73. Other types of data may be required in certain situations. Some of 

 these items are difficult to quantify, such as permeability factors for groins 

 and transmission factors for detached breakwaters; nevertheless, estimates 

 must be made. Final values of these ambiguous quantities are usually deter- 

 mined in the model verification process. In these situations, special care 

 must be given to check inferences against field data on shoreline change at 

 the site. 



Regional sediment transport 



74. Sediment transport and shoreline change at the site should be 

 interpreted within a regional context, as there may be a "far field" effect on 

 the project from processes quite distant from it and vice versa. If possible, 

 the project is placed within the context of a littoral cell, which is a 

 coastal area defined by known or well-estimated sediment fluxes at lateral 

 boundaries. Examples of good lateral boundaries are large inlets and 

 entrances, harbor breakwaters and long jetties, and regions that have experi- 

 enced little shoreline change. A sediment budget is made for the littoral 

 cell (Shore Protection Manual (SPM) 1984, Chapter 4), and this analysis may be 

 repeated in gradual stages of sophistication, leading into a production 

 modeling effort with GENESIS. Such a simple budget analysis might be termed 

 "first-order modeling" and gives an integrated and regional perspective of the 

 dominant processes to serve as guidance in interpreting the more extensive and 

 quantitative results produced by shoreline change models. Information that 

 should be gathered in this task are estimates of direction and amounts of net 

 longshore sediment transport; gross sediment transport; trends in shoreline 

 change; and seasonal variations in waves, currents, sediment transport, and 

 beach change . 



Regional geology 



75. Collection and analysis of geologic and geomorphic data are linked 

 with the study of regional transport processes in development of the sediment 

 budget. Typical subjects of the regional geology portion of the study include 

 estimation of the effects of inlets, both as sources and as sinks of littoral 

 material; river discharges; special sources of littoral material, such as 

 cliffs; sea level rise and subsidence; and analysis of grain size. The 



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