I've enjoyed a month's vacation from blogging, but now am getting back the creative urge, so hopefully I can post more regularly on the many interesting events, both local and global, involving fluid mechanics in geology!
CNN is reporting today that a "boil" has caused an evacuation of about 600 people from Hamburg, Iowa. Hmmmm...I hadn't a clue about boiling levees! Turns out that it's a well-known and well-studied phenomenon because it can lead to rapid levee failure. The boil noticed today appears to be a hole less than 1.5" diameter that created a small geyser of water erupting onto the dry side of the levee. A-ha--if they had said "geyser," I'd have gotten the idea much sooner! Black Hawk helicopters are being used to drop sand bags onto the levee because it is deemed to dangerous to send in a ground crew.
Here's a primer from the Army Corps of Engineers on levee failure and repair. A "sand boil" from a levee is a small hole created by water seepage through the levee. Water flows through (sometimes being so turbulent that it appears to boil), creating the "geysers" noticed today. Sand boils occur in earthen dams, but the phenomenon is usually referred to as "piping," not boiling. If the seepage water is dirty, it indicates that material is being eroded from the levee and that the integrity of the levee is threatened. If you ever need to sandbag your premises, check out the instructions on the primer sheet! Even shows how to reduce fatigue while filling sandbags!
I discussed liquefaction earlier in a post about the Canterbury earthquake, without pointing out that the term "sand boil" is sometimes applied to those features.
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| A sand boil on April 27, 201; along the levee near Hickman, Ky. Army Corp of Engineers have built a sand bag ring to allow the water to seep out but to contain sediment within the ring, in hopes of building up pressure from the weight of the sediment to prevent a major break. AP Photo/The Paducah Sun, by Stephen Lance Dennee, as published in the Washington Post |
Here's a primer from the Army Corps of Engineers on levee failure and repair. A "sand boil" from a levee is a small hole created by water seepage through the levee. Water flows through (sometimes being so turbulent that it appears to boil), creating the "geysers" noticed today. Sand boils occur in earthen dams, but the phenomenon is usually referred to as "piping," not boiling. If the seepage water is dirty, it indicates that material is being eroded from the levee and that the integrity of the levee is threatened. If you ever need to sandbag your premises, check out the instructions on the primer sheet! Even shows how to reduce fatigue while filling sandbags!
4 comments:
There was a lot of concern over sand boils during the Mississippi River floods as well. In particular, I remember some large ones being reported in Cairo, and that being a small part of the reason the Bird's Point floodway was opened. The Cairo levees were high enough for the projected crest, but they were concerned about seepage erosion weakening the levees and causing failure if super-high water lasted a more than a couple of days.
Hi, Anne,
Thanks for pointing this out! I took too long a vacation (part of it in the bottom of the Grand Canyon blissfully out of touch with the world for a week!) and didn't cover that, but you are correct and I should have said that sand boils are quite common. Guess they just don't make headlines all that often!
Cheers!
Hi Anne!
Thank you so very much for posting this! I live in Michigan & have been anxiously watching for stories on this because one of my very best friends lives in Council Bluffs, IA. A reliable inside source let her know a few days ago that if the already crumbling earthen dam (on Indian Creek, I believe)near her family's home were to completely fail due to delays in the controlled release of pressure on levees/dams upriver from her location, the entire town of Council Bluffs would be basically leveled by a tsunami-force wall of water. The citizens would have less than 30mins notice. Yet no one has officially stated this possibility in order to give those people the warning that this isn't simply a potential of flooding, but a potential of total destruction. The deteriorating condition of this earthen dam was of major concern last year, as well, yet wasn't repaired.
Like she said, she'd rather have the water slowly seep into her home than have a wave completely level it. Makes sense to me. Her family is busily evacuating as I type this.
Levee boils. What can you tell me about the Dayton, OH flood of 1913?
California levee designers prefer slurry walls to control material transport.
What can you tell me about lessons learned from southern Illinois floods, 1997. Is there a downstream notch in the levee on the sacrificial side?
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