This project will examine flood risk reduction options for the area near Highlands Reservoir, including HCFCD tributaries O119-00-00, O200-00-00 and other nearby tributaries. This advanced feasibility study builds on the previous work done for the Cedar Bayou Flood Risk Reduction Study completed in 2018, which evaluated the potential flood reduction improvements to the Highland Mobile Estates, a neighborhood with repeated flooding history evident by multiple flood claims. Harris County Flood Control District conducted the study to investigate the potential of using a portion of the Highlands Reservoir property to provide additional storage volume or potential conveyance capacity. The study's goal was to identify possible drainage improvements that could lower the surface elevation within the Flood Control District channels south of the Highland Mobile Estates neighborhood. The Flood Control District worked with the San Jacinto River Authority (SJRA) who owns and maintains the Highlands Reservoir. The Harris County Engineering Department engaged a consultant to complete a neighborhood drainage study that included a more detailed analysis of potential drainage improvements within the Highland Mobile Estates neighborhood, concurrently with the Flood Control District’s advanced feasibility study.
This project is one of several under 2018 HCFCD Bond Project F-39, which concerns Investigations of General Drainage Improvements on Spring Gully.
Feasibility Study Results
As part of the advanced feasibility study, data was collected revealing that the existing pipelines were found below the west fork of the watershed Goose Creek (O119-00-00) and Spring Gully (O200-00-00) channels south of Barbers Hill Road and running north-south along the western side of the Highlands Reservoir into Buff Gully in the San Jacinto River Watershed. The recommended alternative proposed for channel improvements is only to widen and not deepen Goose Creek and Spring Gully.
Next, an existing conditions analysis of Goose Creek, Spring Gully and Buff Gully watersheds surrounding the Highland Reservoir was conducted to verify general drainage patterns, establish baseline water surface elevation, and better understand the underlying causes of exiting flooding. Based on existing model results and site visit observations, flooding within the Highland Mobile Estates neighborhood can be attributed to a lack of adequate local drainage infrastructure and high backwater elevations in the Flood Control District channels south of Barbers Hill Road.
Based on the existing conditions analysis results, the Flood Control District and San Jacinto River Authority selected five alternatives that focused on reducing the water surface elevation. The different strategies included:
· Widening the existing channel to provide additional storage.
· Constructing a detention pond within the reservoir.
· Making improvements such as benched widening, new detention pond, and structure replacement along G103-04-00.
· Diverting flow to the G103-04-00 to gain deeper outfall depths via box culvert.
· Constructing a new storm sewer to convey runoff from Highland Mobile Estates neighborhood directly into G103-04-00.