• Journal of Korean Society of Forest Science
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• v.89 no.3
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• pp.342-355
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• 2000

This study was carried out to reveal the influence of discharge change on matters and stream water quality between pH, EC and dissolved matters obtained by observation of long-term and short-term on stream water quality and separated runoff components from stream water by using HYCYMODEL. From January in 1998 to September in 1999, it was estimated by relationships of character of water quality and discharge for the experimental watershed in Mt. Palgong. The results were summarized as follows : 1. Annual average pH values of stream water in 1998 and in 1999 were 6.48(6.22~6.89) and 6.52(5.75~7.18), respectively. The observed annual average pH values were maintaining identical values in general, but pH values decreased continuously during the four months after thinning in the experimental watershed. So thinning is suspected of the major cause for the decrease. 2. Annual average EC values of stream water in 1998 and in 1999 were $26.69(17.95{\sim}33.5){\mu}S/cm$ and $25.19(17.5{\sim}33.8){\mu}S/cm$, respectively. The observed annual average EC values were maintaining identical values in general. 3. As a result of the comparison of average dissolved ions of rainfall and stream water, $Na^+$, $Mg^{2+}$, $Ca^{2+}$, $Cl^-$, $NO_3{^-}$, and $SO_4{^{2-}}$ showed minus values between incomings and outgoings. $Na^+$ and $NO_3{^-}$ among the dissolved ions of stream water showed the highest concentration out of cations and anions respectively. 4. By the change of pH value in stream water due to rainfall events, pH value decreased with increasing runoff as pH value increased before and after peak flow. 5. By the change of EC value in stream water due to rainfall events, EC value decreased with increasing runoff of first rainfall as EC value changed with runoff before and after peak flow. 6. As the runoff increased, the concentration of $Na^+$, $Ca^{2+}$, $K^+$, total cation, $Cl^-$, and $SO_4{^{2-}}$ in stream water lowered. On the other hand, the runoff decreased, their concentration in stream water tended to get high. But in terms of $NO_3{^-}$ and total anion, they turned out vice versa. $Mg^{2+}$ produced no reaction. 7. The base flow among runoff components separated by using HYCYMODEL influenced greatly on pH, EC, concentration of cation and anion.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.3
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• pp.337-352
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• 2023

In general, Rainfall-Runoff model parameter set is optimized using the entire data to calculate unique parameter set. However, Korea has a large precipitation deviation according to the season, and it is expected to even worsen due to climate change. Therefore, the need for hydrological data considering seasonal characteristics. In this study, we conducted regional sensitivity analysis(RSA) using the conceptual Rainfall-Runoff model, GR4J aimed at the Soyanggang dam basin, and clustered combining the RSA results with hydrometeorological data using Self-Organizing map(SOM). In order to consider the climate characteristics in parameter estimation, the data was divided based on clustering, and a calibration approach of the Rainfall-Runoff model was developed by comparing the objective functions of the Global Optimization method. The performance of calibration was evaluated by statistical techniques. As a result, it was confirmed that the model performance during the Cold period(November~April) with a relatively low flow rate was improved. This is expected to improve the performance and predictability of the hydrological model for areas that have a large precipitation deviation such as Monsoon climate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3B
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• pp.193-201
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• 2012

In the last decade, heavy rainfall induced debris flow events have been remarkably occurred in Korea. Consequently, debris flow is becoming one of the most dangerous natural phenomena in mountainous area. Understanding and correct predicting of the runout distance of debris flow is an essential prerequisite for developing debris flow hazard map and prevention technology. Based on the simple and widely used sled model, in this study, we analyse the net efficiency of debris flows which is a dimensionless constant (=1/R) and defined by the ratio of the horizontal runout distance L from the debris flow source to deposit and the vertical elevation H of the source above the deposit. The analysis of field data observed in total 238 debris flow events occurred from 2002 to 2011 reveals that the representative value of the net efficiency of debris flows in Korea is 4.3. The data observed in Gangwon province where is the most debris flow-prone area in Korea shows that debris flows in Inje area have the runout distance longer than those in Pyongchang and Gangneung. Overall features of the net efficiency of debris flows observed in the central Korea are similar to those in the southern Korea. The estimation based on aerial photographs and available depositional conditions appears to overestimate the net efficiency compared to estimation based on the field observations, which indicates that appropriate depositional conditions need to be developed for debris flows in Korea.

• The Journal of Engineering Geology
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• v.24 no.4
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• pp.501-510
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• 2014

Volcanic eruptions alone may lead to serious natural disasters, but the associated release of water from a caldera lake may be equally damaging. There is both historical and geological evidence of the past eruptions of Mt. Baekdusan, and the volcano, which has not erupted for over 100 years, has recently shown signs of reawakening. Action is required if we are to limit the social, political, cultural, and economic damage of any future eruption. This study aims to identify the area that would be inundated following a volcanic flood from the Cheon-Ji caldera lake that lies within Mt. Baekdusan. A scenario-based numerical analysis was performed to generate a flood hydrograph, and the parameters required were selected following a consideration of historical records from other volcanoes. The amount of water at the outer rim as a function of time was used as an upper boundary condition for the downstream routing process for a period of 10 days. Data from the USGS were used to generate a DEM with a resolution of 100 m, and remotely sensed satellite data from the moderate-resolution imaging spectroradiometer (MODIS) were used to show land cover and use. The simulation was generated using the software FLO-2D and was superposed on the remotely sensed map. The results show that the inundation area would cover about 80% of the urban area near Erdaobaihezhen assuming a 10 m/hr collapse rate, and 98% of the area would be flooded assuming a 100 m/hr collapse rate.

• Journal of Korea Water Resources Association
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• v.36 no.4
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• pp.521-531
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• 2003

Pollutant load to Yongdam Reservoir considering rainfall effect is estimated using data collected during dry and wet days between Dec 1998 and Oct. 1999. Limit of significant rainfall was assumed to be as 10 mm/day and numbers of days of significant rainfall for each month were counted using 10 years of meteorological data of the study area. Water quality input concentrations were estimated by taking weighted averages of concentrations in dry and wet days in each month. The resulting concentrations were used as inputs for water quality modeling of Yongdam Reservoir. When rainfall effect was included average reservoir concentrations of BOD, TN and TP were increased by 70％, 5％ and 27％, respectively Considering the fact that Korea is under the significant influence of monsoon effect during the summer, it should be important to include rainfall effect in estimating pollutant input to receiving waters. This method is expected to increase reliability of annual water quality modeling results by providing realistic input data.

• Journal of Korea Water Resources Association
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• v.50 no.11
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• pp.745-758
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• 2017

The copula-based models have been successfully applied to hydrological modeling including drought frequency analysis and time series modeling. However, uncertainty estimation associated with the parameters of these model is not often properly addressed. In these context, the main purposes of this study are to develop the Bayesian inference scheme for bivariate copula functions. The main applications considered are two-fold: First, this study developed and tested an approach to copula model parameter estimation within a Bayesian framework for drought frequency analysis. The proposed modeling scheme was shown to correctly estimate model parameters and detect the underlying dependence structure of the assumed copula functions in the synthetic dataset. The model was then used to estimate the joint return period of the recent 2013~2015 drought events in the Han River watershed. The joint return period of the drought duration and drought severity was above 100 years for many of stations. The results obtained in the validation process showed that the proposed model could effectively reproduce the underlying distribution of observed extreme rainfalls as well as explicitly account for parameter uncertainty in the bivariate drought frequency analysis.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.163-173
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• 2022

Climate change is a key factor that greatly influences changes in the biological seasons and geographical distribution of species. In the ecological field, the BioClimatic predictor (BioClim), which is most related to the physiological characteristics of organisms, is used for vulnerability assessment. However, BioClim values are not provided other than the future period climate average values for each GCM for the Shared Socio-economic Pathways (SSPs) scenario. In this study, BioClim data suitable for domestic conditions was produced using 1 km resolution SSPs scenario detailed data produced by Rural Development Administration, and based on the data, a species distribution model was applied to mainly grow in southern, Gyeongsangbuk-do, Gangwon-do and humid regions. Appropriate habitat distributions were predicted every 30 years for the base years (1981 - 2010) and future years (2011 - 2100) of the Acer pictum subsp. mono. Acer pictum subsp. mono appearance data were collected from a total of 819 points through the national natural environment survey data. In order to improve the performance of the MaxEnt model, the parameters of the model (LQH-1.5) were optimized, and 7 detailed biolicm indices and 5 topographical indices were applied to the MaxEnt model. Drainage, Annual Precipitation (Bio12), and Slope significantly contributed to the distribution of Acer pictum subsp. mono in Korea. As a result of reflecting the growth characteristics that favor moist and fertile soil, the influence of climatic factors was not significant. Accordingly, in the base year, the suitable habitat for a high level of Acer pictum subsp. mono is 3.41% of the area of Korea, and in the near future (2011 - 2040) and far future (2071 - 2100), SSP1-2.6 accounts for 0.01% and 0.02%, gradually decreasing. However, in SSP5-8.5, it was 0.01% and 0.72%, respectively, showing a tendency to decrease in the near future compared to the base year, but to gradually increase toward the far future. This study confirms the future distribution of vegetation that is more easily adapted to climate change, and has significance as a basic study that can be used for future forest restoration of climate change-adapted species.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.129-136
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• 2008

The purpose of this study is to find an effective operating system for water supply of Andong Dam. The reliability of water supply was assessed by HEC-5 model based on operated water supply data of Andong Dam and data of Jin-dong water level gauge station in Nak- dong river. In addition, estimated additional amount of water supply was evaluated for each alternative by additional retention of Andong Dam in rainy season from June to September. As the result, additional amount of water supply of each alternative in non-rainy season (excluding rainy season) is increased as $1.35m^3/s{\sim}2.12m^3/s$, it shows that additional amount of water supply can be made by effective operating system for water supply in every dam as Andang Dam.

• Journal of Korea Water Resources Association
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• v.34 no.1
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• pp.3-17
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• 2001

The purpose of this study is to understand applicabilities of sediment yield estimation technique with observed data in the field accelerated by human activity. Commonly used equations such as Universal Soil Loss Equation and Transport Research Board etc. from foreign country is not validated. And analyzing affecting parameters and understanding limit of each estimation technique is not examined, either. To test the applicabilities of several models, a hot spring development site in Chunahn city, Chungnam province is selected. Sediment yield of catchment is determined using RVSLE, TRB, MUSLE, SLEMA, and Morgan & Finned method and compared to actual measurement. It is found that RUSLE and TRB are overestimated and MUSLE dives a rotatively resonable value.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.94-97
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• 2009

연 및 계절강수량의 정확한 예보는 수자원관리에 매우 중요하다. 예보 정확도를 높이기 위한 다양한 연구가 계속 진행되어 왔다. 그럼에도 불구하고 강수자료가 가지는 매우 큰 불확실성 때문에 예보의 정확도 향상은 계속되는 숙제로 우리에게 남아 있다. 이를 개선하기 위하여 본 연구에서는 군집화 기법을 이용한 연 및 계절 강수량 예측개선에 대한 연구 결과를 제시하였다. 이를 위하여 연강수량, 계절강수량 및 월강수량의 예측을 위하여 전구에서 일어나는 각종 기후 인자들과의 상관성 분석은 대단히 중요하다. 전 세계적으로 어느 특정 지역에서의 선행 기후인자 변화 양상이 우리나라의 강수량에 높은 상관성을 가지며 영향을 미친다면 예측을 위한 매우 유용한 정보라 하겠으나 국내 강수량과 기후 지수 사이의 선형 상관성은 매우 낮을 뿐만 아니라 지체상관성도 특정 지체에서 매우 큰 상관성을 보이는 인자를 찾기 어려움을 알 수 있다. 이를 극복하기 위하여 본 연구에서는 k-mean clustering을 이용하여 우리나라 주변의 기후조건을 분류하고 기후조건에 따른 강수량의 변화를 분석하였다. 남중국해역($105^{\circ}E\;^{\sim}\;135^{\circ}E$, $0^{\circ}N\;^{\sim}\;35^{\circ}N$), 우리나라 연안 해역 ($110^{\circ}E\;^{\sim}\;150^{\circ}E$, $20^{\circ}N\;^{\sim}\;40^{\circ}N$), 인도양 해역 ($75^{\circ}E\;^{\sim}\;105^{\circ}E$, $0^{\circ}N\;^{\sim}\;25^{\circ}N$) 및 아라비아 해역 ($45^{\circ}E\;^{\sim}\;75^{\circ}E$, $0^{\circ}N\;^{\sim}\;30^{\circ}N$ 평균 해수면 온도 변화에 따라 8개 군집으로 분류한 분석결과로 분석결과 2008년도는 그룹 5에 해당하며 그룹 5의 기후 상태는 근해와 남중국해역의 평균 해수면 온도가 평년보다 낮고 인도양 해역과 아라비아 해역의 평균 해수면 온도는 평년값과 비슷한 상태를 나타낸다. 그룹 5에 해당하는 기후조건에서 차년의 강수평균은 평년값 보다 적음을 보였다. 이러한 특성은 전체 유역에 걸쳐 동일하게 나타났다. 이에 대한 계절적 평균 분포는 군집 5에 대한 차년도 강수의 평균 계절분포는 전체적으로 평년값보다 낮게 나타났다. 이에 근거하여 올해 연 평균 강수량은 평년값보다 적을 것이며 전체 계절에 대하여도 평년값보다 적은 강수량이 올 것으로 판단된다. 이는 기상청의 2009년 봄철 기후전망과 유사한 예측 결과를 보여준다.