|Shields Jr, Fletcher|
Submitted to: Proceedings of the World Water and Environmental Resources Congress
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2005
Publication Date: 8/1/2005
Citation: Shields Jr, F.D., Knight, S.S., Stofleth, J.M. 2005. Alternatives for riverine backwater restoration by manipulation of severed meander bend. Walton, R., editor. Proceedings of the 2005 World Water and Environmental Resources Congress: Impacts of global climate change. American Society of Civil Engineers Proceedings 173(566), doi: 10.1061/40792(173)566, Reston, VA, CD-ROM. Interpretive Summary: Natural stream ecosystems feature numerous backwater regions that are frequently connected to the main channel during high flow events. These backwaters are important habitats for stream corridor organisms and may trap and process pollutants. However, backwaters are usually eliminated by channel management in agricultural watersheds. The current state of science with regard to rehabilitation of riverine backwaters was reviewed for relevance to application to a specific degraded backwater site along the Coldwater River, Tunica County, Mississippi. Four major alternatives for backwater rehabilitation were identified and compared. At least some of the physical properties of a less-perturbed backwater system could be regained by pumping water from the river into the degraded backwater an average of 27 days per year. These findings will provide a basis for a field experiment that may lead to standard practices.
Technical Abstract: 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 populations are projected and compared.