Alternatives for Riverine Backwater Restoration by Manipulation of Severed Meander Bend

Current thinking in stream ecology emphasizes the dependence of large riverine ecosystems on the materials and habitats provided by floodplain backwaters. However, these types of habitat are becoming increasingly rare as development is transforming floodplain landscapes in fundamental ways. Despite the large sums of money spent on control and management of water pollution, environmental quality continues to decline due to diminished hydrological connectivity between rivers and floodplain backwaters even as water quality improves. Along rivers with wide valley bottoms, functional values associated with floodplain water bodies such as abandoned channels, sloughs, severed meander bendways and borrow pits have been reclaimed by re-opening relatively small connecting channels. Reconnection projects typically involve dredging connecting channels or installing weirs or other types of water control structures. Backwater inflow augmentation is sometimes necessary for reconnection due to changes in bed elevation that have isolated backwaters from the main channel. Flow augmentation may involve installing and operating pumps on a permanent or seasonal basis. Design approaches are illustrated using a case study from a 2.5-km long severed bendway adjacent to the Coldwater River, Mississippi. Costs for project construction, operation and maintenance and benefits to fish habitats are projected and compared. Introduction Prior to about 1900, much of the area presently under cultivation in the U.S. was characterized by low relief and gentle undulating topography such as ridge and swale patterns that produced high levels of physical and biological diversity. Vegetation cover was comprised of virgin bottomland hardwoods, cane breaks, and