Evolution of the Zumbro River as a Response to Ice-Sheet Retreat
River terraces, the remnants of ancient river floodplain surfaces, provide a glimpse into the evolution of a river through time. The terraces of the Zumbro River, a tributary of the Mississippi River in southeastern Minnesota, were chosen for study due to the river’s complex history involving glacial retreat and the drop in the elevation of the Mississippi River. I manually digitized river terraces using a 5-meter resolution Digital Elevation Model and plotted their elevations against the distance along the centerline of the river valley. The results indicate one high-elevation terrace level indicative of the floodplain surface at the time of the Last Glacial Maximum, as well as lower terraces indicating a response in the Zumbro river system to a drop in base level of the Mississippi River. These findings provide us with a more complete understanding of the history of the Zumbro River system, and will help construct a reference against which we can compare computer models of fluvial evolution.