Mitigation and Conservation
The Greens Bayou Wetlands Mitigation Bank is a permanently protected, 961-acre expanse of ponds, marshes and forest, located near Greens and Garners bayous in northeast Harris County. Combined with bordering Harris County Flood Control District properties, it is part of a larger tract totaling 1,450 acres.
The Flood Control District established Greens WetBank in 1995 for two reasons:
- To provide mitigation opportunities to compensate for unavoidable negative consequences on wetlands elsewhere in Harris County.
- To protect and sustain a high-quality wetlands ecosystem.
Greens WetBank is developed as three separate subdivisions: A, B and the newest subdivision, C. Since establishing the Greens WetBank, the Flood Control District has successfully developed about 250 acres of the property in two subdivisions. This work has resulted in the creation of approximately 156 wetland credits, many of which have already been sold or reserved for use by local governments and private entities ranging from churches to commercial builders.
In 2014, a new Mitigation Banking Instrument (MBI) significantly changed the bank's service area for all subdivisions, while permitting additional mitigation credits in the newest Subdivision C. The new MBI also incorporates a new credit calculation.
This 50-acre forested subdivision consists of wetland habitat created and enhanced through a developed network of berms, depressions and hydrology-control structures. Terrain contouring and an intricate system of surface swales, completed in 1997, also helps disperse water throughout the subdivision. Varying water depths in open ponds helps filter out sediment and toxicans, and attract waterfowl and other wildlife.
Construction on this 220-acre subdivision of primarily former grazing land was complete in 1999. Along with its primary mitigation function, Subdivision B is designed to collect, manage and naturally treat stormwater runoff from the drainage area around Beltway 8. Run-off is routed into a polishing marsh, which naturally filters out impurities from auto traffic. The naturally enhanced stormwater then provides a hydrology source for the created wetland habitats in the subdivision. The site includes open ponds and marshes, bordered with wetland vegetation, that attract waterfowl and other aquatic wildlife.
This subdivision includes a mixture of pine and hardwood forest, interspersed with open grassy prairies and wetlands found in old bayou meanders and low areas. The Flood Control District will use low-impact, low-maintenance construction techniques to create and enhance additional wetland acres. The new Mitigation Work Plan (part of the MBI) calls for simple and natural techniques - such as strategically located earthen berms and low-water crossings - to retain and slowly disperse rainwater throughout the site. Large amounts of clearing, excavation and filling will be avoided. Planting native herbaceous and scrub-shrub wetland vegetation, and removing non-native invasive species, will re-establish and create herbaceous wetland areas. When work is complete, the property will provide a valuable resource for mitigation credits and preserved habitat. It is one of the few remaining undeveloped parcels in the northeast Harris County area.