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Sep 16 2013

A Few Good Reads (9/16/13): Colorado Flooding Update

National Guard said today they’ve conducted the most helicopter rescues since Hurricane Katrina. (@nicolevap, Saturday, Sept 4)

It’s a scramble this morning as the floodwaters are coming down across the Colorado Front Range and the damage is still coming to light. A number of folks in our office spent the weekend in the field helping tag and document high water marks on the Cache La Poudre and Big Thompson Rivers. There are also a number of other emergency issues that engineers in our office are involved with and looking at this morning. The flood watch is now on the South Platte River in the northeast region of the state. Search and rescue operations continue today to locate the over 1,200 people still unaccounted for and to keep evacuating folks trapped by the floodwaters.

Little relief from Colorado floods with six dead and 1,253 unaccounted for (Denver Post)

Emergency management officials said 17,494 homes were damaged, 1,502 homes were destroyed and 11,700 people were ordered evacuated…

Even as rescuers found stranded people and crossed them off the list of “the unaccounted for,” that list continued to grow as more people called police asking for welfare checks on friends and relatives they couldn’t reach.

The list across the state now tallies 1,253 people unaccounted for. The fear is that some of them are dead, Barth said.

Map of rainfall totals across eastern Colorado, Sept. 6-13, 2013

Engineers often refer to NOAA’s Atlas 14 to find frequency estimates: how often to expect precipitation of a given intensity and duration. Russ Schumacher (Colorado State University) used the atlas to calculate frequency estimates for the rains observed in the critical 48-hour window from 6 a.m. MDT Wednesday to 6 a.m. Friday. In doing so, Schumacher found that a large chunk of Boulder County and parts of several other state counties passed the 1000-year recurrence threshold. 

This doesn’t mean that such a rainfall would literally be expected once every thousand years, like clockwork. Rather, it’s a statement of probability: a 1000-year rainfall has a 0.1% chance of occurring in any given year. Such values shouldn’t be taken as gospel—there are important caveats, including the hard-to-model behavior of the most extreme events—but they do suggest how truly noteworthy this week’s rains were.

Helicopter Footage of 2013 Flood [Cache La Poudre River] (City of Fort Collins)

Short condensed ride up the Poudre, certain areas are labeled for location.

Larimer County Colorado Flooding Survey (2013LarimerFlooding)

This is video of Larimer County Colorado Sheriff Justin Smith’s helicopter flight to survey the flooding damage throughout Larimer County taken on September 14, 2013.

Video notes: 3:00 – Enter Big Thompson Canyon, 10:00 – Enter Drake, 18:00 – Enter Estes Park, 38:00 Lake Estes/Olympic Dam

Portrait of a historic deluge in Colorado (Coloradoan)

Once the storm reached Colorado, light winds and the mountains pushed it up high — and there it stuck, dumping for hours over Colorado Springs, Boulder and throughout Larimer County. In a matter of days, it dumped a year’s worth of rain in parts of Colorado. The rain fell onto burn scars, into dams and rivers; unlike a wildfire, it could not be mitigated or stopped, only endured. Days later, the damage it wrought is still being tallied, and if history is any precedent, it could take Colorado months to rebuild the roads and communities that were washed away.

7 Photos that show how destructive the Colorado Flooding is (Daily Camera)

Highway 7 is completely blown out from the South St. Vrain river about 12 miles west of Lyons, Colo.

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