Colorado Deluge: Flooding Before and After as Seen From Space

By Tom Yulsman | September 15, 2013 2:57 pm

An animated gif consisting of before and after false-color satellite images of the Denver-Boulder area. Water is black or dark blue; sediment-laden water or muddy ground is pale blue; vegetation is green; and bare earth is tan. (Images: NASA. Animated gif: Tom Yulsman)

As I write this on Sunday at 10:30 a.m. from my home near Boulder, Colorado, it is pouring buckets — again. Flood warnings are once again up for a region that has already suffered a 1,000-year rain event, and which is reeling from heart-rending death and destruction.

So far, hundreds of people are unaccounted for. Moreover, four people are confirmed dead, but search and rescue has taken precedence over looking for additional victims. So that grim toll is definitely going up, probably significantly.

My family and I are safe. Niwot is pretty much high and reasonably dry. The only significant impact we’ve experienced is a boil-water directive.

In the coming days I’ll be posting more on the continuing disaster here, including photos I shot of a building that was literally ripped in half by an intermittent spring that turned into a rampaging monster of water, boulders and mud. Also, a piece I’m working on now questioning whether hundreds of oil and gas wells in Weld County that have been affected by flooding are causing contamination of surface waters.

I the meantime,  I thought I’d post the animated gif above showing what our region looks like in before and after satellite images. Both false-color images were acquired by NASA’s Aqua satellite.

The first one shows the view from orbit on September 7, before the flooding. The second was captured yesterday, Sept. 14, when the clouds parted for a while to reveal what several days of unprecedented rain have wrought. In the false-color scheme, water is black or dark blue; sediment-laden water or muddy ground appears pale blue; vegetation is green; and bare earth is tan.

In the before image, water is barely detectable in the South Platte River and the tributaries leading into it. In the after image, the river’s flood plain has filled in with a turquoise blue color.

Here’s a map of what that flooding likely looks like in a portion of that image, as well as the impact on roads:

Road closures in Weld County are shown in red. The blue shows the extent of water in a 100-year flood. The city at the confluence of two rivers is Greeley. (Source: Weld County Office of Emergency Management)

This map shows the 100-year flood extent for creeks and rivers in Weld County. (In other words, the extent of a once-in-a-hundred year flood, in light blue.) The South Platte River comes in from the south and is joined by the Cache La Poudre River by the city of Greeley.

An interactive online map that allows you to determine the actual flood extent is not working right now, so I’m not sure whether flooding has equaled the 100-year level on these waterways.

But given that early this morning, at least one river gauge downstream of Greeley registered flows that surpassed the previous record set in 1965, I think it is very likely a 100-year flood — at least. Click on the thumbnail at right to see that record of that hydrograph. (And click here to access this as well as other hydrographs around Colorado and the nation at the Advanced Hydrological Prediction Service of the National Weather Service.)

Channel 7 here in the Denver area has reported that the South Platte has flowed at up to about 500,000 cubic feet per second during this event. I haven’t been able to confirm that number yet, but the hydrograph above suggests this number may well be correct.

To put that flow in perspective, consider that a cubic foot of water is equivalent to a basketball weighing 60 pounds. So this works out to 30 million pounds of water flowing past a given spot on the South Platte every second.

  • Stephani Schupbach

    Thanks for posting the gif. According to, the South Platte was near 10,000 cfs at its peak at the Ft Lupton gauge and almost 6,000 at the Commerce City gauge. In Ft. Collins it was over 9,000 cfs on the Poudre and Boulder Creek at 75th Street was near 7,000cfs. I could be reading the graphs wrong (or maybe the gauges aren’t working) but 500,000 cfs seems hard to imagine. I appreciate what Channel 7 has done during all our emergencies, but they are the same people who tweeted Red Rocks was flooded to the 30th row, which turned out to be a hoax. I hope you continue to stay safe and relatively dry.

    • Tom Yulsman
      • slincoln

        670,000cfs for the S Platte River is almost a physical impossibility for that area. Rating curves need major scrutiny during extreme events, and are frequently extrapolated to values that are not representative.

      • Stephani Schupbach

        Thanks for the link; I see what you mean. I wrote to the USGS Colorado Water Science Center for some clarification and the USGS Office of Communications and Publishing said, “The peak stream flow values for the South Platte River are not going be officially determined until the flooding has subsided and all the stream gage data from the flood is gathered and analyzed.
        If you have further questions, you can contact the USGS Colorado Water Science Center. There
        is also information on about the flooding in Colorado on the USGS Flood Information website.”

        I’m sure more definitive information will arise in the coming weeks.

      • slincoln

        Tom: you’ll now notice that for the entire Denver/Boulder NWS area, the rating curves have been removed from Advanced Hydrologic Prediction Service (AHPS) hydrographs. I’m sure it is because people were erroneously extrapolating flow rates from upper ends of the rating curve and/or guessing values beyond the curves.
        We’ve had to do it before on the Mississippi River, although a rating curve for those locations has much more uncertainty on any day due to loop rating effects.

    • Inmyriver

      All those S. Platte gauges you mentioned are upstream of the St. Vrain, Big Thompson and Poudre confluences which contributed a lot of volume, so Ft Lupton never got too huge. Ft. Morgan is positioned to see all of the discharge. They went from 6500 cfs to almost 50K in just a few hours Sunday afternoon.

      • Stephani Schupbach

        Howdy — yes, I understand the importance of the downstream locations of the gauges. But 600K cfs?? Anyway, you’ve probably read the other posts by now and understand that’s simply not realistic.

  • CaseMan

    Hundreds of oil wells more like tens of thousands in Weld County

  • slincoln

    Tom… you can’t necessarily use the interval since the previous record as a predictor of average recurrence interval. It will be estimated by the USGS using the context of the historical record and how this event’s estimated flow relates.

    • Ron

      670,000 cfs would be 15 acre feet per second, a lot of water.

      • slincoln

        An incredible amount of water… more than the S. Platte can hold. And way more than what actually passed by any of the gauging locations in the area.

        • Ron

          Agreed. That volume of water reported would roughly equal 15 football fields filling with water one foot deep every second. However, as of yesterday, the S. Platte was still running over one mile wide along I-76 toward Nebraska. It was much wider on Sunday.

  • Billerica1

    Will all this flooding help the level of Lake Powell and Lake Mead in the drought problems at th Hoover Dam?

    • slincoln

      Most of the rainfall was east of the continental divide. The S. Platte River is getting most of the runoff, and it flows east toward the Missouri and the Mississippi.

      • TehGBear

        Most but not all? I too am curious as to the direction of this storm and if it will drop any notable amount of water over the watershed of the Colorado River.

        • Inmyriver

          Lake Powell saw a bump in the middle of September which brought up the level a bit, but it was from the cumulative effects of rain across the watershed. If this event has any measurable effect on the lake it will take at least a couple of weeks to display.

  • dieselpop1

    1 gallon of water weighs about 8 pounds. There’s no way a basketball of water could weigh 60 pounds.

    • Awetmedic

      True enough, but the 30 million figure is close if you multiply the weight of water per cubic foot (62.4) x his figure of 500,000 gallons. He must not know that a standard basketball has a circumference of 29 inches which gives an area no were close to a cu/ft. He doesn’t know balls.

  • Tom Yulsman

    To everyone who commented and offered corrections, thank you! I’ve been distracted over the past 10 days, so I haven’t been able to engage in the discussion as much as I’d like. Also, I definitely make some mistakes in the heat of what was happening. My apologies for that. I try to do my best, but sometimes I miss the mark.

  • socalbum

    Wow, nice, you are all so brilliant with your water gauge flow assessments and what not, but not a single one of you, that I can see, takes into account, or even barely mentions, the potential environmental disaster visited on this area as a result of the influx of so much water – are you really scientists or just laypeople like myself claiming to know so much? FRACKING and the 20,000+ wells, containment ponds, broken fuel lines, spilled evaporation containers, etc., have inundated the region with their toxicity as a result of the flooding. What about gauging and reporting on those “flows”?



ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.


See More


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Collapse bottom bar