Science Snapshots: 10 Years since the Great Colorado Flood

My Peckers, please allow me to apologize for the lack of Science Snapshots recently. Thinks have been hectic in the Peacock household, on top of my constant fatigue plus insomnia because why the hell should I be able to sleep when I'm exhausted?

But today is a very special Science Snapshots, where we look back at the Great Colorado Flood which occurred 10 years ago. The anniversary was actually yesterday, but I didn't want to step on the toes of yesterday's remembrance.

Any other Front Range Peckers will remember this too. In September 2013, I was living in the city of Boulder, Colorado. I remember the week very well. It was cold and rainy after an early September that was atypically hot, producing multiple record high temperatures, and on Monday we were all quite happy with the cold and the rain. On Tuesday it started to get old. And on Wednesday the 11th, I was sending out energy to the universe that the rain would just stop already, please. But it didn't stop. It got worse.

I'm a hypocrite fam. You should always follow your country's Weather Service watches and warnings or however they title their weather forecast products. But I'm the first to run outside when the tornado siren blows, and I almost always ignore a flash flood warning. But that Wednesday, I decided maybe it was worth listening to that warning. After work, I parked outside rather than in our apartment complex's basement parking garage. And I waited and followed along on Twitter (no, I'm not going to call it that random letter). There were some disturbing images coming from Boulder Creek, likes this famous one.

Via hcn.org

They were mostly disturbing because they were University of Colorado students playing in flood waters along the creek, and let me tell you: just say NO to playing in flood water! There is legit every kind of feces, sewage, and plague floating around in flood waters. They're gross and they can really make you sick. Stay out.

College kids are going to be, well, kids, but aside from that the bike paths and underpasses around Boulder Creek are specifically designed as overflow, so a bit of flooding around the Creek wasn't a huge concern. Except it just. Kept. Raining.

My roommate and I went out on our back balcony and watched the rain and listened to the roar of the creek behind our apartment. I say creek, but more accurately it was an agriculture ditch. During a certain time of the year, a gate on Boulder Creek is opened to allow water to flow through the ditch and provide irrigation to farms. On September 11 the gate is closed, and that ditch is a trickle at best. But this night it was flowing so fast, so high, that it was actually roaring. As we watched, a giant cottonwood tree fell because the bank had eroded away so much it couldn't hold on anymore.

At about 9pm, all hell broke loose. There were news reports of people missing along certain roads in western Boulder that had washed out. The flood sirens started sounding. In Boulder, the flood/tornado sirens have the familiar sound but also a voice that issues announcements. Usually, it's "this is just a test." On that Wednesday, it was "move away from Boulder Creek immediately. Walk to higher ground."

It was hard sleeping that night, but we managed a bit after coming up with our escape plan. I had an awesome pool floaty, and we were going to put my cat in the middle of it and my roommate and I hanging off each side to keep it steady. It was a terrible plan, and we were wishing we owned kayaks. Fortunately we stayed dry in our home.

This was the first image I remember from the morning of the 12th.

This is a place called Dillon Road. Courtesy USA Today.

If I recall correctly, this accident had no fatalities.

In my little corner of the world, Boulder was cut off from surrounding communities for about a day. My roommate had fortunately listened to me about moving his car the night before, because there was about 3 feet of water in the underground parking garage. We were fortunate that although we were on the first level, the apartment was about half a story above the ground, plus on a bit of a hill. Many others experienced flooding in their homes. That creek behind our apartment continued to roar, all the houses back there had backed up sewers, the main cause of flooding in my area.

I didn't have enough toilet paper to make it until I could safely go anywhere again. My kind roommate gave me a roll. I was prepared for COVID based on this experience.

Like I said, we were very lucky. This was Longmont, just to the east of Boulder.

Via the Longmont Times-Call

This was Lyons, to the northwest of Boulder and up in the foothills.

Fema.gov

It took a long time to rebuild along highway 36 between Lyons and Estes Park, a mountain town that was cut off for months...residents had to drive west over the Continental Divide in order to leave town. It's still weird driving that route. One can see where things are no longer the same.

Highway 36 via Denver Post

That Saturday things had cleared up enough around Boulder that I could get my car out and go on a quest for toilet paper. This is where I have my last major memory of that week. I lived near the airport, and watching and listening to the chinook helicopters rescuing people stranded in mountain towns was surreal.

People being airlifted out of mountain community, Denver Post

But this is Science Snapshots, not Fireside Chats with Captain Peacock, so why on Cthulhu's doomed Earth did we get a year's worth of water in less than a week?

The rain was out of the ordinary in both its duration and its spatial extent. The system essentially stalled over Colorado due to a blocking ridge over the Canadian Rockies and a slow-moving cutoff low over the western US. A ridge is an area of high pressure, and when it just parks its ass without moving it causes blockage, which we can all understand now and then. You likely have experienced blocking patterns often in your life: just think of a time when the weather stayed the same for a week or longer. I'll also interject quickly that this is pretty specific to midlatitudes, so if you're from a tropical or polar region unfortunately I am just not familiar with your weather patterns as I'm not an expert in either of those regions.

That blocking ridge left the cut off low, meaning a low pressure system that is orphaned from the main westerly flow, parked and spinning to our west. That resulted in moist tropical air being transported into Colorado. It was juicy, and Colorado doesn't do juicy. It was even juicier than normal because the sea surface temperatures in the Gulf of Mexico were a few degrees warmer than usual. All of this meant that there was a lot of water being brought into the atmosphere of Colorado and most of it fell on Boulder and surrounds, and that shit was RARE. Fortunately, because a lot of us damn near floated away.

If you'd like to learn more about the sciency science, the definitive article is here:

I don't *think* it's behind a paywall, but if it is and you want it, email me at captstephenpeacock@gmail.com and I am authorized to share it.

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