Landslide-lake outburst floods accelerate downstream hillslope slippage

Abstract

Abstract. The Jinsha River, which has carved a 2–4 km deep gorge, is one of the largest SE Asian rivers. Two successive landslide-lake outburst floods (LLFs) occurred after the 2018 Baige landslides along the river. Using Sentinel-2 images, we examined the LLF impacts on downstream river channels and adjacent hillslopes over a 100 km distance. The floods increased the width of the active river channel by 54 %. Subsequently, major landslides persisted for 15 months in at least nine locations for displacements >2 m. Among them, three moving hillslopes ∼80 km downstream from the Baige landslides slumped more than 10 m 1 year after the floods. Extensive undercuts by floods probably removed hillslope buttresses and triggered a deformation response, suggesting strong and dynamic channel–hillslope coupling. Our findings indicate that infrequent catastrophic outburst flooding plays an important role in landscape evolution. Persistent post-flood hillslope movement should be considered in disaster mitigation in high-relief mountainous regions.

Seismic Monitoring and Geomorphic Impacts of the Catastrophic 2018 Baige Landslide Hazard Cascades in the Tibetan Plateau

“…The two Baige landslides transported 3.4 × 10 7 m 3 of sediments into the Jinsha River. Following the landslide dam breaches, the catastrophic outburst floods not only entrained sediments from the landslide dams but may have also eroded and scraped the river channel, bank, and hillslope (Yang et al., 2021), which resulted in a significant increase in the downstream sediment flux in 2018. As these sediments are transported downstream, some are deposited along the way before being successively re‐transferred downstream during the next monsoon seasons, which explains why the recorded sediment fluxes after the hazard cascades are higher than the expected sediment flux level given annual runoff in the following years (Figure 5).…”

Detection of slow‐moving landslides through automated monitoring of surface deformation using Sentinel‐2 satellite imagery

“…The median total displacement of this landslide over the past 7 years Slow-moving landslides are sensitive to changes in climate, both directly through changes in their hydrology and water availability (Ardizzone et al, 2023;Gariano & Guzzetti, 2016;Handwerger et al, 2019Handwerger et al, , 2022 and indirectly through changes in their boundary conditions (Dai et al, 2020;Mititelu-Ionus¸et al, 2011;Van Wyk de Vries, Bhushan, et al, 2022;Yang et al, 2021). The close match between the average displacement of the Oriental lateral moraine and lateral retreat rate of the glacier is an example of this second category.…”

“…Rapid climate warming is a driving factor for the current high rates of ice loss (Abdel Jaber et al, 2019; Willis et al, 2012), which in turn impact the stability of surrounding slopes. Other changes in local conditions such as vegetation cover, snow accumulation, rivers and landslide dam or glacial outburst floods can also affect the long‐term motion of slow‐moving landslides (Cook et al, 2018; Mititelu‐Ionuș et al, 2011; Van Wyk de Vries, Bhushan, et al, 2022; Yang et al, 2021). In many instances, slow‐moving landslide motion is driven by the availability of water which increases internal pore‐water pressure and decreases the frictional strength of slopes (Bogaard & Greco, 2016; Lacroix et al, 2020).…”

Quantitative assessment of the erosion and deposition effects of landslide-dam outburst flood, Eastern Himalaya

“…1 a). In rapidly uplifting mountain belts, fluvial, glacial and hillslope erosion processes are closely linked 62 , 63 . Therefore, the complex patterns associated with short-lived extreme floods should exert a strong influence on more regular processes, promoting fluctuations between erosion-limited and transport-limited regimes.…”