Sensitive evaluation and spatial analysis of soil and water loss based on USLE and GIS:Taking Taihang Mountain area of Hebei Province as an example

Located in the western part of Hebei province, the Taihang Mountain area is an important ecological protective screen for Beijing, Tianjin and North China Plain so that its ecological vulnerability and sensitivity attract great attention. In this region, topography, climate, drought, poor soils, sparse vegetation and irregular human activities will result in serious soil erosion. With the development of 3S technology in recent years, applying GIS to solve complex spatial problems in environmental fields has become one of the key researches for general geo- information technologic workers. Based on the USLE equation and analysis of factors influencing soil and water loss, the index of soil and water loss sensitivity evaluation was established in the Taihang Mountain area. The appraisal system included rainfall erosion, length-slope factor, vegetation cover, soil type and gully density, and each of the factors that influenced soil erosion sensitivity was calculated using the GIS method. As influencing factors play different roles in soil and water loss, we assigned different weights to them, which were converted to grid pattern and illuminated in thematic map. We calculated the soil and water loss sensitivity by overlaying weighted thematic maps and classified them into five classes: very low, low, moderate, high, and very high. Then, we used composite index SEPDI to describe the overall soil and water loss sensitivity in the research area and analyzed the spatial distribution of soil and water loss sensitivity under different geographical backgrounds. The results indicated that:(1) The value of SEPDI of the Taihang Mountain area of Hebei province amounted to 3.97, which meant soil and water loss sensitivity in this region presented a tendency from moderate to high;(2) From the perspective of sensitivity spatial distribution, soil erosion sensitivity presented obvious zonal distribution, and moderately sensitive area accounted for the largest proportion of 39.2%;(3) The spatial distribution of soil erosion sensitivity in different geographical backgrounds presented obvious difference. In various land use types, the unused land showed the highest soil erosion sensitivity while the forest and grassland were the lowest. Along with the slope increase, the soil erosion sensitivity of the whole region presented an increasing tendency. In different urban areas, soil erosion sensitivity of Zhangjiakou was the lowest while that of Baoding was the highest. Generally speaking, the sensitivity of each urban area was primarily at moderate level.