Forest fires, to which the arid west is vulnerable, are terrible in themselves.
The Missionary Ridge fire (pictured left) occurred in 2002 near Durango. Not as well understood is that danger and damage often continue after the flames are out. When a forest fire occurs in the mountains, most people do not automatically think, “call a geologist,” but it’s not really such a bad idea. Forest fires remove stabilizing vegetation and when combined with the right (or wrong) geology, commonly set up conditions that lead to major flooding and debris flows during subsequent heavy rains.
Flooding following a fire in the Front Range southeast of Denver resulted in tremendous problems with silt deposited in the Strontia Springs Reservoir on the South Platte River. Millions of dollars were spent repairing the damage to this reservoir, and scientists estimate that 463,000 cubic yards of material were deposited in the reservoir in the two-and-a-half years after the fire. This represents only a fraction of the total soil eroded from the fire area. After a large fire, CGS geologists quickly notify local jurisdictions of those areas that are most susceptible to debris flows.