Geospatial technologies for estimating post-wildfire severity through satellite imagery and vegetation types: a case study of the Gangneung Wildfire, South Korea

Wildfires have caused natural environmental damage that has contributed to deforestation, consequently demonstrating a significant influence on atmospheric emissions. Wildfires occur frequently in South Korea, especially during the spring season. This study assessed post-wildfires areas in Gangneung, South Korea, on April 11, 2023, which were generated by implementing remote sensing technology and statistical analysis. Remote sensing and classification techniques, including PlanetScope, have been developed for identifying wildfire-damaged areas. The method for classifying post-wildfire mapping estimation includes the utilization of deep learning approaches, especially using the U-Net architecture. Therefore, the assessment of wildfire severity can be conducted using Sentinel-2 and Sentinel-5P imagery in addition to an analysis of the vegetation type and air pollutant within the affected region. In the present study, Sentinel-2 imagery was to generate spectral indices, including the differenced normalized burn ratio (dNBR), differenced normalized difference moisture index (dNDMI), differenced soil adjusted vegetation index (dSAVI), and differenced normalized vegetation index (dNDVI). Sentinel-5P imagery was utilized to produce carbon monoxide (CO) column number densities. The estimation of wildfire areas was conducted using a PlanetScope classified image with the U-Net classifier, which was evaluated based on the overall accuracy value of 95% and kappa accuracy of 0.901. The wildfire severity level was shown by dNBR, which was correlated with the parameters, including RBR, dNDMI, dSAVI, dNDVI, and CO. The statistical analysis demonstrated a significant and positive correlation between the wildfire severity and the parameters. Moreover, the average of vegetation indices (NDMI, SAVI, and NDVI) before and after a wildfire were found to decrease by vegetation type, including 17.55% in mixed barren land areas, 17.49% in other grasses, 24.71% in mixed forest land, 22.48% in coniferous land, 13.48% in fields, and 4.29% in paddy fields. On the basis of the results, these estimates can be employed to identify the level of damage caused by wildfires to vegetation and air quality.