Assessment of levee treatments for an irrigation reservoir in Arkansas

Authors: OZEREN, YAVUZ - University Of Mississippi; Wren, Daniel; YASARER, HAKAN - University Of Mississippi

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2018
Publication Date: 10/17/2018
Citation: Ozeren, Y., Wren, D.G., Yasarer, H. 2018. Assessment of levee treatments for an irrigation reservoir in Arkansas. Transactions of the ASABE. 61(5):1677-1689. https://doi.org/10.13031/trans.12983.
DOI: https://doi.org/10.13031/trans.12983

Interpretive Summary: Irrigation reservoirs are used to reduce dependence on limited groundwater resources in the Mississippi river alluvial floodplain, particularly in the state of Arkansas. The earthen embankments that enclose the reservoirs are susceptible to erosion by wind-generated waves. In an effort to assess levee protection strategies, a range of treatment techniques, including levee configurations and surface treatments, were applied to the embankments of the University of Arkansas Pine Bluff (UAPB) Lonoke Demonstration Reservoir in 2007. The treatment techniques included 17 slope configurations along the east and west embankments and 5 mechanical treatments along the north and south embankments. Embankment erosion was measured by comparing new surveys conducted in 2015 and 2017 with as-built information provided by the Natural Resources Conservation Service (NRCS). The change in levee profile between the surveys was used to quantify the effectiveness of the treatment methods for protection against wave action. It was found that only soil cement, fly ash, and geo-textiles were effective at reducing levee erosion. All of the slope configurations suffered severe erosion the the 10-year period between completion and the 2015 survey. Levee sections with the greatest amount of erosion were typically on the north and south ends of the reservoir, which was caused by the strongest winds and longest axis of the reservoir being oriented in a north-south direction.

Technical Abstract: On-farm irrigation reservoirs are commonly used in the Mississippi River Valley alluvial floodplain to supplement limited groundwater resources. The inner slopes of the earthen embankments that enclose these reservoirs are subjected to continuous erosion due to wind-generated waves. Various methods have been used to protect the embankments, but none of them have been shown to be both sustainable and cost effective. In an effort to assess levee protection strategies, a range of treatment techniques, including levee configurations and surface treatments, were applied on the embankments of the University of Arkansas Pine Bluff (UAPB) Lonoke Demonstration Reservoir in 2007. The treatment techniques included 17 slope configurations along the east and west embankments and 5 mechanical treatments along the north and south embankments. Embankment erosion was measured by comparing new surveys conducted in 2015 and 2017 with as-built information provided by the Natural Resources Conservation Service (NRCS). The change in levee profile between the surveys was used to quantify the effectiveness of the treatment methods for protection against wave action. An Artificial Neural Network (ANN) prediction model was developed to establish relationships between erosion parameters (eroded area and maximum retreat) and four independent variables (existence of berm, face slope, maximum effective fetch and probability of wind speed). Data from 27 sections were used for training and data from 7 sections were used for testing the ANN model. Almost all of the slope treatments were significantly eroded over the 10-years that elapsed between construction and the surveys. Although having a berm did not reduce the total eroded volume significantly, in most cases it delayed the bank retreat. For any two identical slope configurations, the one with the longest fetch typically had at least slightly higher erosion and retreat. In general, milder slopes performed better than steeper slopes. The survey results showed that geo-textiles, fly ash, and soil cement were more effective at reducing wave erosion than the slope treatment methods.