The canyon country of Colorado can be very beautiful, but it can turn deadly in a very short time. There are many hazards that a visitor can encounter in this wonderful country. Among them are rattle snakes, scorpions, mountain lion, exposed crumbling cliffs, extreme heat and cold and believe it or not rain.
The beautiful sandstone cliffs and spires that comprise a large portion of Western Colorado actually contribute to one hazard that a lot of people don’t think about. Flash Floods. The majority of Western Colorado consists of a layer of rock, mostly sandstone with a thin layer of soil on the surface. This thin layer of soil makes it especially easy for a small amount of rain to wash it away leaving the rock below exposed and creating a convenient channel for water to pass.
Flash floods can happen in a very short time and become deadly in an instant. Most flash floods are caused by slow moving thunderstorms, but they can also occur from dam breaks, ice dams coming apart or debris breaking loose.
A common mistake people make when they are out in the mountains is not paying attention to what is happening in the distance. Even though the sun could be shining overhead, up the valley could be getting rain and if the environment is right that rain water can find it’s way down the canyon very quickly.
Things to keep in mind when your out is, first, if there is a chance of a thunderstorm you should postpone your outing until the weather can cooperate. Second, pay attention of the geologic features of the area your in. You want to be especially careful in narrow canyons or normally dry washes. If you cross a canyon or wash, remember that it could become full of water in an instant trapping you on the other side. Always have an escape route. A very small amount of fast moving water can knock a person off of their feet. The power of flash floods can move boulders, knock down trees and sweep cars away. If you are driving and the road becomes flooded, never attempt to drive through the water. Even if you know the road is suppose to be there it could be washed out under the water.
In the mountains and canyon country of Western Colorado heavy rains that cause flash flooding can also cause mudslides and landslides. A lot of the canyon rims are unstable to begin with and with the addition of water softening the ground could make them extra dangerous.
Some interesting facts:
On August 8, 1968, over 2 inches of rain fell on Colorado National Monument resulting in a 182 foot section of RimRock Drive getting washed out and closing the road for a year.
On September 7, 1978 a flood came through No Thoroughfare Canyon and the United States Geological Survey estimated the flow of water to be almost 9300 cubic feet per second which was more then twice the flow of the Colorado River.
Here are a few pictures of a mild flash flood that happened in No Thoroughfare Canyon on the Colorado National Monument on August 16, 2010. It only rained a little over .5 inches in about 10-15 minutes. My original plan was to hike the Old Gordon Trail but I turned around when the storm started moving in. I’m glad I did, otherwise I would have been stuck on the wrong side of the wash. It would have been a long cold evening.