Comparison of HEC-RAS and InfoWorks RS: A Case Study in Grand Prairie, Texas

The Hydrologic Engineering Center's River Analysis System (HEC-RAS) is a one-dimensional computer model intended to perform hydraulic calculations for a network of open channels. This model is widely available, free of cost and is the most commonly used hydraulic model in the United States. Most HEC-RAS models are steady state. Unsteady flow analysis in HEC-RAS differs in many ways from the traditional steady state analysis. The largest difference involves the ability to input a full hydrograph to analyze the response of the river system to flows (and tailwater conditions) that vary with time. This is a case study on Lower Mountain Creek in Grand Prairie, Texas. The study area is between Mountain Creek Lake and the confluence with the West Fork Trinity River. This area offers many challenges to a traditional HEC-RAS analysis, including relatively flat channel slope, a wide floodplain with split flows through multiple bridge openings, and considerable shallow overbank flooding. A comparison of the results using Steady HEC-RAS, Unsteady HEC-RAS and InfoWorks RS (IWRS) will be presented. The comparison will include not only differences in computational results, but differences in model structure, input requirements, and methodology.