On the evening of July 28, 1997, the city of Fort Collins experienced a devastating flood that took the lives of five people and caused extensive property damage in the city. A tropical air mass from Mexico driven by monsoonal flow was pushed up the gradual but significant slopes of eastern Colorado towards the Rocky Mountains. Upon reaching the front range of the Rockies, this air mass became unstable over the western portion of Fort Collins. The lifting provided by the topography, coupled with light upper-level winds resulted in a rapid succession of extreme "warm-rain" thunderstorms, that dropped amounts of 9 to 11 inches of precipitation.
Saturation of the soil was a factor that increased flooding potential. Soils in the area were near saturation due to heavy rain showers on July 27 and the morning of July 28. The storm of 28 July, 1997, caused the largest storm-total rainfall accumulations ever observed in Fort Collins.
Data from historical preceding storms were reported by Wirshborn (1997) and Doeskin (1997). Six inches of precipitation fell over a 48 hour period in 1951, and 4.4 inches fell over 24 hours in 1977. The Colorado State Climatologists' report on the 28 July, 1997 storm is available on-line at: http://ccc.atmos.colostate.edu/~odie/rain.html.
The Fort Collins storm
of 28 July, 1997, is similar to the devastating flood that occurred in
July 31, 1976 on the Big Thompson River watershed, 30 miles south west
of Fort Collins. The Fort Collins storm is different, however, in
terms of the structure of the storm that caused it. Both storms produced
short duration, high intensity precipitation of approximately 10 inches
over a short time period. Furthermore, both storms tended to linger
because of light upper-level winds. The Fort Collins storm is different
because its' structure is more typical of tropical convective systems (saturated
air column at the ground surface, high precipitation production efficiency,
low echo centroid, low cloud top). The Big Thompson flood caused
$41 Million in damages and killed 139 people. Simons,
On November 6, 1997, a symposium on the flood was held on the campus of Colorado State University. Speakers at this symposium included City and University Emergency Response personnel, CSU Professors, Sociologists, Reporters, and others. The topics discussed at the symposium covered the range of affects/impacts the flood had on the lives of everyone in and around Fort Collins.
Notes taken during this symposium can be read by clicking here.
Other LinksA personal testimony http://tdholder.com/timsfort.htm