In September, 2013, a slow-moving cold front stalled over Colorado, clashing with warm humid air from the south, resulting in a severe rain event that lasted a week and caused catastrophic flooding and damage along Colorado’s Front Range. Rain began the afternoon of Monday, Sept. 9, and intensified throughout the week. In Boulder, just one of the many hard-hit communities, rainfall for the week exceeded 18 inches, contributing to a monthly rainfall total far exceeding any other month since recording began in 1893. Boulder’s average September rainfall is less than 1.6 inches!
The first reported mudslides resulting from the intense rains occurred on Wednesday, Sept. 11. Flood impacts were widespread, particularly across northern Colorado, where rockslides, landslides, mudslides and washouts caused major damage and, in some cases, total destruction of residences, roadways and local access bridges. Flooding was so severe that it fully re-routed creeks and rivers by more than 500 feet in some locations.
Colorado Governor John Hickenlooper declared a disaster emergency on September 12th. Two days later, a Major Disaster Declaration was issued (DR-4145) by President Obama for federal aid to supplement state and local recovery efforts in the area affected by severe storms, flooding, landslides and mudslides. Initially the presidential declaration included 14 counties, but four counties gained funding from the original declaration due to CDOT’s rapid response and compilation of detailed damage assessment reports that demonstrated the need for additional assistance.