Experiment in Passive Habitat Rehabilitation, Lower Missouri River

Robert B. Jacobson and Mark S. Laustrup
U.S. Geological Survey, 4200 New haven Road, Columbia, MO 6520, 573-876-1844, robb_jacobson@usgs.gov

Raymond E. Arvidson and Curt S. Niebur
Dept of Earth and Planetary Sciences, Washington University, St Louis, MO 63130

The "Great Flood" of July 1993 broke through levees on the Missouri River at Lisbon Bottom near Glasgow, Missouri. Subsequent large floods in 1995 and 1996 eroded more of the Bottom and connected levee- break scours to form a 3-kilometer since-channel chute. The chute has attracted considerable interest because of the hazard it poses to barge navigation and because of its potential value as fish and wildlife habitat. The chute also has many similarities to highly engineered side-channel rehabilitation projects on the lower Missouri River. However, unlike engineered rehabilitation projects, the Lisbon Bottom chute has been allowed to erode and deposit freely and create natural side-channel habitats. As such, the Lisbon Bottom chute provides a field experiment in passive, minimum-cost flood-plain rehabilitation. Repeated mapping of the chute, its bathymetry, substrate, and velocity distributions indicate that it is evolving from a narrow, fast channel toward a wide, shallow channel similar to chutes that existed before extensive channelization of the Missouri River. Concurrently, sinuosity has increased, although not enough to decrease the channel slope to that of the main channel. Bathymetric, bed-classification, and acoustic Doppler velocity data indicate that the naturally evolving chute provides habitats that are not well represented in the main channel.