Flooding in NB and Quebec. Is it time to stop building on flood plains?

[Admiral Beez]

I lived in Fredericton from 2004 to 2007 and every year the Saint John River flooded the downtown and flooded out houses down river towards CFB Gagetown. And every year I wondered, why are they allowed to build houses in these flood zones? And if they are, why are building permits demanding flood resistant housing?

 

[lenaitch]

It would instructive to see the relative timelines of building dams upriver of the city vs. the development of the now-flooding areas. Did the dams make the flooding better or worse? Fredericton is an old city but I don't know it well enough to know if the areas are similarly old or newer. It (and areas on the lower Ottawa) certainly does seem repetitive. One more reason why I would never want to be on water; I don't want to pay for it and in many cases is getting unpredictable (or predictably unsettling). I would rather be on high ground with a nice view of water.

Southern Ontario learned its lesson from Hurricane Hazel. Hopefully we don't forget it, especially with the weakening of the conservation authority funding.

 

[AlvinofDiaspar]

I lived in Fredericton from 2004 to 2007 and every year the Saint John River flooded the downtown and flooded out houses down river towards CFB Gagetown. And every year I wondered, why are they allowed to build houses in these flood zones? And if they are, why are building permits demanding flood resistant housing?

Someone will have to buy the properties on the floodplain - but that's never a popular, cheap decision if it is at all possible (see Calgary, for example).

AoD

 

[Admiral Beez]

Someone will have to buy the properties on the floodplain - but that's never a popular, cheap decision if it is at all possible (see Calgary, for example).

AoD

Refuse flood insurance unless homes are flood resistant or moved. I recall noting as I drove past the flooded residences that a lot of them had wheels underneath.

 

[the lemur]

Or is it time to start building flood barriers and generally doing water management?

 

[steveintoronto]

Southern Ontario learned its lesson from Hurricane Hazel.

Actually not, although you're right, they *should have* and did to an extent for *river flooding*. I'm shocked by how unprepared Ontario is according to experts and dialog link below.

Refuse flood insurance unless homes are flood resistant or moved. I recall noting as I drove past the flooded residences that a lot of them had wheels underneath.

See:

Rochester's most popular newspaper carries these stories:
https://www.democratandchronicle.co...lster-shoreline-water-levels-rise/3642918002/
https://www.democratandchronicle.co...sing-fast-sandbagging-intensifies/3571841002/

 

[lenaitch]

Actually not, although you're right, they *should have* and did to an extent for *river flooding*. I'm shocked by how unprepared Ontario is according to experts and dialog link below.


See:

Rochester's most popular newspaper carries these stories:
https://www.democratandchronicle.co...lster-shoreline-water-levels-rise/3642918002/
https://www.democratandchronicle.co...sing-fast-sandbagging-intensifies/3571841002/

Fair point. I was more thinking of the watershed conservation authorities (now under threat) and things like flow control structures, such as G. Ross Lord dam vs. open run rivercourses. There was building code/bylaw changes after the loss of life and property in areas like the lower Humber River.

No potential solution is without issues. The flooding is a massive seasonal flow that raises levels in the order of meters. Lac Coulonge (near Pembroke, about halfway along the river) it is up about 3 meters. You could build flood barriers but they would have to be virtually be continuous dikes. Water management means holding it back, which means large-scale dam modifications and essentially sacrificing upstream communities and land owners.
I heard the mayor of Muskoka Lakes Twp. on the news saying 'they' have to do better water level management. It's a crap shoot. If they draw the lakes down too far in the Fall then don't get the anticipated Spring runoff, cottagers howl at the low levels.
There is also the issue of energy production. Lower water levels impact generation.
Some have mentioned a diversion aka the Winnipeg Floodway ('Duff's Ditch'). I don't even know if it would be technically feasible but I know it would be massively costly, and while it might save one area, there is always a downstream.
The Mississippi waterway is highly managed and they had built several 'water retention areas'; basically, dry ponds. Over the years there was pressure for recreational areas so many of these areas were flooded. When they had the their massive flood a few years ago, these retention areas couldn't do their job. I don't know enough about the topography of, say, the Ottawa valley to speculate whether something similar would be possible, let alone affordable.

 

[W. K. Lis]

Maybe include stilts for any new or renovated buildings in the floodplains.

From link.

From link.

 

[steveintoronto]

You could build flood barriers but they would have to be virtually be continuous dikes.

Some have mentioned a diversion aka the Winnipeg Floodway ('Duff's Ditch'). I don't even know if it would be technically feasible but I know it would be massively costly, and while it might save one area, there is always a downstream.

It's a diversion of a quantifiable problem, but on an even larger scale, even the Dutch, the masters of dikes, realize it's a solution with limited utility. We're going to be hearing a lot more on this subject in the next while.

Maybe include stilts for any new or renovated buildings in the floodplains.

The solution? Don't build on a floodplain, or even close to one. What you posit is a solution to existing homes to get them above the flood level, but what about all the essential services and ability to function as an island in inclement weather?

 

[jje1000]

Flood control like dikes is unsightly and only serve to create a system that goes against the natural river condition, possibly even compounding problems elsewhere (as the Mississipi dikes have shown).

Rather, I think houses should be able to ride out flooding without significant damage, like the stilt houses above. In fact, the stilt houses are really overkill- just a couple of feet higher should probably suffice for most houses in affected areas in Canada. This can be done over time through municipal and provincial laws, and selective insurance coverage. The overall goal would be to minimize damage, not avert it completely.

The other option is to move people away from floodplains through buyouts, expropriations and limiting payouts (like what Quebec is doing). Toronto did that after Hurricane Hazel, thankfully enough. This option is tougher to do, considering the value North Americans place on their properties.

 

[W. K. Lis]

Flood control like dikes is unsightly and only serve to create a system that goes against the natural river condition, possibly even compounding problems elsewhere (as the Mississipi dikes have shown).

Rather, I think houses should be able to ride out flooding without significant damage, like the stilt houses above. In fact, the stilt houses are really overkill- just a couple of feet higher should probably suffice for most houses in affected areas in Canada. This can be done over time through municipal and provincial laws, and selective insurance coverage. The overall goal would be to minimize damage, not avert it completely.

The other option is to move people away from floodplains through buyouts, expropriations and limiting payouts (like what Quebec is doing). Toronto did that after Hurricane Hazel, thankfully enough. This option is tougher to do, considering the value North Americans place on their properties.

Basically, put houses on artificial hills.

 

[lenaitch]

Flood control like dikes is unsightly and only serve to create a system that goes against the natural river condition, possibly even compounding problems elsewhere (as the Mississipi dikes have shown).

Rather, I think houses should be able to ride out flooding without significant damage, like the stilt houses above. In fact, the stilt houses are really overkill- just a couple of feet higher should probably suffice for most houses in affected areas in Canada. This can be done over time through municipal and provincial laws, and selective insurance coverage. The overall goal would be to minimize damage, not avert it completely.

The other option is to move people away from floodplains through buyouts, expropriations and limiting payouts (like what Quebec is doing). Toronto did that after Hurricane Hazel, thankfully enough. This option is tougher to do, considering the value North Americans place on their properties.

It will be interesting to see how much uptake there is on the Quebec offer. From what I understand, it is capped at $200k which would still leave many seriously behind the ball in terms of paying off any remaining mortgage, plus finding new digs. Many are in an untenable position but may elect to stay living in something they still owe on.

The stilt houses pictured are probably from the US south. Still, the Ottawa has risen a couple of meters so any adjustment would have to account for that. The other issue is water supply and septic contamination.

The portion of the affected residents that are completely screwed are those who are cottagers. It's not their principle residence so are eligible for nothing. Some may be inclined to say 'boo-hoo' but it's still a multi $K loss and possibly a defaulted mortgage.

Insurance carriers will always provide selective coverage and the selections will favour them not the client. It is my understanding that few, if any, of the folks in these areas would have overland flooding coverage, yet they still live there (and builders still build there and municipalities still approve there).

 

[Northern Light]

I don't know enough about the topography of, say, the Ottawa valley to speculate whether something similar would be possible, let alone affordable.

Most of this area is Shield. Really tough rock that you can not just 'dig' through. A diversion system or the like would be hideously expensive. Literally cheaper to buy out the most affected properties, modify area building codes for peripheral properties, and institute a small number of infrastructure projects for selects spaces (berms, raised roads/bridges)

 

[Northern Light]

Rather, I think houses should be able to ride out flooding without significant damage, like the stilt houses above. In fact, the stilt houses are really overkill- just a couple of feet higher should probably suffice for most houses in affected areas in Canada. This can be done over time through municipal and provincial laws, and selective insurance coverage. The overall goal would be to minimize damage, not avert it completely.

Not practical in most situations. You may save the house, but you have sewer/septic/water intake; hydro polls, cable/fibre, roads, and important public buildings like schools/fire halls and hospitals.

To make every one of these flood-resistant across a large area is going to easily crest 10B and possibly a good deal more.

Flood resistance is practical only on a limited scale, typically in peripheral to flood risk areas, where your protecting against the 100-year plus storm with just a bit of extra caution.

The only other reason to use this strategy is for a very limited area, deemed high value/essential to remain in its current location, but that's a pretty high bar to meet.

The solution? Don't build on a floodplain, or even close to one. What you posit is a solution to existing homes to get them above the flood level, but what about all the essential services and ability to function as an island in inclement weather?

Entirely correct.

Now the asterisk is how we define the floodplain? Do we use the 25-year storm?, The 100-year storm? The 200-year storm? etc.

I typically think the 100-year storm is the correct bar; but we need both updated flood maps that correctly show flood risks as they are; and reasonable projections of where the risk will be 100 years out, given climate change.

 

[steveintoronto]

The other issue is water supply and septic contamination.

This is a far greater point than many realize.

Now the asterisk is how we define the floodplain?

And beyond that, the *type and cause of flooding*. Windsor, for instance, was totally a case of inadequate sewer capacity and freak (? Changing pattern?) rainfall. And river and lake flooding are also separate phenomena.