BOULDER - Jim Brautigam, the city manager for the City of Boulder, signed and issued a local disaster and emergency declaration for the area after floodwaters swept through the city.
The declaration allows the city to request necessary support from the state to help the city respond to the torrential rains and flooding that started Weddesday afternoon.
The Boulder County Sheriff's Office confirmed to 9NEWS that a "wall of water" came down Left Hand Canyon Thursday morning and trapped a firefighter in a nearby tree.
Emergency crews were able to rescue the firefighter. The water is also causing damage to many buildings.
Highway 36 at Longmont Dam Road was completely destroyed by the floods. The Bouldersheriff urges people to stay on high ground during the storms.
Residents in Boulder's University Hill reported flooding in house basements.
Several creeks in Boulder County have flooded, including Left Hand Creek, Four Mile Creek, Coal Creek Creek and Saint Vrain Creek, according to the National Weather Service in Boulder.
Boulder Creek is running 10 times its normal rate but remains in its banks. Sirens were going off near the creek to warn people to stay away.
Up to 3.5 inches of rain has already fallen in the area. Flash flooding is also occurring in the Erie, Lafayette and Niwot areas.
Flash flooding is expected to become more widespread as heavy rain continues into Thursday morning.
Authorities are asking motorists to stay off the roads. Xcel Energy is reporting more than 1,800 Boulder-area customers are without power.
Boulder County Government buildings will be closed on Thursday as a result of the severe flooding.