Flood Warning and Detection System

A flood forecasting system was implemented after the Big Thompson Flood in 1976. Rain gauges were placed in the drainages emptying into the city of Boulder and placed throughout the county west of Highway 36 and below 9000 feet. These gauges are monitored on a 24/7 basis to determine possible flooding.

Outdoor Warning System

Why use outdoor warning sirens?

Sirens are the most effective method to warn the population at large in the shortest amount of time. People may be outdoors in their yard, at outdoor events or anywhere else where they are not in contact with the news media channels such as radio, TV or local public address systems.

The siren system is an all hazard warning system used to alert citizens to potential danger. Twenty-eight outdoor warning systems are in place across Boulder County. The sirens are located in Boulder, Longmont, Louisville, Lafayette, Lyons, Eldorado Springs and the University of Colorado at Boulder. Some sirens have voice capability and the voice message will immediately follow the siren signal to inform the public of the situation and what actions should be taken.

During an actual emergency, the sirens will sound for five minutes. The same signal is used whether the emergency is flood, tornado or other disaster. The public should tune to a local TV or radio station for further information.

The outdoor warning sirens are sounded only in the event of an emergency or during pre-announced tests. Boulder’s sirens are toned from the Boulder Communications Center in the Public Safety Building. Louisville and Lafayette’s sirens can also be toned from the Boulder Communications Center. The siren’s at the University of Colorado are activated from CU’s Police Department Dispatch. Longmont’s sirens are activated from their Communications Center.

Siren Tests

Sirens are tested regularly on the first Monday during the months of April, May, June, July and August. The two-minute test is done at 10 a.m. The purpose of the test is to make sure the sirens work property and to educate the public about what action to take when they hear the sirens. All the cities in the county usually test the sirens at the same time.

When you hear a siren, you should:

• Tune in Boulder Municipal Cable Channel 8 (for those with cable TV in Boulder) or
• Tune in to radio stations KOA 850 AM, KBCO 1190 AM or 97.3 FM, or
• TV channels 2, 4, 7 or 9
• Listen for a voice message, if you are near a voice activated siren.

If an emergency has occurred, information about the situation and what to do will be available.

NOTE: Outdoor warning sirens may not be heard inside buildings or when residents are sleeping. They are primarily intended to warn persons in outdoor areas only.

It is estimated that about 50 percent of the public can hear a siren on a still day in the city of Boulder. During heavy rains or stormy weather, the percentage receiving a warning is reduced because of the noise associated with the storm and more people are indoors.