Over the last few years I’ve been doing a lot of dam breach analyses. We use a Corps of Engineers computer program which models the breach flow leaving the dam and routes it through the downstream valley. The program has a very groovy feature where you can animate the flow in a pseudo-3D setup. Recently they added the capability to record .avi files of the animation.
This model has two lakesin it. I’ve breached the upper lake; it overtops the second dam so that one must be breached also. This also has a highway downstream.
You know, these little movies are just a bunch of still bmp’s, apparently. I wonder if I could edit them to include tiny people running away from the water …
The breach inundation map for that dam should be a matter of public record. For California, the agency in charge is Dam Safety: www.damsafety.water.ca.gov . I found this about Dixon Lake:
Dam No. : 834-002
Name: Dixon
Owner: City Of Escondido
County: San Diego
Lat-Long: 33.158 -117.04
Stream: Tr Escondido Cr
Year Built: 1970
Volume: 2500 acre-feet
That’s a fairly good sized reservoir, there. Someone at Dam Safety should be able to point you to the inundation map. Also, it should have an Emergency Action Plan (EAP) in place; this tells you what steps are taken in the case of imminent failure, or after a failure, or in the case of the owner releasing large amounts of water for any reason (should include evacuation routes for downstream areas). Some EAPs will also show expected times of peak flows at points along the downstream valley.
Well, we are always concerned that it might drown the fish.
That is HEC-RAS that I’m using, but I’ve used DAMBRK as well. I’m in consulting, currently. I recently realized that I’ve spent time in all areas: 2 yrs research, 4 years government, 15 yrs private, and even taught a class or two at the Junior College. It’s been fun.
Thanks. I think everyone loves their own corner of geekery. It’s not often that mine is of interest to others.
Soggy toast!
Seriously, the City’s risk management department might know more, such as predicted water depths along your street. You could compare that to your home’s floor elevation and see how you stand.
Do you mean from an emergency response perspective or a hydraulic modeling perspective?
From an emergency response perspective, I can see that closing a road for a few hours would probably be easier than evacuating 100 houses.
From a hydraulic perspective, usually highway crossings are modeled to see if they can pass the water; also we can see if the water will be ankle-deep or neck-deep if it does indeed cross the road. Dense urban areas typically have lots of little culverts which are not going to be able to handle the water - we often omit them from the model since they aren’t relevant. A related point is gathering data such as finished floor elevations of buildings - if the buildings are many we typically won’t do that. If only a handful are affected, we might include that in our data gathering.
I meant the hydraulic modeling perspective. It makes sense that culverts would be deemed negligible. When you say, “pass the water”, do you mean it would flow over the highways without damaging them, that the highway drainage system would handle and divert the water, or something else?
Ah, ok. I mean that the highway structure (be it bridge, box culvert, what have you) would pass the water from upstream to downstream without the water overtopping the highway.
Some of the larger structures are capable of this, and/or if the volume coming from the dam is close to the design flow, it will be ok. Overtopping is a problem for two reasons. One is the traffic - one can imagine the havoc if the interstate suddenly has a foot or more of water over it. The other is damage to the embankment.
If the water is less than a foot deep and the duration of the flow is less than half an hour, that would not be as great of a concern. Greater depths and longer durations will damage the embankment, and can wash them completely out.
