• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.335-335
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• 2011

토양유실은 농업환경지표를 비롯한 국제 규범에서 농업에 의한 환경오염의 핵심문제로 제기되고 있다. 이러한 토양유실의 문제점을 해결하기 위해 USLE를 기반으로 한 SATEEC모형을 사용하여 토양유실량 및 유사량을 산정하였다. SATEEC모형은 USLE입력자료와 DEM을 이용하여 산정된 토양유실량 과 GA-SDR모듈을 통해 산정된 유달률(Sediment Delivery Ratio, SDR)을 통하여 최종유출구에서의 유사량을 산정한다. 많은 연구자들은 최종유출구에서의 유사량을 실측유사량과 비교하여 비슷하게 모의되면 유역의 특성을 잘 반영한다고 판단하므로 SATEEC모형의 단점인 토양유실량이 과하게 산정되는 문제점을 중요하게 생각하지 않는다. 하지만 SATEEC 모형의 결과값인 유사량의 신뢰도를 향상시키기 위해서는 토양유실량 검증을 통한 정확한 입력자료 구축이 필요하다. 따라서 본 연구에서는 여러개의 토양유실량 시나리오를 만들어 이에 따른 SATEEC 모형의 유사량을 비교/평가하고, 이를 이용하여 토양유실량의 검증이 필요함을 제시하고자 한다. 본 연구에서 사용한 토양유실량 시나리오는 총 4개로써, 시나리오 1은 SATEEC모형을 이용하여 산정된 토양유실량이며, 시나리오2~4는 ArcGIS를 사용하여 기존의 토양유실량 값에 ${\pm}0.25$의 범위를 주어 새롭게 산정된 토양유실량으로 SATEEC모형을 이용한 유사량 산정시 입력자료로 활용하였다. 그 결과 SATEEC모형을 이용하여 산정된 토양유실량은 시나리오별로 차이를 보였다. 또한 SATEEC GA-SDR모듈을 통해 예측된 토양유실량 값과 실측유사량을 이용하여 유달률을 산정하였으며 유달률도 토양유실량 시나리오별로 차이를 보였다. 따라서 SATEEC모형을 이용하여 최종유출구에서의 유사량 산정 결과 토양유실량의 차이에도 불구하고 유사량은 거의 비슷한 값을 나타내고 있으며, 최종유출구에서의 모의된 예측 유사량이 실측유사량과 비교 시 R2=0.688, EI=0.643 정도로 실측유사량과 비슷한 경향을 나타냈다. 따라서 SATEEC모형을 이용하여 유사량 산정시 먼저 문헌을 통한 토양유실량 검증이 필요하리라 판단되며, 문헌을 통해 토양유실량 검증 후 정확한 입력자료를 구축하여 유역에서의 유사량 저감을 위한 최적관리 기법 분석에 사용할 수 있도록 프로세서를 구축해야 할 것이라 판단된다.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.1
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• pp.1-16
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• 2020

The APEX model has been developed for assessing agricultural management efforts and their effects on soil and water at the field scale as well as more complex multi-subarea landscapes, whole farms, and watersheds. Recently, a key component of APEX application, named APEX-Paddy, has been modified for simulating water quality by considering paddy rice management practices. In this study, the performance of the APEX-Paddy model was evaluated using field data at Iksan experimental paddy sites in Korea. The discharge and pollutant load data during 2013 and 2014 were used to both manually and automatically calibrate the model. The APEX auto-calibration tool (APEX-CUTE 4.1) was used for model calibration and sensitivity analysis. Results indicate that APEX-Paddy reasonably performs in predicting runoff discharge rate and nitrogen yield. However, sediment and phosphorus yield is not correctly predicted due to the limitation of model schemes. With APEX-Paddy, the performance in reproducing the discharge and nitrogen yield is found to be a satisfactory level after manual calibration. The manually calibrated model performed better than the automatically calibrated model in nearly all comparisons. For runoff, manual calibration reduced PBIAS while R² and NSE values of the automatically calibrated model were the same as the manual calibration. For T-N, NSE and PBIAS were reduced when using manual calibration, whereas R² value was the same as manual calibration. The limitation of the APEX-Paddy model for predicting sediment, as well as the phosphorous yield, was discussed in this study.

• Journal of Soil and Groundwater Environment
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• v.14 no.3
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• pp.57-67
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• 2009

In soil and sediment environment, microorganisms play major roles in biochemical cycles of ecological significant elements. Because of its ecological significance, microbial diversity and community structure information are useful as indexes for assessing the quality of subsurface ecological environment and bioremediation. To achieve more accurate assessment, it is requested to gain sufficient yield and purity of DNA extracted from various soil and sediment samples. Although there have been a large number of basic researches regarding soil and sediment DNA extraction methods, little guideline information is given in literature when choosing optimal DNA extraction methods for various purposes such as environmental ecology impact assessment and bioremediation capability evaluation. In this study, we performed a thorough literature review to compare the characteristics of the current DNA extraction methods from soil and sediment samples, and discussed about considerations when selecting and applying DNA extraction methods for environmental impact assessment and bioremediation capability evaluation. This review suggested that one approach is not enough to gain the suitable quantity and yield of DNA for assessing microbial diversity, community structure and population dynamics, and that a careful attention has to be paid for selecting an optimal method for individual environmental purpose.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.4
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• pp.89-93
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• 2010

It is well known that the drastic change of hydrological characteristics of an urbanized basin causes severe runoff, sediment yield, and peak flow. High vulnerability of urban flood disasters is caused by land-use change and development of a basin. A typical site suffering urbanization was selected and the experimental site has being operated last three years. Hydrological and hydraulic characteristics of the urbanizing basin were examined by observation of runoff, sediment loads and precipitation with T/M. The effects of land-use change were analyzed by examination of the hydrological characteristics, such as run-off ratio (runoff volume/rainfall volume), sediment yields. Runoff coefficient of rational equation was increased as basin was urbanized. Suspended sediment yields due to a urban development activities were raised almost 10 times compare to undisturbed condition for small runoff less than 1 cms. Meanwhile, no big change could be detected for bed loads.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.241-246
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• 2005

Doam watershed is located at alpine areas in the Kangwon province. The annual average precipitation, including snow accumulation during the winter, at the Doam watershed is significantly higher than other areas. Thus, pollutant laden runoff and sediment discharge from the alpine agricultural fields are causing water quality degradation at the Doam watershed. To estimate soil erosion from the agricultural fields, the Universal Soil Loss Equation (USLE) has been widely used because of its simplicity to use. The USLE rainfall erosivity (R) factor is responsible for impacts of rainfall on soil erosion. Thus, use of constant R factor for the Doam watershed cannot reflect variations in precipitation patterns, consequently soil erosion estimation. In the early spring at the Doam watershed, the stream flow increases because of snow melt, which results in erosion of loosened soil experiencing freezing and thaw during the winter. However, the USLE model cannot consider the impacts on soil erosion of freezing and thaw of the soil. Also, it cannot simulate temporal changes in USLE input parameters. Thus, the Soil and Water Assessment Tool (SWAT) model was investigated for its applicability to estimate soil erosion at the Doam watershed, instead of the widely used USLE model. The SWAT hydrology and erosion/sediment components were validated after calibration of the hydrologic component. The $R^2$ and Nash-Sutcliffe coefficient values are higher enough, thus it was found the SWAT model can be efficiently used to simulate hydrology and sediment yield at the Doam watershed. The effects of snow melt on SWAT estimated stream flow and sediment were investigated using long-term precipitation and temperature data at the Doam watershed. It was found significant amount of flow and sediment in the spring are contributed by melting snow accumulated during the winter. Thus, it is recommend that the SWAT model capable of simulating snow melt and long-term weather data needs to be used in estimating soil erosion at alpine agricultural land instead of the USLE model for successful soil erosion management at the Doam watershed.

• Journal of the korean society of oceanography
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• v.31 no.2
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• pp.43-54
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• 1996

Jinhae Bay, one of the largest tidal bays on the southern coast of Korea, is an area with thick accumulations of recent, fine-grained sediments, mainly supplied from the Nakdong River. The preponderance of silt and clay particles reflects the large quantity of sediments transported in suspension. Although the clay mineral assemblage is similar to that derived from the nearby Nakdong River, relatively high concentration (3-9%) of smectite suggests some local input of fine particles from several streams around the bay or some contribution from the offshore water that may be influenced by the Tsushima Current. The content of organic matters in sediments is as high as 12%, and their C/N ratios imply that they are comprised of mixtures derived from marine plankton and terrestrial plants. $^{210}Pb$ excess activity profiles of sediment cores yield an average sedimentation rate (a 100-year time scale) of about 2-5 mm/yr, which coincides well with the long-term sedimentation rate (a 1000-year time scale) estimated from the sediment isopach map. On the basis of sediment bulk density and sedimentation rate, an annual sink of mud in the bay is estimated approximately 1.0 ${\times}$ $10^{6}$ tons per year.

• Journal of Korean Society of Disaster and Security
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• v.15 no.1
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• pp.35-46
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• 2022

In this study, the amount of debris flow was calculated through the empirical equations of RUSLE, NILIM, and Marchi, which are widely used to calculate areas affected by debris flow, and debris flow measured through precise measurements and field surveys was compared. The RUSLE method over estimated by 2.13 times in the average sense compared with the measured sediment quantify and Marchi's empirical equation over estimated by 2.83 times while NILIM's empirical equation 1.26 times, which is the lowest error among the three empirical equation.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1008-1013
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• 2007

The objectives of the paper were to identify appropriate best management practices (BMPs) for reducing nonpoint source (NPS) pollutant loadings and to simulate the effects of the application of the several BMP scenarios on the study watershed using Agricultural Nonpoint Source (AGNPS) model. AGNPS model was calibrated and validated for runoff, sediment yield, and nutrient components using the observed hydrologic and water quality data. The simulated runoff, sediment, and nutrient components were well agreed with observed data. The validated AGNPS was applied to estimate the NPS pollution removal efficiency for BMP scenarios which were selected considering the pollutant characteristics of the study watershed.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.862-865
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• 2012

유사량은 하천의 단면을 단위시간 동안 통과하는 토사의 양을 의미하며, 하천 구조물의 설계 및 유지관리를 위한 기본자료로 활용된다. 유사량은 하천 유역의 지형적인 특성과 기상요소에 영향을 받으며, 이를 규명하기 위한 많은 연구들이 수행되어 왔다. GIS기반의 유사량 예측모델로서 국내에서는 개정범용토양유실공식과 유사운송비(Sediment Delivery Ratio)를 이용하여 유역단위 유사량을 예측하는 연구가 이루어져왔다. Gavrilovi$\acute{c}$ 모델은 유역의 총 연유사량을 예측하고 토양침식의 정도를 정량화할 수 있는 경험적 모형으로 지질 및 토양, 지형조건, 기후인자(연평균 강우량, 연평균 온도), 토지이용의 6가지 입력변수로 구성되어 있다. 본 연구는 Gavrilovi$\acute{c}$ 모델의 국내 적용성을 검토하기 위한 것으로서, 왕숙천 유역을 대상으로 Gavrilovi$\acute{c}$ 모델을 적용하여 유사량을 산정해본 결과, 실측값을 약 20% 내외로 비교적 근사하게 추정할 수 있음을 알 수 있었다.

• Journal of Korean Society on Water Environment
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• v.23 no.4
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• pp.467-473
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• 2007

Although the dominant land use at the Imha-dam watershed is forest areas, soil erosion has been increasing because of intensive agricultural activities performed at the fields located along the stream for easy-access to water supply and relatively favorable topography. In addition, steep topography at the Imha-dam watershed is also contributing increased soil erosion and sediment loads. At the Imha-dam watershed, outflow has increased sharply by the typhoons Rusa and Maemi in 2002, 2003 respectively. In this study, the Soil and Water Assessment Tool (SWAT) model was evaluated for simulation of flow and sediment behaviors with long-term temporal and spatial conditions. The precipitation data from eight precipitation observatories, located at Ilwol, Subi and etc., were used. There was no significant difference in monthly rainfall for 8 locations. However, there was slight differences in rainfall amounts and patterns in 2003 and 2004. The topographical map at 1:5000 scale from the National Geographic Information Institute was used to define watershed boundaries, the detailed soil map at 1:25,000 scale from the National Institute of Highland Agriculture and the land cover data from the Korea Institute of Water and Environment were used to simulate the hydrologic response and soil erosion and sediment behaviors. To evaluate hydrologic component of the SWAT model, calibration was performed for the period from Jan. 2002 to Dec. 2003, and validation for Jan. 2004 to Apr. 2005. The $R^2$ value and El value were 0.93 and 0.90 respectively for calibration period, and the $R^2$ value and El value for validation were 0.73 and 0.68 respectively. The $R^2$ value and El value of sediment yield data with the calibrated parameters was 0.89 and 0.84 respectively. The comparisons with the measured data showed that the SWAT model is applicable to simulate hydrology and sediment behaviors at Imha dam watershed. With proper representation of the Best Management Practices (BM Ps) in the SWAT model, the SWAT can be used for pre-evaluation of the cost-effective and sustainable soil erosion BMPs to solve sediment issues at the Imha-dam watershed. In Korea, the Universal Soil Loss Equation (USLE) has been used to estimate the soil loss for over 30 years. However, there are limitations in the field scale mdel, USLE when applied for watershed. Also, the soil loss changes temporarily and spatially, for example, the Imha-dam watershed. Thus, the SW AT model, capable of simulating hydrologic and soil erosion/sediment behaviors temporarily and spatially at watershed scale, should be used to solve the muddy water issues at the Imha-dam watershed to establish more effective muddy water reduction countermeasure.