While a considerable amount of data exist on the coastal and oceanic pro- 

 cesses of the US coasts, there are few field studies in which data on 

 geomorphic changes and relevant processes were obtained concurrently. Such 

 data are critically needed for many areas in order to validate existing models 

 of process/response relationships under a variety of conditions. 



Wave data is one of several components required to characterize the 

 process-response framework of the coastal zone. Important wave parameters 

 include wave height, period, and steepness, and breaker type. The estimated 

 height is often given as the significant wave height (H 1,3), the average of the 

 highest one-third of waves, or as the maximum height (H 1/10), the average of 

 the highest one-tenth of the waves. Significant wave height may be used to 

 compute other wave statistics (Shore Protection Manual 1984). 



Certain wave characteristics are strongly related to morphologic variables. 

 Wave steepness, for example, is an important variable in determining fore- 

 shore slope, which explains changes in beach profile characteristics from 

 summer to winter (Shepard and LaFond 1940; Saville 1950; Bascom 1954). 

 Other wave characteristics, including the surf scaling factor and breaker type 

 are important in determining beach profile characteristics (Wright et al. 1979; 

 Huntley and Bowen 1975). Other parameters, such as shore-normal currents 

 and sediment grain size, should also be considered in conjunction with wave 

 variables in order to thoroughly understand beach profile development (Sonu 

 and van Beek 1971; Iwagaki and Noda 1963; Komar 1976). 



Wave climate data can also be used in conjunction with bathymetric data to 

 construct wave refraction diagrams, which provide an indication of how 

 bottom topography can affect the bending of waves approaching a shoreline. 

 Such studies can help in determining mass transport and longshore transport of 

 sediment, which in turn can assist in predicting morphologic changes, and in 

 design of coastal engineering projects. Wave refraction analysis can also be 

 used for hypothetical scenarios, for instance, how wave energy and associated 

 littoral conditions would be affected by the dredging of an offshore shoal or 

 offshore placement of dredged material. 



Water Level 



Water level measurements represent the combined effects of tides, setup or 

 setdown by onshore or offshore winds, eustatic changes, and vertical crustal 

 displacements Figures 27-31). Short-term variations, particularly those 

 associated with storms, are important in increasing the effective wave base. 

 This allows erosion to take place farther inland than during mild weather 

 periods. Long-term variations in sea level, while of much lower intensity than 

 surf processes, can be important in predicting erosion or accretion and 

 changes in beach profile response (e.g.. Wells and Coleman 1981b; Hands 

 1983). 



Chapter 4 Investigation of Environmental Factors 



69 



