Embankment Erosion and Retreat by Wave Action: Laboratory Experiments

Irrigation reservoirs are widely used in the Mississippi River alluvial floodplain to supplement limited groundwater resources. Constructed using local soils that are often low in clay content, the earthen embankments of these reservoirs are susceptible to wave erosion. This paper presents the findings of laboratory experiments carried out to quantify wave induced erosion and retreat of a model erodible embankment, made of natural soil, under the action of regular waves. A standardized packing procedure was developed to establish the model embankment in the wave tank. Particle size distribution, critical shear stress and the packed density of the model embankment were measured. The model embankment was exposed to wave action for up to 48 hours, and the amount of eroded material and retreat were monitored. Relationships were established between erosion, retreat rate, and incident wave characteristics. The waves quickly undercut the upper part of the embankment face and formed a scarp, which retreated in discrete slump failures until an equilibrium profile was established. The results of the experiments showed that eroded volume was linearly related to retreat distance for the conditions of this study. A unified empirical relationship was established for erosion and retreat rates, which depended only on wave height for the tested embankment characteristics.