Date of Graduation

Fall 2023


Master of Natural and Applied Science in Geography, Geology, and Planning


Geography, Geology, and Planning

Committee Chair

Robert Pavlowsky


Climate and land use can control the flood regime of a river and regulate channel form and size over periods of decades to centuries. Recent climate change has increased rainfall intensity and flood magnitude/frequency in many watersheds in the midwestern United States. Thus, river channels affected by more frequent and larger floods are expected to respond by increasing width (or depth) by fluvial erosion to accommodate larger peak discharges. This hypothesis was evaluated along 186 km of the Big River in southeast Missouri by analysis of historical aerial photography, precipitation studies, and United States Geological Survey (USGS) flow gage records. From 1937 to the 1970s, nine of eleven channel segments in Big River decreased in average width by 10% or more with the remaining two segments showing no significant change. In contrast, from 1970 to 2018 all eleven segments increased in width by more than 10% and all but one segment had a wider average width compared to the channel width in 1937. To verify these results, a survey of channel width changes was completed for all USGS gaging sites in the Ozarks Highlands with sufficient records for flood analysis. Like the Big River, most sites indicated more frequent and larger floods since the 1970s. Further, channel widening was indicated at 16 of 24 reaches in other watersheds since 1990 at rates ranging from 0.18 m/yr to 0.26 m/yr. Given that land use has not changed measurably during this period, with even more forest cover present today, climate-driven flooding is probably the main cause of recent channel widening in Big River. Further, while more in-depth study is needed, recent channel widening has been documented at most flow gaging sites along rivers in the Ozarks Highlands. These channel adjustments to larger floods are not only indicative of increased flood risk, but also of physical disturbances to aquatic habitats and water quality problems due to bank erosion and the remobilization of stored sediment.


climate change, river planform, bars, flood, aerial photograph

Subject Categories

Geomorphology | Hydrology


© Patrick Saulys

Open Access