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Chapter 18 Sediment Impact Analysis Methods (SIAM) Figure 18-5. Grain class specific grain class function feature. Fall Velocity Method The Fall Velocity Method drop down box allows the user to select the method of fall velocity computation. If Default is selected, the method associated with the respective transport function in the literature is used. Otherwise, the selected fall velocity method will be used. The three fall velocity methods available are: Toffaleti, Van Rijn, and Rubey. Wash Load Max Class, Diameter Wash load is the material in the system, but not present in appreciable quantities in the bed. SIAM does not apply the standard transport equations to compute a mass balance for wash load materials. Instead, it automatically passes them through the sediment reach. If the wash load threshold drops from one sediment reach to the next adjacent downstream reach, the material in the grain class(es) that is no longer wash load is added to the bedload and subjected to the standard mass balance approach. 18-7
