Fire risk mapping by integration of dynamic and structural variables

摘要

A methodology for fire risk mapping using satellite imagery and ancillary data, developed within PREMFIRE, a project funded by European Space Agency (ESA), is presented. The proposed methodology is based on the combination of both structural and dynamic indices to produce an Integrated Forest Fire Risk map, to be updated daily. The structural component is based on the combination of geographical variables that do not change in a short lapse of time or that are human-related, such as vegetation cover (fuel types), topography, and distance to roads and urban areas. Therefore, to be realistic, this index needs to be updated only at the beginning of the fire season. The dynamic fire risk index aims at detecting slight and constant variations in the flammability of forest fuels during the fire season and hence makes use of variables that, however changing in a short lapse of time, can still be measured. The approach combines a fuel model map, a maximum live ratio map, a relative greenness map and a 10-hour timelag dead fuel moisture map. The integration of both structural and dynamic indices was achieved by creating a fire risk table, where specific risk values were assigned to all possible combinations, resulting in values ranging from 1 to 3, where 1 means low risk, 2 medium risk, and 3 very high risk. Final results on the validation of the integrated risk model for a study area in central Portugal and for the 2001 fire season are also presented. The results obtained show that the model developed, designated as Integrated Forest Fire Risk (IFFR), identifies well those areas at risk. The model explains adequately fire occurrence, since high-risk value situations have shown an excellent relation with burnt areas.