• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.438-438
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• 2022

본류와 지류가 만나는 하천의 합류부는 물의 흐름에 변화가 생겨 수면 변화가 상류에 미치는 배수현상이 나타난다. 또한 한강과 평창강이 만나는 영월 지역의 경우 각 유역 면적이 비슷하기 때문에 홍수 사상에 따라 상호 배수 영향을 주어 상류 수위에 영향을 준다. 그러므로 하천 유량을 산정하는 기존 방법인 수위-유량관계곡선(stage-discharge relation curve)을 이용한 환산 유량은 실제 측정 유량과 차이가 있다. 본 연구에서는 2021년 강우 사상에 따른 영월군(영월대교) 지점, 영월군(팔괴교) 지점 간 수위관측소 수위 비교, 각 지점의 수위관측소 수위와 유량관측소 수위 비교, 각 지점의 수위-지표유속관계를 분석하여 기간별 상호 배수 영향을 검토하였고, 연속적으로 유속을 직접 측정하여 얻은 유속과 평균유속 간의 관계를 이용한 지표유속법(index velocity method)의 적용을 검토하였다. 검토 결과 배수 영향 발생 시 지표유속법을 이용하여 산정된 유량과 수위-유량관계곡선식으로 산정된 유량 간의 차이가 발생하였고, 배수 영향 기간에는 지표유속법을 활용하여 유량을 산정하는 것이 타당한 것으로 분석되었다.

• Journal of the Korean earth science society
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• v.33 no.2
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• pp.148-161
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• 2012

The intensive observation (ProbeX-2010) with 6-hour launches of radiosonde was performed over Seoul metropolitan area (Dongducheon, Incheon Airport, and Yangpyeong) from 13 Aug. to 3 Sep. 2010. Five typical heavy rainfall patterns occurred consecutively which are squall line, stationary front, remote tropical cyclone (TC), tropical depression, and typhoon patterns. On 15 Aug. 03 KST, when squall line developed over Seoul metropolitan area, dry mid-level air was drawn over warm and moist low-level air, inducing strong convective instability. From 23 to 26 Aug and from 27 to 29 Aug. Rainfall event occurred influenced by stationary front and remote TC, respectively. During the stationary frontal rainy period, thermal instability was dominant in the beginning stage, but dynamic instability became strong in the latter stage. Especially, heavy rainfall occurred on 25 Aug. when southerly low level jet formed over the Yellow Sea. During the rainy period by the remote TC, thermal and dynamic instability sustained together. Especially, heavy rainfall event occurred on 29 Aug. when the tropical air with high equivalent potential temperature (>345 K) occupied the deep low-middle level. On 27 Aug. and 2 Sep. tropical depression and typhoon Kompasu affected Seoul metropolitan area, respectively. During these events, dynamic instability was very strong.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.553-562
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• 2017

In these days, agricultural reservoirs are considered as a useful resource for recreational purposes, tour and cultural amenity for vicinity communities as well as irrigation water supply. However, many of the agricultural reservoirs are showing a eutrophic or hyper-eutrophic state and high level of organic contamination. In particular, about 44.7% of the aged agricultural reservoirs that constructed before 1945 exceed the water quality criteria for irrigational water use. In addition to external loading, internal nutrient loading from bottom sediment may play an important role in the nutrient budget of the aged reservoirs. The objectives of this study were to characterize variations of thermal structure of a shallow M reservoir (mean depth 1.7 m) and examine the potential of internal nutrient loading by continuous monitoring of vertical water temperature and dissolved oxygen (DO) concentration profiles in 2015 and 2016. The effect of internal loading on the total loading of the reservoir was evaluated by mass balance analysis. Results showed that a weak thermal stratification and a strong DO stratification were developed in the shallow M Reservoir. And, dynamic temporal variation in DO was observed at the bottom of the reservoir. Persistent hypoxic conditions (DO concentrations less than 2 mg/L) were established for 87 days and 98 days in 2015 and 2016, respectively, during the no-rainy summer periods. The DO concentrations intermittently increased during several events of atmospheric temperature drop and rainfall. According to the mass balance analysis, the amount of internal $PO_4-P$ loading from sediment to the overlying water were 37.9% and 39.7% of total loading during no-rainy season in 2015 and 2016, respectively on August when algae growth is enhanced with increasing water temperature. Consequently, supply of DO to the lower layer of the reservoir could be effective countermeasure to reduce nutrient release under the condition of persistent DO depletion in the bottom of the reservoir.

• Korean Journal of Ecology and Environment
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• v.47 no.2
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• pp.116-126
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• 2014

To evaluate the relationship between dynamics of Cyanobacterial bloom and rainfalls, a monthly monitoring of water quality and phytoplankton from the three serial lakes (Lake Ui-am, Lake Chung-pyeong and Lake Pal-dang) in the North Han River System were examined 12 times from May 2012 to March 2013. A dense bloom of cyanobacterium Anabaena spp., was occurred over three lakes in the summer season of 2012. In Lake Ui-am, the Anabaena population appeared in June, showed a peak in July (43,850 cells $mL^{-1}$) and disappeared in November 2012. In Lake Chung-pyeong and Lake Pal-dang, Anabaena population commonly appeared in July, showed the peaks (31,648 cells $mL^{-1}$ and 7,136 cells $mL^{-1}$, respectively) in August, and entirely disappeared in September 2012. Over the three lakes, the phytoplankton community was commonly dominated by diatoms before Monsoon, cyanobacteria during Monsoon, and diatoms after Monsoon, respectively, indicating a Monsoon-dependent succession. A correlation analysis revealed that dynamics of Anabaena population was strongly related with rainfall (r=0.72, r=0.83, r=0.88, P<0.01 for three lakes), and partly with nutrients, inflow and outflow of lakes. Therefore, this study indicates that the outbreak and destruction of Anabaena bloom in North Han River System between 2012 and 2013 was impacted by rainfalls. However, a high density of cyanobacteria in Lake Ui-am remained after Monsoon, and thus, may paroduce bad-order and toxins from phytoplankton.

• Journal of Korea Water Resources Association
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• v.53 no.7
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• pp.493-505
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• 2020

The rainfall-runoff model has been generally adopted to obtain a consistent runoff sequence with the use of the long-term ground-gauged based precipitation data. The Thiessen polygon is a commonly applied approach for estimating the mean areal rainfall from the ground-gauged precipitation by assigning weight based on the relative areas delineated by a polygon. However, spatial bias is likely to increase due to a sparse network of the rain gauge. This study aims to generate continuous runoff sequences with the mean areal rainfall obtained from radar rainfall estimates through a PRMS rainfall-runoff model. Here, the systematic error of radar rainfall is corrected by applying the G/R Ratio. The results showed that the estimated runoff using the corrected radar rainfall estimates are largely similar and comparable to that of the Thiessen. More importantly, one can expect that the mean areal rainfall obtained from the radar rainfall estimates are more desirable than that of the ground in terms of representing rainfall patterns in space, which in turn leads to significant improvement in the estimation of runoff.

• Journal of Korea Water Resources Association
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• v.39 no.8 s.169
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• pp.669-676
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• 2006

Hydrological factors, especially the spatial distribution of interpretation on precipitation is often topic of interest in studying of water resource. The popular methods such as Thiessen method, inverse distance method, and isohyetal method are limited in calculating the spatial continuity and geographical characteristics. This study was intended to overcome those limitations with improved method that will yield higher accuracy. The monthly and yearly precipitation data were produced and compared with the observed daily precipitation to find correlation between them. They were then used as secondary variables in Co-kriging method, and the result was compared with the outcome of existing methods like inverse distance method and kriging method. The comparison of the data showed that the daily precipitation had high correlation with corresponding year's average monthly amounts of precipitation and the observed average monthly amounts of precipitation. Then the result from the application of these data for a Co-kriging method confirmed increased accuracy in the modeling of spatial distribution of precipitation, thus indirectly reducing inconsistency of the spatial distribution of hydrological factors other than precipitation.

• Journal of Korea Water Resources Association
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• v.30 no.6
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• pp.575-585
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• 1997

A daily runoff system was constructed to support decision making for water use in the downstream region of multipurpose dams in the Han River. The daily runoff system used the modified model from NWSRFS by Tabios III et al. (1986), and potential evapotranspiration was computed from Penman equation. DWOPER was used for channel routing. While the North Han River is the main river reach in the channel routing system, the South Han River and the Soyang River became tributaries. The rainfall-runoff model was calibrated and verified for five subbasins. Daily runoffs were simulated with the hydrometeorological data in 1986 and1990. The simulations were performed from April to November, and the sum of computed discharges for seven or thirty days were compared with actual releases of the downstream dams. It showed the average absolute errors of 8.7 ~31.6%. The sum of total discharges were 10% or less. While stage errors were produced by 0.5 m or less at Yoju station in the ease of simulation from April to August in 1986, the errors kept under 0.2 m since September. In the simulation for 1990, we compared two simulation results. One is produced from real internal and downstream boundary conditions and the other is one from internal and downstream boundary conditions fixed arbitrarily. The two cases showed similar results.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.79-88
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• 2007

This study evaluated the statistical stationarity of rainfall quantiles as well as the rainfall itself. The conventional methodologies like the Cox-Stuart test for trend and Dickey-Fuller test for a unit root used for testing the stationarity of a time series were applied and evaluated their application to the rainfall quantiles. As results, first, no obvious increasing or decreasing trend was found for the rainfall in Seoul, which was also found to be a stationary time series based on the Dickey-Fuller test. However, the Cox-Stuart test for the rainfall quantiles show some trends but not in consistent ways of increasing or decreasing. Also, the Dickey-Fuller test for a unit root shows that the rainfall quantiles are non-stationary. This result is mainly due to the difference between the rainfall data and rainfall quantiles. That is, the rainfall is a random variable without any trend or non-stationarity. On the other hand, the rainfall quantiles are estimated by considering all the data to result in high correlation between their consecutive estimates. That is, as the rainfall quantiles are estimated by adding a stationary rainfall data continuously, it becomes possible for their consecutive estimates to become highly correlated. Thus, it is natural for the rainfall quantiles to be decided non-stationary if considering the methodology used in this study.

• Journal of Korea Water Resources Association
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• v.46 no.4
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• pp.425-437
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• 2013

This study performed the bivariate drought frequency analysis for duration and severity of drought, using copula functions which allow considering the correlation structure of joint features of drought. We suggested the confidence intervals of duration-severity-frequency (DSF) curves for the given drought duration using stochastic scheme of monthly rainfall generation for 57 sites in Korea. This study also investigated drought risk via illustrating the largest drought events on record over 50 and 100 consecutive years. It appears that drought risks are much higher in some parts of the Nakdong River basin, southern and east coastal areas. However, such analyses are not always reliable, especially when the frequency analysis is performed based on the data observed over relatively short period of time. To quantify the uncertainty of drought frequency curves, the droughts were filtered by different durations. The 5%, 25%, 50%, 75%, and 95% confidence intervals of the drought severity for a given duration were estimated based on the simulated rainfall time series. Finally, it is shown that the growing uncertainties is revealed in the estimation of the joint probability using the two marginal distributions since the correlation coefficient of two variables is relatively low.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.296-296
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• 2008

국내 절토비탈면은 이상 기후 및 건설공사의 증대로 인해 증가하고 있는 추세이며 장마철 및 태풍으로 인해 비탈면의 붕괴로 많은 인명 및 재산피해가 발생되고 있는 실정이다. 국내에서 사용되고 있는 기존의 비탈면의 설계기준은 암반의 불연속면에 대한 조사를 실시하고는 있지만 주로 암반의 굴착난이도를 토층, 리핑암, 발파암으로 구분하여 각각의 비탈면 절취경사를 결정하여 사용하는 방법을 사용하였으며 이러한 기준은 단순히 암석의 강도를 기준으로 설정되어 있으므로 암석의 공학적 특성 즉, 암반내 불연속면 방향성, 연속성, 충진물질, 마찰각, 풍화속도 등의 영향으로 공용후 비탈면 구배의 재조정 및 보강이 빈번하다. 국내외 절토비탈면의 설계기준은 각 기관별로 산재되어 있었으며 비탈면에 대한 설계 및 시공 등에 관한 기준은 도로와 철도 설계기준에 일부 반영되어 있을 뿐 항만, 댐, 택지조성 등 기타 시설 설계기준에는 비탈면에 대한 기준이 마련되어 있지 않아 표준적인 비탈면 설계기준 및 유지관리지침이 등이 필요하였다. 이러한 문제점을 보완하기 위해 2004년부터 2006까지 한국시설안전공단, 한국도로공사, 대한주택공사가 협동으로 연구한 건설공사 비탈면 설계 시공 및 유지관리에 관한 연구의 결과로 2006년도에 "건설공사 비탈면 설계기준"이 수립되었다. 이 설계기준은 건설공사에서의 기존 상이한 기준들을 정리하고 동일화하는 작업을 수행하였으며 지반의 조사에서부터 대책공까지를 막나하여 정리하였다. 그러나 최근에 급격한 기후변화로 인한 비탈면붕괴 빈번함에 따라 과거 적용되어 왔던 이들 기준을 적용하는 경우, 특히 상부 토층 및 풍화암 구간에서 많은 설계안전율을 만족하지 못해 많은 보강을 수반해야 하는 문제가 발생되고 있어 그 원인에 대한 분석을 수행하고자 하였다. 2006년도 정리된 기준은 과거에 적용하여 온 유기시의 안전율 조건을 Fs > 1.1~1.2을 적용하였던 것을 Fs > 1.2로 통일하였으며 지하수위 조건은 지표면에 위치하도록 하였다. 지하수위 조건은 풍화암 및 토층의 경우, 과거 지표면에 -3m를 적용한 시기가 있었으나 지표면에 지하수위를 적용하는 것이 일반적인 해석방법이다. 이러한 결과의 원인을 검토해 보면 다음과 같다. 첫째, 풍화암 및 토층에 적용되어 온 지반강도 정수가 과거 적용한 값보다 최근에는 작아지는 경향을 보이고 있다. 둘째, 지하수위 적용문제로 현재 지표면에 지하수위를 두어 안전율을 감소시키는 문제로 이는 최근 들어 많은 연구기관에서 강우시 간극수압의 증가에 대한 연구가 활발하게 진행되고 있다. 그러나 침투수 해석은 현행 기준에도 강우의 침투를 고려한 해석을 실시하는 경우 FS > 1.3 적용하는 것으로 되어 있으나 대부분의 해석에서는 적용이 되지 못하고 있는 실정이다. 셋째, 안전율이 과거에 주로 적용된 Fs > 1.1에서 Fs > 1.2로 상향 조정되어 우기시의 설계안전율 만족시키지 못하는 문제이다. 그러므로 이러한 문제점을 개선하기 위한 검토가 필요하며 장기적으로 이에 대한 합리적인 기준을 개정하는 작업이 추후에 수행되어야 할 것으로 판단된다.