US Army Corps of Engineers Fort Worth District tree mitigation supports Dallas levee improvement project

U.S. Army Corps of Engineers, Fort Worth District
Published July 10, 2012

DALLAS – A tree mitigation survey completed in July 2012 is a first step in executing an important component of the Fort Worth District’s Dallas Floodway Extension Project, which supports the city of Dallas’ flood risk reduction efforts. Life safety is paramount in the U.S. Army Corps of Engineers Levee Safety Program. Levee safety is a shared responsibility for the Corps, Dallas and its citizens.

A chain of wetlands lowers flood risk for Dallas by rapidly conveying floodwaters downstream through the Dallas Floodway System. The first set of wetlands, the Lower Chain of Wetlands, has already been built between the Interstate 45 and Loop 12 bridges over the Trinity River. Construction of a second interlocking wetlands group, the Upper Chain of Wetlands, is planned. All of these wetlands are necessary to permit the future construction of the Lamar and Cadillac Heights levees to protect these Dallas neighborhoods. A tree mitigation program in the adjacent Great Trinity Forest is required as part of the Corps’ environmental stewardship mission to compensate for the loss of woody plants in the Floodway as these chains of wetlands are built.

The tree mitigation survey was conducted by staff at the Corps’ Engineer Research and Development Center’s Lewisville Aquatic Ecosystem Research Facility in Texas. A crew led by University of North Texas graduate student Aaron Schad surveyed 20-foot-square sections of the mitigation area to better understand the soils, slopes and existing plant cover. This is required to aid the designing of the mitigation program by locating ideal sites for plantings.

The ERDC-Fort Worth District team’s test plots will be planted in fall 2012, followed by general plantings the following two years. The planting program will use adaptive management – the same process used in establishing desirable herbaceous vegetation in the wetlands. Sequential plantings will provide important guidance for future plantings as the project progresses, particularly in learning how best to establish new trees using little or no watering. The woody plant seedlings are being grown at ERDC’s Lewisville facility.

The mitigation program will improve the habitat quality of the Great Trinity Forest on lands owned by the city of Dallas. Much of this bottomland suffers a lack of woody plant diversity. Plantings will introduce a rich mixture of acorn-, nut- and fruit-bearing trees. Plantings of hardwoods and beneficial shrubs will add diversity to the area, which is now dominated by willows, elms, ash and cottonwoods. Planting Texas natives – all found elsewhere in the Trinity River Basin – will create new nesting areas and provide a greater and more dependable food supply for wildlife.