Prediction of the behaviour of landslide dams using a geomorphological dimensionless index

Abstract

Landslide dams are a common phenomenon. They form when a landslide reaches the bottom of a river valley causing a blockage. The first effect of such a dam is the infilling of a lake that inundates the areas upstream, while the possibility of a sudden dam collapse, with a rapid release of the impounded waters, poses a higher flood risk to the downstream areas.The results of the main inventories carried out to date on landslide dams, have been examined to determine criteria for forecasting landslide dam evolution with particular emphasis on the assessment of dam stability. Not all landslides result in the blockage of a river channel. This only occurs with ones that can move a large amount of material with moderate or high-velocities. In most cases, these landslides are triggered by rainfall events or high magnitude earthquakes. A relationship also exists between the volume of the displaced material and the landslide dam stability.Several authors have proposed that landslide dam behaviour can be forecast by defining various geomorphological indexes, that result from the combination of variables identifying both the dam and the dammed river channel. Further developments of this geomorphological approach are presented in this paper by the definition of a dimensionless blockage index. Starting with an analysis of 84 episodes selected worldwide, it proved to be a useful tool for making accurate predictions concerning the fate of a landslide dam.

Morphological analysis and features of the landslide dams in the Cordillera Blanca, Peru

“…Deterministic approaches are often adopted to simulate the features comparison and predict evolutions. A common methodology in such analysis is the formulation of geomorphological indexes based on morphometrical parameters of the two involved systems, the river and the slope, including dam volume, valley width, and watershed area (Swanson et al 1986;Ermini and Casagli 2003;Korup 2004;Dong et al 2011;Peng and Zhang 2012). Landslide dam formation and stability predictions are not an easy task, due to the number of factors involved, and they are assessed through critical threshold index values.…”

Large-Scale Rockslide Inventories: From the Kokomeren River Basin to the Entire Central Asia Region (WCoE 2014–2017, IPL-106-2)

“…Considering the unknown morphology of both the source zone and depositional area prior to slope failure, the accuracy of the volume assessment is estimated as ±30 -50%. However, such accuracy seems to be sufficient for the statistical analysis of basic relationships between the magnitude of the phenomena (characterized by its volume) and its main geometrical parameters (runout, area, H/L ratio) and such parameter as the DBI-the Dimensionless Blockage Index (Ermini and Casagli 2003). It is higher than the scatter of the landslide volume versus area relationships, which usually are about 1 order larger (Honious et al 1997;Guzetti et al 2008).…”

Earth Observation for Earthquake Disaster Monitoring and Assessment

“…Therefore, the risk assessment of barrier lakes becomes very important. The dimensionless blockage index (DBI) was introduced by Casagli and Ermini (Ermini et al, 2003;Liu et al, 2009) to evaluate the stability of a dam:…”