Baywood : Riverbend : Hunting Bayou : Varners Creek
Baywood Detention Analysis
Baywood Golf Course planned to redevelop approximately 40 acres to multi-family residential with 3 acres of commercial. The project area included a detention pond site for detention storage to mitigate increases in the 10-year and 100-year peak runoff associated with the 43 acre redevelopment and a conveyance channel will run adjacent to the redevelopment which will outfall into Armand Bayou (HCFCD Unit No. B100-00-00). Grounds Anderson analyzed the projected increase runoff as a result of development of the project, and the detention necessary to mitigate the increase using methodology defined in the Harris County Flood Control District’s (HCFCD) “Criteria Manual for the Design of Flood Control and Drainage Facilities.”
River Bend Letter of Map Revision and Conditional Letter of Map Revision
Grounds Anderson prepared a LOMR in support of revising the Clear Creek (A100-00-00) Special Flood Hazard Areas Zone AE and floodway at the River Bend location by analyzing the floodway using HEC-RAS models and remapping the Zone AE with updated topography. A Conditional Letter of Map Revision based on fill (CLOMR-F) will be prepared and submitted at a later date to remove River Bend from the Clear Creek 100-year floodplain.
Hunting Bayou Pipeline Crossing
Grounds Anderson analyzed the addition of a Magellan Pipeline structure at the East Houston Station and Tank Farm across a Harris County Flood Control District Channel (HCFCD) Hunting Bayou (H100-00-00). A hydraulic analysis was performed to analyze the effects of the addition of this pipeline structure across Hunting Bayou using HEC-RAS. Mitigation areas were designed to counteract the impacts.
Varners Creek Letter of Map Revision – Brazos River Watershed
Grounds Anderson prepared a Letter of Map Revision for Columbia Lakes Community. The Effective Flood Insurance Study was updated with more detailed hydrology and hydraulics to determine 100-year water surface elevations along Varner Creek. The Effective Varner Creek HEC-2 model was recreated and updated in HEC-RAS with additional cross sections from field survey data and updated discharges from a technically superior hydrologic analysis. Hydrology was developed as part of this analysis that incorporated not only local runoff from basins adjacent to the channel but also from an overflow from the Brazos River to Varner’s Creek. As a result, a detailed floodplain and floodway analysis using HEC-RAS was performed to model the current existing condition of Varner Creek. The revised Base Flood Elevations were mapped against an inundation grid to develop an updated Zone AE along Varner Creek. The inundation was derived from a difference in surfaces between a base topography of the USGS DEM (West Columbia and East Columbia panels) and a surface created from the Base Flood Elevations along the HEC-RAS cross sections. The difference grid was spatially calculated in ArcView (Version 9.2) with the 3D Analyst Extension.