• Journal of the Korean Association of Geographic Information Studies
• /
• v.16 no.3
• /
• pp.193-210
• /
• 2013

This study aims to assess the slope stability variation of Jeollabuk-do drainage areas by RCM model outputs based on A1B climate change scenario and infinite slope stability model based on the specific catchment area concept. For this objective, we downscaled RCM data in time and space: from watershed scale to rain gauge scale in space and from monthly data to daily data in time and also developed the GIS-based infinite slope stability model based on the concept of specific catchment area to calculate spatially-distributed wetness index. For model parameterization, topographic, geologic, forestry digital map were used and model parameters were set up in format of grid cells($90m{\times}90m$). Finally, we applied the future daily rainfall data to the infinite slope stability model and then assess slope stability variation under the climate change scenario. This research consists of two papers: the first paper focuses on the methodologies of climate change scenario preparation and infinite slope stability model development.

• Journal of Environmental Impact Assessment
• /
• v.14 no.5
• /
• pp.305-315
• /
• 2005

The scheme to classify pollution sources in Korean TMDL planning has been pointed out too much complex to implement practically because of requiring a wide range of items to be collected from a field. Within a deficient situation to collect field data, the mathematical scheme that focuses only on counting an uniform area ratio of the different land uses to estimate of pollutant loads from individual sub-catchments has been used without taking into account of the spatial characteristics of major land uses as well as the locations of pollution sources in each sub-catchment. It would cause to significant level of errors to estimate the pollution loads. Therefore, this study proposes a renovated scheme that can be adopted more easily to classify pollution sources in the watershed and reduce the estimation errors in the spatial distribution of pollution sources by introducing a spatial analysis based on digital land cover maps. In order to estimate a unit area to calculate the uniform pollution load, the pollution response unit area that is locating spatially at the same place and having same land use is identified through the application of GIS overlay technique. Unlikely existing conventional method to calculate the pollution load based on equal distribution of pollutants for each administrative boundary, it is assumed that the pollution load from household and livestock sources are generated and washed off from only residential areas. While, pollution from business population comes from commercial area and industrial load from wastewater discharge facilities are from industrial areas. From comparison of the calculated results from the existing the method and the proposed one, it is found that although the estimation of pollution load from sub-catchment in the case of the existing conventional method application results in negligible difference in total pollution amounts from the whole area of Wangsook watershed as a study area, significant difference of pollution load among sub-catchment in which pollution response unit areas are diverse, however, appears in the case of the application of the renovated scheme.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.15 no.4
• /
• pp.304-311
• /
• 2013

There have been increasing cases for farmers to install automated weather stations (AWS) at their farms and orchards in order to take countermeasures to more frequent weather disasters caused by climate variability and weather extremes. Although raw data are the same, the additive values as agrometeorological information may vary depending on data processing methods. User demands on appropriate information could also be different among crop species, cropping systems and even cultivars. We designed an internet based AWS data processing and display system to help diverse users (e.g., farmers), extension workers to access their weather data on specific demands. The system was implemented at a rural catchment with 52 $km^2$ land area where 14 automated weather stations are in operation. This note introduces the system and describes the major modules in detail. By linking regional AWS networks, a feasibility for this system as an early warning system is also discussed.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.19 no.2
• /
• pp.117-131
• /
• 2016

This study aims to analyze the spatial accessibilities to urban greens considering the catchment areas of urban parks to improve those areas with lower spatial accessibility in the neighborhood units. Nam-gu in Daegu was selected as the study area. In the results of the analysis of 16 existing parks, Daemyung6-dong and Daemyung5-dong had high ratios of green service area to administrative district, with values of 94.4% and 92.3%, respectively. Low ratios of green service area(vulnerable area of green service) were recorded in Icheondong(1.6%) and Daemyung10-dong(24.1%). However, the ratio of Icheondong may increase by 88.6%, when the 12 unexecuted urban parks are established. The ratio of Daemyung10-dong can also increase up to 40.1% by establishing green spaces in public institutions such as government offices and schools. This study suggests possibilities to improve the spatial accessibilities to urban parks and indicates the policies required for enhancing the even distribution of green spaces.

• Journal of Korea Water Resources Association
• /
• v.47 no.9
• /
• pp.777-787
• /
• 2014

Stormwater pipe systems are most commonly used to discharge rainwater from the urban catchment covered by the impervious area. To design stormwater pipe and rainwater pumping station, frequency analysis is implemented using historical rainfall and the design rainfall is timely distributed using theoretical shape such as Huff distribution. This method cannot consider the rainfall intensity variation caused by climate change which is type of uncertainty. Therefore, in this study, runoff from Gasan1 stormwater pumping stations catchment is calculated using design rainfall distributed by the 2nd quartile distribution method and the historical rainfall events. From the analysis, the nodal flooding in the urban catchment is likely caused by the high peak rainfall event rather than the large amount of rainfall. The linear regression analysis is implemented. As a result, when several storms have the same amount of rainfall, the nodal flooding in the stormwater pipe systems could be caused by the high peak of storm events. Since as the storm duration become short, the peak rainfall become high, the nodal flooding likely become severe with the short storm duration. The uncertainty in the peak data of design rainfall is analyzed and this uncertainty has to be consider in the stormwater pipe design process.

• Journal of Korea Water Resources Association
• /
• v.41 no.3
• /
• pp.341-351
• /
• 2008

Since the damage from the torrential rain increases recently due to climate change and global warming, the significance of flood forecasting and warning becomes important in medium and small streams as well as large river. Through the preprocess and main processes for estimating runoff, diverse errors occur and are accumulated, so that the outcome contains the errors in the existing flood forecasting and warning method. And estimating the parameters needed for runoff models requires a lot of data and the processes contain various uncertainty. In order to overcome the difficulties of the existing flood forecasting and warning system and the uncertainty problem, ANFIS(Adaptive Neuro-Fuzzy Inference System) technique has been presented in this study. ANFIS, a data driven model using the fuzzy inference theory with neural network, can forecast stream level only by using the precipitation and stream level data in catchment without using a lot of physical data that are necessary in existing physical model. Time series data for precipitation and stream level are used as input, and stream levels for t+1, t+2, and t+3 are forecasted with this model. The applicability and the appropriateness of the model is examined by actual rainfall and stream level data from 2003 to 2005 in the Tancheon catchment area. The results of applying ANFIS to the Tancheon catchment area for the actual data show that the stream level can be simulated without large error.

• Journal of Korean Society of Forest Science
• /
• v.103 no.1
• /
• pp.80-86
• /
• 2014

$^{210}Pb$ dating was conducted to examine the influence of land use changes in the forest catchment on lake sedimentation. The Kushiro River, into which Lake Takkobu drains under regular flow conditions, contributed to an increased sedimentation rate in sampling point at the lake outflow because turbid water from the Kushiro River flows back into Lake Takkobu during floods. The elevated sediment flux from the catchment dilutes the $^{210}Pb$ concentration in sampling points at the inflow of the Takkobu River and the lake outflow, which causes fluctuations in the $^{210}Pb$ concentrations in sediment cores. The $^{210}Pb$ dating was estimated using the CRS (Constant rate of Supply) model. The dates by the CRS model in Lake Takkobu profiles were in good agreement with the dates by $^{137}Cs$. Sedimentation rates reconstructed for the past 100-150 years suggested that sedimentation rates increased drastically following land use changes. While a natural sedimentation rate of $0.01-0.03g/cm^2/year$ is observed until the 1880s, whereas lake sedimentation accelerated to $0.03-0.09g/cm^2/year$ following land use changes such as deforestation and channelization, between the 1880s and 1940s. In particular, the sedimentation rates have been associated with deforestation, channelization, agricultural development and road construction, since the 1980s, and these rates were about 9-28 times higher than those under natural conditions, leading to accelerated lake shallowing.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.26 no.4
• /
• pp.52-65
• /
• 1984

In general precise estimation of hourly of daily distribution of the long-term run-off should be very important in a design of source of irrigation. However, there have not been a satisfying method for forecasting of stationar'y long-term run-off in Korea. Solving this problem, this study introduces unit-hydrograph method frequently used in short-term run-off analysis into the long-term run-off analysis, of which model basin was selected to be Sumgin-river catchment area. In the estimation of effective rainfall, conventional method neglects the Soil moisture condition of catchment area, but in this study, the initial discharge (qb) occurred just before rising phase of the hydrograph was selected as the index of a basin soil moisture condition and then introduced as 3rd variable in the analysis of the reationship between cumulative rainfall and cumulative loss of rainfall, which built a new type of separation method of effective rainfall. In next step, in order to normalize significant potential error included in hydrological data, especially in vast catchment area, Snyder's correlation method was applied. A key to solution in this study is multiple correlation method or multiple regressional analysis, which is primarily based on the method of least squres and which is solved by the form of systems of linear equations. And for verification of the change of characteristics of unit hydrograph according to the variation of a various kind of hydrological charateristics (for example, precipitation, tree cover, soil condition, etc),seasonal unit hydrograph models of dry season(autumn, winter), semi-dry season (spring), rainy season (summer) were made respectively. The results obtained in this study were summarized as follows; 1.During the test period of 1966-1971, effective rainfall was estimated for the total 114 run-off hydrograph. From this estimation results, relative error of estimation to the ovservation value was 6%, -which is mush smaller than 12% of the error of conventional method. 2.During the test period, daily distribution of long-term run-off discharge was estimated by the unit hydrograph model. From this estimation results, relative error of estimation by the application of standard unit hydrograph model was 12%. When estimating by each seasonal unit bydrograph model, the relative error was 14% during dry season 10% during semi-dry season and 7% during rainy season, which is much smaller than 37% of conventional method. Summing up the analysis results obtained above, it is convinced that qb-index method of this study for the estimation of effective rainfall be preciser than any other method developed before. Because even recently no method has been developed for the estimation of daily distribution of long-term run-off dicharge, therefore estimation value by unit hydrograph model was only compared with that due to kaziyama method which estimates monthly run-off discharge. However this method due to this study turns out to have high accuracy. If specially mentioned from the results of this study, there is no need to use each seasonal unit hydrograph model separately except the case of semi-dry season. The author hopes to analyze the latter case in future sudies.

• Journal of Korea Water Resources Association
• /
• v.45 no.12
• /
• pp.1293-1307
• /
• 2012

This study is to evaluate the RHESSys (Regional Hydro-Ecological Simulation System) simulated streamflow (Q), evapotranspiration (ET), soil moisture (SM), gross primary productivity (GPP) and photosynthetic productivity (PSNnet) with the measured data. The RHESSys is a hydro-ecological model designed to simulate integrated water, carbon, and nutrient cycling and transport over spatially variable terrain. A 8.5 $km^2$ Seolma-cheon catchment located in the northwest of South Korea was adopted. The catchment covers 90.0% forest and the dominant soil is sandy loam. The model was calibrated with 2 years (2007-2008) daily Q at the watershed outlet and MODIS (Moderate Resolution Imaging Spectroradiometer) GPP, PSNnet and 3 year (2007～2009) daily ET data measured at flux tower using the eddy-covariance technique. The coefficient of determination ($R^2$) and the Nash-Sutcliffe model efficiency (ME) for Q were 0.74 and 0.63, and the average $R^2$ for ET and GPP were 0.54 and 0.93 respectively. The model was validated with 1 year (2009) Q and GPP. The $R^2$ and the ME for Q were 0.92 and 0.84, the $R^2$ for GPP were 0.93.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2011.05a
• /
• pp.14-14
• /
• 2011

Groundwater in the Waikatoregion is a valuable resource for agriculture, water supply, forestry and industries. The 434,000 ha study area comprises the upper Waikato River catchment from the outflow of Lake Taupo (New Zealand's largest lake) through to Lake Karapiro (a man-made hydro lake with high recreational value) (Figure 1). Water quality in the area is naturally high. However, there are indications that this quality is deteriorating as a result of land use intensification and deforestation. Compounding this concern for decision makers is the lag time between land use changes and the realisation of effects on groundwater and surface water quality. It is expected that the effects of land use changes have not yet fully manifested, and additional intensification may take decadesto fully develop, further compounding the deterioration. Consequently, Environment Waikato (EW) have proposed a programme of work to develop a groundwater model to assist managing water quality and appropriate policy development within the catchment. One of the most important and critical decisions of any modelling exercise is the choice of the modelling platform to be used. It must not inhibit future decision making and scenario exploration and needs to allow as accurate representation of reality as feasible. With this in mind, EW requested that two modelling platforms, MODFLOW/MT3DMS and FEFLOW, be assessed for their ability to deliver the long-term modelling objectives for this project. The two platforms were compared alongside various selection criteria including complexity of model set-up and development, computational burden, ease and accuracy of representing surface water-groundwater interactions, precision in predictive scenarios and ease with which the model input and output files could be interrogated. This latter criteria is essential for the thorough assessment of predictive uncertainty with third-party software, such as PEST. This paper will focus on the attributes of each modelling platform and the comparison of the two approaches against the key criteria in the selection process. Primarily due to the ease of handling and developing input files and interrogating output files, MODFLOW/MT3DMS was selected as the preferred platform. Other advantages and disadvantages of the two modelling platforms were somewhat balanced. A preliminary regional groundwater numerical model of the study area was subsequently constructed. The model simulates steady state groundwater and surface water flows using MODFLOW and transient contaminant transport with MT3DMS, focussing on nitrate nitrogen (as a conservative solute). Geological information for this project was provided by GNS Science. Professional peer review was completed by Dr. Vince Bidwell (of Lincoln Environmental).