TIDAL INLET OR STREAM 



BEACH RIOGE HEADUNDS 



BREAKWATER 



OFFSHORE BREAKWATER 



Figure 33. Morphologic indicators of littoral drift along natural and modified shorelines. 



Natural features such as rock headlands show accretion on the updrift side and 

 erosion on the downdrift side (A), tidal inlets and spits show extension in a 

 downdrift direction (B-C), and beach ridge headlands show successive growth 

 on the updrift end influenced by the development of coastal cells, which form 

 shoreline irregularities (D). Coastal engineering structures including groin fields, 

 jetties, seawalls, attached breakwaters, and detached breakwaters (E-l) 

 generally show accumulation of sediment on the updrift side, and reduced 

 sediment supply on the downdrift side 



landforms assume systematic, as opposed to random, patterns both along and 

 across the coast. Large storms caused severe erosion in the same locations as 

 previous storms of lower severity. Long-term erosion rates can be examined 

 even over large areas (Dolan, Hayden, and May 1983). Such studies can then 

 be used to assign temporal probability levels to the distribution of coastal 

 change rates and thus predict shoreline positions several years beyond the data 

 set (Dolan et al. 1982; Dolan and Hayden 1983). Clues regarding the influ- 

 ence of natural and human-induced wetland changes can also be found by 

 interpretation of historical maps and photographs (May and Britsch 1987). 



80 



Chapter 5 Investigation of Geomorphio Factors 



