Understanding Colorado Flooding

The Poudre River in Fort Collins drains more than 500 square miles of mountains and empties through a narrow canyon.

The Big Thompson River in Loveland drains more than 500 square miles of mountains and empties through a narrow canyon.

The St. Vrain River, Lefthand Creek and Boulder Creek drain more than 500 square miles of mountains and empty through narrow canyons.

Upslope winds force humid air from the plains up into the mountains. The air expands, cools and drops below its dew point. Rain falls and floods occur.

In 1976, the Big Thompson drainage received 14 inches of rain in four hours and produced one of America’s most deadly floods. This week’s rains have been nowhere near that intense.

In 1997, Spring Creek in Fort Collins received 10 inches of rain in four hours, and produced a flood with killed five people. Again, that rainfall was much more intense than this week.

In 1965, the South Platte River drainage received 15 inches of rain in 14 hours, and produced a flood with killed twenty-one people. Rainfall was much more intense than this week.

In 1921, a similar rain killed 1,200 people in Pueblo, Colorado.

People talking about biblical or 1,000 year rainfall have absolutely no idea what they are talking about. These floods can be expected somewhere along the Front Range every couple of decades.