Implications of canyon fire behavior under different fuel conditions for fire risk assessment

Canyon fire spread often involves sudden acceleration associated with eruptive fire. However, the critical condition of eruptive fire, and the effectiveness of forest management in reducing fire risks in such complex terrains, remain unclear. This study conducted systematic canyon fire experiments using two fuel types and different fuel loads to investigate their influence on canyon fire behavior and eruptive fire, and to discuss their implications for fire risk assessment. The results indicate that fuel conditions influence fire behavior due to varying physicochemical properties and fuel bed structures. Fire line evolution of Korean pine and Mongolian oak canyon fires exhibited distinct differences only under low-slope configurations (α ≤ 20°). The influence of fuel type on the rate of spread (ROS) is associated with the occurrence of eruptive fire. Fuel load did not noticeably alter the fire line evolution pattern, whereas ROS increased with increasing load. Notably, the observed critical conditions (α = 27.5°, δ = 20°) for the occurrence of eruptive fire remained unchanged across the tested conditions, indicating that topography exerted the dominant control. When the slope meets the critical conditions, the ROS increases sharply within a short period. Consequently, topographic analysis should be prioritized in the formulation of forest management strategies and fire danger assessments, with hazardous canyon areas designated as key monitoring zones. The findings provide a critical scientific basis for future wildfire management strategies and on-site decision-making by fire risk managers, contributing to more effective wildfire management.