• Journal of Korea Water Resources Association
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• v.55 no.10
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• pp.823-833
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• 2022

This study aims to improve the runoff modeling accuracy of a basin using Hydrological Simulation Program-FORTRAN (HSPF) model by considering nonhomogeneous characteristics of a basin. By entering classified values according to the various types of land cover and soil to the parameters in HSPF-roughness coefficient (NSUR), infiltration (INFILT), and evapotranspiration (LZETP)- the heterogeneity of the Yongdam Dam basin was reflected in the model. The results were analyzed and compared with the one where the parameters were set as a single value throughout the basin. The flow rate and water quality simulation results showed improved results when classified parameters were used by land cover and soil type than when single values were used. The parameterization changed not only the flow rate, but also the composition ratio of each hydrologic components such as surface runoff, baseflow, and evapotranspiration, which shows the impact of the value set to a parameter on the entire hydrological process. This implies the importance of considering the heterogeneous characteristics of the land cover and soil of the basin when setting the parameters in a model.

• Journal of Korea Water Resources Association
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• v.53 no.1
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• pp.45-56
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• 2020

This study aims to quantify the uncertainty that can be induced by the objective function when calibrating SWAT parameters using SWAT-CUP. SWAT model was constructed to estimate runoff in Naesenong-cheon, which is the one of mid-watershed in Nakdong River basin, and then automatic calibration was performed using eight objective functions (R², bR², NS, MNS, KGE, PBIAS, RSR, and SSQR). The optimum parameter sets obtained from each objective function showed different ranges, and thus the corresponding hydrologic characteristics of simulated data were also derived differently. This is because each objective function is sensitive to specific hydrologic signatures and evaluates model performance in an unique way. In other words, one objective function might be sensitive to the residual of the extreme value, so that well produce the peak value, whereas ignores the average or low flow residuals. Therefore, the hydrological similarity between the simulated and measured values was evaluated in order to select the optimum objective function. The hydrologic signatures, which include not only the magnitude, but also the ratio of the inclining and declining time in hydrograph, were defined to consider the timing of the flow occurrence, the response of watershed, and the increasing and decreasing trend. The results of evaluation were quantified by scoring method, and hence the optimal objective functions for SWAT parameter calibration were determined as MNS (342.48) and SSQR (346.45) with the highest total scores.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1659-1663
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• 2008

홍수 범람에 의한 피해를 경감시키기 위해서는 하천관리에 필요한 제반 수리 수문 자료를 지속적으로 축적함으로써 하천관리의 과학화를 도모해야 하며 효율적인 홍수피해 경감을 위한 체계를 구축해야 한다. 이를 위한 기초 자료로써 범람 홍수의 거동특성을 파악하는 것은 무엇보다도 우선되어야 한다. 본 연구에서는 극한 홍수의 발생으로 제방의 붕괴위험이 증가되는 상황을 고려하여 과거범람 지역 조사 및 분석, 제방마루 높이와 여유고 평가, 무차원 소류력에 의한 취약지점 분석 및 제방의 월류위험도 분석을 통해 홍수재해에 대한 취약지점 선정 및 제내외지의 홍수특성 분석 방법을 제안하여 현실적인 하천방재계획 수립에 기여하고자 하였다.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.573-583
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• 2013

Construction of large-scale structures such as dams would be suggested actively to cope with change of flood characteristics caused by climate change. However, due to environmental, economic and political issues, dams are not ideally constructed. Thus flood damage reduction planning projects would get started including washland or detention pond for sharing the flood in basin. The washland made artificially by human being is an area of floodplain surrounded by bank to be intentionally inundated by overflowing through overflow structure adjacent to main channel during flood season. Flood reduction capacity at just downstream of each washland could be affected by type, length, and crest elevation of overflow structure in addition to shape of design hydrograph, storage volume of washland, etc.. In this study flood reduction effects of washland are estimated for overflow weir type and gate type to compare the results of flood reduction respectively subjected to given hydrograph in sample site, the Cheongmicheon stream. It has been shown that even if gate type at overflow structure could yield more flood reduction than overflow weir type, economic aspect such as initial cost, operation cost and maintenance cost should be considered to select the type of overflow structure because flood reduction rate by gate type could not be significant value from engineering point of view.

• Journal of Korea Water Resources Association
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• v.40 no.5
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• pp.419-430
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• 2007

Integrated modelling of surface water and groundwater has become important to satisfy the growing demands for sustainable water resources and improved water quality. In this study, the integrated model of the semi-distributed watershed model, SWA T and the fully-distributed groundwater flow model, MODFLOW is applied to Musirn river basin for the purpose of investigating its applicability to reproduce watershed-scale hydrological processes. This objective is accomplished by first demonstrating good agreement between the simulated discharge hydrographs with the measured hydrographs for the period of 2001 -2004 while simultaneously calibrating the calculated groundwater level distribution to observation wells. Next, the integrated model is used to evaluate the effect of different temporal precipitation averages on hydrodynamic processes of streamflow, percolation, recharge and groundwater discharge. Moreover, comprehensive simulations are performed to present the relationships between monthly precipitation and each hydrological component, and to analyze the temporal-spatial variability of recharge. The results show that the components are highly interrelated, and that the heterogeneity of watershed characteristics such as subbasin slope, land use, soil type causes a significant spatial variation of recharge. Overall it is concluded that the model is capable of reproducing the temporally and spatially varied surface and subsurface hydrological processes at the watershed scale.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.117-117
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• 2012

본 연구에서는 도시화가 진행중인 경안천($561.1km^2$)유역과 안성천($909.1km^2$) 유역을 대상으로 토지이용 변화를 분석하고 그에 따른 유출특성을 파악하는데 있다. 경안천과 안성천 유역의 과거(1975, 1980, 1985, 1990, 1995, 2000)의 토지이용 분석결과 도시지역 면적이 각각 6.9%와 8.3%씩 증가하였다. 본 연구에서는 미래토지이용 예측을 위하여 CLUE-S (Conversion of Land Use Change and its Effects)모델을 이용하였다. 과거 토지이용 변화 특성을 분석하여 토지피복의 변화와 전이 특성값을 결정하였고, 이를 바탕으로 토지면적 시나리오, 변화 제한지역, 회귀식 결과와 토지이용 변화 특성 값을 CLUE-S 모델에 입력하여 미래의 토지이용변화를 모의하였다. 예측된 토지이용 정보를 가지고 2040s (2020-2059)와 2080s (2060-2099)의 기간으로 나누어 수문모의가 가능한 SWAT (Soil and Water Assessment Tool) 모형에 적용 및 그에 따른 유출특성을 파악하였다. SWAT 모형의 적용성 평가를 위하여 안성천과 경안천 유역을 대상으로 1998~2005의 기간 동안 일별 유출, 자료에 대한 보정 및 검증을 실시하였다. 미래의 토지이용 변화에 따른 유역의 유출특성의 영향은 도시의 비율이 큰 유역에서 더 많이 나타날 것으로 기대된다.

• Ecology and Resilient Infrastructure
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• v.6 no.2
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• pp.89-100
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• 2019

We've reviewed existing studies on the interactions among vegetation, hydrology, and geomorphology in the stream corridors, adding one more factor of vegetation in the traditional area of hydro-geomorphology. Understanding of the interactions among those three factors is important not only academically but also practically since it is related intimately to the restoration of river corridor as well as management itself. Studies of this area started from field investigations in the latter part of the 20th century and focused on the flume experiments and then computer modelling in the 1990s and 2000s. Now, it has turned again to the field investigations of specific phenomena of the vegetative-hydrologic-geomorphologic interactions in detailed micro scales. Relevant studies in Korea, however, seem to be uncommon and far behind the international status quo in spite that practically important issues related directly to this topic have been emerged. In this study, we propose, based on the extensive literature review and authors' own knowledge and experiences, a conceptual diagram expressing the interactions among vegetation, flow (water), sediment, and geomorphology. Existing relevant studies in Korea since the 1990s are classified according to the categorization in the proposed diagrams and then briefly reviewed. Finally, considering the practical issues of riparian vegetation that have emerged recently in Korea, we propose areas of investigation needed in near future such as, among others, long-term and systematic field investigations and monitoring at multiple river corridors having different attributes on vegetative-hydrologic-geomorphologic interactions, including vegetative dynamics for succession.

• Journal of Korea Water Resources Association
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• v.56 no.2
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• pp.151-163
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• 2023

This study explored the 2022 drought over the Nakdong River watershed. Here, we developed a bivariate regional frequency analysis method to evaluate the risk of hydrological drought. Currently, natural streamflow data are generally limited to accurately estimating the drought frequency. Under this circumstance, the existing at site frequency analysis can be problematic in estimating the drought risk. On the other hand, a regional frequency analysis could provide a more reliable estimation of the joint return periods of drought variables by pooling available streamflow data over the entire watershed. More specifically, the Copula-based regional frequency analysis model was proposed to effectively take into account the tail dependencies between drought variables. The results confirmed that the regional frequency analysis model showed better performance in model fit by comparing the goodness-of-fit measures with the at-site frequency analysis model. We find that the estimated joint return period of the 2022 drought in the Nakdong River basin is about eight years. In the case of the Nam river Dam, the joint return period was approximately 20 years, which can be regarded as a relatively severe drought over the last three decades.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.95-95
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• 2018

최근 하천관리 정책은 단편적인 홍수방어뿐만 아니라 맑은 물을 안전하게 확보하고 건강한 생태계가 유지되는 하천으로 관리하는 방향에 주안점을 두고 있다. 그러나 치수 목적의 하천관리 기술에 비하여 하천환경관리를 위한 기술은 요소기술 개발 및 적용으로 산재되어 있어, 체계가 정립되지 못하고 실무 적용에서도 활용에 한계가 있는 실정이다. 따라서 본 연구에서는 치수, 이수, 하천환경 목적의 다차원 하천관리를 위하여 하천복원의 기술적 체계를 기술수준의 정도를 기준으로 단계별로 정립하였다. 첫 단계는 수문특성, 수리특성, 하상변동/유사특성, 생물/화학특성의 분석이다. 이 단계에서는 각 특성의 현황과 하천복원 방법에 따른 물리특성 변화를 분석하는 것이다. 다음 단계는 하천복원에 따른 정량적인 기대효과 분석이다. 수위저감 및 안정하도 확보, 수질개선, 생물서식처 효과분석 등이 수행된다. 마지막 단계는 하천복원 등의 관리계획에 의한 기대효과 전망이다. 사회경제적 가치, 생물종 다양성 확대가치 등이 분석항목에 포함된다. 각 단계에서는 계량 가능한 지표를 설정하여 계획의 성과를 비교한다. 제안된 다차원 하천복원 기술적 프레임웍을 통해 하천사업에 따른 물리, 생물, 사회, 경제 등 다양한 분야의 구조를 통합한 방법론을 제시함으로써 하도개선 위주의 획일적인 하천복원사업에 변화를 주고, 더 나아가 하천공간 복원 등 적극적인 하천복원사업이 활성화되길 기대한다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.4
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• pp.381-392
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• 2011

Pollutant loads calculated with unit factor method can not identity seasonal variations of pollutant inputs. Estimation of pollutant loads considering rainfall runoff can overcome these limits. SCS curve number method was applied to estimate runoff of each event of Koeup watershed of Koheung estuary lake. SCS curve numbers were calculated based upon land use, soil types of the catchment using GIS. Point and nonpoint source pollutant loads were summed up for total loads estimation. Those from nonpoint source were estimated by multiplying the calculated runoff and expected mean concentrations (EMC) presented by the Minister of Environment of Korea. DEM can present three dimensional views of a terrain, identity stream networks and flow accumulation. Furthermore, it can examine accumulated pollutant loads of specific point of a catchment. Therefore, cell based pollutant load estimation was attempted using DEM. ArcView was utilized to collect, store and manipulate spatial and attribute data of pollutant sources and features of the catchment. Cell-based DEM which was established by the GRID module of ARC/INFO was employed to estimate flows and pollutant loads.