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Catastrophic Flood in Boulder, Colorado

By: Christopher C. Burt , 7:50 PM GMT on September 12, 2013

Catastrophic Flood in Boulder, Colorado

An all-time 24-hour record rainfall of 9.08” (as of 6 p.m. 9/12 MT--almost double the previous record) has deluged the city of Boulder, Colorado resulting in widespread flash flooding and the deaths of at least three people so far. 12.27" has accumulated since Monday 5 p.m. (September 9th). Needless to say, these are numbers that surpass most tropical storm events. Other locations in the Boulder and Rocky Mountain Front Range have picked up over 11” of precipitation in just the past 24 hours. The official Colorado state record of 11.08" for a 24-hour period set at Holly on June 17, 1965 might be in jeopardy. UPDATE A site near Eldorado Springs in Jefferson County has reported 14.60" of rainfall as of 9:40 p.m. MT on Thursday evening. It is not clear if this is a storm total or 24-hour total.



Bridge washout and its results at Highway 287 and Dillon Rd. in Lafayette just east of Boulder. Photo by Cliff Grassmick in the Daily Camera Boulder County News.



Radar estimated rainfall for the 18-hour period between 5 p.m. September 11 and around 11 a.m. on September 12th MT across north-central Colorado. You can see how Boulder rests in an area of 8”+. Map from NWS-Denver office web site.

According to the Western Regional Climate Center’s historical data set, Boulder’s former 24-hour precipitation record was 4.79” on July 31, 1919. The September record was 3.05” on September 4, 1909. Records began in October 1893 with some months missing. The CoCoRaHS (Community Collaborative Rain, Hail, and Snow Network) observers have reported the following 24-hour precipitation amounts as of Thursday (September 12th) morning (I'll update this on Friday):



Flooding is also occurring up and down the length of the Front Range from Colorado Springs (where 3.68” of rain has so far fallen) to Longmont (with 3.37” so far). In both cities mandatory evacuations are taking place in several neighborhoods.

The cause of the excessive rainfall is a deep plume of monsoon moisture from the south overriding a cool and moist air mass with orographic lift enhancing the rainfall along the Front Range and its nearby cities.



Show-and-tell graphic of the cause behind all the heavy rainfall in Colorado the past few days. It will continue into the near future. From NWS-Denver office web site.

The full extent of the damage and number of storm-related fatalities has yet to be determined (the rain continues to fall heavily in many locations) but the flooding, at least in Boulder, will be of historic proportions.

Flood History of Boulder

Boulder is considered to be Colorado’s ‘most at risk’ city in terms of potential flood damage. This is because it rests against the mouth of a canyon (the Boulder Canyon) from which a creek (the Boulder Creek) bisects the heart of the town.

Serious floods have affected downtown Boulder in 1894, 1896, 1906, 1909, 1916, 1921, 1938, and 1969 with the worst being those of May 31-June 2, 1894 and May 7, 1969. The flood of 1969 was the result of four days of almost continuous rainfall (11.27” measured in Morrison and 9.34” at the Boulder Hydroelectric Plant three miles up Boulder Canyon from town). There was one death reported and “many thousands of dollars” worth of damage including two bridge wash outs. The flood of 1894 was considerably worse with many causalities although no specific number of fatalities has ever been determined. A brief account of the flood appears on the “Front Range Flood Histories” web site: "In the Left-hand Creek basin to the north of Four Mile Canyon Creek, the mountain towns, mining camps and upstream canyons of the area were perhaps the most severely affected by the 1894 flood. Most were virtually wiped off the map.....Left-hand Canyon areas sustained heavy damages. All bridges were washed out and roads obliterated. Sheriff Dyer stated that Left-hand Creek was over a half mile wide in places and that the farms along that creek were piled knee high with debris and sand....8.54 inches of rain from May 30 through June 1 was reported in Ward.” The estimated water flow on Boulder Creek at 4th Street was 11,000-13,500 cfs (cubic feet per second).



A photo of what was supposed to be Canyon St. in Boulder during the 1894 flood. A caption that goes along with this photo on the Boulder Flood Safety web page says “The eventual repeat flood of this magnitude may well cause hundreds of millions of dollars of damage.” It just may be that that day has arrived. Image from Denver Public Library Archives.

KUDOS: Thanks to Bob Henson of UCAR for updating precipitation totals in Boulder.

Christopher C. Burt
Weather Historian


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

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18. MMZ
5:55 PM GMT on September 28, 2013
Regarding the recent Boulder flood I'd like to find photos that express its 'magnitude', rather than specific, detail photos I see so often. The photo of the 1894 flood shown above is good because the viewer can see Canyon Blvd and see the Flatirons in the distance and deduce the location, the depth of water and see the extent of flooding. Anybody have a good source of viewing high vantage points or aerials of Boulder that show the flooding as well as give a sense of location from where the photos were taken? What I don't need to see are aerial photos looking straight down, zoomed in, but rather I;d like to 'oblique' angle photos with the horizon, that reveal location and perspective, of both north and south Boulder Creeks and flooded areas nearby.

Some lingering questions I still have: Did Boulder Creek from the canyon to say 28th Street actually overflow its banks? Same with S. Boulder Creek? ANd if so, how much water was in surrounding areas? How deep was the water on say Canyon at 17th, or Pearl St? And of that water downtown, how much was from the creek overflowing, and much was accumulated rain and runoff that did not originate from the creek?

Member Since: December 31, 1969 Posts: Comments:
17. WunderAlertBot (Admin)
9:19 PM GMT on September 16, 2013
weatherhistorian has created a new entry.
16. sunlinepr
8:26 PM GMT on September 16, 2013
Someone Here knows???.... why with the wv filter the area W of S California shows a black color? (Very dry area) Is there the equivalente of a SAL there or SC air layer (SCAL)?... Looks like a very dry area....

IR View



Enhanced WV view... (Black area)

Member Since: December 31, 1969 Posts: Comments:
15. 1900hurricane
6:35 PM GMT on September 16, 2013
Also, with an abundant moisture tap coming from the south at the surface coupled with the easterly winds at cloud level, this Skew-T shows basically an orographic worst-case event.

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14. 1900hurricane
6:21 PM GMT on September 16, 2013
Seven day rainfall estimates from along the front range are fairly large, with some locations exceeding their yearly averages.

Link
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13. Neapolitan
5:08 PM GMT on September 13, 2013
I find this map fascinating. It displays precipitation anomalies across the US (and Puerto Rico) over the past seven days, with those anomalies expressed as a percentage of normal for the period. The map shows hundreds of thousands of square miles of the Rockies that have received 300% - 600% of what they normally should have, along with many other hundreds of thousands of square miles that have received little to none of what they normally would. Extremes seem to rule the image; there's very little grey showing that would indicate "normal".

wet
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12. Christopher C. Burt , Weather Historian
4:41 AM GMT on September 13, 2013
Quoting 11. Astrometeor:
Hi Chris, thanks for the fresh blog on this horrific flood. We have a blogger that lives just outside of Nederland, CO, here's his blog:

MrMixon


Super blog by Mr. Mixon. I suggest all WU readers follow this. He (and the comments) seem to be the best most up-to-date info on this unfolding event.
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11. Astrometeor
4:20 AM GMT on September 13, 2013
Hi Chris, thanks for the fresh blog on this horrific flood. We have a blogger that lives just outside of Nederland, CO, here's his blog:

MrMixon
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10. Christopher C. Burt , Weather Historian
4:18 AM GMT on September 13, 2013
Quoting 8. RickyRood:
So the local USGS has called it 100 year flood - so far. Still raining.

I should be arriving tomorrow. Trying to figure out how to pick my way through the closed roads.



Just heard from Bob Henson and he confirms that the official 24-hour Boulder (COOP) total for 6 p.m. Wednesday to 6 p.m. Thursday is now an amazing 9.08"! 12.27" since Monday. Holy cow! Still raining hard in the foothills, I'm fearing some very bad news from the hill communities above Boulder when all is said and done.
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9. whitewabit
2:53 AM GMT on September 13, 2013
Very nice blog on some of the reasons behind this flood ..

Stay safe Dr Rood ..
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8. Dr. Ricky Rood , Professor
2:50 AM GMT on September 13, 2013
So the local USGS has called it 100 year flood - so far. Still raining.

I should be arriving tomorrow. Trying to figure out how to pick my way through the closed roads.

Member Since: December 31, 1969 Posts: Comments:
7. Christopher C. Burt , Weather Historian
1:41 AM GMT on September 13, 2013
Quoting 4. RickyRood:
Hi Chris, nice article.

The picture you show of Dillon Road and US 287 not far from my place. (Unfortunately for me, I am stuck in Ann Arbor right now.) It is at the confluence of creeks and culverts and highways. It's also about 10 miles downstream from mountains and Boulder after the water has had a lot of area to spread out.

Looks to me as if the flood planning in Boulder has reduced damage from what it could be. Different story up in the mountains where they have all of the fire damage and now mudslides. Some of those towns truly cutoff.

ricky



Indeed. So far it seems the flow at 14th St on Boulder Creek downtown has just been 3,100 cfs whereas the 1894 event was four times that.
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6. Christopher C. Burt , Weather Historian
1:39 AM GMT on September 13, 2013
Quoting 5. ColoradoBob1:
I was in the Big Thompson Flood in 1976. This is much bigger , that one was just one drainage , this goes all the way down into New Mexico.

“The rainfall totals from when this event began are going to be record breaking, they already have been,” said Kerry Jones, a National Weather Service meteorologist in Albuquerque.

Jones said it’s likely some areas could see 6 to 10 inches of rain by the weekend. In one spot in the Guadalupe Mountains of southern New Mexico, more than 11 inches fell in a 24-hour period, which forecasters described as “unbelievable.”


Link


I'd like to know the source of the "more than 11" in 24 hours in NM. The NM state record for 24 hours is 11.28" at Lake Maloya on May 19, 1955.
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5. ColoradoBob1
1:33 AM GMT on September 13, 2013
I was in the Big Thompson Flood in 1976. This is much bigger , that one was just one drainage , this goes all the way down into New Mexico.

“The rainfall totals from when this event began are going to be record breaking, they already have been,” said Kerry Jones, a National Weather Service meteorologist in Albuquerque.

Jones said it’s likely some areas could see 6 to 10 inches of rain by the weekend. In one spot in the Guadalupe Mountains of southern New Mexico, more than 11 inches fell in a 24-hour period, which forecasters described as “unbelievable.”


Link
Member Since: December 31, 1969 Posts: Comments:
4. Dr. Ricky Rood , Professor
9:59 PM GMT on September 12, 2013
Hi Chris, nice article.

The picture you show of Dillon Road and US 287 not far from my place. (Unfortunately for me, I am stuck in Ann Arbor right now.) It is at the confluence of creeks and culverts and highways. It's also about 10 miles downstream from mountains and Boulder after the water has had a lot of area to spread out.

Looks to me as if the flood planning in Boulder has reduced damage from what it could be. Different story up in the mountains where they have all of the fire damage and now mudslides. Some of those towns truly cutoff.

ricky

Member Since: December 31, 1969 Posts: Comments:
3. Ameister12
8:08 PM GMT on September 12, 2013
Thanks Christopher!

Hopefully this rain will come to an end soon. Some of the pictures and video I've seen from the area are terrifying!
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2. barbamz
8:03 PM GMT on September 12, 2013

Thanks a lot for the information. This is a screenshot I just took from the live coverage on 7News.
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1. Patrap
7:52 PM GMT on September 12, 2013
Published on Sep 12, 2013

Colorado Flash Flood Video: Man Rescued from Overturned Car during Severe Flood Boulder Colorado (CNN) -- Emergency crews in Colorado braved racing flood waters early Friday,



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About weatherhistorian

Christopher C. Burt is the author of 'Extreme Weather; A Guide and Record Book'. He studied meteorology at the Univ. of Wisconsin-Madison.

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