토지분류 정확성에 따른 SWAT 예측 오류 평가

허성구(Sung Gu Heo),안재훈(Jae Hun Ahn),유동선(Dong Sun Yoo),김기성(Ki Sung Kim),임경재(Kyoung Jae Lim) 한국생물환경조절학회 2008 한국생물환경조절학회 학술발표논문집 Vol.17 No.1

고령지 농경지에서 융설에 의한 토양유실량 모의

허성구 ( Heo Sung-gu ),임경재 ( Lim Kyoung-jae ),김기성 ( Kim Ki-sung ),사공명 ( Myung Sagong ),안재훈 ( An Jae-hun ) 한국농공학회 2005 한국농공학회 학술대회초록집 Vol.2005 No.-

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 R² 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.

도암댐 유역의 산림 파편화에 따른 수(水)환경 영향 평가

허성구 ( Sung-gu Heo ),김기성 ( Ki-sung Kim ),안재훈 ( Jae-hun Ahn ),윤정숙 ( Jong-suk Yoon ),임경재 ( Kyoung Jae Lim ),최중대 ( Joongdae Choi ),신용철 ( Yong-chul Shin ),유창원 ( Changwon Lyou ) 한국농공학회 2006 한국농공학회 학술대회초록집 Vol.2006 No.-

The water quality impacts of forest fragmentation at the Doam-dam watershed were evaluated in this study. For this ends, the watershed scale model, Soil and Water Assessment Tool (SWAT) model was utilized. To exclude the effects of different magnitude and patterns in weather, the same weather data of 1985 was used because of significant differences in precipitation in year 1985 and 2000. The water quality impacts of forest fragmentation were analyzed temporarily and spatially because of its nature. The flow rates for Winter and Spring has increased with forest fragmentations by 8,366㎥/month and 72,763㎥/month in the S1 subwatershed, experiencing the most forest fragmentation within the Doam-dam watershed. For Summer and Fall, the flow rate has increased by 149,901 ㎥/month and 107,109㎥/month, respectively. It is believed that increased flow rates contributed significant amounts of soil erosion and diffused nonpoint source pollutants into the receiving water bodies. With the forest fragmentation in the S1 watershed, the average sediment concentration values for Winter and Spring increased by 5.448mg/L and 13.354mg/L, respectively. It is believed that the agricultural area, which were forest before the forest fragmentation, are responsible for increased soil erosion and sediment yield during the spring thaw and snow melts. For Spring and Fall, the sediment concentration values increased by 20.680mg/L and 24.680mg/L, respectively. Compared with Winter and Spring, the increased precipitation during Summer and Fall contributed more soil erosion and increased sediment concentration value in the stream. Based on the results obtained from the analysis performed in this study, the stream flow and sediment concentration values has increased with forest fragmentation within the S1 subwatershed. These increased flow and soil erosion could contribute the eutrophication in the receiving water bodies. This results show that natural functionalities of the forest, such as flood control, soil erosion protection, and water quality improvement, can be easily lost with on-going forest fragmentation within the watershed. Thus, the minimize the negative impacts of forest fragmentation, comprehensive land use planning at watershed scale needs to be developed and implemented based on the results obtained in this research.

고랭지 농경지의 토양유실모의를 위한 SWAT 모형의 적용성 평가

허성구 ( Sung Gu Heo ),김기성 ( Ki Sung Kim ),사공명 ( Myung Sagong ),안재훈 ( Joe Hun Ahn ),임경재 ( Kyoung Jae Lim ) 한국농촌계획학회 2005 농촌계획 Vol.11 No.4

객토 농경지의 토양특성을 고려한 도암댐 유역에서의 수문 및 유사 거동 모의

허성구,김재영,유동선,김기성,안재훈,윤정숙,임경재,Heo, Sung-Gu,Kim, Jae-Young,Yoo, Dong-Sun,Kim, Ki-Sung,Ahn, Jae-Hun,Yoon, Jong-Suk,Lim, Kyoung-Jae 한국농공학회 2007 한국농공학회논문집 Vol.49 No.2

The alpine agricultural activities are usually performed at higher and steep areas in nature. Thus, significant amounts of soil erosion are occurring compared with those from other areas. Thus, the soil erosion induced environmental impacts in these areas are getting greater. The Doam watershed is located at alpine areas and it has been well known that the agricultural activities in the watershed are causing accelerated soil erosion and water quality degradations. Many modeling approaches were employed to solve soil erosion and water quality issues. In this study, the Soil and Water Assessment Tool (SWAT) model was utilized to simulate the hydrologic and sediment behaviors in the Doam watershed. In many previous modeling studies, the digital soil map and its corresponding soil properties were used without modification to reflect soil conditioning at many agricultural fields of the Doam watershed. Thus, the soil sample was taken at the agricultural field within the Doam watershed and analyzed for its physical properties. In this study, the digital topsoil properties in the agricultural fields within the Doam watershed were replaced with the soil properties for reconditioned soil analyzed in this study to simulate the impacts of using soil properties for reconditioned soil in hydrologic and sediment modeling at the Doam watershed using the SWAT model. The hydrologic component of the SWAT model was calibrated and validated for measured flow data from 2002 to 2003. The $R^2$ value was 0.79 and the EI value was 0.53 for weekly simulated data. The calibrated model parameters were used for hydrologic component validation and the $R^2$ value was 0.86 and the EI value was 0.74 for weekly data. For sediment comparison, the $R^2$ value was 0.67 and the EI value was 0.59. These statistics improved with the use of soil properties of the reconditioned soil in the field compared with the results obtained without considering soil reconditioning. The simulated sediment amounts with and without considering the soil properties of the reconditioned soil were 284,813 ton and 158,369 ton, respectively. This result indicates that there could be approximately 79% of errors in estimated sediment yield at the Doam watershed, although the model comparison with the measured data gave similar satisfactory statistics with and without considering soil properties from the reconditioned soil.

고랭지 농업의 작물별 객토량 변화에 따른 토양유실 저감 분석

허성구 ( Sung Gu Heo ),전만식 ( Man Sig Jun ),박상헌 ( Sang Hun Park ),김기성 ( Ki Sung Kim ),강성근 ( Sung Keun Kang ),옥용식 ( Yong Sik Ok ),임경재 ( Kyoung Jae Lim ) 한국물환경학회 2008 한국물환경학회지 Vol.24 No.2

There is increased soil erosion potential at highland agricultural crop fields because of its topographic characteristics and site-specific agricultural management practices performed at these areas. The agricultural upland fields are usually located at the sloping areas, resulting in higher soil loss, pesticides, and nutrients in case of torrential rainfall events or typhoon, such as 2002 Rusa and 2003 MaeMi. At the highland agricultural fields, the soil reconditioning have been performed every year to decrease damage by continuous cropping and pests. Also it has been done to increase crop productivity and soil fertility. The increased amounts of soil used for soil reconditioning are increasing over the years, causing significant impacts on water quality at the receiving water bodies. In this study, the field investigation was done to check soil reconditioning status for potato, carrot, and cabbage at the Doam-dam watershed. With these data obtained from the field investigation, the Soil and Water Assesment Tool (SWAT) model was used to simulate the soil loss reduction with environment-friendly and agronomically enough soil reconditioning. The average soil reconditioning depth for potato was 34.3 cm, 48.3 cm for carrot, and 31.2 cm for cabbage at the Doam-dam watershed. These data were used for SWAT model runs. Before the SWAT simulation, the SWAT ArcView GIS Patch, developed by the Kangwon National University, was applied because of proper simulation of soil erosion and sediment yield at the sloping watershed, such as the Doam-dam watershed. With this patch applied, the Coefficient of Determination (R2) value was 0.85 and the Nash-Sutcliffe Model Efficiency (EI) was 0.75 for flow calibration. The R2 value was 0.87 and the EI was 0.85 for flow validation. For sediment simulation, the R2 value was 0.91 and the EI was 0.70, indicating the SWAT model predicts the soil erosion processes and sediment yield at the Doam-dam watershed. With the calibrated and validated SWAT for the Doam-dam watershed, the soil erosion reduction was investigated for potato, carrot, and cabbage. For potato, around 19.3 cm of soil were over applied to the agricultural field, causing 146% of more soil erosion rate, approximately 33.3 cm, causing 146% of more soil erosion for carrot, and approximately 16.2 cm, causing 44% of more soil erosion. The results obtained in this study showed that excessive soil reconditioning are performed at the highland agricultural fields, causing severe muddy water issues and water quality degradation at the Doam-water watershed. The results can be used to develop soil reconditioning standard policy for various crops at the highland agricultural fields, without causing problems agronomically and environmentally.

GIS 기반의 모형을 이용한 도암댐 유역의 산림 파편화에 따른 수(水)환경 영향 평가

허성구 ( Sung Gu Heo ),김기성 ( Ki Sung Kim ),안재훈 ( Jae Hun Ahn ),윤정숙 ( Jong Suk Yoon ),임경재 ( Kyoung Jae Lim ),최중대 ( Joong Dae Choi ),신용철 ( Yong Chul Shin ),유창원 ( Chang Won Lyou ) 한국지리정보학회 2006 한국지리정보학회지 Vol.9 No.4

FRAGSTATS 모형을 이용한 도암댐 유역의 산림 파편화 분석

허성구 ( Sung Gu Heo ),김기성 ( Ki Sung Kim ),안재훈 ( Jae Hun Ahn ),윤정숙 ( Jong Suk Yoon ),임경재 ( Kyoung Jae Lim ),최중대 ( Joong Dae Choi ),신용철 ( Yong Chul Shin ),유창원 ( Chang Won Lyou ) 한국지리정보학회 2007 한국지리정보학회지 Vol.10 No.1

강원도 평창군에 위치한 도암댐 유역은 인간의 개발행위에 따른 산림지역 파편화로 인해 산림지역의 상당부분이 농업/도시 지역으로 변화되어 왔다. 이러한 토지이용변화로 인해 하류 수역에서는 많은 부정적인 영향이 발생하고 있다. 그러나 토지이용변화가 도암댐 유역내 경관에 미치는 영향을 과학적인 분석 툴을 이용하여 수계단위로 분석한 예는 그리 많지 않다. 따라서 본 연구에서는 산림의 파편화가 경관에 미치는 영향을 정량적으로 분석하기 위하여 경관분석 프로그램인 FRAGSTATS를 이용하였다. 복잡한 계산식으로 구성된 경관지수를 자동으로 산출해주는 FRAGSTATS 프로그램은 경관분석에 많이 이용해 왔으나, 각 경관지수별 설명이 충분하지 않아 FRAGSTATS를 처음 사용하는 사용자가 이를 이용하여 정량적 경관분석을 수행하기에는 다소 어려움이 있어 왔다. 따라서 본 연구에서는 경관 파편화가 발생하기 전과 후의 가상적이면서 단순화 된 경관을 구성하여 경관지수를 설명하였다. 본 연구에서 기술된 경관지수를 이용하여 도암댐 유역내에서 산림 파편화가 경관에 미치는 영향을 정량적으로 평가하였다. 총 19개 소유역중 S1 유역이 1985년부터 2000년까지 가장 많은 산림 파편화가 진행된 것으로 분석되었다. 본 연구의 결과는 산림지역의 파편화, 이에 따른 토지이용변화가 수질에 미치는 영향을 수계단위로 평가하는데 매우 유용하게 사용될 수 있으리라 판단되며, FRAGSTATS과 같은 경관분석 프로그램의 결과를 바탕으로 한 환경친화적 토지이용계획을 수립하는데 매우 유용하리라 판단된다. The Doam-dam watershed, located at Kangwon Province, Korea, has been experiencing significant changes in land uses, conversion from forest to agricultural/urban areas, with human involvements. However, no thorough investigation of the landscape impacts of land use changes was performed at this watershed using the scientific analytical tool. Thus, the FRAGSTATS model was utilized to quantitatively analyze the landscape impacts of forest fragmentation in this study. To provide the detailed explanations for 11 landscape indices considered in this study, two artificial and simplified landscapes, before and after fragmentations, were constructed. Using these 11 indices, the landscape impacts of forest fragmentation in 19 subwatersheds of the Doam-dam watershed were analyzed. The S1 subwatershed, one of 19 subwatersheds of the Doam-dam watershed, was found to have experienced the significant forest fragmentation from 1985 to 2000 based on landscape analysis using the FRAGSTATS model. The results obtained in this study can be used to evaluate the water quality impacts of forest fragmentations/land use changes at watershed scale level, and establish environment-friendly land use planning based on the results obtained using landscape analytical tool, FRAGSTATS.

FRAGSTATS 모형을 이용한 도암댐 유역의 경관 분석

허성구 ( Sung-gu Heo ),김기성 ( Ki-sung Kim ),안재훈 ( Jae-hun Ahn ),윤정숙 ( Jong-suk Yoon ),임경재 ( Kyoung Jae Lim ),최중대 ( Yong-chul Shin ),신용철 ( Changwon Lyou ),유창원 ( Joongdae Choi ) 한국농공학회 2006 한국농공학회 학술대회초록집 Vol.2006 No.-

The Doam-dam watershed, located at Kangwon Province, Korea, has been experiencing significant changes in land uses, conversion from forest to agricultural/urban areas, with human involvements. However, no thorough investigation of the landscape impacts of land use changes was performed at this watershed using scientific analytical tool. Thus, the FRAGSTATS model was utilized to quantitatively analyze the landscape impacts of forest fragmentation in this study. To provide the detailed explanations for 11 landscape indices considered in this study, two artificial and simplified landscapes, before and after fragmentations, were constructed. Using these 11 indices, the landscape impacts of forest fragmentation in 19 subwatersheds of the Doam-dam watershed were analyzed. The S1 subwatershed, one of 19 subwatersheds of the Doam-dam watershed, was found to have experienced the significant forest fragmentation from 1985 to 2000 based on landscape analysis. The results obtained in this study can be used to evaluate the water quality impacts of forest fragmentations/landuse changes at watershed scale level, and establish environment-friendly land use planning based on the results obtained using landscape analytical tool, FRAGSTATS.

토지피복도 정확도에 따른 SWAT 예측 오류 평가

허성구 ( Sung Gu Heo ),김기성 ( Ki Sung Kim ),김남원 ( Nam Won Kim ),안재훈 ( Jae Hun Ahn ),박상헌 ( Sang Hun Park ),유동선 ( Dong Seon Yoo ),최중대 ( Joong Dae Choi ),임경재 ( Kyoung Jae Lim ) 한국물환경학회 2008 한국물환경학회지 Vol.24 No.6