• Journal of Korean Society of Forest Science
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• v.105 no.3
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• pp.315-320
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• 2016

This study was carried out to establish a management plan for urban forest trails with analysis of trail damage types and soil physicochemical properties on 3 urban forest parks in Jinju, Gyeongnam-do. We found that soil hardness was significantly higher in forest trails than forest area at 0 cm and 5 cm at a significance level of 0.05. However, we could not find any significant differences for other soil properties. For the trail damage types, the most common types were as follows: trail expansion (66%), trail erosion (59%), side road (57%), and trail boundary erosion and root exposure (41%). The results showed no difference in most of these types between the trails and forest area, indicating that the forest area might be damaged as well as the trails. Priority should be given to prepare measures that prevent soil compaction from overcrowded hikers.

• Journal of the Korean GEO-environmental Society
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• v.10 no.2
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• pp.69-76
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• 2009

In this study, design method for debris flow and drift wood dams used in Japan was evaluated to develop currently available design method practiced in Korea. In Japan, represented a similarity in the aspects of topography and the climate compared with Korea, casualties due to debris flow, landslide, and collapse of cliff as well as earthquake, have been reported every year. Especially, debris flow had often occurred during heavy rainy season rather than due to Typhoons or localized torrential thunderstorms. Since the characteristic of the debris flow reveals in the middle of water flow and soil behaviors, the behavior of debris flow associated with drift wood was not fully understood at this moment and therefore empirical design method to design debris flow dam is adopted in the practice and currently used in Japan. Based on the result of this study, modification of debris flow design method used in Korea are presented.

• The Journal of Engineering Geology
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• v.23 no.3
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• pp.257-269
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• 2013

Prevention plans for landslide and slope disasters should be appropriate for a country's budget when considering a systematic investment plan. The systematic management of slopes adjacent to national highways should incorporate reasonable investment risk and the expected degree of damage should be calculated by considering the investment priorities. In terms of priority of investment, the major factors used to determine the degree of hazard are gradient, soil characteristics, RMR (Rock Mass Rating), stability interpretation, type of discontinuities, and history of collapse, among others. The likely consequences of slope failure can be determined by considering traffic volume, the number of lanes, and average vehicle risk. We performed such calculations regarding the priority of investment and performed a regression analysis for 392 slopes located in Yeongseo region, Gangwon province. The calculation results show that collapsed slopes have a higher priority for investment, as do slopes with a high proportion of dangerous sections and locations in valleys.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.7-7
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• 2023

국내뿐만 아니라 세계적으로도 산사태 발생에 따른 토석류 피해가 빈번하게 발생하고 있으나 아직 토석류 거동에 대한 물리적인 특성을 규명하고, 실험 등을 통한 면밀한 검토가 안 되었다. 토석류는 집중호우 시 토사 내 함수량의 증가로 인해 또는 지진, 화산 발생 시 지각 변동으로 인해 사면의 저항력이 약화되어 발생한다. 이러한 토석류는 재해를 일으키는 매우 위험한 자연 현상이며, 그 규모에 따라 하류부에 큰 피해를 발생시킬 수 있다. 국내에서 수행된 토석류 관련 연구들은 해외에서 주로 수행된 기초연구 결과를 이용한 토석류 피해 발생예측, 위험지도 작성, 토석류 방지 구조물 개발 등의 응용연구가 대부분이며 소규모 모형을 제작하여 수리실험이 진행되었다. 김기환 외(2008)은 토석류 확산형태와 흐름 속도에 대한 모형실험을 수행하였으며, 김영일과 백중철(2011)은 토석류 유동과 퇴적 특성에 대한 실험을 수행하였다. 미국의 경우 미지질조사국(USGS, U.S Geological Survey)에서 1994년부터 지금까지 100 m 길이의 대형 경사수로를 이용하여 토석류 수리모형실험을 수행하고 있으며 이를 통해 토석류의 수위, 충격력, 전파속도, 유출 후 퇴적형상 등에 대한 다양한 실험데이터를 제시하고 있다. 그러나, 현재까지 국내외 토석류 실험에 대한 표준실험방법과 기준이 정립되지 않아 실험결과의 신뢰성을 명확히 증명하기 어려운 실정이다. 토석류로 인한 가장 직접적인 피해 인자인 토석류의 충격력과 전파속도를 수리모형실험을 통해 정량적으로 파악하기 위한 시험 표준으로 시험 절차, 시험 방법 및 적정한 측정장비의 사양 등을 단체표준을 통해 제공함으로써 시험의 불확실성을 최소화하고, 명확한 프로세스에 따른 시험 결과의 신뢰성과 일관성을 확보하고자 한다. 국토교통연구인프라운영원에서는 단체표준 개발을 위한 시험기관협의체를 구성하고, 이해관계인들의 의견을 반영한 토석류 충격력과 전파속도 측정방법(안)을 2022년에 7월 작성하였으며, 현재 이해관계자들의 의견을 수렴하고 중소기업중앙회에 심의를 상정한 상태이다.

• Journal of Korean Society of Forest Science
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• v.105 no.3
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• pp.321-329
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• 2016

To estimate the sediment discharge controlled by sediment-filled check-dam and thereby enhancing factor for check-dam design and dredging criteria, we surveyed slope failures and stream-bed fluctuation caused by geomorphic disturbances (i.e., landslides and debris flows) in Inje, Gangwondo. In general, check-dams play roles for restraining and controlling sediment discharge within a section under the design equilibrium gradient and a section under the design flood gradient, respectively. The results in this study showed same pattern: that is, the closed type check-dam, which has a design restraint sediment discharge of $2,111m^3$, estimated to control a sediment discharge of $3,996m^3$ in the stream section within 250 m right upper area immediately after the disturbances occurred in 2006. As a result, a design control sediment discharge of the check-dam was larger than its design restraint sediment discharge. This represents that the check-dam is still having an own function for controlling sediment discharge although it exceeded the designed capacity by the sediment discharged from upstream during the disturbances. Our finding suggests that the sediment discharge controlling of check-dam may need to be evaluated separately from its sediment discharge restraint. Currently, the country, however, does not consider the design control (or restraint) sediment discharges, based on the actual field survey, as criteria for check-dam design and/or dredging work. Therefore, the accumulation of the quantitative data is required to support that check-dam has functions for both restraining and controlling sediment discharge. This would be a way to develop our erosion control technology to the scientific technology equipped with a more objective and systematic aspects.

• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1187-1198
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• 2014

Strong winds and heavy rainfall from tropical cyclones (TCs) that occur in the Northwestern Pacific cause significant human and material damage to the Korean peninsula and East Asia. Hence, it is important to establish early warning systems and conduct preparedness activities in advance of a TC. This study suggests a technique to extract the value of uniform TC-induced rainfall considering the TC track and TC size. To validate our technique, we compare it to existing TC rainfall techniques using the spatial domain. To determine the TC size required for extracting TC-induced rainfall, this research analyzed the mean of TC-induced rainfall by TC size (1973-2012). As a result of this analysis, the maximum amount of mean of TC-induced rainfall was found for a TC with a radius of 700 km. Other techniques have limitations which this new technique addresses; it can extract TC-induced rainfall in each administrative area and minimize systematic biases of other extraction methods. The result of this study can be utilized in the preparation of rainfall forecasts, designing hydraulic structures, and predicting landslide and debris flows using TC-induced rainfall and downpours.

• Journal of Korean Society of Forest Science
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• v.83 no.2
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• pp.175-190
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• 1994

In order to get fundamental information for prediction of landslide hazard, both forest and site factors affecting slope stability were investigated in many areas of active landslides. Twelve descriptors were identified and quantified to develop the prediction model by multivariate statistical analysis. The main results obtained could be summarized as follows : The main factors influencing a large scale of landslide were shown in order of precipitation, age group of forest trees, altitude, soil texture, slope gradient, position of slope, vegetation, stream order, vertical slope, bed rock, soil depth and aspect. According to partial correlation coefficient, it was shown in order of age group of forest trees, precipitation, soil texture, bed rock, slope gradient, position of slope, altitude, vertical slope, stream order, vegetation, soil depth and aspect. The main factors influencing a landslide occurrence were shown in order of age group of forest trees, altitude, soil texture, slope gradient, precipitation, vertical slope, stream order, bed rock and soil depth. Two prediction models were developed by magnitude and frequency of landslide. Particularly, a prediction method by magnitude of landslide was changed the score for the convenience of use. If the total store of the various factors mark over 9.1636, it is evaluated as a very dangerous area. The mean score of landslide and non-landslide group was 0.1977 and -0.1977, and variance was 0.1100 and 0.1250, respectively. The boundary value between the two groups related to slope stability was -0.02, and its predicted rate of discrimination was 73%. In the score range of the degree of landslide hazard based on the boundary value of discrimination, class A was 0.3132 over, class B was 0.3132 to -0.1050, class C was -0.1050 to -0.4196, class D was -0.4195 below. The rank of landslide hazard could be divided into classes A, B, C and D by the boundary value. In the number of slope, class A was 68, class B was 115, class C was 65, and class D was 52. The rate of landslide occurrence in class A and class B was shown at the hige prediction of 83%. Therefore, dangerous areas selected by the prediction method of landslide could be mapped for land-use planning and criterion of disaster district. And also, it could be applied to an administration index for disaster prevention.

• Journal of Korea Water Resources Association
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• v.54 no.2
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• pp.81-91
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• 2021

Synthetic Apreture Radar (SAR) is attracting attentions with its possibility of producing high resolution data that can be used for soil moisture estimation. High resolution soil moisture data enables more specific observation of soil moisture than existing soil moisture products from other satellites. It can also be used for studies of wildfire, landslide, and flood. The SAR based soil moisture estimation should be conducted considering vegetation, which affects backscattering signals from the SAR sensor. In this study, a SAR based soil moisture estimation at regions covered with various vegetation types on the middle area of Korea (Cropland, Grassland, Forest) is conducted. The representative backscattering model, Water Cloud Model (WCM) is used for soil moisture estimation over vegetated areas. Radar Vegetation Index (RVI) and in-situ soil moisture data are used as input factors for the model. Total 6 study areas are selected for 3 vegetation types according to land cover classification with 2 sites per each vegetation type. Soil moisture evaluation result shows that the accuracy of each site stands out in the order of grassland, forest, and cropland. Forested area shows correlation coefficient value higher than 0.5 even with the most dense vegetation, while cropland shows correlation coefficient value lower than 0.3. The proper vegetation and soil moisture conditions for SAR based soil moisture estimation are suggested through the results of the study. Future study, which utilizes additional ancillary vegetation data (vegetation height, vegetation type) is thought to be necessary.

• Journal of Korean Society of Forest Science
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• v.105 no.2
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• pp.223-230
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• 2016

This study was carried out to investigate the quarrying and restoration characteristics on quarry in Korea. We researched quarrying and restoration status, analyzed the relationship between restoration area and permitted period, permitted area, quarrying volume, pit slope width, height, and berm width from 55 quarry sites. Most of the quarries were located in the following conditions : mixed forest, average altitude of less than 300 m, average mountain slope of $61^{\circ}$<, hillside, granite and landslide hazard class. Major quarrying characteristics were permitted period of 6~10 years, permitted area of less than 10 ha, quarrying volume of less than $1,000,000m^3$, a stone type of aggregate, a quarrying type of terrace, pit slope of $61^{\circ}$< Most quarries were restored by themselves, and the main restoration type was slope greening. Also, area ratio of flatland, pit slope, and berm was 54.9:39.6:5.5. Ccorrelation analysis showed that quarrying area was positively correlate with quarrying volume (${\alpha}=0.01$), permitted area, pit width, and pit height (a=0.05).

• Korean Journal of Remote Sensing
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• v.36 no.5_3
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• pp.1109-1123
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• 2020

In South Korea with forest as a major land cover class (over 60% of the country), many wildfires occur every year. Wildfires weaken the shear strength of the soil, forming a layer of soil that is vulnerable to landslides. It is important to identify the severity of a wildfire as well as the burned area to sustainably manage the forest. Although satellite remote sensing has been widely used to map wildfire severity, it is often difficult to determine the severity using only the temporal change of satellite-derived indices such as Normalized Difference Vegetation Index (NDVI) and Normalized Burn Ratio (NBR). In this study, we proposed an approach for determining wildfire severity based on machine learning through the synergistic use of Sentinel-1A Synthetic Aperture Radar-C data and Sentinel-2A Multi Spectral Instrument data. Three wildfire cases-Samcheok in May 2017, Gangreung·Donghae in April 2019, and Gosung·Sokcho in April 2019-were used for developing wildfire severity mapping models with three machine learning algorithms (i.e., Random Forest, Logistic Regression, and Support Vector Machine). The results showed that the random forest model yielded the best performance, resulting in an overall accuracy of 82.3%. The cross-site validation to examine the spatiotemporal transferability of the machine learning models showed that the models were highly sensitive to temporal differences between the training and validation sites, especially in the early growing season. This implies that a more robust model with high spatiotemporal transferability can be developed when more wildfire cases with different seasons and areas are added in the future.