Those who live downslope of a wildfire area should be aware of this potential for slope failure that is present until new vegetation rebinds the soil. The flowing mud carries rocks, bushes, and other debris as it pours down the slopes. Speeds in excess of 20 mph are not uncommon, and speeds in excess of 100 mph, although rare, do occur locally. Sketch of a typical debris avalanche scar and track. Original drawing by Janet K. Smith.
Debris avalanches pose hazards that are often overlooked.
Houses in the path of debris avalanches can be severely damaged or demolished. Persons in these structures can be severely injured or killed. Most rainstorms are of such low intensity that they do not trigger debris avalanches. Some intense storms may trigger only a few debris avalanches. However, when the ground is already saturated from previous rain, even relatively short high-intensity rainstorms may trigger debris avalanches.