PRELIMINARY DISCUSSION OF THE FREQUENTLY DEBRIS FLOW EVENTS IN SEDONGPU BASIN AT GYALAPERI PEAK, YARLUNG ZANGBO RIVER

We used Landsat and other high-moderate space resolution images to analysis the glacial retreat in the recent 40 years of Sedongpu Basin, and combed the eight times debris flow blocking Yarlung Zangbo river incidents of Sedongpu Basin after 2014. Combined with the radar and meteorological data, we analyzed the reasons of frequent collapse disasters occurred in the basin. Then we found the following factors. First, the "steep-gentle-relative steep" ladder terrain is the foundation of the frequent occurrence of the debris flows in Sedongpu Basin. Second, the debris flow always block the channel at a large extent. Third, there are lots of crevasses in the glacier trailing edge. Fourth, earthquake and abundant rainfalls also lead to the frequent debris flow of Sedongpu Basin. Combined the above factors, we speculate the glacier avalanche induced debris flow(GAIDF) of Sedongpu Basin will happen frequently for a long time with typical periodicity. So, we suggested to establish a long-time monitoring and warning system for the Yarlung Zangbo Grand Canyon in order to provide effective support to the emergency work of Sedongpu Basin glacier debrisflow.