• Journal of the Korean Geotechnical Society
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• v.26 no.10
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• pp.27-38
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• 2010

In every summer season, most of the slope failures and debris flows occurr due to seasonal rain, typhoon, and localized extreme rainfall in Gangwon Province where 83% of the area is of mountain region. To investigate the slope-hazard triggering rainfall characteristics in Gangwon Province, slope hazard data, precipitation records, and forest fire data were collected and the DATABASE was constructed. Analysis results based on the DATABASE showed that many slope hazards occurred when there was little rainfall and the preceding rainfall had more effect on the slope hazard than the rainfall intensity at the day of hazard. It also showed that the burned area by forest fire was highly susceptible to slope hazard with low rainfall intensity, and the slope hazard in burned area showed highest frequency, especially, under the rainfall below 2-year return period.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.1
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• pp.23-32
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• 2022

In this study, rainfall water outlet water quality monitoring was performed on the C industrial complex to evaluate the characteristics of non-point pollutant runoff from the industrial complex during rainfall and to use it as basic data for calculating the load and unit of non-point pollutant. As a result of the IETD analysis, it was selected as a representative rainfall event for simulating non-point pollutants when the rainfall duration was about 21 hours and the rainfall was 26.44mm. Also as a result of monitoring the flow and water quality survey, the first rainfall was 12.2 mm, the rainfall duration was 12 hr, the number of preceding dry days was 3 days, the second rainfall was 22.1 mm, the rainfall duration was 12 hr, and the number of preceding dry days was 7 days.

• The Journal of Engineering Geology
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• v.28 no.1
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• pp.47-59
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• 2018

At present, there has been a wide range of studies on debris flow in Korea, more specifically, on rainfall characteristics that trigger debris flow including rainfall intensity, rainfall duration, and preceding rainfall. the prediction of landslide / debris flow relies on the criteria for landslide watch and warning by the Korea Forest Service (KFS, 2012). Despite this, it has been found that most incidents of debris flow were caused by rainfall above the level of landslide watch, maximum hourly rainfall, extensive damage was caused even under the watch level. Under these circumstances, we calculated a rainfall triggering index (RTI) using the main factors that trigger debris flow-rainfall, rainfall intensity, and cumulative rainfall-to design a more sophisticated watch / warning criteria than those by the KFS. The RTI was classified into attention, caution, alert, and evacuation, and was assessed through the application of two debris flow incidents that occurred in Umyeon Mountain, Seoul, and Cheongju, Inje, causing serious damage and casualties. Moreover, we reviewed the feasibility of the RTI by comparing it with the KFS's landslide watch / warning criteria (KFS, 2012).

• Journal of Environmental Science International
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• v.27 no.10
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• pp.845-851
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• 2018

In this study, the runoff characteristics of the non-rainfall period were examined using daily rainfall data from 1977 to 2017 and the data of runoff into the dam. Results showed that, the mean runoff decreases with longer non-rainfall periods in the Andong dam basin. The correlation coefficient between non-rainfall days and average runoff reaches 0.85. The results of the analysis of the runoff characteristics during the non-rainfall period, based on the preceding rainfall of Andong dam are as follows. The runoff characteristics of the entire non-rainfall period, shows that, for a rainfall of 1.0 mm or less, the runoff height was larger than the rainfall size and the base runoff larger. The correlation between the antecedent rainfall and runoff height was reached as high as 0.9864 in the 30 ~ 50 mm interval of the antecedent rainfall period, and this is the interval where the linearity of rainfall and runoff was at its maximum in the Andong dam basin. The correlation between the antecedent rainfall and the runoff height reached 0.92 for rainfalls of 100.0 mm. However, for rainfalls of 100.0 mm greater, the correlation between the antecedent rainfall and runoff height during the rainfall period was 0.64, which is relatively small. In this study, we investigated the runoff characteristics of the rainfall period in the Andong dam watershed. As a result, it was confirmed that the mean runoff decreased with rainfall duration. The linearity was found to be weak for rainfall events greater than 100.0 mm. The results of this study can be used as data for water balance analysis and for formulating a water supply plan to establish water resource management of Andong dam.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.2
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• pp.183-190
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• 1993

It is desirable to utilize the result after studying the rainfall characteristics including the latest observation data in the districts for the sake of establishment of the more accurate plans for drainage or plans for hydraulic stuctures because the rainfall phenomena are different in their characteristics by regional groups and if we make a meteorological observation for a long period of time, the rainfall characteristics also change a great deal as compared with the preceding years. Therefore, we selected only the annual maximum rainfall from the self-recording rain gauge of the main rainfall observation station (Cheju, Sogwipo, Songsanpo) in the Cheju districts in the last twenty years, extracted the rainfall by actual measurement by the rainfall duration, and induced the optimal probable rainfall-intensity formulas by regional groups in the Cheju districts, taking advantage of the rainfall formulas being in wide use in general, that is, Talbot type, Sherman type, Japanese type, and new Semi-log type. As the result, the return periods at Cheju station appeared to be three years to five years and the optimal probable rainfall-intensity formula at Cheju station, Japanese type and outside the city, Talbot type; Sogwipo, Sherman type; Songsanpo, Talbot type respectively.

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.574-578
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• 2012

This study was carried out to clarify the influences of forest environmental factors on turbidity of Stream water on three stands (Castanea crenata, Pinus densiflora and Plantation Land) of small watershed in Samgyeri Naedong-myeon Jinju-si Gyeongsangnam-do. The relationship between turbidity and forest environmental factors was a positive correlation at 1% level with chromaticity, suspended solid, sediment runoff erosion, slope, rainfall intensity, preceding dry days, watershed area and stream length and at 5% level with accumulative rainfall. The important factors that affected turbidity in small watershed showed in order of preceding dry days, rainfall intensity, stream length, chromaticity and suspended solid. In the stepwise regression between turbidity and forest environmental factors, the estimation equation is as follow; Y=-28.125+0.047x (suspended solid)+0.058x (chromaticity)+1.518x (rainfall intensity)+0.264x (stream length)+1.837x (preceding dry days). The results indicates that dangerous areas of landslide and soil runoff by land use could be applied to the mitigation measures such as afforestation, erosion check dam and revetment for erosion control and water quality management in small watershed.

• Journal of the Korean Geotechnical Society
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• v.31 no.8
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• pp.5-15
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• 2015

One-dimensional rainfall laboratory tests using gneissic weathered soil were conducted to investigate effect of antecedent rainfall on infiltration characteristics. Experimental results using samples from Chuncheon and Chungju sites showed that rainfall onto the ground surface decreased initial negative pore water pressure of unsaturated soils, which recovered gradually after the end of rainfall. Rainfall intensity increases water infiltration rate, and infiltration rate during main rainfall is faster than that of the preceding rainfall. It is considered that higher water saturation after antecedent rainfall increases water infiltration rate during main rainfall. In particular, Chungju sample with higher clay content had slower recovery of negative pore water pressure and infiltration rate. Numerical results using finite element slope stability analysis showed that reduction of initial negative pore pressure due to rainfall infiltration deteriorates slope stability, and diffusion of pore water pressure after the end of rainfall further reduces FS of the slope in the short term. Main rainfall after prior rainfall further reduced factor of safety of the unsaturated slope. Pattern of antecedent rainfall has a significant impact on the magnitude and distribution of initial pore water pressure in unsaturated soils which are controlling factor to assess factor of safety of unsaturated slope during rainfall.

• Journal of Environmental Science International
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• v.22 no.5
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• pp.555-562
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• 2013

Jeju Island, the heaviest raining area in Korea, is a volcanic Island located at the southernmost of Korea, but most streams are of the dry due to its hydrological/geological characteristics different from those of inland areas. Therefore, there are limitations in applying the results from the mainland to the studies on stream run-off characteristics analysis and water resource analysis of Jeju Island. In this study, the SWAT(soil & water assessment tool) model is used for the Hwabuk stream watershed located east of the downtown to calculate the long-term stream run-off rate, and WMS(watershed modeling system) and HEC-HMS(hydrologic modeling system) models are used to figure out the stream run-off characteristics due to short-term heavy rainfall. As the result of SWAT modelling for the long-term rainfall-runoff model for Hwabuk stream watershed in 2008, 5.66% of the average precipitation of the entire basin was run off, with 3.47% in 2009, 8.12% in 2010, and root mean square error(RMSE) and determination coefficient($R^2$) was 496.9 and 0.87, respectively, with model efficient(ME) of 0.72. From the results of WMS and HEC-HMS models which are short-term rainfall-runoff models, unless there was a preceding rainfall, the runoff occurred only for rainfall of 40mm or greater, and the run-off duration averaged 10~14 hours.

• Journal of the Korean earth science society
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• v.35 no.7
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• pp.518-528
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• 2014

In this study, a model of rainfall drop-size distribution was modified using PARSIVEL-retrieved rainfall drop-size distribution over Daegwanryeong mountainous area. A prototype model (Modified ${\Gamma}$ distribution model) applicable for this area was decided through the comparative analysis between results from models proposed by preceding research and PARSIVEL-retrieved data over Daegwanryeong mountainous area. In order to apply the prototype model for Daegwanryeong region, the parameters (${\alpha}$, A, B) were made via sensitivity experiments and models of the rainfall drop-size distributions for five cases of rainfall rate were proposed. Results from the proposed five models showed high correlations with PARSIVEL-retrieved data ($R^2=0.975$). In order to suggest a generalized form of rainfall drop-size distribution, interaction equations between rainfall rates and parameters (${\alpha}$, A, B) were investigated. The generalized model of the rainfall drop-size distribution was highly correlated with PARSIVEL-retrieved data ($R^2=0.953$), which means that the proposed model from this study was effective for simulating the rainfall drop-size distribution over Daegwanryeong region. However, the proposed model was optimized for rainfall drop-size distribution over Daegwanryeong region. Therefore, broad observations of other regions are necessary in order to develop the representative model of the Korean peninsula.

• Proceedings of the Korean Quaternary Association Conference
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• 2004.06a
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• pp.24-25
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• 2004

It is well known that there is an inverse relationship between the strength of Indian summer monsoon Rainfall (ISMR) and extent of Eurasian snow cover/depth in the preceding season. Tibetan snow cover/depth also affects the Asian monsoon rainy season largely. The positive correlation between Tibetan sensible heat flux and southeast Asian rainfall suggest an inverse relationship between Tibetan snow cover and southeast Asian rainfall. Developments in Regional Climate Models suggest that the effect of Tibetan snow on the ISMR can be well studied by Limited Area Models (LAMs). LAMs are used for regional climate studies and operational weather forecast of several hours to 3 days in future. The Eta model developed by the National Center for Environmental Prediction (NCEP), the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) and Regional Climate Model (RegCM) have been used for weather prediction as well as for the study of present-day climate and variability over different parts of the world. Regional Climate Model (RegCM3) has been widely . used for various mesoscale studies. However, it has not been tested to study the characteristics of circulation features and associated rainfall over India so far. In the present study, Regional Climate Model (RegCM-3) has been integrated from 1 st April to 30th September for the years 1993-1996 and monthly mean monsoon circulation features and rainfall simulated by the model at 55km resolution have been studied for the Indian summer monsoon season. Characteristics of wind at 850hPa and 200hPa, temperature at 500hPa, surface pressure and rainfall simulated by the model have been examined for two convective schemes such as Kuo and Grell with Arakawa-Schubert as the closure scheme, Model simulated monsoon circulation features have been compared with those of NCEP/NCAR reanalyzed fields and the rainfall with those of India Meteorological Department (IMD) observational rainfall datasets, Comparisons of wind and temperature fields show that Grell scheme is closer to the NCEP/NCAR reanalysis, The influence of Tibetan snowdepth in spring season on the summer monsoon circulation features and subsequent rainfall over India have been examined. For such sensitivity experiment, NIMBUS-7 SMMR snowdepth data have been used as a boundary condition in the RegCM3, Model simulation indicates that ISMR is reduced by 30% when 10cm of snow has been introduced over Tibetan region in the month of previous April. The existence of Tibetan snow in RegCM3 also indicates weak lower level monsoon westerlies and upper level easterlies.