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



      Journal of Coastal Research         14          1            61-92           Royal Palm Beach, Florida        Winter 1998



Monitoring the Coastal Environment; Part IV:

Mapping, Shoreline Changes, and Bathymetric Analysis   4

Laurel Gormant, Andrew Morangt, and Robert Larsonï¿½

tU.S. Army Engineer              *U.S. Army Engineer              ï¿½U.S. Army Engineer                          . ,   ,  
 Waterways Experiment             Waterways Experiment             Waterways Expreriment         g
 Station                          Station                          Station                                      -
Information Technology           Coastal Engineering Research   Geotechnical Laboratory
 Laboratory                       Center                         Vicksburg, MS 39180, U.S.A.   I-
3909 Halls Ferry Road            3909 Halls Ferry Road
Vicksburg, MS 39180, U.S.A.    Vicksburg, MS 39180, U.S.A.

                      ABSTRACT
                      GORMAN, L.; MORANG, A., and LARSON, R., 1998. Monitoring the coastal environment; Part IV: Mapping, shoreline
       ï¿½,ee  ï¿½ ï¿½ee  Ee e changes, and bathymetric analysis. Journal of Coastal Research, 14(1), 61-92. Royal Palm Beach (Florida), ISSN 0749-
se-;          ,1~      0208.

 _______________ -This paper presents an overview of field methods, data collection, and analysis procedures applied to four key coastal
                      data sets used in monitoring and baseline studies: aerial photography, satellite imagery, profile surveys, and bathy-
                       metric (hydrographic) records. Often, aerial photographs and satellite images, after rectifying and georeferencing,
                       serve as base maps to interpret landform changes and quantify shoreline movement. Large-scale topographic and
                       hydrographic maps are the primary sources for shoreline position and volumetric change computations. Profile sur-
                       veys, available from many Federal and local agencies and universities, can also be used to evaluate shoreline changes
                       and compute beach volume changes along and across the shore. Frequently, post-processing steps are required to
                       normalize these data to the same coordinate system and vertical datum prior to quantifying changes for a coastal
                       area. For example, project-specific bathymetric data in the United States is often plotted using State Plane coordi-
                       nates, while hydrographic data from NOAA is supplied with latitude/longitude coordinates.
                         Maps, surveys, and aerial photographs are available from Federal agencies such as the USGS, NOAA, and the
                       Corps of Engineers. These long-term data records can be used to evaluate natural and man-made changes to a coastal
                       system. The resultant statistics and volumetric calculations should be presented in terms of the regional and local
                       conditions, i.e., storm history, seasonality, wave climate, man-made environmental and engineering changes, and
                       large- and small-scale landforms.

                       ADDITIONAL INDEX WORDS: Shoreline change, bathymetric mapping, grid models, triangular Irregular Network
                       models, cartographic software, depth of closure, geospatial methods.



                    INTRODUCTION                                                    AERIAL PHOTOGRAPHY
                                                                     Aerial photographs provide invaluable information for the
  This paper is the fourth in a series of four that discuss
                                                                   interpretation of geologic history. Aerial images can be ob-
techniques for measuring and analyzing coastal geologic and
                                                                   tained from Federal and state government agencies such as
engineering data. The focus of this paper is on mapping tech-ates Geological Survey (USGS)  the US. De-
nology and methods used to analyze shoreline change and 
                                                      o    a met se  te  partment of Agriculture, the EROS Data Center, and the U.S.
offshore bathymetric changes. These techniques are often             Army  Corps  of Engineers  (USACE)  (other Government
used by geologists and engineers who must evaluate the ef-           sources are listed in HE                USACE, 1995). tere-
fects of coastal structures on the adjacent shorelines or de-
cipher the morphologic history of a region based on historical       ographc  photograph pai rs wi th overlap of 60 percent are of-
maps and bathymetric data sets. Shoreline change data are            tained using photogrammetric techniques. Coverage for the
critical for coastal managers tasked with establishing setback       United States is available since the 1930's for most locations.
lines and guiding growth in the coastal zone, especially in          The types of analyses and interpretation that can be per-
low-lying areas subject to storm flooding. Volumetric analy-         formed depend in part on the scale of the photographs, the
ses based on bathymetric data are used to compute amounts            resolution, and the percentage of cloud cover. One of the
of sediment trapped by structures, growth of offshore shoals,        greatest advantages of aerial surveys is the ability of Federal
migrations of channel thalwegs, and dredging volumes. Vol-           and state agencies to rapidly mobilize photographic equip-
umetric analyses are also used to monitor the performance of         ment and aircraft and document the effects of major events
beach renourishment projects.                                        such as hurricanes or floods. Aircraft can cover large areas
                                                                   in a short time and can survey terrain that is not readily
96026-IV received 22 February 1996; accepted in revision 10 April    accessible from the ground. Clouds and haze are the two main
 1996.                                                                factors that reduce the quality of aerial photographs.





62                                                 Gorman, Morang and Larson


  For modern process studies, a series of aerial photographs      0 Radial lens distortion. With older aerial lenses, distortion
can provide much data for examining a variety of problems.          varied as a function of distance from the photo isocenter.
Information pertinent to environmental mapping and classi-          It is impossible to correct for these distortions without
fication such as the nature of coastal landforms and materi-        knowing the make and model of the lens used for the ex-
als, the presence of engineering structures, the effects of re-     posures (CROWELL, LEATHERMAN, and BucKLEY, 1991). If
cent storms, the locations of rip currents, the character of        overlapping images are available, digitizing the centers,
wave shoaling, and the growth of spits and other coastal fea-       where distortion is least, can minimize the problems.
tures can be examined on aerial photographs. For coastal            Fortunately, most errors and inaccuracies from photo-
morphological studies, it is generally preferable to obtain       graphic distortion and planimetric conversion can be quan-
photographs during low tide so that nearshore features aretiedOrhhoquragsan   toptmsicae
                expoed r patlyvisile hrouh te waer.Howeerthephotomaps made by applying differential rectification tech-             '
National Ocean Survey (NOS) prefers to map the mean high          niques (stereo plotters) to remove photographic distortions.
water line or high water line (mhwlihwl) using high-tide co-      Shoreline mapping exercises have shown that, if care is taken

 Forstdiesoenhsoialtied sclemutpessofagery  in all stages of filtering original data sources, digitizing data
                 Forstuiesove hitorcaltie sale, mltile etsof e-and performing distortion corrections, the resulting maps
rial photographs are required. Historical photographs and         meet, and often exceed, National Map Accuracy Standards
maps are integral components of shoreline change assess-(C OE LLATEMNanBuRY,19)
ments. Water level and, therefore, shoreline locations, show      (CWELLATRMNanBUKY,19)
great variation according to when aerial photographic mis- RMTL-ESDSTLIEDT
sions were flown. Therefore, coastal scientists should account            RMTL-ESDSTLIEDT
for such variations as potential sources of error in making or      Satellite imagery archives span broad areas of the globe
interpreting shoreline change maps.                               and include regular coverage of most coastlines in all weather
  Air photographs, which are not map projections, must be         and seasons. Much of the existing data has a resolution of 10
corrected by optical or computerized methods before shore         mn or greater. However, despite the coarse resolution (in com-
positions compiled from the photos can be directly compared       parison with film-based aerial photographs), satellite digital
with those plotted on maps. The distortion correction proce-      data may assist in understanding large-scale phenomena, es-
dures are involved because most photos do not contain de-         pecially processes which are indicators of geologic conditions
fined control points such as latitude-longitude marks or tri-     and surface dynamics. Remote sensing data are also exten-
angulation stations'. On many images, however, secondary          sively used in wetlands research to monitor changes in flora,
control points can be obtained by matching prominent fea-         drainage patterns, and hazardous waste discharges (LAmp-
tures such as the corners of buildings or road intersections      ivAN, 1993). With modern processing equipment, remote
with their mapped counterparts (CROWELL, LEATHERMAN,              sensing data can be downloaded, processed, and manipulated
and BUCKLEY, 1991). Types of distortion which must be cor-        easily and quickly.
rected include:                                                     Satellite data are available from U.S. agencies, the French
                ï¿½   Tlt.Almst   llverica aeia phtogaph ae tlte, wthSysteme Pour L'Observation de la Terre (SPOT) satellite
                * Tlt.Almst ll ertcalaeral hotgrahs  re iltd, ith data network, and from Russian (Soviet) archives. In most
  I degree being common and 3 degree not unusual (LILLE-         instances, the data can be purchased either as photographic
                  SANDandKIEER,1987.    Te  saleacrss tlte ai phtospaper copy or in digital format for use in computer applica-
  is non-orthogonal, resulting in gross displacement of fea-     tions. Numerous remote sensing references are listed in
  tures depending upon the degree of tilt.LmmN   19)Alitnofseltedamitiedb
* Variable scale. Planes are unable to fly at a constant alti-    theMN (93.alitionalo Spacellinter Data mainteraSD s ine  Hoy
                  tude Threfreeac phtogaph n aseres aris i scle.ROWiTZ and KING (1990). This data can be accessed electron-
  Zoom transfer scopes or cartographic software can be used      ically. NELSON (1994) lists names and addresses of Govern-
  to remove scale differences between photos.                     ment and private vendors of remote sensing imagery.
ï¿½ Relief displacement. Surfaces which rise above the average        Satellite data are especially useful for assessing large-scale
  land elevation are displaced outward from the photo iso-        changes across the coastal zone. In the vicinity of deltas, es-
  center. Fortunately, most U.S. coastal areas, especially the    tuaries, and other sediment-laden locations, spatial patterns
  Atlantic and Gulf barriers, are relatively flat and distor-     of suspended sediment can be detected with remote sensing
  tion caused by relief displacement is minimal. However,         (Figure 1). In shallow non-turbid water bodies, some features
  when digitizing dliffed shorelines, control points at about     of the offshore bottom, including the crests of submarine bars
  the same elevation as the feature being digitized must be       and shoals, can be imaged. The spatial extent of tidal flows
                  selected. ~~~~~~~~~~may be determined using thermal infrared data, which can
                                                                 be helpful in distinguishing temperature differences of ebb
  1For low-altitude aerial surveys, monuments and other triangu-  and flood flows and freshwater discharges in estuaries. In
lation points can be flagged with markers (triangles or plastic or  deeper waters, satellites provide data on ocean currents and
cloth strips) that are large enough to be visible on the resulting pho-  circulation (BARRICK, EvAxws, and WEBER, 1977).
tographs. This is a necessary procedure for highest accuracy photo-  The Landsat satellite program was developed by the Na-
mapping, although flagging is an expensive procedure because of the
many field crews that have to be on standby waiting for optimum   tional Aeronautics and Space Administration in cooperation
flight conditions.                                                with the U.S. Department of the Interior. Landsat satellites



                                          Journal of Coastal Research, Vol. 14, No. 1, 1998






                                       Monitoring Coastal Environments: Geospatial Methods                                  63














































Figure 1. NOAA AVHRR satellite image from February 24, 1990, showing plume of cold water emerging from Choctawhatchee Bay, Florida (from
MoRANG, 1993). Image processed at the Earth Scan Laboratory, Louisiana State University, Baton Rouge.


have used a variety of sensors with different wavelength sen-      0.50-0.59pum; red: 0.61-0.69 pm-and  one near infrared
sitivity characteristics, ranging from the visible (green) to the  band: 0.79-0.89 pm). For coastal studies, SPOT images have
thermal infrared with a maximum wavelength of 12 microm-           been used to detect suspended sediment, indicative of runoff
eters (>m). Figure 2 shows bandwidths and spatial resolution       and coastal currents (Figure 3). SPOT 1 and 2 are in sun-
of various satellite sensors. Of the five Landsat satellites,      synchronous orbits of 832 km and orbit the earth once every
only Landsat 4 and Landsat 5 are currently in orbit. Both are      101 min. This provides full earth coverage between 72ï¿½ N and
equipped with the multispectral scanner, which has a reso-         72ï¿½ S every 26 days.
lution of 82 m in four visible and near-infrared bands, and          Several generations of satellites have flown in the National
the thematic mapper, which has a resolution of 30 m in six         Oceanic and Atmospheric Series (NOAA) series. The most re-
visible and near- and mid-infrared bands and a resolution of       cent ones contain the Advanced Very High-Resolution Radi-
120 m in one thermal infrared band (10.4-12.5 jim).                ometer (AVHRR). This provides increased aerial coverage but
  SPOT is a French commercial satellite program. The first         at much coarser resolution than the Landsat or SPOT satel-
satellite, SPOT 1, launched in 1986, has two identical sensors     lites. More information on the wide variety of satellites can
known as HRV  (high-resolution-visible) imaging systems.           be found in textbooks on remote sensing (COLWELL, 1983;
Each HRV can function in a 10-m resolution panchromatic            LILLESAND and KIEFER, 1987; RICHARDS, 1986; SABINS,
mode with one wide visible band (0.51-0.731xm), or a 20-m          1987; STEWART, 1985). Many defense contractors are bring-
resolution multispectral mode (two visible bands-green:            ing to the civilian market powerful, formerly restricted, map-



                                            Journal of Coastal Research, Vol. 14, No. 1, 1998






64                                                   Gorman, Morang and Larson




                                        LANDSAT
                                                                                                            NOAA
                      Multispectral      Thermatic    Panchromatic       SPOT                         Advanced Very High
                     Scanner (MSS)      Mapper (TM)   Band on         High Resolution             Resolution Radiometer (AVHRR)
                    Landsats 1,2,3,4,5   Landsot 4,5,6  Landsat 6      Visible (HRV)                NOMAA 6,8,10   NOAA 7,9,11
           .4
                        80m   i.-30m-                  15m-22  H210m                           1.1 km
           .5                          [7. Blue. eBond   _
                    *ï¿½ '..''Band 1-                     Band  1       _l..
                    ..... Green .'               |.       . Band 2  Band 1       E
                     Bond2 .                                      Bnd 2                       i1
                    .....  Red        .        Band 3         Bond 2      ......     .
           .7 -B                                                    2
                   '9 Bond 3                             ...                    a-
                   --  .. Near-Infrared                  ....                                   .                 .
           .8                           Near-
                             .........  Infrared Band 4.       Band  3
                   .9. Ban                  d  4 ..    d ....
                    .' ' Neor-lnfrared '.'.'
                             1.0  ---- ..'.' '  ' '  ' ' '. ' ..' 
          1.                           ......


         v)    1.65 -_      Band 6                        Areas of Coverage
  c)                      Mid-Infrared                             185 km
  e>  1.75                                                  ..            ...

  o 2.0                          1                                -k ..
  oE                                                    2.1                          -_ ...... 170k m~l .. ..O km ~ Landsat Image Area
      2.1                                                               60km

  o                       Mi-2.I2n- Band 7                *     .......            SPOT Image Area
  .                       Mid-Infrare d
 :3   2 32.3....

  Wi/    2.4
 r'r
         3.5
       3.6 --
       3.7 --
          3.8 --
          3.9 --

         4.0
        10.0                                      120 m
                                             Spatial Resolution
        10.5 --                        '.....''.... .... ..................


                                       .......... Band 6.........
        11.0 --                        ...'. Thermal Infrared  I..I
                                       12.0-    - .................                             .       Band 5
                                        . . . . . . . . ... .   .                                  ..   .   . . . .
        12.0 --  .......................

        12.5                                  ..................

Figure 2. Spectral resolution and approximate spatial resolution of sensors on Landsat, SPOT, and NOAA satellites (from Earth Observation Satellite
Company literature and HUH and LEIBOWITZ, 1986).



ping and display technologies (EOM  STAFF,  1994; Mc-                systems have been tested for mapping the bottom topography
DONALD, 1995). Time will tell how many of these ventures             of coastal waters.
are commercially viable, but many show tremendous poten-               A LIDAR system, known as SHOALS (Scanning Hydro-
tial in coastal geological and ecological studies.                   graphic Operational Airborne Lidar Survey), is now being
  Aircraft-mounted scanners, including thermal sensors and           used by the Corps of Engineers to survey coastal areas and
radar and microwave systems, also have applications in               inlets. The system is based on the transmission and reflection
coastal studies. LIDAR (Light Detection and Ranging), SLAR           of a pulsed coherent laser light from a helicopter equipped
(Side-Looking Airborne Radar), SAR (Synthetic Aperture Ra-           with the SHOALS instrument pod and with data processing
dar), SIR (shuttle imaging radar), and passive microwave             and navigation equipment (LILLYCROP and BANIC, 1992; Es-



                                            Journal of Coastal Research, Vol. 14, No. 1, 1998






                                       Monitoring Coastal Environments: Geospatial Methods                                     65














































Figure 3. SPOT satellite image, Atchafalaya Bay, Louisiana. Suspended sediment from runoff is clearly visible. Data processed by the Earthscan
Laboratory, School of Geosciences, Louisiana State University, Baton Rouge.



TEP, LILLYCROP, and PARSON,  1994). In  operation, the               quickly, allowing broad-area post-storm surveys or surveys of
SHOALS laser pulses 200 times per second and scans an arc            unexpected situations such as breaches across barriers. For
across the helicopter's flight path, producing a survey swath        instance, SHOALS surveyed portions of the Florida Panhan-
equal to about half of the aircraft altitude. A strongly reflect-    dle within a week after Hurricane Opal crossed the coast in
ed light return is recorded from the water surface, followed         October, 1995 (Figure 4). Finally, SHOALS can survey di-
closely by a weaker return from the seafloor. The difference         rectly from water through the surf zone and across the beach;
in time of the returns corresponds to water depth. SHOALS            this allows efficient coverage of shoals, channels, or breaches
may revolutionize hydrographic surveying in shallow water            that would normally be impossible or very difficult to survey
for several reasons. The most important advantage is that            using traditional methods, especially in winter. Maximum
the system can survey up to eight square km per hour, there-         survey depth is proving to be over 30 m, depending on water
by densely covering large stretches of the coast in a few days.      clarity. Because of the immense amount of data that the
This enables almost instantaneous data collection along              SHOALS  system collects, data processing, archiving, and
shores subject to rapid changes. The system can be mobilized         management is proving to be a challenge.


                                           Journal of Coastal Research, Vol. 14, No . 1, 1998
                                - _  =  3t2S~~~~~~~~~~~"~~f~~
                                    - - A i m  5 I~~~~~~~~~~~~~~~~~e X~~~~~~~g - - , ï¿½ W    F i r   z =~~~~~~~~~~~~~~~~~~~~~i


           1U                                                                                    -liï¿½--ï¿½ ;~t











































                                           Journal of Coastal Research, Vol. 14, No. 1, 1998






66                                                   Gorman, Morang and Larson



                                no                   mo                    m                     mo
                                Co                   Xo                     W                    C.o
                                     Coo                                   co                    o
                                     S~~~ ï¿½
                                a                     0                    0                     0

                      NS13000   +          +          +          +          +          +          +    N513000







                                +5 1   "1000  <:7                                                      N511000
                                                                    ~.






                      NSIIOOO    +++                                                              +     N509000





                                             +  +,             '4< ~~~~"-'4gatt+ so+oo

                      N507000   +          +         4~~    92             A<          +          +  N507000

                                 East Pass, FL          !     : :
                                 Oct. 10, 1995    .
                                 Post-Hurricane Opal



                                                                                o~~~~~~~~~C
                                        _W~~~~~~~~~~~~~~~~~~~~~-
                                o~                                                               m
                                                                           co                   co
                                o                                                                o

Figure 4. SHOALS helicopter LIDAR bathymetry survey tracklines at East Pass, Destin, Florida, flown on October 10, 1995, only six days the passage
of Hurricane Opal. The coverage includes over 200,000 individual depth values. Arrowhead jetties mark the mouth of East Pass inlet.


    TOPOGRAPHIC AND BATHYMETRIC DATA                                of the U.S. Coast and Geodetic Survey (USC&GS). U.S. Geo-
                                                                    logical Survey topographic maps are generally revised every
  Topographic and hydrographic maps are available from
                  Toporaphc an  hydograhi&mapsare  vailble  rom     20 to 30 years, but sometimes more often in high-priority
the USGS, many Corps of Engineers District Offices, and the          20 to 30 years, but sometimes more often in high-priority
                       . '  a .  ar.   ..............  .  . '   ....areas. Nevertheless, the maps are sometimes outdated be-
National Ocean Service (NOS), which includes the archives            areas. Nevertheless, the maps are sometimes outdated be-
                                                                    cause of the ephemeral nature of many coastal landforms.
                                                                    The maps are created at a range of scales from 1:24,000 to 1:
 2The term topographic usually refers to the shape and form of the  250,000 (ELLIS, 1978), with the most common being the 7ï¿½'
dry land portions of the earth (from the Greek topos, "a place").    (minute) series (scale 1:24,000) and a 15' series (scale 1:
Bathymetric and hydrographic, often used interchangeably, describe
the morphology of the seafloor. However, NOAA makes a subtle dis-    62,500). Their purpose is to portray the shape and elevation
tinction: a bathymetric chart depicts water depths, contour lines,   of the terrain above a given datum, usually the mean high
and gradient tints, whereas a hydrographic chart emphasizes water    water line. The resolution of these maps is typically inade-
measurements showing submarine features and the adjacent coastal     quate to provide details of coastal surface features but are
areas with respect to navigational use (BowDITCH, 1981). The dis-   
tinction between the terms map and chart are based on usage, with    sufficient for exam     g regonal landforms and pronounced
chart being a product constructed for use in marine navigation       local changes, particularly over long periods.
(SHALowiTz, 1964).                                                     Recent and historical hydrographic survey data for the



                                            Journal of Coastal Research, Vol. 14, No. 1, 1998





                                       Monitoring Coastal Environments: Geospatial Methods                              67


United States marine coasts and Great Lakes are available       and sediment grain size (BRUUN, 1954; DEAN, 1976, 1977,
from the NOS. Much of this data can be obtained in the form     1990; PILKEY et at., 1993). Therefore, the active portion of the
of preliminary plots that are of larger scale and contain more  shoreface varies in width throughout the year depending on
soundings and bottom notations than the published charts        wave conditions. In effect, "closure" is a time-dependent
made from them. Surveys since about 1930 are available in       quantity that may be predicted based on wave climatology or
digital form from the National Geophysical Data Center in       may be interpreted statistically using profile surveys.
Boulder, Colorado. For older surveys, a user must purchase        The energy-dependent nature of the active portion of the
photographic reproductions of T-sheets (topographic) or         shoreface also requires us to consider return period. The clo-
H-sheets (hydrographic) from the NOS and digitize them          sure depth that accommodates the 100-year storm will be
himself.                                                        much deeper than one that merely needs to include the
  Bathymetric survey maps are sometimes out of date be-         10-year storm. Therefore, the choice of a closure depth must
cause geomorphic changes in many submarine areas occur          be made in light of a project's engineering requirements and
rapidly. On some navigation charts, the bathymetry may be       design life. For example, if a berm is to be built in deep water
more than 50 years old and the marked depths may be quite       where it will be immune from wave resuspension, what is the
different than actual depths. The greatest changes are likely   minimum depth at which it should be placed? This is an im-
to be in areas of strong current activity, of strong storm ac-  portant question because of the high costs of transporting
tivity, of submarine mass movement, and of dredging near        material and disposing of it at sea. It would be tempting to
ship channels. The user must also be aware of changes in the    use a safe criteria such as the 100- or 500-year storm, but
datums used in different maps (to be discussed later in this    excessive costs may force the project engineer to consider a
paper). The Corps of Engineers surveys most Federal navi-       shallower site that may be stable only for shorter return pe-
gation projects annually to determine if the channels meet      riod events.
project specifications. These surveys sometimes extend over       Two methods are commonly used to predict closure depth.
the ebb and flood shoals of inlets and along the adjacent       One is predictive, based on wave data collected at the site
shores.                                                         over time. HALLERMEIER (1977, 1978, 1981a, 1981b, 1981c),
                                                                 using laboratory tests and limited field data, introduced
   BRIEF DISCUSSION OF DEPTH OF CLOSURE                         equations to predict the limits of extreme wave-related sed-
                                                                 iment movement. This paper is not the appropriate forum to
  Depth of closure is a concept that is often misinterpreted    review the formulas in detail; they are summarized in HEAD-
and misused. For engineering practice, depth of closure is      QUARTERS, USACE (1995), and the reader is urged to read
commonly defined as the minimum water depth at which no         Hallermeier's original papers to understand his assumptions
measurable or significant change in bottom depth occurs         and interpretations.
(STAUBLE et al., 1993). The word significant in this definition   When surveys covering several years are available for a
is important because it leaves considerable room for inter-     project site, closure is best determined by plotting and ana-
pretation. "Closure" has erroneously been interpreted to        lyzing the profiles. The closure depth computed in this man-
mean the depth at which no sediment moves on- or offshore,      ner reflects the influence of storms as well as of calmer con-
although numerous field studies have verified that much sed-    ditions. KRAUS and HARIKAI (1983) evaluated the depth of
iment moves in deep water (WRIGHT et al, 1991). Another         closure as the minimum depth where the standard deviation
complication is introduced by the fact that it is impossible to  in depth change decreased markedly to a near-constant val-
define a single depth of closure for a project site because "clo-  ue. Using this procedure, they interpreted the landward re-
sure" moves depending on waves and other hydrodynamic           gion where the standard deviation increased to be the active
forces.                                                         profile where the seafloor was influenced by gravity waves
  For the Atlantic Coast of the United States, closure depth    and storm-driven water level changes. The offshore region of
was often assumed to be about 9 m (30 ft) for use in engi-      smaller and nearly constant standard deviation was primar-
neering project design. However, at the Field Research Fa-      ily influenced by lower frequency sediment-transporting pro-
cility in Duck, North Carolina, BIRKEMEIER (1985) calculated    cesses such as shelf and oceanic currents (STAUBLE et al.,
closure as deep as 6.3 m relative to mean low water using       1993). Note that the smaller standard deviation values fall
surveys conducted from the Corps of Engineers' Coastal Re-      within the limit of measurement accuracy. This suggests that
search Amphibious Buggy (CRAB). STAUBLE et al. (1993) ob-       it is not possible to specify a closure depth unambiguously
tained 5.5 to 7.6 m at Ocean City, Maryland, from profile       because of operational limits of present offshore profiling
surveys. Obviously, it is invalid to assume that "closure" is a  hardware and procedures.
single fixed depth along the eastern United States.               An example of how closure was determined empirically at
   Closure depth is used in a number of applications such as     Ocean City, Maryland, is shown in Figure 5. A clear reduction
the placement of mounds of dredged material, beach fill,        in standard deviation occurs at a depth of about 18 to 20 ft
placement of ocean outfalls, and the calculation of sediment    (- 6 m). Above the - 18-ft depth, the profile exhibits large
budgets.                                                        variability, indicating active wave erosion, deposition, and lit-
   Closure is related to energy factors at coastal sites. The    toral transport. Deeper (and seaward) of this zone, the lower
primary assumption behind the concept of the shoreface equi-    and relatively constant deviation of about 3 to 4 inches (8 to
librium profile is that sediment movement,and the resultant     10 cm) is within the measurement error of the sled surveys.
 changes in bottom elevation are a function of wave properties   Nevertheless, despite the inability to precisely measure sea-



                                           Journal of Coastal Research, Vol. 14, No. 1, 1998





68                                                  Gorman, Morang and Larson



                       20                                                                            S
                                                                           74th Street
                                                                                                  -7
                        10-
                                       o                                                           ~~~~~~~~~~~~~~~~~~~~~~~~-6
                   C..D  o
                   z                                                                                -5  .a
                                        '4-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.+
                                                                                                   -4  Q)


                   .> c2
                    oJ                                                                                 -2
                      -3 0 -


                      -40 0
                          0        500       1000       1500      2000      2500       ' 3000    3500
                                                 Distance Offshore, ft
Figure 5. Profile surveys and standard deviation of seafloor elevation at Ocean City, Maryland (from STAUBLE et l., 1993). Surveys conducted from
1988 to 1992. Large changes above the datum were caused by beach fill placement and storm erosion.


floor changes in this offshore region, it is apparent that less    would be a conservative value, but only with respect to the
energetic erosion and sedimentation take place here than in        hydrologic conditions that occurred during the survey pro-
water shallower than   - 18 ft. This does not mean that there      gram. Presumably, if lake level dropped further at a later
is no sediment transport in deep water, just that sled surveys     date, sediment movement might occur deeper on the shore-
are unable to measure it. For the 5.6 km of shore surveyed         face. This suggests that closure on the lakes should be chosen
at Ocean City, the depth of closure ranged between 18 and          to reflect the lowest likely water level that is expected to occur
25 ft (5.5 to 8.5 m). Scatter plots indicated that the average     during the life of a project. (Note that this consideration does
closure depth was 20 ft (6 m).                                     not arise on ocean coasts because year-to-year changes in rel-
  Presumably, conducting surveys over a longer time span at        ative sea level are minor, well within the error bounds of sled
Ocean City would reveal seafloor changes deeper than   - 20        surveys. Sea level does change throughout the year because
ft, depending on storms that passed the region. However,           of thermal expansion, freshwater runoff, wind set-up, and
STAUBLE et al. (1993) noted that the "Halloween Storm" of          other factors, but the multi-year mean is essentially stable.)
October 29 to November 2, 1991, generated waves of peak            In summary, determining closure depth in the Great Lakes
period (Tp) 19.7 sec, extraordinarily long compared to normal      is problematic because of changing water levels, and more
conditions along the central Atlantic coast. Therefore, the        research is needed to develop procedures that accommodate
profiles may already reflect the effects of an unusually severe    these non-periodic lake level fluctuations.
storm.
  Figure 6 is an example of profiles from St. Joseph, Michi-                MAP DATUMS, CORRECTIONS, AND
gan, on the east shore of Lake Michigan. Along Line 14, dra-                         SOURCES OF ERROR
matic bar movement occurs as far as 2,500 ft (560 m) offshore
to a depth of -25 ft (-7.6 m) with respect to International
Great Lakes Datum (IGLD) 1985. This is where an abrupt               A datum is an established reference level or position that
decrease in standard deviation of lake floor elevation occurs      can be used as a basis of comparison for surveying or mea-
and can be interpreted as closure depth. In September, 1992,       surement purposes (HEADQUARTERS, USACE, 1994). For
the mean water surface was 1.66 ft above IGLD 85. There-           coastal engineering and geologic studies, both horizontal
fore, closure was around 26-27 ft (8 m) below water level.         (geographic location) and vertical (distance above sea level or
  In the Great Lakes, water levels fluctuate over multi-year       other surface) datums must be established:
cycles. This raises some fundamental difficulties in calculat-       First, specific features of a project site must be correctly
ing closure based on profile surveys. Presumably, during a         located in horizontal position on the face of the earth, es-
period of high lake level, the zone of active sand movement        pecially when recent measurements are to be compared to
would be higher on the shoreface than during a time of low         ones collected decades ago. Several map projections are in
lake level (assuming similar wave conditions). Therefore, the      common use. For convenience in data entry and manipula-
depth where superimposed profiles converge should reflect          tion, many Corps of Engineers project maps are plotted on
the deepest limit of active shoreface sand movement. This          rectangular grids such as the State Plane Coordinate System.



                                          Journal of Coastal Research, Vol. 14, No. 1, 1998





                                       Monitoring Coastal Environments: Geospatial Methods                                   69




                                                        STJOE 1 4


           0                                                                                                        6
                                                                                              LEGEND
                                                                                          Si  14 910814 1810
                            .,//,,-,'A                                               .......... Sd 14 910827 112
         -10-                                     S---- 1. 14 920518 1030
                                                                                    --...  Sd 14 920616 1233  - 5
                                                                                    -    SJ 14 930505 930
                                       -(\ N,   ......., .    ....'>..........              Si 14 930811 520    -
         -20 -                           ï¿½\'., ....'"~x~it 'C,"-                     ....    SD  1 940318 1458

                                             'r%%~~~~~~~~~-'< ".J"--.'                  .         . \                 "

       '-30--                                                        "...

                                                                                                                 -3

       -4-                                                                                                            40





                                                    "~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ VA
         -                                                    -70 ,
                                          I          it
                              A--/             // 
                     -4~ ~ ~ ~~~~i
                                          It'~~~~~ I             it 
                         i',~~~I                             -    I        -                                           Cl
              -60~~~~~~~          -' ,                       I   's. *

         -50               ,'                 /              1    i 0




             0          500         1000         1500         2000 2500000 3500 4000
                                                        Distance (ft)

Figure 6. Profile surveys and standard deviation of lake floor elevation at St. Joseph, Michigan, on the east shore of Lake Michigan. Profiles are
referenced to International Great Lakes Datum (IGLD) 1985. Surveys conducted between 1991 and 1994.




A separate grid has been established for each state, with the tional datums have been lost. ELLIS (1978) and CAMPBELL
larger states divided into several zones. This system uses rec- (1991) discuss details of projections and various grid systems.
tilinear coordinates with uniform x- and y- dimensions so The second datum of critical importance in coastal studies
that surveyors do not have to take into account the curvature is the horizontal surface to which all vertical measurements
of the earth in their calculations. The simplification is ac- are referenced. When computing sediment volumes or ex-
ceptable for local surveys because the introduced error is amining changes in shorelines or bottom configuration, all
small (CAMPBELL, 1991). These charts are referred to either data must be corrected to a common datum. For North Amer-
the North American Datum of 1927 (NAD27) or the North ican coastal engineering projects, normally two types of hor-
American Datum of 1983 (NAD83) (HEADQUARTERS, USA-                  izontal datums have been considered: those pertaining to
CE, 1994; U.S. GEOLOGICAL SURVEY, 1989). Charts covering open water, ocean coasts, and those pertaining to the Great
larger areas, particularly when they cross state boundaries' Lakes. Studies in other lakes or in reservoirs may use local,
use latitude/longitude coordinates or metric dimensions unique datums.
based on a non-uniform projection (e~g., Mercator). Mapping Sea Level                             /  Tid   Dat
computer software can convert spatial data from one horizon-SeLvlorTdlDtm
tal coordinate s ystem to another. Note that the conversion           In t he 1800's, mean sea l evel (ofsl) was adopted as a pri-
can be difficult for old maps if they do not specifically stat e mary datum because it was believed that ysl could be  accu-
what coordi           nate                   system was used. Another difficulty arises rately determined f rom    ti de gauge records. Over time, other
wh       en project maps use a local rectangular grid a nd the   re- datums became established for spe cific needs or for certain
cords th at describe the relationship of the  l     ocal  grid to h a- geographic regions.  The  most      important for navigation-relat-



                                           Journal of Coastal Resear                            ch, Vol. 14,   No. 1, 1998





70                                                        Gorman, Morang and Larson


                                                                         These are based on combinations of other datums (eg., mean
    3.0                                       Higher High Tid              low gulf (mlg) for the Gulf of Mexico), or on local measure-
       2.5    Higher        High Tide        I          I                  ments of water level over different periods (SWANSON, 1974).
                               Lower High Tide                            Because of varying relative sea level in many areas, tidal
                                  2  \I                                  datums are constantly changing and require continuous mon-
g  2.0                           /      '    |         /                   itoring and updating. Formal definitions of standard tidal da-
               >  1.5   \       l        \   |   |   l/  |                 tums for the United States are officially promulgated in
                               o  \4 I     \\   I  /[   IHICKS (1984). Figure 7 and Table 1 illustrate and define ter-
   1.0                         /                      I   I                minology used to describe water levels at an Oregon bay.
                             / \   /       Higher Low Tide
aX  0.5           8         /                L  j\                         The National Geodetic Vertical Datum (NGVD)
    m0.0O          i\ u             Mean Lower Low Water (MLLW)   -           The NGVD is a national fixed datum. It was established in
                                                                        the 1920's because of the need to compare land elevations at
                                                                         sites where there were no tide gauges or at interior sites far
                  Lower Low Tide    |   [   |   |   |   |   [             from the ocean. Because it was desirable to have the zero of
   -1.o
      o   2.  4   6   8  1'0  12  14  16  18  20  22  24  26  28          the geodetic leveling net coincide with local sea level across
                                 Hours                                   much of the North American continent, NGVD was adjusted
Figure 7. Tide curve for Yaquina Bay, Oregon (based on 6 years of ob-      in 1929 according to tide records from 26 selected United
servations). By definition, mean lower low water (mllw) is zero (from OR-  States and Canadian tide stations. The reference level de-
EGON, 1973).                                         .... fined in this manner was called the NGVD, 1929 adjustment
                                                                         (NGVD 29), and has been used as a primary datum for en-
                                                                         gineering design in the United States (HEADQUARTERS,
ed activities are mean low water (mlw) for the Atlantic coast              USACE,  1989). Note that NGVD  29 is not equal to mlw or
and mean lower low water (mllw) for the Pacific coast (HEAD-               mllw. Information is available from NOAA to relate NGVD
QUARTERS, USACE, 1989). These are defined as the average                   29 to tide curves at bays, inlets, and harbors around the coun-
height of the tide at low water (diurnal coasts: the Atlantic)             try. It is important to remember that two charts or two sets
or lower low water (semi-diurnal coasts: the Pacific) when all             of hydrographic data, one based on NGVD, and another on a
tides for a 19-year period are considered. The specific 19-year            tidal datum, can not be directly compared without making
cycle is known as the National Tidal Datum Epoch. Some                     the appropriate vertical correction. During the 1980's, NOS
areas of the United States have established regional datums.               conducted a major survey and analysis effort to relevel the


Table 1. Tidal datums and definitions, Yaquina Bay, Oregon.'

Tide (m)                                                          Datum and Definition
 4.42   Extreme high tide. The highest projected tide that can occur. It is the sum of the highest predicted tide and the highest recorded storm surge.
          Such an event would be expected to have a very long recurrence interval. In some locations, the effect of a rain-induced freshet must be
          considered. The extreme high tide level is used for the design of harbor structures.
 3.85   Highest measured tide. The highest tide observed on the tide staff.
 3.14   Highest predicted tide. Highest tide predicted by the Tide Tables.
 2.55   Mean higher high water. The average height of the higher high tides observed over a specific interval. Intervals are related to the moon's
          many cycles, ranging from 28 days to 18.6 years. The time length chosen depends upon the refinement required. The datum plane of mhhw
          is used on NOS charts to reference rocks awash and navigation clearances.
 2.32   Mean high water. The average of all observed high tides. The average is of both the higher high and of the lower high tide recorded each day
          over a specific period. The datum of mhw is the boundary between upland and tideland. It is used on navigation charts to reference topo-
          graphic features.
 1.40   Mean tide level. Also called half-tide level. A level midway between mean high water and mean low water. The difference between mean tide
          level and local mean and sea level reflects the asymmetry between local high and low tides.
 1.37   Local mean sea level. The average height of the water surface for all tide stages at a particular observation point. The level is usually deter-
          mined from hourly height readings.
 1.25   Mean sea level. A datum based upon observations taken over several years at various tide stations along the west coast of the United States
          and Canada. It is officially known as the Sea Level Datum of 1929, 1947 adj. Msl is the reference for elevations on U.S. Geological Survey
          Quadrangles. The difference between msl and local msl reflects many factors ranging from the location of the tide staff within an estuary
          to global weather patterns.
 0.47   Mean low water. Average of all observed low tides. The average is of both the lower low and of the higher low tides recorded each day over a
          specific period. The mlw datum is the boundary line between tideland and submerged land.
 0.00   Mean lower low water. Average height of the lower low tides observed over a specific interval. The datum plane is used on Pacific coast
          nautical charts to reference soundings.
-0.88   Lowest predicted tide. The lowest tide predicted by the Tide Tables.
-0.96   Lowest measured tide. Lowest tide actually observed on the tide staff.
-1.07   Extreme low tide. The lowest estimated tide that can occur. Used by navigation and harbor interests.
'Based on six years of observations at Oregon State University marine science center dock
From OREGON (1973)



                                               Journal of Coastal Research, Vol. 14, No. 1, 1998






                                      Monitoring Coastal Environments: Geospatial Methods                                  71


Table 2. Low water (chart) datum for IGLD 1955 and IGLD 1985.      national Great Lakes Datum (ILD) 1985. This datum, es-
                                                              tablished and revised by the Coordinating Committee on
                                         Low Water Datum       Great Lakes Basic Hydraulic and Hydrologic Data, replaced
                                            in Meters          IGLD 1955 in January, 1992. The main differences between
                                         IGLD     IGLD         IGLD 1955 and IGLD 1985 are corrections in the elevations
                Location                   1955     1985         assigned to water levels (Table 2). This is a result of bench-
Lake Superior                                182.9    183.2        mark elevation changes due to adjustments for crustal move-
Lake Michigan                                175.8    176.0
Lake Michigan                               175.8    176.0         ments, more accurate measurement of elevation differences,
Lake Huron                                   175.8    176.0
Lake St. Clair                               174.2    174.4        a new reference zero point location, and an expanded geodetic
Lake Erie                                    173.3    173.5        network. The reference zero point of IGLD 1985 is at Ri-
Lake Ontario                                  74.0     74.2        mouski, Qu6bec (Figure 8). The new 1985 datum establishes
Lake St. Lawrence at Long Sault Dam, Ontario  72.4     72.5        a set of elevations consistent for surveys taken within the
Lake St. Francis at Summerstown, Ontario      46.1     46.2
Lake St. Louis at Pointe Claire, Qu6bec       20.3     20.4        time span 1982-1988. IGLD 1985 is referred to NAVD 1988.
Montrdal Harbour at Jetty Number 1             5.5      5.6        Note that the IGLD's are not parallel to NGVD 29 or NAVD
               From COORDINATING COMMITTEE ON GAT LAs BAs  HYDRAuic  1988 because the Great Lakes datums are dynamic or geo-
From COORDINATING COMMITTEE ON GREAT LAKES BASIC HYDPAULIC
AND HYDROLOGIC DATA (1992)                                         potential heights that represent the hydraulic structure of
                                                              the lakes and connecting waterways (HEADQUARTERS, USA-
                                                              CE, 1994).
first order leveling lines and establish a single, more accurate     On the Great Lakes, astronomic tides have little influence
datum for North America. The result, covering Mexico, the          on water levels. Instead, atmospheric pressure changes and
United States, and Canada, is called the North American Ver-       winds cause most of the short-term water level fluctuations.
tical Datum (NAVD) of 1988. Maps and coastal projects are          Long-term changes are caused by regional hydrographic con-
only slowly being referenced to NAVD 1988. Specific defini-        ditions such as precipitation, runoff, temperature and evapo-
tions of various datums and their relationship with geodetic       transpiration, snow melt, and ice cover (GREAT LAKES COM
datums are listed in HARRIS (1981).                                MISSION, 1986). Global climate variations, in turn, influence
                                                              these factors. Crustal movements also influence levels. For
Water Level Datums of the Great Lakes of North
               AmericavlakesSuperirGHatnkesofg Nrthexample, the earth's crust at the eastern end of Lake Supe-
America (Lakes Superior, Huron, Mchigan,
AEerie  (ae  Spr, AH             nd  Ontia,                        ri or is rebounding about 25 cm/century faster than the west-
                E~eri~e, and~ O~ntarino)   ~ern end, resulting in a drop of the datums (apparent higher
  Low water reference datums used on the Great Lakes and           water) at the west end at Duluth. Aquatic plant life and man-
their connecting waterways are currently based on the Inter-       made control structures are additional factors that influence




                 |International  Great  Lakes  Datum   198'5  |Lake St. Lawrence (72.5)
                                                                               at Long Sault Dam, Ontario
                                                                                /   Lake St. Francis (46.2)
                                                                              //rat Summerstown, Ontario
  St. Marys River   Lake St. Louis (20.4)
     -\Lake              MLas -St Clair River M/ N/i--at Pointe Claire, Qu6bec
          /.l.~    t    ~~Micnigan /,-                              N iaro / /r/ 
     Superior-7  Huron  /                          Lake Erie        Fils      /   /   /  Montr6al Harbour (5.6)
      (185.2)/      ~    ~ ...../ 16/             %7173.5) L/            ke                       at Jetty Number 1


                                                                   7 .   . .L/  - - I = .  f    g~ntcrjo/   /   / Gulf of
                                                                                            St. Lawren
                 \4---5  Ad / L~~~~~~~~etroeitg||\
                                   Lake          River
                =            W    ~~~~(51t74l4a)          /           L

                                        Niagara Rive    /  St. Lawrence River
                                                                                                 \-Rimouski Quebec
                                    'c~U~~~~~~~~~~~~~~~ zIGLD 1985 Reference
                                                                                                    Zero Point
           610      I 97        359 I1 143 I   380   1561 2421 124 1451 84 1531              536
                    I                 I       I           I I      I      II      I I
                                                Distance (Km.)

Figure 8. The reference zero point for IGLD 1985 at Rimouski, Quebec is shown in its vertical and horizontal relationship to the Great Lakes-St.
Lawrence River System. Low water datums for the lakes in meters (from COORDINATING COMMITTEE ON GREAT LAKES BASIC HYDRAULIC AND HYDRO-
LOGIC DATA, 1992).




                                         Journal of Coastal Research, Vol. 14, No. 1, 1998






72                                                Gorman, Morang and Larson


the exceedingly complex cycles of water level changes in the     turn or North American (NA) datum) that must be updated
Great Lakes. As a result, the concept of mean water level is     to the current standards of NAD27 or the more recent
not applicable to these inland Great Lakes. Attempts to pre-     NAD83. To align maps to a specific coordinate system, a
dict lake levels have not been entirely successful (WALTON,      number of stable and permanent points or features must be
1990).                                                           identified for which accurate and current geographic coordi-
                                                                 nates are known. These locations, called primary control
           SHORELINE CHANGE MAPPING                              points, are used by computer mapping programs to calculate
Introduction                                                     the transformations necessary to change the map's projection
                                                                 and scale. The most suitable control points are triangulation
  Maps and aerial photographs provide a wealth of useful         stations whose current coordinates are available from the Na-
information for the interpretation of geologic coastal process-  tional Geodetic Survey.
es and evolution. Maps and photographs can reveal details          Maps that were originally printed on paper have been sub-
on:                                                              jected to varying amounts of shrinkage. The problem is par-
* Long-term and short-term advance or retreat of the shore       ticularly difficult to correct if the shrinkage along the paper's
* Longshore movement of sediments                                grain is different than across the grain. Maps with this prob-
                                                                 lem have to be rectified or discarded. In addition, tears, creas-
* The impact of storms, including barrier island breaches,          
                                                              es, folds, and faded areas in paper maps must be corrected.
  overwash, and changes in inlets, vegetation, and dunes
                                             oe s   an  ca i inlets, ve   Several steps are needed to accurately quantify shoreline
* Problems of siltation associated with tidal inlets, river
                  mouths, estuaries, and harbors                 change. These steps include assembling data sources, enter-
                                                                ing data, digitizing coordinates, analyzing potential errors,
* Human impacts caused by construction or dredging
* Complianc e with permits               or dredging             computing  shoreline change statistics, and interpreting
* Biological cond ition of wetlands and estuaries                shoreline trends. Based on shoreline change studies conduct-
                                                                 ed at universities and Federal, State, and local agencies, a
  The use of maps and aerial photographs to determine his-       brief summary of the recommended techniques and proce-
torical changes in shoreline position is increasing rapidly. An-  dures is given below.
alyzing existing maps does not require extensive field time
or expensive equipment, therefore often providing valuable       Data Sources
information at an economical price. This section summarizes
the interpretation of shorelines on photographs and maps           Five potential data sources exist for assessing spatial and
and corrections needed to convert historical maps to contem-     temporal changes in shoreline position.
porary projections and coordinate systems.                         USGS topographic quadrangle maps. Accurate delineation
  Many possible datums can be used to monitor historical         of the shoreline was not a primary concern on these land-
changes of the shoreline. In many situations, the high water     oriented maps. However, shoreline position is routinely re-
line (hwl) has been found to be the best indicator of the land-  vised on 1:24,000 topographic maps using aerial photographic
water interface, the coastline (CROWELL, LEATHERMAN, and         surveys. Many shoreline mapping studies have used these
BUCKLEY, 1991). The hwl is easily recognizable in the field      maps for quantifying changes in position, but more accurate
and can often be approximated from aerial photographs by a       and appropriate sources should be employed if available.
change in color or shade of the beach sand or a line of sea-       NOS Topographic Maps. Because the National Ocean Ser-
weed and debris. The datum printed on NOS T-sheets (to-          vice is responsible for surveying and mapping topographic
pographic) is listed as "Mean High Water." Fortunately, the      information along the coast, NOS topographic map products
early NOS topographers approximated hwl during their sur-        (T-sheets) have been used in the study of coastal erosion and
vey procedures. Therefore, direct comparisons between his-       protection, in law courts in the investigation of land owner-
torical T-sheets and modern aerial photographs are possible.     ship, and in the negotiation of international boundaries and
  In order to calculate the genuine long-term shoreline          territorial waters (SHALOWITZ, 1962). Most of these maps are
change, seasonal beach width variations and other short-         planimetric in that only horizontal position of selected fea-
term changes should be filtered out of the record. Ideally, the  tures is recorded; the primary mapped feature is the high-
best approach is to use only maps and aerial images from the     water shoreline. From 1835 to 1927, almost all topographic
same season, preferably summertime, when the beach is ex-        surveys were made by plane table; most post-1927 maps were
posed at its maximum width. In practice, however, maps with      produced using aerial photographs (SHALOWITZ, 1964). NOS
adequate coverage of a study area are usually few in number.     shoreline position data are often used on USGS topographic
As a result, a researcher is typically compelled to take all the  quadrangles, suggesting that T-sheets are the primary source
data he can find, regardless of the season (and usually he is    for accurate shoreline surveys. Scales of topographic surveys
glad to have found at least this much!).                         are generally 1:10,000 or 1:20,000. These large-scale products
  A crucial problem underlying the analysis of all historical    provide the most accurate representation of shoreline posi-
maps is that they must be corrected to reflect a common da-      tion other than direct field measurements using surveying
tum and brought to a common scale, projection, and coordi-       methods.
nate system before data from successive maps can be com-           Large-scale engineering surveys. In areas of significant hu-
pared (ANDERS and BYRNES, 1991). Maps made before 1927           man activity, engineering site maps often exist for specific
have obsolete latitude-longitude coordinate systems (U.S. da-    projects. However, surveyed areas often are quite limited by



                                          Journal of Coastal Research, Vol. 14, No. 1, 1998






                                       Monitoring Coastal Environments: Geospatial Methods                                 73


the scope of the project, and regional mapping at large scale     tion stations provide control points, which are crucial when
(greater than 1:5,000) is sparse. If these surveys do exist,      using older maps or a multitude of different map sources
they potentially provide the most accurate estimates of high-     (SHALOWITZ, 1964). Older maps may contain misplaced co-
water shoreline position and should be used. These data are       ordinate systems. If there is not enough information on the
valuable for rectifying aerial photographs.                       coordinate system or triangulation station, the map should
  Near-vertical aerial photography. Since the 1920's, aerial      not be used for quantitative data. A useful source of available
photography has been available for many coastal regions.          United States triangulation stations is Datum Differences
However, these images cannot be used directly to produce a        (U.S. COAST AND GEODETIC SURVEY, 1985).
map. A number of graphical methods and computational rou-           Media distortion can be eliminated by using maps drawn
tines exist for removing distortions inherent in photography      on stable-base materials such as NOS T- and H-sheets. Most
(LEATHERMAN, 1984; ANDERS and BYRNES, 1991). Users are            Corps of Engineers project maps have been made from linen
warned that conversion of photographic images to map pro-         or Mylar film. The original map or a high-quality Mylar copy
jection is not a trivial procedure, despite the availability of   should be used as opposed to black-line, blue-line, or other
modern cartographic software.                                     paper-based medium. However, if paper maps are used and
  GPS surveys. From the late 1970's through the early 1990's,     distortion from shrinking and swelling is significant, the dig-
significant advances in satellite surveying were made with        itizer setup provides some degree of correction by distributing
the development of the Navigation Satellite Timing and            error uniformly across the map. In addition, rubber-sheeting
Ranging (NAVSTAR) Global Positioning System (GPS). The            and least-squares fit computer programs allow the user to
GPS was developed to support military navigation and timing       define certain control points and correct for distortion errors
needs; however, many other applications are possible with         as much as possible. It is also important to remember that
the current technology. This surveying technique can be very      data in digital form acquire no new distortions, whereas even
accurate under certain conditions; however, signal degrada-       stable-base maps can be torn, wrinkled, and folded. Scale dis-
tion through selective availability causes significant position-  tortion from optical methods of map reproduction are also
al errors if only one station is used (LEICK, 1990). BYRNEs et    corrected by bringing all maps to a 1:1 scale.
al. (1994) have documented how they used GPS along with
hand-held survey lasers to map the shoreline of southern          General Digitizing Guidelines
Louisiana, which has experienced severe erosion and land
loss. They claim that they have been able to substantially          Cartographic methods and map handling should be consis-
upgrade the accuracy of old aerial survey photographs by us-      tent within a project and organization. The following shore-
ing GPS control points to rectify the photographs. In sum-        line digitizing guidelines are summarized from BYRNES and
mary, differential GPS provides the capability for accurately     HILAND (1994):
delineating high-water shoreline position from ground sur-          All shorelines are digitized from stable-base materials. If
veys, but surveys must be conducted carefully by trained op-      possible use NOS T- and H-sheets on Mylar or on bromide if
erators with properly calibrated equipment. Coastal re-           Mylar is not available. Shorelines mapped from rectified ae-
searchers should be beware of unskilled contractors claiming      rial photography are drawn onto, and digitized from, acetate
amazing accuracy on the basis of their new GPS tools.             film.
                                                                    To prevent curling and wrinkling of maps, store carto-
Data Entry                                                        graphic and photographic materials flat or vertical. Bromide-
                                                                  based maps that are shipped in a map tube should be kept
  Frequently, shoreline maps have variable scales and use         fiat for several days before digitizing.
different datums and coordinate systems. Shoreline maps             When attaching a map to a digitizer table, the area being
must be corrected to reflect a common datum and brought to        digitized is always perfectly flat. Any wrinkles can cause that
a common scale, projection, and coordinate system before          portion of the map to move during digitizing, creating posi-
data from successive maps can accurately be compared.             tional errors. High-quality drafting tape or masking tape is
There are several computer cartographic systems, consisting       used to attach the map. One corner is taped first, then the
of a high-precision digitizing table and cursor and computer      map is smoothed diagonally and the opposite corner is taped
interface, available. Ideally, a Geographic Information Sys-      securely; this procedure is repeated for the other two corners.
tem (GIS) should be used to digitize various data sources and     Once the corners are secured, the map is smoothed from the
store the information in data layers that can be linked to a      center to the edges and taped along each edge.
relational database. Most systems have a table or comment           High-precision equipment must be used for accurate shore-
file associated with each data layer to document the original     line change mapping. Digitizer tables and cursors with a pre-
map source, cartographic methods, and potential errors.           cision of 0.1 mm are recommended. This magnitude of change
  Digitized shoreline points are commonly entered into an x-      equates to 1 m of ground distance at a scale of 1:10,000. The
y data file for each shoreline source. A header or comment        center bead or crosshair should ideally be smaller than the
line should be incorporated into the digital file of the carto-   width of the line being digitized; the smallest pen width gen-
graphic parameters such as map scale, projection, and hori-       erally used is 0.13 mm (corresponds to the size 000 Rapido-
zontal and vertical datums.                                       graf pen). The width of the crosshair of a high-precision cur-
  Before the shoreline is digitized, triangulation points         sor is approximately 0.1 mm.
should be digitized for each shoreline map. These triangula-        When digitizing, use manual point input as opposed to



                                           Journal of Coastal Research, Vol. 14, No. 1, 1998







74                                                  Gorman, Morang and Larson


Table 3. Factors affecting potential errors associated with cartographic data sources.

                                      Accuracy
  Maps and Charts                      Field Surveys and Aerial Photographs                          Precision
Scale                             Location, Quality, and Quantity of Control Points         Annotation of High-Water Line
Horizontal Datum                   Interpretation of High-Water Line                        Digitizing Equipment
Shrink/Stretch                     Field Surveying Standards                                Temporal Data Consistency
Line Thickness                    Photogrammetric Standards                                 Media Consistency
Projection                         Aircraft Tilt and Pitch                                  Operator Consistency
Ellipsoid                         Aircraft Altitude Changes
Publication Standards             Topographic Relief
                                  Film Prints Versus Contact Prints
After ANDEas and BYRNES (1991)


stream input. Stream input places points at a specified dis-       H-sheets at a 1:10,000 scale, national map standards allow
tance as the user traces over the line being digitized. This       up to 8.5 m of error for a stable point (up to 10.2 m of error
procedure tends to make a very uniform and smooth line.            at 1:20,000), but the location of these points can be more ac-
However, it could miss some curvature in the line if the spec-     curate (SHALOWITZ, 1964; CROWELL,  LEATHERMAN, and
ified distance is too large; likewise, it could accept more        BucKLEY, 1991). Non-stable points are located with less ac-
points than are needed if the specified distance is too small,     curacy; however, features critical to safe marine navigation
resulting in extremely large files, as well as storage and dis-    are mapped to accuracy stricter than national standards (EL-
play problems. In addition, if the user's hand slips during the   LIS, 1978). The shoreline is mapped to within 0.5 mm (at map
digitizing process, stream digitizing will continue to place       scale) of true position, which at 1: 10,000 scale is 5.0 m on the
points in the erroneous locations. These can be difficult and      ground.
time-consuming to correct. Manual digitizing allows the user         Potential error considerations related to field survey equip-
to place points at non-uniform distances from each other, and      ment and mapping of high-water shoreline position were ad-
therefore allows the user to represent all variations in the       dressed by SnALOWIrZ (1964; p. 175) as follows:
shoreline.
  The seaward edge of the high-water shoreline and the cen-          With the methods used, and assuming the normal con-
ter point of the printed bathymetric sounding should be used         trol, it was possible to measure distances with an accu-
as the reference positions for data capture.                         racy of I meter (Annual Report, U.S. Coast and Geodetic
                                                                     Survey 192, 1880) while the position of the plane table
Potential Errors                                                     could be determined within 2 or 3 meters of its true po-
                                                                     sition. To this must be added the error due to the iden-
  It is important that all available procedures be used as           tification of the actual mean high water line on the
carefully as possible to capture map data; however, no matter        ground, which may approximate 3 to 4 meters. It may
how cautious the approach, a certain amount of error will be         therefore be assumed that the accuracy of location of the
generated in all measurements of horizontal position. Poten-         high-water line on the early surveys is within a maxi-
tial errors are introduced in two ways. Accuracy refers to the       mum error of 10 meters and may possibly be much more
degree to which a recorded value conforms to a known stan-           accurate than this. This is the accuracy of the actual rod-
dard. In the case of mapping, this relates to how well a po-         ded points along the shore and does not include errors
sition on a map is represented relative to actual ground lo-         resulting from sketching between points. The latter may,
cation. Precision, on the other band, refers to how well a mea-      in some cases, amount to as much as 10 meters, partic-
surement taken from a map or an aerial photograph can be             ularly where small indentations are not visible to the
reproduced. Table 3 lists the factors affecting the magnitude        topographer at the plane table.
of error associated with data sources and measurement tech-
niques. Both types of error should be evaluated to gauge the         The accuracy of the high-water line on early topographic
significance of calculated changes relative to inherent inac-        surveys of the Bureau-was thus dependent upon a com-
curacies. The following discussion addresses these factors in        bination of factors, in addition to the personal equation
terms of data sources, operator procedures, and equipment            of the individual topographer. But no large errors were
limitations.                                                         allowed to accumulate. By means of the triangulation
                                                                     control, a constant check was kept on the overall accu-
Cartographic Sources                                                 racy of the work.

  Shoreline measurements obtained from historical maps can           In addition to survey limitations listed by SnALOWITZ
only be as reliable as the original maps themselves. Accuracy      (1964), line thickness and cartographic errors (relative loca-
depends on the standards to which each original map was            tion of control points on a map) can be evaluated to provide
made, and on changes which may have occurred to a map              an estimate of potential inaccuracy for source information.
since its initial publication. Field and aerial surveys provided   Although it can be argued that surveys conducted after 1900
the source data used to produce shoreline maps. For T- and         were of higher quality than original mapping operations in



                                           Journal of Coastal Research, Vol. 14, No. 1, 1998





                                       Monitoring Coastal Environments: Geospatial Methods                                 75


the 1840's, an absolute difference can not be quantified. Con-    resulting data pairs include the x-value and the y-value,
sequently, the parameters outlined above are assumed con-         which represents the perpendicular transect.
stant for all field surveys and provide a conservative estimate     Once the shoreline data have been edited into files of equal-
of potential errors. For the 1857/70 and 1924 T-sheets, digi-     length segments, shoreline changes can then be computed.
tizer setup recorded an average percent deviation of 0.02, or     Shoreline change is generally reported based on three com-
4 m ground distance at a 1:20,000 scale. Line thickness, due      mon statistical values. They include the sample mean, sam-
to original production and photo-reproduction, was no greater     ple standard deviation, and maximum shoreline movement
than 0.3 mm, or 6 m ground distance for this same scale.          (BYRNES and HILAND, 1994; ANDERS, REED, and MEISBER-
  A primary consideration with aerial surveys is the inter-       GER, 1990). The sample mean is defined as a measure ofcen-
preted high-water shoreline position. Because delineation of      tral tendency for a set of sample observations and is ex-
this feature is done remotely, the potential for error is much    pressed as follows:
greater than field surveys and is a function of geologic control
and coastal processes. DOLAN et al. (1980) indicated that av-
erage high-water line movement over a tidal cycle is about 1
to 2 m along the mid-Atlantic coast; however, accurate delin-                              X =                              (1)
eation of the line is sometimes difficult due to field condi-
tions, human impacts, and photographic quality. Although          where:
the magnitude of error associated with locating the high-wa-
ter line is unknown, on gently sloping beaches with large tid-              xi = sample observations for i = 1 to n
al ranges (i.e., Sea Islands, Georgia/South Carolina), signifi-             n = total number of observations.
cant horizontal displacement can occur with a small increase
in elevation.                                                     The sample standard deviation s is a measure of sample
  For H-sheets, a topographical survey of the coast was often     variability about the mean:
conducted before the bathymetric survey. The control points
established along the shoreline were then used for position-
ing of the survey vessel offshore. Due to the nature of trian-                          i=      l
gulating distances and angles from points on land, horizontal                                    n - 1
positions plotted for the vessel became less accurate as it
moved away from shore. When the vessel was out of sight of
the triangulation points along the coast, positioning was done    The maximum shoreline movement represents the difference
by dead reckoning. Therefore, horizontal positions of some        in the most landward and seaward position. It also repre-
offshore soundings on early H-sheets may be suspect.              sents the end points for shoreline change inclusive of all the
                                                                  data sets. Identifying areas of maximum shoreline movement
Digitizer Limitations                                             is useful with beach fill projects.
                                                                    Comparisons of calculated shoreline change rates are gen-
  Another source of error relates to equipment and operator       erally grouped by specific time periods or by alongshore seg-
accuracy and precision. As stated earlier, the absolute accu-     ments (i.e., geomorphic features representing spatial trends).
racy (accuracy and precision) of the digitizing tables used for   The appropriate historical time period to use in the calcula-
this study is 0.1 mm (0.004 in). At a scale of 1:10,000, this     tion of shoreline change rates depends on how the rates are
converts to + 1 m. Furthermore, the precision with which an       to be applied and on the magnitude of allowable rate error.
operator can visualize and move the cursor along a line can       In general, the use of longer temporal spans (many decades
lead to much greater errors (TANNER, 1978). To evaluate the       or greater than a century) are preferred inasmuch as they act
magnitude of operator error associated with digitizing shore-     to decrease the impact of, shoreline mapping and surveying
line position, at least three repetitive measurements should      error, and, at the same time, filter out short-term fluctua-
be compared.                                                      tions (noise) from the long-term trend (signal). Shorter tem-
                                                                  poral spans (decades) are typically used in areas where recent
                                                                  shoreline change can be accounted for by a significant change
  In most instances, data pairs are generated from shoreline      in the beach system (such as the opening of a large and po-
locations relative to some arbitrary axis system. A compari-      tentially long-term inlet), or where the recent construction of
son of these data pairs is used to calculate mean shoreline       major coastal engineering structures has a significant impact
movements, variations in the rate and direction of move-          on the beach (DOLAN, FENSTER, and HOLME, 1991; CROW-
ments, and maximum net movements (ANDERS, REED, and               ELL, LEATHERMAN, and BUCKLEY, 1993). A case example,
MEISBURGER, 1990). Generally the coastline is divided into        shown in Figure 9, of distinctive spatial shoreline trends is
segments based on the general orientation of the shoreline,       located in northern New Jersey, where the shoreline is part
as shown in Figure 9. Baselines should be chosen based on         of a barrier spit complex including an active compound spit
segments that are parallel to the shoreline. Usually a stan-      (Sandy Hook to Sea Bright, New Jersey), barrier peninsula
dard Cartesian coordinate system is assigned to each seg-         (Sea Bright to Monmouth Beach), and a headland coastline
 ment with the positive x-axis directed generally north to         (Monmouth Beach to Shark River Inlet) (GORMAN and REED,
 south and the positive y-axis lying orthogonally seaward. The     1989).



                                            Journal of Coastal Research, Vol. 14, No. 1, 1998





76                                                Gorman, Morang and Larson




          - 40'30'          I
                                                                MEAN, M/YR                 STD DEV, M
                                                                -4    0    4         0    4    8    12   16
                          -N-
                            LI           SANDY HOOK










                  A..:                        SEA BRIGHT




                           ":ago~  C    .''!  4MONMOUTH BEACH




                 NEW JERSEY         '


          - 40'15'                   m ,:







                                   SHARK RIVER INLET
          -4010I '









Figure 9. Distinctive spatial shoreline trends along the northern New Jersey shore.



       BEACH AND NEARSHORE PROFILES                             ward of the zone that can be inundated by storms, usually
                                                               behind the frontal dunes. The lines should extend seaward
                                                               deep enough to include the portion of the shoreface where
  Periodic topographic and nearshore profile surveys consti-     most sediment moves (i.e., to beyond closure-discussed be-
tute one of the most direct and accurate means of assessing      low). At many projects, profiles are run to about 10 m depth,
geologic and geomorphic changes on the shoreface to water        although, depending on the wave climate, this may not be
depths of 10 or 15 m. Surveys conducted over time allow the      deep enough to record bed elevation changes that occur dur-
assessment of erosion and accretion in the coastal zone.         ing major storms.
Beach profiles provide the basic data for evaluating what
happens to sand placed in beach nourishment projects (WEG-       Monuments
GEL, 1995). The most common surveying technique is the col-        Permanent or semi-permanent benchmarks are required
lection of shore-normal profiles. The lines must extend land-    for reoccupying profile sites over successive months and



                                         Journal of Coastal Research, Vol. 14, No. 1, 1998





                                         Monitoring Coastal Environments: Geospatial Methods                                      77


Table 4. Example of beach fill area profile survey scheme.

             Times/
 Year         Year                                                    Number of Profiles
pre-fill        2         Collect within fill area and at control locations in summer and winter months to characterize seasonal profile envelope
                           (beach & nearshore to closure depth).
post-fill       1         Collect all profiles immediately after fill placement at each site (beach & offshore) to document fill volume. Collect control
                           profiles immediately after project is completed.
1               4         Four quarterly survey trips collecting all beach and offshore profiles out to depth of closure. Begin series during the quar-
                           ter following the post-fill survey.
Continue year 1 schedule to time of renourishment (usually 4-6 years). If project is a single nourishment, taper surveys in subsequent years:
2               2         6- and 12-month survey of all beach and offshore profiles.
3               2         6- and 12-month survey of all beach and offshore profiles.
4               1         12-month survey of beach and offshore profiles.
Note: If project is renourished, repeat survey schedule from post-fill immediately after each renourishment to document new fill quantity and behavior.
Project-specific morphology and process requirements may modify this scheme. Monitoring fill after major storms is highly desirable to assess fill behavior
and storm protection ability. Include both profile and sediment sampling. Conduct less than one week after storm conditions abate to document the beach
and offshore response.
After STAUeLE (1994)


years. These benchmarks should be located at the landward             coastal erosion or vandalism. Another point of importance:
end of the profile lines in order to minimize their likelihood        monuments should be referenced to geographic datums so
of being damaged in storms. The locations of survey monu-             that the profile data can used to evaluate changes in sea level
ments must be carefully documented and referenced to other            or other phenomena that require reference to established re-
survey markers or to control points. The ability to accurately        gional datums. With the increasing use of Global Positioning
reestablish a survey monument is critical because it ensures          System (GPS) receivers by surveyors, the rigorous need for
that profile data collected over many years will be compara-          duplicate survey monuments may be reduced. This is an
ble (HEMSLEY, 1981). Locations that might experience dune             evolving technology, and for now we still recommend that two
burial should be avoided, and care should also be taken to            monuments per survey line be established. U.S. Army Corps
reduce the visibility of benchmarks to minimize vandalism.3           of Engineers standards for construction of monuments are
  The safest procedure is to establish two benchmarks or              discussed in HEADQUARTERS, USACE (1990).
monuments. One should be at the dune line; this serves as
the origin for the profiles, which are run seaward either per-        Project Planning
pendicular to the local shore or at a fixed azimuth. The sec-
ond benchmark should be situated some distance inland so                When planning a beach profiling study, both the frequency
that it can serve as an emergency marker in case of severe            of the sampling and the overall duration of a project must be
                                                                     considered. Morphologic changes of beaches can occur over
                                                                    varying time scales, and if long-term studies are to be con-
  3 Unfortunately, damage caused by vandals is a serious and ex-      ducted, the dynamic nature of the beach should be taken into
pensive problem at all coastal projects, even ones far from urban
areas.bly, it is financially and logistically imprac-
                                                                     tical to conduct frequent, repeated surveys for a sufficient
                                                                     length of time to obtain reliable and comprehensive infor-
                                                                     mation on long-term processes at the study area. Nonethe-
  10         ,  ,                          , I       ,                less, resurveying of profile lines over a period of more than
                        Amelia Island, Florida                        one year can be of substantial help in understanding the pre-
                                             Survey Line A49
                                                  26 Jul E8          vailing seasonal changes. In addition, supplemental surveys
                sr                                    ~~~~~~~~22 Aug 90o.   can be made after big storms to determine their effects and
                                                                     measure the rate of recovery of the local beach system. At a
                                                                     minimum, summer and winter profiles are recommended.
 .E                                                                    Unfortunately, there are no definitive guidelines for the tim-
  .si _  ...                                                          ing and spacing of profile lines. Table 4 outlines a suggested
 a': ...... -. survey schedule for monitoring beach fill projects. In sum-
                                                                     mary, observations over a period of time are recommended in
  -'ï¿½ -                                                       -        order to document the range of variability of morphology and
                                                                     bathymetry.
            50  ,      00                           v , , ,Spatial aspects of a field study must be carefully planned,
    0           2      010  4000    sow    s  0o     w
                        Distance from Baseline, m                     including the spacing of profiles and the longshore and cross-
                                                                     shore dimensions of the study area. Profile lines should be
Figure 10. Example of vertical offset between two offshore profile sur-
veys due to use of different datums. (From Gorman et al., 1994)       spaced at close enough intervals to show any significant
                                                                     changes in lateral continuity. In a cross-shore direction, the



                                             Journal of Coastal Research, Vol. 14, No. 1, 1998





78                                                 Gorman, Morang and Larson





                                              Base of Dune

                                                                 Shoreline Position Defined as Intercept
                                                                 of Profile with Mean High Water



        > g                                                              0.0 NGVD
                                                                           Mean Low Water
         E
         c                                  Subaerial               \                               Inner Bar Crest
        .-                           -    Beach Width

         UD                                                                                         Slope Break
                                                                       to Inner
                                                                         Bar
                                            Zone Over Which                         Zone Over Which
                                             Beach Slope        -                  Nearshore Slope
                                               Computed                                Computed

               * Not to Scale

                                                      Distance From Baseline
Figure 11. Features within the beach and nearshore zone used for linear profile computations.



uppermost and lower-most limits of the profiles should be         from about +1.5 m to closure depth. This results in overlap
located where change is unlikely to occur and should ade-         between onshore rod surveys and sled surveys to assure that
quately cover the most active beach zones such as the fore-       the two systems are recording the same elevations. If offshore
shore and upper shoreface. Reviewing locations of historical      surveys are conducted by boat-mounted echo sounder, over-
shorelines in the study area is one way to establish the gross    lap with rod surveys is often not possible because most boats
limits of the area that should be examined in detail during a     cannot survey in water shallower than about 11/2 or 2 m. Also,
profiling program, particularly along rapidly changing coasts.    acoustic surveys are impossible in the surf zone because bub-
For example, shore and dune deposits that are now inland          bles in the water attenuate the acoustic pulses. DALLY,
from the modern shoreline are likely to be affected by marine     JOHNSON  and OsiEcxi (1994) have described the. develop-
or lacustrine processes only during large storms. It may nothibious vehicle that may al-
                                                                 ment of a remote-operated amphibious vehicle that may al-
be necessary to run surveys regularly across the dunes, and
                                                             low surveys in areas where a sled cannot be maneuvered.
aerial photographs of these interior areas may be adequate
                        for . examining morpho c c s .              Comparison of sled/Zeiss systems and boat echo sounders
for examining morphologic changes. If the shoreline has
shown patterns of retreat or advance over time, the seaward       has shown sled surveys to have a higher vertical and hori-
extent of profiles may need to be extended far enough off-        zontal accuracy (CLAUSNER, BIRKEMEIER, and CLARK, 1986).
shore to accommodate an advance of the shore.                     Echo sounder surveys are limited by the indirect (acoustic)
                                                                 nature of the depth measurement, the effects of water level
Accuracy Criteria                                                 variations and boat motions, and the inability to survey the
                                                                 surf zone due to wave action and tidal range. In summary,
  Elevation resolution for a typical profile across the beach
                                                                 there are quality advantages in using sled surveys offshore,
and extending offshore to closure depth will vary according
                                                                 but operational limitations are imposed by wave heights, wa-
to the survey method, sea state, reference datum, and sta-
bility of the subbottom material. It is impossible to assign a    ter depth, seafloor obstructions, and the maneuvering needed
single accuracy value to cover these factors. However, under      to keep the sled on line.
ideal conditions, the estimated vertical accuracy is the resul-     All repetitively-surveyed profiles must be referenced to the
tant mean square error of + 0.15 ft (0.05 m) (HEADQUAR-           sAme elevation datum. This can especially be a problem when
TERS, USACE, 1994, Table 9-3). Most surveys do not achieve        echo sounder surveys are conducted by different agencies or
this accuracy, especially if the offshore data was collected      contractors over time (Figure 10). Meticulous field notes must
with acoustic methods.                                            be kept to record datums, corrections, equipment calibra-
  As described earlier, the seafloor close to shore is often sur-  tions, and other information that are needed for accurate
veyed by a sled which is towed by boat out into the water         data reduction.



                                          Journal of Coastal Research, Vol. 14, No. 1, 1998






                                      Monitoring Coastal Environments: Geospatial Methods                                  79


                                                                (BMAP) contains many analysis tools, including generation
   40--                                                           of synthetic profiles (SOMMERFELD et al., 1994).
                                       37th Street                Vertical elevations of morphologic features found on pro-
                             --Pre-State Fill   16 Jun 88       files are usually referenced to NGVD 29 or another datum
   20--                       Post-State Fill  -- 22 Sep 88       specified for a particular project. All horizontal distances
                               i4-Month ... 17 Jan 89           should be measured from the designated baseline monument.
 1Q- ,x                                                           Survey distances offshore often vary in length due to wave
          XCu>~~~~ 0>~ "NGVD                                     conditions at the time of the sled survey. Volume change cal-
                                                                culations can be made from the baseline to a common dis-
  -10--                                                           tance offshore (usually the shortest profile) to normalize vol-
                                                                ume change between survey dates.
  -20--
                                                      '  --.;   Profile Survey Applications
  -So
     0   200  400  600  800  1000 1200 1400 1600 1800 2000.
                     0   200  400  00  800  1000 1200 1400  16  180    Beach response to coastal processes can be interpreted
                          Distance, ft                           from geometric and volumetric comparison of beach profile
                                                                sets. If the profile sets cover a long period, information on
                                                                both the cross-shore and alongshore evolution of a coastline
    40. -can be made (i.e., shoreline advance or retreat, position of the
                                                                berm crest, and closure depth). Several types of beach param-
                   so30 ~~~--            37th Street      ~       eters can be measured from profile data, including the width
                                  Preo-Storm--    17 Jan 89      of the subaerial beach, location and depth of the inner bar,
    2o--                          Post-Storm ....-  20 Apr 89
                   2a__           Post-Storm---- 20 Apr 89        and beach and nearshore profile slope. Comparisons between
                g=~~~~ i~~~~~o-->~ ~successive profiles can be used to quantify shoreline position
                                                X  ~  NGVD  ~   change, volumetric change, and seasonal profile response.
ï¿½>   0                                                             Numerous  authors  (e.g., BASCOM,  1964;  KOMAR,  1976;
W        ,         R                                               HANDS, 1976; WRIGHT and SHORT, 1983) have documented
   -10 - -             -
         -14 ~      ~~~0 Xothe cyclic nature of beach topography and its response to sea-
   -20--                                                          sonal shifts in wind and wave climate. In addition to normal
                                            ---        _ ~ ~effects, profile surveys can also be used to measure change
   -o      :    :    :    :    :    :    :    :                   caused by short-term episodic events (CHiu, 1977; SAVAGE
      0   200  400  600  800  1000 1200 1400 1600 1800 2000       and BIRKEMIER, 1987).
                                                                and BmRKEMEIER, 1987).
                           Distance, ft                            Linear measurements. Selected parameters can be used to
Figure 12. Analysis of the Ocean City, Maryland, beach fill project. Up-  define cross-shore morphologic features within a study area.
per plot shows profile before beach fill and the large quantity of sand  General location and limits of features in the beach and near-
placed on the beach during the summer of 1988. Lower plot shows erosion  shore zone used for linear profile computations are shown in
of the upper profile during a storm in early 1989. Sand from the beach  F  11
moved offshore to the region between 400 and 900 ft from the benchmark.  gure
(From Stauble et al, 1992)                                         * The most variable beach parameter is beach width, which
                                                                   is usually measured between the base of the dune and
                                                                   mean low water (mlw).
                                                                0 Beach slope can be calculated between the base of the dune
Analysis Techniques
                                                                   and mlw.
  Profile analysis reveals the variability in cross-shore elevation  0 The zone from mlw out to the nearshore slope break is
patterns and volume change that occur along a profile line. With     generally considered as the area where the nearshore slope
multiple profiles, the alongshore variability in profile response    is computed.
is documented. With a long-term monitoring program, seasonal       * Alongshore changes of the inner bar position are a useful
variations and the impact of storms can be identified.               guide of the surf zone breaker height and bottom slope. The
  Profile data recorded in the field are typically processed in      inner bar position is measured from 0.0 m (NGVD) to the
the laboratory using computer software packages. The Coast-          bar crest (GORMAN et al., 1994).
al Engineering Research Center (CERC) Interactive Survey           * If shoreline change or aerial photography maps are not
Reduction Program (ISRP) plots and compares both spatial             available, shoreline position can be estimated from the lo-
and temporal profile sets (BIRKEmMEIER, 1984). The program           cation of a specified elevation point on a profile line. An
allows the plotting of field data sets at various scales and         approximate position of the high-water shoreline should be
vertical exaggerations from baseline (x) and elevation (y). An       selected based on local tidal information. A common ele-
unlimited number of profiles can be plotted on a single axis         vation referenced for this type of analysis for many engi-
to compare profile change and determine profile envelopes            neering projects is 0.0 (NGVD) (U.S. ARmy ENGINEER DIS-
and closure areas. The most frequent analysis uses profiles          TRICT, JACKSONVILLE, 1993). However, this position con-
of successive dates to compare morphology and volume                 stitutes a highly variable measure due to the movement of
changes. CERC's Beach Morphology and Analysis Package                the bar or ridge and runnel features along the lower beach.



                                          Journal of Coastal Research, Vol. 14, No. 1, 1998






80                                                        Gorman, Morang and Larson





                                                    FRF Survey Line 62 (1984-85)

                                        Dune
                                                                                    Profile Line 62
                                                                                                20  Mar 84
                               4 Beach                                                               6 Sep  85


                           2                      B r/Trough

                       ï¿½ 0
                               _ I1


                         -8 -


                         -6

                         -8 

                        -10                     I       I        I                       I       I       I       I
                              0      100    200    300    400    500   600    700    800    900   1000
                                                              Distance, m


Figure 13. United States Atlantic coast profiles showing typical winter erosion and summer recovery. (Stauble 1992)








































Figure 14. Ridge and runnel system, Charlestown, Rhode Island. Stranded sea grass and debris marks limit of high tide runup.




                                             Journal of Coastal Research, Vol. 14, No. 1, 1998






                                     Monitoring Coastal Environments: Geospatial Methods                               81




                                                       STJOE1 1


           15
                                                                                           LEGEND
                                                                                     -    SJ 11 910830 1200
           10 .......... SJ 119110150
                                                                                  -    SJ 11911015 0
                                                                                  ----- SJ 11911912 0
             5                                                                      -    SJ 11920518 915
                                                                                  ----- SJ11 920617 1010
                                                                                  --    SJ 11920618 845
               0E----- ...  11 2Ci~U i4uU
                                                                                    -    SJI 11930504 1400
                                                                                  -. .S.. J11 930812 400



       .~ -1 0 -       a

                                                                 Till Platform with Possible Sand Veneer
       0:-15-.


          -20-


          -25 


          -30


          - 35 
              0       500      1000      1500      2000     2500      3000      3500      4000      4500      5000
                                                  Distance Offshore (ft)

Figure 15. Profile envelope from St. Joseph, Michigan. The horizontal platform 1,000 to 2,500 ft (300 to 750 m) offshore is an exposed till surface. Most
shoreface sand movement appears to be confined to the zone landward of the till platform, although it is likely that thin veneers of sand periodically
cover the till (CERC project data).



  Volumetric analysis. Volume analysis of most long-term        is a function of storm frequency and intensity. When trying
profile data sets will provide temporal and spatial documen-     to determine the extent of the profile envelope, at least 1 year
tation of profile volume change due to overwash processes,       of data should be used. The profile envelope of an East Coast
storm impacts, and nearshore bar evolution. Computer pro-        beach system is shown in Figure 13, with the characteristic
grams such as ISRP can provide quantitative information on       winter and summer berm profiles. Because there are fre-
profile shape change and volume of sediment gained or lost       quent local storm surges during the winter months, the berm
between two or more survey dates (BIRKEMEIER, 1984). Fig-        and dune crest often retreat; however, in many areas sand
ure 12 shows an analysis of the Ocean City, Maryland, beach      recovery takes place during the summer months as littoral
fill project. Based on volume computations, this type of anal-   material moves onshore and longshore. Along a well-defined
ysis provided a time history of fill placed on the beach and     ridge and runnel system, significant sediment exchange can
the subsequent readjustment of the fill material. Typical pro-   occur between the summer and winter months (Figure 14).
file response showed erosion on the dry beach above NGVD         Great Lakes beaches also display summer/winter patterns,
and accretion in the nearshore area after fill placement as      often characterized by considerable bar movement (Figure
the shoreface adjusted to a new equilibrium profile.             15). At some Great Lakes sites, the mobile sand layer is quite
  Seasonality. Winter erosional beach profiles can be char-      thin, and seasonal patterns can be difficult to detect.
acterized as having concave foreshore areas and a well-de-                        BATHYMETRI  DATA
veloped bar/trough in the nearshore. During fair-weather
summer conditions, the bar moves landward and welds onto         Introduction
the foreshore, producing a wider berm with a lower offshore        In many coastal studies, the analysis of topographic and
bar and flatter trough. Profile response to the seasonal cycle   bathymetric data is one of the fundamental tools used to eval-



                                         Journal of Coastal Research, Vol. 14, No. 1, 1998







82                                                   Gorman, Morang and Larson











                                               .~Ati  0     '0001         EXISTING STONE JETTY SECTION
                                                   e~~~~~~~oOt-,Ojo   ,f-,OJ






                    0 ~  ~    ~    p ï¿½                                                                    5)O    'd -r
               ?11~~~~~0
                                                'bb

                          \A, o          boerOn3~r--~O





                                         b, ~ ~     ~     ~     S        a                    2'  00nq'q00
                                        ";d           ?;a~~~~~~~~~~~~~~~~rnZ                     C56( 0      6da





                                    ~~~~~~~~~V9)~~~~~~~~~~~~~~~~~~~~~~~~  \~2'                           0  'dP    -d(
                                    .b                                           10
                        <),0                   KI O
                                     'fr 6        \M    (o9m  6 '   ao                         rsi      6 i; 6 a 4-.o -6 oo










               12~~~f~                <'2 
                                  Y~~ ~        ~~~~~ ~                        ~ ~XSIG S TOE  J T TYSECION~i





                'P 0                If.
               \9)  r" "4'                        \03O     


















                                      99'~ ~ ~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~ O -    O1<  a  s_ 6-5 6-o   Odd    -c  da -a-.
             p ï¿½   <SQ          'Ps                     9)


















                  9, ~ ~ S
                                                            A.. \cl   uo -
















                 <0 0    Qflz~~~.4- 0           40Q On69              N                    N                   7
                             4~~~~~~~~~~9
                               0<   ,, -:<JL~0 O 2 O O O S

                          ( 9                      \O\?        P t --                        _ _ _  
                               9;`2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~9




















                                                   A0 .o                    -
                                         0 0                 C     >
                    f~om U.S.oA r        m       y nger         D          i strict, Mob       ile.)



                                      Jr         of          Co     a    s     talResearch, Vol. 14, No. 1,  1 9 98
                 5~ ~ 9               <'T         9        C   <
                                       N            t        I 9)<2 <bo  odd

                                           N,      (\ 0        , r
                2   ~         ? o< 4,:
                (99L                       .                     n  
                                s ~ ~~      ~~              oor         erraoï¿½oin   a  ndsddcd
                    > o
                                <'~~<    4   4%               EXISTING STONE  JETTY SECTION           ~         o ~I-~n 
                       '%t~I %D
                      \%                 .''          0rï¿½  Ne.a     C- Ga a a aan an a   oooOoo              dd dddo 

                7~p~ C). 4 t
                                                        eim<?"      q9s3   SO<              Pf          rO       ,<
                   4a                          Yï¿½                                                     n       naa 
               tot                                                                                                   ï¿½a
               p5 o                   I:              ~

                    Q5    "<2;Co    CJN.e o4a2aoa   o09O   l.l2O~~-'



                  -   ij4-                              (P
                  7.~~~~ {

                         -~~~~~~~~~~EXISTINGWERSCINTOBREARDUER HS CO6N JTRAT) ET



                       -G~na a0 C 0 '<4 0 0<'<~ Ga'0r    *J        <2Oo~o adO0N~n~3oooo                               o~
                .   b&         n      %o;ztswoo~                             _'  aaaflOOOOO~~~c4<4*4*4*4a66d adoad
                                       bhro~~~~~~~~~~~~004<6141a4414
      Fiue1.Hn-anttdhdorahcmpfo Es  as  lrda  ets(nfet  aebe  oretdfrtdeadaerfrncdt  i.(a
      frmUS An   niee  ititMbl.



                    's,.o ~ ~ ~ ~ ~~ornlo ostlRsach  o.1, o  ,19






                                       Monitoring Coastal Environments: Geospatial Methods                                  83



               to                 -                                  -l 
               0    ''          '            '''-".'.-'I
               0
               0



               O ï¿½'-                   "        ""-



               o7o





                                    ..-   .-    -    .-    -                --.   *.




               o          -   ,.
               0,                         :- -- --                --       -     -.-  -















                I)            FEB    1990


                  1363000 1364000    1365000    1366000    1367000 1368000
Figure 17. Digitally collected hydrographic data from a Florida project site. The track lines are obvious, as is the fact that soundings are not uniformly
distributed throughout the survey area. (Data courtesy of U.S. Army Engineer District, Mobile).



uate historical morphological changes, patterns of erosion         agencies like NOAA, but often a researcher must first digitize
and sedimentation, and shoreline response over time. When          the maps in order to be able to perform computer-based pro-
assembling bathymetric surveys from a coastal area, a re-          cessing and plotting. If only a very limited region is being ex-
searcher is often confronted with an immense amount of data        anined, it may be more expedient to contour the charts by hand.
that must be sorted, checked for errors, redisplayed at a com-     The disadvantage of hand-contouring is that it is a subjective
mon scale, projection, and datum, and compared year by year        procedure. Therefore, one person should be responsible for all of
or survey by survey in order to detect whether changes in          the contouring to minimize variations caused by different draw-
bottom topography have occurred. This section will discuss         ing styles or methods of smoothing topographic variations.
three general aspects of geographic data analysis:                   In order to manipulate 3-dimensional (x, y, and z) data,
ï¿½ Processing of bathymetric data using mapping software            display and plot it at different scales, and compare different
                                           o .            .  ''   ' '' .  '~.o    .o        . 































                                                0ï¿½Apliatinsdata sets, it is necessary to use one of the commercial map-
               Applicatisand display of the processed results     ping programs such as GeoQuest's Contour Plotting System
                 EAST  PASSFLORIA-.-


























ï¿½ Error analyses                                                   3 (CPS-30), Golden Software's Surfer451 or Plus III Software's

                                                                  Terranaodelm. These are comprehensive packages of file ma-
                            Bahmti   aaPoesn-aaPeaainadnipulation, plotting algorithms, contouring, and 2- and 3-di-
input                                                              mensional display. Their use requires considerable training,







                                           Journal of Coastal Research, Vol. 14,No. I, 1998
                             1363000 164000    135000    136600    136700 136800
            Fiue 7  Dgtll  oletd yrorpicdtafo aFord  roet ie Tetrc lnsar  bvos a  s h  ac  ha-ondnsor  otuifrl
             distriuted troughut thesurveyarea.(Data ourtes of US ArmyEnginer Disrict, obile

   uehsoiclmrhlgia   hne,  atrsofeoin                             aenislk  OAA  "ut ofte a-eerhrmstfrtdgtz
                   andsedmenatin,  nd  horlin repose vertim. Wen   he  apsin rde t beabl toperormcomute-baedï¿½oo
    asseblin  bahyeti  suvy'rmacatlaear-                          csigadpotn.I  nyavr  iie  eini  en  x
    searcher isotn'ofote-ihanimneomutof data                       am d it *aï¿½emr   xein  ocotu  h  hrsb  ad
    thatmus  be ortdcekdfrerrrdslydaac                           Tedavntgofhd-cnorg is 'hti  sasbetv
               monscleprjecio, nd  atm ad  omare  yar y ear      prceure Tereor, ne eron hold e esonsbl-fo '.o
                       orsuvy  ysuvy  nore  t  etc wehe   hags  n th cnouig omiiiz  araioscasd ydifretL:w
    bottom      O toorah  hav  ocurd'hsscinwl'ics                       tlsormtoso  mohn  oorpi  aitos
                   thre enra asecs f eogapicdaa aalsi:                n ode  t mniplae  -dmenioal(x y'an.z dta
     *~~~ES PrcsigobahmtidtAuSigmpngSofwr                          ipa   n   ltitdfeetsae, FLOID '-.ar  diffren
                            0~~~~~~~~~~~~dt  sets it' eesr    o ueoeo  h   omrilm
    *~~~~                                                               ~'octosad  ipa  fteprcse  eut





84                                                  Gorman, Morang and Larson



              O





                            o.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I.I

                      5~~~~~~~~~........\.....
               0 ::::::::.........







                       0 ~~~~~~~~~~............. ............... .............................................
                r. ......................... ......................... .................................
               0.
               o .............................................................................

               _0  ::;;::.............
                                '~~~~~~......... .................::::::::::::::::::::::::::::::::::::
                  :::::::::::.................................. ...............................


                       C) .....~~~~~~~.........................t ................................. .....................



                    u-I.~~~~~~~~~~~~~~~~~~~~~~~~~~~~
               0.


                       0 ::::::~~~~~~~..........

                   0 ::::::::~..........

               in                   .........



                 1363000 1364-000    136,5000    1366000    1367000 1368000
Figure 18. Surface grid computed by OPS-3 based on the data shown in Figure 17. The nodes are uniformly spaced compared with the locations of the
original soundings. A grid does not necessarily have to be square, although this is common.




  The raw data used by mapping programs consists of indi-           Gridding Operations
vidual points in x-y-z form. As described earlier, if the data        Gidn   o  ufc   oeig   samteaia   rcs
                           ~~~~~~~~~~~~~Gidn  o  ufce m d ln)           ...........alproes






are derived from old maps, they must first be corrected to a        i  hc      otnossraei  optdfo     e  frn
               commo  datm, mp prjecton, ad cordinte sstem  For   domly distributed x, y, and z data.4 The result is a data struc-
               small iles, isual xaminaion ofthe daa may  e wortwhile ture (usually a surface) called a grid. Note that the grid is an
in order to inspect for obviously incorrect values. Because it      aricalsutreItsbsdonhergnldtbtte
               is lborius t reiew  housndsof dta pint, siple  ro- grid points are not identical to the original survey points (Fig-
Figruread 18) . Becmas e o n     the    data  For in         ig     ure  17  nd       e s  are grid epreesents the surface that
oiiall soninshAgi doepts ino anecsarily have exetdto be sqaelhuhthiwecmmn +.0






viualle  eponts in an- foreamare expected tobebetweenï¿½2.0          Ais being modeled, the accuracy of the surface model directly
arend -120 ma ceckive frogram old maffepts that are                affects to  quality of any output based on it or on compari-
outside this ra nge. The analyst can then determine if ques-        sons with a       grid. generat          therid     s     an
tionable points are erroneous or represent genuine it artingca grIt is ned                       onfore origins such but tu-
expected topography.
  Many analysis procedures display and manipulate data in           imp    le pro-ulaid   poile generaton, or surve pom-
Cartesian coordinates. If the original maps were based on
                                                               g Most examples in this section wee repred using CPSu3ï¿½ map-
Sallthe dPthlnanarare epcoodntes, tohe betwend y2 pins beingmdleteacry ofth sufaemoedirctly



State Plane coordinates, the x and y points will not ched con-k ping software. The overall concepts and procedures discussed are
version. Points in latitude and longitude usually must be con-      general, and other software packages perferm similar functions but
verted by the program to a rectangular projection,                  with different mathematical algorithms.



                                        Journal of Coastal Research, Vol. 14, No. 1, 1998





                                       Monitoring Coastal Environments: Geospatial Methods                              85



























                  /-.". ~.'K          /      //-Z  ,,4~/A////I//t//%$f/ /  1/   / /St  V?////f/
Figure 19. TIN surface model computed by Terramodel based on the data shown in Figure 17. Because of the density of the triangles, only a 200 x 300
ft section is shown. The apex of each triangle is at a depth data point.



parison can be performed. The advantage of a grid is that it      The fundamental challenge of a gridding algorithm is to
allows the program to manipulate the surface at any scale or    estimate depth values in regions of sparse data. The proce-
orientation. For example, profiles can be generated across a    dure must attempt to create a surface which follows the trend
channel even if the original survey lines were not run in these  of the terrain as demonstrated in the areas where data do
directions. In addition, profiles from subsequent surveys can   exist. In effect, this is similar to the trend-estimating that a
be directly compared, even if the survey track lines and the    human performs when he contours by hand. The other chal-
spacing of data points were very different.                     lenge occurs in complex, densely sampled terrains. The al-
  Several steps must be considered as part of the grid gen-     gorithm must fit the surface over many points, but genuine
eration. These include:                                         topographic relief must not be smoothed away! Along a rocky
                                                                 coast, for example, high pinnacles may indeed project above
ï¿½ Selecting a gridding algorithm
                                                                 the surrounding seafloor.
* Identifying the input data
                                                                   Gridding algorithms include:
* Specifying the limits of the grid coverage
* Specifying gridding parameters                                * Convergent (multi-snap) (CPS-3@ software)
ï¿½ Specifying gridding constraints                               * Least squares with smoothing
* Computing the grid                                            * Moving average
                                                                 ï¿½ Trend
The choice of a gridding algorithm can have a major effect on   * Trend
the ultimate appearance of the surface model. Software com-
panies have proprietary algorithms which they claim are uni-    The convergent procedure often works well for bathymetric
versally superior. Often, however, the type or distribution of  data. It uses multiple data points as controls for calculating
data determines which procedure to use, and some trial and      the values at nearby nodes. The values are blended with a
error is necessary at the beginning of a project. Because a     distance-weighing technique such that close points have more
computed grid is an artificial structure, often it is a subjective  influence over the node than distant points. Several itera-
evaluation whether one grid is "better" than another. For       tions are made, with the first being crude and including many
subaerial topography, an oblique aerial photograph can be       points, and the final being confined to the closest points. The
compared with a computer-generated 3-dimensional drawing        least-squares method produces a plane that fits across sev-
oriented at the same azimuth and angle. But for a subaque-      eral points near the node. Once the plane has been calculat-
ous seafloor, how can a researcher really state that one sur-   ed, the z-value at the node is easily computed. The reader
face does not look right while another does? Even comparing     must consult software manuals to learn the intricacies of how
a gridded surface with a hand-contoured chart is not a valid    these and other algorithms have been implemented.
test because hand-contouring is a very subjective procedure.      Another important parameter that must be chosen is the



                                           Journal of Coastal Research, Vol. 14, No. 1, 1998





86                                                 Gorman, Morang and Larson




                  o                                                     1
                  o
                  o



                  [0                                                                    9

                  LO

                  o







                            L~                                                                U~~~~~~/
                  O
                  LO







                  ~o   -ft --                       --
                  0










                   o ERSI PRSSI  FLORIUR -,.---   '-LJ\----
                  0








                              FEB 1990                       .\
                  0
                  [0
                     1363000 1364000    1365000    1366000    1367000 1368000
Figure 20. Contoured bathynmetry of the same area shown in Figures 17 and 18. Depths in feet below miw (English units retained to correspond with
the units used for the original data collection).


gridding increment. This is partly determined by the alga-        TIN model is that it can describe a topographic surface at
rithm chosen and also by the data spacing. For example, if        different levels of resolution as far as the information con-
survey lines are far apart, there is little purpose in specifying  tent is concerned (TsAI, 1993). Another advantage is that a
closely spaced nodes because of the low confidence that can       TIN model can accurately describe more complex surfaces
be assigned to the nodes located far from soundings. In con-      and use less space and computer time than grid cell models
trast, when the original data are closely spaced, large x- and    of similar resolution (McCuLLAGH, 1988). An  example of a
y-increments result in an artificially smoothed surface be-       TIN surface model is shown in Figure 19 using a small por-
cause too many data points influence each node. Some pro-         tion (- 60 x 90 m) of bathymetry data from East Pass,
grams can automatically calculate an increment that often         Florida. Additionally, TINs are used to support digital ter-
produces good results.                                            rain modelling analyses which include contouring, calculat-
                                                                  ing slope, generating cross-sectional and three-dimensional
TIN Models                                                        displays, analyzing cut and fill volumes, and viewing sur-
  Contours computed by GIS systems are frequently based           face changes at multiple angles (BURRouJGH, 1986; CLARKCE,
on Triangulated Irregular Network (TIN) models (PEUCKER           1990; KORTE, 1994).
et at., 1976). A TIN is generated from a series of irregularly      Once a triangulated network is computed, a grid matrix
shaped triangles interpolated from elevation data points          can be generated using interpolation algorithms. Topographic
forming a three-dimensional surface. A TIN model is com-          (or bathymetric) contours can then be computed from the grid
posed of nodes, edges, triangles, and polygons (ENvIRON-          surface. Contours are usually smoothed using various splin-
MENTAL  SYSTEMS  RESEARCH  INSTITUTE,  1994;  DIE-                ing techniques. If survey data are sparse but the morphology
FLORI.ANI and MAGILLO, 1994). One of the advantages of a          complex (i.e., submarine mounds, multiple bar and trough


                                           Journal of Coastal Research, Vol. 14, No. 1, 1998






                                     Monitoring Coastal Environments: Geospatial Methods                                      87



                   0
                   0


                                                                                              -N-
                   0

                   O4                       X


                         I\...~\\

                   o 13                        2 1










                   LO                  7 
                     .-           .    .      . \          *


                   oo 4i" x'l, 10    4







                   to    I     I~      I   "~
                                                     ~i/\
                    _ \ 's,,, ,A.^ ,, x',.


                    o 13               I           5 1 -  I-.\0 2                                 3
                                            "',   \ ~.',%-", - -\e.






                   3-                     11                                  5              '
                          o ' ._-~ ~                        ,   C-,_  - ....._C...,
                         o ~ ~ ~ ~ ~~', ,.'    -                '"..  .......






                     8    EAST PASS, DESTIN, FLORIDA
                   0
                   To
                   '~                  I       l7                            8                 9

                     1363000       1364000          1365000           1366000          1367000        1368000



                                 SCALE
                               0         1000 FT
                                                                         EAST PASS, DESTIN, FLORIDA
                                     ~~~~0  300  600  M           ~EBB-TIDAL SHOAL GROWTH
                        0          300         600 M                                  97-10
                         I            I            T                                 1967 - 1990

                                  LEGEND                                      ALL COORDINATES ARE:
                                                                          PLANE COORDINATES
                          JUNE  1967                    .............LAMBERT CONFORMAL PROJECTION
                          APRIL  1969 -                   -----STATE OF FLORIDA, NORTH ZONE
                           MAY  1970                                      (LINES REPRESENT -4.57 M MLLW)
                           MAY 1 970
                            JAN  1974
                           JULY  1983 .-------
                      OCTOBER  1986 ------ -
                     FEBRUARY 1990-----
Figure 21. Overall growth of an ebb-tidal shoal over 24 years is shown by the advance of the 15-ft (4.5-m) isobath. This isobath was chosen because it
represented approximately the mid-depth of the bar front. The 1000-ft (305-m) squares are polygons used for volumetric computations (MoRANG, 1992).



features) or if there are structures such as jetties, groins, and     exclusion boundaries, TIN models can describe very complex
breakwaters present, the resultant contours may be angular            terrain. Exclusion boundaries define explicitly the lines along
or contain spikes. When this occurs, the user needs to eval-          which abrupt changes in surface behavior occur (for example,
uate the original data points, line segments between data             along jetties). Quality review is key at each procedural step
nodes, and the visible surface of the triangulated network to         to ensure that the basic trends of the bathymetric data are
determine the source of error. With the use of breaklines and         accurately represented.



                                         Journal of Coastal Research, Vol. 14, No. 1, 1998






88                                                 Gorman, Morang and Larson






                o a.:2 -:. .-*-


                0                                                .    .... 
                0           (/1











                                   ',,:,:,?#5..













                        ,AST PASS, FLORIDA
                0 ....-.











                o
                o           1967  -  1990
                0
                   1363000 1364000   1365000   1356000   1367000 1368000
Figure 22. Isopach map showing overall changes in bottom configuration between 1967 and 1990 at East Pass, Florida. Solid contours (2-ft interval)
represent erosion, while dashed represent deposition. The migration of the channel thalweg to the east is obvious, as is the growth of scour holes at the
jetties. Map computed by subtracting June 1967 surface from February 1990 surface (MORANG, 1992).



Applications and Display of Gridded Data                            Volumetric data can be used to estimate growth rates of
                                                               features like shoals. As an example, using all 18 of the
  Contouring of an area is one of the most common applica-        1,000-ft squares shown in Figure 21, the overall change in
tions of mapping software (Figure 20). Not only is this faster    1,000-ft       squ are s   shown in Figure 21, the overall chang
                                                               volume of the East Pass ebb-tidal shoal between 1967 and
than hand-contouring, but the results are uniform in style
                                                               1990 was only 19 percent (Figure 23). Although the shoal had
across the area and precision (i.e., repeatability) is vastly su-  1990 as only 19    entthFigst, the minor overall increase in
                                                               clearly grown to the southwest, the minor overall increase in
  The power of                                                  mappiograms.is best demonstrated  volume suggests that considerable sand may have eroded
  The power of mapping programs is best demonstrated
                            The. power of. ma g p s i           from the inner portions of the shoal. In contrast, when plot-
when analyzing different surveys. If at all possible, the dif-
ferent data sets should be gridded with the same algorithms       tig the change in volume of nne selected squares, the
                                                               growth over time was 600 percent. This underscores how crit-
and parameters in order that the results be as comparable
as possible. Difficulty arises if earlier surveys contain much    ically numerical values such as growth rats depend upon the
                sparser data than later ones. Under these circumstances, it  boundaries of the areas used in the calculations. The user of
sparser data than later ones. Under these circumstances, it
is probably best if the optimum grid is chosen for each data      secondary data beware!
set. A simple application is to plot a suitable contour to dem-
                                                               Error Analysis of Gridded Bathymetry
onstrate the growth over time of a feature like a shoal (Figure
21). Computation of volumetric changes over time is another         A crucial question is how much confidence can a researcher
application (Figure 22). This can graphically demonstrate         place on growth rates that are based on bathymetric or to-
how shoals develop or channels migrate.                           pographic data? Unfortunately, in the past many researchers



                                         Journal of Coastal Research, Vol. 14, No. 1, 1998






                                      Monitoring Coastal Environments: Geospatial Methods                               89


                                                              Note that this is for a Corps of Engineers Class i survey;
     6.0                                                        many offshore reconnaissance surveys are not conducted un-
         Jetty constru                                          der such tight specifications. If Az = 1.5 ft (0.46 m) for Class
         Jetty Constructon                   -'~-------         3, then MLE for the above example = 91 percent. Under
                                                              these circumstances, it becomes meaningless to say that an
                                                              area has changed in volume by a certain amount ï¿½ 91 per-
     4.0     "     '                                            cent.
                                                                 The size of the polygons used in the calculation of Azav, can
a) 2                                                            influence the MLE. A particular polygon that covers a large
  . 3.0
                                                               area may average Az of only 0.3 or 0.6 m, but water depths
_iP                                                              from spot to spot within the polygon may vary considerably
     ~P2.0                                                      more. Therefore, by using smaller polygons, Az will typically
                                                              be greater and MLE correspondingly less. However, the use
                                                              of smaller polygons must be balanced against the fact that
                                                               positioning errors (Ax and Ay) become correspondingly more
                                                               significant.
     0.0     .... . . . . . .                                     More research is needed to quantify errors associated with
      1967    1971    1975    1979    1983    1987    1991      various types of offshore surveys and to identify how these
Figure 23. Growth of the ebb-tide shoal, East Pass, Florida. Areas used  errors are passed through computed quantities. They must
in the computations are shown in Figure 21. Growth rates are dramati-  not be neglected when analyzing geologic data, particularly if
cally different depending upon which polygons are included in the corn-  management or policy decisions will be based on perceived
putations.                                                       trends.


                                                                          SUMMARY AND CONCLUSIONS
ignored or conveniently overlooked the possibility that error      Most changes in the coastal zone are associated with inlet,
bars may have been greater than calculated trends, particu-      beach, and nearshore zone dynamic processes. Frequently,
larly when volumetric computations were based on data of         the natural processes in coastal areas are interrupted by hu-
questionable quality.
                questionable quality. ~~~~~man development and related construction. The most useful
  This section outlines a basic procedure that can be used to     an development and  elate        the                 se
calculate volumetric errors provided that estimates of the           costalfctive me         to    map  and evar e thea-
vertical (Az) accuracy are available. If Az values are unavail-  coastalschangeseareston,    and  ompare p    rologic fe
                                                  ï¿½ 0.5,ï¿½ 1.0, tures, shoreline position, and offshore profiles and to use
able for the specific surveys, standard errors of                these data to quantify nearshore sediment losses and gains.
or ï¿½ 1.5 ft, based on the class of the survey, can be used (see    The key data sets-aerial photography, shoreline position
discussion of hydrographic survey standards in Paper 3 of        change, and bathymetry-provide qualitative and quantita-
this series (MonMa, LARSON, and GORMAN, 1996) orHE-
thisRseries (MoRANGN, Uan   (1994)). For HEAstal surveysclotive answers to the stability and behavior of the shoreface
                                                               and nearshore zone. Many classical coastal studies have used
shore, this method assumes that errors in positioning (Ax and                            y
Ay) are random and have insignificant effect on the volumes               and overla nd datsore ton           ment A e-
compared with possible systematic errors in water depth          al    photonrthy ofte n  sershe endionmenta se-
measurements, tide correction, and data reduction. For older      ial largrale  oftu res as the
historical surveys, positioning error may be important, re-   b each  small and aropri ate gross the
                quirng amuchmorecompicaed aalyss prcedue. Psi-  beach system. Additionally, with appropriate ground control,
quioing accurach more hyrogaplicated s ys is detailedur. Psi-    the high waterline (optimum shoreline) can be digitized from
tioning accuracy of hydrographic surveys is detailed in I-EAD- aalbeara htsa ato  rjc' hrln aa
                QUARTERS,  SACE (199) and UMBAH (1976).available aerial photos as part of a project's shoreline data-
QUARTERS, USACE (1994) and UMBACH (1976).bae
  The error in volumetric difference between surveys can be       ase.
                estiatedby dtermninghow  uch  he aerag  deph in   There are numerous shoreline maps available through Fed-
estimatd pyg   changesromin hon  murvy the anherae andethen      eral, State, and local agencies that can serve as the project's
calculating an average depth change over all polygons. Max-
imum likely error (MLE) is:                                      in setting up a large shoreline data base is assessing and
                                                               documenting map accuracy, quantifying errors, and recording
                             2 X Az                             the lineage of data transformations and processing. Quanti-
                     MLE =  Az (3) fying errors is vital to the validity of the final results. It is
                                                               critical that engineering decisions or management initiatives
For example, if Az = 0.5 ft (0.15 m) and Aze = 1.0 m, then       be based on maps that have been produced from the best data
MLE is:                                                          available and with the most meticulous standards in digitiz-
                                                               ing and converting historical data. With the increasing use
               0.30 mn = 0.30 = 30 percentof Geographic Information Systems for coastal mapping, data
                1.00 m                                           sets can now be attributed and documented so that future



                                          Journal of Coastal Research, Vol. 14, No. 1, 1998






90                                                    Gorman, Morang and Larson


users will have a convenient means to evaluate how the data           BYRNES, M.A.; McBRmE, R.A.; UNDERWOOD, S.G., and CORBLEY,
were prepared.                                                          K.P., 1994. Losing ground: mapping Louisiana's disappearing
                                                                        coastline. GPS World, 5(10), 46-50.
  Because most of the beach is influenced by swash process-           CAMPBELL, J., 1991. Map Use and Analysis. Dubuque, Iowa: Brown,
es, sediments move cross-shore and alongshore. Sediment                 429p.
losses and gains on the lower portion of the beach are typi-          CHIU, T.Y., 1977. Beach and dune response to Hurricane Eloise of
cally evaluated based on volumetric changes computed from               September 1975. Proceedings Coastal Sediments '77, American So-
                                                                        ciety of Civil Engineers (New York), pp. 116-134.
a time series of water depths referenced to the same vertical           ciety of Civil Engineers (New York), pp. 116-134.
                                                                      CLARKE, K.C., 1990. Analytical and Computer Cartography. Engle-
datum. Documentation of accuracy and estimation of poten-               wood Cliffs, New Jersey: Prentice-Hall, 290p.
tial errors should be applied to all bathymetric survey data,         CLAUSNER, J.E.; BIRKEMEIER, W.A., and CLARK, G.R., 1986. Field
and final shoreline change rates and volumetric calculations            comparison of four nearshore survey systems. Miscellaneous Paper
should be reported in the light of the maximum cumulative               CERC-86-6, U.S. Army Engineer Waterways Experiment Station,
                                                                        Vicksburg, Mississippi.
errors that may occur. Quality control in data collection, data       COLWELL, R.N. (ed.), 1983. Manual of Remote Sensing. Falls Church,
preparation, conversion, and analysis, and evaluation of er-            Virginia: American Society of Photogrammetry (in two volumes),
rors are among the most important elements to be empha-                 2440p.
sized in the technical assessment of a coastal project.               COORDINATING COMMITTEE ON GREAT LAKES BASIN HYDRAULIC
                                                                        AND HYDROLOGIC DATA, 1992. IGLD 1985. U.S. Government
                        ~ACKNOWLEDGEMENTS AND~ NOTES             ~      Printing Office, Washington, D.C. (Brochure on the International
        ACKNOWLEDGEMENTS AND NOTES                                      GetLksDtm18)
                                                                        Great Lakes Datum 1985).
  This paper was supported by various work units at the U.S           CROWELL, M.; LEATHERMAN, S.P., and BUCKLEY, M.K., 1991. His-
                  Army Engineer Waterways Experiment Station in particular  torical shoreline change: error analysis and mapping accuracy.
Army Engineer Waterways Experiment Station, in particularJoraofCstleerc,73   8952
                                                                        Journal of Coastal Research, 7(3), 839-852.
the Civil Works Guidance Update Program and the Coastal               CROWELL, M.; LEATHERMAN, S.P., and BUCKLEY, M.K., 1993. Shore-
Structures  Evaluation  and  Design  Program.  We  thank                line change rate analysis: long term versus short term data. Shore
Messrs. Mark Crowell and Larry Parson for reviews and con-              and Beach, 61(2), 13-20.
structive comments. Permission to publish this paper was              DALLY, W.R.; JOHNSON, M.A., and OSIECKI, D.A., 1994. Initial de-
                                                                        velopment of an amphibious ROV for use in big surf. Marine Tech-
granted by the Chief of Engineers, U.S. Army Corps of En-               nical Society Journal, 28(1), 3-10
gineers. Citation of trade names does not constitute an offi-         DEFLORIANI, L. and MAGILLO, P., 1994. Visibility algorithms on tri-
cial endorsement or approval of the use of such commercial              angulated digital terrain models. International Journal of Geo-
products.                                                               graphical Information Systems, 8(1), 13-41.
                                                                      DEAN, R.G., 1976. Beach erosion: causes, processes, and remedial
                   LITERATURE CITr                                      measures. CRC Reviews in Environmental Control. Vol. 6, Issue 3.
                                                                        Boca Raton, Florida: CRC Press, pp. 259-296.
ANDERS, F.J. and BYRNEs, M.A., 1991. Accuracy of shoreline change     DEAN, R.G., 1977. Equilibrium beach profiles-U.S. Atlantic and
  rates as determined from maps and aerial photographs. Shore and       Gulf coasts. Ocean Engineering Report No. 12, University of Del-
  Beach, 59(1), 17-26.                                                  aware, Newark, Delaware, pp. 1-45.
ANDERS, F.J.; REED, D.W., and MEISBURGER, E.P., 1990. Shoreline       DEAN, R.G., 1990. Equilibrium beach profiles: characteristics and
  movements; Report 2: Tybee Island, Georgia to Cape Fear, North        applications. Report UFL/COEL-90/001, Coastal and Oceano-
  Carolina: 1851-1983. Technical Report CERC-83-1, U.S. Army En-        graphic Engineering Department, University of Florida, Gaines-
  gineer Waterways Experiment Station, Vicksburg, Mississippi.          ville, Florida.
BARRICK, D.E.; EVANS, M.W., and WEBER, B.L., 1977. Ocean surface      DOLAN, R.B.; HAYDEN, B.; MAY, P., and MAY, S., 1980. Reliability
  currents mapped by radar. Science, 198, 138-144.                      of shoreline change measurements from aerial photographs. Shore
BASCOM, W., 1964. Waves and Beaches, the Dynamics of the Ocean          and Beach, 48(4), 22-29.
  Surface. Garden City, New York: Doubleday, 267p.                    DOLAN, R.; FENSTER, M.S., and HOLME, S.J., 1991. Temporal anal-
BIRKEMEIER, W.A., 1984. The Interactive Survey Reduction Pro-           ysis of shoreline recession and accretion. Journal of Coastal Re-
  gram: user's manual of ISRP. Instruction Report CERC-84-1, U.S.       search, 7(3), 723-744.
  Army Engineer Waterways Experiment Station, Vicksburg, Mis-         ELLIS, M.Y. (ed.), 1978. Coastal Mapping Handbook. Geological Sur-
  sissippi.                                                             vey, U.S. Department of the Interior, and National Ocean Survey
BIRKEMEIER, W.A., 1985. Field data on seaward limit of profile          and Office of Coastal Zone Management, U.S. Department ofComn-
  change. Journal of Waterway, Port, Coastal and Ocean Engineering,     merce, U.S. Government Printing Office, Washington, D.C, l99p.
  111(3), 598-602.                                                    ENVIRONMENTAL SYSTEMS RESEARCH INSTITUTE, 1994. Surface
BRUUN, P., 1954. Coast erosion and the development of beach pro-        modeling with TIN Redlands, California: Environmental Systems
  files. Technical Memorandum No. 44, Beach Erosion Board, U.S.         Research Institute, 260 p.
  Army Engineer Waterways Experiment Station, Vicksburg, Mis-         EOM STAFF, 1994. Defense contractors pursue growing markets in
  sissippi.                                                             the geotechnologies. Earth Observation Magazine, 11(3), 12-20.
BOWDITCH, N., 1981. American Practical Navigator; an Epitome of       ESTEP, L.L.; LILLYCROP, W.J., and PARSON, L.E., 1994. Estimation
  Navigation. Defense Mapping Agency Hydrographic/Topographic           of maximum depth of penetration of a bathymetric lidar system
  Center, Washington, D.C., 961p. (prepared by the U.S. Naval           using a Secchi disk database. Marine Technology Society Journal,
  Oceanographic Office).                                                28(2), 31-36.
BURROUGH, P.A., 1986. Principles of Geographic Information Sys-       GIS WORLD, 1995. GIS World Sourcebook 1996, Geographic Infor-
  tems for Land Resources Assessment. New York: Oxford University       mation System Technology. Fort Collins, Colorado: GIS World, Inc.,
  Press, 193p.                                                          747p. (Updated yearly).
BYRNEs, M.A. and HILAND, M.W., 1994. Shoreline position and           GORMAN, L.T. and REED, D.W., 1989. Shoreline response of the
  nearshore bathymetric change. In: KRAUS, N.C., GORMAN, L.T.,          northern New Jersey barrier system. Proceedings Coastal Zone
  and POPE, J., (eds.), Kings Bay Coastal and Estuarine Physical        '89, Barrier Islands: Process and Management, American Society
  Monitoring and Evaluation Program: Coastal Studies; Volume I,         of Civil Engineers (New York), pp. 122-137.
  Main Text and Appendix A, Technical Report CERC-94-9, U.S.          GORMAN, L.T.; PITCHFORD, K.R., STAUBLE, D.K., and LANGSTON,
  Army Engineer Waterways Experiment Station, Vicksburg, Mis-           J.T., 1995. Appendix D, survey and sediment grain-size data. In:
  sissippi, pp. 61-144.                                                 KRAUS, N.C.; GORMAN, L.T., and POPE, J., (eds.), Kings Bay



                                             Journal of Coastal Research, Vol. 14, No. 1, 1998






                                          Monitoring Coastal Environments: Geospatial Methods                                        91


  Coastal and Estuarine Physical Monitoring and Evaluation Pro-        LEATHERMAN, S.P., 1984. Shoreline evolution of north Assateague
  gram: Coastal Studies; Volume II: Appendices B-G, Technical Re-        Island, Maryland. Shore and Beach, 52, 3-10.
 port CERC-94-9, U.S. Army Engineer Waterways Experiment Sta-         LEICK, A., 1990. GPS Satellite Surveying. New York: Wiley, 560p.
  tion, Vicksburg, Mississippi, pp. D1-D163.                           LILLESAND, T.M. and KIEFER, R.W., 1987. Remote Sensing and Im-
GREAT LAKES COMMISSION., 1986. Water Level Changes: Factors              age Interpretation. 2nd Edition. New York: Wiley.
  Influencing the Great Lakes. Great Lakes Commission, Ann Ar-         LILLYCROP, W.J. and BANIC, J.R., 1992. Advancements in the U.S.
  bor, Michigan.                                                         Army Corps of Engineers hydrographic survey capabilities: the
HALLERMEIER, R.J., 1977. Calculating a yearly depth limit to the          SHOALS system. Marine Geodesy, 15, 177-185.
  active beach profile. Technical Paper TP 77-9, U.S. Army Engineer    MCCULLAGH, M.J., 1988. Terrain and surface modeling systems:
  Waterways Experiment Station, Coastal Engineering Research             theory and practice. Photogrammetric Record, 12, 749-779.
  Center, Vicksburg, Mississippi.                                      MCDONALD, R.A., 1995. Opening the Cold War sky to the public:
HALLERMEIER, R.J., 1978. Uses for a calculated limit depth to beach       declassifying satellite reconnaissance imagery. Photogrammetric
  erosion. Proceedings of the Sixteenth Coastal Engineering Confer-      Engineering & Remote Sensing, 61(4), 385-390.
  ence, American Society of Civil Engineers (New York), pp. 1493-      MORANG, A., 1992. A study of geologic and hydraulic processes at
  1512.                                                                  East Pass, Destin, Florida. Technical Report CERC-92-5, U.S.
HALLERMEIER, R.J., 1981a. A profile zonation for seasonal sand           Army Engineer Waterways Experiment Station, Vicksburg, Mis-
  beaches from wavq climate. Coastal Engineering, 4(3), 253-277.         sissippi (in 2 volumes).
HALLERMEIER, R.J., 1981b. Terminal settling velocity of commonly       MORANG, A., 1993. Geologic and Physical Processes at a GulfofMex-
  occurring sand grains. Sedimentology, 28(6), 859-865.                  ico Tidal Inlet, East Pass, Florida. Ph.D. dissertation, Louisiana
HALLERMEIER, R.J., 1981c. Seaward limit of significant sand trans-        State University, Baton Rouge, Louisiana, 331p.
  port by waves: an annual zonation for seasonal profiles. Coastal     NELSON, L.J., 1994. Commercially available remote sensing imagery
  Engineering Technical Aide CETA 81-2, U.S. Army Engineer Wa-           now: what you can get, where. Advanced Imaging, 9(10), 48-52.
  terways Experiment Station, Coastal Engineering Research Cen-        OREGON, 1973. Oregon Estuaries. State of Oregon Division of State
  ter, Vicksburg, Mississippi.                                           Lands, Salem, Oregon.
HANDS, E.B., 1976. Observations of barred coastal profiles under the   PILKEY, O.H.; YOUNG, R.S.; RIGGS, S.R.; SMITH, A.W.S.; Wu, H.,
  influence of rising water levels, eastern Lake Michigan, 1967-71.      and PILKEY, W.D., 1993. The concept of shoreface profile of equi-
  Technical Report 76-1, U.S. Army Engineer Waterways Experi-            librium: a critical review. Journal of Coastal Research, 9(1), 225-
  ment Station, Coastal Engineering Research Center, Vicksburg,          278.
  Mississippi.                                                         PEUCKER, T.K.; FLOWER, R.L.; LITTLE, J.J., and MARK, D.M.,
HARRIS, D.L., 1981. Tides and tidal datums in the United States.          1976. Digital representation of three-dimensional surfaces by tri-
  Special Report No. 7, U.S. Army Engineer Waterways Experiment          angulated irregular networks (TIN). Technical Report No. 10,
  Station, Coastal Engineering Research Center, Vicksburg, Missis-       U.S. Office of Naval Research, Geography Programs, Washing-
  sippi.                                                                 ton, D.C.
HEADQUARTERS, U.S. ARMY CORPS OF ENGINEERS, 1989. Water lev-           RICHARDS, J.A., 1986. Remote Sensing Digital Image Analysis, An
  els and wave heights for coastal engineering design. Engineer          Introduction. Berlin: Springer-Verlag, 281p.
  Manual EM 1110-2-1414. Washington, D.C.                              SABINS, F.F., JNR., 1987. Remote Sensing, Principles and Interpre-
HEADQUARTERS, U.S. ARMY CORPS OF ENGINEERS., 1990. Survey                tation. 2nd Edition. New York: Freeman, 449p.
  Umarkers  and monuSentation. Engineer Manual EM 1110-1-1002.         SAVAGE, R.J. and BIRKEMEIER, W.A., 1987. Storm erosion data from
  U.S. Army Corps of Engineers, Washington, D.C.                         the United States Atlantic coast. Coastal Sediments '87, American
HEADQUARTERS, U.S. ARMY CORPS OF ENGINEERS., 1994. Hydro                  Society of Civil Engineers (New York), pp. 1445-1459.
  graphic surveying. Engineer Manual EM 1110-2-1003. U.S. Army         SHALOWITZ, A.L., 1962. Shore and Sea Boundaries, with Special Ref-
                    graphic surveying. Engineer Manual  11erence to the Interpretation and Use of Coast and Geodetic Survey
  Corps of Engineers, Washington, D. C.                                  Data. Volume 1. Publication 10-1, U.S. Department of Commerce,
                  HEADQUARTERS, U.S. Amr CORS OF ENGINEERS., 1995. Coastal  Coast and Geodetic Survey, U.S. Government Printing Office,
  geology. Engineer Manual EM 1110-2-1810. U.S. Army Corps of            Washington         , D .C., 42Gp.
  Engineers, Washington, D.C.
                   ~~Engineers, Washington, D.C.  ~SHALOwiTZ, A.L., 1964. Shore and Sea Boundaries, with Special Ref-
HEMSLEY, J.M., 1981. Guidelines for establishing coastal survey          erence to the Interpretation and Use ofCoast and Geodetic Survey
  base lines. Coastal Engineering Technical Aid No. 81-15, U.S.          Data. Volume 2. Publication 10-1 U.S. Department of Commerce,
  Army Engineer Waterways Experiment Station, Coastal Engi-              Coast and Geodetic Survey, U.S. Government Printing Office,
  neering Research Center, Vicksburg, Mississippi.                       Washington, D.C., 749 p.
HICKS, S.D., 1984. Tide and Current Glossary. National Oceanic and     SOMMERFELD, B.G.; MASON, J.M.; KIAUS, N.C., and LARSON, M.,
  Atmospheric Administration, National Ocean Survey, U.S. De-             1994. BFM: Beach Fill Module; report 1, Beach Morphology Anal-
  partment of Commerce, Washington, D.C., 30p.                           ysis Package (BMAP)-user's guide. Instruction Report CERC-94-
HOROWITZ, R. and KING, J.H., 1990. NSSD.C data listing. Report           1, U.S. Army Engineer Waterways Experiment Station, Vicks-
  No: NAS 1.15:102989; NSSD.C/WD.C-A-RIS-90-06; NASA-TM-                 burg, Mississippi.
  102989, Goddard Space Flight Center, National Aeronautics and        STAUBLE, D.K., 1992. "Long term profile and sediment morphody-
  Space Administration, Greenbelt, Maryland.                             namics; Field Research Facility case history," Technical Report
HuH, O.K. and LEIBOWITZ, S.G., 1986. User's guide to image pro-           CERC-92-7, U. S. Army Engineer Waterways Experiment Station,
  cessing; applications of the NOAA satellite HRPT/AVHRR data,           Vicksburg, MS.
   Technical Report TR 301.86, Remote Sensing and Image Process-        STAUBLE, D.K., 1994. A Physical Monitoring Plan for Northern As-
   ing Laboratory, Louisiana State University, Baton Rouge, Loui-         sateague Island, Maryland. Final report prepared for U.S. De-
  siana.                                                                 partment of the Interior, National Park Service, Mid-Atlantic
KoMAR, P.D., 1976. Beach Processes and Sedimentation. Englewood          Region and Assateague Island National Seashore by the U.S
  Cliffs, New Jersey: Prentice Hall, 429p.                               Army Engineer Waterways Experiment Station, Vicksburg, Mis-
KORTE, G.B., 1994. The GIS Book. Santa Fe, New Mexico: OnWord            sissippi.
   Press, 166p.                                                         STAUBLE, D.K.; GARCIA, A.W.; KRAUS, N.C.; GROSSKOPF, W.G., and
KRAUS, N.C. and HARIKAI, S., 1983. Numerical model of the shore-         BASS, G.P., 1993. Beach nourishment project response and design
   line change at Oarai Beach. Coastal Engineering, 7(1), 1-28.           evaluation, Ocean City, Maryland. Technical Report CERC-93-13,
LAMPMAN, J.L., 1993. Bibliography of remote sensing techniques           U.S. Army Engineer Waterways Experiment Station, Vicksburg,
   used in wetland research. Wetland Research Program Technical           Mississippi.
  Report WRP-SM-2, U.S. Army Engineer Waterways Experiment             STEWART, R.H., 1985. Methods of Satellite Oceanography. Berkeley,
   Station, Vicksburg, Mississippi.                                       California: University of California Press, 360p.



                                               Journal of Coastal Research, Vol. 14, No. 1, 1998






92                                                    Gorman, Morang and Larson


SWANSON, R.L., 1974. Variability of Tidal Datums and Accuracy in      U.S. COAST AND GEODETIC SURVEY, 1985. Datum Differences-At-
  Determining Datums from Short Series of Observations, National        lantic, Gulf, and Pacific Coasts, United States. Washington, D.C.
  Ocean Survey, Rockville, Maryland, 41p.                             U.S. GEOLOGICAL SURVEY, 1989. North American Datum of 1983:
TANNER, W.F., (ed.), 1978. Standards for Measuring Shoreline            Map Data Conversion Tables. U.S. Government Printing Office,
  Changes: A Study of the Precision Obtainable and Needed in Mak-       Washington, D.C. (prepared with U.S. Department of Commerce,
  ing Measurements of Changes (erosion and accretion). Proceedings      National Oceanic and Atmospheric Administration).
  of a Workshop, Florida State University, Tallahassee, Florida.      WALTON, T.L., JNR., 1990. Simulating Great Lakes water levels for
TSAI, V.J.D., 1993. Delaunaytriangulations in TIN creation: an over-       ero     sion prediction. Miscellaneous Paper CERC-90-6, U.S. Army
  view and a linear-time algorithm. International Journal of Geo-       Engineer Waterways Experiment Station, Vicksb urg, Mississippi.
                                                                      WEGGEL, J.R., 1995. A primer on monitoring beach nourishment
  graphical Information Systems, 9(6), 501-524.                         projects. Shore & Beach, 63(3), 20-24.
UnteACH, M.J. (Commander, NOAA), 1976. Hydrographic Manual.             poet.Soe&Bah  33,2-4
                 UMBACH, M.J. (Commander, NOAA), 1976. Hydrographic Manual.  WRIGHT, L.D. and SHORT, A.D., 1983. Morphodynamics of beaches
  4th Edition. U.S. Department of Commerce, National Oceanic and        and surf zones in Australia. In: KomAR, PD., (ed.), Handbook of
  Atmospheric Administration, National Ocean Survey, Washing-           Coastal Processes and Erosion. Boca Raton, Florida: CRC Press,
  ton, D.C. (with updates 1979, 1980, 1981).                            pp. 35-64.
U.S. ARMY ENGINEER DISTRICT, JACKSONVILLE, 1993. Nassau               WRIGHT, L.D.; BooN, J.D.; KIM, S.C., and LIST, J.H., 1991. Modes
  County, Florida, Fernandina Harbor, Section 933 study. Jackson-       of cross-shore sediment transport on the shoreface of the Middle
  ville, Florida.                                                       Atlantic Bight. Marine Geology, 96, 19-51.





























































                                              Journal of Coastal Research, Vol. 14, No. 1, 1998