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<br />2,11 <br /> <br />3. The assumptions inherent in the turbul ent and 1 ami nar flow equat ions <br />(Equations 2.17, 2.20, and 2.21) are valid for this analysis. <br /> <br />4. Granular flow dispersive stress is negligible for the viscous type of flows <br />being considered. For a further discussion of the nature of dispersive <br />stress, see O'Brien and Julien (1988). Generally, if the fluid matrix is <br />substantially more viscous than water, the role of dispersive stress is <br />transferring momentum from the core of the flow to the boundary will be <br />negligible. <br /> <br />2.5 Model Structure <br />The MUDFLOW model has been designed in a modular form to allow convenient <br />editing and revision of code. All the subroutines have been separated from the ""'. <br />main program and exist as individual programs that must be compiled and linked, <br />The main program handles all the reading of the input data and the writing of <br />the results to the output fil e. It also performs most of the flood p 1 a in <br />computations. <br /> <br />2.5.1 ICHECK <br />ICHECK is a subroutine that conducts a data check of the grid system and <br />the width reduction factors (WRF). It ensures that the common boundary of <br />contiguous grid elements is identified correctly in the data file. Further, it <br />ensures that the WRF's are identical for common boundaries. <br /> <br />2.5.2 UPMUD <br />This subroutine calculates the watershed overland flow discharge into the <br />watershed channels and adds sediment to it. A sediment concentration matrix must <br />be specified based on the channel grid element and a time interval. The water <br />fl owi ng over 'land off the watershed and into the channel is bul ked accordi ng to <br />the equation <br /> <br />BF = <br /> <br />L <br />1. ' Cv <br /> <br />(2.24) <br /> <br />using the specified sediment concentration by volume for that channel grid and <br />time interval presented in a sediment concentration matrix in the data file. <br />An example of the sediment concentration matrix is presented in Table 2.L The <br />