Sobering results have come back from a preliminary analysis of the rain and flooding that traumatized the Colorado Front Range this month:
Expect it again.
Yes, record rains occurred. Yes, homes were swept away and lives claimed. Yes, it was rare and, in some cases, unprecedented.
But similar rains and flooding occurred in 1935, 1938 and 1965.
Climate change was likely a bit player in this recent flood, but it could increase the frequency of such flooding in the future, according to the study, which was done by university and federal researchers.
The rain and flooding were the result of a low-pressure system that stalled over Nevada and Utah. The counterclockwise, swirling motion of the massive low pressure system swept up monsoon-like moisture from the Pacific Ocean and swung it around and into the Front Range.
Making matters worse, moisture from the Gulf of Mexico was swept into Colorado from a little farther east.
The flooding “event” lasted from Sept. 9 to 15.
The total moisture content of the atmosphere above Denver on Sept. 11 was at record levels for that month, according to the study. As a result, most of the rain that fed the flooding fell over 36 hours from the afternoon of Sept. 11 until the early morning of Sept. 13.
Boulder set records for one-day precipitation (9.08 inches), two-day (11.52 inches) and seven-day (16.9 inches). The town got more rain in two days than had it ever received for the whole month of September. Records at Boulder date to 1893.
Similar records were set elsewhere.
The study concludes that the historical record is clear — this is an area that has seen extreme flooding. What has changed most noticeably over the years is development, which has placed more people and property in harm's way.
“Severe Flooding on the Colorado Front Range September 2013, A Preliminary Assessment,'' was done by the Cooperative Institute for Research in Environmental Sciences Western Water Assessment.
CIRES is a joint institute of the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder; the Physical Science Division of NOAA's Earth System Research Laboratory; and the Colorado Climate Center at Colorado State University.
Read more about CIRES and check out the flood assessment document below.