Texas Department of Transportation

Texas' Wetland Mitigation Banks

Bottomland hardwood forests are more than wetland "bottoms" created by creeks, rivers, and floodplains. They're communities of trees like elm, bald cypress, tupelo, and cottonwood, which contribute immeasurably to wetland functioning and biodiversity. They also provide food and shelter for migratory birds and other wildlife as one of the most endangered ecosystems in the nation.

Over the years, timbering, reservoir construction, and urban and rural development have diminished bottomland hardwoods. In the 18th century, Texas had approximately 16 million acres of bottomlands. Today, the state has 5.9 million acres of bottomland hardwoods and other forested riparian vegetation and 95,000 acres of swamps. Since pre-settlement days, there has been a 63 percent loss of the original bottomland hardwoods.

During the 1990s, the Texas Department of Transportation (TxDOT) partnered with the Texas Parks and Wildlife Department (TPWD) to purchase, restore, enhance, preserve, and manage more than 9,000 acres of this diminishing habitat. Locations for the bank sites throughout Texas were selected by TxDOT with input from a Mitigation Banking Review Team (the TPWD, U.S. Army Corps of Engineers, the U.S. Fish and Wildlife Service, the U.S. Environmental Protection Agency, and the Texas Commission on Environmental Quality).

No unsophisticated equipment, no ordinary sites. Infrared satellite imagery and GPS data were used to delineate each of the bank sites, chosen for their unique habitats, their ability to be restored and enhanced, their proximity to other resources, and their multi-purpose capabilities. Luckily, the landowners were willing to sell.

TxDOT's first bank--the 2,243-acre Anderson Tract--was established in Smith County. The tract is a highly diverse complex of bottomland hardwood wetlands and oxbow lakes now managed by TPWD. Adjacent to the Big Sandy Wildlife Management Area on the northern bank of the Sabine River, the large contiguous tract of land is even more beneficial for wildlife.

In Orange County, the Blue Elbow Swamp Mitigation Bank is a 3,343-acre cypress-tupelo swamp near the mouth of the Sabine River by the Gulf Coast. Chinese tallow, an invasive tree introduced to the United States by Ben Franklin, threatens to crowd out the swamp's cypress, tupelo, and other trees. TxDOT is spending $100,000 for research in tallow control measures to be carried out on the site.

Bald eagle habitat, bottomland hardwood wetlands and uplands, and 40 acres of created wetlands make up the Coastal Bottomlands Mitigation Bank (the largest of the three banks with approximately 3,552 acres) adjacent to the Brazoria River. An unusual feature of this bank is "the gilgai component"--micro-topographical relief that allows very small wetland pockets to co-exist scattered among ancient live oak trees that may be more than 500 years old. Another unusual feature of this bank is a willow swamp, which is rare in Texas.

All three bank sites offer more than ecological benefits. They've become popular outdoor classrooms for students and recreational havens for campers, hikers, birdwatchers, and other nature enthusiasts.

Time is on TxDOT's side. The three wetland mitigation banks have an anticipated 20 year credit life in which to meet the goals of a management plan and to speed the progress of transportation projects within the banks' geographic service area (Northeast Texas, Beaumont, and the Houston metropolitan area). To date, more than 90 transportation projects have been expedited by using bank credits. After 20 years, the unused credits will still be available to TxDOT and the wetland tracts will transfer from TxDOT to TPWD to own and manage in perpetuity.

For more information, contact Tom Bruechert, tom.bruechert@dot.gov