Normalized Burn Ratio (NBR)

Example map showing differenced NBR (dNBR) in northern British Columbia following a fire in the summer of 2023.

Description

The Normalized Burn Ratio (NBR) is used to map burned areas and to characterize fire severity. It is calculated as the normalized difference ratio in reflectance between the near-infrared (~0.76-0.9 µm) and shortwave infrared (~2.08-2.35 µm) portions of the electromagnetic spectrum, typically measured by satellite or other aerial platforms (Roy et al, 2006). Values of NBR are bounded between -1 and 1, with values close to 1 indicating healthy/productive vegetation and values near or below 0 often being burned or unproductive vegetation.

NBR is calculated as the normalized difference ratio between near infrared and shortwave infrared reflectance

The image below compares a typical spectral signature for healthy/productive vegetation and burned areas.

A comparison between a typical spectral signature for healthy/productive vegetation and burned areas. Source: US Forest Service

The differenced (or delta) Normalized Burn Ratio (dNBR) is commonly used to assess fire severity and maps of dNBR can be created by subtracting post-fire NBR from pre-fire NBR. Interpretation of both NBR and dNBR maps will depend on the vegetation community present before the fire. For example, grasslands and shrublands will often have lower NBR and dNBR than forests, even after impactful fires, because of differences in vegetation density and the influence of bare soil on values (Miller & Thode, 2007).

See a demonstration of using the NBR and dNBR in Climate Engine in the video below

References

Miller, J. D., & Thode, A. E. (2007). Quantifying burn severity in a heterogeneous landscape with a relative version of the delta Normalized Burn Ratio (dNBR). Remote sensing of Environment, 109(1), 66-80.
Roy, D. P., Boschetti, L., & Trigg, S. N. (2006). Remote sensing of fire severity: assessing the performance of the normalized burn ratio. IEEE Geoscience and remote sensing letters, 3(1), 112-116.