Experiments of dike erosion due to a wave impact

Dike erosion is a crucial issue in coastal and fluvial flood risk management. These defense structures appear vulnerable to extreme hydrological events, whose potential occurrence risk seems recently increased due to climate change. Their design and reinforcement is, however, a complex task and, although numerical models are very powerful nowadays, some physical processes cannot be predicted accurately and, therefore, physical models constitute a useful tool to investigate different features under controlled conditions. This paper discusses an experimental study of erosion of a sand dike produced by the impact of a sudden dambreak wave. The experiments have been conducted in the Water Engineering Laboratory at University of Cassino and Southern Lazio, Cassino (FR), Italy, in a small-scale rectangular channel, where a gate constitutes the barrage creating an upstream reservoir, while downstream a dike of almost-uniform non-cohesive material is positioned. Two sands with different diameter size have been used for the dike structure. The experimental evidence proves that the whole erosion process is strongly unsteady and it is significantly different from a gradual overtopping one. Moreover, the results highlight the importance of apparent cohesion for the fine-sand dike.