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Rivers Dam scenarios

Rivers Dam scenarios

Abbysmum
Joined: Mar 2009
Posts: 5039

Abbysmum
Joined: Mar 2009
Posts: 5039

Rivers Dam scenarios
7/2/2020 at 4:35 PM

Is the anticipated peak with or without considering the volume of water that a catastrophic breech at Rivers would create?

If it is NOT, have they said what the range of peak from that event could be?

If there was a breech at Rivers, how much time would Brandon have before the water reached the Assiniboine Valley and/or Brandon? Hours? Days?
Adam

Joined: Mar 2005
Posts: 15663

Adam
Joined: Mar 2005
Posts: 15663

Rivers dam
7/2/2020 at 6:05 PM

Hope you don't mind that I split this off into its own thread!

Those are super important questions to ask and have answered, am hearing a lot of concern from folks on what happens if Rivers fails. I can’t say for sure and haven’t seen or heard a definitive answer but I go on the assumption that that forecast peak range is if upstream structures hold. By wanting people downstream from Rivers cautioned to have an evacuation plan there has to be a conceivable scenario where the dike couldn’t handle the water. Maybe they just flat out don’t know, maybe there are just too many variables around different levels of dam failure and these things must be a balance between informing and not inciting unnecessary panic but I hope there's priority put on transparency.

If anyone finds a link to speak to more definitively, please share.

Interesting thing is that yesterday they actually revised the top end of the forecasted peak range downward by a couple of feet compared to the day before. FWIW, 1180.1 at 18th St is still showing as the high end in the daily flood forecast just posted at https://gov.mb.ca/mit/floodinfo/floodoutlook/forecast_centre/flood_sheets/2020/20200702%20Assiniboine%20River%20Flood%20Sheet.pdf
Trevor B

Joined: Apr 2005
Posts: 8881

Trevor B
Joined: Apr 2005
Posts: 8881

I think
7/2/2020 at 6:32 PM

it's in the territory of don't really know what will happen and is just an educated guess. Guess it really depends on the severity of the failure.
dougdoug
Joined: Nov 2018
Posts: 124

dougdoug
Joined: Nov 2018
Posts: 124

Grand Valley &; Trans Canada will help
7/2/2020 at 7:14 PM

One thing to consider would be the grand valley and trans Canada acts as a choke point and will help throttle the flow of water coming into Brandon. I would be hopeful that as long the grand valley trans Canada stays intact I would be hopeful that our dikes in Brandon wont be breached. Our dikes do have the ability to be raised a few feet with various types of aqua dams or tiger dams they would however fail the moment a tree or large debris hits it. Our dikes could also be raised a few feet if really needed would take probably a week or so but it would be a organizing nightmare and it would only be temporary as the dirt would need to be removed after.
Trevor B

Joined: Apr 2005
Posts: 8881

Trevor B
Joined: Apr 2005
Posts: 8881

The very
7/2/2020 at 7:28 PM

dougdoug said "One thing to consider would be the grand valley and trans Canada acts as a choke point and will help throttle the flow of water coming into Brandon. I would be hopeful that as long the grand valley trans Canada stays intact I would be hopeful that our dikes in Brandon wont be breached. Our dikes do have the ability to be raised a few feet with various types of aqua dams or tiger dams they would however fail the moment a tree or large debris hits it. Our dikes could also be raised a few feet if really needed would take probably a week or so but it would be a organizing nightmare and it would only be temporary as the dirt would need to be removed after. "
windy nature of the Little Saskatchewan will likely also slow down the water. The water will likely go into fields instead of taking the many 90 and 180 degree turns.
Abbysmum
Joined: Mar 2009
Posts: 5039

Abbysmum
Joined: Mar 2009
Posts: 5039

maybe
7/2/2020 at 7:34 PM

Trevor B said "windy nature of the Little Saskatchewan will likely also slow down the water. The water will likely go into fields instead of taking the many 90 and 180 degree turns. "
That's a good point. It's also possible it will try to cut itself a new channel due to sheer volume of water. I wonder if that's going to be a possibility at the choke points mentioned above if there's a surge in water.

Thanks Adam for splitting it off from the parent thread and reassuring me that I'm not crazy for worrying about this!
Adam

Joined: Mar 2005
Posts: 15663

Adam
Joined: Mar 2005
Posts: 15663

Dam
7/2/2020 at 8:21 PM

Cross posting this with the main flood facts thread...
Image released today courtesy Manitoba government of the dam near Rivers at Lake Wahtopanah...
Trevor B

Joined: Apr 2005
Posts: 8881

Trevor B
Joined: Apr 2005
Posts: 8881

It's
7/2/2020 at 8:24 PM

really like a big heavy truck going 100 km/h making a sharp 90 or 180 degree turn staying on the road. Momentum will make it want to continue in a straight line. Then where the Little Saskatchewan meets the Assiniboine will slow it down as the 2 rivers meet. Brandon will still see a rise no doubt, but shouldn't be a full impact. Then this will all depend on the method and severity of dam failure. This is still all hypothetical since it has never happened before and hope it never happens.
Mr. Smith
Joined: Jul 2010
Posts: 104

Mr. Smith
Joined: Jul 2010
Posts: 104

Rivers Dam Failure
7/2/2020 at 9:11 PM

I happened to pose this question to the Brandon Emergency Response Team email. It was responded to by Brian Kayes. Here is my question and his response. I have blanked out my address.

"Good afternoon. I live at XXXXXX, just south of Stickney Avenue (outside of zone given evacuation warnings). I am wondering if the city or the province has any idea of what would happen to us given the worst case scenario of the dam at Rivers failing?

JM"

The response:
"Greetings:

The evacuation warnings were given to those properties most likely to be directly impacted by a flash flood on the Assiniboine River caused by a huge volume of water coming down the Little Saskatchewan River. Provincial flood forecasters have calculated that the water level in Brandon would be below the top of our dikes so in order for the City of Brandon to be impacted there would have to a failure of our dike that would allow water into residential areas. While the possibility of this happening is very small, we want people to be prepared, just in case. If you are outside of the notification area, our Engineering Department has determined that your property is above the anticipated flood level.

Brian Kayes "

I interpret this to mean that our current dike structures could support any water coming downstream if the Rivers Dam were to fail.
This is Me
Joined: Feb 2008
Posts: 366

This is Me
Joined: Feb 2008
Posts: 366

Crazy question maybe not
7/3/2020 at 7:32 AM

Is there anyway to divert some of the water before it gets to the damn? If you could do that , then it is less pressure on it.
Adam

Joined: Mar 2005
Posts: 15663

Adam
Joined: Mar 2005
Posts: 15663

Rivers dam
7/3/2020 at 1:16 PM

Cross-posting with the main facts thread.

Via Sun story below, the level at Rivers has dropped slightly but there continues to be concern over the dam structure.

On a question about what would happen to Brandon in the event of a failure, infrastructure minister Ron Schuler said "At this moment, we do not view there being any significant issue"

also saying:

"It’s not that we feel the structure is going to collapse imminently. Hardly. It’s just that we don’t have confidence in the structure as it stands and out of an abundance of caution we are suggesting that people evacuate."

The full story is at:
https://www.brandonsun.com/local/water-level-lower-but-threat-remains-571611702.html
Adam

Joined: Mar 2005
Posts: 15663

Adam
Joined: Mar 2005
Posts: 15663

Rivers dam
7/3/2020 at 5:34 PM

The City tweet below speaks to the flash flooding scenario from a dam failure...worst-case scenario said to be levels comparable to the flood of 2011 (below the height of the dike):
Our team continues to monitor the potential for flash flooding in the Assiniboine River Valley should the Rivers Dam fail. In such an event, worst-case peak levels in #BdnMb would be similar to those seen in the spring of 2011 - which would be below top of our dike system. (2/3)
— City of Brandon (@CityBrandon) July 3, 2020
Adam

Joined: Mar 2005
Posts: 15663

Adam
Joined: Mar 2005
Posts: 15663

Dam scenarios
7/3/2020 at 11:48 PM

From the link below via Economic Development Brandon/Brandon Chamber, in the event of a dam failure at Rivers there would be approximately four hours notice for Brandon. In dam failure projections, have water level at 2-3 feet below Brandon’s dike height. If projections are accurate and dike does what it’s built to do, water would come and go in less than 12 hours:
http://brandonchamberofcommerce.chambermaster.com/news/details/elevated-risk-of-flooding-update-for-businesses-located-in-the-flats
Separate note, see info below via the Sun of a test emergency alert on Friday that had been causing quite a bit of added concern:
An emergency alert sent out by the province through The Weather Network at 3:29 p.m. for the RM of Cornwallis says that the Rivers dam could fail within 24 hours. However, we have confirmed with a provincial spokesperson that the alert was a test message — dam's status unchanged.
— The Brandon Sun (@thebrandonsun) July 3, 2020