• Membrane and Water Treatment
• /
• v.10 no.1
• /
• pp.45-55
• /
• 2019

Climate change has significantly affected the rainfall characteristics which can influence the pollutant build-up and wash-off patterns from the catchment. Therefore, this study explored the influence of varying rainfall characteristics on urban and agricultural runoff pollutant export using statistical approaches. For this purpose, Mann-Kendall and Pettitt's test were applied to detect the trend and breakpoint in rainfall characteristics time series. In addition, double mass curve and correlation analysis were used to drive the relationship between rainfall-runoff and pollutant exports from both catchments. The results indicate a significant decreased in total rainfall and average rainfall intensity, while a significant increased trend for antecedents dry days and total storm duration over the study periods. The breakpoint was determined to be 2013 which shows remarkable trend shifts for total rainfall, average rainfall intensity and antecedents dry days except total duration. Double mass curve exhibited a straight line with significant rainfall-runoff relationship indicates a climate change effect on both sites. Overall, higher pollutant exports were observed at both sites during the baseline period as compared to change periods. In agricultural site, most of the pollutants exhibited significant (p< 0.05) association with total rainfall, average rainfall intensity and total storm duration. In contrast, pollutants from urban site significantly correlated with antecedent dry days and average rainfall intensity. Thus, total rainfall, average rainfall intensity and total duration were the significant factors for the agricultural catchment while, antecedents dry days and average rainfall intensity were key factors in build-up and wash-off from the urban catchment.

• Journal of People, Plants, and Environment
• /
• v.24 no.1
• /
• pp.39-51
• /
• 2021

Background and objective: Urban topology can be characterized as impervious, which changes the hydrologic features of an area, increasing surface water flow during local heavy rain events. The pluvial flooding is also influenced by the vertical structures of the urban area. This study suggested a modified digital elevation model (DEM) to identify changes in urban hydrological conditions and segmentalized urban micro catchment areas using a geographical information system (GIS). Methods: This study suggests using a modified DEM creation process based on Rolling Ball Method concepts along with a GIS program. This method proposes adding realized urban vertical data to normal DEM data and simulating hydrological analyses based on RBM concepts. The most important aspect is the combination of the DEM with polygon data, which includes urban vertical data in three datasets: the contour polyline, the locations of buildings and roads, and the elevation point data from the DEM. DEM without vertical data (DCA) were compared with the DEM including vertical data (VCA) to analyze catchment areas in Shin-wol district, Seoul, Korea. Results: The DCA had 136 catchments, and the area of each catchment ranged from 3,406 m² to 423,449 m². The VCA had 2,963 catchments, with the area of each ranging from 50 m² to 16,209 m². The most important finding is that in the overlapped VCA; the boundary of areas directly affected by flooding and the direction of surface water flow could be identified. Flooding data from September 21, 2010 and July 27, 2011 in the Shin-wol district were applied as ground reference data. The finding is that in the overlapped VCA; the boundary of areas directly affected by flooding and the direction of surface water flow could be identified. Conclusion: The analysis of the area vulnerable to surface water flooding (SWF) was more accurately determined using the VCA than using the DCA.

• Journal of Korean Society of Disaster and Security
• /
• v.16 no.2
• /
• pp.99-104
• /
• 2023

In recent years, the occurrence of abnormal weather has increased rapidly, increasing the frequency of torrential rain. As a result, stable water resource management is difficult, and human and material damage is increasing. Various measures are being established to reduce damage caused by torrential rains, but small-scale mountain catchments are relatively difficult to manage due to lack of basic plan. In this study, the risk of flooding was evaluated using the rainfall-flow model in the Yeonhwa-dong catchment national park among national parks in Korea. The Yeonhwa-dong catchment of Mt. Sobaeksan was simulated to cause flooding when rainfall of more than 50 years occurred, and it was confirmed that there was a high risk of water resource structures, safety facilities, and trails.

• Journal of Environmental Impact Assessment
• /
• v.13 no.2
• /
• pp.73-86
• /
• 2004

The objective of this research was to estimate residents' willingness-to-pay using contingent valuation method and to investigate their environmental sensibilities prior to conduct the costbenefit analysis on the watershed management program of integrated sewerage construction and operation in the catchment of Dam Chung-Ju. A set of questionnaire was prepared and asked to 1,200 residents at downstream area as well as upstream area of Dam Chung-Ju. As a result, environmental sensibility of the residents living in the catchment of upstream of Lake Chung-Ju seemed very high. However, the substantial practice in their own life for conserving their environment was inactive, although residents' efforts trying to collect and dispose garbages in separate containers and to minimize the waste discharge load were actually made. The willingness-to-pay on each month for 20 years was estimated as 4,841 wons for the openended question and 3,411 wons for the close-ended question. Factorial analysis was also performed to obtain correlation among the questions asked. Seven groups of the correlated questions were identified and their contribution to the estimated willingness-to-pay was analyzed.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.5 no.2 s.17
• /
• pp.17-28
• /
• 2005

The objective of this study is to evaluate the critical duration between detention facility and flood control facility of small size catchment. 4 small size catchments are applied for hydrological analysis and rainfall excess is computed by using the NRCS Runoff Curve Number method. The critical duration of detention facility and flood control facility is evaluated using the concept of allowable release rate. The conclusions studied in this study are as follows; (1) The type of temporal pattern of design rainfall which causes maximum storage ratio has resulted in Huff's 2 quartile in case of the use of the concept of allowable release rate. (2) Based on (1) of conclusion, the critical durations of flood control facility are similar to those of detention facility, which is used for uncontrolled single detention pond.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.21 no.1
• /
• pp.13-23
• /
• 1979

The predictien of a design flood hydrograph at a particular site on a river may be based on the derivation of a discharge or stage hydrograph at an upstream section, together with a method to route this hydrograph along the rest of the river. In order to limit this investigation to cases where the assumption like uniform rainfall may be reasonably valid, the derivation of unit hydrographs has been limited to catchment with an area less than 500 km2. Consequently, flood routing methods provide a useful tool for the analysis of flooding in all but the smaller catchment, particularly where the shape of the hydrograph as well as the peak value is required. The author, therefore, will introduce here a flood routing method on the open channel with a peak discharge of the catchment area concerned. The importance of being able to route floods accurately is also reflected in the large number of flood routing method which have been developed since the year 1900. There are the modified puls method, Steinberg method, Goodrich method, Ekdahl method, Tatum's mean continuously Equation, wisler-Brater method, Muskingum, chung, and Muskingum-cunge (M-C) method and so on. The author will try to introduce a flood routing method which is revised Muskingum-cunge method. In calculating flood routing by the M-C method, whole variable parameters on the river were assumed to almost uniform values from the upstream to the downstream. In the results, the controlled flood rates at the 40km downstream on the river is appeared to decrease 22m$^3$/sec or 12 percent of the peak flood 170m$^3$/sec.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.54 no.1
• /
• pp.27-38
• /
• 2012

This study is to analyse the hydrological behavior of agricultural reservoir using CAT (Catchment hydrologic cycle Assessment Tool). The CAT is a water cycle analysis model in order to quantitatively assess the characteristics of the short/long-term changes in watershed. It supports the effective design of water cycle improvement facilities by supplementing the strengths and weaknesses of existing conceptual parameter-based lumped hydrologic models and physical parameter-based distributed hydrologic models. The CAT especially supports the analysis of runoff processes in paddy fields and reservoirs. To evaluate the impact of agricultural reservoir operation and irrigation water supply on long-term rainfall-runoff process, the CAT was applied to Idong experimental catchment, operated for research on the rural catchment characteristics and accumulated long term data by hydrological observation equipments since 2000. From the results of the main control points, Idong, Yongdeok and Misan reservoirs, the daily water levels of those points are consistent well with observed water levels, and the Nash-Sutcliffe model efficiencies were 0.32~0.89 (2001~2007) and correlation coefficients were 0.73~0.98.

• Journal of Environmental Science International
• /
• v.25 no.1
• /
• pp.41-56
• /
• 2016

In recent localized heavy rainfalls have been arising from abnormal climate change. People are concerning about damages with increasing the frequency of flooding. Therefore, we need to understand river hydraulic characteristics and management to reduce damage from flooding. To study hydraulic characterization of Sincheon experimental catchment HEC-RAS (Hydrologic Engineering Center River Analysis System) model which provided by U.S Army Corps of Engineers (USACE) was applied. This study analyzed and compared water level the frequency flood for 100 years and 200 years by clark unit Hydrography. The change of the water level of Daejeon bridge, Sincheon bridge and Singi bridge showed increased for all conditions. The flow rate for the Daejeon bridge and the Sincheon bridge showed an increase, but the Sinki bridge showed a decreasing flow rate overally, except for 1hour-100 years. The verification result showed that the model was able to simulate the water level with 0.4709 coefficient of determination and error ration ranging from 1 to 3%.

• Journal of Wetlands Research
• /
• v.22 no.3
• /
• pp.200-216
• /
• 2020

Many studies conducted in Kenya regarding water resource governance have focused on the mandate of Water Resource Users Associations (WRUAs) with less attention being accorded to their effectiveness in conservation of wetlands. This study assessed the effectiveness of WRUA committees, and challenges faced in conservation of Rwamuthambi Sub-catchment. The study employed exploratory descriptive research design. Data was collected through questionnaires, semi-structured interviews, observations and review of secondary data. Chi square and descriptive statistics was used to analyze the data. The survey results revealed that only 15% of WRUA committee understood water resources management while 35% were aware of relevant legislations. Factors of wetland degradation showed significant association with existence of WRUA (χ2 (4, N=180) = 20.46, p< .01) where (χ2- chi square (degrees of freedom, N = sample size) = chi-square statistic value, p = p value), although WRUA contributions were perceived differently per agro-ecological zone (χ2 (8, N=147) = 15.51, p>.05). Challenges unearthed were inadequate financial and human resources, lack of understanding, ineffective collaborative governance, poor support from county government and private ownership of riparian land reserve. There is need for WRUAs to embrace collaborative governance for effective conservation of wetlands. Integration of sub catchment management plan with county land use plans and policy review is also required.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.1
• /
• pp.89-97
• /
• 2015

This study is to assess the effect of non-point source pollution discharge loads between tillage and no-tillage applications for upland crop areas using SWAT (Soil and Water Assessment Tool) watershed modeling. For Byulmi-cheon small rural catchment ($1.17km^2$) located in upstream of Gyeongan-cheon watershed, the rainfall, discharge and stream water quality have been monitored in the catchment outlet since 2011. The SWAT model was calibrated and validated in hourly basis using 19 rainfall events during 2011-2013. The average Nash-Sutcliffe model efficiency and $R^2$ (determination coefficient) for streamflow were 0.67 and 0.79 respectively. Using the 10 % surface runoff reduction from experiment results for no-tillage condition in field plots of 3 % and 8 % slopes under sesami cultivation, the soil saturated hydraulic conductivity for upland crop areas was adjusted from 0.001 mm/hr to 0.0025 mm/hr in average. Under the condition, the catchment sediment, T-N (total nitrogen, TN), and T-P (total phosphorus, TP) discharge loads were reduced by 6.9 %, 7.4 %, and 7.7 % respectively.