Assessment of Flood Risk Due to Storm Surge in Coastal Bayous Using Dynamic Hydraulic Modeling

The purpose of this study is to analyze the combined effects of storm surge and inland rainfall on the floodplain of a coastal bayou in the Houston area using dynamic hydraulic modeling. The hydrologic and hydraulic models that were utilized in the study were created by the Tropical Storm Allison Recovery Project (TSARP). The TSARP HEC-RAS model was run for both the steady and unsteady states. In steady mode, storm surge was introduced by changing the downstream boundary conditions to match that of the measured and predicted peak stage of the surge. HEC-RAS was then used to run a backwater calculation in order to provide a worst case floodplain. Upon completion of the steady state study, the model was then evaluated in the unsteady state. Running HEC-RAS in the unsteady state allowed both rainfall and storm surge to be introduced dynamically. This allowed for a more accurate representation of the flooding characteristics of this channel, but more work is needed to refine hydrographs.