decide how well the estimate for the nearby site predicted the longshore trans- 

 port rate. For example, was the dredging maintenance schedule or the fillet 

 growth of a jetty predicted with adequate accuracy? If satisfied that it was, 

 the two sites should be compared for similarity. Some items to check are: 



(1) Sediment sources and sinks [may affect one site but not the 

 other; examples of sediment sources are eroding bluffs and river sedi- 

 ment discharge, and examples of sinks are offshore canyons and inlet 

 shoals). 



(2) Shoreline orientation (can control which waves reach the shore- 

 line from which direction). 



(3) Offshore bathymetry (controls refraction of waves, thereby 

 affecting the wave climate; examples are shoals and canyons). The 

 bathymetry also controls wave energy dissipation due to bottom fric- 

 tion (see Bretschneider and Reid, 1954). 



(4) Offshore islands (can block waves from certain directions). 



(5) Coastal structures (groins and jetties can block longshore 

 transport; offshore and submerged breakwaters can block waves). 



Based on this comparison of the two sites, an estimate can then be made of 

 the longshore transport rate at the location in question by using engineering 

 judgment to increase, decrease, or leave unchanged the transport rate at the 

 nearby site. 



2, Method 2 . 



Method 2 is an application of historical data which gives usable answers if 

 the basic data are reliable and available at reasonable cost and the interpre- 

 tation is based on a thorough knowledge of the locality. 



Some indicators of the transport rate are the growth of a spit, shoaling 

 patterns and deposition rates at an inlet, and the growth of a fillet adjacent 

 to a jetty or groin. As an example, the longshore transport rate across Cold 

 Spring Inlet, New Jersey, was estimated based on fillet growth next to the 

 tpdrift jetty -and surveys of the surrounding area to account for the sand that 

 was not impounded by the jetty (Beach Erosion Board, 1953). The rates of growth 

 for Sandy Hook, New Jersey (U.S. Army Engineer District, New York, 1954) and for 

 Sheshalik Spit, Alaska (Moore and Cole, 1960), were used to estimate longshore 

 transport rate. Bruno and Gable (1976) measured the deposition behind the off- 

 shore breakwater and adjacent to the updrift jetty at Channel Island Harbor, 

 California, to find the longshore transport rate. Various methods of finding 

 longshore transport rates including surveys, aerial photos, dredge records of 

 a tidal inlet, and a quantitative analysis of eroding sources of sand are dis- 

 cussed in Beach Erosion Board (1954) . 



3. Method 3 . 



This method of con^juting longshore transport rate is based on the empirical 

 relationship between the longshore conponent of wave energy flux entering the 



