HYDROLOGIC CHANNEL-FLOW ROUTING FOR COMPOUND SECTIONS

An efficient channel-flow routing scheme for large drainage networks with compound sections and for continuous long-term simulation is often needed for sediment and water-quality investigations. A Muskingum-Cunge channel-flow routing scheme is adopted for this purpose. Main channel and overbank flow in compound cross sections are decoupled and routed separately to quantify the different flow characteristics in each channel portion. A variable time step is introduced to increase the efficiency of the numerical scheme. The adaptations of the channel-flow routing scheme are tested against hydraulic channel-flow routing using the DAMBRK model. Test conditions consist of several hypothetical flood hydrographs in long prismatic channels with significant overbank storage. For the tested cases, hydrograph peak and time to peak are, on the average, within 4% of the results from hydraulic routing. Simulated hydrograph shapes are consistent with expectations, and hydrograph distortions, resulting from overbank flood plains, are well reproduced. Furthermore, execution time of the numerical scheme is generally more than one order of magnitude faster than the benchmark hydraulic routing.