a. Sources of Data . The next step is to collect pertinent data. If the 

 problem area is located on a U.S. coastline, the National Shoreline Study may 

 be consulted. This study can provide a general description of the area and 

 may give some indication of the littoral processes occurring in the vicinity 

 of the problem area. 



Historical records of shoreline changes are usually in the form of charts, 

 surveyed profiles, dredging reports, beach replenishment reports, and aerial 

 photos. As an example of such historical data. Figure 4-51 shows the pos- 

 itions of the shoreline at Sandy Hook, New Jersey, during six surveys from 

 1835 to 1932. Such shoreline change data are useful for computing longshore 

 transport rates. The Corps of Engineers maintains, in its District and 

 Division offices, survey, dredging, and other reports relating to Corps 

 projects. Charts may be obtained from various Federal agencies including the 

 Defense Mapping Agency Hydrographic Center, Geological Survey, National Ocean 

 Service, and Defense Mapping Agency Topographic Center. A map called "Status 

 of Aerial Photography," which may be obtained from the Map Information Office, 

 Geological Survey, Washington, D.C. 20242, shows the locations and types of 

 aerial photos available for the U.S. and lists the sources from vAiich the 

 photos may be requested. A description of a coastal imagery data bank can be 

 found in the interim report by Szuwalski (1972). 



Other kinds of data usually available are wave, tide, and meteorological 

 data. Chapter 3 discusses wave and vater level predictions; Chapter 4, 

 Section III discusses the effects of waves on the littoral zone; and Chapter 

 4, Section III,d presents methods of estimating vave climate and gives 

 possible sources of data. These referenced sections indicate the wave, tide, 

 and storm data necessary to evaluate coastal engineering problems. 



Additional information can be obtained from local newspapers, courthouse 

 records, and area residents. Local people can often identify factors that 

 outsiders may not be aware of, and can also provide qualitative information on 

 previous coastal engineering efforts in the area and their effects. 



b. Interpretation of Shoreline Position . Preliminary interpretation of 

 littoral processes is possible from the position of the shoreline on aerial 

 photos and charts. Stafford (1971) describes a procedure for utilizing 

 periodic aerial photographs to estimate coastal erosion. Used in conjunction 

 with charts and topographic maps, this technique may provide quick and fairly 

 accurate estimates of shoreline movement, although the results can be biased 

 by the short-term effects of storms. 



Charts show the coastal exposure of a study site, and, since exposure 

 determines the possible directions from which waves reach the coast, exposure 

 also determines the most likely direction of longshore transport. 



Direction of longshore transport may also be indicated by the position of 

 sand accumulation and beach erosion around littoral barriers. A coastal 

 structure in the surf zone may limit or prevent the movement of sand, and the 

 buildup of sediment on one side of the littoral barrier serves as an indicator 

 of the net direction of transport. This buildup can be determined from 

 dredging or sand bypassing records or aerial photos. Figure 4-52 shows the 

 accumulation of sand on one side of a jetty. But wave direction and nearshore 

 currents at the time of the photo indicate that transport vas then in the 



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