Water Repellent Soils and Their Relation to Wildfire Temperatures

A naturally occurring water resistant soil was exposed to different burning times and temperatures after which the soil samples were tested for non-wettability. The less intense treatments produced an extremely non-wettable condition. Temperatures of 800 and 900 degrees applied for 20 minutes completely destroyed the non-wettable property. Heat treatments within the realm of soil temperatures existing during wildfires were capable of producing the extreme non-wettable condition. The increased surface runoff and erosion from burned southern California watersheds could be the result of this relationship.