The formula de Parkland calculates wildfire spread rate based on wind speed, fuel moisture, and slope. It's a core tool in fire behavior prediction.
The formula estimates fire spread in feet per minute. It combines wind speed, fuel moisture, and slope to predict how quickly a fire will move. The original equation was developed by Australian researcher Alan S. McArthur in the 1960s and later refined by others, including Richard Parker, who contributed to its adaptation for different fuel types.
The formula is:
Rate of Spread (ROS) = 0.01 * (Wind Speed)^2 * Fuel Moisture Factor * Slope Factor
Where:
The formula adjusts for different fuel types, categorized by vegetation. Common types include:
| Fuel Type | Description |
|---|---|
| Grass | Dry grasslands, often found in plains |
| Brush | Dense shrubs and small trees |
| Timber | Mature forests with large trees |
Firefighters and forest managers use the formula de Parkland to predict fire behavior and plan suppression strategies. It's particularly useful in regions prone to wildfires, such as Australia, California, and the Mediterranean.
For example, during a wildfire in Southern California, firefighters might use the formula to determine how quickly the fire will spread toward nearby towns. By inputting wind speed, fuel moisture, and slope data, they can estimate the fire's rate of spread and allocate resources accordingly.
Many assume the formula accounts for all variables, but it doesn't include humidity or temperature directly. These factors influence fuel moisture, which is part of the equation but isn't measured independently.
Another mistake is applying the formula universally without adjusting for local conditions. Different regions have unique fuel types and weather patterns, requiring calibration for accurate predictions.
When I worked with a wildland fire module, we used the formula de Parkland to model fire spread during a controlled burn. We measured wind speed with an anemometer, estimated fuel moisture by examining local vegetation, and assessed slope using a topographic map. The formula helped us predict the fire's movement within a 10% margin of error, allowing us to set containment lines effectively.
For instance, if wind speeds were 15 mph, fuel moisture was low, and the slope was 20%, the formula might predict a spread rate of 50 feet per minute. This information guided our decision to position crews and equipment upstream of the fire's projected path.
While the formula de Parkland is a useful tool, it's not foolproof. Fire behavior is complex, and real-world conditions can introduce variability. However, when used alongside other models and on-the-ground observations, it provides valuable insights for firefighting efforts.