PATTERN CHANGES ON THE HOLOCENE MISSOURI RIVER

The Missouri River is a continent-scale channel flowing from Montana through Missouri where it connects with the Mississippi River. The river drains one-sixth of the conterminous US. Through the EDMAP program, eight students from Texas Christian University, under the advisement of Dr. John Holbrook, were able to focus on reconstruction of the Holocene development of the Missouri River Valley. Mapping concentrated on the reach between Nebraska City, Nebraska and Nemaha, Kansas. The target of research during the summer of 2012 was the transition from a meandering river to a braided river pattern, a transition that is observed both upstream and downstream from this reach. In teams of two, students mapped floodplain strata of the Nebraska City, Sydney, Hamburg, Peru, Rockport, Nemaha, Julian, and Langdon. Using air photos, students hypothesized landforms and associated lithofacies and tested these hypotheses with the use of hand augers. Maps were constructed in a GIS format. Mapping reveals a sharp transition from meandering to braided consistent with maps developed from reaches farther to the north. The timing of this transition is still being determined. The floodplain also reveals reverse meanders that developed during the braided phase. Mapping documents a long part of the reach of the river spanning the length between the confluence of the Platt and Kansas rivers to the main Missouri trunk. This is part of a continuing project to map the extent of the lower Missouri River Valley through student mapping efforts.