Effects of Longitudinal Training Walls on Two-Dimensional Flow Structure, Sediment Transport, and Bed Aggredation Using Numerical Methods and Sediment Core Analyses in Grand River, Michigan

Longitudinal training walls (LTWs) are structures oriented parallelly with the main flow and separate the channel into two sub-channels. One channel acts as the main navigational channel and the other is considered a secondary side channel. The long-term effects of the LTWs on morphodynamics and deposition remain poorly understood. This study investigated the long-term effects of the LTWs on flow, sediment transport and long-term deposition of the Grand River using numerical approaches and sediment core analysis. The effects of LTWs on 2D flow dynamics and sediment transport were investigated by using numerical approaches. The long-term deposition under the influence of walls was studied by sediment core analyses. Training walls were simulated in the numerical domain to see the long-term effects on flow parameters and sediment transport with and without the presence of walls. The results show how the effects on flow and sediment transport for the initial conditions since 1906 changed over time in different stages of deterioration and the effects vary with the spatial orientation of the walls. Simulated morphologic evolution matches with the pattern of current channel evolution and shows where the long-term deposition occurred under the influence of the walls. Finally, age-dating of the cores reveal depositional rates of river island and floodplain formation under the influence of the walls. This research will be used as a guideline for researchers and river managers for understanding the long-term evolution history and the different ways this river behaved in the past in regards to these walls. Also, the research suggests alternative wooden structures and informs areas of environmental management concerns.