maintenance of the entrance by scouring water flows. The entrance instead is 

 designed to prevent sediment from entering the inlet channel, thus making the 

 entrance system a barrier to the major portion of longshore -moving sediment. 

 Material that does enter the channel will be deposited, and periodic dredging 

 may be required to maintain the entrance channel at its design dimensions. 



IMPACTS TO SURFING 



A qualitative assessment of potential impacts that an ocean entrance 

 system at Bolsa Chica may have on local surfing activities was performed under 

 contract. Existing surfing conditions were assessed by conducting interviews 

 with local surfers and by examining wave results obtained from a Littoral 

 Environment Observation Program conducted at Bolsa Chica. Based on knowledge 

 of surfing and coastal processes, a method was developed for quantifying the 

 incident wave climate in terms of desirable surfing qualities (Dally, in 

 publication) . Application of this method in assessing the proposed project 

 impacts led to the following considerations: 



a. The primary impact to surfing is the potential loss of 

 approximately 3200 ft of surf break due to the shadow zone of the 

 detached breakwater. This zone would lengthen when the wave 

 angle approach is very oblique. The impact zone will decrease 

 with decrease in breakwater length. 



b. The loss of surf break is incurred only at times when surfable 

 waves would otherwise be present, which was estimated to be less 

 than 50% of the time . 



c. There is a possibility that wave reflection from the jetties may 

 interact with non- surfable incident waves to form ridable waves. 



Additional surfing assessment using the physical model of Bolsa Chica was 

 performed, but results were not available at the writing of this paper. A 

 complete description of the surfing analysis is included in the comprehensive 

 modeling report (Gravens, et al . in preparation). 



SUMMARY 



Modern coastal engineering analysis tools have been used to assess and 

 quantify, where possible, the impacts that two proposed ocean entrance altern- 

 atives would have if either were to be constructed at Bolsa Chica, California. 



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