Flash Floods, Slot Canyons, and Kinetic Energy
The recent episodes of flooding in Nepal and the Grand Canyon are horrific, to say the least. My heart goes out to those affected at both locations. Each of the floods were the result of a different set of circumstances from a scientific standpoint, and both would seem to be worth a blog post.
I would like to start with the flash flooding in the Grand Canyon, and put off what will likely turn into a much more complex and lengthy discussion of Nepal until a few of life’s current misdemeanors abate for a bit.
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It is not my intention to devote this post to a discussion of the specifics of what occurred in northern Arizona over the past week or so. You can go online and find all you could ever hope for, as everybody and his brother’s third cousin dissect what happened, what didn’t happen, what should and shouldn’t have happened, and why the current direction of scientific inquiry in this country is either good or bad or ugly — said judgments likely depending upon one’s political affiliation more than anything that actually has to do with science.
I would much rather spend this post blathering about flash floods in general, and how all of us should be prepared to be proactive in our efforts to protect ourselves and loved ones, in case we find that our karma has taken us to flash flood country at the wrong time.
But before we jump in, I’d like to make sure we’re all on the same page regarding the energy contained in moving water. I think the easiest and fastest way to do this (at least for me) is to include a link to an earlier post — cunningly titled “Kinetic Energy” — that covers this in enough detail to get all of us up to speed. If you’re fuzzy about what Ek is, I’d encourage you to spend a couple minutes on this. I’ll wait…
Welcome back (and be careful where you swing that thing).
One final caveat: Much of this discussion is going to relate to areas in the southwestern United States, but don’t let that fool you: high water can exist and impact just about anybody on this planet. All it takes is enough water with enough people getting in the way — whether they know it or not, expect it or not, or are prepared for it or not.
With that said, and all of us nattering in the same language going in…
I actually have quite a few thunderstorm and flash flood stories that I share in class; some are personal, and others — such as my mom’s bedroom windows; the guy whose toilet had a metallic roof vent where his lightning rod should have been; the life-altering incident on the peak of San Jacinto — are episodes I either heard about or read in some journal or other.
One personal experience that may be germane in this situation has to do with a lovely springtime evening in the early 70s when Susie and I were dangling our feet over the south rim of the Grand Canyon, and watched as a thunderstorm barreled its way upriver from the west end of the canyon and blew itself out the east.
The flat-bottomed base of the thundercloud (a.k.a. the dew point, as described in Hot AND Humid) was just above eye level, and towered many thousands of feet above that. We may have been high (and mostly dry), but it was raining cats and dogs down in the canyon, with thunder and lightning, and all the other extraneous special effects that come along with a weather-spawned hissy-fit like this one.
A second also had to do with the Colorado Plateau — the “Four Corners” region in general, and the high country north and east of the Grand Canyon in particular, certainly do act as magnets for thunderstorms. This occasion also took place back in the early 70s. Susie and I had been married for less than a year, were still doing the education thing in southern California, and had decided to spend spring break looking for silver and turquoise jewelry on the Navajo and Hopi reservations of northeastern Arizona (this was before Native American turquoise had become a thing, and we found some AMAZING “old pawn” at prices we could afford).
We were on top of the Colorado Plateau and driving along Highway 160 east of Tuba City, and could see multiple thundercells scattered all across the upland (elevation +/-8,000’ so we had plenty of orographic lifting to juice up the sky). The storm cells were pretty obvious from the towering clouds capping the downbursts that were dumping their moisture and transferring it to the ground. (Yes, I know this is supposed to be a dry climate, but the local weather can do whatever it wants whenever it wants. Click here for more details about the differences between weather and climate.)
Originally hoping to make it as far as Four Corners itself, we managed to finally run under one of the thundercells that was sitting right on top of the highway. It was raining very hard — with lightning arcing to the scrub all around and rifle-shot cracks of thunder shattering the sky — so we pulled over and waited it out. By the time the cell had moved away we’d decided that we were too young and green to keep going, so we turned back. Feel free to review Turn Around, Don’t Drown for an earlier post the dwells on safety in the face of moving (and rising) water.
And a third reminds us that we can go from “too sexy for my shirt” to “mercy me, too, Pooh” in a matter of minutes! We were along Hwy. 24 west of Colorado Springs and spending the day exploring the Manitou Cliff Dwellings and the Garden of the Gods (both are definitely worth a visit). We had parked outside a small market and had headed in to get some water and snacks. When we got out of the car it was dry, and were probably in the store for less than ten minutes. When we got back to the door it was pouring down rain and the parking lot was already flooded — oh yeah, a thunderstorm with a serious downburst!
As usual, this storm was small and localized, with God’s own bucket of rain coming down in big drops over a very short span of time. The good news: all we had to do was wait ten minutes for the center of the low to move away and the rain to stop, and then another five or so for the water to drain and the flooded parking lot to dry again.
Which brings us to the overarching message (hopefully) contained in this blog post.
The point of all three of the stories has been to stress how you can go from a warm sunny day with blue sky and birds singing in every tree, to a massive downburst that can put inches of rain on top of your head in a matter of minutes.
Water flows downhill, and a lot of water can flow a long way downhill. Miles downhill. Tens of miles downhill. It may not even be raining where you are, but the flash flood can still wreck your afternoon! And the farther and faster it flows, the more Ek it contains, and the more stuff it can rearrange. Sometime this redistribution is benign and sometimes not, but no matter what, there is absolutely nothing we can do about it.
As the 4th Law of GeoFantasy continues to remind us: “Water always wins!”
One of the other things that are fairly common to the Four Corners region are called “slot canyons”. These are very narrow ravines, possibly structural in origin, but certainly carved in part by moving water. You really don’t want to be caught in a slot canyon when a flash flood roars through!
It is safe to assume that the Colorado River is a much larger body of water as it goes through the Grand Canyon than the stream that fills the slot canyon in the above image. The good news is, the physics and hydrology act the same in both cases. The bad news is that the increased size and popularity of the Colorado as it goes through the canyon attracts one heck of a lot more people, putting a whole lot more tourists at risk.
This isn’t to imply that being a tourist makes you dumb or stupid — it’s all too easy for any of us to get caught up in the moment, caught up in the heat of the day, and looking for a place to cool down the kiddos and silence their legitimate complaints. Add some testosterone and adult beverages, and an otherwise pleasant afternoon along the creek can turn ugly even before you have any idea you’re in trouble.
One last thing before I publish this ramble: Being who we are, the search for a villain will be immediate, and intense. As expected, Climate Change is an early favorite (and in this case the charge may hit closer to the mark than, say, in the Cyclospora outbreak we discussed a couple weeks ago). This snippet is taken from the lead article in The Morning (the New York Times; 6 September 2026) titled “Bummer Time” by David Gelles:
Downpours: With climate change creating stronger, more powerful rainstorms, communities around the country have been dealing with sudden downpours and flash floods. Waves of extreme weather swept across America this summer, unleashing torrents of water from Colorado to Massachusetts. In the past week alone, a deadly flash flood hit the Grand Canyon, and Tropical Storm Edouard drenched parts of southeast Texas.
No matter who or what will be determined to be responsible for the deaths in the Grand Canyon, I’m pretty sure we can expect more extreme weather events leading to more fatalities in the years and decades to come.
So, to close the circle: your safest approach is probably to pay attention to the regional weather forecast, and simply know when to choose not to go.
“Turn Around, Don’t Drown” before you get in trouble.
