• 한국토양비료학회지
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• 제44권6호
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• pp.983-990
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• 2011

Universal Soil Loss Equation (USLE) has been used to estimate potential long-term soil erosion in the fields. However, the USLE does not estimate sediment yield due to lack of module considering sediment delivery ratio (SDR) for watershed application. For that reason, the Sediment Assessment Tool for Effective Erosion Control (SATEEC) system was developed and applied to compute the sediment yield at watershed scale. However, the R factor of current SATEEC Ver. 2.1 was estimated based on 5-day antecedent rainfall, it is not related with fundamental concept of R factor. To compute R factor accurately, the energy of rainfall strikes should be considered. In this study, the R module in the SATEEC system was enhanced using formulas of Williams, Foster, Cooley, CREAMS which could consider the energy of rainfall strikes. The enhanced SATEEC system ver. 2.2 was applied to the Imha watershed and monthly sediment yield was estimated. As a result of this study, the $R^2$ and NSE values are 0.591 and 0.573 for calibration period, and 0.927 and 0.911 for validation period, respectively. The results demonstrate the enhanced SATEEC System estimates the sediment yield suitably, and it could be used to establish the detailed environmental policy standard using USLE input dataset at watershed scale.

• 한국물환경학회지
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• 제35권1호
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• pp.72-77
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• 2019

Soil type in LID infiltration practices plays a major role in runoff reduction efficacy. In this study, the effects of infiltration rate of foundation ground under bioretention on annual runoff reduction rate was evaluated using LIDMOD3 which is a simple excel based model for evaluating LID practices. A bioretention area of about 3.2 % was required to capture surface runoff from an impervious area for a 25.4 mm rainfall event. The relative error of runoff from bioretention using LIDMOD3 is 10 % less than that of SWMM5.1 for a total rainfall event of 257.1 mm during the period of Aug. 1 ~ 18, 2017, hence, the applicability of LIDMOD3 was confirmed. Annual runoff reduction rates for the period 2008 ~ 2017 were evaluated for various infiltration rates of foundation ground under the bioretention which ranged from 0.001 to 0.600 m/day and were converted to annual runoff reduction for hydrologic soil group. The runoff reduction rates within hydrologic soil group C and D were steeply increased through increased infiltration rate but not steep within hydrologic A and B with reduction rates ranging from 53 ~ 68 %. The estimated time required to completely empty a bioretention which has a storage depth of 0.632 m is 3.5 ~ 6.9 days and we could assume that the annual average of antecedent rainfall is longer than 3.5 ~ 6.9 days. Therefore, we recommended B type as the minimum hydrologic soil group installed LID infiltration practices for high runoff reduction rate.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.179-179
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• 2023

This study suggests a new approach of water level forecasting for extended lead times using original data preprocessing with variational mode decomposition (VMD). Here, two machine learning algorithms including light gradient boosting machine (LGBM) and random forest (RF) were considered to incorporate extended lead times (i.e., 5, 10, 15, 20, 25, 30, 40, and 50 days) forecasting of water levels. At first, the original data at two water level stations (i.e., SW173 and SW269 in Bangladesh) and their decomposed data from VMD were prepared on antecedent lag times to analyze in the datasets of different lead times. Mean absolute error (MAE), root mean squared error (RMSE), and mean squared error (MSE) were used to evaluate the performance of the machine learning models in water level forecasting. As results, it represents that the errors were minimized when the decomposed datasets were considered to predict water levels, rather than the use of original data standalone. It was also noted that LGBM produced lower MAE, RMSE, and MSE values than RF, indicating better performance. For instance, at the SW173 station, LGBM outperformed RF in both decomposed and original data with MAE values of 0.511 and 1.566, compared to RF's MAE values of 0.719 and 1.644, respectively, in a 30-day lead time. The models' performance decreased with increasing lead time, as per the study findings. In summary, preprocessing original data and utilizing machine learning models with decomposed techniques have shown promising results for water level forecasting in higher lead times. It is expected that the approach of this study can assist water management authorities in taking precautionary measures based on forecasted water levels, which is crucial for sustainable water resource utilization.

• 한국습지학회지
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• 제18권3호
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• pp.275-281
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• 2016

본 연구는 수질 및 수생태계 보전에 관한 법 53조2항에 해당하는 고속도로에서의 효과적인 비점오염관리를 위해 자동차 운행대수에 따른 고속도로의 강우유출 특성을 분석하여 비점오염 저감시설 설치 방안을 제공하고자 수행하였다. 연구대상지점은 총 5지점으로 경부, 서해안, 호남 및 통영대전 고속도로로 지점에 따라 2006~2008년과 2015년에 총 44회의 강우사상을 대상으로 모니터링을 수행하였다. 모니터링 결과, 평균 선행건기일수(ADD)는 6.2일, 평균 강우량은 19.2 mm로 조사되었다. 단위면적당 일평균 차량 통행량(ADT/CA)의 경우 경부고속도로 지점인 H-4에서 49.4대/$day{\cdot}m^2$으로 가장 높았으며 다른 지점의 경우 10대/$day{\cdot}m^2$미만으로 조사되었다. 조사대상 지점에서 발생되는 비점오염물질의 농도는 평균적으로 TSS는 63.5 mg/L, BOD는 24.9 mg/L, TN은 3.35 mg/L, TP는 0.63 mg/L, Total Zn은 298 ug/L로 국내에서 발표된 고속도로 관련 강우유출수 EMC 값보다 비교적 낮게 조사되었다. 한편, 조사대상지점의 오염물질 농도와 ADT/CA간의 상관관계 분석결과, SS에서 $R^2$값이 0.585로 가장 높은 상관성을 나타냈다. ADT/CA와 TSS EMC 와의 상관관계식을 통하여 국내 고속도로 평균 TSS EMC가 73.7 mg/L일 때 ADT/CA는 13 대/일${\cdot}m^2$으로 이를 기준으로 단위면적당 차량의 통행량이 13대보다 높을 경우 입자상 물질의 발생량이 높은 지역으로 고려, 비점오염관리가 필요한 지역으로 제시할 수 있으며 본 연구에서는 선행연구에서 제시된 ADT에 단위면적을 고려하였기에 기존에 수행되었던 연구보다 일반화된 단위로 활용도 및 적용성이 높을 것으로 판단된다.

• 한국물환경학회지
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• 제26권5호
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• pp.841-849
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• 2010

Soil erosion is an natural phenomenon. However accelerated soil erosion has caused many environmental problems. To reduce soil loss from a watershed, many management practices have been proposed worldwide. To develop proper and efficient soil erosion best management practices, soil erosion rates should be estimated spatially and temporarily. The Universal Soil Loss Equation (USLE) and USLE-based soil erosion and sediment modelling systems have been developed and tested in many countries. The Sediment Assessment Tool for Effective Erosion Control (SATEEC) system has been developed and enhanced to provide ease-of-use interface to the USLE users. However many researchers and decision makers have requested to enhance the SATEEC system for simulation of soil erosion and sediment reflecting effects of single storm event. Thus, the SATEEC R factors were estimated based on 5 day antecedent rainfall data. The SATEEC 2.1 daily R factor was applied to the study watershed and it was found that the R2 and EI values (0.776 and 0.776 for calibration and 0.927 and 0.911 for validation) with the daily R were greater than those (0.721 and 0.720 for calibration and 0.906 and 0.881 for validation) with monthly R, which was available in the SATEEC 2.0 system. As shown in this study, the SATEEC with daily R can be used to estimate soil erosion and sediment yield at a watershed scale with higher accuracy. Thus the SATEEC with daily R can be efficiently used to develop site-specific soil erosion best management practices based on spatial and temporal analysis of soil erosion and sediment yield at a daily-time step, which was not possible with USLE-based soil erosion modeling system.

• 한국물환경학회지
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• 제23권6호
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• pp.897-905
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• 2007

Approximately 70% of Korea is composed of forest areas. Especially 48% of agricultural field is practiced at highland areas over 400 m in elevation in Kangwon province. Over 90% of highland agricultural farming is located at Kangwon province. Runoff characteristics at the mountainous area such as Kangwon province are largely affected by steep slopes, thus runoff estimation considering field slopes needs to be utilized for accurate estimation of direct runoff. Although many methods for runoff estimation are available, the Soil Conservation Service (SCS), now Natural Resource Conservation Service (NRCS), Curve Number (CN)-based method is used in this study. The CN values were obtained from many plot-years dataset obtained from mid-west areas of the United States, where most of the areas have less than 5% in slopes. Thus, the CN method is not suitable for accurate runoff estimation where significant areas are over 5% in slopes. Therefore, the CN values were adjusted based on the average slopes (25.8% at Doam-dam watershed) depending on the 5-day Antecedent Moisture Condition (AMC). In this study, the CN-based Long-Term Hydrologic Impact Assessment (L-THIA) direct runoff estimation model used and the Web-based Hydrograph Analysis Tool (WHAT) was used for direct runoff separation from the stream flow data. The $R^2$ value was 0.65 and the Nash-Sutcliffe coefficient value was 0.60 when no slope adjustment was made in CN method. However, the $R^2$ value was 0.69 and the Nash-Sutcliffe value was 0.69 with slope adjustment. As shown in this study, it is strongly recommended the slope adjustment in the CN direct runoff estimation should be made for accurate direct runoff prediction using the CN-based L-THIA model when applied to steep mountainous areas.

• 한국수자원학회논문집
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• 제40권7호
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• pp.533-543
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• 2007

본 연구에서는 조선왕조실록의 문헌 기록 호우사상의 특성을 파악하고 정성적으로 평가하였다. 먼저, 조선왕조실록의 문헌기록에 대한 사상은 '큰비', '큰물', '홍수', '폭우'의 네 가지 키워드를 이용하여 추출하였다. '큰비'가 포함된 사상의 경우, 피해상황이나 규모 등이 자세하게 기록되지 않은 경우가 많았지만 '큰물', '홍수', '폭우'의 경우, 그 피해 정도나 규모가 상세하게 기록되어 있었다. 즉, '큰비'의 경우는 비의 절대량만으로 판단하여 기록된 것이고 '큰물', '홍수', '폭우'의 경우는 비의 절대량보다는 유출에 의해 피해가 비교적 컸던 경우 기록된 것으로 판단된다. 간단한 유효 우량 산정방법인 SCS방법을 적용하여 유효우량을 살펴본 결과에서는 대체로 '큰비'의 경우는 선행 5일 강수량의 크기가 작아 AMC-I 조건인 경우가 많았고 반대로 '큰물', '홍수', '폭우'의 경우는 선행 5일 강수량이 상당히 커 AMC-III 조건이 대부분 이었다. 이에 따라 강수량 대비 유효우량은 '큰물', '홍수', '폭우'의 경우가 '큰비'에 비해 훨씬 크게 나타났음을 확인할 수 있었다. 따라서 피해기록이 자세하게 기록되어 있는 경우는 유출로 인한 피해가 큰 경우라 할 수 있으며 '큰물', '홍수', '폭우' 문구가 포함된 기록들이 이에 해당한다고 할 수 있다.

• Clinical and Experimental Pediatrics
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• 제53권4호
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• pp.503-509
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• 2010

목 적: 신생아 폐출혈은 드물긴 하나, 일단 발생한 환아는 높은 사망률을 보인다. 급성 좌심실 부전, 호흡 곤란 증후군, 동맥관 개존증, 패혈증, 혈소판 감소증 등이 폐출혈 발생에 영향을 미칠 수 있다고 보고되고 있다. 저자는 출생 체중에 따라 신생아의 폐출혈 발생에 영향을 줄 수 있는 위험 인자를 규명하고 예후를 알아보고자 하였다. 방 법: 1995년 1월부터 2008년 12월까지 본원 신생아 중환자실에 입원한 재태 기간 37주 미만의 미숙아 117명을 대상으로 출생 체중에 따라 두 군으로 구분하였다. 폐출혈의 정의는 임상적인 정의를 적용하였고, 각 군에서 폐출혈의 발생에 영향을 미치는 요인을 알고자 병력지를 기초로 후향적으로 조사하였다. 결 과: 대상 환아 총 117례 중 폐출혈은 39례(33.3%)에서 발생하였으며, 출생 체중에 따라 극소 저체중 출생아군에서는 대상환아 총 48례 중 17례(35.4%)에서 폐출혈이 있었고 산전 산모의 스테로이드 치료 여부는 환아의 폐출혈 발생과 유의한 관련이 있었다($P$=0.001). 1분 APGAR 점수가 3점 이하인 경우, 혈소판 감소증도 폐출혈 발생과 유의한 관련이 있었다($P$<0.05). 저체중 출생아군에서는 대상 환아 총 69례 중 22례(31.9%)에서 폐출혈이 있었고 1분 APGAR 점수가 3점 이하인 경우는 폐출혈 발생과 유의한 관련이 있었다($P$=0.025). 저혈압, 산혈증, 혈소판 감소증도 폐출혈 발생과 유의한 관련이 있었다($P$<0.05). 다변수 분석에서 극소 저체중 출생아군에서는 산전의 산모 스테로이드 치료가 환아의 폐출혈 발생을 의미있게 감소시켰으며(OR=0.203, 95% CI=0.044-0.934), 저체중 출생아군에서는 1분 APGAR 점수가 3점 이하인 경우(OR=5.992, 95% CI=1.145-31.351)와 산혈증(OR=4.434, 95% CI=1.279-15.376)이 환아의 폐출혈 발생과 유의한 관련이 있었다. 결 론: 출생 체중이 적은 군에서 비교적 폐출혈이 늦게 발생하나, 일단 발생하면 사망률은 더 높은 것으로 나타났다. 극소 저체중 출생아군에서는 산전의 산모 스테로이드 치료가 환아의 폐출혈 발생을 의미있게 감소시켰으며, 저체중 출생아군에서는 1분 APGAR 점수가 3점 이하인 경우와 산혈증이 환아의 폐출혈 발생과 유의한 관련이 있었다.