Lateral Migration Dynamics and Bank Erodibility of the Lowermost Mississippi River
Abstract
The lowermost Mississippi River from RK (river kilometer) 500 to the downstream head of passes displays spatial variabilities in a range of geomorphological features. For example, channel sinuosity and lateral migration rate decrease downstream, while mud content in the bank increases downstream. High sinuosity is typically associated with high channel curvature, which can promote channel migration by elevating near bank shear stress. On the other hand, high bank mud content can inhibit channel migration by enhancing bank cohesiveness. Both mechanisms can explain the spatial trend of channel migration rate of the lowermost Mississippi River, however, their relative importance remains unclear. This study tests the hypothesis that the increased mud content can reduce the erodibility of bank in the lowermost Mississippi River. The bank locations along the Mississippi River on the years of 1883 and 1913 are traced according to the US Army Corps of Engineers Survey Books. River centerlines are then determined based on the traced bank lines. Average migration rates of the river from 1883 to 1913 are calculated using a dynamic time warping method that compares the channel centerlines from the two years. Bank erodibility along the lowermost Mississippi River is estimated by calibrating a numerical model for river meandering, where the calculated average migration rates are conditioned. Preliminary results show that erosion coefficient, a term that characterizes the erodibility of bank in the model, decreases from RK 480 to RK 120 and then increases towards the river outlet (RK 0). This suggests that the erodibility of bank for the lower 120 kilometers of the Mississippi River increases downstream despite the increased mud content in bank over the same reach, which calls for alternative mechanisms, such as tidal influences. Moreover, channel bend curvature slightly increases from RK 480 to RK 350 and then decreases downstream towards the river outlet. These results suggest that the mud content in the bank is an important control on bank erodibility from RK 480 to RK 120 for the Mississippi River, while channel curvature determines the actual migration rate.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFMEP52A..05W