1 Introduction 



Background 



Many geomorphic features are relatively stable and changes in their form 

 occur slowly; others are less stable and are subject to comparatively rapid 

 change in response to dynamic environmental factors. Variable features are 

 usually composed of unconsolidated or friable materials that react rapidly to 

 changes in the dynamic environment. More stable features are usually associ- 

 ated with consolidated rock and/or the absence of potent geological processes. 



Few geological envirormients contain a greater variety of dynamic 

 geomorphic features than the coastal zones of oceans and large lakes. Because 

 of the many variable features, complex processes, and submerged areas, study 

 and description of coastal areas present special problems that do not arise 

 when examining more stable environments. In general, study of coastal areas 

 requires a process-oriented approach and a larger database than are usually 

 needed for study of more stable and accessible environments. The large 

 database is needed for two principal reasons. First, time series data collection 

 on many variable geomorphic features is needed to determine the range of 

 temporal variability. Second, selection of representative data points and 

 projection of data by visual observation and aerial photography are not possi- 

 ble in submerged parts of the coastal zone. Consequently, a dense data matrix 

 is needed for an adequate and reliable representation of bottom morphology 

 and sediment distribution. 



Temporal variations in coastal geomorphology occur in: (a) cyclic 

 patterns; (b) as a result of intermittent noncyclic events; or, (c) as long-term 

 trends. Cyclic variations occur on a periodic or repetitious basis and are 

 generally related to processes like astronomical tide and seasonal sea and swell 

 patterns. Intermittent events are noncyclic occurrences such as large storms 

 or earthquakes. They are of relatively short duration but often have lasting 

 consequences for coastal morphology. Long-term trends include gradual 

 changes in relative sea level or climatic patterns which, in turn, cause slow 

 but often significant changes in coastal features or processes. Over the time 

 scales of modern process studies, they are considered noncyclic, although over 

 geologic time scales they may have a periodic component. The detection of 

 such long-term trends is often difficult, but they may be discovered by 



Chapter 1 Introduction 



