Which statement about how slope influences ROS is correct?

• A. Slope effects are smaller on steep slopes
• B. Slope effects are larger on steep slopes
• C. Slope effects are irrelevant to ROS
• D. Slope effects are only relevant when wind is calm

Answer: (B)

Slope has a strong influence on how fast a fire spreads uphill because heat and flames preheat and ignite fuels ahead of the fire more effectively as the incline increases. On steeper slopes, the upslope preheating and radiant heat transfer are amplified, making fuels above the fire reach ignition sooner and the fire advance more quickly. That means the impact of slope on the rate of spread grows as the slope gets steeper, which is why the statement that slope effects are larger on steep slopes is the best choice. On gentle slopes or flat ground, the preheating effect exists but is much smaller, while the other options would imply either no impact or an impact that doesn’t increase with slope, which contradicts the observed behavior of uphill fire spread.