Investigating Wave Erosion For A Model On-Farm Storage Reservoir Embankment in a Laboratory Wave Tank

Highlights On-farm water storage reservoirs constructed using locally available soil are susceptible to wave-induced erosion. Accurate prediction of embankment erosion informs best management practices to increase reservoir lifespan. A non-cohesive model reservoir embankment was tested in a laboratory environment to expand on prior study. Results show three stages of erosive behavior and that initial conditions affect early embankment degradation. Models developed for coastal erosion prediction tend to underestimate the erosion of inland reservoir embankments. ABSTRACT. The unprotected embankments of on-farm water storage reservoirs in the Mississippi Delta are subjected to erosion due to wind-driven waves, and there is a need to predict the rate of erosion to aid in mitigation and planning efforts. In order to advance the mechanistic understanding of levee erosion, laboratory experiments were used to investigate the response of embankments to wave attack. In this study the erosion and recession processes of a model sand embankment were measured for a range of regular wave heights and two initial slope conditions in a laboratory wave tank. Embankment profiles were measured using time-lapse photography processed through image analysis. Embankment retreat, volume of onshore embankment erosion, and volume of offshore deposition were quantified, and results indicated three stages of embankment evolution. Comparisons with previously published data show that for the range of soil types considered, the rates of embankment retreat and erosion were dependent on both bulk soil properties and embankment geometry during the active stage of embankment evolution. Two analytical models meant to predict embankment retreat and onshore erosion were shown to underpredict the quantities observed in this study. A semi-empirical model originally developed using cohesive earthen soil erosion data was found to accurately predict erosive embankment behavior during the active stage. Therefore, the model shows potential for practical application in future field investigations where long-term background data may be available and aids in understanding the properties of mechanical wave erosion in small, closed, inland reservoirs. Keywords: Embankment retreat, Irrigation reservoir, Sand embankment, Wave erosion.