• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.264-269
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• 2002

The wave profiles of directional breaking waves are investigated experimentally in a directional wave basin. The directional breaking waves are generated by component wave focusing both in direction and frequency based on constant wave steepness and constant wave amplitude spectrum models. the profile parameters of wave crest steepness and asymmetry are adapted to analyze the evolution of breaking ware characteristics in a view of focusing efficiency. The generated breaking waves are classified into the incipient, single and multi breaking waves.

• 대한원격탐사학회지
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• 제5권1호
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• pp.13-27
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• 1989

In recent years satellite data have been increasingly used for the analysis of floodprone areas. This study was carried out to demonstrate the usefulness of repetitive satellite imagery in monitoring flood levels of the Pyungchang watershed. Runoff characteristics parameters were analyzed by Soil Conservation Service(SCS) Runoff Curve Number(RCN) based on Landsat imagery and Digital Terrain Model data. The RCN average within the watershed was calculated from RCN estimates for all the pixels(picture elements) and adjusted by antecedent precipitation conditions. The direct runoff hydrograph was derived from the unit hydrograph using SCS dimensionless unit hydrograph and effective rainfalls estimated by the SCS method. In comparsion of the direct runoff hydrograph with the measured rating curve their peak times differ by one hour and peak discharges differ by 5.9 percents of the discharge from each other. It was shown that repetitive satellite image could be very useful in timely estimating watershed runoffs and evaluating ever-changing surface conditions of a river basin.

• 한국항만학회지
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• 제10권1호
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• pp.15-23
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• 1996

In this paper, the numerical model to analyze the wave absorbing performance of upright perforated plates is developed under the linear potential theory. If the drag force is dominent to the inertia force in passing perforated plate, the characteristics of perforated plates are determined by a nondimensionlized real-value of G or a length scaled real-value of a. The parameters (G,a), which depend on the drag coefficient, porosity and local shape of plates, can be readily obtained by simple experiments. We investigated the reflection coefficients over a wide frequency range according to the arrays of perforated plates with different values of G and a. We found that the wave absorbing system using the arrays of upright perforated plates is sufficient to install in the ocean engineering basin.

• 한국지리정보학회지
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• 제15권3호
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• pp.103-118
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• 2012

분포형 모형은 유역내에서 공간 분포된 임의 지점의 유출해석 결과를 손쉽게 얻을 수 있다. 이때 다양한 특성을 가지는 소유역으로 구성된 유역의 경우, 소유역에 대해 신뢰성 있는 유출량을 얻기 위해서는 소유역별로 보정된 모형을 적용해야 한다. 본 연구에서는 관측 유량자료가 있는 소유역별로 모형을 보정할 수 있는 다지점 보정 기술을 개발하였다. 이를 위해서 다지점 보정 대상매개변수의 선정 및 적용 방법과 소유역 네트워크 정보를 설정하는 방법을 제시하였다. 또한 다지점 보정 모듈을 구현하기 위한 클래스를 설계하고 GUI를 개발하였으며, 소유역별로 설정된 매개 변수를 이용한 유출해석 절차를 정립하였다. 다지점 보정 모듈을 낙동강 수계 선산 유역($977km^2$)에 적용하였다. 적용결과 다지점 보정 모듈은 유역내 소유역에 대한 모형의 보정에 효과적으로 적용할 수 있었으며, 다지점 보정에 의해서 소유역의 유출해석 결과를 향상시킬 수 있었다.

• 지구물리와물리탐사
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• 제11권3호
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• pp.263-270
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• 2008

가스하이드레이트 개발사업단은 2007년 동해 울릉분지의 가스하이드레이트 탐사를 위하여 5개 정점에 대한 물리검층을 실시하였다. 물리검층은 시추와 동시에 지층의 물성 특성을 실시간으로 측정하는 LWD (Logging While Drilling) 및 MWD (Measurement While Drilling)가 동시에 수행되었다. LWD/MWD에서 취득된 검층자료는 전기비저항, 속도, 밀도, 공극률 및 자연감마와 시추와 동시에 얻어지는 온도, 압력 및 시추공경에 대한 자료 등이다. LWD/MWD에서 얻은 검층자료는 울릉분지에 가스하이드레이트의 존재가능성이 높은 몇 가지 증거를 보여주었다. LWD/MWD에서 취득된 검층자료를 기초로 하여 동해 울릉분지에 가스하이드레이트의 존재 가능성이 높은 3개 정점이 선정되었고, 이 정점에서 직접 시추작업을 수행한 견과 다량의 가스하이드레이트를 채취하는데 성공하였다. LWD를 통해 취득된 다양한 자료들은 향후 가스하이드레이트의 분포 및 매장량을 산정하기 위한 연구에 기초자료로 이용될 것이며, 그외 동해 울릉분지에서의 가스하이드레이트 함유 지층의 퇴적학적인 특성과 퇴적환경에 대한 연구에도 유용한 자료로 활용될 것이다.

• 한국농공학회지
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• 제27권2호
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• pp.23-37
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• 1985

This studies were carried out to get characteristics of frequency distribution, probable flood flows according to the return periods, and the correlation between return periods and those length of records affect the Risk of failure in the annual maximum series of the main river systems in Korea. Especially, Risk analysis according to the levels were emphasized in relation to the design frequency factors for the different watersheds. Twelve watersheds along Han, Geum, Nak Dong, Yeong San and Seom Jin river basin were selected as studying basins. The results were analyzed and summarized as follows. 1. Type 1 extremal distribution was newly confirmed as a good fitted distribution at selected watersheds along Geum and Yeong San river basin. Three parameter lognormal Seom Jin river basin. Consequently, characteristics of frequency distribution for the extreme value series could be changed in connection with the watershed location even the same river system judging from the results so far obtained by author. 2. Evaluation of parameters for Type 1 extremal and three parameter lognormal distribution based on the method of moment by using an electronic computer. 3. Formulas for the probable flood flows were derived for the three parameter lognormal and Type 1 extremal distribution. 4. Equations for the risk to failure could be simplified as $\frac{n}{N+n}$ and $\frac{n}{T}$ under the condition of non-parametric method and the longer return period than the life of project, respectively. 5. Formulas for the return periods in relation to frequency factors were derived by the least square method for the three parameter lognormal and Type 1 extremal distribution. 6. The more the length of records, the lesser the risk of failure, and it was appeared that the risk of failure was increasing in propotion to the length of return periods even same length of records. 7. Empirical formulas for design frequency factors were derived from under the condition of the return periods identify with the life of Hydraulic structure in relation to the risk level. 8. Design frequency factor was appeared to be increased in propotion to the return periods while it is in inverse proportion to the levels of the risk of failure. 9. Derivation of design flood including the risk of failure could be accomplished by using of emprical formulas for the design frequency factor for each watershed.

• 한국물환경학회지
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• 제26권3호
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• pp.532-539
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• 2010

The synthetic unit hydrograph is developed and verified using Nash model and characteristic velocities considering geomorphological dispersion in this present study. Application watersheds are selected 5 subwatersheds of Bocheong basin. The mean and variance of hillslope and stream path length are estimated in each watershed with GIS. Characteristic velocities are calculated using estimated path lengths and moment characteristics of rainfall-runoff data. Characteristic velocities of random devised 7 ungauged watersheds are estimated through regional analysis of chracteristic velocities in guaged watershed. And Nash model parameters and IUH are derived using characteristic velocities and path length in the gauged and ungauged watershed. The result to compare of IUH about gauged watershed and random devised ungauged watershed in application watershed presents coherently hydrologic response characteristics that peak discharge is reduced and peak time is extended. In conclusion, Developed synthetic unit hydrograph in this study expects that it is useful method to estimate runoff discharge for managing of water pollution in ungauged watershed.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.1849-1853
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• 2007

In this study, flow-sediment discharge characteristics and relationships are estimated for the Cheonggyecheon basin, newly restored in 2005. Flow and sediment discharge measurement is performed on Ogansugyo, Majanggyo 2 and Yongdugyo during the rainy seasons in 2005-2006. The parameters of Clark UH are estimated using measured data, and sediment rating curves are derived by using grading and concentration analysis. Concentration time and storage coefficient of Clark UH are estimated 0.5 hr and 0.63 hr for Majanggyo 2, and 0.4 hr and 0.45 hr for Yongdugyo, respectively. Grain size of sediments are composed of fine silt to fine sand (0.008-0.25mm) based on the sediment grain size classification (Lane, 1947). Flow-sediment relationships derived by using concentration analysis shows that sediment discharge has no obvious relationship with flow discharge.

• 산업기술연구
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• 제27권B호
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• pp.83-89
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• 2007

We studied runoff characteristics of combined sewer overflows in a city while it was raining. The event mean concentration (EMC) of biochemical oxygen demand (BOD), chemical oxygen demand ($COD_{Cr}$), suspended solids (SS), total nitrogen (TN), and total phosphorus (TP) in one of the combined sewer sites in Chuncheon was 63.5-211.6 mg/L, 114.9-523.8 mg/L, 70.3-436.4 mg/L, 6.4-33.0 mg/L, and 1.09-6.81 mg/L, respectively. In another combined sewer, the EMC of BOD, COD, SS, TN, and TP was 42.1-131.4 mg/L, 107.7-256.5 mg/L, 33.7-221.1 mg/L, 7.9-26.4 mg/L, and 1.16-3.91 mg/L, respectively. The ratio of the cumulative pollutant mass and the cumulative discharged volume determined using all parameters (BOD, $COD_{Cr}$, SS, TN, and TP) was over 1.0, which shows the first flush effect. Relationships between flow and loadings of BOD, $COD_{Cr}$, SS, TN, and TP were 0.90, 0.89, 0.88, 0.89, 0.92, respectively. Although the size of two areas was almost same, pollutant concentration and loading were different because of the amount of rainfall, rainfall intensity and basin area.

• 한국물환경학회지
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• 제37권3호
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• pp.204-216
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• 2021

It is important to understand the factors influencing the temporal and spatial variability of water quality in order to establish an effective customized management strategy for contaminated aquatic ecosystems. In this study, the spatial diversity of the 5-year (2015 - 2019) average total phosphorus (TP) concentration observed in 40 Total Maximum Daily Loads unit-basins in the Nakdong River watershed was analyzed using 50 predictive variables of watershed characteristics, climate characteristics, land use characteristics, and soil characteristics. Cross-correlation analysis, a two-stage exhaustive search approach, and Bayesian inference were applied to identify predictors that best matched the time-averaged TP. The predictors that were finally identified included watershed altitude, precipitation in fall, precipitation in winter, residential area, public facilities area, paddy field, soil available phosphate, soil magnesium, soil available silicic acid, and soil potassium. Among them, it was found that the most influential factors for the spatial difference of TP were watershed altitude in watershed characteristics, public facilities area in land use characteristics, and soil available silicic acid in soil characteristics. This means that artificial factors have a great influence on the spatial variability of TP. It is expected that the proposed statistical modeling approach can be applied to the identification of major factors affecting the spatial variability of the temporal average state of various water quality parameters.