APPARENT NON-COINCIDENT COUPLING OF THE MISSOURI RIVER TRUNK SYSTEM TO MID-CONTINENT CLIMATE CHANGE

Paleochannel research of the Missouri river has been ongoing since 2001, funded through the USGS EDMAP program (2001- Present) and the National Science Foundation (2008-2010). Quadrangle maps are prepared individually for publication through the University of South Dakota Missouri River Institute. Maps have been published in the Iowa/South Dakota reach and the central Missouri reach of the Missouri River, with current mapping being conducted on the Northwestern Missouri reach.

Distinct morphologies exist between the Iowa/South Dakota reach and the Central Missouri reach of the Missouri river, indicative of differences in an overall transition from a meandering to braided river over the last 5,000 years. Within the upper reaches in Iowa and South Dakota, there is a distinct transition from a meander to a braided system. However, the southern reach within central Missouri includes transitional morphologies between meander and braided. Current mapping between these two reaches in Northwestern Missouri includes some of these transitional forms, but not to the same extent as farther south.

Dating with Optically Stimulated Luminescence (OSL) has revealed the transition in the downstream central Missouri reach predates the transition in the Iowa/South Dakota upstream reach by at least 1000 years, indicating tributary and/or climate change influences to the south that would not affect the upstream reach.

In addition to transitional forms, distinct reverse meanders are found in the Iowa/South Dakota reach and northwestern Missouri reach, created by the accretion of successive braid bars on the cut-bank side of the loop rather than the traditional accretion on the loop interior. Reverse meanders are not found in the downstream reaches.