한국 토석류의 이동거리 특성

최두영(Choi Dooyoung),백중철(Paik Joongcheol) 대한토목학회 2012 대한토목학회논문집 B Vol.32 No.3B

지난 10년이래 집중강우에 의해서 유발된 토석류가 우리나라에서 현저히 발생하고 있다. 그로 인해 산지유역에서 토석류는 가장 위험한 자연재해 중 하나가 되고 있다. 토석류 위험지도와 방재 기술을 개발하기 위해서 먼저 이해해야 하고 정확히 예측해야 하는 것 중 하나는 발생한 토석류의 이동거리이다. 단순하고 적용범위가 넓은 sled 모형에 근거해서, 이 연구에서는 현장조사를 통해 구한 토석류 자료를 이용하여 토석류의 수평이동거리(L)에 대한 토석류 시작점과 퇴적점의 표고차(H) 비로 정의되어 이동성을 나타내는 토석류의 순효율을 산정하였다. 2002년 이후 현재까지 확보된 국내 238개의 토석류 현장 자료를 분석한 결과 한국 토석류의 순효율 대푯값은 4.3인 것으로 나타났다. 가장 많은 토석류가 발생하는 강원지역의 경우 강릉과 평창지역보다는 인제지역의 토석류가 상대적으로 표고차에 비해 이동거리가 큰 것으로 나타났다. 국내 토석류를 중부 지역과 남부지역으로 나눠 분석한 결과 두 지역 모두 토석류의 전반적인 순효율 분포는 유사한 것으로 나타났다. 가용한 토석류 퇴적조건 적용과 항공사진 분석을 통해 산정하는 방법은 토석류의 순효율을 과대 산정하는 것으로 나타났다. 이 방법을 적용하기 위해서는 우리나라 토석류에 적합한 퇴적조건을 도출하는 연구가 필요한 것으로 나타났다. In the last decade, heavy rainfall induced debris flow events have been remarkably occurred in Korea. Consequently, debris flow is becoming one of the most dangerous natural phenomena in mountainous area. Understanding and correct predicting of the runout distance of debris flow is an essential prerequisite for developing debris flow hazard map and prevention technology. Based on the simple and widely used sled model, in this study, we analyse the net efficiency of debris flows which is a dimensionless constant (=1/R) and defined by the ratio of the horizontal runout distance L from the debris flow source to deposit and the vertical elevation H of the source above the deposit. The analysis of field data observed in total 238 debris flow events occurred from 2002 to 2011 reveals that the representative value of the net efficiency of debris flows in Korea is 4.3. The data observed in Gangwon province where is the most debris flow-prone area in Korea shows that debris flows in Inje area have the runout distance longer than those in Pyongchang and Gangneung. Overall features of the net efficiency of debris flows observed in the central Korea are similar to those in the southern Korea. The estimation based on aerial photographs and available depositional conditions appears to overestimate the net efficiency compared to estimation based on the field observations, which indicates that appropriate depositional conditions need to be developed for debris flows in Korea.

전파면의 경사에 따른 토석류 흐름양상에 대한 연구

이준선 ( Jun Seon Lee ),송창근 ( Chang Geun Song ),김홍택 ( Hong Teak Kim ),이승오 ( Seung Oh Lee ) 한국안전학회(구 한국산업안전학회) 2015 한국안전학회지 Vol.30 No.3

As sudden rainfall has happened, the debris flow has occurred in the mountain area. Recently sudden rainfall occurred so frequently caused by abnormal climate. Thus debris flow hazard had consecutively increased damage because of debris flow. Recently, Enormous damage due to debris flow have occurred in Korea. Various studies have been conducted to prevent search debris flow hazard. This study was carried out for debris flow behavior according to the land slope on propagation. It is the important one among factors that are related to the propagation over the city with respect to debris flow discharge and depth. For the numerical simulations in this study, the land slope was varied of 5, 0, -5 ° to investigate the debris flow behavior with the FLO-2D, often recommended by FEMA to simulate debris flow. To verify the performance of FLO-2D, comparison with the USGS experiments (Iverson et al, 2010) was conducted. From numerical results the propagation length of the debris flow was found the most sensitive one. Maximum of debris flow thickness and velocity and structural vulnerabilities were investigated to the effect of land slope. They was became smaller according to land slope of 5, -5, 0 ° in the order. As a result, debris flow behavior analysis about the effect of the land slope could contribute to understand thevulnerability of city for debris flow hazards.

토석류 규모 산정과 영향인자와의 상관성 분석

최영남(Young-Nam Choi),황희석(Hui-Seok Hwan),이형호(Hyung-Ho Lee),유남재(Nam-Jae Yoo) 한국지반신소재학회 2017 한국지반신소재학회 논문집 Vol.16 No.2

본 연구에서는 2006년부터 2013년 까지 강원도 영서 인근 지역의 토석류 피해지역 43개소에 대한 현장조사 결과를 바탕으로 토석류 규모를 산정하고 영향인자가 토석류 규모에 미치는 상관성 분석을 실시하였다. 토석류의 규모는 발생지역별로 큰 차이를 보이나 계곡형이 사면형보다 약 6.5배 큰 것으로 조사되었으며 계곡형 발생부의 토석류 규모는 전체의 약 5% 정도의 규모인 것을 확인하였다. 침식률은 계곡형에서 전체 토석류 발생량이 10,000m<SUP>3</SUP>보다 큰 대규모인 경우 19m<SUP>3</SUP>/m, 10,000m<SUP>3</SUP>보다 작은 경우 8m<SUP>3</SUP>/m의 값을 갖고, 사면형은 5m<SUP>3</SUP>/m로 산정되었다. 토석류 규모의 영향인자에 대한 상관성 분석결과, 토석류 유하부의 길이와 폭은 상관성이 높은 것으로 나타났으며, 평균경사와 침식 깊이는 상관성이 낮은 것으로 나타났다. 특히, 침식깊이는 규모와 상관성 없이 0.5~2.6m의 범위로 Ikeya(1981)가 제안한 값과 유사하였다. 연속강우량, 최대시간강우량 등 토석류 유발강우와 토석류 규모는 상관성이 낮은 것으로 분석되었다. In this paper, for 43 sites neighboring to western area of Gangwondo where disaster of debris flow occurred from 2006 to 2013, magnitude of debris flow was estimated from results of site investigation and correlation analysis between influencing factors to its magnitude was performed. Magnitude of channelized debris flow was found greater by 6.5 times of that of hill slope debris flow and approximately 5% of total volume was occurred at initiation part of channelized debris flow. As results of analyzing yield rate of debris flow, for channelized debris flow, yield rate values of 19 m<SUP>3</SUP>/m and 8㎥/m were obtained for total volume being over 10,000 m<SUP>3</SUP>/m as the large scale of debris flow and less than 10,000 m<SUP>3</SUP>/m respectively, and value of 5 m<SUP>3</SUP>/m was estimated for hill slope debris flow. As results of correlation analysis of influencing factors to magnitude of debris flow, runoff distance and erosion width were very highly correlated to its magnitude whereas average slope of basin and erosion depth showed relatively low correlation. In particular, value of erosion depth was in the range of 0.5-2.6 m, being similar range to the value proposed by Ikeya (1981). Triggering rainfall to debris flow such as continuous rainfall and maximum intensity of hour rainfall were analyzed to have low correlation with magnitude of debris flow.

계곡형 토석류가 발생한 급경사 신기 계곡의 특성

박상덕,김용현,함광현,손상진,나락스메이,김남진 한국지형학회 2021 한국지형학회지 Vol.28 No.3

In mountain gully, channelized debris flow is an important phenomenon in the process of topographical change. Social infrastructure as roads may be damaged by channelized debris flows, but there has been little information about their occurrence and movement to prepare for the risk of the debris flow. Most of the channelized debris flows occur during heavy rains in mountainous valleys that are difficult to access, so there are not many field data. In this study, the topographical characteristics of the catchment, the rainfall and runoff related to the debris flow, the sedimentary pattern and the cross-sectional change of the channel bed, and the underflow velocity of the gravel bed have been investigated and analyzed in the Singi gully where the channelized debris flows occurred. In the catchment, there was almost no sediment runoff because the vegetation combine with the debris landforms and covered the surface. Therefore, the obvious cause of the channelized debris flows is the collapse of the slope and bed of the gully. Even if the gravel, cobbles, and boulders of the channel bed were lost by debris flow, the thalweg change due to debris flow may not be significant because they are supplied from the gully side slope normally. After the gabion structures were installed, the debris flow increased the thalweg change, bed erosion and side slope of the gully. Various sedimentary structures in the gully were classified according to the factors supporting the sedimentation. The hypsometric curve of the gully reflects the debris landforms and vegetation characteristics of the watershed and the sediment runoff due to debris flow, etc. The relationship between the flow velocity and the hydraulic gradient was non-linear under the condition that the porous medium with gully bed gravels is saturated with water. These results may be used as basic data for channelized debris flow research.

계곡형 토석류가 발생한 급경사 신기 계곡의 특성

박상덕 ( Sang Doeg Park ),김용현 ( Yong Hyun Kim ),함광현 ( Gwang Hyun Ham ),손상진 ( Sang Jin Son ),나락스메이 ( Raksmey Na ),김남진 ( Nam Jin Kim ) 한국지형학회 2021 한국지형학회지 Vol.28 No.3

In mountain gully, channelized debris flow is an important phenomenon in the process of topographical change. Social infrastructure as roads may be damaged by channelized debris flows, but there has been little information about their occurrence and movement to prepare for the risk of the debris flow. Most of the channelized debris flows occur during heavy rains in mountainous valleys that are difficult to access, so there are not many field data. In this study, the topographical characteristics of the catchment, the rainfall and runoff related to the debris flow, the sedimentary pattern and the cross-sectional change of the channel bed, and the underflow velocity of the gravel bed have been investigated and analyzed in the Singi gully where the channelized debris flows occurred. In the catchment, there was almost no sediment runoff because the vegetation combine with the debris landforms and covered the surface. Therefore, the obvious cause of the channelized debris flows is the collapse of the slope and bed of the gully. Even if the gravel, cobbles, and boulders of the channel bed were lost by debris flow, the thalweg change due to debris flow may not be significant because they are supplied from the gully side slope normally. After the gabion structures were installed, the debris flow increased the thalweg change, bed erosion and side slope of the gully. Various sedimentary structures in the gully were classified according to the factors supporting the sedimentation. The hypsometric curve of the gully reflects the debris landforms and vegetation characteristics of the watershed and the sediment runoff due to debris flow, etc. The relationship between the flow velocity and the hydraulic gradient was non-linear under the condition that the porous medium with gully bed gravels is saturated with water. These results may be used as basic data for channelized debris flow research.

Development of an initiation criterion for debris flows based on local topographic properties and applicability assessment at a regional scale

Kang, Sinhang,Lee, Seung-Rae,Vasu, Nikhil N.,Park, Joon-Young,Lee, Deuk-Hwan Elsevier 2017 Engineering geology Vol.230 No.-

<P><B>Abstract</B></P> <P>Damages caused by landslides have been increasing because of the greater frequency of localized heavy rain. To prevent landslide disasters more efficiently, more studies in relation to predicting the initiation areas of debris flows that cause large-scale damage are necessary. The main purpose of this study is to develop a criterion for detecting debris flow initiation areas by using an empirical method that was chosen from several types of approaches to debris flow initiation detection. In this study, ten GIS-based geomorphological datasets were obtained from slide and debris flow initiation areas located in Seoul, Gyeonggi Province and Gangwon Province. The geomorphological characteristics of slide and debris flow occurrence areas were analyzed through a comparative analysis to identify relationships between debris flow initiation and each topographic index. An initiation criterion for debris flows based on the geomorphological characteristics was suggested using an Artificial Neural Network (ANN) model combined with a modified threshold for the relationship between slope and upslope contributing area. To validate the suitability of the initiation criterion for debris flow, sequential applications of slope failure analysis and debris flow initiation analysis were conducted on a case study site to simulate the actual debris flow events. As a result of the debris flow initiation analysis, the prediction capture rate of the debris flow initiation criterion was determined to be 88.9%. Debris flow initiation areas totaling 143,300m<SUP>2</SUP> were identified among 1,935,400m<SUP>2</SUP> of slope failure areas predicted in the slope failure analysis. It is efficient to apply the debris flow initiation criterion in the debris flow simulation because slope failure areas are only partly transformed into debris flows.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We developed a new criterion to predict the debris flow initiation area. </LI> <LI> The criterion composed of an ANN model and a modified slope-UCA threshold was in good agreement with actual cases. </LI> <LI> We conducted sequential applications of slope failure analysis and debris flow initiation analysis to validate the criterion. </LI> </UL> </P>

항공LiDAR 자료를 이용한 토석류 침식 및 퇴적모델 분석

원상연(Won, Sang Yeon),김기홍(Kim, Gi Hong) 대한공간정보학회 2016 대한공간정보학회지 Vol.24 No.3

2011년 발생한 서울시 우면산의 토석류는 과거 산간지역 피해와는 달리 도심지역에서 큰 피해가 발생하였다. 따라서 산사태 및 토석류는 산악지역과 도심지역에 관계없이 다양한 지역에서 빠른 속도로 발생하여 엄청난 피해를 유발시키기 때문에 많은 연구자들은 토석류의 영향범위를 예측하고 피해를 최소화하기 위해 노력하고 있다. 토석류의 영향범위 예측을 위한 가장 핵심적인 부분은 복잡한 3차원 지형에서의 토석류 거동 및 퇴적 메커니즘을 이해하여야 한다. 그리고 퇴적 메커니즘을 이해하기 위해서는 토석류의 거동에 따른 에너지량과 침식량이 산정되어야 한다. 하지만 기존에 개발된 토석류 모델들은 토석류의 침식량을 산정하는데 한계가 있었다. 따라서 본 연구에서는 2011년 도심지의 대규모 토석류가 발생한 서울시 우면산 지역을 대상으로 항공사진, 항공 LiDAR 자료로부터 생성된 토석류 피해 전과 후의 DEM을 활용하여 토석류의 피해규모를 산정하였으며, 에너지 이론을 기반으로 하여 침식량을 산정할 수 있는 토석류 거동 해석 모델을 개발하여 비교하였다. 또한 동일지역에 대하여 기존의 토석류 모델(RWM, Debris 2D)도 함께 시뮬레이션 하여 종합적으로 토석류 지역을 비교 분석하였다. The 2011 debris flow in Mt. Umyeonsan in Seoul, South Korea caused significant damages to the surrounding urban area, unlike other similar incidents reported to have occurred in the past in the country’s mountainous regions. Accordingly, landslides and debris flows cause damage in various surroundings, regardless of mountainous area and urban area, at a great speed and with enormous impact. Hence, many researchers attempted to forecast the extent of impact of debris flows to help minimize the damage. The most fundamental part in forecasting the impact extent of debris flow is to understand the debris flow behavior and sedimentation mechanism in complex three-dimensional topography. To understand sedimentation mechanism, in particular, it is necessary to calculate the amount of energy and erosion according to debris flow behavior. The previously developed debris flow models, however, are limited in their ability to calculate the erosion amount of debris flow. This study calculated the extent of damage caused by a massive debris flow that occurred in 2011 in Seoul’s urban area adjacent to Mt. Umyeonsan by using DEM, created from aerial photography and airborne LiDAR data, for both before and after the damage; and developed and compared a debris flow behavioral analysis model that can assess the amount of erosion based on energy theory. In addition, simulations using the existing debris flow model (RWM, Debris 2D) and a comprehensive comparison of debris flow-stricken areas were performed in the same study area.

유역별 토석류 위험도 평가 모델

유한중,신종환,서흥석,김기홍,이승우 한국방재학회 2012 한국방재학회논문집 Vol.12 No.4

In general, landslides of mountain areas have been occurred by typhoon and severe rain storm in Korea. The multiple landslides caused by heavy rain may lead to debris flow which is very rapid downslope movement of debris of a high water content along stream channels. Generally, a debris flow causes larger and severe damage. than a landslide. To protect and reduce the damage of debris flow, a reliable tool to predict potential damage area by drbris flow is needed. Since the water and moveable soils by landslide flow from high elevation to low elevation with additional erosion through the stream of valley, the magnitude of debris can subsequently amplified. Therefore any structures and people in the path of debris flow lies in great risk. Due to the chacteristics of debris flow which is delivered quite a long distance from the location of initiation (hundread meters - kilometers), the risk analysis of debris flow should consider larger area compared with landslide analysis and analysis unit need to be determined based a watershed. In this study, an anlysis tool for the evaluation of debris flow risk in a watershed incorperated with GIS system is proposed. The essence of system is a model to predict the risk of debris flow for any given location. The model is developed based on the statistical analysis of forty eight debris flow cases, which obtained from: field surveys, disaster reports on national roads of korea, and digital maps of the debris flow area. Each set of data in the database includes debris flow size, rainfall information,bedrock types, and run out distance of the debris. The comparison between predicted risk and actual occurrence of the debris flow hazard for forty eight site, showed accuracy of seventy seven percent based on accuracy-classification. 최근 국내 산사태는 주로 태풍 혹은 국지성 집중호우에 의해 발생하기 때문에, 강우가 내리는 지역 내에서 동시다발적으로발생하는 경향을 보이며, 토석류의 경우 다수의 산사태에서 발생된 사태물질이 계곡부를 따라 흘러 본류로 합류하기 때문에 일반적인 산사태에 비해 사태물질의 규모가 크다. 또한 피토석류 시발점으로부터 수백 미터에서 수 킬로미터까지의 떨어진 위치까지 토석류 피해가 전파될 수 있으므로 토석류에 의한 피해를 예측하기는 매우 어렵다. 따라서 토석류의 위험도를 평가하기 위해서는 임의의 피해지역까지 도달 가능한 토석류를 유역단위로 구분하여 분석하는 모델이 효과적이다. 본 연구에서는 유역별 토석류 위험도 평가모델을 개발하기 위하여 다양한 공간정보를 보유하고 있는 GIS시스템을 이용하였으며, 임의의 피해지역에 대해 도달 가능한 범위의 유역을 선정하였다. 또한 토석류 피해 발생에 영향을 미칠 수 있는 토석류 규모, 강우 정보, 표토의모암, 토석류 이동거리 등의 자료를 재해대장과, 항공사진분석, 그리고 현장조사를 실시하였으며, 48개 유역의 토석류 피해 데이터에 대한 통계적 분석을 수행하여 유역별 토석류 위험도 평가 모델을 제안하였다. 제안된 예측 모델로 예측된 결과와 실제토석류 피해발생여부를 비교해 본 결과 약 77%의 분류 정확도를 보였다.

횡단 배수로에서 토석류 퇴적에 대한 유사농도와 바닥경사 영향 실험연구

김영일(Kim,Youngil),백중철(Paik,Joongcheol) 대한토목학회 2011 대한토목학회논문집 B Vol.31 No.5B

토석류는 산간지역에서 발생할 수 있는 가장 위험한 자연현상 중 하나이다. 토석류로 인한 배수구조물의 통수능 저하는 도로의 파괴뿐만 아니라 인명과 재산의 피해를 야기시킬 수도 있다. 이러한 토석류 피해를 막기 위한 배수구조물의 진보된 설계 기술을 개발하기 위해서는 토석류의 유사체적농도 그리고 접근 수로와 배수로의 경사를 포함하는 다양한 조건에 대해서 토석류의 흐름 거동을 이해하고 정확하게 재현할 수 있어야 한다. 이 연구에서는 경사 변화점을 갖는 일정한 폭의 사각형 수로에서 일련의 토석류 실험을 실시하였다. 실험수로는 15°~30°의 경사조절이 가능한 접근수로와 전형적인 배수로를 재현하기 위한 0°~12°의 경사조절이 기능한 하류부 배수로로 이루어진다. 실험은 서로 다른 수로의 경사와 유사체적농도의 조합으로 구성된 전체 22개의 실험조건에 대해서 수행하여 이들 실험 변수들이 토석류의 흐름 거동에 미치는 영향을 분석하였다. 실험결과는 먼저 동일 유량 조건에 대해서 토석류 흐름은 물 흐름에 비해서 유사체적농도에 따라서 약 50%에서 150%정도 수심이 크게 형성되는 것으로 나타났다. 실험결과는 배수로에서 토석류의 흐름 거동과 퇴적의 시간적 변화 특성이 접근수로 및 배수로의 바닥경사 그리고 유사체적농도 특성에 지배됨을 정량적으로 보여준다. 아울러 실험 자료에 근거해서, 토석류의 퇴적을 방지할 수 있는 배수로의 최적 경사를 결정할 수 있는 로지스틱 모형을 개발하였다. 이 로지스틱 모형은 우수한 정확도로 배수로에서의 토석류 퇴적 유무를 판별할 수 있는 것으로 나타났다. Debris flow is one of the most hazardous natural processes in mountainous regions. The degradation of discharge capacity of drainage facilities due to debris flows may result in damages of properties and casualty as well as road. Understanding and accurate reproducing flow behaviour of debris flows at various conditions, such as sediment volume concentration and approaching channel and culvert slopes, are prerequisite to develop advanced design criteria for drainage facilities to prevent such damages. We carried out a series of laboratory experiments of debris flows in a rectangular channel of constant width with an abrupt change of bottom slope. The experimental flume consists of an approaching channel part with the bed slope ranging 15° to 30° and the test channel with slope ranging from 0° to 12° which mimics a typical drainage culvert. The experiments have been conducted for 22 test cases with various flow conditions of channel slopes and sediment volume concentration of debris flows to investigate those effects on the behaviour of debris flows. The results show that, according to sediment volume concentration, the depth of debris flow is approximately 50% to 150% larger than that of fresh water flow at the same flow rate. Experimental results quantitatively present that flow behaviour and deposit history of debris flows in the culvert depend on the slopes of the approaching and drainage channels and sediment volume concentration. Based on the experimental results, furthermore, a logistic model is developed to find the optimized culvert slope which prevents the debris flow from depositing in the culvert.

흐름 경사면의 경사도에 따른 토석류 흐름의 특성 분석

이준선 ( Jun Seon Lee ),송창근 ( Chang Geun Song ),이승오 ( Seung Oh Lee ) 한국안전학회(구 한국산업안전학회) 2016 한국안전학회지 Vol.31 No.2

In Korea, there exist many mountains, and sudden storms occur during the summer season. When severe rainstorm events occur in steep slope topography, risk of debris flow is increased. Once debris flow occurs in urban area, it may cause casualties and physical damages due to rapid debris flow velocity along a steep slope. Accordingly, preventing method of sediment-related disaster for demage mitigation are essential. Recently, various studies on debris flow have been conducted. However, the prediction of the physical propagation of debris flow along the steep slope was not thoroughly investigated. Debris flow is characterized by various factors such as topography, properties of debris flow, amount of debris flow. In the study the numerical simulation was focused on the topographic factor. Fundamental analysis of the risk area was implemented with emphasis on the propagation length, thickness, and the development of maximum velocity. The proposed results and the methodology of estimating the structural vulnerability would be helpful in predicting the behavior and the risk assessment of debris flow in urban area. These results will be able to estimate the vulnerability of urban areas affected the most damage by debris flow.