1. State Key Laboratory of Earth Surface Processes and Resource Ecology; Beijing Normal University; Beijing 100875 China
2. Academy of Disaster Reduction and Emergency Management; Ministry of Civil Affairs and Ministry of Education; Beijing 100875 China
3. Key Laboratory of Environmental Change and Natural Disaster, MOE; Beijing Normal University; Beijing 100875 China
4. School of Geographical Sciences; University of Bristol; Bristol BS8 1SS UK
5. Institute of Geographical Sciences and Natural Resources Research; Chinese Academy of Sciences; Beijing 100101 China