Normalized Burn Ratio Plus (NBR+): A New Index for Sentinel-2 Imagery

Abstract

The monitoring of burned areas can easily be performed using satellite multispectral images: several indices are available in the literature for highlighting the differences between healthy vegetation areas and burned areas, in consideration of their different signatures. However, these indices may have limitations determined, for example, by the presence of clouds or water bodies that produce false alarms. To avoid these inaccuracies and optimize the results, this work proposes a new index for detecting burned areas named Normalized Burn Ratio Plus (NBR+), based on the involvement of Sentinel-2 bands. The efficiency of this index is verified by comparing it with five other existing indices, all applied on an area with a surface of about 500 km2 and covering the north-eastern part of Sicily (Italy). To achieve this aim, both a uni-temporal approach (single date image) and a bi-temporal approach (two date images) are adopted. The maximum likelihood classifier (MLC) is applied to each resulting index map to define the threshold separating burned pixels from non-burned ones. To evaluate the efficiency of the indices, confusion matrices are constructed and compared with each other. The NBR+ shows excellent results, especially because it excludes a large part of the areas incorrectly classified as burned by other indices, despite being clouds or water bodies.

Geospatial assessment of vegetation condition pre-wildfire and post-wildfire on Luštica (Montenegro) using differenced Normalized Burn Ratio (dNBR) index

“…This kind of geospatial assessment using the dNBR index has been validated many times in different geographical conditions, and its high efficiency has been widely discussed in previous studies (Jovanović & Ţupan 2017;Potić et al, 2017;Llorens et al, 2021;Alcaras et al, 2022;Ponomarev et al, 2022). This study shows the possibility of assessing vegetation's condition pre-wildfire and post-wildfire based on Sentinel-2a satellite images in a QGIS environment using the dNBR index.…”

“…The application of Normalized Burn Ratio (NBR) and differenced Normalized Burn Ratio (dNBR) indices using satellite images has been the subject of many studies in various wildfire-affected landscape areas and is considered to be effective for identifying damage to burned areas (Roy et al, 2006;Miller & Thode, 2007;Keeley, 2009;Veraverbeke et al, 2010;Parker et al, 2015;Potić et al, 2016Potić et al, , 2017Potić et al, , 2019Jovanović & Ţupan 2017;Santos et al, 2020;Alcaras et al, 2022;Ponomarev et al, 2022).…”

Sentinel-2 data classification for land use land cover mapping in northern Algeria

“…The NBR+ index, which is a modified version of the Normalized Burn Ratio (NBR) index, was found to be more efficient than both the NBR and the Burned Area Index (BAI) in a study conducted by the authors in [15]. The NBR+ index was proposed to address some of the limitations of the NBR index, which is commonly used to assess fire severity and vegetation recovery following wildfires.…”

“…In contrast, the NBR+ index incorporates a correction factor that accounts for differences in topography and atmospheric conditions, making it more robust and accurate than the NBR index. The authors in [15] conducted a study comparing the performance of the NBR+, NBR, and BAI indices in assessing post-fire vegetation recovery, and found that the NBR+ index was more efficient and accurate than the other two indices. Therefore, based on the findings of this study, the NBR+ index may be a better choice for assessing fire severity and vegetation recovery following wildfires.…”

“…SWIR) / (NIR + SWIR) (B8 -B12) / (B8 + B12) [28] NBR+ (SWIR − NIR − GEEN − BLUE) / (SWIR + NIR + GEEN + BLUE) (B12 − B8A − B3 − B2) /(B12 + B8A + B3 + B2)[15] …”