78 



resurveyed and fairly accurate surveys, going back in some cases 150 years or 

 more, are available for most US coastal areas. 



The primary source of chart data is the NOS and its predecessor, the 

 U.S. Coast and Geodetic Survey. Archive material for all past surveys of 

 these agencies is available from NOS, a division within NOAA. Much of this 

 data can be obtained in the form of preliminary plots that are of a larger scale 

 and contain more soundings and bottom notations than the published charts 

 made from them. Some of these data were used for regional studies of net 

 shoreline movement (Anders, Reed, and Meisburger 1990) (Figure 32). A 

 great variety of additional documentary evidence may also be available, as 

 described by Fulton (1981). This includes such items as local records and tax 

 assessments, which might be incorporated in background investigations of a 

 site if sufficient time exists to find these materials. 



Aerial photographs are another useful and economic technique for examin- 

 ing details of coastal features above the water line. The general turbidity of 

 coastal waters inhibits the application of photographic data of the offshore 

 bottom; however, in relatively clear shallow water, the crests of submarine 

 bars and shoals may be visible. Sources of aerial photography data are 

 numerous, including Federal, state, county, and local government agencies. 

 Aerial photography of coastal areas has been collected for about 60 years; 

 thus, it often can provide useful time series data on changing conditions. 

 Also, the effects of major events can be documented by aerial photography 

 because the necessary equipment and airplanes can be rapidly mobilized to 

 reach areas that are not easily accessible on the ground. 



Applications of aerial photographs include assessments of short-term and 

 long-term, as well as mesoscale and macroscale, coastal changes. The type of 

 information that can be derived depends in part upon the scale of the 

 photography, and also upon the historical nature of the database. The relative 

 accuracy of the surveys, maps, or aerial photographs will depend largely on 

 the scale of the initial photography; horizontal and vertical error increases 

 with smaller scale (Tanner 1978). 



Much information regarding local processes can be derived from maps and 

 aerial photographs. One example is the longshore movement of sediment, an 

 item of paramount interest to geologists and engineers because of its impor- 

 tance in coastline evolution. The geometry of coastlines in the vicinity of 

 headlands, tidal inlets and streams, and coastal structures is one key to 

 determine the directions of littoral transport (Figure 33). Storm impacts, 

 including island breaches, occurrence of overwash features, and changes in 

 inlets, vegetation, and dunes can be determined with time-series photography. 

 Problems with siltation of tidal inlets, river mouths, estuaries, and harbors can 

 also be examined using photographs. 



Large data sets of historical aerial photographs and maps can be used for 

 interpretating regional geomorphic changes in coasts. Using detailed historical 

 data, Dolan and Hayden (1983) were able to assess that shore processes and 



Chapter 5 Investigation of Geomorphic Factors 



