BURN SEVERITY ASSESSMENT IN THE OKANOGAN-WENATCHEE FOREST USING NASA SATELLITE MISSIONS

ABSTRACT Fire severity is an increasingly critical issue for forest managers. A long history of fire suppression has led to millions of acres of dry western forests and a buildup of fuels. Satellite imagery offers a cost-effective and feasible tool for fire severity assessment and can provide near real-time data for mitigation measures. This study focused on the Tripod Complex Fire that burned more than 175,000 acres of the Okanogan-Wenatchee Forest in Washington in 2006. Field data were collected in order to calculate the Composite Burn Index (CBI), a ground-based measurement of burn severity which can directly correlate with satellite measurements. These in-situ data were used to calibrate the satellite data from the Landsat TM5 and the MODIS sensor on board the NASA Terra satellite. The satellite data were used to calculate the differenced Normalized Burn Ratio (dNBR) and the Relative dNBR (RdNBR). These algorithms use the relationship between the near infrared and the shortwave infrared to quantify burn severity. After comparing these two algorithms, it was determined that there was no significant difference between dNBR and RdNBR. Using the burn severity map created with the dNBR data, an analysis was performed to examine the relationship between burn severity and variables such as slope, aspect, and vegetation type. The relationships between several measures of burn severity are discussed