Case Study of Dam Overtopping from Waves Generated by Landslides Impinging Perpendicular to a Reservoir’s Longitudinal Axis

Abstract

Landslide-generated impulse waves in dammed reservoirs run up the reservoir banks as well as the upstream dam slope. If large enough, the waves may overtop and even breach the dam and cause flooding of the downstream area with hazardous consequences. Hence, for reservoirs in landslide-prone areas, it is important to provide a means to estimate the potential size of an event triggered by landslides along the reservoir banks. This research deals with landslide-generated waves and the overtopping process over the dam crest in a three-dimensional (3D) physical model test, presenting a case study. The model set-up describes the landslide impacting the reservoir in a perpendicular manner, which is often the case in natural settings. Based on the experimental results, dimensionless empirical relations are derived between the overtopping volume and the governing parameters, namely the slide volume, slide release height, slide impact velocity, still-water depth, and upstream dam face slope. Predictive relations for the overtopping volume are presented as applicable for cases relating to the specific model set-up. Measured overtopping volumes are further compared to a two-dimensional (2D) case reported in the literature. An important feature regarding the overtopping process for the 3D case is the variation in time and space, resulting in an uneven distribution of the volume of water overtopping the dam crest. This observation is made possible by the 3D model set-up, and is of value for dam safety considerations as well as for foundation-related issues, including erosion and scouring.

Physical Model Study on Discharge over a Dam Due to Landslide Generated Waves

“…The aforementioned studies describe a way of predicting the overtopping discharge with a two-step approach, basing on a 2D experimental setup where slides impact the longitudinal direction of the reservoir. A recent paper by Tessema et al [21] studied the case of landslides impacting a reservoir from a lateral direction (see Figure 1b) with a 1:190 laboratory scale model for a typical dam of 60 m height. A new empirical equation for the dam overtopping volume as a function of the slide volume, slide release height, slide impact velocity, still water depth, and upstream dam slope was derived for the case studied.…”

Tsunami Science and Engineering II

“…This book includes nine excellent contributions [3][4][5][6][7][8][9][10][11] to this special issue published between 2018 and 2019. The overall aim of the collection is to improve modelling and mitigate the destruction of tsunamis and the negative effects they have on us and our environment.…”

“…The order of the nine articles [3][4][5][6][7][8][9][10][11] in this book follows the three tsunami phases: generation, propagation and their effects. The first article from Perez del Postigo et al [3] focuses on tsunami generation and propagation.…”

“…The following two articles from Tan et al [4] and Tessema et al [5] involve the entire process of subaerial landslide-tsunami generation, propagation and runup. This is challenging, both from a numerical (typically requiring several models) and physical modelling point of view given that multiple physical processes at different length and time scales need to be modelled.…”

“…The up to 133 m high tsunamis decay relatively fast with distance from Es Vedrà to 14.2 m offshore Cala d'Hort (3 km from the source) with a maximum run-up height of around 21.5 m. Nearly all numerical and physical model studies into landslide-tsunamis released the slide in the longitudinal direction of the flume or basin, which does not well represent slide impacts in narrow reservoirs in lateral direction. This shortage motivated Tessema et al [5] to investigate landslides impacting a reservoir in lateral direction in a 1:190 laboratory scale model for a typical dam of ≈60 m in height. They derived new empirical equations for the dam overtopping volume in a function of the slide volume, slide release height, slide impact velocity, still-water depth and upstream dam face slope.…”