extensive low- lying areas surrounding them which may be subject to exten- 

 sive flooding during severe storm conditions. Also, these basins are 

 usually shallow, and on the windward side of the basin substantial bottom 

 areas can become exposed. Thus, during the passage of a storm system, 

 many semienclosed basins have time-dependent moving boundaries. The 

 water present at any time in a bay or estuary is also dependent upon the 

 sea state because of the interrelation between these two bodies of water. 

 Because of the above characteristics of semienclosed basins, a simplified 

 approach does not usually provide a satisfactory estimate of water motions, 

 and methods based on full two-dimensional dynamic approaches should be 

 employed. 



3-143 



