These results were verified by comparing one year’s sediment yield observation on the outlet of the watershed. Other land, soil eroded from upland were deposited in lowland. Upland area was designated as having a severe to extreme severe erosion hazard compared to lowland which was designated as having very less to moderate. Annual average soil loss for Sumani watershed was 76.70 Mg ha-1 y-1 in 2011. Sumani Watershed had erosion hazard in criteria as: severe to extreme severe (26.23%), moderate (24.59%) and very low to low (49.18%). Calculating soil loss and map of USLE factor were determined by Kriging method in Surfer 9. Landsat TM imagery and field survey were used to determine crop management (C-factor) and conservation practices (P-factor). Of Sumani Watershed was used to calculate slope length and Steepness (LS-factor). As many as101 sampling sites were used to investigate soil erodibility (K-factor) with physico-chemical laboratory analysis. Climatology data from three stations were used to calculate Rainfall erosivity (R) factor. West Sumatra, Indonesia using data soil survey and monitoring sediment yield in outlet watershed. The Universal Soil Loss Equation (USLE) and Erosion Three Dimension (E3D) in Surfer were used to identify characteristic of dominant erosion factors in Sumani Watershed in Quantitative evaluation of soil erosion rate is an important basic to investigate and improve land use system, which has not been sufficiently conducted in Indonesia.
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