|The accurate simulation of flooding is crucial in the design of safe, cost-effective hydraulic structures. Hydraulic engineers are faced with several difficult decisions that will determine the accuracy of any modeling scenario. The foremost decision is the selection of the hydraulic model. Once the model has been selected the input parameters must be chosen, the model executed, and the results interpreted.
This study is a comparison of two flow models to determine their applicability to specific river reaches. The two models selected for comparison were Hydraulic Engineering Center’s River Analysis System and Finite Element Surface Water Modeling System. The respective one- and two-dimensional models were used in conjunction with calibration data for flood flow simulation.
Two river reaches with varying basin characteristics were modeled. The roughness values required to simulate the high-water profiles were less for the two-dimensional model than for the one-dimensional model. Comparison of the two reaches indicated that the roughness values for one- and two- dimensional flow are not considerably different for basins with very flat slopes. It was also determined, for two-dimensional flow, a reasonable range of values; the base kinematic eddy viscosity has little effect on the resulting water-surface profile.
The high- water profiles predicted by the one- and two-dimensional models were examined and the hydraulic properties within the reach were investigated. The results showed that assumptions of one-dimensional flow are valid for a standard reach and a skewed roadway crossing up to approximately thirty degrees. The flow distribution and correlating velocities were compared to measured values, for the second river reach. It was found that the flow distribution for both models matched the measured value within three percent. The velocity profiles created within the two-dimensional model were found to overall provide a closer match to the calibration data.