Efficient Soil Loss Assessment for Large Basins Using Smart Coded Polygons

Abstract

Soil erosion is a severe ecological problem. Most conventional methodologies for soil-erosion assessment are appropriate for small or medium river basins. This paper presents an approach to soil-erosion intensity assessment in large basins, utilizing coded polygons identified by spatially overlapping gradation levels of primary environmental factors. Efficient assessment of soil-erosion intensity is achieved by matching the coded polygons to selected polygons pre-assigned to reference groups. A case study is presented for the soil-erosion assessment of the Yellow River Basin. It is found that the calculated and observed soil-erosion intensities are in close agreement for 86% of the total area. Sensitivity analysis indicates that acceptable results are obtained using a 5% sample of the original 9,921 coded polygons, thus reducing substantially the computational load. Direct comparisons between the polygon codes in the reference and test groups show that uncertainty is reduced with respect to previous methods. This is confirmed by the reduction in information entropy from 7.49 to 1.33. The proposed approach should be of particular use in the cost-effective assessment of soil erosion in large basins.

Keywords: coded polygons, soil erosion assessment, Yellow River Basin, information classification, semi-quantitative model