The Vulnerability of Damaged River and Lake Dikes for Wave Overtopping

Wave overtopping results in erosion of grass-covered flood defenses which can result in a dike breach. Damages to the dike cover decrease the cover strength and simultaneously increase the hydraulic load on the dike cover. Therefore, damages on the dike cover are vulnerable locations for wave overtopping failure. In this study, the failure probabilities of different types of damages are calculated and compared to the failure probability of a regular dike profile to determine the vulnerability of damages for wave overtopping. The method is applied to a river and lake dike where the model results show that the total failure probability is smaller on the crest and upper slope for the lake dike and higher on the lower slope and at the inner toe. The failure probability increases between a factor 4 and 14 for damaged location where the cover still contains grass vegetation. However, lake dikes are more vulnerable for damages compared to lake dikes in cases where only a bare clay cover is left. In that case, a dike with a damage is almost 3000 more likely to fail compared to a regular dike for a lake dike and around 120 times more likely to fail for a river dike.