Abstract: Opening Plenary Session  1:30 pm (BACK)

Colorado’s Extraordinary Flooding in 2013: Data Issues, Relevance, and Lessons Learned

Robert D. Jarrett, Ph.D.
Applied Weather Associates, LLC
Monument, Colorado

In 2013, Colorado experienced one of its worst flood seasons in its historic record. During July and August, the Waldo Canyon area in Colorado Springs experienced three moderate thunderstorms that normally would not have produced any flooding in its forested watersheds.  However, these rainstorms occurred over the 2012 severely burned Waldo Canyon area, producing true “wall of water” floods causing loss of one life and extensive damages.  Additionally, over a week of sustained precipitation in mid-September produced up to 20 inches of rainfall over several areas of the Front Range from central Colorado extending north to Wyoming.  The hardest hit regions were in Boulder and Larimer Counties.  Rainfall annual exceedance probabilities were less than 0.001 (greater than 1,000-year recurrence interval).  The storm produced widespread flooding that resulted in ten deaths and about $2 Billion in damages.  Man-made dam failures, landslides, and debris flows with their own associated dam failures all served to exacerbate flooding in several mountain streams, in some cases tripling the peak discharge values.  All scientists, engineers, and planners require sound data and interpretations to help the region recover more efficiently and effectively from flood events, as well as to help mitigate the effects of future floods.  Estimating the magnitude and frequency of flooding requires substantial, yet cost-effective, peak discharge documentation.  One of the most important components of flood science is rapid and reliable data collection on a regional basis.  This presentation provides an overview of the previously discussed storms, impact issues, and progress in hydrologic modeling.  There is a need to assess lessons learned following this and other historic floods such as the infamous July 1976 Big Thompson Canyon Flood.  The presentation also provides a basis for discussion of the future direction and needs of flood science in the Rocky Mountain Region.