by Pilkey et al . (1981) has emphasized this large and frequently overlooked sea- 

 level factor in unequivocal terms. 



As stated in the introduction, no attempt has been made to provide complete 

 references. However, the reader is encouraged to consult the follovn'ng papers as a 

 sample of some of the significant literature: Bruun (1962), Hands (1980), 

 Leatherman (1979, 1981), Meisburger et al . (1980), Pilkey et al. (1980), and 

 Schwartz (1965, 1967). 



With any rise in water level, the shoreline moves inland an amount equal to the 

 product of the rise and the cotangent of the angle of land slope. Obviously, the 

 inland movement is small on relatively steep rocky coasts and large on relatively 

 flat deltaic coasts, salt marshes, mangrove swamps, et cetera. The slope on an 

 exposed beach is somewhat deceiving. The water does not ride up the slopes of the 

 various features making up the beach profile. The water rides on an "effective" 

 slope (not necessarily linear) through these beach features at some lower angle. A 

 representative value for shore retreat is 40 to 1 (Hands, 1979). The beach features 

 themselves are in equilibrium (or trying to get into equilibrium) with the 

 prevailing dynamic forces and, under ideal conditions, would also migrate inland 

 along this effective slope with the redistribution of shore material. 



As previously mentioned, the entire spectrum of water-level changes includes 

 such oscillations as annual variability, seasonal change, tidal cycle, storm surge, 

 wind setup, et cetera. The oscillations vary in magnitude and time, whether 

 periodic or not. With any incremental increase in water level, the dynamic forces 

 (variable themselves) will try to reestablish the shore in equilibrium. The success 

 will be a function of the magnitude of the dynamic forces, the shore material, and 

 the length of time the water is at this new elevation. Now the importance of the 

 secular rise in relative sea level is simply that it is very slow , thus allowing the 

 dynamic forces time to establish their new equilibrium progressively landward 

 (Hands, 1976). 



The process is far more complicated when considering the many additional 

 factors such as: longshore transport, that it is not a closed source system, and 

 man's intervention. The simplification is only intended to help isolate the impor- 

 tance of the sea-level factor. 



10 



