Environmental Enhancement Design and Special Project Support

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Environmental Enhancement Design and Special Project Support

Stormwater runoff enters our waterways, bringing floatable debris and suspended or dissolved pollutants. Stormwater treatment wetlands intercept runoff and help clean stormwater by settling, filtering, and transforming pollutants into less harmful forms. For example, excess nutrients in the water that feed bacteria growth, promote algal growth, and harm aquatic resources are transformed by wetland plants into harmless gases or plant tissue.

The Flood Control District has taken every opportunity to design environmental enhancements into its flood damage reduction projects. Environmental Enhancement is a general term referring to manmade features that mimic natural systems. These include permanent pools of water, stormwater treatment wetlands, riparian corridors, reforestation zones, and coastal prairies.

Open water areas within detention basins promote the breakdown of pollutants, such as pathogenic bacteria, through exposure to sunlight. These dynamic processes occur within any detention basin that includes stormwater treatment wetlands. In addition to improvements to water quality, stormwater treatment wetlands provide native animal habitat and aesthetic value. Additional benefits associated with riparian corridors, reforestation zones, and coastal prairies are discussed in further detail in Site Stabilization and Revegetation.

The Flood Control District has developed the following tools to assist design engineers and other professionals with incorporation of water quality enhancements into flood control projects, where practicable.

Design Guidelines for HCFCD Wet Bottom Detention Basins with Water Quality Features

Harris County Low Impact Development & Green Infrastructure Design Criteria for Storm Water Management

An example conceptual layout of a Flood Control District detention basin, showing directional water flow through constructed stormwater quality treatment wetlands

Conceptual layout of stormwater quality treatment wetlands and reforestation areas at Arthur Storey Park Detention Basin. The basin was engineered and designed for stormwater to pass over and through strategically planted vegetation for water quality enhancement purposes

Cypress Creek Overflow Management Plan Project Support

The Stormwater Quality Department provides support for the environmental tasks associated with the Cypress Creek Overflow Management Plan a planning effort to reduce flood risks within upper Cypress Creek and the drainage areas upstream of Addicks and Barker reservoirs. By reviewing historic and current land-use and ecological data, critical conservation areas (CCAs) were identified within the study area. These CCAs allowed planners and engineers to consider best possible land uses as the project was being designed, such as high-priority conservation sites, active or passive recreation areas, and wetland mitigation banking opportunities.

Additionally, the ecosystem benefits of coastal prairies will be quantified through monitoring and comparison of rainfall and runoff data between differing land types. The deep roots of prairie vegetation and the uncultivated soils in which they grow are thought to act like a sponge and absorb rainfall and runoff, providing the basis that the coastal prairie ecosystem could be used as another tool to support flood control efforts. While data collection and analysis are still in its infancy stages, growing evidence supports the hypothesis that the coastal prairie ecosystem provides a flood control benefit. Data will be collected through 2018, at which time a more robust conclusion and quantification of this ecosystem benefit can be offered.