Semester of Graduation

Summer (August) 2020

Degree

Master of Civil Engineering (MCE)

Department

Civil Engineering (water resources)

Document Type

Thesis

Abstract

The Lower Mississippi River (LMR), since the creation of the Mississippi River and Tributaries (MR&T) project, has been extensively modified to support navigation and flood risk reduction. The components of the MR&T system, implemented to support the above missions, have performed successfully for many decades, but not without contention. Rising stages in recent years have led to the questioning of the hydraulic impact of navigation dikes and river training methodologies. Multiple studies have been performed (Biedenharn, 2000, May 2017, Mayne, 2018, and Simon, 2019) that indicate these river training structures have minimal impact to stage during flood conditions. It has been hypothesized that the large batture area of the LMR may play a significant role in overbank stages, particularly at flood conditions.

The LMR batture, defined as the portion of the floodplain confined by levees and/or valley walls, is one of the largest of such riverine areas in the world and stretches continually for nearly 700 miles. Upstream of Baton Rouge, Louisiana, the batture has an average width of almost 6.5 miles and can be generally classified as a heavily forested area. At high flows, the LMR batture becomes inundated, thus activating a substantial area of amplified roughness as compared to the main channel of the Mississippi River. Through the use of a large-scale two-dimensional hydraulic numerical model, an attempt to isolate and quantify the hydraulic effects of the LMR batture area roughness on stage trends was conducted. Analysis of the model results within this effort show that the batture of the LMR represents a substantial area of flow for the Mississippi River at flood stages and the hydraulic roughness of said area has a measurable effect on water surface elevation. Common forestry management methods, such as select cutting to reduce tree density, resulted in a decrease of water surface elevation at flood stage in the range of feet.

Committee Chair

Willson, Clint

Available for download on Saturday, July 10, 2021

Share

COinS