Journal of Wetlands Research (한국습지학회지)

Korean Wetlands Society (한국습지학회)
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Study on improvement of USLE P factor considering topography and cultivation method

지형 및 경작 방법을 반영한 범용토양유실량 산정공식 보전관리 인자 개선 연구

  • Sung, Yunsoo (Ministry of Environment Wonju Regional Environment Office, Total maximum daily load management division) ;
  • Lee, Gwanjae (Dept of Regional Infrastructure Engg, Kangwon National University) ;
  • Lee, Gwanjae (Dept of Regional Infrastructure Engg, Kangwon National University) ;
  • Han, Jeongho (Dept of Regional Infrastructure Engg, Kangwon National University) ;
  • Kim, Jonggun (Dept of Regional Infrastructure Engg, Kangwon National University) ;
  • Lim, Kyoung Jae (Dept of Regional Infrastructure Engg, Kangwon National University) ;
  • Kim, Ki Sung (Dept of Regional Infrastructure Engg, Kangwon National University)
  • 성윤수 (원주지방환경청 수질총량관리과) ;
  • 이관재 (강원대학교 지역건설공학과) ;
  • 이동준 (강원대학교 지역건설공학과) ;
  • 한정호 (강원대학교 지역건설공학과) ;
  • 김종건 (강원대학교 지역건설공학과) ;
  • 임경재 (강원대학교 지역건설공학과) ;
  • 김기성 (강원대학교 지역건설공학과)
  • Received : 2018.10.15
  • Accepted : 2019.04.12
  • Published : 2019.05.31
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Abstract

The USLE P factor is a factor that varies depending on how croplands are managed and cultivated. Previous studies tend to overestimate the amount of soil loss because the factor was estimated from the slope of the watershed rather than the estimate of each cultivated land. In addition, the accuracy of estimating the soil loss is decreasing due to the fact that the factor is calculated without considering various conditions of cultivated land defined by Wishmeier and Smith. In order to overcome these problems, the Ministry of Environment (MOE) has proposed to establish the topsoil notification and calculate the P factor according to the cultivation methods (e.g., tillage system, support practice). However, it is required to apply the conditions proposed in the United States to domestic circumstances as it is causing uncertainties. Thus, this study selected the watersheds where soil loss was serious (Haean, Jaun, Banbyeoncheon), measured the actual slopes and slope lengths, and examined the crop, tillage systems, and support practice for each cultivated land. The P factors were recalculated considering the actual conditions of cultivated land and compared to the factors proposed by the previous studies (MOE). As the result of the study, the P factors calculated based on the previous studies were 0.8 ~ 1.0 in three watersheds. On the other hand, it is confirmed that there is a significant difference between the factors notified by MOE and estimated by reflecting the topography and cultivation methods in this study. Therefore, it is considered that the research for developing the cultivation conditions to calculate the P factor suitable for the domestic environment should be continuously carried out.

본 연구는 토양유실량 산정을 위해 사용되는 USLE P factor 선정의 문제점 확인 및 개선방향 제시에 대한 연구이다. USLE P factor는 경작지를 어떻게 관리하여 사용하느냐에 따라 그 값이 달라지는 계수이다. 하지만 기존 연구들은 경작지 상황에 따른 선정이 아닌 유역의 경사도에 대한 P factor를 선정함에 따라 토양유실량이 과다 산정되는 경향이 있다. 뿐만 아니라 처음에 이 식은 제안한 Wishmeier와 Smith에 의해 정의된 다양한 조건들에 부합되지 않게 인자를 선정하고 있어 토양유실량 산정에 대한 정확성이 떨어지고 있다. 이에 환경부에서는 이러한 문제점을 해결하기 위해 표토관련고시를 제정하고 이에 따른 P factor를 선정하도록 제안하고 있다. 하지만 미국에서 제안된 조건을 그대로 국내 사정에 적용하도록 되어 있어 많은 문제점을 야기하고 있다. 이에 본 연구에서는 실제 토양유실이 심각하게 이루어지고 있는 유역(양구 해안면 유역, 홍천 내면 자운리 유역, 안동 임하면 반변천 상류유역)을 선정하여 경사장과 경사도를 측정하고 각 필지에 적용된 관리방법과 경운방법을 조사하여 각 조건들에 적용한 후 고시에 의거하여 제시된 조건을 통해 선정된 인자와의 비교를 통해 고시의 문제점을 확인하였고, 문헌연구를 통한 새로운 조건에 대입하여 새로운 인자들을 선정하였다. 연구 결과, 환경부에서 제시한 표토관련고시에 의거하여 선정된 P factor의 경우 대상 유역 3곳에서 0.8~1.0사이의 값을 제시하고 있었다. 하지만 처음 제안된 조건들을 대입하여 P factor를 선정해본 결과 각 경사도 및 경사장 조건에 부합하여 선정된 값은 고시를 통해 선정된 값과는 차이가 있음을 확인하였다. 이를 통해 국내 환경에 적합한 P factor를 선정하기 위한 조건을 개발하기 위한 연구가 지속적으로 이루어져야 한다고 판단된다.

Keywords

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Fig. 1. Study areas

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Fig. 2. Agriculture land in the study areas

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Fig. 3. Comparisons of measured and Google Earth based slopes for selected feilds

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Fig. 8. Results of farming survey(crop, Tillage system, and Support practice) for three study areas

Table 1. P factors of conservation practice in Korea (Jung, 2004)

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Table 2. Modified USLE P factor according to management plan in Haean

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Table 3. Modified USLE P factor according to management plan in Jaun-ri

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Table 4. Modified USLE P factor according to management plan in Jaun-ri

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