Measuring Trends In Riverbed Gradation: A Lower Mississippi River Case Study
Abstract
The trends of degradation and aggradation are measured in this study for the Lower Mississippi River. Historical riverbed elevation and stage data from the past hundred years were used from six gages in order to measure changes in riverbed gradation. It was found that using stage data to measure gradation changes is a superior method to using riverbed elevations, due to stage data's reliability, length of record and daily measurements. Degradation in the Lower Mississippi River was seen during the 40's, 50's and late 70's for upstream gages and during the late 20's, early 40's and the 80's for downstream gages. Memphis yielded an overall degradation level of 12 feet, Helena 6 feet, Arkansas City 13 feet and Vicksburg 10 feet for the hundred-year span. Aggradation occurred mostly during the 70's and 90's, with high spatial variation. The causes of these amounts of degradation and aggradation will need to be looked into further in future studies.
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