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This report presents the mathematical formulation and verification of a numerical model that simulates wave transformation and longshore current over a bar and trough beach profile. The model is intended for application on projects involving dredged material berms and other situations where a bar and trough topography prevents use of simple analytic or numerical solutions that are restricted to a uniformly sloping beach. The model is called NMLONG, an acronym that stands for Numerical Model of the Longshore current. The model incorporates all known features of the wave and longshore current system that appear in research-type engineering models run on mainframe computer systems. These features include wave and wind driving, wave breaking and reformation over multiple bar and trough profiles, and lateral mixing. The model also allows choice of linear or quadratic bottom friction and regular or random wave heights as options. The main restriction of the model is longshore uniformity of the waves and beach topography.
This user's manual provides the necessary guidance, complete with multiple example applications which include model input and output, for using the N-line numerical model. Capabilities of the model include the simulation of a) single or multiple shore-perpendicular structures, b) single or multiple detached offshore breakwaters, and c) disposal of material or dredging of material in the coastal zone. Model parameters are discussed in order to guide the potential user to a successful application of the model. The N-line model is versatile, easy to use, and capable of producing dependable results when used for appropriate applications. The documentation in this manual covers only the breakwater subroutine. Since conceptual modifications were not made to the original model, the original documentation, presented in CERC's report MR 83-10, should be obtained by any potential user of the model. The N-line model is useful in showing qualitative trends for a complex case such as Lakeview Park, Lorain, Ohio. Some of the drawbacks of the program when modeling Lakeview Park, such as the inability reach an equilibrium shoreline, and the low sinuosity of the shoreline when influenced by breakwater segments, could possibly be successfully modeled by modifying the different input parameters, such as the ADEAN parameter and/or initial shoreline location and/or the model code. Perhaps then a quantitative verification if the model could be made. However, in this case, the model would have then been tailored to produce a previously known result.
A numerical model called STFATE for computing the short-term fate of dredged material disposed in open water has been developed. STFATE builds upon work of earlier researchers to provide a more realistic simulation of real disposal operations from split-hull barges and multi-bin hopper dredges. New developments allow for multiple-convecting clouds and stripping of solids fluid from those clouds to better represent water column effects. Other developments include the use of the total energy approach for computing the bottom surge and computations that make the model more applicable at dispersive disposal sites. STFATE has been applied to simulate disposal tests conducted at a 1:50 scale in a large laboratory facility at the U.S. Army Engineer Waterways Experiment Station. Comparison of computed and measured results on decent and bottom surge speeds, bottom deposition, and suspended sediment concentrations have been made. The results show that STFATE can be used to reliably predict the fate of material disposed at open water disposal sites. However, an uncertainty analysis is needed to place accuracy bounds on model results. (AN).