Thesis Title

Relationship Of Dam Construction And Riparian Buffer Vegetation To Historical Channel Changes, Little Sac River, Southwest Missouri

Date of Graduation

Spring 2002

Degree

Master of Science in Geospatial Sciences

Department

Geography, Geology and Planning

Committee Chair

Robert Pavlowsky

Subject Categories

Hydrology | Sedimentology | Water Resource Management

Abstract

Natural and human factors have caused hydrological and geomorphic changes in most rivers in the Ozark Plateau Region of Missouri. Degraded water quality due to channel bank erosion and the release of sediment and other non-point pollutants have ranked the Little Sac River as one of the state's endangered waterways by state and federal environmental agencies. The Little Sac River drains northern Greene County and is a source of Springfield's drinking water. The purpose of this study is to document the vegetation and channel changes along a 6.4 kilometer reach of the Little Sac River, located between Fellows and McDaniel Lakes. Three main components of the study involved ortho-rectifying aerial photographs from 1938 through 1997, digitizing the channel for each year to evaluate for channel changes, and developing a system to classify riparian land cover to assess coverage area and change. Information utilized in a GIS made it possible to investigate watershed and channel morphologic relationships at a larger scale, which previously have been constrained by technical issues and time. In general, channel width decreased by 30% and channel stability increased over the 59 year period. Width reduction can be attributed to the closure of Fellows Lake dam and the stabilization of riparian vegetation cover that has acted as a trap to capture sediment during floods. Forested buffer area increased by 2.6 times and grass buffered area decreased by almost one half. A decrease of contributing drainage area of 51 percent due to dam construction has decreased bed load supply and reduced gravel bar activity, resulting in a change from a low sinuosity, gravel-bedded channel form to one with more meandering properties. These results indicate that sedimentation problems in McDaniel Lake are not related to poor buffer management and/or widespread bank erosion along the Little Sac River. However, it is not known to what degree localized channel bank erosion and tributary inputs affect downstream sediment loads.

Copyright

© Ryan G. Wyllie

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