shore characteristics and often penetrate well inland of the shore zone because 

 of high waves and storm surges. 



In addition to cyclic seasonal patterns, many areas are being affected by 

 long-term unidirectional trends in a particular environmental factor, which 

 causes continuous adjustments in morphology. For example, a rising relative 

 sea level usually results in shore erosion and progressive landward retreat of 

 the shoreline. Evidence of past or ongoing changes, and the rates of these 

 changes, need to be taken into account for planning and management of 

 engineering activities. 



A rapid change in coastal morphology, due to an intense storm or other 

 event that causes a feature to be out of equilibrium with the prevailing envi- 

 ronmental factors can lead to significant long- and short-term trends. 

 Unidirectional trends are observed until the normal balance or equilibrium is 

 restored. In some cases, the effects of an extreme event may become 

 permanent because normal processes are unable to restore the old equilibrium. 



Several types of unidirectional trends caused by extreme events are 

 possible. For example, beach and dune sands lost to storm overwash deposits 

 caimot be returned because there is no process that can move the material 

 back toward the shore, except for minor eolian transport. Thus, most of the 

 material will not reenter the shore area unless barrier recession eventually 

 reexposes it on the seaward side. Also, if island breaching occurs during 

 storms, inlets may develop and enlarge unless littoral drift processes work to 

 close them. 



The identification and analysis of trends in coastal geomorphic processes 

 and features are of great importance in the planning and design of coastal 

 engineering efforts and of long-range management plans. Indeed, in many 

 cases, the purpose of coastal engineering works may be to modify or com- 

 pensate for some trend that is producing undesirable effects. Since each 

 location is unique geomorphically, exhibiting different types of changes, 

 management and structural techniques that are appropriate for a given site 

 might not be appropriate for others. In summary, although coastal 

 geomorphology displays many general trends, unique conditions at each 

 location must be identified and evaluated before initiating engineering projects 

 or long-term management practices. 



Historical Charts and Aerial Photographs 



Detection of long-term trends is often difficult because these processes are 

 often relatively slow on human time scales. However, trends may be 

 identified by comparative analysis of historical maps, charts, and aerial 

 photographs that show changes over a period of decades or centuries. 

 Historical charts and aerial photographs of many areas have been periodically 



Chapter 5 Investigation of Geomorphic Factors 



77 



