Analysis of the Impacts of Dikes on Flood Stages in the Middle Mississippi River

Abstract

The US Army Corps of Engineers has constructed numerous river engineering structures in and along the Middle Mississippi River. River training and bank stabilization measures include pile dikes, stone dikes, bendway weirs, chevrons, and revetments. Concerns have long been voiced about the effects of these structures on flood stages. Recent debate concerning the scientific basis for these concerns has been invigorated by specific gauge analysis that appears to show a rising trend in flood stages over the past 150 years. This paper attempts to advance the debate by providing an objective review of the specific gauge analysis technique that explains how the method should be performed and the results interpreted; identifies strengths and limitations; examines the uncertainties associated with application to the Middle Mississippi River given the available data; and reassesses the conclusions that can and cannot reasonably be drawn regarding the impacts of dikes and levees on flood stages, based on specific gauge analysis of the Middle Mississippi River. The application of specific gauge analysis to records from the St. Louis gauge, by using methods that carefully follow the guidelines set out in this paper, provides no evidence that dike construction has raised flood stages, but indicates that rises in flood stages are more probably related to levee building.