Building a flood way for Calgary?

[Acey]

Originally Posted by SebC

Wouldn't being flat make things worse? If you divert water where everything's flat, it goes everywhere. In terrain, it would stay more confined. Like isn't it much easier to build a reservoir in a valley? Am I wrong?

Well the idea is to build a big ditch around Calgary, then block the Bow so it flows into the ditch and meets back up with the Bow downstream of Calgary. But with our funky terrain here... water can't flow uphill. So all you'll do is build a reservoir at the point you were trying to block the river, instead of that water flowing into the ditch you've spent billions digging out. Hence the tunnel, which is indeed tens of billions.

[Acey]

More feasible would be big ass dams for both rivers upstream, but I don't think anyone west of Calgary wants their land turned into a reservoir.

[You Need a Thneed]

Originally Posted by SebC

Wouldn't being flat make things worse? If you divert water where everything's flat, it goes everywhere. In terrain, it would stay more confined. Like isn't it much easier to build a reservoir in a valley? Am I wrong?

The flood way in Winnipeg seems to work fine.

[Slanter]

Couple of things...

The Red River floodway is built to a capacity of 4000 cm3/s. The bow maxed out at what, 1600 cm3/s? So if building a floodway was a possibility in Cagary, it could be much, much smaller. You could probably get away with something that could carry 400 cm3/s and it could avoid the catastrophe that just happened. That's one tenth the volume of the red river floodway. So... maybe with that in mind you could build a longer (or more complicated) floodway without incurring huge costs.

Second thing... The Red River floodway is built to withstand a 1-700 year flood. So those of you saying "well, it doesn't happen that often in Calgary" or, "makes more sense in Winnipeg, because it floods more often"... You're missing the point.

All that said, maybe it is in fact completely impossible from an engineering and/or land acquisition position. I don't know. But since we're having this debate, don't think about building a copy of the red river floodway in Alberta. Think about a much smaller floodway, and it might seem more possible.

[Acey]

Originally Posted by Slanter

The Red River floodway was expanded to a capacity of 4000 cm3/s at a cost of more than half a billion dollars.

I think that's important to note...

Originally Posted by Slanter

Second thing... The Red River floodway is built to withstand a 1-700 year flood. So those of you saying "well, it doesn't happen that often in Calgary" or, "makes more sense in Winnipeg, because it floods more often"... You're missing the point.

I dunno. I still feel like opportunity cost is huge. The Red floodway has paid for itself more than 10x over in damages saved. A Bow floodway might not ever pay for itself.

[flamesfever]

Originally Posted by redforever

To the north of Calgary is the airport...water would have to be channelled far north of such a major transportation facility.

To the south of Calgary is Fish Creek. Do you put water into Fish Creek and expand it, because it can't handle any more water right now? Or do you go further south in which case the canal would have to traverse Fish Creek.

To the west is the Tsui Tina and part of the Elbow flows right throuh that reserve. You would have to enter into negotiations with them. How well do you think those negotiations would go?...in light of the fact that ring road negotiations have been on going for 40 years with no end in sight.

A better solution would be to dredge existing reservoirs and make them deeper with the ability to hold more water...or build more reservoirs and dams upstream.

If nothing is done, all reservoirs will gradually fill up with sediment. From what I understand, most progressive countries have some plans in place for extending the life of reservoirs by dredging. I have not heard of any such plans for our reservoirs in Alberta.

[Free Ben Hur!]

Originally Posted by flamesfever

If nothing is done, all reservoirs will gradually fill up with sediment. From what I understand, most progressive countries have some plans in place for extending the life of reservoirs by dredging. I have not heard of any such plans for our reservoirs in Alberta.

Particularly given that the mean depth of the Glenmore Reservoir is only 6M (20'). You would think that adding capacity through dredging would be a relatively cheap and easy thing to do. Way less than a complete flood way for both the Bow and Elbow. Maybe a combination of a flood way upstream of Bearspaw Dam to divert some flow from to the Elbow then a much higher capacity reservoir?

[Rathji]

I remember there being some discussion about this a while back, maybe in 2005? Am I remembering right?

Either way, obviously nothing was done with it, but it seems like it might be the only viable solution.

[DiracSpike]

Originally Posted by Free Ben Hur!

Particularly given that the mean depth of the Glenmore Reservoir is only 6M (20'). You would think that adding capacity through dredging would be a relatively cheap and easy thing to do. Way less than a complete flood way for both the Bow and Elbow. Maybe a combination of a flood way upstream of Bearspaw Dam to divert some flow from to the Elbow then a much higher capacity reservoir?

I definitely think dredging is the way to go, do it for both rivers and then dredge the living sh-- out of the reservoir. You're right about the depth, most times one can see the bottom even when you're in the middle of it. I live right by it, and I noticed that every spring since 2005 they drain over half of it to prepare for excess capacity. On Thursday morning it was half empty and it filled up to almost capacity in an afternoon.

[Brannigans Law]

I wonder how much it would cost to dredge like that?

[DiracSpike]

Originally Posted by Brannigans Law

I wonder how much it would cost to dredge like that?

Haha probably way too much, but in terms of preventative measures I don't really see what else we could do, between the geography of the river valleys and the native reserve there's no way a floodway could ever be built here.

[ken0042]

Keep in mind a floodway would have to go the long way around the city; through the north side. The shortest route would involve crossing the Elbow; which would be impossible without some sort of tunnel system.

Keep in mind that Winnipeg's system works partly because there are two floodways. One on the Red and the other on the Assiniboine River. Contrary to popular belief; the Red River Floodway doesn't save Winnipeg at the expense of other places. That water would be going there no matter what. However the Assiniboine floodway water never re-joins the river; it goes right north into Lake Manitoba. That can come at the expense of others; as the Assiniboine normally flows into the Red and then into Lake Winnipeg.

The only realistic option I can see is some sort of Elbow diversion; and set it up like the Assiniboine diversion where they can practically drain the Assiniboine river from Portage to Winnipeg; leaving a lot of capacity for the Red to empty into.

[carom]

It's really easy for me to say this from far away, but IMHO it is never a good idea to try and mess with natural waterways or Mother Nature. To me it's is best summed up in the old sports cliche "you can't stop it, you can only hope to contain it." Most large scale waterway engineering I know of just seems like band aid a solution that generally create bigger issues down the road. The idea of fast tracking flow through/around the city all of the time when it is only required very infrequently scares me and I think would have some serious long term consequences.

If it were up to me I would put some bigger berms along the Bow and make sure everyone that lives in a flood plain is prepared by mandating insurance and having really good, frequently updated evac measures in place.

[ranchlandsselling]

Dredging the reservoir might be a good option however I don't think it makes sense for the bow river. I wonder if the reservoir would be a better fishing lake etc if it was dredged all over. I remember 15+ years ago the reservoir seemed more like a lake than it does now. Now when I go there I’m always surprised by the meandering streams and marshland / tributary like area around weaselhead that looks more like a flood plain than a reservoir.

Regarding the bow, at some points in the fall and early spring the flow of the bow looks almost nonexistent. There are parts you could walk across. I can't imagine digging it deeper would do much other than ruin the existing bed. That said, I also don't have the faintest idea how it would work. Would you dig deeper areas where it floods so they’re like pools? Wouldn't those areas just fill up instantly until prior equilibrium was reached at which point it would spill over anyway?

Seems too complicated to even clearly type out what I'm thinking let alone understand river dredging.

[You Need a Thneed]

Dredging the Bow wouldn't work. A good part of the year, it's quite low. Dredging would make the top of water level lower than the current bottom much of the year. All the intakes for water, outfalls, etc may have to be redesigned. The weir would have to redesigned, which would mean that the irrigation canal would have to rebuilt.

[ranchlandsselling]

Originally Posted by You Need a Thneed

Dredging the Bow wouldn't work. A good part of the year, it's quite low. Dredging would make the top of water level lower than the current bottom much of the year. All the intakes for water, outfalls, etc may have to be redesigned. The weir would have to redesigned, which would mean that the irrigation canal would have to rebuilt.

Bolded part is what I was trying to say...

technically we don't have a weir anymore... I think.

[carom]

Technically I think the weir is still there, it has just been made less dangerous by making the drop less severe.

By constructing rock structures below the weir, the water level will be backed up to eliminate the deadly recirculation. The backed-up water will drop over a series of short swifts followed by calm pools.

http://www.harviepassage.ca/about.html

Just to clarify, it is not the cost of the dredging/diversion that scares me, but the ecological consequences. Any anglers or people with more ecological knowledge want to weigh in?

[SebC]

From what I've read, the ecology is messed up anyways because the pebbly bottom of the Bow has been replaced with mud. Having said that, I'm far from an expert so could easily be wrong here.

[redforever]

Originally Posted by SebC

From what I've read, the ecology is messed up anyways because the pebbly bottom of the Bow has been replaced with mud. Having said that, I'm far from an expert so could easily be wrong here.

Both my husband and son are avid fly fishermen.

After 2005, many of the channels in the rivers looked totally different, particularly the Bow and down Livingstone way. They thought fishing was seriously hooped.

But by end of July, when the waters had cleared and settled down, the fish were still there and according to them, fishing has remained the same.

[You Need a Thneed]

Originally Posted by ranchlandsselling

Bolded part is what I was trying to say...

technically we don't have a weir anymore... I think.

Yup, trust me, the weir is still there. It's been modified, and the "rock" "rapids" were built below it.