The Colorado front-range and metropolitan areas are not immune to floods. Flood intensity is gauged by using terminology such as the 100-year storm event or the 50-year storm event. A 100-year storm event is one that has a 1/100th chance (1% chance) of occurring in any one year. A 10-year storm event has 1/10th chance (10% chance) of occurring in any one year.
Below are some examples of storm events and their measured occurrence:
- Between September 9 and 14, 2013, the Denver Metro area including Arvada experienced between 7 an 16 inches of rain over five consecutive days, gauged as a 1,000 year storm event.
- On July 28, 1997, a flood hit Fort Collins, leaving a path of destruction. - this flood was gauged as over a 500-year storm event.
- In June of 1989, merchants at Arvada Plaza on Ralston Road were flooded. - this flood was gauged as a 50-year storm event.
- In 1976, a flood destroyed much of the Big Thompson River valley - this flood was gauged as a 1,000-year storm event.
Arvada has the following FEMA-identified 100-year floodplains: Big Dry Creek, Little Dry Creek, Leyden Creek, Ralston Creek, Van Bibber Creek and Clear Creek. Even if a property is outside of these floodplains, flooding can still be possible from a localized drainage source, or a storm larger than the 100-year event.
The City of Arvada, Jefferson County, the Urban Drainage and Flood Control District, and the National Weather Service have developed a flood warning plan for Ralston Creek, Leyden Creek, and Van Bibber Creek. Rain gauges along these creeks give officials the ability to continually monitor storm and flood conditions. Warnings and other information are disseminated by radio, television, and police and fire departments.
Each spring and after major rainfalls, the City inspects all of Arvada's creeks and drainageways. Any accumulated debris is removed to keep the channels clear. If you see debris or other problems in the creeks, drainageways, inlets or storm sewer please contact the City Streets Division at (720) 898-7720. Maintenance of irrigation ditches is the responsibility of the ditch owners.