Distribution patterns and formation mechanisms of stable landslide dams in the Qinghai-Tibet plateau: a preliminary study

The eastern margin of the Qinghai-Tibet Plateau is renowned for its deep gorges and significant tectonic activities, which makes it a region prone to the formation of natural dams. However, there are limited studies focusing on the stable natural dams in this area. To elucidate the distribution of stable natural dams and the factors contributing to their long-term stability, we established an inventory of stable dams with the aid of remote sensing mapping and detailed field investigations. The findings indicated that there are at least 348 stable natural dams within the Qinghai-Tibet Plateau, comprising 294 current natural dams and 54 paleo natural dams. The origins of these stable natural dams included rock avalanches (36.5%), rock slides (7.7%), rock falls (23%), and moraine (32.8%). We summarized six types of stable dam geomorphometry. The origin types contributing to the formation of stable landslide dams include rock avalanches, landslides, and glacial moraine damming events. This leads to the formation of dam structures categorized as follows: inverse grading from high-speed long-runout landslides, slipped or seated pseudo-bedrock structures from short-runout landslides, boulder-dominated architectures from proximal avalanche river-blocking events, and soil-rock matrices resulting from damming by interbedded soft-hard rock sequences or heterogeneous deposits. The structural configuration of the dam plays a critical role in ensuring the long-term stability of landslide dams.