1.4
Historical Flooding in Colorado in 2013 (Invited Presentation)

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Tuesday, 4 February 2014: 9:30 AM
Georgia Ballroom 1 (The Georgia World Congress Center )
Robert Henson, UCAR, Boulder, CO; and M. Kelsch and R. S. Schumacher

An exceptionally prolonged rainfall event across the Front Range of Colorado produced record single- and multi-day totals at a number of stations. A total of 9.08 (230 mm) was measured in Boulder for the 24 hours ending at 0000 UTC on 13 September, and weekly totals for the period 815 September were in excess of 17 (432 mm) at several locations. In some cases, the estimated recurrence intervals exceed 1,000 years. These rains produced record floods and severe damage within the St. Vrain and Big Thompson watersheds, with major damage also reported along smaller creeks in and near Boulder. As the flood crests moved downstream, they continued to inflict widespread damage along the South Platte River valley well east of the Front Range. This presentation will focus on aspects of prediction and observation relevant to this high-impact event, including the skill of numerical models in predicting the location, intensity, and duration of the extreme Front Range rainfall and the meteorological and hydrological factors that together determined where the most severe flooding occurred.