A NEW OCEAN-ENTRANCE SYSTEM AT BOLSA CHICA BAY, CALIFORNIA: 

 PRECONSTRUCTION ASSESSMENT OF POTENTIAL SHORELINE IMPACTS 



Mark B. Gravens 1 



ABSTRACT 



This paper describes the use of the shoreline change numerical 

 model GENESIS in the assessment of potential shoreline impacts 

 resulting from the construction of a structured inlet entrance 

 system at Bolsa Chica, California. The methodology of shoreline 

 change modeling, including the preliminary steps of data collec- 

 tion, analysis, and preparation for input to the shoreline change 

 model, is discussed, as well as interpretation of models results. 

 This paper illustrates the utility of shoreline change models in 

 the assessment of shore protection alternatives and the modifica- 

 tion of longshore sediment transport processes. 



INTRODUCTION 



The shoreline change study discussed herein was conducted by the U.S. 

 Army Engineer Waterways Experiment Station (WES) , Coastal Engineering Research 

 Center (CERC), for the California State Lands Commission (SLC). This study 

 was performed as one task of a multi- tasked engineering investigation which 

 examined the impacts that a proposed ocean entrance system at Bolsa Chica, 

 California, would have on the adjacent shorelines and tidal wetlands. An 

 overview of the suite of studies conducted at WES is presented in a companion 

 paper (Hughes 1989). 



The purpose of the shoreline modeling effort was to quantitatively 

 assess the potential long-term impacts of the proposed ocean entrance system 

 at Bolsa Chica on adjacent shorelines and to investigate the potential for 

 mitigation of any adverse effects induced by the entrance. Three major 

 components were involved in the shoreline modeling effort: (1) preliminary 

 shoreline response study, (2) comprehensive wave hindcast, and (3) comprehen- 

 sive shoreline response study. In the preliminary shoreline response study, 

 available shoreline and wave data were collected, analyzed, and input to the 

 shoreline change numerical model to predict the response of adjacent 



(1) Research Hydraulic Engineer, Coastal Engineering Research Center, U.S. 

 Army Engineer Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, 

 Mississippi 39180-6199. 



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