A new approach to temporal modelling for landslide hazard assessment using an extreme rainfall induced-landslide index

Nedumpallile Vasu, N.,Lee, S.R.,Pradhan, A.M.S.,Kim, Y.T.,Kang, S.H.,Lee, D.H. Elsevier Pub. Co 2016 Engineering geology Vol.215 No.-

An ever-increasing trend of extreme rainfall events in South Korea due to climate change is causing shallow landslides and shallow landslide induced debris flows in the mountains that cover 70% of the total land area of the nation. These catastrophic, gravity-driven processes cost the government several billion won in losses, and attendant fatalities, every year. The most common type of landslide observed is the shallow landslide occurring at 1-3m depth, which may mobilize into a catastrophic debris flow. A landslide early warning system encompassing different scale-based stages is used to predict potential areas for both the landslide types. Current study focusing on the first stage landslide hazard assessment at regional or medium scale requires the development of spatially evolving landslide hazard maps for both types of landslides based on the real-time rainfall. However, lack of complete landslide inventory data motivates the development of temporal and spatial models as independent components of the landslide hazard. Most of the existing temporal assessment schemes traditionally rooted in recurrence-based concepts does not consider soil factors and are not suitable to be incorporated in to the landslide early warning system since real-time rainfall cannot be considered. This motivated the development of a new probabilistic temporal model termed the extreme rainfall-induced landslide index. The probabilistic index was developed in Gangwon Province through a logistic regression using four factors; namely, continuous rainfall, 20-days antecedent rainfall, saturated hydraulic conductivity, and storage capacity. The developed model exhibited high area under the curve (AUC) values of 82% and 91% obtained for the training and validation curves, exhibiting good performance of the statistical index. Also, a high performance susceptibility model (training and validation AUC values of 96% and 94%, respectively) was developed using a logistic regression analysis, for Deokjeok-ri Creek, located in Gangwon province. Assuming the independence of the hazard components, a dynamic hazard index (DHI) was established through a joint probability of both the well validated models. The DHI was used to study the evolution of landslide hazard for the July 2006 extreme rainfall-induced landslide events in Deokjeok-ri Creek.

Assessment and Applicability Analysis of Dynamic Landslide Hazard Using Matrix Approach

Ki Dae Kim,Min Jeng Kang,Chang Woo Lee,Choong Shik Woo,Jun Pyo Seo 위기관리 이론과 실천 2020 Crisisonomy Vol.16 No.9

산사태 발생시점 및 지점을 예측하기 위한 연구는 서로 다른 목적과 범위로 구성되었지만 상호보완적인 역할을 한다. 따라서 이 연구에서는 산림청에서 구축한 산사태 예보체계와 산사태위험지도의 활용성을 높이고자 정적 산사태위험도를 동적 산사태위험도로 변환하고, 이를 평가하기 위해 시공간적 위험도의 매트릭스 결합을 수행하였다. 2017년 산사태 발생지인 충청남도 천안시의 시나리오 및 실제 산사태 발생시점을 대상으로 다양한 매트릭스 평가모형을 적용한 결과, 간단한 행렬 조합만으로 동적 산사태위험도의 정량적 평가를 가능케 하였으며, 정확도 또한 기존의 산사태위험지도에 비해 높게 나타났다. 또한 산림청에서 제공하는 1시간 이후의 산사태 예측정보와 결합을 통해 단기적인 미래의 동적 산사태위험도를 평가할 수 있는 점에 의의가 있다. 이 연구결과는 기구축된 국가산사태 예보체계와 산사태위험지도의 활용성을 극대화함과 동시에 우기 시의 산사태위험지 관리효율성 향상에 기여할 수 있을 것이다. The models to predict when and where a landslide occurs were constructed with different purposes and scopes, but tended to be complementary to each other. The objective of this study was to convert the static landslide hazard into the dynamic landslide hazard and combine a spatiotemporal hazard matrix to assess it, in order to enhance the usability of the early warning system for landslide and the landslide hazard map developed by the Korea Forest Service. We applied various matrix evaluation models to develop scenarios and assess the 2017 landslide occurred in Cheonan, Korea. The results of this study showed that a simple combination of matrices facilitated quantitative evaluation of the dynamic landslide hazard and its accuracy was higher than the static landslide hazard map. In addition, the dynamic landslide hazard can be assessed for the near future by integrating the 1-hour prediction data provided by the Korea Forest Service. The results of this study can help maximize the utilization of the existing national landslide forecast system and landslide hazard map, which should enhance the efficiency of managing landslide-prone zones during the rainy season.

한국의 산사태취약지역과 사방지의 환경요인 분석

박수진,주우영,이수연 국토지리학회 2015 국토지리학회지 Vol.49 No.2

This study aims at comprehending the relation between landslide hazard and environmental factors by analyzing spatial distribution of landslide hazard zone and erosion control area of Korea. Landslide hazard zone is the area appointed as a potential landslide hazard zone, and erosion control area is the area which is reinforced after landslide. 25 types of environmental data which predict landslide hazard are collected based on 5 critical factors: landuse, climate, landform, soil, distance from road and river. Erosion control area shows high ratio in the area where land is frequently used, while it shows low ratio in the area with low accessibility. The reason of low ratio of erosion control area in the area with low accessibility is because it costs relatively low if landslide occurs in mountainous area. Landuse > Soil type > Landform are the most important three factors determining landslide hazard zone. Landuse > Landform > Soil type are the most important three factors of erosion control area. Additional analysis in regional scale is needed as environmental factors show big difference by region and have nonlinearity in complex interactions. 이 연구는 전국 산사태취약지역과 사방지의 분포를 비교분석하여 산사태의 위험과 환경요인과의 관련성을 분석하는 것이 목적이다. 환경요인은 토지이용, 기후, 지형, 토양, 도로 및 하천요인으로 구분하였다. 다양한 환경요인들과의 비교에서 산사태취약지역과 실제 산사태가 발생한 후 이루어지는 사방공사지역간에는 상당한 불일치가 나타나는 것을 확인할 수 있었다. 이것은 토지이용이 활발한 곳을 중심으로 사방지가 우선적으로 조성되는 것이 주원인이지만, 산사태에 취약한 환경요인들에 대한 인식차이가 존재하며 그 결과 산사태취약지들이 효과적으로 관리되지 못하고 있다는 것을 의미한다. 범주형주성분 분석 결과 산사태취약지역의 경우 토지이용요인 > 토양요인 > 지형요인이, 사방지의 경우 토지이용요인 > 지형요인 > 토양요인이 가장 중요한 환경요인들이었다. 환경요인은 지역별로 큰 차이를 보이며 상호작용 시 비선형성을 보여 효과적인 산사태 방재를 위해서 지역차원의 추가적인 분석이 필요하다.

산사태예측도에 의한 석조문화재 주변의 산사태재해 가능성 분석

김경수 ( Kyeong Su Kim ),이춘오 ( Choon Oh Lee ),송영석 ( Young Suk Song ),조용찬 ( Yong Chan Cho ),김만일 ( Man Il Kim ),채병곤 ( Byung Gon Chae ) 대한지질공학회 2007 지질공학 Vol.17 No.3

산사태가 일어날 지점을 예측한다든지 사태물질로 인한 피해 예상지역을 알아내는 것은 쉬운 일이 아니다. 이는 산사태를 발생시키는 요인들이 여러가지가 있고 개개의 요인들이 산사태를 발생시키는데 기여하는 중요도도 서로 다르기 때문이다. 그러나 많은 산사태자료에 대한 분석을 바탕으로 발생 메커니즘 규명과 통계적 해석기법을 통해 산사태 발생가능성의 예측과 위험지역의 분류가 가능해졌다. 석조문화재가 산사면 또는 그 직하부에 인접해 있는 경우는 산사태가 발생되면 재해에 무방비로 노출되어 있다. 이 연구에서는 여름철의 집중호우 등에 의해 석조문화재 및 그 주변지역에 산사태가 발생할 가능성을 사전에 예측함으로써 그로 인한 석조문화재의 피해가능성을 분석하고자 하였다. 이러한 목적을 위해 2002년 8월 산사태재해로 인해 피해가 발생된 바 있으며 중요 석조문화재가 위치해 있는 실상사 백장암지역을 연구대상지역으로 선정하여 산사태예측도를 작성하였다. 그리고 산사태재해 가능성을 발생확률로 표현하여 등급별로 구분함으로써 석조문화재 및 그 주변지역이 산사태에 취약한지의 여부를 평가하였다. 또한, 이러한 조사 및 해석기법을 앞으로 석조문화재 주변의 산사태재해 예측 및 평가를 위해 실용적으로 활용할 수 있는 토대를 마련하였다. It is a very difficult thing to estimate an occurrence possibility location and hazard expectation area by landslide. The prediction difficulty of landslide occurrence has relativity in factor of various geological physical factors and contributions. However, estimation of landslide occurrence possibility and classification of hazard area became available correlation mechanism through analysis of landslide occurrence through landslide data analysis and statistical analysis. This study analyzed a damage possibility of a cultual heritage area due to landslide occurrence by a heavy rainfall. We make a landslide prediction map and tried to analysis of landslide occurrence possibility for the cultural heritage site. The study area chooses a temple of Silsang-Sa Baekjang-Am site and made a landslide prediction map. In landslide prediction map, landslide hazard possibility area expressed by occurrence probability and divided by each of probability degrees. This degree used to evaluate occurrence possibility for existence and nonexistence of landslide in the study site. For the prediction and evaluation of landslide hazard for the cultural heritage site, investigation and analysis technique which is introduced in this study may contribute an efficient management and investigation in the cultural heritage site, Korea.

Comparative evaluation of various approaches for landslide hazard zoning: a critical review in Indian perspectives

Harjeet Kaur,Srimanta Gupta,Surya Parkash 대한공간정보학회 2017 Spatial Information Research Vol.25 No.3

The progress of geospatial technique can help to minimise the losses as it emerges as a powerful technique for mapping landslide hazard zonation. Different researchers use different methods for landslide hazard assessment. But, there is not a single method which has been universally accepted for effective assessment of landslide hazard. In Indian subcontinent, 12.6% of land area is susceptible to landslide hazard and the estimated total economic damage due to landslide hazard is 4,500,000US$. This review article represents the temporal development of different methodologies towards landslide hazard zonation up to a recent year and their advantages and disadvantages. The review indicates that mostly three methods i.e., knowledge driven, data driven and physical based method are followed among which, knowledge driven and bivariate analysis are mostly used during last decade but from the twenty-first century onwards multivariate statistical modelling is mostly popularised as it gives the most accurate result of landslide hazard zonation in comparison to other methods. Geospatial modelling of landslide susceptibility is useful for monitoring, mapping and formulating proper management plans that will be helpful for future landslide mitigation measures.

GIS를 이용한 땅밀림지 특성 분석: 산지경사 및 산사태위험등급을 중심으로

박재현,서정일,이창우 한국산림과학회 2019 한국산림과학회지 Vol.108 No.3

This study was carried out to establish basic data for the development of slow-moving landslide hazard classes. Mountain slopes in slow-moving landslide areas ranged from 11.8° to 37.0° with a mean slope of 23.8°. However, the slope inclination of microtopography in slow-moving landslide areas was slightly different, with a mean slope of 23.5° (10.7°~41.5°) compared with the mountain slope. There was a significant difference (p < 0.05) between the contour intervals of microtopography and the contour intervals of the slow-moving landslide areas. Among all the slow-moving landslide areas examined, 14 plots (approximately 38.0%) were classified into landslide hazard class I, 6 plots (approximately 16.0%) into landslide hazard class II, 5 plots (approximately 14.0%) into landslide hazard class III and IV, and 16 plots (approximately 43.0%) into landslide hazard class V, whereas 9 plots (approximately 24.0%) fit the no landslide hazard class. 이 연구는 땅밀림위험등급을 구축하기 위하여 수행되었다. 땅밀림지의 평균산지경사는 23.8°(11.8°~37.0°), 땅밀림지 내에서 미세지형지의 평균사면경사는 23.5° (10.7°~41.5°)로 미소한 차이가 있는 것으로 분석되었다. 땅밀림지 및 땅밀림 재발생지에서 땅밀림지 내 등고선 간격과 땅밀림지 내 미세지형지의 등고선 간격은 5% 수준에서 유의한 결과를 나타내었다. 산사태위험등급에 포함되지 않는 땅밀림지는 전체 땅밀림지 중 1등급이 14개소(약 38.0%), 2등급이 6개소(약16.0%), 3등급과 4등급이 각각 5개소(약 14.0%), 5등급이 16개소(약 43.0%), 산사태위험지등급 외 지역이 9개소(약24.0%)이었다. 땅밀림지 중 산사태위험 1~5등급으로 지정되지 않은 면적 비율이 50.0% 이상인 지역은 8개소(약 22.0%), 20.0%~50.0% 이상인 지역은 18개소(약 49.0%), 20.0% 이상인 지역은 26개소(약 70.0%)이었다.

Landslide Hazard Mapping Using GIS : A Case of Pelakot VDC, Syangja

Gajendra Sharma 위기관리 이론과 실천 2016 Journal of Safety and Crisis Management Vol.6 No.1

Landslides are one of the major natural disasters in Nepal and responsible for loss of property and lives. Landslide hazard mapping is an important tool for disaster management. The landslide hazard maps provide information about landslide vulnerability condition of certain region, which is beneficial for the community in planning, mitigating, and avoiding the danger. Various methods of hazard assessment have been proposed and demonstrated in Nepal. The use of Geographic Information Systems (GIS) for landslide hazard mapping has been increasing constantly in recent years in Nepal. In this study, GIS technology was applied to investigate zonation of the landslide hazards of the Pelakot VDC, Syagnja, Nepal. The Village Development Committee (VDC) is one of the susceptible areas to landslides in Syangja. In this particular area, several landslides were occurred. The method of landslide zonation used in this study was weighted overlay method. The causative factors include slope, landuse, geology, distance to drainage, distance to fault. The study of the area has been classified into five categories of relative landslide hazard namely, very low, low, moderate, and high. As a result, it can be concluded that 7% of this particular area has a high landslide hazard.

Amenity or hazard? The effects of landslide hazard on property value in Woomyeon Nature Park area, Korea

Kim, Jeongseob,Park, Junsung,Yoon, D.K.,Cho, Gi-Hyoug Elsevier 2017 Landscape and urban planning Vol.157 No.-

<P><B>Abstract</B></P> <P>A nature park in an urban area, which generally includes environmentally valuable natural landscape such as forests, mountains, rivers, and beaches, provides valuable benefits for the public such as recreational opportunities and an aesthetic landscape. However, residents near nature parks could be more vulnerable to natural disasters like floods, tsunamis, and landslides. In order to understand the trade-off between the amenity and hazard effects of nature parks, this study explores the case of the Woomyeon Nature Park (WNP) in Seoul, Korea, which experienced a catastrophic landslide disaster in 2011. The hazard and amenity effects of the WNP before and after a landslide event are analyzed using a difference-in-difference approach with a random coefficient model. The results show that the amenity effect of the WNP has continued after the landslide disaster in apartment complexes near the WNP, but its housing market premiums have fallen by up to 11.3% since the event due to the risk of landslide. The existence of the WNP hazard effect underlines the importance of disaster prevention efforts in urban open space design and management.</P> <P><B>Highlights</B></P> <P> <UL> <LI> In Korea, a mountain-type urban nature park increases nearby housing values as a place for leisure and recreation. </LI> <LI> Landslide hazard started to have a negative effect on housing values after the massive landslide event in Woomyeon Nature Park. </LI> <LI> A trade-off between the amenity and hazard effects of urban open spaces exists. </LI> <LI> Disaster prevention efforts in urban open spaces should be combined with landscape and urban planning. </LI> </UL> </P>

Hazard Prediction for Baishuihe Landslide in the Three Gorges Reservoirduring the Extreme Rainfall Return Period

Deying Li,Fasheng Miao,Yuanhua Xie,Chin Leo 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12

Landslide hazard prediction for the Three Gorges area is necessary for mitigating geohazards, especially under extreme rainfall conditions. A method for calculating rainfall in the extreme rainfall return period was first proposed. Then, geological conditions of the Baishuihe landslide on the reservoir shore were modelled, along with soil parameters. Four geological profiles were chosen, and the phreatic line of the landslide was simulated in the SEEP/W programme. The profiles were then divided into slices, and, the long-term stability and failure probability of each slice was calculated using the uncertainty of the soil parameters and the Monte Carlo method. An Empirical Bayesian Kriging (EBK) method in ArcGIS was used to obtain a hazard distribution map for the landslide’s active area and the deeper landslide. The standardized extreme rainfall for different return periods were then used to predict the hazard of the active area and determine the relationship between the unstable area within the active area and the rainfall return period. The stability of the Baishuihe landslide shows a periodic trend and a strong relationship with the reservoir water level and the rainfall distribution, while the stability of the deeper landslide is less affected. With an increase in the rainfall return period, the unstable area of the active area expands. The ratio of the unstable area in the active area and the rainfall return period show a logarithmic correlation. This paper solves the standardization problem of rainfall return period in the field of geological hazards, and realizes the visualization of local stability in the landslide area, which can promote to enhance the ability of preventing and controlling landslide hazards.

지진에 의한 산사태 위험도 평가방안에 관한 연구

서준표,유송,이기환,이창우,우충식 한국재난정보학회 2021 한국재난정보학회 논문집 Vol.17 No.4

연구목적: 지진에 의한 산사태 위험도 평가를 통하여 지진발생 전에는 산사태 예방사업, 지진발생 후에는 피 해지 예측 및 복구 우선순위 선정으로 지진유발 산사태 피해저감을 효율적·선제적으로 하기 위한 기초자료를 제공하고자 수행하였다. 연구방법: 국외 선행연구를 분석하여 평가 방법론 검토와 평가 인자를 도출하고 국 내 산사태 위험지도 활용성을 검토하였다. 또한 지진동 감쇠식을 이용하여 포항지역의 단층대 및 진앙지 기 준으로 지진에 의한 산사태 위험지도를 시범 구축하였다. 연구결과: 지진에 의한 산사태 위험도 평가 연구는 중국이 전체의 44%, 이탈리아 16%, 미국 15%, 일본 10%, 대만 8% 순으로 나타났다. 평가 방법론으로 통계적 모형이 59%로 가장 많았고, 물리적 모형이 23%로 나타났다. 통계적 모형에 많이 사용된 인자는 고도, 단층대 와의 거리, 경사도, 사면방향, 모암, 지형곡률로 나타났다. 현재 국내의 산사태 위험지도는 지형·지질·임상이 반영되는데 이를 활용한 지진에 의한 산사태 위험도 평가는 합리적인 것으로 나타났다. 포항지역에 단층대 및 진앙지 기준으로 산사태 위험도를 평가한 결과 기존의 낮은 등급이 높은 등급으로 변화하는 등 지진의 영 향이 고려되었다. 결론: 광역 단위의 지진유발 산사태 위험도 평가를 위해서는 산사태 위험지도를 활용하는 것이 효율적이다. 단층대 기준의 위험지도는 지진에 의한 산사태 피해방지를 위한 예방사방사업 대상지 선정에 활용하고, 진앙지 기준의 위험지도 는 지진이 발생한 이후 산사태 피해 현황을 조사하거나 피해지 복구 등 피해방지 대책 우선순위 선정의 효율적 사후관리에 활용할 수 있다. Purpose: In this study, earthquake-induced landslide risk assessment was conducted to provide basic data for efficient and preemptive damage prevention by selecting the erosion control work before the earthquake and the prediction and restoration priorities of the damaged area after the earthquake. Method: The study analyzed the previous studies abroad to examine the evaluation methodology and to derive the evaluation factors, and examine the utilization of the landslide hazard map currently used in Korea. In addition, the earthquake-induced landslide hazard map was also established on a pilot basis based on the fault zone and epicenter of Pohang using seismic attenuation. Result: The earthquake-induced landslide risk assessment study showed that China ranked 44%, Italy 16%, the U.S. 15%, Japan 10%, and Taiwan 8%. As for the evaluation method, the statistical model was the most common at 59%, and the physical model was found at 23%. The factors frequently used in the statistical model were altitude, distance from the fault, gradient, slope aspect, country rock, and topographic curvature. Since Korea's landslide hazard map reflects topography, geology, and forest floor conditions, it has been shown that it is reasonable to evaluate the risk of earthquake-induced landslides using it. As a result of evaluating the risk of landslides based on the fault zone and epicenter in the Pohang area, the risk grade was changed to reflect the impact of the earthquake. Conclusion: It is effective to use the landslide hazard map to evaluate the risk of earthquakeinduced landslides at the regional scale. The risk map based on the fault zone is effective when used in the selection of a target site for preventive erosion control work to prevent damage from earthquake-induced landslides. In addition, the risk map based on the epicenter can be used for efficient follow-up management in order to prioritize damage prevention measures, such as to investigate the current status of landslide damage after an earthquake, or to restore the damaged area.