flood maps – The Map Room

The CBC on Inaccessible Flood Maps

Jonathan Crowe — Wed, 27 Sep 2023 18:19:53 +0000

As the CBC’s evening news program The National reports, flood maps can be incredibly hard to find, with even municipal maps requiring an NDA to view in some cases. Now this story focuses on Halifax, Nova Scotia in the wake of flash flooding this summer; the situation elsewhere in Canada may be quite different (Quebec’s flood maps, for example, are available online, though only in French).

Quebec’s Updated Flood Maps Prove Controversial

Jonathan Crowe — Thu, 01 Aug 2019 17:51:49 +0000

Government of Quebec (screenshot)

In the wake of serious and devastating spring flooding in 2017 and 2019, the Quebec government issued proposed flood zone maps that marked areas where rebuilding and new construction would be put on hold. There was immediate pushback: as CBC News reported last month, the maps included substantial areas of small towns (such as, in my neck of the woods, the villages of Fort-Coulonge and Campbell’s Bay), or, in the case of Gatineau, areas that were not flooded in either 2017 or 2019 as well as major new developments. The mayor of Vaudreuil-Dorion suggested that the mapmakers forgot to correct for cloud cover. In the end, new maps were issued that removed substantial areas of Montreal from the flood zone, among other areas: some 20 percent of the 120,000 homes affected by the first set of maps were removed from the revised maps.

Previously: Quebec Flood Maps.

Quebec Flood Maps

Jonathan Crowe — Tue, 21 May 2019 13:41:42 +0000

In my neck of the woods we’ve been dealing with some pretty severe spring flooding. And as is often the case, existing flood maps are not up to handling the new normal imposed by climate change. Sainte-Marthe-sur-le-Lac, a community near Montreal, was hit hard by flooding this spring, but only two of the 800 flooded homes were in current maps’ flood zones. This isn’t an new situation; we had similar floods in 2017. Back then, CBC News reported that Montreal-area flood maps’ 20- and 100-year floodplains were exceeded by the then-current flood extent.

Fast forward to this spring. The flood maps for Montreal-area municipalities have been updated—they’re now based on LIDAR data from 2014 onward—but have not yet made public: they’ve yet to be approved by the municipalities or adopted by the province; nonetheless they’ve been put to use during the recent emergency. On the new maps, some 1,500 homes in Sainte-Marthe are part of the flood zone.

FEMA Flood Maps Don’t Account for Future Sea Level Rise

Jonathan Crowe — Mon, 28 Aug 2017 16:28:23 +0000

NPR last month, reporting on a problem with FEMA’s flood insurance maps: they’re not keeping up with reality. “FEMA’s insurance maps are based on past patterns of flooding. Future sea level rise—which is expected to create new, bigger flood zones—is not factored in. So some communities are doing the mapping themselves. Like Annapolis, the state capital of Maryland.” [Leventhal]

Alberta Flood Maps

Jonathan Crowe — Fri, 21 Jun 2013 13:26:56 +0000

This is a list of maps related to the flooding in southern Alberta (Calgary, Canmore, Bragg Creek, High River, Okotoks, etc.). This list will be added to as needed. Feel free to contribute additional links in the comments.

Evacuation zone maps from the City of Calgary, in PDF format.
For a wider view, an interactive map of Calgary evacuation zones from CBC News.
A map of flooding zones across Alberta.
A flood report map from the Calgary Herald, using reader submissions.
A mobile site for crowdmapping flood reports (thanks, Matt).

Update, 10:15 PM:

The Alberta provincial government’s Flood Hazard Map Application; requires Flash (via Colby Cosh).

Update, June 22 at 8:25 AM:

Google’s Alberta Flooding Crisis Map.