• Journal of the Korean Association of Geographic Information Studies
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• v.7 no.2
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• pp.47-56
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• 2004

The purpose of this study is to estimate soil loss amount according to the rainfall-runoff erosivity factor frequency and to analyze the hazard zone that has high possibilities of soil erosion in the watershed. RUSLE was used to analyze soil loss quantity. The study area is Gwanchon that is part of Seomjin river basin. To obtain the frequency rainfall-runoff erosivity factor, the daily maximum rainfall data for 39 years was used. The probability rainfall was calculated by using the Normal distribution, Log-normal distribution, Pearson type III distribution, Log-Pearson type III distribution and Extreme-I distribution. Log-Pearson type III was considered to be the most accurate of all, and used to estimate 24 hours probabilistic rainfall, and the rainfall-runoff erosivity factor by frequency was estimated by adapting the Huff distribution ratio. As a result of estimating soil erosion quantity, the average soil quantity shows 12.8 and $68.0ton/ha{\cdot}yr$, respectively from 2 years to 200 years frequency. The distribution of soil loss quantity within a watershed was classified into 4 classes, and the hazard zone that has high possibilities of soil erosion was analyzed on the basis of these 4 classes. The hazard zone represents class IV. The land use area of class IV shows $0.01-5.28km^2$, it ranges 0.02-9.06% of total farming area. Especially, in the case of a frequency of 200 years, the field area occupies 77.1% of total fanning area. Accordingly, it is considered that soil loss can be influenced by land cover and cultivation practices.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.687-696
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• 2006

Slope failure triggered by rainfall produces severe effects on the serviceability and stability of railway. Therefore slope stability problem is one of the major concerns on the operation of railway. In this study we collected rainfall data when and where slope failures were observed. The collected data show that the range of cumulative rainfall is from 150 to 500mm and the rainfall duration is about 3 to 24 hours. By using the collected rainfall information, slope stability analysis considering infiltration was carried. The analyses employs multiple sliding surfaces to find the minimal factor of safety in the infinite slope condition. This approach show more reasonable results than the results from analysis following the design code which assumes that groundwater level and the slope surface are equal.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.273-280
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• 2001

In order to evaluate the stability of railway cut-slope under rainfall, explanatory variables and subordinate variables were selected for multivariate analysis. Furthermore the site which had occurred failure due to rainfall was investigated, and by executing multivariate analysis for 121 cases, critical rainfall was defined by the case that had high value of correlation factor. The 0.3 square value of maximum hourly rainfall during 24 hours before failure caused the collapse of railway cut-slope and could be used to estimate the stability of railway cut-slope. From the result of application to a collapse example, the evaluaton method by critical rainfall curve is satisfactory.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.257-265
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• 2012

Since the collapse of MSE walls frequently occurs due to the rainfall, it is necessary to analyze the behavior of MSE wall depending on the characteristics of rainfall and the properties of permeability of backfill. In order to understand the behavior of MSE wall depending on the characteristics of rainfall and the properties of permeability of backfill, finite element analyses were performed on the typical MSE wall. With varying ratio of saturated permeability to rainfall intensity, porepressures, displacements and factor of safety were analyzed. As the ratio of the saturated permeability to rainfall intensity increases, the global factor of safety is found to increase. Based on the analyses, the use of permeability of backfill with $2.56{\times}10^{-5}m/sec$ is desirable considering the characteristics of rainfall in Korea.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.71-78
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• 2010

The stability analysis of unsaturated infinite slope under rainfall-induced infiltration condition was performed using the generalized effective stress that unifies both saturated and unsaturated condition recently proposed by Lu and Likos(2004, 2006). The Soil-Water Characteristic Curve (SWCC) of the sand with the relative density of 75% was first measured for both drying and wetting processes. The Hydraulic Conductivity Function (HCF) and Suction Stress Characteristic Curve (SSCC) were subsequently estimated. Also, under the rainfall-induced infiltration condition transient seepage analysis of unsaturated infinite slope was performed using the finite element program, SEEP/W. Based on these results, the stability of unsaturated infinite slope under rainfall-induced infiltration condition was examined considering the suction stress. According to the results, the negative pore water pressure and water content within the soil changed with time due to the infiltration. Also, the variation of those caused the variation of suction stress and then the factor of safety of slope changed consequently during the rainfall period.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.893-903
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• 2008

A method for predicting surface failures which occur during heavy rainfall on mountain slopes is proposed by using the digital land form model that is obtained by reading altitude on a topographical map at 10m grid point space. A depth of a potential failure layer is assumed at each grid point. In the layer, an infiltrated water movement from cell to cell is modeled in the study (cell is a square of the grid). Infiltrated ground water levels which show the three dimensional effects of a topographical factor in an area can be hourly calculated at every cell by the model. The safety factor of every cell is also calculated every hour by the infinite slope stability analysis method with the obtained infiltrated ground water level. Failure potential delineation is defined here as the time when the safety factor becomes less than unity under the assumptions that effective rainfall is 20mm/h and continues 20 hours.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.1
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• pp.13-19
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• 2014

The management of non point sources was marked by the need for clean water environments. It was proposed the fundamentals to promote the reasonable land management in this study. We monitored rainfall events at two non point sources with different crop cultivations such as a sweet potato and a cherry tree for three years. Because the most important factor was rainfall, the rainfall runoff and pollutant loads were generated 100% in the case of rainfall ranges with 50 < rainfall (mm). However the frequency of rainfall runoff was interacted with the crop cultivation and soil characteristics in the case of rainfall ranges such as 30 < rainfall (mm) ${\leq}50^a$ and 10 < rainfall (mm) ${\leq}30^b$. The frequency of rainfall runoff was a : 60% and b : 5% in the cherry tree cultivation with growing significantly and pollutant loads were lower than that of the sweet potato cultivation. Meanwhile the frequency of rainfall runoff was a : 60% and b : 5% in the sweet potato cultivation.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.501-504
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• 2007

Slope-related disasters have occurred in the rainy season. It can be assumed that one of the most important factor slope-related disasters is rainfall intensity. Slope-related disasters occurred in relatively short time and had characteristics that lead to huge damage. Therefore, if rainfall characteristics were applied to estimate slope stability effectively, slope-related disasters could be predicted and prepared in advance. In this study, the SEEP/W program was used and the frequency rainfall estimated by using precipitation data($1961{\sim}2005$) in Seoul was applied to analyze the change of groundwater level according to rainfall intensity.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.402-409
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• 2000

In order to evaluate the stability of railway embankment under rainfall, explanatory variables and subordinate variables wet-e selected for multivariate analysis. Furthermore the site which had occurred failure due to rainfall was investigated, and by executing multivariate analysis for 121 cases, critical rainfall was defined by the case that had high value of correlation factor. The maximum hourly rainfall during 24 hours before failure caused the collapse of railway embankment and could be used estimate the stability of railway embankment. From the result of application to a collapse example, the evaluation method by critical rainfall curve is satisfactory.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.643-646
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• 2006

An operational calibration is applied to improve radar rainfall intensity using rainfall obtained from rain gauge. The method is applied under the assumption of the temporal continuity of rainfall, the rainfall intensity from rain gauge is linearly related to that from radar. The method is applied to the cases of typhoon and rain band using the reflectivity of CAPPI at 1.5km obtained from Jindo radar. The CAPPI is obtained by bilinear interpolation. For the two cases, the rainfall intensities obtained by operational calibration are very consistent with the ones by the rain gauges. The present study shows that the correlation between the rainfall intensity by operational calibration and rain gauges is better than the one between the rainfall intensity by M-P relationship and rain gauges. The correlation coefficients between the total rainfall intensity obtained by operational calibration and rain gauges in typhoon and rain band cases are 0.99 and 0.97, respectively. Areal rainfalls are estimated using the field of calibration factor interpolated by Barnes objective analysis. The method applied here shows an improvement in the areal rainfall estimation. For the cases of typhoon and rain band, the correlation between the areal rainfall by operational calibration and rain gauges is better than the one between the area rainfall by M-P relationship and rain gauges. The correlation coefficients between the areal rainfall obtained by operational calibration and rain gauges in typhoon and rain band cases are 0.97 and 0.84, respectively. The present study suggests that the operational calibration is very useful for the real-time estimation of rainfall intensity and areal rainfall.