• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.839-850
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• 2018

The flood damage in urban areas due to torrential rain is increasing with urbanization. For this reason, accurate and rapid flooding forecasting and expected inundation maps are needed. Predicting the extent of flooding for certain rainfalls is a very important issue in preparing flood in advance. Recently, government agencies are trying to provide expected inundation maps to the public. However, there is a lack of quantifying the extent of inundation caused by a particular rainfall scenario and the real-time prediction method for flood extent within a short time. Therefore the real-time prediction of flood extent is needed based on rainfall-runoff-inundation analysis. One/two dimensional model are continued to analyize drainage network, manhole overflow and inundation propagation by rainfall condition. By applying the various rainfall scenarios considering rainfall duration/distribution and return periods, the inundation volume and depth can be estimated and stored on a database. The Rainfall-Duration-Flooding Quantity (RDF) relationship curve based on the hydraulic analysis results and the Self-Organizing Map (SOM) that conducts unsupervised learning are applied to predict flooded area with particular rainfall condition. The validity of the proposed methodology was examined by comparing the results of the expected flood map with the 2-dimensional hydraulic model. Based on the result of the study, it is judged that this methodology will be useful to provide an unknown flood map according to medium-sized rainfall or frequency scenario. Furthermore, it will be used as a fundamental data for flood forecast by establishing the RDF curve which the relationship of rainfall-outflow-flood is considered and the database of expected inundation maps.

• Spatial Information Research
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• v.14 no.4 s.39
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• pp.363-377
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• 2006

Mean annual soil loss was calculated and critical soil erosion areas were identified for the Congaree River Basin in South Carolina, USA using the Revised Universal Soil Loss Equation (RUSLE) model. In the RUSLE model, the mean annual soil loss (A) can be calculated by multiplying rainfall-runoff erosivity (R), soil erodibility (K), slope length and steepness (LS), crop-management (C), and support practice (P) factors. The critical soil erosion areas can be identified as the areas with soil loss amounts (A) greater than the soil loss tolerance (T) factor More than 10% of the total area was identified as a critical soil erosion area. Among seven subwatersheds within the Congaree River Basin, the urban areas of the Congaree Creek and the Gills Creek subwatersheds as well as the agricultural area of the Cedar Creek subwatershed appeared to be exposed to the risk of severe soil loss. As a prototype model for examining future effect of human and/or nature-induced changes on soil erosion, the RUSLE model customized for the area was embedded into ESRI ArcGIS ArcMap 9.0 using Visual Basic for Applications. Using the embedded model, users can modify C, LS, and P-factor values for each subwatershed by changing conditions such as land cover, canopy type, ground cover type, slope, type of agriculture, and agricultural practice types. The result mean annual soil loss and critical soil erosion areas can be compared to the ones with existing conditions and used for further soil loss management for the area.

• Water for future
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• v.26 no.1
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• pp.115-124
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• 1993

This study is to determine the critical duration of design rainfall and to utilize it for the design of detention pond with pump station. To examine the effect of the duration and temporal distribution of the design rainfall, Huff's quartile method is used for the 9 cases of durations ranging from 20 to 240 minutes with 10 years return period, and the ILLUDAS model is used for runoff analysis. The storage ration which is the ratio of maximum storage amounts to total runoff volume, is introduced to determine the critical duration of design rainfall. The duration which maximizes the storage ratio is adopted as the critical duration. This study is applied to 18 urban drainage watersheds with pump station in Seoul, of which the range of watershed area is $0.24-12.70\textrm{km}^2.$ The result of simulation shows that the duration which maximizes storage ration is 30 and 60 minutes on the whole. It is shown also that the storage ration of 2nd- and 3rd-quartile pattern is larger than that of 1st- and 4th-quartile pattern of temporal distribution. A simplified empirical formula for Seoul area is suggested by using the regression analysis between the maximum storage ration and the peak ratio, and can be utilized for the preliminary design and planning of detention pond with pump station.

• Journal of Environmental Impact Assessment
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• v.24 no.2
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• pp.163-174
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• 2015

Urbanization caused various environmental problems like destruction of natural water cycle and increased urban flood. To solve these problems, LID(Low Impact Development) deserves attention. The main objective of LID is to restore the water circulation to the state before the development. In the previous studies about the LID, the runoff reduction effect is mainly discussed and the effects of each techniques of LID depending on rainfall types have not fully investigated. The objective of this research is to evaluate the effect of LID using the quantitative simulation of rainwater runoff as well as an amount of infiltration according to the rainfall and LID techniques. To evaluate the water circulation of LID on the development area, new land development areas of Hanam in South Korea is decided as the study site. In this research, hydrological model named STORM is used for the simulation of water balance associated with LID. Rainfall types are separated into two categories based on the rainfall intensity. And simulated LID techniques are green roof, permeable pavement and swale. Results of this research indicate that LID is effective on improvement of water balance in case of the low intensity rainfall event rather than the extreme event. The most effective LID technique is permeable pavement in case of the low intensity rainfall event and swale is effective in case of the high intensity rainfall event. The results of this study could be used as a reference when the spatial plan is made considering the water circulation.

• Journal of Korea Water Resources Association
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• v.45 no.1
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• pp.39-52
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• 2012

Surface-subsurface interactions are an intrinsic component of the hydrologic response within a watershed. In general, these interactions are considered to be one of the most difficult areas of the discipline, particularly for the modeler who intends simulate the dynamic relations between these two major domains of the hydrological cycle. In essence, one major complexity is the spatial and temporal variations in the dynamically interacting system behavior. The proper simulation of these variations requires the need for providing an appropriate coupling mechanism between the surface and subsurface components of the system. In this study, an approach for modelling surface-subsurface flow and transport in a fully intergrated way is presented. The model uses the 2-dimensional diffusion wave equation for sheet surface water flow, and the Boussinesq equation with the Darcy's law and Dupuit-Forchheimer's assumption for variably saturated subsurface water flow. The coupled system of equations governing surface and subsurface flows is discretized using the finite volume method with central differencing in space and the Crank-Nicolson method in time. The interactions between surface and subsurface flows are considered mass balance based on the continuity conditions of pressure head and exchange flux. The major module consists of four sub-module (SUBFA, SFA, IA and NS module) is developed.

• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.929-939
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• 2018

In North Korea, hydropower which occupies about 63% of power generation is a major electric power source, and North Korea has many advantages in the geographical for developing hydroelectric power. In this study, Information on the basin and dam capacity for 33 potential development site of hydroelectric dam was analyzed using DEM, and potential annual power generation was estimated by applying results of long-term runoff simulation with MWSWAT model for recent 30-year. The potential annual power generation at 33 dam was estimated to be about 28% of the current hydroelectric power in North Korea. In addition, a priority of dam development in each province was assessed by estimating the scale of an industry and prospecting the population change in the future. And a priority for dam development within the province was estimated based on the dam capacity and the potential annual power generation. The priority of each province was ranked in order of Pyeongannamdo, Hamgyungnamdo, Hamgyungbukdo, Hwanghaebukdo, Pyeonganbukdo, Jagangdo, Ryanggangdo, Hwanghaenamdo, and Gangwondo. The results of this study can be used as an initial review data for advancing to hydropower development project in North Korea.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.897-913
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• 2004

There has been continuous efforts to manage the water resources for the required water quality criterion at river channel in Korea. However, we could not obtain the partial improvement only for the point source pollutant such as, wastewater from urban and industrial site through the water quality management. Therefore, it is strongly needed that the Best Management Practice(BMP) throughout the river basin for water quality management including non-point source pollutant loads. This problem should be resolved by recognizing the non-point source pollutant loads from upstream river basin to the outlet depends on the land use and soil type characteristic of the river basin using the computer simulation by distributed parameter model based on the detailed investigation and the application of Geographic Information System(GIS). Used in this study, Annualized Agricultural Non-Point Source Pollution (AnnAGNPS) model is a tool suitable for long term evaluation of the effects of BMPs and can be used for un gauged watershed simulation of runoff and sediment yield. Now applications of model are in progress. So we just describe the limited result. However If well have done modeling and have investigated of propriety of model, well achieve our final goal of this study.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.759-763
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• 2010

본 연구는 격자기반의 지표면 유출 및 도시 유역 우수관거 유출해석모형으로서 유역을 관거 유입구를 기준으로 다수의 소유역들로 구분하고 각 소유역내 지표면 흐름을 비선형저류방정식으로 표현하여 유출량을 산정하는 방법 및 유역을 일정한 크기의 격자로 분할한 상태에서 각 격자의 유입 유출을 계산함으로써 주어진 시간 간격별로 유역 전체에 대한 물수지를 파악하는 격자 물수지식을 이용하는 방법을 결합하여 도시유역의 지표면 유출량을 산정하기 위한 격자기반의 분포형 지표면 유출해석 모형을 개발하는 것을 연구의 목적으로 하였다. 즉, 본 연구에서 개발한 유출모형은 지표면 유출의 메카니즘을 비선형저류방정식으로 표현한다는 점에서 SWMM의 방법을, 격자기반으로 유출량을 계산 추적한다는 것이다. 또한 도시지역의 침수형태 및 원인을 파악함과 동시에 기존의 도시유출 해석모형을 일부 수정 및 보완하여 집중호우발생시의 지표이동류 흐름, 폐합형 우수관거, 하류부의 배수영향 등을 고려한 우수관거 유출모델을 개발하였다. 본 모형을 이용하여 가상 및 실제 유역에 대한 유출모의를 수행함으로써 모형의 적용성을 평가하였다. 본 연구에서 제시하는 격자기반 도시유출해석모형은 대상유역을 일정한 크기의 격자로 구성하고 개개의 격자마다 유출해석을 위한 지형정보와 수문정보를 입력하여 격자별 유출량을 계산 추적함으로써 유역의 임의의 위치에서의 유출량, 유출심의 시간적 변화와 공간적인 분포를 모의할 수 있다. 가상 및 실제 유역에 대한 유출해석을 통하여 본 연구에서 개발한 모형은 이동강우나 국지적인 집중호우 등 시공간적으로 변하는 수문 특성을 반영할 수 있고, 폐합형 우수관망 해석 및 하류부 배수효과를 검토하여 도시유역의 홍수방재관리에 유용하게 활용될 수 있을 것으로 기대된다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.222-223
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• 2017

기후변화로 인한 태풍 및 집중호우의 발생빈도가 증가함에 따라 매년 많은 홍수피해가 발생하고 있다. 특히 제주도는 지리적 특성상 태풍의 길목에 위치하고 있어 집중호우, 돌발홍수 등과 같은 자연재해에 연중 노출되어 있으며, 이상기후로 인한 일강우량의 경신이 빈번하게 발생함에 따라 홍수피해 위험이 증가하고 있다. 홍수피해를 저감시키기 위해서는 정확한 홍수량 산정을 통한 하천기본계획 및 치수계획 수립이 매우 중요하다. 실무에서는 홍수량 산정 시 대부분 HEC-HMS 모형을 활용하고 있으나 본 연구에서는 기존 방법이 아닌 분포형 모형인 Vflo를 활용하여 제주도심하천의 홍수유출을 해석하였다. 도심하천인 외도천을 연구대상유역으로 선정하였으며 Arc-GIS를 이용하여 DEM, 토지피복도, 토양도 등 지형인자들을 $30m{\times}30m$ 격자크기로 나누어 매개변수로 구축하였다. 제주도는 강우관측소가 조밀하고 고르게 분포되어 있어 강우자료의 경우는 레이더영상 자료로부터 추출하여 G/R 기법을 적용하여 보정하였다. 2012년 7월 태풍 카눈은 RMSE 2.6954와 0.9115, 8월 집중호우는 RMSE 2.5703, $R^2$ 0.9202, 9월 태풍 산바는 RMSE 2.1569, $R^2$ 0.9842로 높은 상관관계를 보였다. 본 연구의 홍수량 산정 방법 정확도 비교를 위해 현장관측자료(FSIV)를 분석한 유출량과 비교 분석하였다. Vflo를 활용한 홍수량 산정 방법은 미계측 유역이 많은 제주도에서 효율적으로 활용될 수 있을 것으로 판단되며, 다양한 홍수량 산정 방법을 통하여 하천기본계획 및 유역종합치수계획 등 치수계획 수립 시 많은 활용이 될 것으로 기대한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.362-366
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• 2016

기후 변화에 따른 국지성 집중호우, 게릴라성 호우는 도심지역 홍수피해의 주요 원인으로, 이러한 극한 강우사상에 대해 도시지역의 침수피해를 선제적으로 대응하기 위해서는 강우-유출모의 현상을 과학적인 방법으로 분석할 필요가 있다. 이러한 이유로 주요 침수발생지역에 국한하여 강우-유출 해석이 수행되어왔지만, 도시전체에 대한 분석은 시간적, 인력적 제약으로 분석이 어려운 실정이다. 본 연구에서는 대표적 도시지역인 서울시의 전체 239개 배수분구를 83개 배수구역으로 구분, 서울시 최신 UIS자료를 이용하여 각 배수구역별 도시유출모형 구축을 위한 소유역 및 관망 입력자료 DB를 GIS shape파일 형식으로 구축하였으며, 미국 EPA의 SWMM을 적용하여 도시유출모형을 구축하였다. 시간적, 인력적 제약을 극복하기 위하여 구축할 관망 기준을 수립 및 가공하여 적용하였으며, 매뉴얼을 작성하여 매개변수의 적용기준 및 DB구축절차를 표준화하여 입력자료의 일관성 및 객관성을 도모하였다. 구축한 모형의 신뢰성 확보를 위해 서울시 기왕 주요 호우사례에 대한 유출모의 결과와 유량측정 성과의 비교를 통해 모형 검증을 수행한 결과, 관측수위/모의수위의 상관계수는 대부분의 지역에서 0.9 이상으로 나타나 모형 구축결과는 적정한 것으로 판단되었다. 구축된 모형은 실시간으로 변화하는 기상상황을 합리적으로 반영하기 위한 고해상도 기상자료를 활용한 도시침수 예측정보 생산 기술 개발의 기반 자료로 활용될 예정이며, 서울시 전역의 우수관로 월류에 의한 침수 취약지역 파악 및 침수원인 분석, 상습 침수지역에 대한 하수관로 교체 및 저류지 설치 등 치수계획에 대한 기초자료로도 활용 될 수 있을 것이다.