Characteristics and classification of landslide dams associated with the 2008 Wenchuan earthquake

Abstract

Background: Strong earthquakes are among the prime triggering factors of landslides, which may block rivers, forming landslide dams. Some of these dams may pose serious threats to people and property due to upstream inundation and downstream dam-breach flooding. Evaluating the stability and potential hazard of landslide dams is significant for the mitigation measures, but remains challenging. The 2008 Wenchuan earthquake (M w 7.9) in China triggered numerous landslides over a broad area, some of which dammed rivers, posing severe threats to downstream settlements. Our previous study created one of the most complete landslide dam inventories including detailed geomorphic parameters of 828 landslide dams induced by the Wenchuan earthquake. This paper presents the study of a number of representative landslide dams associated with the 2008 Wenchuan earthquake. Results: The coseismic landslides were classified into rock/debris avalanches, debris flows, rock/debris slides and rock falls. According to dam composition material and sedimentological features, landslide dams were categorized into three types: dams mainly composed of large boulders and blocks; dams composed of unconsolidated fine debris; and dams with partly intact rock strata at the base topped by large boulders and blocks or soil with rock fragments, showing two-layered or three-layered depositional structure. This classification is linked to the typology of damming landslides and considered to be a preliminary indicator of dam stability. In addition, dam stability also largely depends on valley morphometry as well as landslide runout distance and mechanism. The post-earthquake debris flow damming events induced by subsequent rainfalls are also introduced. It was found that there is still a large amount of loose sediment remaining on the slope, which may continue promoting heavy debris flows and dams in the coming years or decades. Conclusions: The classification of landslide dams proposed in this study can be used as a preliminary indicator of dam stability. More reliable assessment requires a geotechnical approach taking into account a variety of dynamic loading scenarios, and also relies on knowledge about the accurate dam and barrier-lake geometry. There is still a large amount of loose sediment remaining on the slopes, which may be reactivated and remobilized during the heavy post-earthquake rainstorms. Therefore, predicting the post-earthquake debris flows and evaluating their potential for damming rivers are still of great concern and remain as a main challenge.

Distribution Pattern of Coseismic Landslides Triggered by the 2017 Jiuzhaigou Ms 7.0 Earthquake of China: Control of Seismic Landslide Susceptibility

“…where a i is the critical acceleration of the slope at the ith point calculated by Equation (1), and N is the number of calculation points of the grid, which depends on the resolution of DEM. In this case, we used SRTM30 to calculate the slope degree, therefore there were around 1000 dots in a 1 km × 1 km cell.…”

“…Large-scale landslides can not only cause serious casualties and damage, but also block rivers and form barrier lakes in some cases, which threaten the safety of downstream areas. For example, the 2008 Wenchuan M7.9 earthquake created up to 828 barrier lakes [1], their breaches further worsening the consequences of landslides. Even small-scale landslides may block roads and affect quick rescue processes after the earthquake.…”

Formation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi

“…Several prediction formulae have been tested for estimating the breaching duration (Froehlich, 2008;Peng and Zhang, 2012;BREACH model). They lead to scattered values, ranging between 10 min and 1 or 2 h. Such discrepancies result from the limited number of real-world case studies for which information on breaching duration is available.…”

“…Many spectacular cases were reported in which earthquakes were a major trigger (Adams, 1981;Cui et al, 2012). For example, the Wenchuan earthquake in 2008 caused up to 828 landslide dams (Fan et al, 2012(Fan et al, , 2017. In addition to earthquakes, long and heavy rainfall (Li et al, 2011) as well as other local parameters can lead to slope instability and to landslide dam formation.…”

Authors response to Review comment by Martin Mergili for “Formation, breaching and flood consequences of a landslide dam near Bujumbura, Burundi”

“…Many spectacular cases were reported, in which earthquakes were as a major trigger (Adams, 1981;Cui et al, 2012). For example, the Wenchuan earthquake in 2008 caused up to 828 landslide dams (Fan et al, 2012;Fan et al, 2017). In addition to earthquakes, long and heavy rainfalls (Li et al, 2011) as well as other local parameters can lead to slope instability and to landslide dam formation.…”