Application for Channel and Flood Plain Interface Model

Application 7: Channel-Flood Plain Model

Figure 37 depicts a discretization of a two-dimensional hypothetical watershed with three major channels crossing through the flood plain.

Figure 38 depicts the inflow and outflow boundary conditions for the hypothetical watershed model. Input data and partial output results of this application are included in Attachment D. Figures 39 through 44 illustrates the evolutions of the flood plain.

The shaded areas indicate which grid element are flooded. From figure 39, it is seen that the outflow rates at nodes 31, 71 and 121 are less than the corresponding inflow rates which results in a flooding situation adjacent to the outflow grid elements. The junction of channel B and B' is also flooded. At the end of the peak inflow rate (figure 41), about 1/3 of the flood plain is flooded. Figure 44 indicates a flooding situation along bottom of the basin after 10 hours of simulation. Figure 45 shows the maximum depth of water at 4 downstream cross-sections. It is needed to point out that the maximum water surface for each grid element are not necessarily incurred at the same time. Finally, figures 46 and 47 depict the outflow hydrographs for both the channel system and the flood plain system.

Until now, no existing numerical model can successfully simulate or predict the evolution of the channel-flood plain interface problem. The proposed DHM model uses a simple diffusion approach and interface scheme to simulate the channel-flood plain interface development.

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