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<br />tit <br /> <br />the node spacing increases the number of nodes and decreases the length of time step <br />used in the model. Both factors increase the model's run time. <br /> <br />Flow in the model is generated by simulating rainfall on each node in the study area or by <br />inputting a runoff hydrograph at select nodes. Rainfall and inflow hydrographs cannot be <br />used simultaneously. The model also accounts for the initial rainfall abstractions and <br />infiltration. Infiltration is estimated for each node using the Green-Ampt equation. The <br />amount and direction of overland flow is calculated in eight directions - directly forward, <br />directly backward, to each side, and in the four diagonal directions. <br /> <br />Mudflows are modeled using inflow hydrographs. The input data contains the hydrograph <br />data, flow versus time, and the concentration of sediment conveyed by the flow, <br />concentration by volume versus time. FLO-2D routes the hyperconcentrated flows, tracking <br />the sediment volumes through the system. Changing sediment concentration, dilution <br />effects, and the remobilization of deposits are simulated at each node. Mudflow cessation <br />and deposition can be predicted by the model. Sediment concentration governs the <br />e movement of the fluid matrix. Quadratic rheological equations are used to predict viscous <br />and yield stresses as a function of sediment concentration. <br /> <br />Results generated by the FLO-2D model include outflow hydrographs at designated <br />nodes, maximum flow depths and velocities, and a summary of the total inflow, outflow, <br />storage, and losses within the study area. <br /> <br />FLO-2D Methodoloav <br /> <br />The model was first run for clear water only. Rainfall was applied over the 'entire study <br />area. Nodes were selected up-gradient (south) of the City, and the flow hydrograph at <br />each of these nodes was determined. <br /> <br />These outflow nodes and hydrographs were then converted to inflow nodes and <br />hydrographs. After examination of the hydrographs, sediment concentrations were <br />assigned for each time period and for each outflow node. The peak sediment concentration <br /> <br />e <br />