Canadian Flooding

[miningman]

Unless one defines a 104 year old structure that was nominally designed for a 1 in 1000 year flood event to be poorly designed, then this is not specifically an engineering failure. However the same area flooded significantly in 2017. In western Canada in 2013 , Calgary was flooded to the tune of $5 billion.

As engineers one of the first things we were taught was " Dont build or buy in a flood plain". I am quite prepared to accept that climate change is contributing to the apparent increasing frequency and severity of these floods etc. And of course the damage and devastation here is insignificant compared to the recent hurricane damages in the SW USA states over the last 20 years or so.

But I cant help but ask , what are we as citizens and / or government doing wrong here ?? Should we as voters and taxpayers be demanding more effective and timely spending by governments??? Should we as engineers be trying to spread the word more effectively to the general public??? I find some of the comments in the press to be incredible. I dont think the insurance industry is likely to be much help to 90% of those affected.

https://montreal.ctvnews.ca/dam-at-...er-grenville-sur-la-rouge-evacuated-1.4395306

 

[oldestguy]

That video shows a stable dam, no failings. No emergency spillway there apparently, but she is holding well n spite of that.. As to engineers and possible changing, how about the folks in government with the constant clamor for more free stuff and no payment needed. Change politics and maybe change disasters. One thought; now and then an engineer runs for a position in government, but few.

 

[itsmoked]

I'm amazed that dam hasn't left the area. That is the worst over-topping I've ever seen. How are the ends not eroding away.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[miningman]

Additional interesting reading, especially given that water levels in the general are are not expected to peak for at least 48 hours. Looks like the flood of 2019 will be much worse than that of 2017.

https://montrealgazette.com/news/lo...-in-spotlight-again-after-forced-evacuations.

The army has already been called in to assist in both Ottawa and Montreal....... population probably about 3 million combined. I certainly don't expect any non Canadians to get too excited about this, but do you think your local authorities have given adequate attention to your local hydrology?? As engineers, I am sure most of us understand the concept of one in 100 or one in 300 year flooding but I can already hear the complaints of the local population starting around mid May.

Only 12 months ago did I have to buy a new house in an area I was not intimately familiar with. It took some effort but I was able to identify on line maps of the local one in a hundred year flood plains. Doesn't guarantee me anything ,but I was able to avoid the areas that are at more risk than the area I ultimately chose.

 

[Sparweb]

Houses built on floodplains does have an effect on politics, though not necessarily the safest one.
Developers buy land, build houses, then sell them. They can buy cheap land in some areas exposed to flood risk, and get building permits when they have prepared "adequate" flood mitigation measures. The value of "adequate" is proving to vary from city to city, and it helps to have a few local politicians to phone up when the decision is being made.
Another consequence of building "adequate" flood barriers is that the developer may not have to consider the upstream or downstream effects of their barriers.
If you build walls all along a river bank for miles, you can prevent floods there, but it's more likely to flood upstream instead. Somebody else's problem.

Referring to Calgary's 2013 floods, the new expanded flood mitigation plans west of the city are a major headache for all levels of politicians from Springbank and Bragg Creek. The new provincial government will not have an easy time taking that plan to the finish line. The city of High River is also still dealing with unfinished business from 2013, but I realize now that I haven't kept track of what they're doing.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[saikee119]

To me flooding is man-make.

To design a drainage system to convey rainwater using open channels or rivers only two parameters are vital. It is just like passing electrical current through a conductor in that we need area and potential in the design.

For hydraulics the potential is the gradient and the required area is the cross section of the channel or river to convey the water.

When a river or channel has been design years ago the same river or channel may not have the original properties or characteristics today. Typically the river bed has risen due to deposits over the year. Therefor a channel or river must be dredged regularly just to maintain its original design capacity.

What happen is more land has been developed and covered by buildings, roads and pavements reducing the natural absorption leaving more excess water to be discharged while the capacity of the water conveying system has been gradually reduced by silting. Nowadays whenever there is a heavy rain flooding is a commonly accepted consequence. Municipal engineers, drainage experts, flood routing professionals and hydraulic engineers are gradually phased out leaving the politicians to blame the climate changes.

I had been working in an office fronting the River Tyne in UK, size comparable to the one passing Calgary, for over 30 years and had never seen it dredged. Over the years I noticed many drainage outlets were blocked one after the other. Whenever a heavy rain storm occurs a few of these buried outlets were pressurized so much that some suddenly blew through like canons shooting mud out like a war zone within the river.

In one recent flooding we had the water flooding on the road just 2m from the edge to the river where the water level was at least 3m below.

If the river were dredged at downstream the gradient is increased and water can traveled faster and not built up to the flood level. Dredging the river bed also increase the cross section for carrying water so the throughput can be increased.

If a city wants to reduce flooding it should always employ knowledgeable engineers to make sure the drainage system capacity is maintained and expanded to suit the city's development. However it makes economic sense to employ less city engineers and blame the climate changes.

 

[GeoEnvGuy]

I think what we are doing wrong is trying to cut costs on operations and maintenance while maximize profit.

Link provided says they hit the 1000 year mark for high water. Maybe hydro Quebec shouldn't store water at such high levels before a flood to maximize profit.

The other thing we are doing wrong is having 4year politicians claiming lower taxes with better service.

I don't work in Quebec so maybe they have more information available but looking at the Canadian river monitoring stations map, Quebec has significantly less coverage than any other province. I know in Ontario the provincial agency responsible for River monitoring has been cut to the bare minimum and the actual calibration and maintenance work is contracted to the lowest bidder.

I don't think any politician will campaign for more flood upgrades or monitoring and projections. Also the public doesn't want to see or pay for more construction of dykes or dredging.

I have also observed the opinion that old structures were built with the best engineering at the time and has performed well thus far, so it must be all good and the inspection box is checked and signed off as safe. In my opinion anything built before the 1970's is probably not designed to current engineering standards. When this is pointed out to owners they don't want to redo the engineering to determine how far off they are and what is required to meet current standards. Just like dykes designed by flood studies conducted in the 70's.

 

[miningman]

Another recent flood, this time only $3 billion...... which is surprisingly low given the apparent areal extent. Eventually society is going to have to choose whether it wants the clean , cheap hydroelectricity than dams can provide ,
or whether the main purpose of the dam is flood control downstream of the dam. Perhaps in previous years hoping to achieve
both was realistic, but present climatic conditions do seem to be be eliminating that option.

And once again aging, neglected infrastructure seems to be playing its part

https://www.engineering.com/BIM/Art...e-Missouri-Flood.aspx?utm_source=relart-etips

 

[itsmoked]

Are you saying the damn DID leave??

Keith Cress
kcress -

http://www.flaminsystems.com