Cypress Creek Overflow Investigation

The purpose of this study is to review the FEMA Effective Physical Map Revision (PMR) published in 2013 and the recognized XPSWMM 2D Overflow model from Harris County Flood Control District (HCFCD) to identify the components of the models that likely contribute to conflicting 100-year Base Flood Elevations in the vicinity of Katy-Hockley Road.

In addition to reviewing input datasets, hydrologic parameters and model assumptions for the 1D and 2D models, a series of analyses were performed to assess the models sensitivity to changes to the aforementioned parameters and their corresponding effects on water levels. Recommendations to help resolve/reduce differences in the Base Flood Elevations computed with the HEC-RAS and XPSWMM model were made based on the findings from this study.

This study also included a detailed review of: USGS streamflow rating development, watershed diversion methods, 1D and 2D modeling procedures.