6 Summary and Conclusions 



Coastal environments show great geomorphic diversity over space and over 

 time. Spatial diversity occurs because coastal landforms develop in a variety 

 of terrestrial and marine environments, composed of materials that include a 

 variety of rocks and sediments. In addition, environmental factors, such as 

 coastal winds, waves, tides, currents, storms, sea level, tectonics, and 

 sediment supply show geographical variation. Temporal diversity in 

 landforms and materials occurs largely because envirormiental factors show 

 temporal variations. Temporal variations may be cyclic, noncyclic, or 

 unidirectional over the time period examined. The geomorphic variability of 

 coasts reflects the multiplicity of geomorphic and geologic responses over a 

 variety of time scales. 



Types of geomorphic zones include (a) beaches and the nearshore zone, 

 (b) coastal dunes, (c) the shoreface, (d) inlets, (e) shelf shoals, (f) deltas, 

 (g) estuaries, (h) reefs, (i) mudflats and mangroves, (j) strand plains, and 

 (k) cliff coasts. It is an important aspect of engineering and geologic studies 

 to assimilate and interpret evidence regarding geomorphic variability over the 

 multiple time scales that occur in these wide-ranging coastal environments. 



Study of the geomorphic variations of coasts can be approached over a 

 variety of time scales. Three principal time scales that are important in 

 assessing geologic and geomorphic changes in coasts include the following: 

 (a) modern studies based largely on field data or laboratory and office 

 experiments regarding envirormiental processes; (b) historic studies based 

 largely on information from maps, photography, archives, and other sources; 

 and, (c) paleoenvironmental studies based largely on stratigraphy and 

 associated geological and paleoenvironmental principles. In actuality, 

 however, these general time scale approaches show overlap. Further, within 

 each of the categories, certain time scales may be of particular importance for 

 influencing coastal changes. For example, tidal and seasonal changes are 

 significant in modern studies and Holocene sea level history is important in 

 paleoenvironmental studies. 



Many coastal geomorphic features are temporally variable and tend to 

 change form with changes in certain critical environmental factors. Some of 

 these changes are cyclic and relate mainly to seasonal variations in wave 

 climate; others are the result of rare intermittent events such as major storms 



Chapter 6 Summary and Conclusions 



