New flood map makes some owners unhappy
The question of Quebec’s new flood maps goes well beyond Montreal but laps up at its western shores. Many people are not happy with the possible consequences of having their homes and property placed in the conceptual grey zone of a flooding area. Whether the province is being realistic in the face of climate change hardly seems to be mentioned. Here’s the full official map.
The St Lawrence has been unusually high since the spring, and the situation continues downriver.
Update: Beaconsfield has asked to be taken off the map. If the mapping is done correctly, you can no more ask to be removed from a flood map than to be excused winter. A flood map should not be tweaked for political reasons, it should be simple fact that can’t be reasoned with. As the old commercial had it, you can’t fool Mother Nature.
Another update: residents of Pierrefonds-Roxboro talk about how they worry about flooding every spring. I have one piece of advice for them: move to a less worrying location. Putting down roots next to the river – what a nice view! – is foolish, and you can’t expect the government to literally bail you out if experience shows that you’re now living with your feet in the water. Cut your losses and go.
As this CBC piece on climate catastrophe says, “Dikes and levees that protect from flooding can encourage development in flood-prone areas by providing a false sense of security.”
John B 10:50 on 2019-07-06 Permalink
From the CTV: “They could not say if people in zones now considered to be flood-prone would be able to lobby to change the new map zoning.” I hope not! A flood map should be science-based, not lobbying-based.
That said, if the official map is to be believed, the “scientific” method for creating the map may have been to use the spray-paint tool in MS Paint to highlight water. The entire north end of Ile-des-Soeurs is shown as “at risk” even though eyeballing it when I’m there tells me it’s at an elevation of 30 – 50 feet above the river. The tops of the dikes of Verdun, (15-20 feet above the water), are all marked as “at risk” but the rest of Verdun isn’t. If water hits the top of the dikes I think pretty much all of Verdun will be under water.
Kate 12:20 on 2019-07-06 Permalink
Don’t we have topo maps of the whole area, which could be cross-referenced with historical knowledge of water levels to generate a map with pretty solid predictive indicators?
John B 13:11 on 2019-07-06 Permalink
I would expect so, but the maps may not be granular enough to capture features like the height of dikes. I bet Roberto Rocha or Ant6n could put together something pretty accurate over the weekend.
Another interesting fact: according to the Radio-Canada article Sainte-Marthe, which just made it extremely clear to most of Canada why we should not be relying on dikes – has an exemption to allow them to build on flood plains.
Kate 13:15 on 2019-07-06 Permalink
CBC says the mayor of Vaudreuil-Dorion claims that areas obscured by cloud on aerial shots have led to inaccurate maps.
Jesus, people, data! It can’t be that hard to generate maps in a more scientific way than letting some stagiaire play around in MS Paint.
Faiz Imam 15:51 on 2019-07-06 Permalink
I have some experience with flood maps, and I have no idea what these are. Thats not at all how maps used for official public use are designed.
Is this a map of a 20 years flood? a 50 year flood? a 200 year flood?
For insurance purposes(which is the most important thing here) these are crap.
Now, these are rendered in ArcGIS, so obviously they are built on some actual data, but I have no idea what.
Kate 08:19 on 2019-07-07 Permalink
I looked back in the blog archives and found a link to this piece from last fall about plans to remap the flood zones, properly.