STUDY ON INFLUENCE OF ROADS ON DEBRIS FLOWS DURING THE 2018 JULY HEAVY RAIN

Background/Objectives: Due to the extreme climate and the localized heavy rain, the frequency of debris flow has been increasing. Therefore, there is a growing expectation for accurate numerical analysis.Methods/Statistical analysis: We present a prediction method that can calculate the propagation length of the debris flow. This analysis indicates the relationship between the potential energy and the propagation length of the debris flow. To study the behavior of the debris flow accurately, the change in the momentum force must be considered; otherwise the calculation accuracy of the debris flow behavior is inevitably low.Findings: Entrainment is a common behavior in a debris flow that leads to changes in the momentum force. Here, we analyzed the change in the momentum force using a 2D simulation model that included entrainment. The results show how the debris flow behaves with changes in the momentum force. When entrainment is considered, the propagation length tends to be underestimated. With detailed information, the uncertainty in the prediction accuracy can be reduced.Improvements/Applications: If studies on the material properties of debris flow would be added, it will be possible to carry out various and accurate analysis of the debris flow

Download Full-text

Prediction of Precipitation in the Western Mountainous Regions of China Using a Statistical Model

Advances in Meteorology ◽

10.1155/2020/4294563 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Yijia Hu ◽

Yuan Sun ◽

Yao Ha ◽

Yimin Zhu ◽

Zhixian Luo

Keyword(s):

Statistical Model ◽

Debris Flows ◽

Summer Precipitation ◽

Heavy Rain ◽

Precipitation Anomaly ◽

Economic Losses ◽

Sample Return ◽

Mountainous Regions ◽

Landslides And Debris Flows ◽

Cross Test

During the summer in the western mountainous regions of China (WMR), the disasters such as mountain floods, landslides, and debris flows caused by heavy rain occur frequently, which often result in huge economic losses and many casualties. Therefore, it is of great significance to predict the precipitation accurately in these regions. In this paper, a statistical model is established to predict the precipitation in the WMR using the linear regression statistical method, in which the summer area-averaged precipitation anomaly in WMR is taken as the predictand and the prewinter Niño3 SST is taken as the predictor. The results of the return cross test for the historical years from 1979 to 2008 and independent sample return test from 2009 to 2018 show that this statistical model has a good performance in predicting the summer precipitation in the WMR, especially in the flood years. It has better skill in the prediction of WMR precipitation than the dynamical model SINTEX-F.

Download Full-text

Extreme geomorphic events in the contemporary evolution of forested slopes in a Central European mountain range, the Sudetes

Revista de Geomorfologie ◽

10.21094/rg.2017.017 ◽

2017 ◽

Vol 19 (1) ◽

pp. 17-28

Author(s):

MIGOŃ Piotr

Keyword(s):

Debris Flows ◽

Heavy Rain ◽

Water Erosion ◽

Surface Processes ◽

Mountain Range ◽

Strong Wind ◽

Contemporary Evolution ◽

Central European ◽

European Mountain ◽

Recurrence Intervals

Forested slopes of the Sudetes have long been implicitly considered as stable under contemporary environmental conditions, with little geomorphic change throughout the Holocene. This view is difficult to sustain and this review-type paper brings together evidence that infrequent but potent surface processes locally cause significant remodelling of slopes and regolith removal or redistribution. These processes are debris flows, shallow and deepseated landslides, episodes of efficient linear water erosion and windthrows. All are triggered by exceptional meteorological events such as heavy rain or strong wind, but additional factors of slope steepness and suitable lithology play a role. Scarce database does not permit to firmly establish recurrence intervals of such events but they seem to occur at least once per decade (within the entire mountain range) for rain-induced phenomena and two-three times per century for wind-induced phenomena.

Download Full-text

Winter Storm Conditions Leading to Excessive Runoff above California’s Oroville Dam during January and February 2017

Bulletin of the American Meteorological Society ◽

10.1175/bams-d-18-0091.1 ◽

2019 ◽

Vol 100 (1) ◽

pp. 55-70 ◽

Cited By ~ 33

Author(s):

Allen B. White ◽

Benjamin J. Moore ◽

Daniel J. Gottas ◽

Paul J. Neiman

Keyword(s):

Sierra Nevada ◽

Debris Flows ◽

Heavy Rain ◽

Heavy Precipitation ◽

Western Slope ◽

Winter Storm ◽

Atmospheric Rivers ◽

Orographic Forcing ◽

First Time ◽

Precipitation Events

AbstractDuring winter 2016/17, California experienced numerous heavy precipitation events linked to land-falling atmospheric rivers (ARs) that filled reservoirs and ended a severe, multiyear drought. These events also caused floods, mudslides, and debris flows, resulting in major socioeconomic disruptions. During 2–11 February 2017, persistent heavy precipitation in the northern Sierra Nevada culminated in a rapid increase in the water level on Lake Oroville, necessitating the activation of an emergency spillway for the first time since the Oroville Dam was installed and forcing the evacuation of 188,000 people. The precipitation, which mostly fell as rain due to elevated freezing levels, was focused on the western slope of the Sierra Nevada in connection with orographic forcing linked to two successive ARs. Heavy rain fell on saturated soils and a snowpack produced by antecedent storms and thereby resulted in excessive runoff into Lake Oroville that led to a damaged spillway and complicated reservoir operations.

Download Full-text

Wetlands in the Jiuzhaigou World Natural Heritage site of south-west China: classification and recent changes

Marine and Freshwater Research ◽

10.1071/mf17118 ◽

2018 ◽

Vol 69 (5) ◽

pp. 677 ◽

Cited By ~ 1

Author(s):

Jie Du ◽

Xue Qiao ◽

Meng Zhang ◽

Baofeng Di ◽

Ya Tang

Keyword(s):

Debris Flows ◽

Heavy Rain ◽

Storm Events ◽

Key Factors ◽

West China ◽

South West ◽

Heritage Site ◽

Increasing Trend ◽

Commercial Logging ◽

Water Nutrients

To understand the effects of tourism and climate change on wetlands, a study was performed at Jiuzhaigou, a destination receiving >5 million people per year. There are 21 types of wetlands in region, covering an area of 265.1ha, with 42.8% on tufa. Wetland areas declined by 16.1% from 1983 to 1999 (autumn) and by 31.2% from 1983 to 2002 (summer) and increased by 31.8% from 1999 to 2011 (autumn) and by 60% from 2002 to 2014 (summer). Wetland changes included dissolving tufa, a reduced tufa deposit rate, collapse of tufa mats, increases in water nutrients and algae, and marshland development. Mean annual air temperature increased from 1977. Annual precipitation varied from 430 to 810mm between 1951 and 2015, exhibiting an increasing trend from 2005 onwards. The number of both heavy rain and storm events increased from 2005. The number of tourists grew slowly from 1984 to 1997, but increased quickly from 360000 in 1998 to 5.1 million in 2015. Commercial logging between 1966 and 1978 and debris flows are probably the key factors contributing to increased lake sedimentation and marshland development. Rapid tourism development with intensive bus movement and regional air pollution likely caused changes in water chemistry, which, in turn, caused tufa changes and wetland degradation. Reducing tourist numbers is likely to be effective in reducing effects on wetlands and conserving them, but research is needed to determine appropriate tourist numbers.

Download Full-text

Assessment of the 2019 Chamoson debris flow event (Swiss Alps)

10.5194/egusphere-egu2020-15074 ◽

2020 ◽

Author(s):

Marc-Henri Derron ◽

Valérie Baumann ◽

Tiggi Choanji ◽

François Noël ◽

Ludovic Baron ◽

...

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Heavy Rain ◽

Peak Discharge ◽

Swiss Alps ◽

Mitigation Measures ◽

Size Classification ◽

Cone Apex ◽

The Right ◽

The Village

Debris flows triggered by heavy rain are common and can cause huge damages in Alpine valleys. In this case we documented the changes occurred in the Losents&#233; valley after the 11 August 2019 event, which caused two death and several damages to the village of Chamoson. The Chamoson basin is located in the Alps on the right side of the Rh&#244;ne valley. Three main rivers drain the Chamoson basin, the Losents&#233;, the Cry and the Tsen&#233;. The main debris flow event occurred in the Losents&#233; sub-basin. The Losents&#233; River is 9 km long from the sources at 3000 m until the alluvial cone apex at 600 m. In the upper part of the Chamoson basin thick loose debris cones and glacial deposits lie on steep slopes, the geology of the middle basin is formed by unstable clayey shales with several active landslides on both lateral valley slopes.The village of Chamoson is located on the huge alluvial cone built with torrential events from the three main rivers. Since the XIX century, several big debris flow events (1898, 1923, 2003, 2018) were recorded in this area and mitigation measures were built in the principal rivers. Unfortunately, the 2019 debris flows overflowed the channels limit when the flows reached the alluvial cone apex, reaching the road and took a car with 2 persons inside. Upstream in the middle basin 2 wood bridges were destroyed and many concrete or stone walls (mitigation measures) along the river were damaged.After the event we acquired pictures with a drone from the sources area and the Losents&#233; river valley in order to have a post event image. With this image we could analyse and map the source areas and the inundated areas in the Losents&#233; channel. We did also field observation along the river.After comparing the pre- and post-event images we mapped the middle and upper basin inundated areas by the 2019 event and the described the deposits and eroded sections along the river. We calculated the peak discharge of 1000 m3/s for this event using the inundated transversal profile area near the cone apex and the flow velocity obtained from a movie. The peak discharge corresponds to 4 in the size classification for debris flows (Jacob et al., 2005).Reference:Jakob, M. (2005). A size classification for debris flows.&#160;Engineering geology,&#160;79(3-4), 151-161.

Download Full-text

Landslides and debris flows on the slopes at Aso Caldera induced by heavy rain event in northern Kyushu on July 2012

Journal of the Japan Landslide Society ◽

10.3313/jls.49.290 ◽

2012 ◽

Vol 49 (5) ◽

pp. 290-291

Author(s):

Shiho ASANO

Keyword(s):

Debris Flows ◽

Heavy Rain ◽

Rain Event ◽

Heavy Rain Event ◽

Aso Caldera ◽

Landslides And Debris Flows

Download Full-text

Settlement Isolation Susceptibility due to Heavy Rain Caused Road Closure

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.723.656 ◽

2013 ◽

Vol 723 ◽

pp. 656-663

Author(s):

Shu Rong Yang

Keyword(s):

River Basin ◽

Debris Flows ◽

Heavy Rain ◽

Transportation Infrastructure ◽

Public Administrators ◽

Typhoon Morakot ◽

Loss Of Life ◽

Southern Taiwan ◽

Road Closure ◽

Landslides And Debris Flows

On August 9, 2009, Typhoon Morakot struck Taiwan, triggering landslides and debris flows and destroying transportation infrastructure in the southern mountains. Many settlements in this area were isolated due to road closure. Residents were trapped in the settlements and unable to evacuate to safe places. Also, emergency goods were unable to be transported to the settlements. In order to minimize the loss of life and property associated with future typhoon, public administrators should evacuate residents before access routes to settlements are affected.In this study, settlements in Lao-Nong River basin of Southern Taiwan were ranked in accordance to isolation susceptibility. Susceptibility was estimated by overlaying maps of landslides, debris flows, temporary roads and primary mountain road layers. Criteria used to evaluate the isolation susceptibility were developed using an expert-based approach. The isolation susceptibilities of settlements were categorized into 3 levels, namely high, moderate and low.

Download Full-text