Upper Trinity River-Dallas: Implementing TMDLs through Low Impact Development
Low-impact development (LID) is a comprehensive approach to site planning, design, and pollution prevention strategies that, when combined, create a more economically sustainable and ecologically functional landscape. LID works with nature to manage stormwater as close to its source as possible.
LID treats stormwater as a resource, rather than a waste product, and integrates hydrologic and water quality functions into all aspects of the urban landscape and infrastructure. The result is functional and appealing site drainage that restores the ecological integrity of receiving waters, promotes the natural movement of water within an ecosystem or watershed, and reduces construction, maintenance, and inspection costs.
Examples of LID management approaches and technologies include rain gardens, porous pavements, green roofs, and rainwater harvesting for later use.
While recent studies have evaluated the effectiveness of LID practices in various regions of the United States, there is still a great need to evaluate their performance. There is also very little data on the possible effects of adopting LID at a watershed level.
The goal of this project was to improve the quality of stormwater from a site typical of commercial development in the Upper Trinity and White Rock Lake watersheds. The focus, as part of the implementation of the Dallas County TMDLs for legacy pollutants, was on removal of chlordane from storm water runoff. An additional goal was reducing the total and peak flows of stormwater and reducing nutrient and sediment loads from storm water entering area streams.
The project designed and built several LID features at the Texas A&M AgriLife Research and Extension Center in Dallas and monitored the volume and quality of storm water entering and leaving these features. Continuing demonstration of these practices after the project ended is showing how LID can be integrated in new developments or retrofitted to existing ones.
Five LID practices were examined in this project: permeable pavements, bio-retention areas, rainwater harvesting, green roofs, and extended detention ponds. Multiple versions of these practices are being compared, including alternate irrigation strategies for the rain water harvesting practices.
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