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<br />The inflowing sediment load is related to water discharge by a rating <br />table at the upstream end of the model. If the gradation of material <br />in the bed is known, and it must be if realistic" depths of scour and <br />the bed are required, this gradation is specified for each cross <br />section. (However, if only deposition is expected, the gradation of <br />material in the bed can be calculated by the program based upon the <br />inflowing water-sediment mixture.) <br /> <br />Sediment mixtures are classified by grain size using the American <br />Geophysical Union scale. The program accommodates clay (up to .004 <br />mm), four classes of silt (.004 - .0625 mm), five classes of sand <br />(very fine sand @ .0625 mm to very coarse sand @ 2 mm), and five <br />classes of gravel (very fine gravel A2 mm to very coarse gravel A <br />64 mm). <br /> <br />Transport capacity is calculated at each cross section by using <br />hydraulic data obtained during the calculation of water surface <br />profiles (e.g., width, depth, energy slope and velocity of flow) <br />and the gradation of bed material for that cross section. <br /> <br />Three options are available for calculating transport of bed material: <br />Toffaleti's application of Einstein's Bed Load Function, reference 5; <br />Laursen's relationship as modified by ~adden for large rivers, reference <br />8; or a special relationship can be developed for the particular study <br />and specified as transport capacity per unit of width versus the water <br />depth-energy slope product. Deposition of cohesive material is based <br />on bed shear stress. <br /> <br />6. THEORETICAL BASIS FOR THE PROGRAM <br /> <br />The theoretical basis for the program is discussed in exhibit 3. <br /> <br />7. PROGRAM ORGANIZATION AND SIZE <br /> <br />In its present configuration the entire program resides in 40,000 <br />words (Univac 1108) of memory without chaining. The various modules <br />function together as subprograms where data is transferred in "Labeled <br />Common" or in "Call Linkage." However, the location for tape commands <br />is identified by Comment Cards in the source program to assist if <br />chaining is required. The functional flow chart is shown in figure 1. <br /> <br />5 <br />