• Journal of the Korean Society of Safety
• /
• v.30 no.3
• /
• pp.52-58
• /
• 2015

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, $-5^{\circ}$ 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, $0^{\circ}$ in the order. As a result, debris flow behavior analysis about the effect of the land slope could contribute to understand the vulnerability of city for debris flow hazards.

• The Journal of Engineering Geology
• /
• v.28 no.3
• /
• pp.341-348
• /
• 2018

Landslides can be caused by localized intense rainfall. The loss of human lives and damage to property from landslides is increasing. However, little information exists on the movement and flow of sediment material at the time of rapid landslides. In this study, a field survey was conducted of landslides that occurred in 2013 in the Hadari area of Yeoju city in Korea. This was followed by numerical analysis. The purpose is to analyze the characteristics of a consequent debris flow and its movement at the time of failure. The results of the field survey and numerical analysis are consistent with each other. The maximum velocity of the debris flow was ~9.335 m/s and the maximum sediment thickness ~4.674 m. The latter is similar to the traces of debris flow observed in the field.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.707-710
• /
• 2008

Recently, a rivers' bridge that locate on among the mountains area is destroyed by debris accumulation and debris flow, because of frequent occurrence of typhoon and a localized torrential downpour. therefore a river make a part of dam's effect. Actually, this situation gives damages like inundation of a bridge upper stream area's. Generally, It the main cause of the occurrence route of the debris accumulation is that outbreaks of driftwood and debris flow because of landslide, that occurred by severe rain storm. Also, a lot of debris are occurred when big flood come up during long period at this time, this kind of debris accumulation remove to other place, in several, and specially, debris accumlation move to the place where the depth of water is deep and velocity is fast river center. According to these kind of fact, this research put in effect and analyze that movement characteristic's numerical simulations of debris accumulation at flood according to a domestic outside literature investigation, on-site monitoring survey and parameter scenario which comes out through the hydraulic modeling analysis.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.13 no.4
• /
• pp.52-64
• /
• 2010

This study was carried out to analyze the occurrence characteristics and the influence of forest environment factors on the debris flow of 3 national parks in korea. The results obtained from this study were summarized as follows; The total number of debris flow occurrence was 125 areas. The average length of the debris flow scar was 144m, average width was 20m. And the average area and sediment were $2,854m^2$ and $3,959m^3$ respectively. The factors influencing the debris flow were highly occurred in Metamorphic rock, mixed forest type. And also, slope gradient was $30{\sim}35^{\circ}$, aspect was NE, altitude was over 1,000m, vertical and cross slope was concave (凹), soil depth was below 15cm, stream order was 0 order. The variables of cross slope (complex), deciduous tree, soil depth (over 46cm), cross slope (concave), mixed forest type and altitude (801~1200m) in correlation analysis were significant at 1 % level. The landslide of high mountain area highly tend to change the debris flow in stream bed of torrent. The debris flow in national parks mainly occurred in high mountain area with long ridge and steep slope.

• Journal of Korean Society for Geospatial Information Science
• /
• v.24 no.2
• /
• pp.15-24
• /
• 2016

This study conducted an evaluation of the extent of debris flow damage using SINMAP, which is slope stability analysis software based on the infinite slope stability method, and FLO-2D, a hydraulic debris flow analysis program. Mt. Majeok located in Chuncheon city in the Gangwon province was selected as the study area to compare the study results with an actual 2011 case. The stability of the slope was evaluated using a DEM of $1{\times}1m$ resolution based on the LiDAR survey method, and the initiation points of the debris flow were estimated by analyzing the overlaps with the drainage network, based on watershed analysis. In addition, the study used measured data from the actual case in the simulation instead of existing empirical equations to obtain simulation results with high reliability. The simulation results for the impact of the debris flow showed a 2.2-29.6% difference from the measured data. The results suggest that the extent of damage can be effectively estimated if the parameter setting for the models and the debris flow initiation point estimation are based on measured data. It is expected that the evaluation method of this study can be used in the future as a useful hazard mapping technique among GIS-based risk mapping techniques.

• The Journal of Engineering Geology
• /
• v.32 no.4
• /
• pp.547-558
• /
• 2022

In August 2020, a debris flow occurred in Gokseon, Jeollanam-do, that resulted in the death of five residents. In this study area, high-resolution 0.03 m topographic information was generated through photogrammetry, and the amount of soil movement/loss was measured. In addition, sensitivity analysis was performed for flow depth, flow velocity, and debris flow area with the program Flo-2D using the difference in simulation parameter that discharge and topographic information. Wth increasing debris flow input discharge, increases were seen in flow depth, flow velocity, and debris flow area, as ell as in the gap in results from high-resolution topographic information and low-resolution topographic information. Also, when high-resolution topographic information was used, the results were similar to the actual (measured) flow direction of the debris flow. Therefore, the application of high-resolution topographic information increases the accuracy of the debris flow analysis results compared with low-resolution information. Results could be further imporved in the future by considering geological information such as yield stress and viscosity.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.3
• /
• pp.49-55
• /
• 2015

The rainfall pattern, rainfall intensity as well as topographical conditions used for the analysis of debris flow affect, in general, the magnitude of debris flow and flow velocity, when debris flow occurs. The consideration of topographical conditions implies that the topography is equally divided into grids and the slope of inside the grid is computed as an average, leading to, in turn, obtain the closer results to the reality as the grid is smaller in the case of the severely bended topography. Although the size of grid should be as small as possible so as for more accurate analysis of debris flow, the analysis of debris flow has been so far conducted by using sparsely divided grids due to the limitation of analysis algorithm, computational ability and running time. So, it is necessary to suggest an appropriate grid size for the practical approaches. Therefore, this study presents the evaluation of the effect of the size of a grid on the debris flow besides the factors which referred to the previous studies such as accumulated rainfall, rainfall intensity and rainfall duration time. From this, it enables to suggest a rational and practical grid size for topography to be divided.

• Journal of the Korean Society of Safety
• /
• v.33 no.4
• /
• pp.84-89
• /
• 2018

The number of landslides has increased since the 2000s due to the increased frequency of heavy rainfall caused by abnormal weather. A variety of debris flow prevention facilities have been installed as a countermeasure against this problem. However, it is not easy to evaluate the efficiency of debris flow prevention structures except for the structures with constant volume such as the erosion dam, because the other structures are limited to be reproduced in simulation program for debris flow. Therefore, the methods by which the debris flow prevention structures were modeled were proposed, and the efficiency of four prevention structures installed in Baekyang Mt. in Busan was evaluated with UDS, which accuracy had been verified, using these methods. The initial amount of debris flow was determined based on landslide which occurred in 2014, and specifications of the complex retaining walls around the settlements were measured and applied modeling for terrain. The numerical results showed that the efficiency of debris flow prevention structures could be quantitatively presented. Among the debris flow prevention structures installed in Baekyang Mt., prevention structure of barrier type for debris flow was the most efficiency and debris flow prevention device was the lowest efficiency when the only depth of debris was evaluated. It seems that this study is meaningful to propose the methods which were used to model the debris flow prevention structures that could not be reproduced in most 2D debris flow numerical analysis programs. If precise verification of the presented methods is carried out, it will be possible to provide clear criteria for the efficiency evaluation method of disaster prevention structures.

• Journal of Korean Society for Geospatial Information Science
• /
• v.24 no.3
• /
• pp.59-66
• /
• 2016

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.

• Proceedings of the Korea Contents Association Conference
• /
• 2016.05a
• /
• pp.241-242
• /
• 2016

Recent abnormal climate change induces localized heavy rainfall and extreme disasters such as debris flow near urban area. Thus many researches have been conducted to estimate and prevent, especially in focus of physical behavior of debris flow. Even though it is hardly to consider overall related parameters to estimate the extent and degree of directly or indirectly damages due to debris flow. Those analytic restraint would be caused by the diversity and complexity of regional topographic and hydrodynamic characteristics of debris flow inside. We have utilized the Bayesian method to compensate the uncertainty due to the complex characteristics of it after analyzing the numerical results from FLO-2D and field measurement data. Revised values by field measurements will enhance the numerical results and the missing parameters during numerical simulation will be supplemented with this methodology. As a final outcome in this study, the risk index of debris flow damage will be suggested to provide quantitative estimation in terms of hazard protection including the impact on buildings, especially in inner and outer of urban area.