|SHIELDS F D JR|
Submitted to: Aquatic Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/1995
Publication Date: N/A
Interpretive Summary: Development of many of the world's largest rivers has resulted in permanent loss of ecologically valuable low-velocity backwaters along the main channel margin. In some rivers, areas between spur dikes (fingers of stone placed for channel stabilization) have been especially hard hit by this type of sedimentation. Repetitive survey records of 26 Lower Mississippi river spur dike fields (groups of two to seven dikes close to one another) were analyzed to examine sedimentation trends. These analyses showed that most sedimentation occurred during the first five years following dike construction. Overall, backwater habitat area declined 17% and backwater volume, 38%. This study provides information which may be used by resource managers to develop habitat protection strategies.
Technical Abstract: Regions of reduced velocity adjacent to spur dikes along the Lower Mississippi River are valuable aquatic habitats. Similar zones along other large rivers have been converted to terrestrial habitats by sediment deposition. Repetitive hydrographic surveys of 26 representative groups of dikes are examined to determine the direction and rates of change. Since the dikes were constructed, the aquatic volume and area of associated low-velocity habitats have been reduced 38% and 17%, respectively. Examination of time series shows that most changes occur shortly after construction, and after initial adjustment, habitat area and volume fluctuate about a condition of dynamic equilibrium. Sedimentation rates were most rapid for dike fields constructed on the inside of bends to prevent chute development. Dike fields built to force or maintain thalweg crossings exhibited erosion rather than deposition.