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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 Larson� tU.S. Army Engineer *U.S. Army Engineer �U.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 �,ee � �ee 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 � 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. � 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 72� N and equipped with the multispectral scanner, which has a reso- 72� 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 _ *� '..''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 - - , � W F i r z =~~~~~~~~~~~~~~~~~~~~~i 1U -li�--� ;~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~~~ � 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 7�' 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 - �\'., ....'"~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 -'� - - 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. �> 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 � 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 � 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 � <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 errao�oin a ndsddcd > o <'~~< 4 4% EXISTING STONE JETTY SECTION ~ o ~I-~n '%t~I %D \% .'' 0r� Ne.a C- Ga a a aan an a oooOoo dd dddo 7~p~ C). 4 t eim<?" q9s3 SO< Pf rO ,< 4a Y� n naa tot �a 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 �'- " ""- 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, � Processing of bathymetric data using mapping software display and plot it at different scales, and compare different o . . '' ' '' . '~.o .o . 0�Apliatinsdata 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-.- � 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-baed�oo asseblin bahyeti suvy'rmacatlaear- csigadpotn.I nyavr iie eini en x searcher isotn'ofote-ihanimneomutof data am d it *a�emr 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 tobebetween�2.0 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 CPSu3� 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 � 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) � Specifying gridding constraints * Least squares with smoothing * Computing the grid * Moving average � 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 � 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 � 0.5,� 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 � 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