• Land and Housing Review
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• v.8 no.4
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• pp.249-256
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• 2017

Urbanization can be remarkable affected flood, pollutant loading, ecological system, and green infrastructure by distortion of hydrologic cycle. In order to mitigate these problems in urban, Low Impact Development(LID) technique has been introduced and applied in the world. SWMM model was calibrated with sets of field monitoring data and applied for calculation of runoff and pollutant loading in Asan-tangjung LID city under 2016 rainfall. Runoff reduction of watershed and catchment basins were showed efficiency 12.2% and 62.0%, respectively. Reduction of COD and TP loading also high efficiency in catchment basins were evaluated 74.9 and 71.4%. The results of this study can be used effectively in decision making processes of urban development project by comparing watershed runoff and pollutant reduction by designs of sort of LID technique, LID volume and location.

• Journal of Korea Water Resources Association
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• v.37 no.11
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• pp.969-978
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• 2004

According to the report of hydrologic modeling study, from a quantitative point of view, a lumped model is more efficient than a distributed model. A distributed model has to simplify geospatial characteristics for the shake of restricted application on computer calculation and field observation. In this reason, a distributed model can not help having some errors of water quantity modelling. However, considering a distribution of rainfall-runoff reflected spatial characteristics, a distributed model is more efficient to simulate a flow of surface water, The purpose of this study is modeling of spatial rainfall-runoff of surface water using grid based distributed model, which is consisted of storage function model and essential basin-channel parameters( slope, flow direction & accumulation), and that procedure is able to be executed at a personal computer. The prototype of this model is developed in Heongseong Multipunose Dam basin and adapted in Hapchon Multipurpose Dam basin, which is larger than the former about five times. The efficiency coefficients in result of two dam basin simulations are more than about 0.9, but ones at the upstream water level gauge station meet with bad result owing to overestimated rating curves in high water level. As a result of this study, it is easily implemented that spatially distributed rainfall-runoff model using GIS, and geophysical characteristics of the catchment, hereafter it is anticipated that this model is easily able to apply rainfall data by real time.

• Journal of Korea Water Resources Association
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• v.49 no.1
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• pp.19-28
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• 2016

The objective of this study is the generation of the gridded flash flood index using the gridded hydrologic components of TOPLATS land surface model and statistic flash flood index model. The accuracy of this method is also examined in this study. The study area is the national capital region of Korea, and 38 flash flood damages had occurred from 2009 to 2012. The spatio-temporal resolutions of land surface model are 1 h and 1 km, respectively. The gridded meteorological data are generated using the inverse distance weight method with automatic weather stations (AWSs) of Korea Meteorological Administration (KMA). The hydrological components (e.g., surface runoff, soil water contents, and water table depth) of cells corresponding to the positions of 38 flood damages reasonably respond to the cell based hourly rainfalls. Under the total rainfall condition, the gridded flash flood index shows 71% to 87% from 4 h to 6 h in the lead time based on the rescue request time and 42% to 52% of accuracy at 0 h which means that the time period of the lead time is in a limited rescue request time. From these results, it is known that the gridded flash flood index using the cell based hydrological components from land surface model and the statistic flash flood index model have a capability to predict flash flood in the mountainous area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.1-12
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• 1983

The wave and hydrologic climate at a beach location are everchanging and coastal engineers have always been interested in the deformation of the natural beach caused by wave action over short or long interval of time. The drift of sand on a beach particulary manifests itself when blocked construction of seawalls, jetties, breakerwaters and groins etc.${\cdots}$ For this reason, the understanding and evaluation of littoral drift has been especially important to the coastal engineers. The resulting of the sand drift movement, such as the type of beach profile, width of beach, storage volume of the littoral sand over the profile are rapid everchange. We have studied the geological changes due to the littoral drift on a beach with field investigation and model tests in laboratory. But, it is impossible to make quantative correct analysis because of the factors are everchange and complicate. And then, most of study are incline to qualitative analysis. In this paper, authors studied mainly on the transition of beach profile and sediment storage on the profile using statistical field data as qualitative analytical method. The used theoretical beach transition model by Sonu and Beek have developed to obtain the change of HAEUNDAE beach backed with seawall. Results of this study indicate that the transition model are useful in the analysis of beach profile changement and the littoral drift movement on the beach. Qualitative analysises for HAEUNDAE beach are as follows. 1) Transition sequence of profile has 4 major transition for one cycle. 2) Storage sediment model of beach profile by Sonu and Beek well coincided with HAEUNDAE beach. 3) Seasonal cycle has ill-balanced process for the 5-yr. investigation.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.217-224
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• 2005

This study was aimed to analyze the long-term fluctuation of water quality and phytoplankton dynamics of Paldang reservoir in Korea and to assess the relationship between algal bloom patterns and hydrological, limnological data. Diatoms in Paldang reservoir occurred continuously through the year. Blue- green algae occurred during the summer season (from June to Sept.), and the highest count was observed in July. Occurrence pattern of green algae was similar to that of blue-green algae. The rest of algae contained a lot of Cryptomonas spp. whose concentration was high from May to Aug. Dominant algal genera (>>7,000 cells $mL^{-1}$) in Paldang reservoir were Aulacoseira, Cyclotella, Microcystis, and Cryptomonas spp. Microcystis and Anabaena occurred during the summer season. Many different green algal genera were found in Paldang reservoir but their abundances were very low. There were some significant correlations (r>0.3, p<0.05) between algal taxa and water quality; diatoms and water temperature, TP:blue-green algae and water temperature, pH, DO saturation, COD, TP; green algae and water temperature, pH, DO saturation, COD, SS, TP. Furthermore, algal genera and water quality was significantly correlated (r>0.3, p<0.05) ; Aulacoseira and TN, TP; Anabaena and water temperature, DO saturation, COD, TP : Microcystisand water temperature, pH, DO saturation, TP; Coelastrum and COD, SS; Scenedesmus and water temperature, COD, TN, TP; Cryptomonas and DO saturation, TN. In Paldang reservoir, the water temperature had relatively big effect on blue-green algal bloom that was also dependant upon its hydrologic condition.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.329-341
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• 2011

This study was conducted with the national river, Munsancheon, which is located in Paju-si, Gyeonggi-do. The sediment discharge of Munsancheon was directly measured to analyze the sediment characteristics, and the results were used in the numerical model to predict the long-term river bed variation. The flow-total sediment discharge relation was derived using the measured total sediment discharge, and the results were compared with the total sediment discharge that was calculated using the existing prediction formula to derive a proper sediment discharge prediction method. In the actual measurements, the total annual sediment discharge was 5,478 ton/year, and the specific sediment discharge was 29.23 ton/$km^2$/year. The Ackers & White formula resulted in the values very close to the actual measurements. With the actual sediment discharge, geographical and hydrologic data as the input variables, HEC-6 and GSTARS models were comparatively analyzed. The test results showed that the HEC-6 model is suitable for the reliable prediction of the long-term river bed variation. Accordingly, the model was used for the long-term river bed variation prediction in this study. In the case of Munsancheon, deposition was continued in the downstream area and erosion occurred in the upstream area on the whole. It was expected that the stream would be stabilized in the river bed condition of 20 years later. The river bed variation was within 1 m, which was at the significance level. In the downstream area that is influenced by tide, however, the accumulation was continuously increasing within the section 2,000-7,000 m from the outlet. It seems that this should be considered in establishing the river management plans.

• Journal of Korea Water Resources Association
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• v.43 no.11
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• pp.995-1009
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• 2010

Accelerated soil erosion due to extreme climate change, such as increased rainfall intensity, and human-induced environmental changes, is a widely recognized problem. Existing soil erosion models are generally based on the gross erosion concept to compute annual upland soil loss in tons per acre per year. However, such models are not suitable for event-based simulations of erosion and deposition in time and space. Recent advances in computer geographic information system (GIS) technologies have allowed hydrologists to develop physically based models, and the trend in erosion prediction is towards process-based models, instead of conceptually lumped models. This study aims to propose an effective and robust distributed rainfall-sediment yield-runoff model consisting of basic element modules: a rainfall-runoff module based on the kinematic wave method for subsurface and surface flow, and a runoff-sediment yield-runoff model based on the unit stream power method. The model was tested on the Cheoncheon catchment, upstream of the Yongdam dam using hydrological data for three extreme flood events due to typhoons. The model provided acceptable simulation results with respect to both discharge and sediment discharge even though the simulated sedigraphs were underestimated, compared to observations. The spatial distribution of erosion and deposition demonstrated that eroded sediment loads were deposited in the cells along the channel network, which have a short overland flow length and a gentle local slope while the erosion rate increased as rainfall became larger. Additionally, spatially heterogeneous rainfall intensity, dependant on Thiessen polygons, led to spatially-distinct erosion and deposition patterns.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.267-276
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• 2019

The Gonggeomji Reservoir is a historical irrigation facility built in the 8th century and designated as a wetland protected area by Ministry of Environment, Korea. In order to collect the baseline data necessary for developing a sustainable conservation strategy, we investigated the classification of actual vegetation, the vegetation distribution and the floristic structure of the vegetation in the Gonggeomji Wetland Protection Area. In the whole protection area, a total of 26 plant communities were classified including the wetland, riparian, grassland, forest, farmland, and orchard vegetation. According to the results of detrended correspondence analysis, the structure of wetland vegetation was mainly affected by water depth and human disturbance. In reservoir wetlands, floating vegetation such as Utricularia vulgaris var. japonica, Trapa japonica, and emergent vegetation such as Nelumbo nucifera, Typha spp. completely covered the water surface. Since 2014, the reservoir wetland has been terrestrialized with the expansion of emergent and hygrophytic plants. For the sustainable conservation and restoration of wetland protected areas, it is necessary to naturalize the topography and wetland vegetation, recovery the hydrologic system, and restore ecosystem connectivity from wetlands to forests.

• Journal of Korea Water Resources Association
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• v.50 no.12
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• pp.827-836
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• 2017

The most important parameters of the Muskingum method, widely used in hydrologic river routing, are the storage coefficient and the weighting factor. The Muskingum method does not consider the lateral inflow from the upstream to the downstream, but the lateral inflow actually occurs due to the rainfall on the watershed. As a result, it is very difficult to estimate the storage coefficient and the weighting factor by using the actual data of upstream and downstream. In this study, the flow without the lateral inflow was calculated from the river flow through the hydraulic flood routing by using the HEC-RAS one-dimensional unsteady flow model, and the method of the storage coefficient and the weighting factor calculation is presented. Considering that the storage coefficient relates to the travel time, the empirical travel time formulas used in the establishment of the domestic river basin plan were applied as the storage coefficient, and the simulation results were compared and analyzed. Finally, we have developed a formula for calculating the travel time considering the flow rate, and proposed a method to perform flood routing by updating the travel time according to the inflow change. The rise and fall process of the flow rate, the peak flow rate, and the peak time are well simulated when the travel time in consideration of the flow rate is applied as the storage coefficient.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.75-87
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• 2007

Groundwater recharge rates were estimated and compared in a headwater catchment at the Gwangneung Supersite using three different methods: water-table fluctuation (WTF), mass balance, and hydrograph separation techniques. Data were obtained during the rainy season from June to September 2005. Two different WTF methods estimated the groundwater recharge rate as 25.9% and 23.6%. The mass balance calculation of chloride ions indicated recharge rates of 13.4% on average. Baseflow separation using chloride ion as a tracer from six storm hydrographs produced a 14.0% net baseflow rate on average. Because of the implicit assumption of a long-term steady state without storage change, recharge rates calculated by mass balance and hydrograph separation were smaller than those done with WTF methods, which include the amount of increased storage due to the water-level rise. Subsequently, the WTF method is superior to others in the estimation of groundwater recharge rate to comprehend the dynamic characteristics of the hydrologic cycle.