Rainwater and flood zones in Mascouche
Updated September 28, 2026
According to the Commission de toponymie, Mascouche's territory is very flat. In several sectors, rain water from the streets drains through ditches and culverts rather than underground pipes. The town's resilience plan includes a lidar survey of these ditches to help regrade them.
The sewer network, the town notes, is designed for ordinary rain: during torrential rain, the volume of water exceeds its capacity and causes overflows. It says that in recent events it received a month's worth of rain in a few hours. After Debby, Mascouche adopted a first climate resilience plan, focused on water, for the years 2026 to 2030.
Heavy rain events
What public sources report about heavy rain in Mascouche, at sector level.
According to the town's resilience plan, the remnants of Debby dropped 171 mm of rain in a few hours, a 100-year rainfall according to Environment and Climate Change Canada. The plan reports flooded basements and displaced families. According to the mayor, only a small share of the flooded owners had been hit by the Mascouche River overflowing, the only ones Québec could compensate. For the others, the sources do not say how much came from runoff and how much from sewer backup.
Sources: Ville de Mascouche, plan de résilience climatique 2026 (PDF) · La Presse, 22 août 2024
That evening, radar estimates gave 70 to 90 mm of rain over the Les Moulins RCM. In Mascouche, backups were seen in several places, in the streets and in private homes, and firefighters went to houses with flooded basements. The source does not say where the water came from.
Sources: La Revue, 14 septembre 2022
Good to know in Mascouche
- The town has ditches in several sectors and names what hinders their flow: no outlet, wrong levels or a reversed slope, flat streets, and private piping that is poorly designed or installed without a permit. (Ville de Mascouche, règlements, fossés et ponceaux)
- By-law 1229 forbids any owner to pipe a street ditch, public or private. A French-drain outlet may discharge into it according to a set plan, provided the drain has a backwater valve. (Ville de Mascouche, règlement 1229 sur les fossés et ponceaux (PDF))
- By-law 729 requires a backwater valve on every building drain, both sanitary and storm. It also requires gutter water to discharge on the surface, at least 150 cm from the building. (Ville de Mascouche, règlement 729 sur les branchements (PDF))
- If a garage is lower than the street or sidewalk, the rules require a small raised lip between the street and the driveway so street water does not run in. The town recommends a working catch basin at the bottom of any reverse-slope driveway or basement stairwell. (Ville de Mascouche, plan de résilience climatique)
- The Subvention pour résilience des pluies abondantes refunds part of the cost of a preventive inspection, a backwater valve, a sump pump or a backup battery, up to a cap per address. It is offered in 2026 on a first-come, first-served basis. (Ville de Mascouche, programmes et subventions)
- According to the town's plan, Mascouche has about 12 days a year with more than 20 mm of rain, and up to 49 mm in 24 h on the wettest days. By 2050, the plan expects 15 or 16 such days and a maximum that could reach 59 mm. (Ville de Mascouche, plan de résilience climatique 2026 (PDF))
Rivers and lakes: what the check does not cover
Waterways in Mascouche: Mascouche River, Des Seizes stream, Gariepy-Gagnon stream and Cabane-Ronde stream.
The Mascouche River winds through the town in many meanders and splits it in two. In early April 2017, after several days of heavy rain, it overflowed into a riverside sector, and some houses were evacuated. During Debby, in August 2024, it also overflowed. The town tracks its level in real time with a flowmeter and keeps sandbags to protect some sectors at risk.
Sources: Commission de toponymie du Québec, fiche Mascouche · Radio-Canada, avril 2017 · La Presse, 22 août 2024 · Ville de Mascouche, FAQ sur les inondations
The check is about the rain that falls on the area and runs off over the ground. River and lake flooding is not part of it: in the simulation, a nearby river or lake holds no water. For a waterfront property, the official map comes first.
What we know about the ground in Mascouche
These values come from the public sources the check uses. They describe the area, not an address.
| 1 m terrain model (NRCan HRDEM) | Available across the whole area |
|---|---|
| Nearest rainfall gauge (ECCC) | L'Assomption, 14 km awayLocal rainfall statistics. |
| Municipal street drains | Not modelled: with no open municipal inventory, the check's depths are an upper bound wherever a working network would carry water away |
| Mapped culverted road crossings | 58Culvert lines mapped in OpenStreetMap (ODbL). |
Data Source: Environment and Climate Change Canada, Short Duration Rainfall Intensity-Duration-Frequency Data, used under the ECCC Data Servers End-use Licence.
Area analysed: adapted from Statistics Canada, Census Subdivision Boundary File (cartographic), 2021 Census. This does not constitute an endorsement by Statistics Canada of this product.
Probed on September 28, 2026.
The official map and what it does not show
Québec's flood-zone maps cover rivers and lakes. They do not show rain water collecting on a lot, in a low spot or at the bottom of a sloping driveway. Check the official map for the address first: it is what says whether a property is in a flood zone.
- Mascouche flood-zone map (Annexe C, sent on request, in French)
- Check a property on the Government of Québec site (in French)
FloodVerity does not reproduce these maps and does not state any regulatory zone.
Check an address in Mascouche for $39
We drop a 100-year, one-hour design storm on the ground around the property, route the runoff, and email you the peak depth of rain water at the address, where it collects, a map and a 3D view.
What the check does not do
- This check models rain falling on the area itself and running off over the terrain. Water arriving from a river or lake, sewer backup, ice jams and storm surge are not modelled.
- The pipe network itself, roof and lot drainage, and sewer backup are not modelled.
- Where the structures inventory records a culverted road crossing, it is lowered to a partly blocked opening rather than solved hydraulically.
- It does not replay the storms described on this page: it applies a 100-year, one-hour design storm.
- It is a screening: a simulated storm on public terrain data, not a hydraulic study, not an official flood-zone determination, not an insurance opinion.
Notaries and brokers in Mascouche
We run the same check over a list of addresses and deliver a spreadsheet ranking them by the modelled rain depth. Priced per address, on quote.
Email [email protected]Other towns and areas
The FloodVerity check is a screening: it applies a design rainstorm to public terrain data and simulates where the rain runs and collects. It is not a hydraulic study or an official flood-zone determination, and it covers neither river and lake flooding nor sewer backup.