Table 4-15. Classification of elements in the littoral zone sediment budget, 



Naturally occurring sources and sinks that usually are major elements in the sediment budget. 



to the littoral zone and according to the boundary across which the contri- 

 bution enters or leaves. Each of the elements is discussed in following 

 sections. 



The length of shoreline over which a line source is active is indicated by 

 b^ and the total contribution of the line source or line sink by Qv or 



Q^ , so that in general 



Qt = \^ 



(4-58) 



It is often useful to specify a source or sink as a fraction k^ of the 

 gross longshore transport rate: 



% = h% 



(4-59) 



In a complete sediment budget, the difference between the sand added by 

 all sources and the sand removed by all sinks should be zero. In the usual 

 case, a sand budget calculation is made to estimate an unknown erosion or 

 deposition rate. This estimated rate will be the difference resulting from 

 equating known sources and sinks. The total budget is shown schematically as 

 follows: 



Sum of Sources - Sum of Sinks = 0, or 



Sum of Known Sources - Sum of Known Sinks = Unknown (Sought) Source or Sink 



4-114 



