extended to a number of years to obtain valid predictions. Stated different- 

 ly, the shoreline change model best calculates shoreline response in transi- 

 tion from one equilibrium state to another, which occur over months to years. 

 Spatial Extent of Simulation 



The spatial extent of a region to be simulated with a shoreline change 

 model can range from the single project scale of hundreds of meters to the 

 regional scale of tens of kilometers. The modeled longshore extent will 

 mainly depend on the physical dimensions of the project and boundary condi- 

 tions controlling the sand transport. Dimensions of the project are at a 

 local level, whereas placement of boundary conditions may or may not require 

 extension to a regional level. Evaluation of possible effects of the project 

 on neighboring beaches may also dictate extension of the spatial range of the 

 simulation. Shoreline change numerical models require minimal computer 

 resources and are usually capable of covering a regional scale for engineering 

 studies . 



As previously discussed, shoreline change models are designed to describe 

 long-term trends of the beach plan shape in the course of its approach to an 

 equilibrium form. This change is usually caused by a notable perturbation 

 (for example, construction of a groin or jetty). Shoreline change models are 

 not applicable to simulating a highly fluctuating beach system in which no 

 trend in shoreline position is evident, such as on a long natural beach. 

 Specifically, the shoreline change model GENESIS, in its present form (Version 

 2), is not applicable to calculating beach change in the following situations: 

 interior of inlets or areas dominated by tidal flow; storm- induced beach 

 erosion in which cross -shore sediment transport processes are dominant; scour 

 at structures; and sediment transport processes in the offshore. 

 Capabilities 



Table 1 gives a summary of major capabilities and limitations of Version 

 2.0 of the shoreline change simulation model GENESIS. 



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