The debris flow hazards following the Wenchuan earthquake were characterized by high frequency, large-scale and serious potential risks and debris flows have been the key restricting factor to restoration and reconstruction in Beichuan County. Developing degrees evaluation of debris flow is of great significance to the reconstruction. Taking Beichuan County as the study area and using ArcGIS technology and multi-factor superposition method, we evaluated the developing degrees of debris flows in Beichuan County following the Earthquake based on the field survey and remote sensing interpretation. Landslides density, formation lithology, seismic intensity, slope gradient, surface roughness and average annual precipitation were selected as evaluation factors and each of them was subdivided into five grades. Analytic Hierarchy Process (AHP) was used to determine the weights of factors and quantify each grade. On that basis, we constructed multi-factor weighted superposition evaluation model and evaluated the developing degrees of debris flow in the study area. According to the evaluation results, the study area was divided into three areas: high growth area, medium growth area and low growth area. The high growth area concentrated on the hanging wall of Beichuan-Yingxiu Fault and distributed along Leigu -Qushan -Chenjiaba townships, accounting for 6.6% of the study area; the medium growth area located on both sides of the high growth area and mainly on the hanging wall of Beichuan-Yingxiu Fault, accounting for 22.5% of the study area; the rest belonged to low growth area, accounting for 70.9% of the study area. We suggested that human activities should avoid debris flows in the high growth area and debris flow disaster evaluation should be conducted in the medium growth area to ensure no disaster threat, or must avoid debris flow, too.
