Abstract
Uplift of the Qinghai-Tibetan Plateau has resulted in rapid incision of rivers along the margin of the plateau. Landslides occur frequently as a consequence of increasing bank slope and potential landslide energy due to stream bed incision or lateral bank erosion on the concave banks at bends. The Fencha Gully is on the eastern margin of the Qinghai-Tibetan Plateau and is developing on a huge landslide body. Flume experiments were conducted on the base of the field investigation to study the mechanism of landslides induced by stream bed incision. The experiments were designed with a length scale ratio of 1:20. Landslides and stream bed incision with loose sediment were observed and analyzed. The results show that landslides are induced as a result of stream bed incision. The potential landslide energy is defined, which increases quickly with an effective incision depth coupling vertical incision and lateral bank erosion. The occurrence of landslides can be attributed to increasing incision depth and potential landslide energy. Results indicate that the critical effective incision depth is 4.0–6.0 m. A critical value of the potential landslide energy is found from the experiments. Landslides occur if the potential energy exceeds the critical energy, which is 2.24×104 t·m/s2 for the Fencha Gully. The incision depth and potential energy of landslides from the Fencha Gully agree well with the results.
Highlights
Bed incision occurs widely in mountain rivers no matter with sediment-bed or rock-bed (Ouimet et al, 2008; Wohl, 2010; Berger et al, 2011; Hobley et al, 2011)
An experimental study of landslides was done with a flume of high bed gradient and bank slopes consisting of loose sediment, to study the mechanism of landslides induced by stream bed incision and the increasing potential energy for landslides
The results show that stream bed incision and lateral bank erosion occur due to water flow scouring
Summary
Bed incision occurs widely in mountain rivers no matter with sediment-bed or rock-bed (Ouimet et al, 2008; Wohl, 2010; Berger et al, 2011; Hobley et al, 2011). The incision still provide a fundamental inducement at the basin - or channel-scale, and has become a major concern for mountain river management (Whipple, 2004; Safran et al, 2005; Wang et al, 2015). This can be interpreted as that with the lack of support from slope toe, the destabilization of landslides is promoted (Gonzalez-Diez et al, 1999; Lacoste et al, 2011; Larsen and Montgomery, 2012; Doi et al, 2020). It is indicated that mass movement rate is highly correlated to incision rate (Larsen and Montgomery, 2012), implying that stream bed incision could be a driving force for hillslope morphology (Mudd and Furbish, 2007; Korup et al, 2010; Chang et al, 2018)
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