How would you estimate ROS if you only have wind speed and slope, with no other data?

• A. Ignore wind and slope and assume a constant ROS.
• B. Use a detailed numerical model.
• C. Apply a simplified rule-of-thumb or baseline ROS for the fuel model and adjust with WAF and SF.
• D. Estimate ROS from fuel moisture alone.

Answer: (C)

When you only know wind speed and slope, the practical way to estimate ROS is to use a simple rule-of-thumb: take the baseline ROS for the fuel model you’re dealing with and then adjust it with a Wind Adjustment Factor and a Slope Factor. The baseline ROS represents how fast the fire would spread in flat, still air for that fuel type. The Wind Adjustment Factor captures how wind speeds increase spread, while the Slope Factor accounts for how uphill or downhill terrain changes flame contact and convection, usually increasing ROS on upslope. By multiplying the baseline ROS by these two adjustment factors, you get a reasonable estimate of ROS with the limited data you have. This approach is preferable to ignoring wind and slope, and it’s more practical than a detailed numerical model that requires many more inputs. It also avoids trying to estimate ROS from fuel moisture alone when wind and slope are the main known drivers in this scenario.