Flood Improvement and LID Modeling Using XP‐SWMM
First developed in 1971, the EPA's Storm Water Management Model (SWMM) has been widely used in urban areas for planning, analysis, and design related to stormwater runoff, combined sewers, sanitary sewers, and other drainage systems. XP‐SWMM, published by XP Solutions Inc., uses the EPA SWMM model as the primary runoff hydrograph simulator for runoff quantity and quality. The major advantage of XP‐SWMM over other software packages is its ability to combine a 1D river hydraulic model with a 2D rainfall‐runoff model to generate floodplain maps. In addition, XP‐SWMM is approved by FEMA for the hydrologic and hydraulic applications detailed in this study.
There are three separate modules present in XP‐SWMM: runoff, sanitary, and hydraulic. The runoff module includes subcatchment areas for hydrologic modeling. The sanitary module allows for pollutant loading and water quality analyses, and the hydraulic module is capable of simulating the hydraulics of channels and storm sewers. Most of the work for Rice University’s flood improvement project was accomplished in XP‐SWMM’s hydraulic module, while the LID modeling was conducted using the runoff module.
Harris Gully Watershed
Rice University is located within the Harris Gully watershed, which covers a drainage area of approximately 5 square miles, consisting mostly of fully‐developed residential and light commercial land use. The area is also home to Hermann Park and the Texas Medical Center, the largest medical center in the world. A number of severe storms have impacted the Harris Gully watershed, the most notable of which being Tropical Storm Allison in 2001. TS Allison caused severe flooding problems throughout the entire watershed, resulting in roughly $5 billion in damages. Inundation was especially severe at the downstream portions of Harris Gully, where Rice University and the Texas Medical Center are located.
After TS Allison and as part of the Tropical Storm Allison Recovery Project (TSARP), a number of drainage improvement efforts were conducted to mitigate future flooding problems in the watershed.