Abstract:The hazard assessment on potential post-earthquake debris flows is an important task and technical basis for disaster prediction and prevention,while related research is limited.Wenchuan was taken as a typical study area.Through data collection,field investigation and remote sensing monitoring,the frequency,the flow quantity and the geomorphic information entropy of post-earthquake debris flow were selected as three key indicators for hazard assessment.Correspondingly,the discharge calculation method of post-earthquake debris flow was improved,the DNWT model was established for dynamic monitoring and quick extraction of the sources of post-earthquake debris flow,and the evaluation index systemfor debris flow hazard was set up.By means of the GIS and the grey system method,the model for evaluating the hazard of post-earthquake debris flows was established,sub-catchments were extracted and selected as hazard assessment units,and the hazard assessment on potential post-earthquake debris flows in the investigated area was conducted.The results show that:1) the proposed DNWT model for extracting debris flow sources can realize the remote sensing identification,dynamic monitoring and automatic extraction of post-earthquake debris flow sources including rockfalls,landslides and their loose accumulations;2) by combining the field investigation with debris-flow discharge calculation data,the discharge calculation formula of debris flow is corrected.The blocking factor of post-earthquake debris flow can increase 1.72-3.46 times,compare with the case before the earthquake,and its discharge increases exponentially;3) based on sub-catchments,geomorphic information entropy is introduced,and meanwhile,it simplifies parameters and procedures for hazard assessment on post-earthquake debris flows and can evaluate the development stage of landforms and the hazard degree of each catchment;4) most of the debris flows in the studied area are in the moderate,high and very high hazard zones and have great potential risks.Among them,there are 89 debris flows in high and very high hazard zones,which are distributed along the main stream of Minjiang River and the valley of Yuzi River,and these areas are crucial for debris flow prevention and mitigation.The research results are consistent with the actual situation and can provide a basis and reference for remote sensing dynamic monitoring,quantitative risk assessment and prevention and mitigation of potential post-earthquake debris flows.