Environmental and Hydraulic Design for Riverine Wetland Restoration

This paper evaluates methods used in the environmental and hydraulic planning, design and evaluation for restoration of riverine wetlands along the Rio Grande in New Mexico. The environmental degradation brought on by anthropogenic changes in riparian and aquatic biological communities have made riverine wetland ecosystems one of the most important for conservation and restoration in the southwestern United States. The U.S. Army Corps of Engineers is planning to rehabilitate a flood control levee along 42 miles of the Rio Grande immediately below San Acacia, New Mexico. The flood control levee currently restrains the Rio Grande to a narrow floodplain that is perched as a result of sediment deposition. Opportunities for overbank flooding within the existing floodplain have further decreased due to localized scouring of the channel and regulated flows that lower spring peak discharges. The project area is important habitat for two endangered species, the Rio Grande silvery minnow (Hybognathus amarus) and the southwestern willow flycatcher (Empidonax trailii extimus). Aquatic habitat needs for silvery minnow include low velocity side channels and non-conveyance backwater areas. Low velocity flooded vegetation is a key for willow flycatcher nesting success and riparian habitat maintenance. The flood control project provides an opportunity to improve habitat for these endangered species by enhancing the structural diversity and ecological integrity of the floodplain.