Landslide Susceptibility Based on Extreme Rainfall-Induced Landslide Inventories and the Following Landslide Evolution

Landslide susceptibility assessment is crucial for mitigating and preventing landslide disasters. Most landslide susceptibility studies have focused on creating landslide susceptibility models for specific rainfall or earthquake events, but landslide susceptibility in the years after specific events are also valuable for further discussion, especially after extreme rainfall events. This research provides a new method to draw an annual landslide susceptibility map in the 5 years after Typhoon Morakot (2009) in the Chishan River watershed in Taiwan. This research establishes four landslide susceptibility models by using four methods and 12 landslide-related factors and selects the model with the optimum performance. This research analyzes landslide evolution in the 5 years after Typhoon Morakot and estimates the average landslide area different ratio (LAD) in upstream, midstream, and downstream of the Chishan River watershed. We combine landslide susceptibility with the model with the highest performance and average annual LAD to draw an annual landslide susceptibility map, and its mean correct ratio ranges from 62.5% to 73.8%.

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Drawing the landslide susceptibility maps based on long term evolution of extreme rainfall-induced landslide

10.5194/egusphere-egu2020-8361 ◽

2020 ◽

Author(s):

Chunhung Wu

Keyword(s):

Landslide Susceptibility ◽

Extreme Rainfall ◽

Landslide Inventory ◽

Landslide Area ◽

Typhoon Morakot ◽

Extreme Rainfall Events ◽

Susceptibility Maps ◽

Susceptibility Model ◽

Landslide Ratio ◽

Landslide Susceptibility Maps

This research is concerned with the prediction accuracy and applicability of statistical landslide susceptibility model to the areas with dense landslide distribution caused by extreme rainfall events and how to draw the annual landslide susceptibility maps after the extreme rainfall events. The landslide induced by 2009 Typhoon Morakot, i.e. an extreme rainfall event, in the Chishan river watershed is dense distributed. We compare the annual landslide inventories in the following 5 years after 2009 Typhoon Morakot and finds the similarity of landslide distribution.The landslide distributions from 2008 to 2014 are concentrated in the midstream and upstream watersheds. The landslide counts and area in 2009 are 3.4 times and 7.4 times larger than those in 2008 due to 2009 Typhoon Morakot. The landslide counts and area in 2014 are only 69.8% and 53.4 % of those in 2009. The landslide area from 2010 to 2014 shows that the landslide area in the following years after 2009 Typhoon Morakot gradually decreases if without any heavy rainfall event with more accumulated rainfall than that during 2009 Typhoon Morakot.The landslide ratio in the upstream watershed in 2008 is 1.37%, and that from 2009 to 2014 are over 3.51%. The landslide ratio in the upstream watershed in 2014 is 1.17 times larger than that in 2009. On average, the landslide inventory from 2010 to 2014 in the upstream watershed is composed of 60.1 % old landslide originated from 2009 Typhoon Morakot and 39.9 % new landslide.The landslide ratio in the midstream watershed reaches peak (9.19%) in 2009 and decreases gradually to 2.56 % in 2014. The landslide ratio in 2014 in the midstream watershed is only 27.9% of that in 2009, and that means around 72.1 % of landslide area in 2009 in the midstream watershed has recovered. On average, the landslide inventory from 2010 to 2014 in the midstream watershed is composed of 76.1 % old landslide originated from 2009 Typhoon Morakot and 23.9 % new landslide.The research uses the landslide area in 2009 and 2014 in the same subareas to calculate the expanding or contracting ratio of landslide area. The contracting ratio of riverbank and non-riverbank landslide area in the midstream watershed are 0.760 and 0.788, while that in the downstream watershed are 0.732 and 0.789. The expanding ratio of riverbank and non-riverbank landslide area in the upstream watershed are 1.04 and 1.02.The annual landslide susceptibility in each subarea in the Chishan river watershed in a specific year from 2010 to 2014 is the production of landslide susceptibility in 2009 and the contraction or expanding ratio to the Nth power, and the N number is how many years between 2009 and the specific year. We adopt the above-mentioned equation and the landslide susceptibility model based on the landslide inventory after 2009 Typhoon Morakot to draw the annual landslide susceptibility maps in 2010 to 2014. The mean correct ratio value of landslide susceptibility model in 2009 is 70.9%, and that from 2010 to 2014 are 62.5% to 73.8%.

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Producing landslide susceptibility maps by applying expert knowledge in a GIS - based environment.

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.10993 ◽

2016 ◽

Vol 47 (3) ◽

pp. 1539 ◽

Cited By ~ 2

Author(s):

P. Tsangaratos ◽

D. Rozos

Keyword(s):

Landslide Susceptibility ◽

Assessment Tool ◽

Expert Knowledge ◽

Visual Basic ◽

Susceptibility Map ◽

Engineering Systems ◽

Landslide Susceptibility Map ◽

Related Factors ◽

Susceptibility Maps ◽

Analytic Hierarchical Process

In this paper two semi - quantative approaches, from the domain of Multi criteria decision analysis, such as Rock Engineering Systems (RES) and Analytic Hierarchical Process (AHP) are implemented for weighting and ranking landslide related factors in an objective manner. Through the use of GIS these approaches provide a highly accurate landslide susceptibility map. For this purpose and in order to automate the process, the Expert Knowledge for Landslide Assessment Tool (EKLATool) was developed as an extension tightly integrated in the ArcMap environment, using ArcObjects and Visual Basic script codes. The EKLATool was implemented in an area of Xanthi Prefecture, Greece, where a spatial database of landslide incidence was available

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Spatiotemporal Hotspots and Decadal Evolution of Extreme Rainfall-Induced Landslides: Case Studies in Southern Taiwan

Water ◽

10.3390/w13152090 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2090

Author(s):

Chunhung Wu ◽

Chengyi Lin

Keyword(s):

Hot Spot ◽

Recovery Period ◽

Extreme Rainfall ◽

Bank Erosion ◽

Typhoon Morakot ◽

River Watershed ◽

Sediment Yields ◽

Landslide Evolution ◽

Southern Taiwan ◽

Landslide Ratio

The 2009 Typhoon Morakot triggered numerous landslides in southern Taiwan, and the landslide ratios in the Ailiao and Tamali river watershed were 7.6% and 10.7%, respectively. The sediment yields from the numerous landslides that were deposited in the gullies and narrow reaches upstream of Ailiao and Tamali river watersheds dominated the landslide recovery and evolution from 2010 to 2015. Rainfall records and annual landslide inventories from 2005 to 2015 were used to analyze the landslide evolution and identify the landslide hotspots. The landslide recovery time in the Ailiao and Tamali river watershed after 2009 Typhoon Morakot was estimated as 5 years after 2009 Typhoon Morakot. The landslide was easily induced, enlarged, or difficult to recover during the oscillating period, particularly in the sub-watersheds, with a landslide ratio > 4.4%. The return period threshold of rainfall-induced landslides during the landslide recovery period was <2 years, and the landslide types of the new or enlarged landslide were the bank-erosion landslide, headwater landslide, and the reoccurrence of old landslide. The landslide hotspot areas in the Ailiao and Tamali river watershed were 2.67–2.88 times larger after the 2009 Typhoon Morakot using the emerging hot spot analysis, and most of the new or enlarged landslide cases were identified into the oscillating or sporadic or consecutive landslide hotspots. The results can contribute to developing strategies of watershed management in watersheds with a dense landslide.

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Landslides and human interference in Darjiling Himalayas, India

Revista de Geomorfologie ◽

10.21094/rg.2017.014 ◽

2017 ◽

Vol 19 (1) ◽

pp. 44-57

Author(s):

Sunil Kumar DE

Keyword(s):

Extreme Rainfall ◽

Susceptibility Map ◽

Human Intervention ◽

Landslide Susceptibility Map ◽

Extreme Rainfall Events ◽

Rainfall Events ◽

Human Interference ◽

Mining Sites ◽

Construction Procedure ◽

Over Time

Landslides are among the nature's primarily ways of adjustment to slope stability. In Darjiling Himalayas the process has been intensified by human interference mainly through rapid deforestation, incorrect construction procedure and unplanned tapping of natural resources. The present paper aims at investigating the occurrence of landslides mainly due to human intervention. For analyzing the acuteness of the problem, important events of landslides over time, landslide susceptibility map using traditional check-list and investigation of the nature of human intervention for landslide occurrences have been carried out. From the study it is found that extreme rainfall events of consecutive days accumulating an amount of 1000 to 1200 mm, coupled with deep weathering in susceptible structure could trigger to 5 to 10 m-thick landslides. Being saturated with percolating rainwater, such slopes even with a rainfall 50 of mm/h would cause disastrous landsllides. Common occurrence of landslides is found along the springs, where thick debris is removed along the slope, ontop of the bedrock.. Generally deforested urbanized tracts, illegal coal mining sites, tea gardens, artillery roads connecting hills with the plains are the most susceptible areas to sliding.

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Predictive analysis of landslide susceptibility in the Kao-Ping watershed, Taiwan under climate change conditions

Natural Hazards and Earth System Sciences Discussions ◽

10.5194/nhessd-3-575-2015 ◽

2015 ◽

Vol 3 (1) ◽

pp. 575-606 ◽

Cited By ~ 2

Author(s):

K. J. Shou ◽

C. C. Wu ◽

J. F. Lin

Keyword(s):

Landslide Susceptibility ◽

General Circulation ◽

Circulation Model ◽

Extreme Rainfall ◽

Extreme Rainfall Events ◽

Climate Conditions ◽

River Watershed ◽

Rainfall Frequency ◽

Critical Issues ◽

Susceptibility Model

Abstract. Among the most critical issues, climatic abnormalities caused by global warming also affect Taiwan significantly for the past decade. The increasing frequency of extreme rainfall events, in which concentrated and intensive rainfalls generally cause geohazards including landslides and debris flows. The extraordinary Typhoon Morakot hit Southern Taiwan on 8 August 2009 and induced serious flooding and landslides. In this study, the Kao-Ping River watershed was adopted as the study area, and the typical events 2007 Krosa Typhoon and 2009 Morakot Typhoon were adopted to train the susceptibility model. This study employs rainfall frequency analysis together with the atmospheric general circulation model (AGCM) downscaling estimation to understand the temporal rainfall trends, distributions, and intensities in the Kao-Ping River watershed. The rainfall estimates were introduced in the landslide susceptibility model to produce the predictive landslide susceptibility for various rainfall scenarios, including abnormal climate conditions. These results can be used for hazard remediation, mitigation, and prevention plans for the Kao-Ping River watershed.

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