The Sedimentology and Internal Structure of Landslide Dams—Implications for Internal Erosion and Piping Failure: A Review

Detailed information on the internal structure and sedimentological characteristics of landslide dams is important for natural dam hazard assessment studies. The materials composing landslide dams play a significant role in determining their overall longevity and stability. This, on the other hand, is linked to their source stratigraphy and the degree of fragmentation and pulverization undergone by the materials during their transport and emplacement history. Overall, the time of failure of landslide dams and the magnitude of the outburst flood depend on the internal characteristics of the impoundment, such as the grain size distribution, grain shape, degree of consolidation, presence of subsurface discontinuities, erodibility, and clay percentage. The evolution of internal erosion and piping in landslide dams has been ascribed to the relationship between the internal structure of the dam and the discharge rate through the impoundment. This paper presents a systematic review of the influence of the internal structure and sedimentological characteristics of landslide dams on the piping failure of natural river blockages. The paper highlights the processes of emplacement of landslide dams, the internal modification of the sediment during transport, the different facies assemblages and their role in the evolution of internal erosion and piping. Results obtained from the microtremor (MTM) chain array survey gave a better understanding of the evolutionary history of landslide dams. Furthermore, preliminary results obtained from laboratory experiments gave credence to the notion that the longevity and stability of landslide dams formed by translational mass movements are higher than those formed by rock avalanche processes.