Erosion Prediction On Irrigation Reservoir Embankments

Groundwater is the primary source for irrigation in the Lower Mississippi River Basin (Delta) which has resulted in significant depletion of the Mississippi River Valley Alluvial Aquifer (MRVAA). A widely adapted method to reduce the dependence on groundwater resources is the use of irrigation reservoirs and tailwater recovery systems. The embankments of the irrigation reservoirs are built using locally available soils and typically left unprotected, which makes them susceptible to erosion due to wind generated waves and surface runoff. In this study, laboratory experiments and numerical simulations using XBeach, an open-source coastal modeling software developed by Deltares, were carried out in order to understand the causes of wave induced erosion of earthen embankments and provide accurate prediction methods. A one-dimensional numerical wave tank was created using the XBeach non-hydrostatic mode to simulate the erosion and retreat of a sand embankment due to regular waves. The numerical wave tank simulations were compared with the laboratory experiments that were carried out in a wave tank at the USDA-ARS National Sedimentation Laboratory to study wave erosion of a sand embankment (𝐷50 = 0.5 mm). The results showed that the XBeach model approximately predicted the erosion profile and its progression, except during the initial formation of the beach slope. The simulation results were also compared with an analytical model. It was concluded that XBeach is an adequate tool for predicting retreat in sandy soil embankments for individual storm events. This paper summarizes the key findings of the laboratory and numerical experiments.