Combined numerical investigation of the Gangda paleolandslide runout and associated dam breach flood propagation in the upper Jinsha River, SE Tibetan Plateau

Abstract The temporary or permanent river blocking event caused by mass movement usually occurs on steep terrain. With the increase of mountain population and land use pressure and the construction of water conservancy and hydropower projects, river blocking event has gradually attracted people’s attention and understanding. The study area (Wangdalong-Gangda reach) is located in the upper reaches of the Jinsha River and the southeast edge of the Qinghai-Tibet Plateau. Affected by strong tectonic activity in the Jinsha River suture zone and the rapid uplift of the Tibetan Plateau, in the past 6000 years, there have been at least five obvious river blocking events in the reach of about 30 km in the study area. The number and density are very rare. Combined with the field investigation, indoor interpretation, laboratory tests, optically stimulated luminescence (OSL) dating, SBAS-InSAR and previous studies, multidisciplinary approaches are used to systematically summarize the analysis methods and further the understanding of one river blocking event and multiple river blocking events from difference perspectives. Especially in multiple river blocking events, we could get the wrong results, even the opposite conclusion if interaction is not considered. Through this study, the general method of analyzing the river blocking event and the problems that should be paid attention to in sampling are given, and relatively reliable historical results of river blocking events are obtained. This method has extensive applicability to the identification and analysis of river blocking events in other areas.

Download Full-text

Huge Landslides along the Jinsha River in Southeastern Tibetan Plateau and Their Association with the Recent Activity of Jinsha River Fault Zone

10.5194/egusphere-egu2020-2815 ◽

2020 ◽

Author(s):

Zufeng Chang ◽

Hao Chang ◽

Zebin Mao ◽

Ruojin Guo

Keyword(s):

Tibetan Plateau ◽

Fault Zone ◽

Large Scale ◽

Late Quaternary ◽

Average Rate ◽

Economic Losses ◽

The Tibetan Plateau ◽

Jinsha River ◽

Water Storage Capacity ◽

Barrier Lake

&#160;&#160;&#160;&#160; The Jinsha river fault zone in the eastern margin of the Tibetan Plateau is an old suture structure after the shutting of the proto-Tethys and a large scale ultra-lithosphere fault zone consisted of&#160; 5 to 6 fault branches with a width of 50km, have a long&#160;&#160;geological evolution history. Since late Quatery, this fault zone is mainly dominated by dextral strike slip with partial thrusting component, absorbing &#160;partial energy of the extrusion movement of&#160;&#160;Tibetan Plateau. Along the fault zone, lower terraces of Jinsha river at Muronglou, Buzhong, Langzhong, Guxue, etc. were displaced, indicating the fault zone is active in late Quaternary, with an average rate of 3.5&#65374;4.3mm/ /yr. horizontally and 0.9-1.1mm/yr. vertically respectively in Holocene. Influenced by the intense fault activity of Jinsha river fault zone, this region is characterized by fractured rocks, strongly weathered surfaces.&#160;&#160;&#160;&#160;&#160; The Jinsha river, the upstream of the Yangtze river, parallel to Jinshajiang fault zone, flows from north to south, forming deep river valley and huge terrain elevation difference. Numerous huge landslides have developed along the river, for example, there are 23 giant avalanches in the 38 km long reach from Narong to Rongxue, with general volumes of 10~70 million m3 and even up to several hundreds million m3. Moreover, the landslides produce many loose clastic fragments which detonate many debris flows and river blocking. The latest disaster event is the Baige barrier lake in 2018 caused by landslide, with a water storage capacity of 524 million m3, causing tens of billions of yuan of economic losses. These landslides are distributed along the fault and its two sides, suggesting that these huge avalanches are closely related to the intense activity of the fault zone and special topography.Keywords: Huge landslide, Jinsha River, Jinsha River Fault Zone, late Quatery activity

Download Full-text