scholarly journals Landslide-lake outburst floods accelerate downstream hillslope slippage

2021 ◽  
Vol 9 (5) ◽  
pp. 1251-1262
Author(s):  
Wentao Yang ◽  
Jian Fang ◽  
Jing Liu-Zeng
Keyword(s):  
River Channel ◽  
Disaster Mitigation ◽  
River Channels ◽  
Jinsha River ◽  
Mountainous Regions ◽  
Deformation Response ◽  
Outburst Floods ◽  
Dynamic Channel ◽  
Landslide Lake ◽  
Sentinel 2

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.

scholarly journals Landslide-lake outburst floods accelerate downstream slope slippage

2021 ◽  
Author(s):  
Wentao Yang ◽  
Jian Fang ◽  
Jing Liu-Zeng
Keyword(s):  
River Channel ◽  
Disaster Mitigation ◽  
Jinsha River ◽  
Mountainous Regions ◽  
Deformation Response ◽  
Outburst Floods ◽  
Dynamic Channel ◽  
One Year ◽  
Landslide Lake ◽  
Sentinel 2

Abstract. The Jinsha River, carving 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 LLFs' impacts on downstream river channel 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 one year after the floods. Extensive undercuts by the floods probably removed hillslope buttresses and triggered deformation response, suggesting a 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.

scholarly journals Timing of exotic, far-travelled boulder emplacement and paleo-outburst flooding in the central Himalaya

2020 ◽  
Author(s):  
Marius L. Huber ◽  
Maarten Lupker ◽  
Sean F. Gallen ◽  
Marcus Christl ◽  
Ananta P. Gajurel
Keyword(s):  
Landscape Evolution ◽  
Hydraulic Geometry ◽  
River Channels ◽  
Mountainous Regions ◽  
Exposure Dating ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Himalayan Rivers ◽  
Active Channels ◽  
Exposure Ages

Abstract. Large boulders, ca. 10 m in diameter or more, commonly linger Himalayan river channels. In many cases, their lithology is only compatible with source areas located > 10 km upstream suggesting long transport distances. The mechanisms and timing of exotic boulder emplacement are poorly constrained, but their presence hints at processes that are significant for landscape evolution and geohazard assessments in mountainous regions. We surveyed river reaches of the Trishuli and Sunkoshi, two trans-Himalayan rivers in central Nepal to improve understanding of the processes responsible for exotic boulder transport and the timing of emplacement. Boulder size and channel hydraulic geometry were used to constrain paleo-discharges and boulder emplacement ages were determined using cosmogenic nuclide exposure dating. Modelled discharges required for boulder transport, of ca. 103 to 105 m3/s, exceed typical monsoonal floods in these river reaches. Exposure ages range between ca. 1.5 and 13.5 kyrs BP with clustering of ages around 4.5–5 kyrs BP in both studied valleys. This later period is coeval with a broader weakening of the Indian summer monsoon and glacial retreat after the Early Holocene Climatic Optimum (EHCO), suggesting Glacial Lake Outburst Floods (GLOFs) as a possible cause for boulder transport. We, therefore, propose that these exceptional events are climate-driven, but counter-intuitively occur in the wake of transitions to drier and warmer climates leading to glacier retreat rather than during wetter periods. Furthermore, the old ages and prolonged preservation of these large boulders in or near the active channels shows that these infrequent events have long-lasting consequences on valley bottoms and channel morphology. Overall this study sheds light on the possible coupling between large-infrequent events and bedrock incision patterns in Himalayan rivers with broader implications on landscape evolution.

scholarly journals Timing of exotic, far-traveled boulder emplacement and paleo-outburst flooding in the central Himalayas

2020 ◽  
Vol 8 (3) ◽  
pp. 769-787
Author(s):  
Marius L. Huber ◽  
Maarten Lupker ◽  
Sean F. Gallen ◽  
Marcus Christl ◽  
Ananta P. Gajurel
Keyword(s):  
Landscape Evolution ◽  
Hydraulic Geometry ◽  
River Channels ◽  
Mountainous Regions ◽  
Exposure Dating ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Himalayan Rivers ◽  
Active Channels ◽  
Exposure Ages

Abstract. Large boulders, ca. 10 m in diameter or more, commonly linger in Himalayan river channels. In many cases, their lithology is consistent with source areas located more than 10 km upstream, suggesting long transport distances. The mechanisms and timing of “exotic” boulder emplacement are poorly constrained, but their presence hints at processes that are relevant for landscape evolution and geohazard assessments in mountainous regions. We surveyed river reaches of the Trishuli and Sunkoshi, two trans-Himalayan rivers in central Nepal, to improve our understanding of the processes responsible for exotic boulder transport and the timing of emplacement. Boulder size and channel hydraulic geometry were used to constrain paleo-flood discharge assuming turbulent, Newtonian fluid flow conditions, and boulder exposure ages were determined using cosmogenic nuclide exposure dating. Modeled discharges required for boulder transport of ca. 103 to 105 m3 s−1 exceed typical monsoonal floods in these river reaches. Exposure ages range between ca. 1.5 and 13.5 ka with a clustering of ages around 4.5 and 5.5 ka in both studied valleys. This later period is coeval with a broader weakening of the Indian summer monsoon and glacial retreat after the Early Holocene Climatic Optimum (EHCO), suggesting glacial lake outburst floods (GLOFs) as a possible cause for boulder transport. We, therefore, propose that exceptional outburst events in the central Himalayan range could be modulated by climate and occur in the wake of transitions to drier climates leading to glacier retreat rather than during wetter periods. Furthermore, the old ages and prolonged preservation of these large boulders in or near the active channels shows that these infrequent events have long-lasting consequences on valley bottoms and channel morphology. Overall, this study sheds light on the possible coupling between large and infrequent events and bedrock incision patterns in Himalayan rivers with broader implications for landscape evolution.

scholarly journals Mapping Outburst Floods Using a Collaborative Learning Method Based on Temporally Dense Optical and SAR Data: A Case Study with the Baige Landslide Dam on the Jinsha River, Tibet

2021 ◽  
Vol 13 (11) ◽  
pp. 2205
Author(s):  
Zhongkang Yang ◽  
Jinbing Wei ◽  
Jianhui Deng ◽  
Yunjian Gao ◽  
Siyuan Zhao ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Landslide Dam ◽  
Flood Mapping ◽  
Outburst Flood ◽  
Backscattering Coefficient ◽  
Sar Images ◽  
Jinsha River ◽  
Outburst Floods ◽  
Sar Data ◽  
Sentinel 2

Outburst floods resulting from giant landslide dams can cause devastating damage to hundreds or thousands of kilometres of a river. Accurate and timely delineation of flood inundated areas is essential for disaster assessment and mitigation. There have been significant advances in flood mapping using remote sensing images in recent years, but little attention has been devoted to outburst flood mapping. The short-duration nature of these events and observation constraints from cloud cover have significantly challenged outburst flood mapping. This study used the outburst flood of the Baige landslide dam on the Jinsha River on 3 November 2018 as an example to propose a new flood mapping method that combines optical images from Sentinel-2, synthetic aperture radar (SAR) images from Sentinel-1 and a Digital Elevation Model (DEM). First, in the cloud-free region, a comparison of four spectral indexes calculated from time series of Sentinel-2 images indicated that the normalized difference vegetation index (NDVI) with the threshold of 0.15 provided the best separation flooded area. Subsequently, in the cloud-covered region, an analysis of dual-polarization RGB false color composites images and backscattering coefficient differences of Sentinel-1 SAR data were found an apparent response to ground roughness’s changes caused by the flood. We carried out the flood range prediction model based on the random forest algorithm. Training samples consisted of 13 feature vectors obtained from the Hue-Saturation-Value color space, backscattering coefficient differences/ratio, DEM data, and a label set from the flood range prepared from Sentinel-2 images. Finally, a field investigation and confusion matrix tested the prediction accuracy of the end-of-flood map. The overall accuracy and Kappa coefficient were 92.3%, 0.89 respectively. The full extent of the outburst floods was successfully obtained within five days of its occurrence. The multi-source data merging framework and the massive sample preparation method with SAR images proposed in this paper, provide a practical demonstration for similar machine learning applications using remote sensing.

scholarly journals Numerical Simulation of Effects of River Reconstruction on Flooding: A Case Study of the Ba River, China

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Haixiao Jing ◽  
Yongbiao Lang ◽  
Xinhong Wang ◽  
Mingyang Yang ◽  
Zongxiao Zhang
Keyword(s):  
Flow Velocity ◽  
Eddy Currents ◽  
Human Life ◽  
River Channel ◽  
Computational Domain ◽  
River Channels ◽  
One Dimensional ◽  
Local Reconstruction ◽  
Before And After ◽  
Flood Flow

The local reconstruction of river channels may pose obstacles of flood flow, local eddy currents, or high flow velocity which pose potential threats to human life and infrastructures nearby. In the design of such projects, the effects of local reconstruction of the river channel on flooding are often evaluated by the one-dimensional method, which is based on the formula of one-dimensional nonuniform flow. In this study, a two-dimensional hydrodynamic model based on shallow water equations is employed to investigate the impacts of river reconstruction on flooding in the Ba River, China. The finite volume method and an unstructured triangular mesh are used to solve the governing equations numerically. The numerical model is validated by comparison with the results of a physical model of 1 : 120 scale. The backwater effects and impacts of flood flow fields under two flood frequencies are analyzed by comparing the numerical results before and after local reconstruction. The results show that the backwater length under both 10-year and 100-year floods can be reached up to the upstream boundary of the computational domain. However, the maximum water level rises are limited, and the levees in this river channel are safe enough. The flow velocity fields under both floods are changed obviously after local reconstruction in the Ba River. Areas with the potential for scour and deposition of the river bed are also pointed out. The findings of this study are helpful for the evaluation of flood risks of the river.

scholarly journals An Improved Method Constructing 3D River Channel for Flood Modeling

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 403 ◽  
Author(s):  
Pengbo Hu ◽  
Jingming Hou ◽  
Zaixing Zhi ◽  
Bingyao Li ◽  
Kaihua Guo
Keyword(s):  
High Resolution ◽  
River Channel ◽  
Hydrodynamic Process ◽  
River Channels ◽  
Section Data ◽  
Terrain Model ◽  
Digital Elevation ◽  
Hydrodynamic Processes ◽  
Hermite Spline ◽  
Elevation Model

The high-resolution topography is very crucial to investigate the hydrological and hydrodynamic process. To resolve the deficiency problem of high resolution terrain data in rivers, the Quartic Hermite Spline with Parameter (QHSP) method constructing the river channel terrain based on the limited cross-section data is presented. The proposed method is able to not only improve the reliability of the constructed river terrain, but also avoid the numerical oscillations caused by the existing constructing approach, e.g., the Cubic Hermite Spline (CHS) method. The performance of the proposed QHSP method is validated against two benchmark tests. Comparing the constructed river terrains, the QHSP method can improve the accuracy by at least 15%. For the simulated flood process, the QHSP method could reproduce more acceptable modeling results as well, e.g., in Wangmaogou catchment, the numerical model applying the Digital Elevation Model (DEM) produced by the QHSP method could increase the reliability by 18.5% higher than that of CHS method. It is indicated that the QHSP method is more reliable for river terrain model construction than the CHS and is a more reasonable tool investigating the hydrodynamic processes in river channels lacking of high resolution topography data.

scholarly journals Correction to: Using Sentinel-2 time series to detect slope movement before the Jinsha River landslide

Landslides ◽  
2019 ◽  
Vol 16 (7) ◽  
pp. 1325-1326
Author(s):  
Wentao Yang ◽  
Yunqi Wang ◽  
Shao Sun ◽  
Yujie Wang ◽  
Chao Ma
Keyword(s):  
Time Series ◽  
Slope Movement ◽  
Jinsha River ◽  
Sentinel 2

Sediment origins across the terrestrial-aquatic continuum: climate threat mitigation and promotion of water quality

2020 ◽  
Author(s):  
Katy Wiltshire ◽  
Toby Waine ◽  
Bob Grabowski ◽  
Miriam Glendell ◽  
Steve Addy ◽  
...  
Keyword(s):  
Water Quality ◽  
Soil Erosion ◽  
Soil Loss ◽  
River Channel ◽  
River Channels ◽  
Catchment Scale ◽  
Transport Pathways ◽  
Fine Grained ◽  
Erosion Rates ◽  
Erosion Modelling

<p>Although fine-grained sediment (FGS) is a natural component of river systems, increased fluxes can impact FGS levels to such an extent they cause detrimental, irreversible changes in the way rivers function intensifying flood risk and negatively affecting water quality.</p><p>Previous catchment scale studies indicate there is no simple link between areas of sediment loss and the organic carbon (OC) load in waterways; areas with a high soil loss rate may not contribute most sediment to the rivers and areas that contribute the most sediment may not contribute the most OC. Anthropogenic and climate changes can accelerate soil erosion and the role of soil OC transported by erosional processes in the fluxes of C between land, water and atmosphere is still debated. Tracing sediment pathways, likely depositional areas and connections to streams leads to better assumptions about control processes and better estimation of OC fluxes.</p><p>In this innovative study OC fingerprinting of sediment reaching a catchment’s waterbodies is combined with OC stock and erosion modelling of the terrestrial catchment. Initial results show disconnect between catchment OC loss erosion modelling and fingerprinting results, which could be due to failure to model connectivity between the land and river channel. The current soil erosion model RUSLE (Revised Universal Soil Loss Equation) calculates only the spatial pattern of mean annual soil erosion rates. Using the WaTEM SEDEM model, which in includes routing (and possible en route deposition) of eroded sediments to river channels, we aim to determine the dominant source of OC within catchment streams by identification of both the land-use specific areas with the highest OC loss and the transport pathways between the sources and river channel.</p>

Recent catastrophic landslide lake outburst floods in the Himalayan mountain range

2016 ◽  
Vol 41 (1) ◽  
pp. 3-28 ◽  
Author(s):  
Virginia Ruiz-Villanueva ◽  
Simon Allen ◽  
Manohar Arora ◽  
Narendra K Goel ◽  
Markus Stoffel
Keyword(s):  
Large Scale ◽  
Drainage System ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Remotely Sensed Data ◽  
Discharge Data ◽  
Outburst Floods ◽  
High Resolution Satellite Images ◽  
Hydrometeorological Conditions ◽  
Landslide Lake

Among the more complex and devastating interactions between climate and hydromorphological processes in mountain environments are landslide lake outburst floods (LLOFs), resulting from mass movements temporarily blocking a drainage system. This work reviews these processes in the Himalayas and highlights the high frequency of this type of phenomenon in the region. In addition, we analyse two recent catastrophic trans-national LLOFs occurring in the Sutlej river basin during 2000 and 2005. Based on high resolution satellite images, Tropical Rainfall Measuring Mission (TRMM), Moderate-Resolution Imaging Spectroradiometer (MODIS) derived evolution of snowline elevation and discharge data we reconstruct the timing and hydrometeorological conditions related to the formation and failure of landslide dams. Results showed that the 2005 flood, originating from the outburst of the Parchu Lake, was not related to heavy precipitation, but was likely enhanced by the rapid and late snowmelt of an unusually deep and widespread snowpack. The flood in 2000 was triggered by the outburst of an unnamed lake located on the Tibetan plateau, identified here for the first time. In this case, the outburst followed intense precipitation in the lake watershed, which raised the level of the lake and thus caused the breaching of the dam. As stream gauges were damaged during the events detailed discharge data is not available, but we estimated the peak discharges ranging between 1100 m3 s−1 and 2000 m3 s−1 in 2005, and 1024 m3 s−1 and 1800 m3 s−1 in 2000. These events caused significant geomorphic changes along the river valleys, with observed changes in channel width exceeding 200 m. Results also demonstrate that remotely-sensed data enables valuable large-scale monitoring of lake development and related hydrometeorological conditions, and may thereby inform early warning strategies, and provide a basis for flood risk reduction measures that focus on disaster preparedness and response strategies.

scholarly journals Central Himalayan rivers record the topographic signature of erosion by glacial lake outburst floods

2021 ◽  
Author(s):  
Maxwell P. Dahlquist ◽  
A. Joshua West
Keyword(s):  
Regional Scale ◽  
Glacial Lake ◽  
River Channels ◽  
Nepal Himalaya ◽  
River Incision ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Bedrock Erosion ◽  
River Valleys ◽  
Future Work

Abstract. In steep landscapes, river incision sets the pace of landscape evolution. Transport of coarse sediment controls incision by evacuating material delivered to river channels by landslides. However, large landslide-derived boulders that impede bedrock erosion are immobile even in major runoff-driven floods. Glacial lake outburst floods (GLOFs) mobilize these boulders and drive incision, yet their role in regional-scale erosion is poorly understood, largely because of their rarity. Here, we find a topographic signature consistent with widespread GLOF erosion in the Nepal Himalaya. In rivers with glaciated headwaters that generate GLOFs, valleys stay narrow and relatively free of sediment, with bedrock often exposed to erosion. In turn, tributaries to these valleys are steep, allowing less efficient erosional regimes to keep pace with GLOF-driven incision. Where GLOFs are less frequent, valleys are more alluviated and incision stalls. Our results suggest the extent of headwater glaciation may play an important role in erosion of Himalayan river valleys and deserves more attention in future work.

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