Breach Parameters for an Earth Embankment Dam
Breach Parameters for an Earth Embankment Dam
(OP)
When simulating a dam breach for the design storm, are you supposed to breach it at the highest water surface elevation, or should you take into account the erodibility of the soil and calculate velocities over the dam to determine when the dam will breach?





RE: Breach Parameters for an Earth Embankment Dam
On that topic, see
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Click on the picture for a bigger view. The picture is not the dam that failed, but another one in the area. This one must have been overtopped by a pretty good depth to have that big tree on the crest. I think the scallops in the crest are scarps from head-cutting.
Reading these news stories always seem a bit voyeuristic, but I suppose it's OK if they remind us of how careful we need to be with dams and public safety. It's OK to stare at car wrecks if it reminds you to drive more carefully (and you don't cause another wreck while staring).
RE: Breach Parameters for an Earth Embankment Dam
RE: Breach Parameters for an Earth Embankment Dam
RE: Breach Parameters for an Earth Embankment Dam
RE: Breach Parameters for an Earth Embankment Dam
The best source on breach parameters is:
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That's a pretty thorough review of the subject.
Please do not use the prediction of breach occurrence in the Dewey & Oaks and Dewey & Gillette papers cited therein. It's been shown to be questionable, or worse.
As to the depth of overtopping to initiate breaching, you might pick 1 to 2 feet or even more, depending on the erosion resistance of the material and the duration. It is not uncommon for dams to be overtopped by 2 feet and survive, if they are constructed of clayey material, have good turf cover, etc. It's going to be a SWAG anyway.
I'm curious about how much difference there is in the peak Q between 1 foot and 4 feet of overtopping. Keep us posted please.
RE: Breach Parameters for an Earth Embankment Dam
Q=CLH^(1.5)
1'=2800 cfs
4'=22,400 cfs
RE: Breach Parameters for an Earth Embankment Dam
RE: Breach Parameters for an Earth Embankment Dam
RE: Breach Parameters for an Earth Embankment Dam
If you are doing an incremental assesment it looks like you already have a problem if your design storm is overwhelming your dam to such a degree that you do this timing thing.
I would run the breach for a 1 foot overtopping storm that lasts longer than the material will handle(the NRCS SITES is a good guessing tool) and then just stick the breach on the top of the "design storm" for a breach.
As for the time for breach, be really careful for those long breach formation times. The breach formation time is typically is from the initiation of removal of crest materail, so most of that downstream section is gone from an embankment dam.(Think Tom Sauk) I typically like to look at a sensitivity analysis and run a few methods( the Tony Wahl USBR papers are fabulous). I like the NWS BREACH model but rely on the empirical stuff.
Good Luck, because evacuation plans will be based on your work. I think engineers are really under bidding what flood inudation mapping requires.
RE: Breach Parameters for an Earth Embankment Dam
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