Profile erosion models 



30. Principal uses of profile erosion models are prediction of beach 

 change on the upper beach profile produced by storms (Kriebel 1982; Kriebel 

 and Dean 1985; Larson 1988; Larson, Kraus , and Sunamura 1988; Larson and Kraus 

 1989b; Larson, Kraus, and Byrnes, in preparation) and initial adjustment of 

 beach fills to wave action (Kraus and Larson 1988, Larson and Kraus 1989a). 

 This type of model is simplified by omitting longshore transport processes; 

 i.e., constancy in longshore processes is assumed so that only one profile at 

 a time along the coast is treated. In principle, the profile change and 

 shoreline change models could be used in combination to predict both long- and 

 short-term changes in shoreline position. 



Shoreline change model 



31. The shoreline change numerical model, the subject of this report, 

 is a generalization of analytical shoreline change models. It enables 

 calculation of the evolution of the shoreline under a wide range of beach, 

 coastal structure, wave, and initial and boundary conditions, which may vary 

 in space and time, as appropriate. Despite the assumption of constancy of 

 beach profile shape alongshore, the shoreline change numerical model has 

 proved to be robust in predictions and provides a general solution of the 

 equation governing shoreline change (described in Part V) . Because the 

 profile shape is assumed to remain constant, in principle, landward and 

 seaward movement of any contour could be used in the modeling to represent 

 beach position change. Thus, this type of model is sometimes referred to as a 

 "one-contour line" model or, simply, "one-line" model. Since the mean 

 shoreline position (zero-depth contour) or similar datum is conveniently 

 measured, the representative contour line is taken to be the shoreline. 

 Longshore sand transport together with lateral boundary conditions on each of 

 the two ends of the model grid are the dominant causes of beach change in the 

 shoreline change model. Sources of sediment, such as beach fills and river 

 discharges, as well as sediment sinks, such as inlets and sand mining, can be 

 accounted for in a phenomenological manner. From this perspective, the 

 shoreline change numerical model provides an automated means to perform a 

 time -dependent sediment budget analysis. 



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