PART VI: STRUCTURE OF GENESIS 



204. This chapter describes the general structure and operation of the 

 user interface of GENESIS and the preparations that must be made prior to 

 running the modeling system. Discussion is focused on the input and output 

 files comprising the interface. This and the succeeding two chapters provide 

 practical information needed to run GENESIS. 



205. The predictive reliability of GENESIS depends on the quality of 

 the input data. A major portion of the shoreline change simulation effort 

 involves gathering, cleaning, interpreting, formatting, and entering data into 

 input files. The various types of data used by GENESIS are discussed in 



Part V. In a scoping application, data preparation and model setup typically 

 take 1 to 2 months, depending on the scale of the project; the time for model 

 preparation and setup for design studies is typically 2 to 6 months. 



Preparation to Run GENESIS 



Coordinate system and grid 



206. As discussed in Part V, a coordinate system and grid are laid out 

 on a nautical chart or aerial photographs covering the region of the project, 

 and measured shoreline positions, locations and configurations of structures 

 and beach fills, and other topographic and geometric information are expressed 

 in the coordinate system as a function of grid cell number alongshore and 

 distance offshore. Alongshore location is specified by grid cell number 

 rather than distance in order to allow the precise control of positioning. 



The grid is discretized alongshore (along the x-axis), whereas shoreline 

 positions and other quantities specified along the y-axis are continuous. 

 Length units can be selected as either meters or feet, and all input and 

 output will use those units. 



207. A schematic example of the coordinate system and a grid is shown 

 in Figure 19. The vertical scale is exaggerated since the longshore extent 

 covered is typically thousands of meters or feet, whereas shoreline change is 

 typically tens or hundreds of the corresponding units. In shoreline applica- 

 tions, such figures are drawn with the observer positioned on land and the 



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