• Journal of Forest and Environmental Science
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• v.32 no.2
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• pp.196-204
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• 2016

In this study, vegetation succession and the rate of consequent topsoil development were investigated in shallow landslide scars of sedimentary rock slopes covered by volcanic ashes and pumice in Kagoshima prefecture, Japan. Seven shallow landslide scars of different ages were selected as study areas. In the initial period after the occurrence of a shallow landslide, deciduous broad-leaved trees such as Mallotus japonicus or Callicarpa mollis were occupied in the areas. Approximately 30 years after the landslide, evergreen broad-leaved trees such as Cinnamomum japonicum invaded in the areas, already existed present deciduous broad-leaved trees. After 50 years, the summit of the canopy comprised evergreen broad-leaved trees such as Castanopsis cuspidata var. sieboldii and Machilus thunbergii. Moreover, the diversity of vegetation invading the site reached the maximum after 15 years, followed by a decrease and stability in the number of trees. The total basal areas under vegetation increased with time. It was concluded that the vegetation community reaches the climax stage approximately 50 years after the occurrence of a shallow landslide in the study areas, in terms of the Fisher-Williams index of diversity (${\alpha}$) and the prevalence of evergreen broad-leaved trees. Moreover, according to the results of topsoil measurement in the study areas, the topsoil was formed at the rate of 0.31 cm/year. The development of topsoil usually functions to improve the multi-faceted functions of a forest. However, when the increased depth of topsoil exceeds the stability threshold, the conditions for a shallow landslide occurrence are satisfied. Therefore, we indicated to control the depth of topsoil and strengthen its resistance by forest management in order to restrain the occurrence of shallow landslides.

• Journal of Korean Society of Forest Science
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• v.84 no.1
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• pp.31-40
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• 1995

The purpose of this study was to analyze the process of natural plant establishment and revegetation on the slopes of landslide scars, both untreated(l4 plots) and treated plots (14 plots) with rehabilitation measures in 1993 and 1994 at Yongin Hwaseong-gun region. While total of 61 species were identified at surveyed sites. in the region, the pioneer species on landslide scars were Lespedeza cyrtobotrya, Arundinella hirta, Artemisia princeps, Pteridium acquilinum, Erigeron canadensis. Rubus crataegifolius, Stephanandra incisa etc. The species diversity (H') and evenness(E') of the untreated scars were greater than those of the treated scars. Similarity indices in the untreated scars were higher than those in the treated scars, and succession indices showed similar value in both areas. As a conclusion, this study shows that the untreated scars were more influenced by the around-vegetation, and the native vegetations(plants) like Lespedeza cyrtobotrya, Arundinella hirta. Miscanthus sinensis, Artemisia princeps, Pteridium acquilinum, Erigeron canadensis. Rubus crataegifolius, Stephanandra incisa ete. could be more effectively used as plant vegetation for rehabilitation of landslide scars.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.11 no.2
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• pp.1-9
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• 2008

The objective of the study is 10 know the relation of landslide occurrence with using TPI (Topographic Position Index) in the Pyungchang County. Total 659 landslide scars were detected from aerial photographs. To analyze TPI, 100m SN (Small-Neighborhood) TPI map, 500m LN (Large-Neighborhood) TPI map, and slope map were generated from the DEM (Digital Elevation Model) data which are made from 1 : 5,000 digital topographic map. 10 classes clustered by regular condition after overlapping each TPI maps and slope map. Through this process, we could make landform classification map. Because it is only to classify landform, 7 classes were finally regrouped by the slope angle information of landslide occurrence detected from aerial photography analysis. The accuracy of reclassified map is about 46%.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.214-214
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• 2015

Rainfall induced landslides is one of the most devastating natural disasters acting on mountainous areas. In Korea, landslide damage areas increase significantly from 1990s to 2000s due to the increase of both rainfall intensity and rainy days in addition with haphazard land development. This study was carried out based on the application of TRIGRS unsaturated (Transient Rainfall Infiltration and Grid-based Regional Slope stability analysis), a Fortran coded, physically based, and numerical model that can predict landslides for areas where are prone to shallow precipitation. Using TRIGRS combining with the geographic information system (GIS) framework, the landslide incident happened on 27th, July 2011 in Mt. Umyeon in Seoul was modeled. The predicted results which were raster maps showed values of the factors of safety on every pixel at different time steps show a strong agreement with to the observed actual landslide scars in both time and locations. Although some limitations of the program are still needed to be further improved, some soil data as well as landslide information are lack; TRIGRS is proved to be a powerful tool for shallow landslide susceptibility zonation especially in great areas where the input geotechnical and hydraulic data for simulation is not fully available.

• Journal of the Korean GEO-environmental Society
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• v.17 no.4
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• pp.17-31
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• 2016

Many researchers have evaluated the influence of vegetation cover on slope stability. However, due to the extensive variety of site conditions and vegetation types, different studies have often provided inconsistent results, especially when evaluating in different regions. Therefore, additional studies need to be conducted to identify the positive impacts of vegetation cover for slope stabilization. This study used the Transient Rainfall Infiltration and Grid-based Regional Slope-stability Model (TRIGRS) to predict the occurrence of landslides in a watershed in Jinbu-Myeon, Pyeongchang-gun, Korea. The influence of vegetation cover was assessed by spatially and temporally comparing the predicted landslides corresponding to multiple trials of cohesion values (which include the role of root cohesion) and real observed landslide scars to back-calculate the contribution of vegetation cover to slope stabilization. The lower bound of cohesion was defined based on the fact that there are no unstable cells in the raster stability map at initial conditions, and the modified success rate was used to evaluate the model performance. In the next step, the most reliable value representing the contribution of vegetation cover in the study area was applied for landslide assessment. The analyzed results showed that the role of vegetation cover could be replaced by increasing the soil cohesion by 3.8 kPa. Without considering the influence of vegetation cover, a large area of the studied watershed is unconditionally unstable in the initial condition. However, when tree root cohesion is taken into account, the model produces more realistic results with about 76.7% of observed unstable cells and 78.6% of observed stable cells being well predicted.

• Journal of Korean Society of Forest Science
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• v.85 no.4
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• pp.565-570
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• 1996

The landslide survey in an area of about 10 ha was carried out in Hyuseok-dong. Youngchoon-myeon, Danyang-gun, Choongcheongbuk-do. The results showed that there were many indications on geographical changes, such as scars, depressions, upheavals, cracks and destructions of the construction features. The mean degree of slope of the study area was $28^{\circ}$. The results of surface displacement in this area showed that landslide mass is moving in the direction of SE~SEE, and horizontal and vertical movement rate of the center of moving mass was about 1.2m/year and 0.86m/year, respectively. It was estimated that the amount of the soil erosion in the cliff at the lower edge of this area was 0.823m due to the caving erosion by the Namhangang(River) from June through November, 1995.