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|Title:||Morphologic effects of lower Mississippi River dike fields|
|Authors:||University of North Carolina at Charlotte.|
Environmental and Water Quality Operational Studies (U.S.)
Nunnally, Nelson R.
Beverly, Linda B.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Dikes are used extensively on large, meandering rivers to help maintain navigation channels. Dike fields alter flow velocities and sedimentation patterns, thereby affecting river morphology and the amount and quality of aquatic habitat. Some investigators have theorized that sedimentation induced by the dike fields constructed on the lower Mississippi, largely since 1960, is altering river morphology and aquatic habitat in a manner similar to the changes that have been observed in the lower Missouri. Others are of the opinion that dike fields on the lower Mississippi do not typically fill completely with sediment, and the pools they contain have increased the amount of slack-water habitat. Low-water photographs taken in 1962 and 1976 and comprehensive hydrographic surveys done in 1962-64 and 1974-75 were used to measure morphologic changes in diked and undiked reaches. River surface area between river miles 320 and 954 was classified as main channel, secondary channel, slough, chute, or pool. The 1962 and 1976 areas in each category were measured from the photographs. River stage at time of photography averaged about 2 ft (0.6 m) lower in 1976, so 1976 measurements were adjusted for stage differential, based on width measurements taken from the hydrographic surveys. Results were summarized for diked and undiked reaches. Total river area remained relatively constant. Secondary channel area decreased by 16.28 square miles (42.2 sq km) (-38.6 percent), but this was offset by increases in sloughs, chutes, and pools. Sloughs increased by 7.13 square miles (18.5 sq km) (+53.2 percent), chutes by 6.92 square miles (17.9 sq km) (+44.8 percent), and pools by 5.09 square miles (13.2 sq km) (+2,357.1 percent). Practically all of the loss occurred in secondary channel area, and all of the increase in sloughs, chutes, and pools occurred in diked reaches. Analysis of changes by age of dike field revealed no noticeable trends or patterns.
|Rights:||Approved for public release; distribution is unlimited.|
|Appears in Collections:||Miscellaneous Paper|
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