The Rapid Damage Assessment (RDA) module of EFFIS was initially implemented in 2003 to map burned areas during the fire season, by analyzing MODIS daily images at 250 m spatial resolution. For the monitoring of burned areas during the summer, daily images from the MODIS instruments on board of TERRA and AQUA satellites are acquired and processed few hours after the acquisition. The EFFIS Rapid Damage Assessment provides the daily update of the perimeters of burnt areas in Europe for fires of about 30 ha or larger, twice every day. Since 2018, the use of Sentinel-2 imagery allows the detection of fires below the 30 ha threshold.
Since the year 2016, the RDA incorporates the mapping of active fires and burnt areas from the VIIRS Sensor, onboard the NASA/NOAA Suomi National Polar-orbiting Partnershp (SNPP), which allows the update of burnt areas maps one more time, every day.
MODIS Burnt Areas
This process involves the delineation of the extent of forest fire events based on the semi-automatic classification of MODIS satellite imagery using ancillary spatial datasets. Testing on the use of MODIS data for mapping burnt areas in Europe was performed between the years 2000 and 2002, and the first map of burnt areas using this imagery was obtained in 2003. Until then maps of fire perimeters (burnt areas) were obtained only at the end of the fire campaign, i.e. end of September/October. After 2003 the processing chain was further automated to process MODIS data in near-real time. Daily, two full image mosaics the European territory are processed in EFFIS to derive burnt area maps, every day.
Fires are mapped using a semi-automatic procedure. Fires are first mapped on the basis of an unsupervised procedure that uses a combination of band thresholds and ancillary information from the CORINE Land Cover, the active-fire detection product from MODIS and VIIRS, and the fire news application, which are described ahead. Fires that are mapped by the unsupervised procedure are visually verified and corrected through visual interpretation of the MODIS and Sentinel-2 images.
IMPORTANT NOTE - For any use of the EFFIS Burnt Area product the conditions listed below must be taken into consideration:
Although only a fraction of the total number of fires is mapped, the area burned by fires of this size represents about 75% to 80% of the total area burned in EU. Modelling historical fire data from the EFFIS European fire database, equations have been set up for the different countries, which make it possible to predict the total area burned with good accuracy; that is, the total burnt area in a country is obtained as a function of the area burned by fires larger than 30 ha.
In order to obtain the statistics of the burnt area by land cover type, the data from the CORINE Land Cover database are used. Therefore the mapped burned areas are overlaid to land cover maps, allowing an assessment of damage to be made that is harmonized for all the European Countries.
The burnt area mapping in the RDA is based on the identification of active large fires from the MODIS, the expansion of the burnt areas from these initial points on the basis of region-growing algorithms, and the refinement of the final perimeter of the fire through visual interpretation of the images. The process is aided by the systematic collection of fire news from a variety of media. An alternative to the current methodology is being developed. This method is based on abrupt post-fire vegetation change detected from MODIS daily time series. Once implemented, this method will allow for a better and less user-dependent classification of the burned areas.
VIIRS Burnt Areas
Data from the VIIRS VIIRS (Visible Infrared Imaging Radiomer Suite) on board the NASA/NOAA Suomi National Polar-orbiting Partnership (SNPP) are also used for the mapping of burnt areas in EFFIS. The perimeters of the fires derived from VIIRS are generated using algorithms that derive polygons on the basis of the active fires retrieved from this sensor. Accordingly, the fire perimeters are directly derived from the coordinates of active fires, which permits near-real time processing, even in light cloudy or smoke situations.
These fire perimeters are thus produced just after the pass of the satellite and the acquisition of the data, without the need to perform the classification of the satellite imagery. Since the procedure is automatic and based on delineating polygons, the fire perimeters may have sharper shapes than those produced from the classification of MODIS imagery (above section). For the spatial resolution of the fire perimeters, it must be noted that the nominal spatial resolution of VIIRS is 375 m.
VIIRS derived data on burnt areas are not yet used in EFFIS to compute burnt area statistics; they are only displayed in the EFFIS "current situation viewer."
Fire severity is estimated using the difference Normalized Burnt Ratio (dNBR), as proposed by Key and Benson (2005) and verified through correlation with field-estimated fire effects (Twele, 2004). The thresholds used for the fire severity classes in EFFIS are as follows:
|Fire Severity Class||Range of dNBR|
|Unburned/Very Low||< 0.1|
|Low||0.1 - 0.255|
|Moderate||0.256 - 0.41|
|High||0.42 - 0.66|
|Very High||> 0.66|
Key, C. H., & Benson, N. C. (2005). Landscape assessment: Remote sensing of severity, the Normalized Burn Ratio. In D. C. Lutes (Ed.), FIREMON: Fire Effects Monitoring and Inventory System, Ogden, UT: USDA Forest Service, Rocky Mountain Research Station, General Technical Report, RMRS-GTR-164-CD (pp. LA1−LA51).
Twele, A., 2004, Post-fire vegetation regeneration: The case studo of the Massif the l'Etoile Fire, JRC Technical Report EUR 21010, European Communities.