Slope effect on pine needle fire spread suppression in firebreaks

The increasing frequency of forest and grassland fires poses significant threats to human safety, property, and ecological stability. Accurately predicting fire spread is crucial for effective fire prevention and control. Traditional methods, such as mechanical tillage, controlled burning, and biological firebreaks, have limitations in terms of efficiency and implementation speed. In contrast, firebreaks established using fire retardants offer numerous advantages, including high effectiveness, minimal disruption to vegetation, and rapid deployment, thus facilitating effective emergency responses. However, the nonlinear behavior of fire spread, influenced by various factors such as topography and fuel characteristics, complicates its analysis and prediction. This study focuses on integrating new fire retardants into efficient firebreaks to enable precise fire management and rapid emergency response. The study investigates the propagation characteristics of pine needle fires on varying slopes and evaluates the effectiveness of firebreaks, aiming to provide scientific insights for developing fire prevention strategies in complex terrains.

Herein, we utilized version 6.8 of the Wildland Fire Dynamics Simulator, developed by the National Institute of Standards and Technology. This simulation tool integrates extensive empirical physical parameters, enabling comprehensive analysis of the slope impact on fire spread. Practical tests were conducted to assess the combustion characteristics of pine needles, with key parameters such as flame propagation speed, heat release rate, and combustion temperature distribution being simulated under various slope conditions (0°, 30°, 45°, and 60°). Additionally, a 10-cm-wide firebreak was introduced to examine the influence of slope on fire behavior and evaluate the effectiveness of this fire control measure at different slopes. This methodology provides a solid scientific foundation for understanding fire spread mechanisms and developing effective countermeasures.

The findings indicate a pronounced impact of slope on fire dynamics, with measurable variations in flame propagation velocity, heat release rate, and combustion duration. Specifically, as the slope was increased from 0° to 60°, the flame propagation velocity rose significantly, leading to a decrease in combustion duration and an increase in heat release rates. At a 30° slope, the 10-cm fire retardant barrier effectively curtailed flame spread, demonstrating a marked reduction in heat flux. However, at steeper slopes of 45° and 60°, the buoyancy effects intensified, resulting in a heightened risk of igniting vegetation located behind the involved barrier. This was evident as the maximum heat flux at a 60° slope reached 39.78 kW/m², surpassing the critical threshold necessary for igniting downwind vegetation. These results underscore the importance of considering slope in fire management strategies, particularly in areas where fire behavior can escalate rapidly. The predictive model developed also highlights the significant relationship between slope, vegetation properties, and fire spread rates, providing a scientific framework for improving fire prevention and control measures in diverse terrains.

The study concludes that slope, firebreak width, and fire retardant application conditions significantly affect fire behavior. Moreover, it highlights the importance of optimizing firebreak designs, particularly in areas with steep slopes. Future research should focus on widening firebreaks and improving the concentration and distribution of fire retardants to maximize fire prevention effectiveness. Overall, this study provides a robust foundation for developing effective fire management strategies that consider the complex interactions among topography, vegetation, and fire dynamics.