



i 





FLOOD 



a 



EBB 













CHESAPEAKE BAY 



r- BREAKWATER (TYP.) 





y 



CZZD 



(=) <=> 



CZD 



□ □□ ci C3 C3 ^ 















V- PUMP STATION ^- EMBANKMENT 



191 



X 



Figure A 10. Shoreline coordinate system 



Data for the START file 



The initial model configuration is contained in START_INIT. Values for 

 the modeling parameters were based on available data from the site and best 

 engineering assumptions. Values selected and the rationale for their selection 

 are discussed in the following paragraphs. 



Line A.3. Breakwaters are 100 ft in length and the gaps between them are 

 100 ft. The exceptions are a 75-ft gap between Breakwaters No. 6 and No. 7, 

 and Breakwater No. 11, which has a length of 75 ft. 



Line A.5. Wave data were developed by hindcasting hourly wind speeds 

 obtained from a nearby anemometer. Accordingly, the initial time interval 

 selected is DT = 1 hr. Previous experience indicated that with an alongshore 

 spacing of DX = 12.5 ft., this time interval should result in a reasonable 

 stability parameter. 



Line A.12. For the initial simulation, the values of Kl and K2 were left at 

 the default values of 0.50 and 0.25, respectively. A preliminary run with 

 these values and no offshore breakwaters resulted in a net longshore transport 

 rate of -10,000 cu yd/yr, which compares favorably with the estimated 

 longshore transport rate in the area. 



Line B.l. For the initial simulation, the values of HCNGF, ZCNGF, and 

 ZCNGA were set to give no change. 



Line C.l. Sand placed as a part of project construction had a median 

 grain size of 0.5 mm. This value was selected for the initial simulation. 



A18 



Appendix A Case Design Example of Detached Breakwater 



