Flooding is a natural phenomenon that recharges wetlands and enriches flood plains. However, when these areas are inhabited or developed, they can pose a risk to populations and infrastructure. In the Rivière du Nord watershed, several municipalities are affected, particularly during spring floods. 

Flooding in at-risk areas

The territory has areas particularly vulnerable to flooding, especially in the southern lowlands. Spring floods, intense rainfall, and rapid urbanization increase the frequency and severity of overflows, affecting residents, infrastructure, and natural environments.

Initiatives such as INFO-Crue and the mapping of flood zones allow for better territorial planning and reduced risks.

Did you know?

Nearly 10% of the watershed territory is exposed to a flood risk according to the most recent flood zone maps from the MELCCFP (ministère de l’Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs).

Location within the territory

The municipalities most vulnerable to flooding are mainly located in the St. Lawrence Lowlands, in the southern part of the Integrated Water Management Zone (ZGIE), where population density is high and several watercourses flow into the Rivière du Nord. In these flat areas, water flows more slowly, which can cause rivers to swell and overflow.

Areas particularly at risk:

  • Saint-Jérôme, Mirabel (Saint-Canut), and Lachute: frequent spring floods affecting downtown areas and agricultural lands. The dam at the former Woodbridge plant in Saint-Jérôme helps limit impacts.
  • Saint-André-d’Argenteuil: residential areas along the Ottawa River or at its confluence with the Rivière du Nord
  • Northern part of the territory (Canadian Shield): areas where rivers converge (e.g., Sainte-Adèle: Rivière du Nord and Doncaster) and areas with meanders (e.g., Val-Morin)

Consult the interactive portrait and browse through the Physical Characteristics (Caractéristiques physiques) tab and, in the Hydrography (Hydrographie) layer, select Ice Jam Flood Events (Évènements d’inondation par embacles) and Open Water Flood Events (Évènements d’inondation en eau libre) to view the areas affected by this issue.

Main causes

Floods result from a combination of natural and human forces. Understanding these factors is essential for better territorial planning, protecting natural environments, and securing communities.

  • Urbanization in flood-prone areas
  • Soil artificialization and impermeabilization (parking lots, roads)
  • Channelization or straightening of watercourses
  • Loss of wetlands that act as natural buffers

  • watershed topography and narrow valleys
  • High variability in annual precipitation
  • Presence of clayey soils with low permeability that promote runoff

Climate change

According to « Les défis et perspectives pour la région des Laurentides » (Ouranos, 2020), watercourse flow rates within the ZGIE du Nord might evolve in the coming decades.

More frequent freeze-thaw events are expected, which could increase the average winter flow rates, while warmer temperatures would promote more liquid precipitation in the winter. Heavy rainfall is likely to become more frequent and intense, increasing runoff, wastewater overflows, and water levels. Although spring rains may decrease in the southern Laurentians, flooding due to runoff could occur more often in the summer and autumn, associated with the increase in intense rainfall events.

Consequences 

Flooding has environmental, social and economic impacts:

Environmental

  • Soil erosion and degradation: Flooding exacerbates erosion,soil leaching, and it can destroy certain riparian habitats.
  • Impact on water quality: Influx of contaminants and pollutants (sewer overflows, chemical or agricultural waste), debris, and garbage into watercourses
  • Ecological role and disruptions: Flooding participates in the natural dynamics of ecosystems (recharge of wetlands, cleaning of watercourse beds), but exceptional floods can harm certain habitats.

Social

  • Impacts on physical and psychological health: diseases, injuries, hypothermia, respiratory risks, stress, anxiety, trauma, long-term feeling of insecurity, etc.
  • Damage to public safety: disruptions to essential services (drinking water, electricity, transportation, communications) and delays in emergency response (paramedics, firefighters, police)

Economic

For institutions (governments and municipalities):

  • Direct and indirect costs: repairs, emergency measures, and loss of income related to property depreciation and the decline in tourism
  • Investments in flood prevention and management: dikes, drainage, flood-proofing works, and risk management policies

For disaster victims:

  • Property damage and financial losses: buildings, property, harvests, income, and interruptions to activities
  • Costs and indirect impacts: temporary accommodations, increased insurance costs, physical and psychological health impacts

Prioritized issues

Flooding of areas with issues is among the six priority problems identified in the 2024-2034 Water Master Plan. For more information, consult the diagnostic fact sheets. These present the portrait and diagnosis of the issues related to water resources in our territory.

Overconsumption of water resources

Poor water quality

Competing water uses

Degradation and/or destruction of wetlands and aquatic environments

Shoreline erosion

Flooding in at-risk areas

Learn more about the ZGIE du Nord, its strategic planning, and the actions planned to ensure sustainable water management.

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An innovative solution

To meet the needs of water stakeholders, the OBV de la rivière du Nord has developed VigieNord, a citizen science platform that makes it easy to report and geolocate water-related issues. The tool makes a tangible contribution to:

Promote better sharing of field observations among water stakeholders

Identify opportunities for action in the region