What is the purpose of using a baseline ROS in S-390?

• A. To define the maximum potential spread.
• B. To provide a reference point that is adjusted by WAF and SF to reflect wind and slope conditions.
• C. To compute flame length directly.
• D. To estimate fuel moisture.

Answer: (B)

The main idea is that baseline rate of spread serves as a neutral starting point for predicting how fast a fire will move. In the S-390 framework, this baseline represents the spread rate under reference conditions (neutral wind and slope, with standard fuel conditions). From there, real-world conditions are incorporated by applying adjustments for wind and slope. The wind adjustment factor increases or decreases the baseline spread depending on wind intensity and direction, while the slope factor accounts for how uphill or downhill terrain accelerates or slows spread. By combining these factors, you get a predicted ROS that reflects actual conditions without recomputing from scratch each time. This approach makes the model consistent and scalable across different fire scenarios. It isn’t about the maximum possible spread, computing flame length directly, or estimating fuel moisture, which require other inputs and methods.