Flooding and channel instability in two Ozark streams, southern Missouri

Keywords: Fluvial processes, flood hydrology, Fort Leonard Wood, Ozarks
Abstract Type: Poster Abstract

Abstract

A substantial decline in threatened and endangered freshwater mussel species has occurred since 2004 in two streams flowing through Fort Leonard Wood Army base in southern Missouri. This decline is associated with significant increases in sediment supply from Army training areas and several large floods. In an overall effort to assess the factors that may have contributed to the mussel decline and to provide recommendations to the Army for sediment and erosion control measures, stormwater improvements, and best management practices at impacted sites at Fort Leonard Wood, we are evaluating the geomorphic and hydrologic characteristics of the two streams that flow through the fort, the Big Piney River and Roubidoux Creek. We use stream gage records, channel surveys, and particle size measurements on riffles and lateral bars to report on historical changes in flood magnitudes, flood volumes, riffle stability, and stream power along these two streams. Results show that by virtually every measure, flood severity has increased substantially in recent years. On the Big Piney River (1922-2019), four of the five largest peak discharges have occurred since 2002. On Roubidoux Creek (2000-2019) unit discharges are larger than on the Big Piney River and the six largest unit discharges and 3-day flood volumes have occurred since 2008. The response of the two streams is quite different, however, with the largely unvegetated Roubidoux Creek experiencing higher stream power and characterized by more unstable riffles than the Big Piney River.