USING FLUVIAL SEDIMENTOLOGY TO GUIDE VEGETATION AND SHALLOW WATER HABITAT REHABILITATION IN THE BIG MUDDY NATIONAL FISH AND WILDLIFE REFUGE, MISSOURI

The Big Muddy National Fish and Wildlife Refuge in central Missouri is a test site area for shallow-water habitat reconstruction in the Missouri River floodplain. We prepared a cross section of refuge floodplain strata in support of this effort using aerial photographs and 36 hand-auger boreholes (10cm sampling intervals). Surficial floodplain deposits identified include active channel fill deposits (averaging 200 meters wide and 5 meters deep), and bar deposits composed of fine to medium grained sand with thin mud drapes. Channel fills retain water for most of the year due to richness in concave-up clay layers, and offer the most suitable location to reconstruct shallow-water floodplain habitat. Most channel fills currently support riparian trees disseminated from windblown seeds such as willows, cottonwoods, and sycamores owing to such moisture retention. The sandy bar deposits do not appear to retain water or support any arboreal vegetation for two reasons. First, the bar sands drain well and therefore prohibit growth of hydrophilic trees. Secondly, water transported seeds from more xeric trees such as oaks and hickories do not reach the floodplain due to man-made levee systems that prevent overbank flooding events that would have floated in these seed stocks. We present two recommendations: 1) plant appropriate xeric species of trees throughout currently unforested bar areas where arboreal habitat is desired. 2) Construct shallow water floodplain habitat by hollowing out extensive clay rich channel fill deposits in the western portion of the wildlife refuge, being careful not to nick the sealing clays during excavation.