Wave Information Study (WIS) . Hindcasting of historical wave conditions 

 on the Nation's coastline is on ongoing mission of the Corps of Engineers. 

 Pacific coast wave hindcasts for the years 1956-1975 were beginning at the 

 onset of the Bolsa Chica studies. With augmented funding through SLC, WES was 

 able to complete a 20-year wave hindcast for the Bolsa Chica region so that 

 results could be incorporated into this study. The purpose of the numerical 

 wave hindcast effort was to provide reliable estimates of wave conditions 

 occurring at the project site for use in the comprehensive shoreline response 

 model and in the physical model of the proposed entrance channel . 



The WIS hindcast starts with synoptic -scale pressure charts of the Pacific 

 Ocean (in this case) , and processes these data numerically to generate wind 

 fields over the ocean basin. The winds are then input to a numerical wave 

 prediction model that provides directional wave spectra at deepwater grid 

 points along the coastline. Next, a spectral transformation numerical model 

 propagates the deepwater waves into the shallow coastal waters, taking into 

 account the specific ba thyme trie features, and correcting for refraction, 

 shoaling, frictional losses, island sheltering, and localized wind effects. 

 Results are checked against measurements made during the period for which the 

 hindcast is being made. The final product is a time history of nearshore 

 directional wave spectra at 3-hour intervals for the 20-year period at each 

 nearshore grid point (approx. 10 m depth) . This massive computational effort 

 consumed weeks of processor time on a supercomputer. 



More details on the WIS wave hindcast at Bolsa Chica and a summary of 

 results are provided in the comprehensive modeling report (Gravens, et al . in 

 preparation) . 



Comprehensive Shoreline Response Modeling . The comprehensive shoreline 

 response modeling task was similar to the preliminary shoreline modeling 

 described above. The comprehensive modeling utilized the same modeling 

 methodology as before, and much of the work performed in the preliminary task 

 (e.g., bathymetry grids, shoreline position data, and model boundary condi- 

 tions) did not have to be repeated for the comprehensive task. The key 

 difference was that wave estimates from the WIS hindcast were used as input to 

 the comprehensive modeling. These improved wave estimates provided more 

 confidence in the numerical model results, and allowed model calibration to be 



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