Harris County enlisted EHRA to perform a planning-level engineering investigation for the Foxwood Subdivision, located in northern Harris County. The objectives of the investigation were to determine the causes of flood losses reported within the residential community, to reduce the risk of structural flooding and improve resiliency in the subdivision.
Project Manager Jennifer Hundl, PE, CFM, LEED AP applied the Rational Method when analyzing the existing storm sewer system for the two-year rainfall design. In addition, our engineers analyzed extreme event flow paths using the Hydrologic Engineering Center’s River Analysis System two-dimensional (HEC-RAS 2D) software. This system’s rain-on-grid exercise utilized available light detection and ranging (LiDAR) information and rainfall for the existing one percent 24-hour event. Our investigation also involved taking an inventory of existing utilities and ingress/egress routes to the neighborhood.
After critical data was compiled, EHRA recommended changes intended to increase inlet capacity in the areas of repetitive flood loss. The results of the HEC-RAS 2D analysis revealed that Foxwood did not have adequate extreme event overflow infrastructure. To resolve this deficit, we recommended the acquisition of a particular property that would allow construction of the necessary extreme event overflow structure and reduce the risk of structural flooding.
EHRA participated in a community engagement meeting to discuss investigation results and subsequent recommendations. Our team fielded comments and addressed community member questions. EHRA further initiated and engaged in discussions amongst local MUD and Harris County Precinct 4 staff members to encourage a construction partnership between the entities.
EHRA performed another subsequent drainage analysis in the area. This analysis was a non-detailed, two-dimensional study evaluating how rainfall interacts with the local topography. The purpose of this additional study was to identify overflow limits versus surveyed finished floor elevations. Previous recommendations were then appraised using updated Atlas 14 rainfall totals. The project was completed in 2021.