Aquatic Habitat Studies on the Lower Mississippi River, River Mile 480 to 530. Report 2. Aquatic Habitat Mapping

Abstract

Abstract : to provide data for design of field studies to determine the impacts and ecological value of the man-made habitats formed by dike and revetment structures in the lower Mississippi River, the aquatic habitat of a 50-mile reach of the river (mile 480 to 530 Above Head of Passes, AHP) was quantitatively mapped to determine spatial relationships among and within habitat types as a function of river stage and discharge. Twelve aquatic habitat types were defined within the study reach based on hydraulic, geomorphological, and ecological criteria: main channel, natural banks, revetted banks, sandbars, dike fields, permanent and temporary secondary channels, abandoned river channels(Types I and II), oxbow lakes, borrow pits, and inundated floodplain. By use of controlled aerial photography and hydrographic survey data, aquatic habitat surface acreages were computed for three river stages (low flow = +13.2 ft, medium flow = +24.6, and high flow = +38.4 ft on the Greenville, Mississippi, gage). Results of the habitat mapping revealed a significant change in total aquatic habitat acreage with changes in river stage and discharge. At the low flow stage 18,581 acres of habitat were present. Habitat area increased to 29,020 acres at medium flow and rose to 56,902 acres for high flow--a total increase of 222 percent in area over low flow conditions.