model of the Chesapeake Bay. The model used was a simplified model origi- 

 nally developed by Reid and Bodine (1968) for the Texas coast. The model 

 calculated the wind-induced setup of the water level throughout the Bay. 



The storm surge model used a time-stepping finite difference numerical 

 algorithm that solved appropriate differential equations representing a flow 

 system. The equations and momentum and continuity expressions contain 

 terms that simulate the following processes: 



- Coriolis forces 



- Surface wind stresses 



- Bottom stresses 



- Advection 



- Surface slope currents 



Land boundaries in the simple model were treated as vertical walls; however, 

 the model did not have the capability to simulate inland flooding. 



Based upon application of the simple storm surge model representation of 

 the Chesapeake Bay and Bay Ridge areas, the storm surge levels 

 corresponding to each design return interval for the project area are shown in 

 Table A2. 



Table A2 



Design Water Levels 



Event 



Surge Level 

 (ft. mlw) 



1 -year 



3.6 



10-year 



4.5 



25-year 



5.2 



50-year 



6.0 



Waves 



Wave conditions for the design of shore protection structures 

 at Bay Ridge were generated using an array of numerical models 

 and finite difference grid scales. 



Large scale, or "offshore," wave conditions in the Chesapeake 

 Bay were calculated using a time-stepping directional spectral 

 wave model. Directional spectral wave models are generally 

 more accurate than other methods of determining wave conditions 

 on the Chesapeake Bay primarily because the Bay is considered 

 both a narrow and shallow water fetch over which the waves are 

 generated. Simpler techniques for determining wave conditions 

 do not account for land boundaries on the sides of narrow fetches and do not 

 account for the predominance of shoal areas such as those in the Bay. 

 Significant errors in wave estimates during extreme events can result by 

 ignoring these physical constraints on wave generation and propagation. The 

 Chesapeake Bay was initially digitized into a 2.5-nautical mile finite difference 

 grid, over which winds corresponding to each design event were applied. 



The offshore wave conditions generated in the initial wave model 

 application were used as input to a finer scale simulation. The simulation was 

 performed using the same directional spectral wave model at a finite 

 difference grid scale of 500 ft including all important nearshore wave 

 transformation processes, including wave refraction, shoaling, wave-wave 

 interactions, bottom friction, etc. The nearshore wave conditions for each 



A4 



Appendix A Case Design Example of Detached Breakwater 



