ANALYSIS OF THE CONTROLLING FACTORS OF LANDSLIDE DAMMING AND DAM FAILURE : AN ANALYSIS BASED ON LITERATURE REVIEW AND THE STUDY ON THE MERIDIONAL RIVER SYSTEM OF EASTERN TIBETAN PLATEAU
In the deep valleys of these meridional rivers located on the eastern margin of the Tibetan Plateau, a large number of ancient landslide dammed lakes were distributed. These paleolakes retained tens of thousands of years in the fast flowing rivers. What are the causal factors of these paleolakes? This paper analyzed this special phenomenon and the geological significance of the paleolakes. From the geomorphological perspective, tectonic eastward extrusion of the Tibetan Plateau effected and controlled the meridional river system. The complexity of landscape in these rivers and frequent earthquakes provide a favourable spot for damming event. For dammed lakes, the lake volume, the dam height, the length and the internal structure affect its stability. For rivers, the existence of successive large dammed lakes can cause the "step-pool system" and knickpoints, which can reduces the fluvial potential energy and preserves the dammed lake for a long time. Climate changes show cyclical impacts on the processes of erosion-deposition. The interglacial of 40~25ka with abundant rainfall and high lake-level stages of the Tibetan Plateau, as well as the strong river discharge capacity caused mass movements and landslides during the wet period. The glacial of 25~10ka with weak river discharge capacity is benefit for stability of the dammed lakes. Climate warming in Holocene was accompanied by fast dam failure under the stronger riverbed undercutting. Earthquake-induced landslides and the rockfall provide better source materials of the natural dams. Narrow-deep outburst on consolidated natural dams caused the remains of lacustrine strata of dammed lake in stream terraces. Finally, this paper tentatively discussed the coupling of tectonic -climate system in surface erosion-deposition processes through damming events and dam failures.