Fuel Break Vegetation Monitoring with Sentinel-2 NDVI Robust to Phenology and Environmental Conditions

Wildfires are recurrent natural disasters in some regions of the globe, being Portugal one of these areas. The Portuguese Institute for Nature Conservation and Forests implemented a national fuel break (FB) network, with the goal of decreasing fire hazard. FBs are areas of reduced fuel load that slow down fire spread, creating firefighting opportunities. Its effectiveness relies on periodic treatments to maintain the fuel load in levels that can reduce the effects of wildfires. This paper proposes a methodology to assess the FB state, according to its fuel load, based on the analysis of the inter-annual variability of Sentinel-2 NDVI time series. Inter-annual comparison allows it to adapt to different regions. To assess the reliability of NDVI data to evaluate the FB state, a linear regression with the vegetation height acquired by the Global Ecosystem Dynamics Investigation (GEDI) mission was tested, achieving determination coefficients between 0.57 and 0.98.