• Journal of Korea Water Resources Association
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• v.41 no.1
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• pp.17-25
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• 2008

Whether rating curves are used in practice or new ones are derived, the characteristics of regression analysis are often neglected. For example, a discharge rating curve, which is established from a regression of observed water levels (H) on observed flowrates(Q), is sometimes used for estimating a design water level corresponding to a simulated design flood runoff. However, if independent and dependent variables are changed with each other, the regression equation is changed in existing regression analysis, which is derived from vertical errors between observed data and regression line. Thus, regression equations should not be applied inversely. To avoid this problem, A new two-way variable least-squares regression analysis is proposed. The new method was applied to the rating curves of five water level stations on main stream of Nakdong River. The three kinds of regression models, which are respectively regression of Q versus H (model 1), H versus Q (model 2) and two-way (model 3), showed that the new method can reduce inadvertent mistakes when applied in practice.

• Journal of Korea Water Resources Association
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• v.43 no.12
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• pp.1051-1061
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• 2010

This study hydrologically re-analysed the Muskingum channel routing method to represent it as a linear combination of the linear channel model considering only the translation and the linear reservoir model considering only the storage effect. The resulting model becomes a kind of instantaneous unit hydrograph, whose parameters are identical to those of the Muskingum model. That is, the outflow occurs after the routing interval ${\Delta}t$ or concentration time $T_c$, and among the total amount of inflow, the x portion is translated by the linear channel model and the remaining (1-x) portion is routed by the linear reservoir model with the storage coefficient ��$K_c$. The application result of both the Muskingum channel routing method and its corresponding instantaneous unit hydrograph to an imaginary channel showed that these two models are basically identical. This result was also assured by the application to the channel flood routing to the Kumnam and Gongju Station for the discharge from the Daechung Dam.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.3
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• pp.283-290
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• 2016

Recent, the construction of the multi-purpose double-deck tunnel is required to solve the flood protection and congested area at urban city. The multi-purpose double-deck tunnel is desperately needed for the introduction of efficient utilization of underground space in addition to the main feature of road capabilities. A basic review was performed for site selection to consider the control capability and features of road tunnel at the same time, and the processable flow in accordance with tunnels cross section of double deck tunnel. Site Selection Criteria for multi-purpose use of the double-deck tunnel has been proposed through the site selection criteria by use of the tunnels review. Also the estimation processable flow was performed to review the versatility of double-deck tunnel due to design of tunnel cross-section. Site Selection of double-deck tunnel from this study can be seen the need for a complex consideration through a variety of analyzes.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.5
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• pp.557-564
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• 2009

A combined sewer system can quickly drain both storm water and sewage, improve the living environment and resolve flood measures. A combined sewer system is much superior to separate sewer system in reduction of the non-point source pollutant load. However, during rainfall. it is impossible in time, space and economic terms to cope with the entire volume of storm water. A sewage system that exceeds the capacity of the sewer facilities drain into the river mixed with storm-water. In addition, high concentration of CSOs by first-flush increase pollution load and reduce treatment efficiency in sewage treatment plant. The aim of this study was to develope a processing unit for the removal of high CSOs concentrations in relation to water quality during rainfall events in a combined sewer. The most suitable operational design for processing facilities under various conditions was also determined. With a designed discharge of 19.89 m/min, the removal efficiency was good, without excessive overflow, but it was less effective in relation to underflow, and decreased with decreasing particle size and specific gravity. It was necessary to lessen radius of vortex separator for increasing inlet velocity in optimum range for efficient performance, and removal efficiency was considered to high because of rotation increases through enlargement of comparing height of vortex separator in diameter. By distribution of influent particle size, the actual turbulent flow and experimental results was a little different from the theoretical removal efficiency due to turbulent effect in device.

• Journal of Korea Water Resources Association
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• v.47 no.10
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• pp.959-972
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• 2014

In this study, a space-time rainfall grid field generation model based on multifractal theory was verified using nine flood events in the upstream watershed of Chungju dam in South Korea. For this purpose, KMA radar rainfall data sets were analyzed for the space-time multifractal characteristics. Simulated rainfall fields that represent the multifractal characteristics of observed rainfall field were reproduced using the space-time rainfall grid field generation model with log-Poisson distribution and three-dimension wavelet function. Simulated rainfall fields were applied to the S-RAT model as input data and compared with both observed rainfall fields and low-resolution rainfall field runoff. Error analyses using RMSE, RRMSE, MAE, SS, NPE and PTE indicated that the peak discharge increases about 20.03% and the time to peak decreases about 0.81%.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.415-426
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• 2001

After Disaster Impact Assessment(DIA) Program was particed, the wide variety of hydrological data are estimated by introducing the concept of critical storm duration to calculate the stormwater impoundments as the alternative of increasing runoff due to many developments. Critical storm duration is varied by a lot of hydraulic structures, drainage characteristics, temporal distribution of design rainfall, return period, and runoff models. In this study the methods of estimating the proper volume to design the stormwater impoundments are proposed to determine the required volume by comparing and analyzing the maximum stormwater impoundments in accordance with the impoundment volume and rainfall duration by using the concept of storage ratio presented in the existing studies. The methods of determining the critical storm duration of design rainfall which cause the maximum load from the runoff hydrograph will be studied as analyzing rainfall-runoff using the various runoff models and observed data.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.25-25
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• 2011

우리나라는 국토의 60% 이상이 산지로 이루어져 있다. 최근 산지하천 유역에서 발생한 홍수와 토석류 등에 의해 많은 인적 물적 피해가 발생하고 있다. 현재 산지하천 유역은 유량자료에 비해 강우관측 자료는 비교적 많이 축적되어있으며, 최근에는 레이더를 이용한 강우관측도 지속적으로 이루어져 강우특성을 분석하는 것은 용이하다. 이에 비해서 산지하천 유역의 하천 유량에 대한 자료는 부족하거나 자료가 있더라도 결측치가 많고 보유연한이 분석에 필요한 만큼 충분하지 못하다. 또한 산지하천 유역의 유출특성을 분석하기 위해서는 강우관측 자료와 수위자료로부터 환산된 유량자료가 필수적인 인자이나 산지하천 유역의 수위관측소는 설치 및 유지관리 등의 어려움으로 인하여 유량자료가 상대적으로 부족한 실정이다. 이와 같은 제약을 해소하기 위해서는 많은 비용과 시간이 소요되므로 단 시간 내에 해결하는 것은 쉬운 일이 아니다. 따라서 유역의 물리적 특성을 이용하여 임의의 지점의 설계홍수량을 손쉽고, 정확하게 산정할 수 있다면 산지유역의 홍수와 토석류에 의해 발생하는 홍수 피해에 대한 대책을 마련하는데 큰 도움이 될 것이다. 일반적인 통계적 회귀분석은 여러 분야에서 널리 적용되고 있으나, 산지하천 유역의 강우-유출해석의 경우 관측자료의 수가 적고 발생하는 사상이 애매한 경우가 많아 일반적인 통계학적 선형 회귀분석을 적용하는 데 어려움이 많다. 이와 같은 어려움을 해결하기 위해 본 연구에서는 fuzzy regression 기법을 사용하였다. Fuzzy regression 기법의 하나인 possibilistic 모형을 사용하여 주어진 관측값과 산정값의 오차를 최소화함으로써 모형의 fuzziness를 최소화하였다. fuzzy regression 기법을 사용하면 변수들 간의 애매한 관계를 쉽게 해석하고 관측값과 산정값의 오차를 최소화하여 연구목적에 적합한 결과를 도출할 수 있다. 산지유역에서 발생하는 홍수는 많은 인명 및 재산피해뿐 아니라 사회 및 경제적 측면, 환경 및 생태계 그리고 인간의 정신적인 측면까지도 깊이 영향을 미친다. 따라서 본 연구에서 제안한 fuzzy regression 기법을 사용한 홍수량 산정기법을 통해 임의 지점의 빈도별 설계홍수량을 보다 신속하고 정확하게 산정하여 수공구조물의 설계에 적용하면 집중호우에 의해 발생하는 피해를 최소할 할 수 있을 것으로 기대된다.

• Ocean and Polar Research
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• v.28 no.3
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• pp.339-352
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• 2006

Seasonal and tidal variations of density stratification in the Saemangeum waters are investigated based on synoptic CTD observations between July 2003 and September 2005. CTD data used in this study are those obtained after closing the dike No. 4 and before closing the two final gaps, the Sinsi and the Garyeok, on the Saemangeum tidal harrier. A total of 19 field campaigns comprehend a wide temporal spectrum, that is, few seasons, spring and neap tides, and high and low waters. In addition, ADCPs were anchored and CTDs were cast at three stations for 25 h in July 2005. Water columns are vertically homogeneous in autumn and winter. The vertical homogeneity persists in spring but with an occasional weak stratification in i:he northern part of the Gogunsan Islands. Increased reshwater runoff tends to stabilize the water columns and strong density stratification is established in summer. The mean potential energy anomaly (PEA) in summer used as a stratification parameter is the largest $(27.7\;J\;m^{-3})$ in the northern part of the Gogunsan Islands where the Geum River discharge dominates, the smallest $(16.9\;J\;m^{-3})$ is in the inner area of the barrier, in between the two $(21.6\;J\;m^{-3})$ in the southern part of the Gogunsan Islands. Whereas the stratification is generally strengthened in summer, strong winds or large tidal currents over the shallow depths frequently destratify the water column near the mouth of river runoff inside the tidal barrier. Periodic stratification, the development of stratification on the ebb and its breakdown on the flood, occurs in the mid-area inside the barrier induced by the tidal straining, which can also be found in the results of 25 h observation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.3
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• pp.115-125
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• 1992

The variation of flow pattern caused by the topographical change of Kwangyang bay, is analyzed using the numerical tidal model for the depth-integrated two- dimensional long wave equation. The results of study are as follows. Due to pier construction, the area of water surface is deceased and the water inflow into the Kwangyang bay is reduced. For this result, at the outer bay of Myo island, the tidal range is slightly increased. And at the inner bay, water level is dropped generally, and especially at the time of low water tide, the phenomena of water level drop obviously appears. According to the variation pattern, flow velocities is lower than those of non-construction condition over the Kwangyang bay. But at the channel(from Kwangyang east stream) flowing into the east Kwangyang bay, for the contraction of channel profile, flow velocity is increased. The study based on the 100 year frequency design flood discharge from Sueocheon(river) and Dongcheon(river) which are flowing into the bay and Seomjin River flowing along the boundary of the bay is also performed. During the spring tide condition, the results showed the rise of water level about 1.2 m at Seomjin River Estuary and 0.3 m at inner bay is occurred.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.805-812
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• 2014

This study investigates the impact of morphological change on the physical habitat simulation. For this, CCHE2D model is used for the hydraulic analysis including the morphological change, and the physical habitat suitability is assessed with habitat suitability curves. The model is applied to a 2.5km long reach downstream of the Goesan Dam, from Sujeon Bridge to Daesu Weir. Flow data of discharge and stage in July, 2006 are used in the computation. The numerical model is verified by means of comparison with the measured water surface elevation data, and the variation of the river bed is not verified in this study. Adult Zacco platypus is chosen for the dominant species. Physical habitat simulations result in composite habitat suitability and weighted usable area for drought, low, normal, and averaged-wet flows. The simulation results indicate that the composite suitability index increased at reaches right downstream of the Sujeon Bridge and around the bend. This also increased weighted usable area by 5.4-11.3%.