Colorado, and especially Boulder, Colo., has a history of flash floods. In 2004, the University of Colorado's Natural Hazards Center listed a flash flood in Boulder as one of six "disasters waiting to happen" in the United States.
(AP Photo/Earth Vision Trust, Matthew Kennedy)
The torrential rains and walls of water that rushed through stream channels caught many Coloradoans by surprise this week, but disaster scenarios have long foretold the fatal flash floods that tore through Colorado's foothills.
"We knew this kind of rain was possible," said Matt Klesch, a hydrometeorologist at the University Corporation for Academic Research (UCAR), based in Boulder, Colo. This week, Boulder set a record for its wettest 24-hour period, with 7.21 inches (18.3 centimeters) of rain from 6 p.m. Wednesday (Sept. 11) to Thursday, and more than 12 inches (30 cm) in total from Monday to Friday.
In 2004, the University of Colorado's Natural Hazards Center listed a flash flood in Boulder as one of six "disasters waiting to happen" in the United States. But scientists and emergency officials have been preparing for this week's flooding since 1976, when a flash flood killed 145 people in Boulder's Big Thompson Canyon. [Colorado Flood Photos: 100-Year Storm]
"Prior to that, we weren't really prepared," Klesch told LiveScience. "Big Thompson Canyon was a wake-up moment."
Preparing for the flood
After the 1976 flood, the city of Boulder bought up undeveloped land along flood zones to prevent development, said Dennis Mileti, the director emeritus of the University's Natural Hazards Center. The city built bike paths to serve double-duty as floodwater channels, with breakaway fences so debris wouldn't jam.