Bathymetry and profiles 



69. If a wave refraction model is used, hydrographic charts are needed 

 to digitize the bathymetry onto the numerical grid. For users with sufficient 

 computer hardware and related capabilities, bathymetric data for US coasts may 

 be obtained on magnetic media from the National Oceanic and Atmospheric 

 Administration (NOAA) and then interpolated to the grid. The nearshore 

 information from bathymetric charts can be compared with available beach 

 profile surveys. Profile surveys often extend to a nominal depth of 10 m 



(30 ft), providing information to supplement the charts. If calibration and 

 verification simulation intervals are in the far past (for example, in the 

 19th century), bathymetric data from that period should be used, not the 

 present bathymetry. This is especially pertinent if an inlet is included in 

 the wave modeling grid, since ebb shoals can greatly change. 



70. Profile data are used to estimate three quantities required to 

 operate GENESIS: the average height of the berm, the depth of closure 

 (seaward limit of significant sediment movement), and the average profile 

 slope . 



71. Bathymetric and profile data are also used to establish a general 

 sediment budget, to locate scour at structures, to infer sediment paths and 

 flow channels, to identify local areas of deposition and erosion, and to 

 qualitatively estimate and distinguish cross -shore transport and longshore 

 transport effects at structures in some situations. 



Structures and other 

 engineering activities 



72. Structures and other engineering activities, such as placement of 

 beach fill, must be correctly located on the grid both in space and time. 

 Procedures for accomplishing this are described in Parts VI and VII. Also, 

 GENESIS allows representation of changes in structures through time as, for 

 example, extension of a breakwater, construction of a groin field during the 

 simulation interval, or multiple placements of beach fill. Therefore, in data 

 collection and project planning, the locations, configurations, and times (and 

 volumes in the case of beach fills, dredging, and sand mining) must be 

 assembled. 



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