ideal beach profile change model discussed in this report include the 

 following: 



a . Input data, initial conditions, and boundary conditions. 



(1) Deepwater wave height and wave period (entering in part 

 as the wave steepness) should be among the basic input 

 variables to drive the model or to establish an offshore 

 wave boundary condition. 



(2) The properties of the beach material (fall velocity or 

 representative grain size and composition) must be 

 included. It may be necessary to allow for natural 

 sorting along the profile in some cases. 



(3) The profile shape is required as an initial condition. 



(4) An offshore boundary condition, specifying the maximum 

 depth to which sand is transported across shore in 

 significant amounts, is required. 



(5) An onshore boundary condition is required. This boundary 

 condition must allow for berm and dune erosion, as well 

 as berm buildup. 



b . Calculation procedures. 



(1) Calculation procedures for the local incident waves, 

 infragravity waves, and wave-induced currents (orbital 

 velocities, mass transport, or undertow) in the region 

 between the offshore and onshore boundary points are 

 required. This calculation includes breaking wave 

 criterion and broken (surf zone) wave model. 



(2) The model must allow for calculation or specification of 

 the mean water level, including the effects of astronomi- 

 cal tide, meteorological surge, wave setup, and runup. 



(3) Calculation procedures for cross-shore sediment transport 

 rates are necessary. These procedures would include 

 threshold effects and encompass spatially and temporally 

 varying sediment transport regimes over ripples, at the 

 breakpoint, in the sheet flow area, in the swash zone, 

 and at the air-water interface on shore. 



(4) A calculation procedure to compute profile change that 

 allows representation of all major morphological 

 features, and which conserves sand volume, is necessary. 



c_. Model properties . 



(1) Formation, movement, and erasure of bars must be 

 represented . 



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