way communications,. non-directional wave stations:          $130,000
                  - One-way communications, directional wave stations:
                  - Two-way communications, noir-directional wave stations:          $250,000
                  - Two-way      communications, directional wave stations:          $300,000
                  Software development costs are assumed to be about $25,000, and installation
                  costs would range from about $8,000 to $10,000 depending upon whether one-way
                  or two-way communications Yere used.

                      The principal advantage to joining          the SIO network is the cost savings
                  from having all data processing and archiving handled by SIO (and not having
                  to develop -specialized software, if that       option is chosen). The annual savings
                  in data processing and archiving           could be substantial.      Another advantage
                  to the SIO network is that wave data could be easily input to the NWS AFOS
                  system for   distribution to the New York WSFO, Bridgeport and Hartford WSOs,
                  and other appropriate NWS offices.

                     There are, however, s     ome distinct disadvantages to utilizing.the. SIO network.
                  Data must be input and @retrieved from the SIO computer system through telephone
                  lines and modem links, making it somewhat more susceptible to disruption during
                  storms (both California and Connecticut storms) than a radio based system.
                  A major. limitation of the SIO system is that water level (tide and storm surge)
                  is not routinely process,e Id.and reported by the system (ASERT software enhancements
                  may overcome this limitation). Other disadvantages include dependence upon
                  another organization for maintaining       a significant portion of the total network;

                                                                                                                                                                      5-22

                                                                                                                                                                                                                                                                                                                                                                    Fr

                                                                              WAVE ENERGY SPECTRA DEC 1985
                                                                                                                                              -                                                 IMPEPIAL REACH ^MAY. DIRECTION
                                                                                                                                                                                                DEC 11POS
                                                                                                                                                                                                                                                         APPOULAR DISTRIOUTION IN PERIOD SAMS
                                                                                                                                                                                                                                                                      MOGLES IN DEGREES)
                                                                                                                                                                                                PST Sze- AM               Tur. SKY                           S-0      PERIOD Ll"ITS ISECR)
                                                                                                                                                                                                DATfT"W        (CEO)      (CrL 80)               22-SN       10-16    so-34      1@&2      12-10      10-9      9@.

                                                                                                                                                                                                    0=1        93.1       -2$7.7                 011.1       WX 5     "-&        ft.0      ".3        ".5       94,11      87.6
                                                             3                                                                                                                                           1                                       " 6         91                          A 94.6       96-1      97.7       91.0
                                                                                                                                                                                                    3401       93.        -9&.;                  Tl@     ,   94
                                                                                                                                                                                                                          &                                           @ *2 9Z 1  92 :      95 7       93 &      9313       94@ 9
                                                                                                                                                                                                                          7
                                                                                                                                                                                                1   2001       96.0                 7            97.0        94.3     94.0       IP3:      919        9Z 7      96, 2      91.0
                                                                                                                                                                                                2   0201       :13-0      -IS-:                  77.9        92.3     92.9       90.6      63. 6      93.7      W.2        00.6
                                                                                                                                                                                                                          4'                     96.6        96.11    92-     5  91 2      09.7       9Z 7      93.2       M 2
                                                                                                                                                                                                                          -29 2                          3            291     a  78:3      94, -P     97.2      S& 4       92     3
                                                                                                                                                                                                                                                 90.
                                                                                                                                                                                                    140,                                         93'
                                                                                                                                                                                                2   ..         as. 1P     @l        4                    3   :1       9W 2       94.3      93.6       90.0      86:4       2@ I
                                                                                                                                                                                                3   0201       93.0       -437.1                 92.2        97.0     ft.6       91.1      W.5        94.6      811.2      37 2
                                                                                                                                                                                                a   000        ft. 9      @113. a                09      1   93       394.0      91.6      94.2       ' '       67 4       " '
                                                             21                                                                                                                                 a   1401       V2. 7      -*20@ I                SIP'2       93:2     M 4        93.7      9Z 5       ql. .     11:2       93.4
                                                                                                                                                                                                3   200t       @M 5       -40Z 9                 03-9        87.2     96.7       90-2      "-         Y03.3     91.4       91.9
                                                                                                                                                                                                4   0201       92.9       -300. 0                04,11       9& 4     'M 2       90. :     90- :      92 29     93. :      97.9
                                                                                                                                                                                                A   OWS        T&         -202-                  03'     2   09F 7            6  -M        91         92-       90         87 4
                                                                                                                                                                                                                                                         3                               3            0      A
                                                    'A                                                                                                                                          4   1401       -03.       :279.17                74-,        9z 7     9z         93.       94:        93..      ::: 3      93@ q
                                                                                                                                                                                                4   2001       94.        15Z       ,            99L         9Z &     ".7        92-4      90.9       102.                 392.6
                                                                                                                                                                                                    Mot                   -194      7            66.0        %.5      69.3       92.4      Bit- 6     80. 7     -Vt
                                                                                                                                                                                                    owl        -M-2                                                   a92.50     92 7      94..       -Ft. ?    so:
                                                                                                                                                                                                               90 2       -91                    04.6        96                                                            .91.
                                                                                                                                                                                                3   1401       9Z 3       -139@                  90.9        94:2     92.        94:1      92.3       93.6      9.%5       90 0
                                                                                                                                                                                                3   2004       ".3        -2*3.     3            89.6        96.3     ".0        96-2      91.2       92-    0  94.        394.1
                                                                                                                                                                                                &   0201       ".3        -2". 4                 92-5        94@ 9    96.0       94-4      99.6       92. q     " 3        ".1
                                                                                                                                                                                                S   W01        94.        1-240.2                85-3        92 3     93.2       93.4      ".3        9Z &      95:2       96-    2
                                                                                                                                                                                                    1401       92 6       -262-7                 -.7         9.       94.4       92-1      92-6       "-b       94.4       95 3
                                                                                                                                                                                                    2"1        93.9       -177.4                 95.6        93::     93.3       ".3       93.8       91.9      95@ 3      90.7
                                                                                                                                                                                                7   0201       93.3.      -126.3                 90 3        ".3      92.1       09.7      94.5       %Z 6      q3 7       95.2
                                                                                                                                                                                                7   0001       "-1        -170.0                 91:6        95.0     9Z A       93,7      IM         S92    7  92         `3
                                                                                                                                                                                                7   1401       93.7       -21Z 0                 110.7       93.9     92.6       96,4      92.        392:   ,  -.:        92-,
                                                                                                                                                                                                7   2001       93.2       -226@     7            72.3        ".A      "@2        93@3      94-3       91.6      91-7       90.4
                                                                                                                                                                                                9   0263       "-2        -= 7                   113.0       "-&      "       '  M 3       94.0       W.3       ".7        405@2
                                                                                                                                                                                                    0001       " 3,       -1:3                   97 4        99 6     q3: 2      94.6      9312       93     -1 913 7      100@ 3
                                                                                                                                                                                                               95:        -2.1 3                 917         09. :    93                                     2  ":9 " !
                                                                   20                            16                  ;2         8                       4                                       9   2001       95.2       -260.4                 100.8       94@      .:2,       9,2. 9*   9"4.- 93   9"4: .    99. a q.:
                                                                                                 .PERIOD SEC.                                                                                   q   0203       96.7       -211.2                 92.8        93.0     93.9       94.9      @M &       97.3      99.2       96.6
                                                                              IMPERIAL           BEACH               ARRAY.ENERGY

                                                             IMFRIAL 3EAC ARRAI.ENERGY                                                                                                                                              WAVE DIRECTION IN PERIOD BANDS
                                                             DEC              '983
                                                                                                                                                                                                                                                                                                                           TO

                                                                                     PERSISTENCE

                                                                              LMVE MUCHY 19 @ METERS OR LESS
                                                                 CONSECUTIVE DAYS 41 an WRE) SIGNIFIeWr

                                                                              METERS             DAYS
                                                                              0 5                1.
                                                                              1:0                1.      1.          T.    5.
                                                                                                 1,      3.          10.   7.
                                                                              2                  2       21L
                                                                              2.5                31:
                                                                              3.0                2,
                                                                              3.S                2.:
                                                                              4.0                21.
                                                                              4                  2

                                                             MAPIMM DAILY SIGNIFICAwr MAW Halawr Fw- nee                                      I"M                                                        Q

                                                             DATE I DEC)                         I       a           3          4         3             A           7
                                                             sic. Kr im 1            1.6         Ole                 z #   A.&       S-6         1.7         1.9

                                                             DATE ( WC I                         a       P           10         A 1                     33          94
                                                             SIG. Wr (M 3            1.9         L7                  1-4   0. V      1.3         1.3         1.2

                                                             DATE d WC                           is      16          17         is       19             20          as
                                                             910. HT (PL             0.9         0.3                 0-&   0@ 9      0. V        9.4         0.7

                                                             DATE C 0=1                          22      zz          24-,       23       26             21'
                                                             Ole- MY (M )            1.0         1.1                 1.6   1.0       0.9         0.4         0.9                                               1          22-14 is-Is                                         ID-11 6-6 a--
                                                             DATE C DEC)                         20      30          31                                                                                                                          PERIOD SEC.
                                                             ago. HT (PL P           0.9         0.9                 1.1                                                                                                            IMPERIAL BEACH ARRAY.OIRECTION

                                                               SOURCE: U.S. Army Corps of Engineerst and California                                                                                                                        Department of Boating
                                                                                                 and waterways. 1986. Coastal Data information Program,, Monthly
                                                                                                 Report, December 1985. Monthly summary Report No. 119.

                                                             F    IGURE                          5.5: Examples Gf Monthly Wave Data; West Coast Wave
                                                                                                                     Measurement Network

                                                                                      5-23

                                                                                                                     IMPERIRL BERCH ARRRY. DIRECTION
                                  IMPERIAL BEACH       JAN-DEC 1984                                                           ANNURL ORTR 1584

                                                                                                                                      BSC

                                                                                                                                              W"WRLY TRWFW

                                                                                                                                              SWTWMY TRARPM

                                                      I%p k.

                                      JOINT DISTRIBUTION OF     HEIGHT & PERIOD

                                                                                                                                              MKnfMY TRANSPOU

                                           IMPERIRL BEFICH RRRRY. DIRECTION
                                                          ZTA 1384

                                                                                                                                              Onnfmy rmnpw

                                 d                                                                TMPERIAL BEACH JAN-DEC 1984

                                                                                                   2

                                                                                                   0
                                                     1167 11@ UL 0.1aw

                                                                                                                        4.
                                                                          to       a
                                                                                                to 0
                                                                                                            JAN      FEB'     MAR'     APR      MAY      JUN

                                                                                                   2

                                                   WWI

                                                                                                   2
                                                             'we         ai        U01a
                                                                                                64
                                                                                                   0.
                                                                                                            JUL      AUG      SEP OCT           NOV     DEC

                                                                                                     SEASONAL SIGNIFICANT HEIGHTS OF SEA & SWELL

                         SOURCE: Seymour, R.J., et. al. 1985. Coastal Data information Program,
                                       Ninth Annual Report, January                1984 through December 19,84. Scripps
                                       institute of Oceanography, La Jolla, CA.

                                FIGURE 5.6:. Examples of                           Yearly Wave Data; West Coast Wave
                                                          Measurement              Network

                                                    5-24

               access to the data by telephone, including associated telephone charges; and
               uncertainty over-the costs of participating in the network1l.

                       Tide, Storm Surge and Wave Measurements: Independent from
                       ASERT* Alternative

                  The  last alternative presented is for a monitoring network that is entirely
               independent of ASERT and provides a maximum of information. T         his network
               would   maintain the same station locations as described for alternatives 2,
               3, and  41 2, and use a two-way communications system.' Instead of using the
               ASERT   base station. computer and software, a separate data processing system
               would   be installed, at the base station.    Equipment costs for this network
               are estimated at about $425,000, and installation costs at about $15,000.

                       IMPLEMENTA110N OF MONITORING NETWORK

                       Estahlisbment of Gage Stations
                  Depending upon the monitoring network design chosen, the State has several
               options and some limitations regarding the sequence and timing of implementation.
               Because of differences in equipment at existing systems and differences in
               timing of converting to new equipment, the entire monitoring network probably
               cannot be installed with its final configuration immediately. The installation
               may need to proceed over a period of several years in order to coordinate
               actions and establish interagency agreements with several federal agencies.
               Some temporary , installations may be needed.      Following are some suggested

                11Presently, California is the only state making a financial contribution to
               the SIO network. In recent years California has been contributing $50,000/year
               and is expected to increase its contribution to $100,000/ year in FY 87. (135)
               Certainly, Connecticut would not need to' contribute this large an amount,
               but an acceptable amount would have to be worked out between the State and
               SIO (and probably the COE and State of California).
                12The NOS stations at New London and Bridgeport could be replaced with stations
               in the same areas, but in open water to obtain wave measurements along the
               shore rather than in the Thames River estuary and Bridgeport Harbor. Locations
               for these new. stations have not been identified, and no cost estimates for
               this alternative were developed.

                                                         5-25

                  State actions.

                          Dev elop a cooperative agreement with the NOS to have the New London
                          station included in the early group of next generation tide gages
                          to be installed. Assuming that NOS proceeds with a primary acoustic
                          gage and a backup pressure gagel3, arrangements should be made to
                          add the pressure gage to the Connecticut flood monitoring             network.

                  (2)     Develop a cooperative agreement with both NOS and NWS to use          the NOS
                          g age at -Bridgeport Harbor on a temporary basis until NOS upgrades
                          this station with new gagesl4,

                  (3)     Develop an agreement with the Coast Guard for continued         use of a gage
                          station at the Sayboook Breakwater and new gage stations at the New
                          Haven and Stamford Breakwaters (assuming wave stations are selected).

                  (4)     Modify the existing agreement with USGS, for operation and maintenance
                          of the gage station at Old Saybrook to provide for upgrading the sensor
                          (tide/surge or tide/surge/wave), if that option is chosen, as well
                          as maintaining the new wave gage stations at New Haven and Stamford.

                  (5)     If a tide/storm surge only alternative is selected, develop an agreement
                          with the COE and USGS for upgrade and/or use of a gage station at
                          the Stamford Hurricane Barrier.

                  (6)     Hold discussions with coastal communities, DEP Water Compliance Unit,
                          UCONN researchers, and Connecticut DOT, Bureau of Waterways to identify
                          locations that would receive high priority for          initial placement of
                          the two roving gages.       Proceed with deployment     of the two "roving"
                          gages.

                          Getting Information to Users

                     Getting- tide, storm surge, wave and meteorological, data to essential users
                  is just a  s important as collecting the information.           For efficient use of
                  the monitoring networkq three user groups need to receive information in real-
                    or near real-time: State emergency officials (OCP and CSP), NWS, and officials
                  of c oastal municipalities.     Real-time information would be highly desirable
                  for at least two additional groups: Coast Guard and -various navigation interests,

                   13
                     There appears to be some uncertainty as to whether NOS will actually install
                  a backup pressure. gage.      If not, the Connecticut network could utilize. the
                  acoustic gage.
                  141t may be nee   essary or desi rable to have the Connecticut monitoring network
                  link directly with the NWS   telemetry unit (HANDAR Model 540A).

                                                      5--26

                own base station and associated software, just as communities are presently
                doing for the ALERT system.

                   In order for communities to purchase their own base station, costs must
                be reasonable and the information must be produced in a format that is easy
                to understand and use. If a double- network (tide/storm surge network and
                wave network) requiring two different communications systems is selected by
                the State, equipment costs for municipalities will increase; antenna(s) and
                receiver(s) must be capable of receiving multiple radio frequencies.

                NAVIGAT  ION INTERESTS AND OTHER USE          If tide, storm surge and wave data are
                easily available and reliable, harbor pilots and others involved in shipping
                could benefit from real-time data from the coastal monitoring network. Navigation
                users could access the information in several ways:
                (1)     Installation of 'a base station at offices' of the different harbor
                        pilots associations, marinas, etc. Harbor pilots on ships could contact
                        the association office to obtain current information on water levels
                        and wave heights.

                (2)     Use of a remote terminal (modem with printout or display) at the pilots
                        offices, marinas -and other locations to access data from the Hartford
                        base station  by telephone, and relay to shipboard users. If the Hartford
                        base station were equipped with a voice synthesizer, information could
                        be accessed by telephone without need for a remote terminal.

                (3)     In the near    future products should be available to permit shipboard
                        use of a remote terminal (modem with printout or display) or portable
                        computer with modem to access information from the Hartford base station
                        via cellular telephone.       Cellular telephone coverage now includes
                        the entire Connecticut coast except the Groton/Stonington area, which
                        should be added during 1986. (180)

                        MAINTENANCE PROGRA

                   Constant or periodic exposure of equipment to saltwater or saltwater spray
                promotes rapid corrosion. Equipment can degrade rapidly under these conditions.
                As a consequence, the coastal flood monitoring network must be maintained
                with care and diligence.

                                                           5-27

                      There are many possibilities for weak links in marine systems, and care
                  must be taken to eliminate these weak links. For example, lack of care in
                  mating cables, or in selection of nuts, bolts, etc., can result in extensive
                  repair costs.      Attention to such detail during design and installation can
                  minimize the maintenance requirements of the system.' Thus, in accepting any
                  components related to the coastal monitoring network, emphasis must be placed
                  on durability, ability to withstand large -waves and high water, and resistance
                  to corrosion. ' Altbough a -tentative maintenance schedule is presented for
                  consideration with this report, final maintenance procedures will be a function
                  of product reliability, construction techniques, and care during installation.

                            Maintenance J!rogram

                      A complete and active maintenance program needs to be developed and rigorously
                  adhered to. It is recommended that one individual be assigned responsibility
                  for the maintenance program. This will, pr.ov       ide continuity in the maintenance
                  program, and build familiarity with the system. Similarly, it is recommended
                  that the individual(s) assigned to the maintenance team(s) be given long-term
                  assignments or contracts.

                      A* tr ouble-sbooting sequence should      be established by either the State or
                  a contractor, to facilitate rapid isolation of any system'modules causing
                  a problem. For example, a procedure should be mapped that will allow discrimina-
                  tion  between problems caused at a gaging station, versus those-caused at a
                  repeater,   versus those caused at a base station. Office         tests may help isolate
                  the module at a remote site which is in need of repair, thereby minimizing
                  field testing at remote sites.         This type of discrimination is necessary to
                  reduce the time required of field crews, training of field crews in the electronic,
                  communications and mechanical aspects of the system,             -and to reduce system
                  down time. Spare modules can be purchased to allow rapi         d correction of problems,
                  with the suspect modules later replaced or repaired.

                      Inspection teams s   hould accomplish minor      repairs Irepairs   taking less than
                  one hour, not requiring major pieces of equipment, nor           requiring special 'skills)
                  during   regular inspections. Each team should have with          them  a tool and spare*
                  parts box with essential equipment needed to accomplish minor          repairs.

                                                     5-28

               especially shippers and harbor pilots.

               STATE EMERGENCY OFFICIALS The ASERT base station is presently located                in
               the offices of the DEP      Water Resources Unit in the State Office Building.
               The two State   Warning Points, OCP and CSP, do not presently have direct access
               to the ASERT system. To ensure proper coordination among all State emergency
               officials, local officials and NWS offices during times of potential flooding,
               it is important that both OCP and CSP have direct access to real-time data
               on coastal (and riverine) flooding. The radio signals which reach the State
               Office Building should also reach both OCP and CSP, which are in the same
               vicinity.   Therefore, it is suggested that both OCP and CSP acquire their
               own base stations.

               NATIONAL WEATHER SERVICE The essential NWS stations are the New York WSFO
               and the Bridgeport and Hartford WSOs. One option would be for each of these
               offices to install their own base      station and receive data directly by radio
               transmission, just as the NERFC office in Bloomfield now does. However, it
               may not be possible for the New York WSFO to receive ASERT radio signals from
               Connecticut due to interference from many other more powerful signals in New
               York City (185). It would also be highly desirable for the National Meteorological
               Center in Silver Springs, MD and the National Hurricane Center in Coral Gables,
               FL to also receive real-time data from the Connecticut coastal monitoring
               network. To do so, the information needs to be added to the NWS AFOS system,
               which all of the concerned NWS offices have. The AFOS system i          s apparently
               being used   to capacity, and specific authorization must be obtained to input
               additional information to the system.       It is also not clear just bow ASERT
               data would be entered into AFOS. (32,36,68,185,186) Clearly, some automated
               procedure is needed. The most logical entry point appears to be the NERFC
               in Bloomfield or . the Hartford WSO at Bradley Field, Windsor Locks. The. State
               and NWS need to pursue the autborization.and procedures for getting ASERT
               data into the NWS AFOS system.

               MUNICIPAL OFFTCIALS Municipal officials who wish to use the coastal monitoring
               network to obtain detailed, geographic specific information on actual storm
               surge and wave levels must also have direct access to the ASERT system. The
               most  efficient, procedure appears to be for local communities to purchase their

                                                        5-29

                     For all inspections procedures described below, a written report should
                  be prepared immediately by the maintenance team and submitted to the program
                  manager, including any repairs or maintenance performed by the team and any
                  problems noted that require further attention. The program manager should
                  evaluate these reports and arrange for immediate r        epair or replacement of
                  equipment, as needed.

                          Maintenaneg Schedule

                     A matrix of maintenance procedures is presented as Table 5.2.. Each aspect
                  of the four maintenance procedures is discussed below.'

                  MAINT            WCEDURE1 All data should be monitored carefully by the Program
                  Manager to detect any hardw are- related problems. Any problems identified
                  can be evaluated more carefully during monthly on-site inspections*'

                     All above-water portions of the system should be         inspected visually each
                  month. All hardware should be. inspected for structural damage and corrosion.
                  Connectors and mating parts should be verified for stability, and clamping
                  hardware should be checked for tightness and integrity. Corrosion of metal
                  materials must be identified and arrested early to avoid catastrophic failures.
                  If any damage or decay is noted,    prompt action should be, taken to avoid later
                  failures that could result in extensive down time.         Records should be kept
                  to document a  history of failures and corroding parts.

                     The remote   backup power supply    should be tested at this time.       Magnitude
                  of charge and  integrity  of charging circuitry should be  ev aluated.  If necessary,
                  the battery can be cycled during this- inspection.

                     Clocks should be r    eset and synchronized,     using a portable   master clock
                  or radio re ceiver.' A log of clock errors should be kept at'each station to
                  permit a history of clock behavior.'     Excessive drift or decay of the accuracy
                  of the time base can be used to indicate need for' clock repla   .cement or modifica-
                  tion.

                                                    5-30
                  The inspection sho'
                                        uld be fairly rapid, taking approximately 1.0 to 1.5
               hours if no defects are detected.     Repairs of any extensive nature might be
               better made during a return 'visit, following approval by the Program Manager.

               MAINTEN             CFDURF 9 Maintenance procedure 2 is a complete visual check
               and servicing of all underwater components.      This maintenance must be done
               by diving teams familiar with the operation, unless some deployment scheme
               is devised whereby - divers are not required.     Divers can initiate inspections
               from the shore or a small boat,  traveling between sites over land.

                  Crews making these checks of underwater components must be familiar with
               corrosion problems and common modes of underwater failures.         All connectors,
               penetrators, splices and other fastenings and joints should be inspected.
               Marine fouling should be removed mechanically, and anti-biofouling paints
               or coatings should be applied if possible. . All zinc anodes should be replaced,
               and the installation inspected for points of weakness, from both a structural
               and a corrosion standpoint. Cable condition should be assessed, and the strain
               relief examined for security. Any breaks, kinks, or other damage to the cable
               should be noted for proper action.

                  The extent of scouring and undermining of the underwater mounting should
               be determined.    Is the tripod sinking or scouring, or is the pipe becoming
               too exposed?    The pressure sensor should be inspected, noting corrosion or
               pitting.   Pressure sensor ports should be cleaned, and filled with oil (if
               applicable). Any problems in these components should be attended to immediately.

               MAINTENANCE PROCFDURF 3 Maintenance procedure 3 includes a close visual inspection
               of the electronics at the remote site, measurement of output signal strengths,
               and general evaluation of all above-water electronic components. Parts with
               known limited lifetime should be replaced. All antenna fastening and structural
               bracing should be inspected and replaced, if damage or decay is severe.          The
               power backup system  ' should be inspected and serviced completely (water level
               in batteries adjusted, operation of power back-up should be noted when unit
               is powered down, then up, and condi     tion of terminals noted before cleaning
               terminals).

                                                        5-31

                     The weather-tight housing should be inspected        for weak points or decay.
                   All time-keeping circuits should be reset, and         any manufacturer-suggested
                  electronic tests of encoding/decoding and telemetry    products should be   performed
                  at this time.    Signal strength measurements of       telemetry power output and
                  receiver sensitivity should be in accordance with manufacturer specifications.
                  Any problems should be tended to immediately.

                  MAINTENANCE PROCRDURF_4 Maintenance procedure 4 involves complete reconditioning
                  of all underwater components (with the exception of the cable, which should
                  be left buried as long as it is working properly).       It should be accomplished
                  from sea on a diver support vessel that has enough enclosed space to refit
                  hardware onto new tripods inside the vessel as. it travels to the next site.
                  The vessel must have sufficient lifting capability to retrieve and deploy
                  tripods with instruments. To accomplish this reconditioning, all underwater
                  componenets except cable should be retrieved, and replaced by completely recon7
                  ditioned components.     The tripod or mounting pipe should be replaced by a
                  clean, newly conditioned one with anti-fouling added, the strain termination
                  should be replaced, and the pressure sensor calibrated thoroughly.

                     At this time a thorough evaluation of the installation and            maintenance
                  procedures should be made.      Weak points should be identified, and corrected.
                  An evaluation of the long-term potential for decay or corrosion is useful
                  at this point. Should any components,be redesigned to allow better performance
                  or wear? Should any element of the     maintenance procedure be changed?

                          Maintenance Costs

                     The exact maintenance costs will depend upon the specific monitoring network
                  chosen by the State. The cost estimates shown in Tabel 5.3 are only approximw-
                  tions, based on the above maintenance procedures for 7 gage installati            ohs,
                  2 repeaters, and 2 base stations.      Only maintenance which directly concerns
                  the electronic components of the monitoring network is included; it does not
                  include activities necessary to maintain the piers, buildings,or grounds         that
                  are used as a platform for the network.

                                                           5-32

                                              TIME BETWEEN MAINTENANCE

                STATI                              I Month                I Year             5 Years

                All coastal                          MP-1                 MP-2,3               MP 4
                gage stations

                Repeaters                            MP-1                 M P-3

                Receivers                            M P-1                MP-3

                 Note: MP        maintenance procedure, see text.         These procedures are suggested
                to assure high data quality.           They should be updated in consultation with
                the equipment manufacturer and installer.

                                    TABLE 5.2: SAMPLE MAINTENANCE SCHEDULE

                    Maintenance             Coats/Month        Cosjs/Year       Expendable        One-Time
                    Procedure                                                   Parts & Equip     Equipment
                                                                                Per Year
                Surface Maintenance

                       M P-1                  $ Soo              $9,600
                                                                                  $ 500(l)        $5,000(2)
                       MP-3                                      11600

                Underwater Maintenance

                       M P-2                                     3,000                500(1)         -

                       MP-4                                      4,000(3)             600(4)         59000(5)
                                                           (20,000/5 years) (3,000/5   years)

                                TOTALS                          $18,200           $4,000           $10,000

                    W  Miscellaneous spare parts such as clamps, nuts, bolts, paint, etc.
                    (2) Field testing equipment
                    (3) Includes rental of diving vessel
                    (4) Includes replacement parts and      reconditioning   of parts
                    (5) Includes replacement parts such as pressure cases, pressure sensor,
                        etc.

                                    TABLE 5.3: ESTIMATED MAINTENANCE COSTS

                                                        6-1

                                    6,0e CQNCL,USIONS AND RECOMMENDATIONS

                    Evaluation of t   he information presented    in the previous sections resulted
                 in four general conclusions and related recommendtions regarding the most
                 favorable design for a coastal flood monitoring- network and the feasibility
                 of a State forecast and warning system.         Each of these . general conclusions
                 and recommendatins, along with additional specific conclusions and recommendtions
                 are detailed in this secton.

                 Li       EXISTING MONITQRING, FORECAST AND                     SYSTEMS

                 o CONCLUSION # I         The present system of 'collecting data,  preparing forecasts
                 and issuing warnings for coastal storms and flooding is less than optimal.

                          Planned Improvements to Exir2ting   Technology and Programs

                    One   option  available to the State is   to continue 'relying upon the existing
                 coastal  f lood monitoring and warning systems, includi ing improvements to        the
                 existing systems and programs that are already underway or planned.

                    Conclusion 0 la       Planned program changes by several federal agencies
                    should result in.. gradual and limited improvements to the collection of
                    meteorological and oceanographic data and to issuance of coastal flood
                    forecasts and warnings.
                    The most relevant of these planned improvements      are summarized belowl.

                    (1) Hurricane Preparedness- Studigs,,    NWS, FEMA, and the COE             proceed
                    with their program of Hurricane Preparedness Studies, utilizing results
                    from the SLOSH model. Information on projected storm surge heights and
                    areas to be innundated from different categories of storms should be available
                    for the eastern portions of LIS and the Connecticut shore beginning in
                    1987, following completion of storm simulations and 'development of MEOWS
                    for the Narrangans e t t/ Buzzards Bay SLOSH bas   'in. More.detailed delineation
                    of storm surge and innundation areas for the entire Connecticut coast should

                  lNo attempt has been made in this report to consider the potential impacts
                 of possible major @cutbacks in federal program budgets. State- officials must
                 consider these possible impacts in making decisions.

                                                     672

                  be  available sometime after 1987 when studies for the New York/Long Island
                  Sound SLOSH basin are completed. Once information for these two SLOSH
                  basins is available, the State and local communities will be able to issue
                  more precise evacuation notices to coastal residents for hurricanes.

                  (2) NW5 Real-Time Data at Selected Tide Stations         The NWS will proceed
                  with its program of temporarily upgrading telemetry at selected NOS tide
                  gage stations, including Bridgeport, CT. Implementation        of this program
                  will increase the speed with which storm surge data is         received by NWS
                  forecast offices in Silver Springs and New York City,          thereby enabling
                  improved forecasts of storm surge for extratropical storms. The availability
                  of this data should also permit an improvement in the          establisbment of
                  boundary conditions for real-time runs of the.SLOSH model.

                  (3) NOS  KGWLMS Program. The NOS will probably proceed         with its program
                  of installing a new generation of tide level gages, including the stations
                  at New London and Bridgeport.        Eventually, this information will also be
                  available to the NWS to help with improved storm surge forecasts. There
                  is  no clear time schedule for installation of the new gages, or for use
                  of the data by the NWS.

                        OpDortunities to Further Enhance Existing Programs

                  Each of the above programs is likely to proceed without any special effort
                by the State. However, by being fully aware of these programs and maintaining
                or establishing communication with the appropriate federal agency offices
                and individuals, the State may be able to influence somewhat the time at which
                some program actions are initiated and the degree to which they benefit Connee-
                ticut.

                  Conclusion    1b;    The State can work with federal agencies to maximize
                  the benefits of federal programs for'Connecticut and LIS.

                0 RFMMM              -@L-The State should take an active role in working with
                  federal agencies to take maximum advantage, of existing programs, and especially
                - program improvements underway or planned.

                  Recommendation # le: ,     The State should indicate to the th       ree federal
                  agencies (NWS, FEMA and COE) involved with Hurricane Preparedness Studies
                  that it desires to have the Hurricane Preparedness Study for, the New York/Long
                  Island Sound SLOSH basin initiated as soon as possible. Joint action with
                  the State of New York in requesting a high priority for initiation of this
                  study should be considered.

                  Recommendation # 1         State representatives should inquire with appropriate
                  NWS officials regarding the specific schedule for installation of the new
                  NWS telemetry instruments at the Bridgeport WSO, and encourage rapid instal-
                  lation if it has not yet occurred.

                                                       6-3

                     E , MMENDATION # I       The State    should explore further with NOS the,
                    possibility of a cooperative agreement or      other arrangement which would
                    permit early installation of one of the next generation tide level gages
                    in Connecticut. The New London gage site would be the most logical choice
                    because of the pending NWS telemetry upgrade at the Bridgeport gage site.

                 6AJ,a   Achievement of State Ubjectives   Through Existing PrograMS
                    Conclusion # 1c;     Existing systems and programs, even with planned improve-
                    ments, will not meet all of the State's objectives for better flood warnings
                    and reduced losses.

                    Reliance upon existing systems and     programs to collect coastal flood data
                 and to prepare coastal flood forecasts and warnings will require no extraordinary
                 expenditures by the State, and some improvements over present conditions can
                 be expected, such as:

                    (1) NWS use of near real-time storm, surge data from the two NOS stations
                    in Connecticut (and other locations outside Connecticut) may result in
                    small improvements to:

                    a*   storm  surge forecasts for extratropical storms, and
                    b.   storm surge forecasts for hurricanes and tropical storms by providing
                         improved data for establishment of boundary conditions      f or the SLOSH
                         model.

                    @2) The development of MEOWs from       SLOSH simulations should significantly
                    improve the accuracy of evacuation notices for hurricanes.

                    (3) The availability of near real-time storm surge      data f rom the two NOS
                    stations in Connecticut could improve the accuracy. and      timeliness of local
                    evacuation notices for tropical and extratropical storms (if NWS includes
                    actual storm surge elevations in its regular marine weather bulletins and
                    flood warnings).
                    However, even with scheduled improvements in federal monitoring and fore-
                 cast/warning prog   Irams, not all of the State's objectives may be achieved.

                    @1) There will be  no additional data   on wave action,   and no    improvements
                    in wave forecasts.

                    (2) The geographic coverage of storm surge data will not          be increased:
                    the number of coastal data stations will remain the same.

                    3) Near'real-time storm surge data will be    Avilable only for two locations:
                    New London and Bridgeport.

                                                        6-4

                         NEW PROGRAMS AND ADDITIONAL IMPROVEMENTS TO EXISTING PROGRAMS

                o CONCLUSION        2     To provide better coastal flood warnings and to reduce
                   flood losses, new   programs and substantial improvements to existing programs
                    beyond those already underway or planned - are needed.

                   Although improvements to all aspects of the present system are certainly
                possible, not all are equally feasible at the present time, nor will potential
                improvements in   each area yield'equal results in reducing flood losses.

                   Conclusion # 2a        Only limited improvements appear feasible to the existing
                   NWS forecast and warning system for hurricanes and tropical storms. Further,
                   because hurricane warnings are already conservative (i.e. attempt to warn
                   of the most severe likely impact), limited improvements will probably have
                   little effect on reducing flood losses, especially in Connecticut where
                   the coastal flood zone is relatively small.

                   Conclusion # 2b        Significant improvements appear possible in forecasts
                   of storm surge in LIS due to extratropical storms.

                   Conclu sion # 2c       Significant improvements also appear possible in forecasts
                   of waves in LIS due to extratropical storms and during non-storm condi-
                   tions..

                   Conclusion # 2d        Significant improvements in the data base for making
                   storm surge and wave forecasts i,s feasible.

                   Conclusion # 2e        Improvements in information needed for local decisionmaking
                   and actions is feasible by supplementing NWS regional forecasts and warnings
                   with more precise real-time information for specific geographic areas.

                o  R=MMR@MATION* The State should initiate actions which will result
                   in improved forecasts and warnings.

                   RecommendLition # 2a:       State initiatives should enhance the capabilities
                   of federal agencies to prepare regional forecasts and warning.
                   RecUmmendgtion # 2b:        State "initiativesIshould supplement regional f ederal
                   regional responsibilities with more detailed information in specific geographic
                   areas regarding the extent and timing of anticipated flooding.

                   Recommendation # 9c-        State Initiatives should non duDlicate federal
                   programs and responsibilities.

                   Reegmmp,ndation # 2d        The State should not issue information that copfliets
                   with NWS forecasts and warnings.

                                                        6-5

                          REAL-TI M              FLOOD MONITORING NETWOBE,

                 o CONCLUSION # 3         There  would be both     immediate and long-term benefits
                    from a real-time:   coastal flood monitoring   network established by the State
                    of Connecticut.

                    A monitoring network      would  make poss-ible improvements in      coastal flood
                 forecasts and warnings beyond that possi     ble with existing systems, and would
                 provide data important for other uses (see Table.1.1).

                 o RECOMMENDATION #-I.. The State should p      roce ed witb development of a real-time
                    coastal flood monitoring network

                          Upe of Monitoring Network

                    Many alternative monitoring network'      de signs are feasible,  each possessing
                 different capabilities and costs.

                    (1)   A monitoring network capable of         providing real-time   data on tides
                          and storm surge (and meteorological     parameters) and that is compatible
                          with the ASERT system is feasible.

                    (2)   Collection of real-time wave data, while providing important information
                          for flood warnings and other uses,, would not be totally compatible
                          with the ASERT system.

                    (3)   A monitoring network capable of providing -real-time data on tides,.
                          storm surge and waves- (and meteorological parameters) is feasible,
                          but would be completely independent of ASERT.

                    (4)   Costs for a re al-time monitoring network would   range:from approximately
                          $50,000 for an ASERT compatible network collecting only tide, storm
                          surge and meteorological data, to over $400,000 for an independent
                          network with two-way communications collecting data on tides, storm
                          surge, waves and meteorological @ parameters.

                    Recommendation      3a:    If the State determines that low         cost and full
                    ASERT compatibility are higher priorities than collection of wave data,
                    it should develop a monitoring network for tide, storm surge, and meteorological
                    parameters with one-way communications, similar tothat described in Alternative
                    1-b

                    Recommendation 4    3 N    If the State determines.tbat cost and ASERT compat-
                    ibility are not major    considerations, but complete wave data is important,
                    it should develop a monitoring network for tide, storm surge, wave energy
                    and direction spectra, and meteorological parameters with two-way communica-
                    tions, similar to Alternative 3b or 4.

                                                    6-6

                  Recommendation      3c;   If the State desires   to balance costs and system
                  performance, it should develop a monitoring network for tide, storm surge,
                  wave energy spectra, and meteorological parameters with one-way communications,
                  similar to Alternative 2b.2.

                  Recommendation # 3d:      Because of the variable quality and - type of instru-
                  mentation available, persons experiencied in oceanographic and meteorological
                  data collection, transmission and processing should be involved in the
                  final choice of a vendor and contractor for installation.

                  Recommendation # 3e:      The Committee on'Automated Flood Marning should
                  work with local communities, the research community, federal agencies,
                  and DEP program offices to identify priority sites for initial installation
                  of the two recommended roving gages.

               fi,=    Use of Date From Real-Time Monitoring Network

                  Conclusion # U       Real-time storm surge, wave, wind, and barometric pressure
                  data from points along the Connecticut coast would enable NWS forecasters
                  to improve both forecasts and bulletins of actual weather conditions.

                  Conclusion # 3b;     Geographically specific and accurate information on
                  actual vs. forecast storm surge and wave heights would permit local officials
                  and residents to make improved decisions and take appropriate and timely
                  actions to protect property from flood losses.

                  Recommendation # 3f;      The State should work with local NWS weather services
                  offices and the NWS Eastern Region Headquarters at Garden City, NY to arrange
                  for data from the monitoring network to be input to the NWS AFOS system.

                  Recommendation # 3r:      A base station should be established in the offices
                  of the two State Warning Points - Off ice of Civil Preparedness and Connecticut
                  State Police. These offices should relay data to the Regional OCP offices
                  and municipalities without their own base stations.

                  Recommendation # 3b:      The State should assist local municipalities in
                  setting up their own base -stations and properly interpreting data from
                  the monitoring network.

                  Recommendlition # 3i;     The State should provide a modem connection or
                  voice synthesizer to a   dedicated telephone line(s) to enable users without
                  a complete base station  to obtain data on a call-up basis.

                       FORECASTS AND WARDIINGS FOR STORM SURGE AND WAVES

                                                       6-7

                 0             DN 4 4    -A State-run  coastal 'flood forecast and warning system
                        while technically feasible     -- does not offer significant advantages
                    over continued reliance on the NWS.
                    Conclusion # 4a:     Storm surge and wave height forecasts cannot be accurately
                    developed based solely on a local monitoring network.

                    Conclusion # 4b:     NWS models and procedures for extratropieal storm surge
                    forecasts *and 'wave forecasts are not state-of-the-art and are not designed
                    specif ically for LIS.
                    Conclusion # 4c      There i  s no extensive data' establishing the accuracy
                    or inaccuracy of NWS forecasts.

                    Conclusion # 4d;     Complex    mathematical,  models utilizing both local     and
                    regional data are    needed to accurately forecast storm surge and waves.

                    Conclusion     4e:   Development and operation of these models would be
                    expensive     more expensive for the State than the NWS because NWS already
                    has an operational computerized database.'

                    Qgnclusion # U       State forecasts, if differenf from those of NWS, could
                    create confusion     and inaction by local officials and residents during
                    emergencies.

                 0        MMENDATION      A    Instead of developing its own flood forecast system,
                    the State should work closely with the NWS and        other federal agencies to
                    improve their ability to provide accurate and timely coastal flood forecasts
                    for Long Island Sound and the Connecticut coast.

                    Recommendation 44 4a       The State should request that NWS develop a new
                    model for forecasting wave heights in Long Island Sound. This should be
                    a model designed specifically for LIS, accounting for the shallow water
                    conditions and other factors peculiar to LIS.         Ideally this model would
                    forecast both open water waves and near shore waves. The model would be
                    utilized by the New York WSFO.

                    Recommendation # 4b        The State should request that NWS develop a new
                    model for forecasting storm surge for extratropical storms in LIS. Ideally
                    a numerical model specific. to LIS could be developed to replace the empirical
                    model now used by NWS.

                    Recommendations # Ao       The State should consider seeking cooperation
                    from Rhode Island and New York State (especially Nassau, Suffolk and West-
                    chester Counties) when requesting NWS to develop     new models.

                    Reco mendation # 4d:       The State should work with the New York, Bridgeport
                    and Hartford weather service offices to ensure that,, as soon as data from
                    the the Connecticut monitoring network are available to NWS in near real-time,
                    NWS will include the actual as well as forecast storm surge (and wave infor-
                    mation  if available) in its weather forecasts and warnings for marine and
                    coastal areas.

                                                   6-8

                 RecommendAtions # 4e:     The State should also establish a program to monitor,
                 through the monitoring network and observations, actual storm surge and
                 wave heights relative to NWS forecasts. In the event that monitoring of
                 NWS forecasts and warnings should show them to be seriously and consis-
                 tently inaccurate, then the State could more actively consider developing
                 its own forecast and warning program.

                 RecommendUtion            The State should work closely with FEMA, NHC and
                 the COE in preparation    of MEOW's and innundation maps for LIS to ensure
                 the highest accuracy and  greatest applicability.

                 Recl2mmendatio ns 4 4g:   The SLOSH MEOW's and associated innundation. maps
                 should be evaluated to determine if they can also be applied (directly
                 or modified) for use during extratropical storms.

                                  "PENDICES

                                                        A-1

                                        APPENDIX A: ASERT SPECIFICATIONS

                     The statewide automated f lood.    warning   system is called ASERT (Automated
                 State Evaluation   in Real Time).. The initial phase of the ASERT system is now
                 being installed and should be operational in late 1986. The system consists of 20
                 automated -rain gages, 6 weather stations (including precipitation gages), 6 radio
                 signal repeaters,. and 2 base stations.      Each base station includes an antenna,
                 radio signal receiver, data decoder, m'icrocomputer, ALERT software,            and an
                 uninterruptable power.supply backup.

                     An automated coastal monitoring      network that is compatible with the ASERT
                  ystem will need to be compatible with and make use of the radio signal repeaters
                 and base station components of the ASERT system.

                 The specifications provided on the following pages are taken from two        sources:
                     1.   Specifications for remote station :transmitters and    radio Isignal  repeaters
                     are taken from the bid specifications prepared by the Connecticut Department
                     of Environmental Protection and the Federal Soil Conservation Service in 1984.
                     Some modifications to these specifications have             been made and other
                     modifications may be made before the system is completely operational.
                     Because some changes may still occur, no attempt was made to update the bid
                     specifications to include any changes that have been made.

                     2.   Specifications for the base station components are taken from           product
                     literature of Sierra Misco, Inc. which supplied           all _major base    station
                     components   except for the microcomputer.

                                                      A- 2

                                              MATERIAL SPECIFICATION

                                                 624. TRANSMITTER

                 1    SCOPE

                      This specification covers  the quality of the   transmitter for the automated
                      gages. The transmitter shall transmit data in a format readable by a
                      Sierra-Misco Model 5051 receiver-decoder.

                2.    TRANSMITTER

                      a)   Sensor 'input signals are analog 0-5V DC signal -using digital SPDT
                           switch contacts.

                      b)   Signal transmitted in binary format consistent with NWS decoding
                           software.

                      c)   Transmission time of 230 milliseconds.

                      d)   Sends 4.digit station ID.
                      e)   Has 2 digitor   greater accumulator (00 to 99) which is automatically
                           resettable and  counts up and@down.

                      @f)  Input channels  of 4 digits and 16 analogs.
                      g).  Rechargeable gel cell battery to provide adequate power for one
                           years' operation. If recharging is needed during the year, a solar
                           panel or AC power, where available, will be used.
                      h)   Frequency stability of 0.0005%.'

                      i)   Operates in a temperature range   of -300C to-600C.

                      j)   Audio distortion of less than 8%.
                      Q.   The transmitter shall have sufficient output to pass the acceptance
                           test.

                      1)   Generates 2 test signals every 24 hours.

                                                           A- 3

                   3.    FREQUENCIES
                         Repeaters & Gages                       Receiving             Transmitting

                         Mohawk Mountain                          171.875                 :169.425
                           Thomaston                                                      171.875
                           New Milford                                                    171.875.
                           Barkhamsted                                                    171.875
                           Norfolk                                                        171.875
                           Sharon                                                         171.875

                         Oxford                                   169.525                 171.125
                           New Haven                                                      169.525
                           Stratford                                                      169.525
                           Oxford                                                         169.525
                           Bethel                                                         169.525

                         Southington Mt.                          171.125                 169.425
                           Plainville                                                     171.125
                           Wallingford                                                    171.125
                           Southington (Prec)
                             Sewer Plant                                                  171.125
                           Southington (River)                                            171.125
                           Southington (Precip),
                             New Britian Reservoir                                        171.125

                         John-Tom Mountain                        171.850                 169.425
                           Mansfield                                                      J71.850
                           Ell ington

                         Ekonk Mountain                           169.475                 171.850
                           North Stonington                                               169.475
                           Plainfield                                                     169.475
                           Thompson                                                       169.475

                         Plain Hill (Norwich)                     171.125                 169.475
                           Salem                                                          171.125
                           Lebanon (Bartlett Brook)                                       171.125
                           Norwich (Prec  W                                               171.125
                           Norwich (River                                                 171.125
                           Lebanon (Susquetonscut-
                             Brook)                                                       1-71.125
                           Lebanon (Deep River)                                           171.125

                         Mount   Parnassus                        169,525                 171.850
                           Old  Saybrook                                                  169.525
                           Haddam                                                         169.525

                         Direct to base stations
                           John-Tom Precip                                                169.425

                                                   A-4

                4.    GENERAL

                      a)   Moisture protected electronics located below ground.

                      b)   Transmission at 300 baud consisting of four ten-bit words, including
                           start and stop bits. Transmission interval of less than one-quarte.r
                           second. This shall include transmitter warm-up period suitable for
                           operation through a minimum of two radio relays.

                      c)   Data transmission shall utilize binary format consistent with NWS
                           decoding software - see attachment.

                      d)   An integral programmable clock which triggers regular check signals
                           for verification of system operation.

                      e)   An automatic regulator which prevents a transmitter from remaining
                           on.

                      f)   Modular components capable of field swapping.

                      g)   A selectable station ID on the electronic package.

                      h)   Integration of the electronics and power supply into a single
                           portable package weighing not more than 15 pounds, which is' water
                           resistant and will float in the base of the gage if it becomes
                           flooded.
                                                                                  I'                   I
                      i)   A carrying handle on the electronics package designed to allow
                           fastening of the lifting rope without blocking hand entry.

                           All transmitters shall comply with FCC type acceptance criteria.

                                                         A-5
                                                 MATERIAL SPECIFICATION

                                                     622. REPEATERS

                  1.    SCOPE'

                        This specification covers the quality of the self-contained automated
                        repeater.

                  2.    VHF RECEIVER

                        a)    A DC rechargeable, gel cell battery to provide adequate power for
                              one year's operation. If recharging is needed during the year,
                              AC power will be available for trickle charging.-
                        b)    Sensitivity of 12dB SINAD 0.35 microv   olts and 20 dB quieting 0.50
                              microvolts.

                        c)    Frequency stability of 0.0005% from -300C to     600C.

                        d)    Modulation acceptance of 7KHz.
                        e)    3.04B gain VHFomnidirectional receivi.ng antenna.
                        f)    Antenna input impedance of $'0 ohms.

                  3. VHF    TRANSMITTER

                        a)    A'DC rechargeable gel   cell battery to provide adequate    power for
                              one year's operation.    If recharging is needed--during the year,
                              AC power will be available for trickle charging.

                        b)    Frequency stability of �0.0005% from -30*C to 60*C.

                        c)    7 dB Directional antenna except'at Plain Hill which shall be a.3 db
                              Omni directional antenna.

                        d)    Power output shall be at least 25 watts.

                  4.    GENERAL

                        a)    All connections and low   loss coax  cables, as well. as s'ide  mount
                              hardware where needed, necessary to receive and transmit,the
                              required signal. All mounting hardware shall be stainless steel.
                        b)    Time to receive and   retransmit signal shall be less than-
                              20 milliseconds.

                                               625. RADIO FREQUENCY FILTER

                        SCOPE

                        This  specification covers  the quality  of the radio  frequency filter at
                        the repeater sites.

                  2.    FILTER

                        A Decibel Products D84002-2B (or equivalent) bandpass filter with an
                        overall insertion loss of 1 dB or less to the transmitter R.F. output.

                                                                          A-6

                                                                    ANTENNA

              DB224              VHF-OMNI          6 DB               360 Degrees           Bracket for 2'.-," top mounting. side mounting ava;lable
                                 Size: Length Approx. 20 Ft., Width 1'-- Ft.

                                        Model 5051R/D
                                 RECEIVER/DECODER

              GENERAL DESCRIPTION

                The Model 5051R/D Receiver Decoder receives transmitted data from field
              transmitters or repeate 'r stations, decodes the data and provides an RS232C
              output for computer input. The receiver and decoder are separated into two
              units so that the receiver can be located near the antenna tower and the decoder
              can be located in the central office near the computer. This reduces the amount
              of coaxial cable needed, minimizing the signal lost, and increases the strength
              of the received signal. The receiver/decoder is supplied with 15 feet of intercon-
              necting cable.
                The receiver is operated by 12Vdc battery or 11 OVac. A. trickle charger is
              included for a 12V battery. To eliminate the loss of data during power outages,
              S i e rra- M i sco reco rn m ends t h e u se of a battery for sta n d by power. Th e decod e r
              may a Iso be batte ry o perated h owever, wh en a U PS i s i n c I u ded f o r th e com p u ter
              it is normally operated by 11 OVac and is backed up by the computer's UPS.
                The base station receiver should be used with a high gain omni receive
              antenna. This will increase the incoming signal strength for remote sites which
              have marginal radio paths.

              RECEIVER FEATURES                                                      DECODER FEATURES
              � Low power consumption                                                * The decoder has tone filters to eliminate noise and interfer-
              � Entirely automatic during operation, requires no manual                ence from possible adjacent voice channels. This assures
                supervision                                                            accurate inputs to the computer
              � No external controls are available for people to touch and get       * Two RS232C output ports standard
                the system out of adjustment                                         & 12Vdc battery operated or 11OVac operated

              SPECIFICATIONS
              Receiver:                                                              Duty Cycle: Continuous
                VHF Frequency Range: 135-174 Mhz                                     Weight: Encased Unit: 3 pounds
                UHF Frequency Range: 400-512 Mhz                                     Size: Encased Unit: 71/4" W x 23/4" H A 9" D
                Sensitivity: 0.25 Microvolts Min. (12 dB Sinad)                      Antenna Input Impedance: 50 ohms
                            0.35 Microvolts Min. (20 dB Ouieting)
                Frequency Stability: +-.001 % (-30 to 60* C)                      50501D Decoder:
                Channels: 1                                                          Power Required: 11 OVac/6OHz or 12Vdc
                Modulation Acceptance: �5.0 KHz Nominal                              Current Drain: 50 milliairrip's
                Power Required: 12VDC, 50ma unsquelched                              Operating Temperature Range:'-30 to 600 C
                                           25ma squelched                            Output: 2 channels RS232C with standard RS232C connector
                Temperature Range: -40 to 60 degrees C                               Weight: 3 lbs.

                                                                                      A-7

                                                                                 Model 5073
                                                                 HYDRALERT SOFTWARE

                      Software: Available ALERT software comes in two packages: standard and ENHANCED. Both versions have an automated flood
                    forecast option. Each package is compatible with the U.S. National Weather Service ALERT standards and protocols.
                                                                                                  STANDARD HYDRALERT SOFTWARE FEATURES
                                  a data displays                                                    automatic data recovery, formatting, and filing
                                       precipitation group summary                                   automatic error checking
                                       single station display                                        100 sensor storage capacity
                                  e remote user communications (e.g., telephone)                     500 data reports stored per sensor
                                  e National Weather Service text file transfer                      data storage to nearest 1 minute
                                  0 precipitation map                                                environmental data types
                                       automatic hourly map                                              precipitation
                                       map up to 24 hours on-demand                                      water levels
                                  * audio/visual alarm                                                   temperature
                                       precipitation                                                     wind speed
                                       water level                                                       wind direction
                                  * limited line printer output                                          barometric pressure
                                                                                                         relative humidity
                                                                                                         snow pack water equivalent
                                                                                                         analog sensor

                                                                                Model 5073E.
                                                          ENHANCED ALERT SOFTWARE
                      Enhanced ALERT software contains all the features available                                 International Hydrological Services
                   in the standard package plus:                                                                        Enhanced ALERT System

                    FEATURES                                                                                              UTILITY PROGRAMS
                      full multi-user and mu'Iti-tasking capability                              ALARM-GROUP         .............      SET ALARM FOR A GROUP
                      menu-driven operation                                                      ALARM-OFF        ................   TURN OFF ACTIVE ALARMS
                      on-line user assistance                                                    ALARM-SEE        .................     LOOK AT ACTIVE ALARMS
                      dynamic data storage allocation                                            ALERT ... ***''**'"*'*       ........  START ENHANCED ALERT
                      data base utilities and editing                                            STREAM-SET       ................      BASE SET STREAM GAGES
                      data storqd to nearest second                                              DEF-DBASE        ........................     DEFINE DATA BASE
                      manual data entry                                                          DEF-MAP          ................. DEFINE PRECIPITATION MAP
                      event reporting and interrogation capability                               DEFGROUP         ..........  DEFINE PRECIPITATION GROUPS
                      data archiving and retrieval                                               DEFINE-RATING       ...............    DEFINE RATING CURVES
                      environmental data types                                                   RAW-DATA         ..................    SINGLE STATION DISPLAY
                         user specified                                                          PRECIP     ...............   PRECIPITATION GROUP DISPLAY
                      data displays                                                              HYDROGRAPH          .......................  HYDROGRAPH PLOT
                         multiple sensor type groups
                                                                                                 MAP-ALPHA        ................   DRAW MAP BACKGROUNDS
                         precipitation group summaries                                           NAMECHNG         ..................    CHANGE STATION NAME
                           user selectable date and time interval                                PMAP    ....................     DISPLAY PRECIPITATION MAP
                           user selectable grouping                                              SENSOUT          ....................  DISPLAY SENSOR NAMES
                         single station                                                          SET-ALARM        ......................    SET SENSOR ALARMS
                           user selectable date and time interval                                SHUTDOWN         .......................      SHUTDOWN ALERT
                         data plots                                                              STAGES       .....................     SENSOR GROUP DISPLAY
                           user selectable date and time interval                                STGGROUP         ...................   DEFINE SENSOR GROUPS
                      rating curves                                                              TIMEZONE         ..................    DEFINE LOCAL TIME ZONE
                      precipitation maps
                         up to 10 different map outlines
                         user selectable time and date interval
                      text labeling of station names
                      action/response displays
                      external control capability
                         terminals      map displays, optional
                         alarms         beeper systems, optional
                      audio/visual alarm
                         all data types can be alarmed
                      complete line-printer output

                                                                           A-8

                                                                                          Model 5071 UPS
                                                                     UN, INTERRUPTIBLE POWER SUPPLY

                                                                  GENERAL DESCRIPTION

                                                                   The5071UPS is usedto keep the computer operational during powerfailures
                                                                  and to protect the computer from low voltage "brown outs," lightning or other
                                                                  types of transient voltages and AC line noise.
                                                                   Since even a 16 millisecond loss of power can cause the computer to drop out
                                                                  of operation and need rebooting, Sierra-Misco considers the UPS essential for
                                                                  the trouble tree operation of the central station.
                                                                   Operation is simple. AC power is converted to DC power and is used totrickle
                                                                  charge low maintenance 12volt batteries. The batteries in turn supply power to
                                                                  an inverter circuit which creates AC voltage for the computer and decoder.
                                                                  There is no loss in synchronization, no loss in phase, and no loss in output
                                                                  voltage during an outage or return to AC power.                               rs
                 The 5071 UPS incorporates a two-stage precision battery charge system that recharges the battery system within 6 to a hou
              after use. Once the batteries have reached 95% full charge, the two stage charge system switches to float operation.
                 When used with one 5071UPS-B Battery the UPS will operate a 5071 Central Site Display continuously for approximately 20
              minutes. More batteries can be installed to allow for longer power failures. If extended power failures are anticipated a motor
              generator set should be used in addition to the UPS.
                 A battery cable and battery are supplied with the UPS.

              SPECIFICATIONS

                                                  Model 5071UPS (60 Hz)               Model 5071UPS-2 (60 Hz)
                                                  5071UPS-1 (50 Hz)                   5071 UPS-3 (50 Hz)

              Power Out                           300                                 600
              Power In                            110/220                             110/220
              Operating Time with 1 Battery       20 minutes                          20 minutes
              Operating Life of Battery           Approx. 5 years                     Approx. 5 years
              Noise Attenuation                   >90 db                              >90 db
              Regulation                          95 to 130 VRMS                      95 to 130 VRMS
              Size                                22" x 17" x 10"                     22" x 17" x 10"
              Weight                              80 lbs.                             150 lbs.

                                                                  MICROCOMPUTER

                  The base station microcomputer                      is an IBM PC/XT configured,                   with 512 K of
                  memory, one 360 K 5 1/4" floopy disk drive, and a 10 MB hard disk drive.

                                                               OPERATING SYSTEM

                  The Enhanced ALERT software works                         under the QNX multi-user, multi-tasking
                  operating system.

                                  APPENDIX B: STORM SURGE AND WAVE MODELS

                 B.1      STORM S]U&GF, MODFLS

                          Introduction

                    Theoretical models of storm surges all involve some degree of approximation
                 and often questionable assumptions of the actual physics involved.          The first
                 theoretical models of storm surge were analytical, calculating storm surge
                 along straight continental shelves with parallel.. contours and constant wind
                 stress.   To solve these equations, bottom stress terms had        to be linearized,
                 and other aspects of the physics were only approximate.            In general, these
                 analytical techniques provide a useful basis for understanding some of the
                 physics of storm surges, but lack the full physics governing the process required
                 for accurate predictions.

                    An alternative approach to storm      surge modeling arose once computer time
                 became more readily availablet and numerical techniques, acquired more widespread
                 popularity.    In the past fifteen years, ever-increasing numbers of numerical
                 models have been developed which can address storm surge problems. Many of
                 these models are similar, @ differing only in representation .-of some of the
                 terms in the equations of motion, or in the precise -detail of the numerical
                 implementation of a term (a good example being the variety of ways to implement
                 the nonlinear inertial terms). Many of these models differ in a more fundamental
                 fashion, however, in that they represent different physics.

                    As an example, bottom stress -- the resistence of the rough ocean bottom
                 to propagation of -any surface disturbance -- can be'approximated in many ways.
                 One approximation invokes a higher order turbulence closure scheme to approximate
                 the effects of bottom friction. This yields adequate results in many cases,
                 but also increases computational time and requires more assigned parameters.
                 A simpler approach is to incorporate a linear bottom friction model, where
                 the friction coefficient is dimensional because of the linearity in velocity.

                    More complex, but largely empirical in derivation, is a quadratic friction
                 term 9 where the friction coefficient describing the coupling between the flow
                 and the bottom is a more appealing nondimefisional number. These techniques
                 generally ignore flows at different time scales. -For instance, a storm surge
                 model will ignore flows at much higher or lower frequencies. Although tides
                 may be incorporated in these models, the effects of surface gravity waves
                 (wind waves) and other disturbances generally are not included. Recent theory
                 has shown that higher frequency flows increase the bottom friction associated
                 with longer.  period motions such as tides and storm surges, so future storm
                 surge models  will have to improve the physics of this term.

                    The above   example illustrates the magnitude    of the uncertainty in developing
                 and applying a storm surge model. Computer methods have increased our abilities
                 to consider more realistic physical cases, but there are still theoretical
                 uncertainties as to what constitutes a realistic physical case. The importance
                 of differences in model details are vigorously debated among scientists and

                engineers developing these models.     The bottomline is that there is no single
                model which will best fulfill the job of accurately predicting storm surge.
                A model which performs well at one site may not perform well at another, because
                of improper physics. For instance, a model with a poor bottom friction represeir-
                tation may perform well in a deeper embayment, but do a much poorer job in
                Long Island Sound,, which is much shallower. The best model for a particular
                area may also be too expensive to run for the variety of cases required for
                compilation of an atlas of storm surge scenarios, for instance.

                   Following is a brief overview and description of the two major techniques
                for estimating storm surges, and how they have been. and may be applied to
                the Connecticut coast.

                B.1.2   Statistical Storm Surge StudieS

                   Many of the estimates of storm surge height are derived from historical
                data concerning past storm surges.        To interpret these past results and to
                apply them to forecast    'future anticipated storm surges, the observations must
                be placed into some statistical framework. This statistical framework is fraught
                with uncertainties and assumptions, but can be applied in a climatological
                sense to provide estimates of expected surges. This method, however, cannot
                provide estimates of expected surge during a particular storm, a shortcoming
                making them of limited utility for this study.
                   Where possible,    tide gage data are used to generate statistics of *storm
                surges (46, 187) in concert with non-gaged estimates of surge level during
                large hurricanes and storms.       These observations are then fit to a statis-
                tical distribution of storm surges and superelevation.              Boon et al. . (187)
                use a Poisson distribution, others use a. Weibel distribution, while Dewberry
                and Davis (46) use a Pearson Type III distribution.            There is considerable
                debate about the proper type of distribution to use; if the forecast is. for
                a 100-year frequency or greater,, the results may not be too sensitive to.'          the
                distribution. However, 500-year events are particularly susceptible to differences
                in distribution. selected.

                   Another common problem in       using statistics of extreme events to forecast
                flood levels As the occurrence of outliers.         Outliers are generally extreme
                events which significantly degrade the fit of the data to a statistical distri-
                bution, compared to all other data. These outliers commonly are larger events,
                which should influence the forecast. There is no standard technique for treating
                outliers, but it is not uncommon to leave these out if the other data fit
                the statistical model without it. Although not uncommon in practice, it might
                be better to suggest a different model than to eliminate data because of lack
                of f it.

                   Most statistical  storm surge models neglect changes in relative sea levels.
                Since relative sea    levels are. indeed increasing along the Connecticut coast
                this should be considered in longer-term estimates of storm surge.              It will
                have no significant effect on storm surge estimates for time periods shorter
                than 20 years or so.

                                                       B-3

                 STATISTICAL STORM SURGE STUDITN

                    There have. been three major studies       of statistics of storm surges along
                 the Long Island coast of Connecticut.       The first, in 1973, was published by
                 the New England Division of the U.S. Army Corps of Engineers (COE) (89). Those
                 study results were revised in 1980 during the second study by the COE (6)
                 using tide-gage data from five stations (Willets'Pont, NY; Stamford, Bridgeport,
                 New London, and Stonington, Connecticut).       A major decision in the 1980 study
                 was to eliminate the 1938 hurricane from the statistical model, thereby lowering
                 the 100-year flood estimates, particularly in eastern Connecticut.             Tidal
                 flood profiles from this study are shown in Figure B.1.

                    In 1982 Dewberry and Davis (D&D) performed the final study for the Federal
                 Emergency Management Agency (FEMA) (46), which was essentially a review of
                 the 1980 COE study.     The major difference resulted in D&D's inclusion of the
                 1938 hurricane in their statistical model fit, particularly in eastern Connecticut
                 where the 1938 surge was highest. D&D recommended the adoption of the COE
                 1980 surge profiles, except in the New London area where an increase was suggested
                 to fit the 1938 hurricane data.    The resulting profile (Figure B.2) was adopted
                 by FEMA for updates to its coastal flood insurance studies.

                    The latest 100-year flood profile   shows the highest flood level in western
                 Connecticut (12.2 feet NGVD), lowering to' 10 feet by Stratford. From Stratford
                 east the level rises to about 10.7 feet at East Haven, followed by a gradual
                 decrease to about 10.0 feet at Waterford. At New London the level is 10.0
                 feet NGVD. To the east of New London-         the flood increases from about 10.0
                 feet to 10.8 feet at Stonington.

                    These flood profiles show that storm       surge increases dramatically within
                 the Thames River estuary. According to the    COE 1980 study, storm surge increased
                 -from 9 5 feet to 14.3 feet NGVD , at the     100-year level as the distance from
                 the mQtb of the Thames River. increased. The 1938 hurricane surge ranged
                 from 9.8 feet -at New London up to 15.2 feet in Norwich. This estuarine effect
                 may not be modeled adequately by. the numerical approximations, so care should
                 be taken to assure that this increase in height in embayments is. known to.
                 flood management personnel.

                 NWS STORM SURGE     MQDFL FOR FXTRATROPICAL STORMS
                    The NWS has adopted     .a storm- surge model for extra-tropical storms (73)
                 which is a statistical storm. surge model (or empirical, in,.NWS's terminology).
                 Using simple, regression methods, the observations of storm surge at ten coastal
                 locations. (with tide gages) are related to sea level pressure values as forecast
                 by the National Meteorlogical Center (NMC).        Using.68 storms occuring from
                 1956 through 1969, regression equations were established using a screening
                 procedure,. to allow the best fit between observed surge and sealevel pressure,
                 at a minimum number of stations to reduce artificial predictability and increase
                 forecast skill.

                    The procedure is entirely empirical, and is based on the observed and theorized
                 relationship between atmospheric pressure and storm surge.          The errors in
                 this empirical technique can be very large, although it does a reasonable
                 job forecasting during some storms. These regression equations apparently
                 have not  been updated since 1974, and there are no present plans to do so (71).

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                                                                                                                                                             1150 YEAR           Y TIVAL PLOOD
                                                                                          NUMCA&Z XM         A         Me   md1
                                                                                                                                                                  YEAR          r r110AL   000

                                                                                                                                                                                                            7

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                                                                                                        ;19
                                                                                                                                                              NOTES

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                                                                                                        Vw w"

                                                                                            A           7                                                         12          13         1.
                                                                    DISIA"Cl IN STATUTE   MILES fROM MOUTH OF THAM@S RIVER AT EASTERN POINT

                                        FIGURE           B.l:               Tide         Levels           and Flood Profiles                             for       Connecticut                   (Cont'd)

                                                                                                       W
                                                              40                        44

                                                                                                  4                     4
                                                                                              :'4
                                                                                                                       -.4

                                                                                                                                    Libil
                                                                                                            "A                                   21 M!,
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                                                                                                                          .......  4-                       LEGEND
                                                                                                                   ... .........
                                                                                                                                     7
                    SOURCE: Dewberry              Davis.      1982.     Tidal Flood Profiles           for   the    Connecticut                                  5W YEAR rL000
                                  Shoreline of Long Island Sound. Prepared for the, Pederal Emergency                                                            100 YEAR FLC'30
                                  Kanagement Agency.
                                                                                                                                                                 50 YEAR FLOOD,
                                                                                                                                                                           000
                                                                                                                     ....................        - - - - - -     10 YEAR FL

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                                                                                        51. Aiu-rr MILLS - LONG ISLAND SOUND
                                            @ 4M-,

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                                                 7

                                                 ......... .

                                                        PIGURE B.2:                   Flood Profiles for Connecticut

                                                                                ELEVATION IN FEET ABOVE "GVb

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                                          FEDERAL EMERGE11MY MANAGEMENT A"Ncv
                                                                                           TIDAL FLOOD                PROFILES.
                                           NEW ENGLAND COASTLINE
                                                                                       LONG ISLAND SOUND & BLOCK ISLAND SOUND
                                                                                                  T
                                                                                4 4-4
                                                                                I
                                                                                Ittl
                                                                                L L-Lill

                                                                                      01-9

                     For most of the ten stations, two regression equations were- developed.
                  One, utilizing sea level pressure at several locations, is used on the NMC
                  computers to generate a storm surge forecast that is provided to local National
                  Weather Service offices.       A second equation, utilizing sea level pressure
                  from fewer locations, can be solved manually by local weather service offices
                   o forecast storm surge.

                     Stamford, Connecticut is one       of  the ten locations for which regression
                  equations were developed.        Only  five sea level pressure stations are used
                  in the Stamford equation (as opposed to 7 - 15 stations for most locations),
                  and the same equation is used by both NMC. and local weather service offices.
                  The equation, used for Stamford is shown-at Figure B.3.

                               SS(SFD)   24.061+ .06265 P(12)t - .07930 P(31)t .03170 P(40)t
                                             + .05521 P(18)Zt - .02926 P(27)t

                                SS = Storm Surge (in feet)
                                 P = Sea Level Pressure (in millibars)
                             (12)   Grid Point f or Sea Level Pressure
                                 t   Time of Sea Level Pressure Observation

                     FIGURE   B.3: Regression Equation for   Extratropical Storm   Surge Forecast,
                                   Stamford, Connecticut

                     Figure   4.1  illustrates the forecast vs. observed storm     surge at Stamford
                  for two storms   in 1972, and indicates that the model consistently over-estimates
                  storm surge at Stamford. The COE, which uses NWS storm surge forecasts as
                  an aid in operating the Stamford Hurricane Barrier, also reported that forecast
                  surges are usually higher than recorded surges (25,39).

                     If the State of Connecticut were to incorpora.te this type of extratropical
                  storm surge forecast into a coastal flood warning system, several improvements
                  to the current procedure are suggested. First, the regression equations should
                  be developed for additional locations having storm surge records (Bridgeport,
                  New London, Old Saybrook). Second, the equations should include additional
                  sea level pressure stations which should be carefully chosen based on there
                  predective capability as indicated by historical records for many recent storms.
                  This improvement in the methodology of regression is needed to assure robust
                  estimates, and minimize problems of artificial predictability.

                     The utility of these statistical techniques is limited, however              It is
                  recommended that this methodology be replaced by dynamic models of storm surge,
                  even for extratropical storms.

                                                       B-12

               ILL3.    Numerical  Storm Surge Models

                  To predict the storm surge associated with a storm of arbitrary features
               (such as path, wind speed, size), the statistical storm surge summaries are
               inadequate. Necessary in this situation is a realistic model of the effects
               of winds on the surface of the water, including all physics appropriate for
               the ocean basin of concern. Generally the model uses as input some representation
               of the storm, including its path, wind distribution, and speed.

                  For the case of hurricanes, such models have long been in existence. The
               first such model, developed by Wilson in 1957 (188), includes the parameters
               of central pressure index, the distance from the hurricane center to the point
               of maximum. winds, and the forward velocity of the hurricane. Subsequent repre-
               sentations of hurricanes include a more realistic description, increasing
               realism while also increasing computational time.

                  Models for extra-tropical storms are much more difficult to generalize,
               and are derived most often from synoptic weather charts, updated every four-
               to-six hours.

               MODFL TYPIE AND PARAMEJERS

                  The number of numerical models which have been applied to storm surge problems
               is very large, increasing rapidly each year.          More than 30 such models were
               reviewed as part of this study.         The different types of models and some of
               the important parameters used in such models are reviewed briefly in the following
               pages.    Although not exhaustive, this discussion provides some understanding
               of the difficulties in representing the physics of the ocean in a numerical
               format, and illustrates some of the pitfalls to be avoided.

                  For further review of the state-of-the-art in storm surge prediction, several
               references are available.      Marine Forecasting by Niboul (189) provides a useful
               review of the concepts of storm surge modeling, current to the date of publication.
               Pagenkopf and Pearce (190) provide a detailed discussion of several types
               of storm surge models, their differences, and their performance in predicting
               surges during a hurricane. Many similar publications exist, from an introductory
               level up to the most current.

                  Numerical storm surge models use the basic hydrodynamic equations governing
               fluid flow as a starting point. The appropriate equations are the Navier-Stokes
               equations for fluid momentum, and the continuity equation.               The diff erences
               are in the way these equations are implemented numerically, which terms are
               included, how the terms are included, and the application of the solution
               of these terms to a physical problem.

                  Some of the important classes of. solution are           discussed here.      Basically,
               the storm surge models include inertial effects,           incorporating the unsteady
               term in the equations of motion; the convective term; and a Coriolis acceleration.
               Theotber terms in the equations are the pressure gradient term and the diss-
               ipation term.      Besides diff erences   .in numerical implementation and gridding
               of the equations, the parameterization of the dissipation term is one of the
               largest diff erences between various models.

                                                       B- 13

                     One  of the most fundamental differences between models is the numerical
                 scheme   implemented. Two methods for approximating the equations of motion
                 numerically are finite difference and finite element techniques. Finite element
                 techniques have only recently (since early 19701s) become popular in ocean
                .hydrodynamics, while finite difference techniques have been around a long
                 time. . Pakenkopf and Pearce (190) provide a quantitative comparison between
                ,these two techniques, using a modified finite difference model of Pearce (191)
                 and finite element model of Connor and Wang (192) and Wang and Connor (193).
                 The finite element model is generally considered to be more appealing because
                 of its flexible grid,- where grid elements need not be of constant size.          The
                 finite element implementation is normally considered to be more expensive
                 to run (194) although this is disputed by (190,195).           Finite elements also
                 have different stability constraints than finite difference, allowing larger
                 time steps for',a given level of numerical stability.

                     Finite difference techniques are still the most        widely used in spite of
                 the advantages of the finite element models.          The higher cost of the finite
                 element technique has made many investigators shy         away -from it.     Although
                 for a long-time-simulation the finite element scheme may be cheaper, it is
                 normally much more expensive for shorter simulations.          The finite difference
                 method is also the most widely taught in engineering schools.

                     To get around the problem of rectangular grids required      by finite difference
                 models, several interesting schemes have been proposed and       implemented. First,
                 a boundary-fitted coordinate system has been suggested such that in a transformed
                 coordinate system the grid is rectangular'  - but in the norr-transformed coordinate
                 system the grid is not regular.        This allows the models to be adapted for
                 specific geometries of shorelines.       Examples of this technique are Johnson
                 (196), Thomson et al. (197), and Spaulding (101).

                     Another solution has been to develop -a metho        Idology for irregular grids
                 in finite difference techniques.         An important series of articles on this
                 technique have been produced by Thacker (197, 1918, 199).      In this methodology,
                 an irregular grid is produced to conform to the boundaries of the problem,
                 and the appropriate numerical transformations applied to it.          Although this
                 technique has provided some interesting results, there is still a question
                 about stability @ of the method (195), and, arguments about why it may be more
                 appropriate than alternative techniques.         Finally, a variety of other grids
                 have beew applied, such as curvilinear grids and stretched rectangular grids.
                 These all must be applied with care, to avoid or minimize stability problems,
                 and are generally difficult to achieve maximum resolution in those areas where
                 itis needed most.

                     Since computational time and resultant expense increases as the size of
                 the computational grid element decreases, there is considerable work on reducing
                 the size of the grid to an acceptable level, and living with the degree of
                 accuracy resulting (finite element grids do not have this limitation).            The
                 smaller the grid size the smaller the, time step required to achieve stability;
                 hence the trend (discussed above) towards achieving finite difference grids
                 having variable resolution.       One way of getting around the limitations of
                 the finite d'ifference restrictions is to run two grids,' in a nested sense.
                 A coarse grid is run to cover the offshore conditions, where the fine resolution
                 is not needed, while a finer mesh grid' is run inshore, where resolution is
                 essential. This is an acceptable compromise for modeling areas with variable

                                                    B-14

               resolution requirements using finite difference techniques.      It has been used
               -in Long Island Sound, for instance, by Gordon and Spaulding (99) and Spaulding
               and Gordon (100) to calculate the tides.

                  Besides the numerical implementation of the equations of motion, and the
               problem of gridding the geographic area to obtain adequate resolution at a
               reasonable cost, there is a consideration of the dimensions of the equations
               to be calculated.   The simplest models are one-dimensional, which the analytic
               solutions tended towards.    The next step is two-dimensional, the most common
               being a vertically-integrated model with the vertical dynamics ignored. The
               two horizontal coordinates, x- and r, then express the momentum balances
               in the flow.     Finally, there is a class of three-dimensional models, which
               are required to specify flows when the vertical dynamics are important. Generally
               as the number of dimensions increases, the cost of the analysis increases.
               Many examples of these different models exist, and are not detailed here.
               Most storm surge models are vert ically- averaged two dimensional models, since
               the vertical, dynamics are not particularly important in describing storm surge
               processes. Although this is an assumption placing a constraint on the accuracy
               of the model, it is not an unreasonable assumption.

                  Other differences between models include the parameterization of bottom
               friction and other dissipation processes.    Many models use a quadratic bottom
               friction, where the dissipation is proportional to, the square of the near-bed
               velocity. Commonly, a Chezy-type friction is applied, or a Manning formulation.
               These ignore the effects of the bed geometry and the surface wind waves on
               the bottom friction, a step which is reasonable in deep water but' not acceptable
               in shallow water. As Grant and Madsen (200, 201), have shown, in shallow water
               where waves are important, these higher frequency motions increase the'drag
               felt by any longer period motions across the bottom.          Incorporation of the
               effects of the non-linear interaction between waves and currents is required
               if dynamics of shallow water flows are to be described accurately. Few numerical
               models incorporate this bottom friction due to wave-current interaction, but
               for Long Island Sound such a physical model should be included for accurate
               storm surge prediction.

                  Another matter of critical concern in numerical modeling is the       prescription
               of boundary conditions. Boundary conditions have a direct. impact on the storm
               surge calculations, and must be analyzed critically.         For, instance, at the
               coastal boundary, several types of boundary conditions are possible. First,
               there can be zero velocity normal to the boundary, a condition which is reasonable
               if the coastline is a high, steep cliff.    This is a common boundary condition.
               However, in the case of a low-lying shoreline, where wetting will occur, this
               is an inappropriate boundary condition.      In this case, more realistic boundary
               conditions must be applied, with a knowledge of bow flooding occurs. This
               entails the use of a boundary condition applied along a moving boundary, a
               modeling problem which has been solved before. . This moving boundary requires
               fine resolution, again requiring a nested grid to allow computations to proceed
               at a reasonable cost.

                  On the open boundary which terminates the model to seaward and laterally,
               a similar dilemma arises. An open boundary will have several possible conditions
               applied to it.    Physically, one requires a description of the physics outside
               of the region, to match with the physics derived for the interior with the
               model. This is not generally known. To minimize these open boundary problems,.

                                                        B- 15

                 one generally applies open boundary conditions         far from the coastal region
                 of interest, and applies a condition which is not unreasonable physically.
                 The sensitivity of the surge calculation to different open boundary conditions
                 can be determined numerically; if the model is extremely sensitive over the
                 time duration of the simulation, a more complicated open boundary condition
                 may be applied.

                     The simplest open boundary condition is that there is a continuity in sea
                 surface across the   boundary, and that there is no flux parallel to the boundary.
                 As emphasized by Reid (202), this condition corresponds to complete reflection
                 of gravity waves.     If this reflection is not large, or the time interval sufficr-
                 iently small, this   may not be a restrictive case.         When the surge behaves
                 like a f ree Wave,  a radiation condition must be applied to minimize the effects
                 of the reflectivity of the open boundaries (203).

                 CONSIDERATIQNS      FOR A LI

                     This brief overview of the modeling problems associated with implementing
                 the equations governing storm surge illustrates the variety of uncertainties
                 and problems associated with these models. With the debate within the scientific
                 and engineering community sti    11 showing no   'signs of abating, there is no clear
                 consensus on which model to use for what situation.            There are some clear
                 trends, however.

                     1) A two-dimensional numerical model, is appropriate for storm-surge calcula-
                 tions*    If the    2-D model uses finite difference techniques, a nested grid
                 must be   used.     If the' 2-D - model is finite element, then a single grid could
                 be used.

                     2)   The open   boundary conditions    must  be implemented carefully. On the
                 open boundaries,    a radiation condition  may  be required for certain storm paths.
                 Since there is only a single open. boundary in the Long Island Sound 'case,
                 this implementation should not be 'difficult.            If a radiation condition is
                 not used, numerical experiments must be run to show that the model is not
                 excessively sensitive to the type of open boundary condition selected.

                     3)   The shore boundary conditions should reflect the possibility of            land
                 wetting for the low-lying areas *of the Connecticut and Long Island shores,
                 paying   particular attention to the estuaries, of Connecticut.        With the large
                 storm surge in the Thames River, for instance, due consideration must be paid
                 to their effect on storm surge downstream. Again, numerical simulations should
                 be required to demonstrate the sensitivity of the model to the boundary conditions
                 selected.

                     4)   Any model will require input of meteorological        condition's to run the
                 model.    Some models will 'work off atmospheric pr       ,essure input, others need
                 calcuated winds. Some models require speed of movement of the storm, others
                 will interpolate from synoptic weather charts.          For tropical cyclones, most
                 models incorporate a simple model of winds within a cyclone,@ requiring only
                 parametric input such as central pressure anomaly, some length parameters
                 relating to winds, and speed of propagation.          Preferable by far is a model
                 which accepts atmospheric pressure input, and calculates the. surface wind
                 stress field from that.      A comprehensive storm model may not apply to all
                 types of coastal storms, but should be emphasized in future research on progress

                                                      B-16

                in storm surge modeling.

                   5)   Shallow water processes should be -represented well in any model of
                Long Island Sound. Bathymetry must be input with as -much resolution as possible,,
                and incorporation of nonlinear bottom stress due to wave/current interaction
                should be made if possible.
                   6)   Because of the effects of tides on storm surge,, the numerical model'
                should combine a tidal model with a pure storm surge model. This way total
                water elevations can be predicted, not just the storm surge component.               If
                this model is run in real-time, such a tidal inclusion is straight-forward,
                and is routinely performed.     If the model is run in a. forecast mode with an
                eye towards generating an "atlas" of storm surge scenarios,           then the tide
                must be added in after the model is run.

                NUMERICAL STORM SURGE MODEJS TISED IN LONG ISLAND SOUN

                   Several numerical storm surge models, o     r portions of larger    models, which
                have been used in Long Island Sound are briefly reviewed below.

                   Laevastu and Callaway (204) bad a 2-D finite difference model      of Long Island
                Sound as part of a larger model.        This model had a grid spacing of 6.6 km.
                The grid is so coarse as to be of little value in the prediction of local
                storm surges.

                   Leendertse and Liu (205) applied a 3-D numerical finite difference mode           I
                to Long Island Sound, using a horizontal grid spacing of 1.9 km. These were
                of short duration (order of a single tidal cycle), the primary intent being
                to estimate turbulent energy fluxes in the region.

                   Beauchamp and Spaulding. (206) developed a tidal model of Long Island Sound
                as part of the New England Bight, using a 2-D finite difference model with
                1.852 km grid spacing.       With limited observations available against which
                to compare the model, the work could not be evaluated, completely.

                   Murphy (207) applied the same 2-D finite difference model to a small area
                within Long Island Sound.        The results are not particularly applicable to
                the present study.

                   Two models will be discussed in a little more detail: one            by Spaulding
                and Gordon (100), and the SLOSH hurricane model by NW8 (93, 94)

                   Spaulding    -- Spaulding and his associates have extensive experience in
                modeling-the waters of southern New England. Papers by Gordon and Spaulding
                (99) and Spaulding and Gordon (100) discuss the application of a nested numerical
                tidal model to the southern New England waters, including Long Island Sound.
                Although primarily a tidal   'mode 1, it can be adapted easily to include storm
                surge effects.     The model is a 2-dimensional, vertically integrated finite
                difference  'implementation of the equations of motion. , It has ignored the
                convective acceleration terms, and employs a Chezy-type bottom friction formula-
                tion.   It ignores the wave-current interactions and their effect . on bottom
                friction. The larger grid interval was 5 55. km' while the smaller grid interval
                was 1.852 km. The model appeared to work well on tidal time scales associated
                with this study.

                                                     B- 17

                    Since storm surge effects were   not included, there was no wind stress term,
                 and' the time history of development of a wind field could not be included.
                 In a later paper (101), wind stress (or surface stress) was included in the
                 formulation using boundary fitted coordinates, and,applied to the North Sea.
                 Any future application of the Spaulding-type models must include a storm model
                 for generating vector wind fields. Such a model is not described in the literature
                 in connection with the tide models cited above.

                 NWS SLOSH Model        SLOSH (Sea, Lake, and    Overland Surges from Hurricanes)
                 is a numerical tropical storm surge model developed for real-time forecasting
                 of 'hurricane storm surge along the continental shelves. It was adapted from
                 an earlier model used by NWS, SPLASH (Special Program to List Amplitudes of
                 Surges from Hurricanes).    It is a two-dimensional, finite difference numerical
                 model with a curvilinear, polar coordinate grid (Figures B.4. and B.5) to
                 increase near-field resolution, while sacrificing far-field resolution.        The
                 model includes a storm wind model, which is fed by several time-dependent
                 meteorological storm variables:

                    1) Latitude and longitude of storm- positions at 6-hour intervals for a
                 72-hour storm track. This begins 48 hours.before the storm's nearest approach,
                 and ends 24 hours after the nearest approach.

                    2) Storm central pressure at 6-hour intervals.

                    3) Storm size (center to region of maximum winds) at 6-hour intervals.

                    Wind stress vector fields are computed independently by the model, and
                 are not input parameters. The initial height of the still-water surface before
                 the storm is required.    Far-field boundary conditions are 'computed far from
                 the region of forecast interest to minimize their effects on the simulation.
                 All geographical' and bathymetric -data must be input by the user, continually
                 updating it in the case of real-time simulations to assure proper boundary
                 perf ormance.

                    The SLOSH model    makes several approximationsi    First, it does not include.
                 the advective terms from the equations of motion, since they have been shown
                 to be small except in regions of large'velocity gradients. Second, it incorporates
                 a time-history bottom stress, formulation (208), which does not incorporate
                 Chezy-type friction coefficients, nor wave-current interactions. NWS acknowledges
                 that the wave/current interactions are important on shallow shelves, but not
                 on those of intermediate depth.     Since Long Island Sound is a shallow shelf,
                 bottom friction due to nonlinear wave/current interaction should be included.
                 Other wind-wave effects such as run-up and set-up are not treated. explicitly.
                 They are treated implicitly in their use of bottom stress terms and other
                 terms which are derived empirically from a historical data base. These wave
                 ,terms act as noise sources, and their effects are included although not in
                 a physical manner.

                    The SLOSH formulation does not include a tide model within it. The reason
                 for this is the uncertainty in timing of tropical cyclones with respe       Ict to
                 the surface tide.   The second reason is that the SLOSH model is also used
                 in a forecast, . or - "atlas" mode, where the storm surge is simply added to the
                 corresponding tide.   The error in not including the tidal -calculation arises
                 in the finite amplitude terms, where the surface tide@may raise or lower the

                                              B-18

                       kGANSETT AND BUZZARDS SAYS

                          SLOSH BASIN

                                                                  V"w

                                                         w

               Source: Techniques Development Laboratory, National
                       Weather Service, Silver Spring, MD.

               FIGURE B.4: Polar Coordinate for Narragansett and Buzzards Bays
                              SLOSH Basin

                                                                             B- 19

                                            76*W                      741W                       72'W                        70*W
                                         44'N                                                                                   44*N

                                                               NEW YORK/

                                                         LONG ISLAND SOUND

                                                              SLOSH BASIN

                                         4M                                                                                     42*N

                                         40*N
                                                                                                                                40ON

                                         38*N                                                                                   38*N

                                             70*w                      74*W                       7L"W                       706W

                                          Source: Techniques Development Laboratory, National
                                                       weather Service, Silver Spring,'MD.

                                 FIGURE       B.5: Polar             Coordinate for New York/Long Isl                             and
                                                          Sound      SLOSH,Basin

                                                   B-20

               datum on which the storm surge acts. This should not be a major drawback
               -in the Connecticut, coastal area where tides are relatively low.

                  In application to the Connecticut coast, the SLOSH model has some problems
               inherent in it. Because of the shallow nature of Long Island Sound, the bottom
               friction formulation used in SLOSH will not correctly predict dissipation.
               Future improvements to SLOSH could include better representation of the physics
               of the bottom boundary layer, which could be done with no large increase in
               run costs.

                  If the SLOSH results do become available for the Connecticut coast as they
               should in the near future, careful comparison with observed storm surge should
               be carried out, and the source of any discrepancies identified. Bottom friction
               is one source which could be poorly represented by SLOSH, but locally advective
               effects could be important (they are ignored by SLOSH).

                  Another major concern in the Connecticut coast is the effect of Long Island
               on tropical cyclone passage.     As seen in the 1976 Hurricane Bell and 1985
               Hurricane Gloria, Long Island appears to have a major effect on the wind field
               of hurricanes. If the forecast winds were much larger than actual winds,
               hurricane surge would be overpredicted, with consequent increased expenses
               associated with evacuation.    This emphasizes the need for evaluation of the
               model locally, where the wind field around a hurricane becomes extremely complex.
               The 1938 hurricane and the 1985 Gloria would be useful examples against which
               to compare the wind stress, model and resulting storm surges.

                  The polar grid must be implemented carefully along Long Island Sound to
               assure a uniform grid.     Large alongshore differences in grid spacing would
               result in greater uncertainties in storm surge simulation in some areas than
               others. The State should consult with NWS when model simulations are run.

                       WAVE FORECASTING/BTNlDCASTING MQDYJA

                       Introduction

                  Wave forecasting    and hindcasting are accomplished by approximating the
               physics of wave generation and wave transformation by parametric or numerical
               methods. Although these. techniques date back quite a few years, the earliest
               publication in, book form of which is Sverdrup and Munk (209), recent advances
               in these techniques make them more reliable and accurate. Since these techniques
               are only approximate, they don't reproduce exactly the correct physics behind
               wave generation and transformation. Some of the techniques are more appropriate
               for deep water uses (such as the Navy's Fleet Numerical Weather Central wave
               model), while others do a much better job approximating physics of shallow
               water waves. Some require elaborate computers for calculation, and long compu-
               tation times, while others require only limited computation, being accomplished
               mainly by nomographs. Almost all methods use the synoptic wind field as input
               for calculations. Since the fine details of the synoptic wind field are not
               available, local variability in waves often is underestimated by these models.

                                                      B-21

                 B.2.2   Wave Model 3:ypes and Parameters

                    In general, wave models can be considered discrete or parametric.             The
                 discrete.models attempt to simulate the wave energy balance or transport equation
                 directly, with all of the wave generation (source) terms and the 'wave dissipation
                 (sink) terms. These models, dating back to Pierson et al. (210), have advanced
                 considerably over the past twenty years. They must all use some parameter-
                 ization or representation of the various source and sink terms to provide
                 adequate results.    In contrast, a class of models known as parametric wave
                 models have evolved from the initial work of Sverdrup and Munk, (209), in which
                 the major features of a wave are derived more simply (represented in nomograph
                 form by S-M), reducing computational cost. All rely to some degree on empiricism,
                 relating wave characteristics to the forcing terms (wind).

                    As might be pr   edicted, these two approaches have led to hybrid models,
                 where elements of discrete models ar  'e combined with elements of the parametric
                 models.   This hybrid approach can be used to describe different elements of
                 the wave field, or the wave field at different stages of development.          There
                 is considerable, ongoing debate over which of these two (or three) types of
                 models is most appropriate for shallow water conditions.

                    The COE for instance, historically has used a parametric approach, as described
                 in the Shore Protection Manual. Recently, however, they have been developing
                 a discrete wave model for use in shallow water.       Its performance has not yet
                 been tested completely with- field data.      In contrast, much recent work has
                 gone into improving pa   rametric wave models.     Several oil companies are now.
                 providing an intercomparison of the models to try to evaluate the performance
                 of the different models.     The results of an experiment in the early 1980's
                 (211) showed that the differences between model results 'are large, and not
                 explainable by uncertainties in meteorlogical conditions.         The debate will
                 continue as the proponents of. the different models continue their theoretical
                 development and comparison with field data (which are extremely sparse).

                    For the Long Island Sound case, a model should be selected*which will account
                 for finite depth effects, and not rely on deepwater relationships. Such models
                 exist in both a discrete and parametric form.        Very' important in the finite
                 depth case is a proper representation of the bottom friction term, as Well
                 as other sources and sinks'.    Given the variety of different models available,
                 the fact that they all yield 'results distinct from one another, and the fact
                 that there has been no definitive intercomparison because of lack of a good
                 data set, there is considerable latitude in selection of an appropriate wave
                 forecasting model.

                 B=      NWS Wave   Forecast Model

                    The National    Weather Service uses    a wind-wave forecast    f or generalized
                 offshore wave conditions. This wave forecast is of the parametric type, based
                 largely on empirical relationships between the size of waves generated by
                 specific winds.    It follows in the mold of the Sverdrup- Munk- Bretschneider
                 (SMB) type methodology first developed in 1947.        Three parameters required
                 to use these nomographs are wind soeedg fetch          length, and wind duration.
                 Each of these is discussed briefly below.

                                                        B-22

                    Wind speed suffers from need to specify average         wind speed over the fetch
                .of the storm and over the duration during which            it existed.    This specif i-
                cation is a primary weakness of the limited nomograpbs, since, the precise
                details of the averaging can affect the final result.             The wind' speed has
                to be adjusted for atmspberic boundary layer effects; thus wind cannot be
                input simply from. calculated geostrophic (or thermal) winds generated from
                synoptic pressure charts.        Details of this correction are generally ignored
                in most parametric forecasts of this type.

                    Fetch is the distance over which the "constant" wind has been ',blowing.
                 For an easterly wind in Long Island Sound, for instance, the fetch is much
                smaller in eastern Connecticut than in western Connecticut.              The definition
                of the fetch is determined by some subjective decisions about the size of
                the pressure system causing the winds, and other such matters. The definition
                of fetch therefore is far from exact.

                    The final term needed to apply these nomograms is the duration of the wind.
                This must be the representative time during which the wind speed has acted
                over theprescribed fetch.         Clearly these three parameters must be chosen
                carefully to make this simple forecast of wave conditions.

                    For the NWS purposes of providing marine forecasts for mariners, genera-
                lized wave forecasts may be adequate. However, since these            simple nomograph
                techniques ignore      all details of wave scattering and dissipation, they are
                not applicable to      forecasting wind waves for coastal localities.            Examples
                of the major areas     of omission in the nomograpbs include: no bottom friction         '
                no wave refraction, no wave reflection, no wave diffraction, lack of             inclusion
                of a time-variable    wind field and fetch length.        Again, these- omissions may
                not affect the generalized wave forecasting needs of NWS, but they are critical
                to the mission of accurately forecasting coastal wave fields.

                    For purposes of providing coastal flood warning to the reside       nts of a coastal
                reach, the NWS methodology is clearly inadequate. For best results, a numerical
                wave forecast model is required, which includes the full effects of dissipation
                and scattering.

                         Elements of a LIS Wave Model

                    The  important elements of a wave model to be          consid ered for LIS include:

                         Shallow water form
                         Appropriate form of bottom friction to          account for nonlinear losses
                         Inclusion of wave refraction/diffraction for    shallow water.
                         Proven performance and reliability
                         Reasonable performance in standard intercom pariso ns
                         Reasonable cost and efficiency
                         Appropriate and separate treatment       of both locally-generated and swell-
                         components.
                         Some spectral form to properly account for wave-wave interactions.

                    Based on a survey of the field 'and opinions of other oceanographers in
                the field, one excellent choice for providing LIS wave forecasts is the hybrid
                wind-wave model of Graber (105).

                                                   B-23

                   In this hybrid model, Graber uses the shallow water form of the wave equations,
                 applying the most advanced -friction estimates to correct for finite depth
                 effects, and incorporates refraction and shoaling.  This model has been run
                 for a variety of different locales, and a variety of different conditions,
                 with reasonable results.

                                                     C-1

                                  APPENDIX C: GLOSSARY OF ABBREVIATIONS

                  AFOS    Automation of Field Operations and Service
                  ALERT - Automated Local Evaluation in Real Time
                  ASERT - Automated State Evaluation in Real Time
                  BW - Bureau of Waterways (DOT)
                  CAFW - Committee on Automated Flood Warning
                  CERC- Coastal Engineering Research Center (Corps of Engineers)
                  COE -  U.S. Army Corps of Engineers (DOA)
                  CSP - Connecticut State Police
                  DEP -  Department of Environmental Protection (CT)
                  DOC -  Department of Commerce (US)
                  DOT -  Department of Transportation (CT)
                  EPA -  Environmental Protection Agency
                  FEMA  - Federal Emergency Management Agency
                  FIRM - Flood Insurance Rate Map
                  FIS - Flood Insurance Study
                  GOES - Geostationary Operational Environmental Satellite
                  IEMIS - Integrated Emergency Management Information System
                  LIS - Long Island Sound
                  MAPONY - Maritime Administration, Port of New York
                  MEOW- Maximum Envelope of Water
                  MHW - Mean High Water
                  MLLW - Mean Lower Low Water
                  MLW - Mean Low Water
                  MSL - Mean Sea Level
                  NAS - National Academy of Sciences
                  NAWAS - National Warning System
                  NERFC - Northeast River Forecast Center (NWS, NOAA)
                  NGVD- National Geodetic Vertical Datum (1929 datum)
                  NGWLMS - Next Generation Water Level Monitoring System
                  NMS - National Meteorological Center (NWS, NOAA, DOC)
                  NOAA - National Oceanic and Atmospheric Administration (DOC)
                  NOS - National Ocean Service (NOAA, DOC)
                  NRC - Natural Resources Center (DEP)
                  NWLON - National Water Level Observation Network
                  NWR - NOAA Weather Radio
                  NWS - National Weather Service (NOAA, DOC)
                  OCP - Office of Civil Preparedness (CT)
                  SCS - Soil Conservation Service (DOAg)
                  SIO - Scripps Institute of Oceanography
                  SLOSH - Sea, Lake and Overland Surges from Hurricanes
                  SPLASH- Special Program to List Amplitudes of Surges from Hurricanes
                  TDL - Techniques Development Laboratory (NWS, NOAA, DOC)
                  UCONN - University of Connecticut
                  UHF - Ultra High Frequency
                  USGS - U.S. Geological Survey (U.S. Dept. of the Interior)
                  VHF - Very High Frequency
                  WHOI - Woods Hole Oceanographic Institution
                  WRU - Water Resources Unit (DEP)
                  WSFO - Weather Service Forecast Office
                  WS 0 - Weather Service Off ice

                                                               D-1

                                                  APPENDIX D: REFER         ENCES

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                                                       D-2

               21.    Boutilier, Carl, Chief, Navigation Branchq New England Division, U.S. Army
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                                                         D-3

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                                                                D-4

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                                                                 D-5

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                  161.   Perlin, Mark, College of Engineering, University of Florida, Gainesville,
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