In the Rivière du Nord watershed, bank erosion is of particular concern in urbanized and agricultural areas, as well as where watercourses have been straightened or artificially altered. Weakened riparian buffers and increased runoff accelerate soil loss and sediment transport into watercourses.

Human activities such as motorized boating, recreational development, and traffic along the banks also worsen bank erosion. These combined factors have a direct impact on water quality, wildlife habitats, infrastructure, and waterfront property values.

Bank erosion

Data from the iEAU platform reveals a gradual deterioration of water quality from north to south in the Rivière du Nord watershed. Since 2016, monitoring stations have shown a decrease in the bacteriological and physico-chemical quality index (BPQI), reflecting increase concentrations of fecal coliforms, phosphorus, and nitrogen.

Lakes in the territory are also affected: increased turbidity, the presence of cyanobacteria, and nutrient enrichment indicate accelerated aging of the aquatic ecosystems (eutrophication).

Did you know?

A vegetated riparian buffer of at least 10 to 15 meters can retain up to 80% of the sediment transported by runoff and effectively protect banks.

Location within the territory

Some areas within the watershed are more vulnerable to erosion and soil movement. In the Argenteuil Regional County Municipality, the areas located around the Ruisseau des Vases and the Rivière de l’Ouest, in Brownsburg-Chatham, are particularly affected. Sensitive areas can also be observed along the Rivière du Nord, especially in Lachute, Saint-André-d’Argenteuil, and in areas where bank slope are steeper or at the confluence of certain tributaries.

Further north, in the Laurentian Plateau, steep slopes and wooded areas are naturally prone to erosion, a phenomenon exacerbated by human activities and variations in the flow rates of watercourses.

Consult the interactive portrait and browse through the Physical Characteristics (Caractéristiques physiques) tab and, in the Hydrography (Hydrographie) layer, select Landslide and Erosion Events (Évènements de glissement de terrain et d’érosion) to view the areas impacted by this problem.

Main causes

Bank erosion is a natural phenomenon amplified by certain human uses. Within the territory of the Integrated Water Management Zone (ZGIE), it is primarily caused by:

Human factors

  • Poorly planned straightening, dredging, or stabilization of banks.
  • Construction of obstacles or protective structures which modify the sediment balance.
  • Concentration of water flow by linearization or surface impermeabilization.

  • Deforestation and vegetation removal, decreasing the soil’s infiltration capacity.
  • Agriculture, construction, and road infrastructure near banks.
  • Repeated traffic on footpaths, bike paths, or ski trails, leading to soil compaction and runoff.

  • Waves created by recreational boats.
  • Water withdrawals, affecting groundwater stability.
  • Work or maintenance on watercourses without erosion mitigation measures.

  • Loss of natural flood regulation and sediment filtration, increasing bank the vulnerability.

Naturel factors

  • Abrasion and undermining of banks by waves, wind, and coastal ice.
  • Rapid fluctuations in water levels, particularly during floods or freeze-thaw cycles.

  • Erosion on concave banks of meanders where the current velocity is at its highest.
  • Deposits on the convex banks, creating alluvial terraces.

  • Soil composition: sand, silt, clay, and easily transportable organic matter.
  • Bank slope: steep slopes (>30%) are particularly vulnerable to erosion.
  • Landslides, mudslides, gullying, collapses, and scree slopes.

Climate change

Rising temperatures predicted in the Laurentians could reduce snow and ice cover that naturally protect riverbanks. More frequent and intense rain may also increase flooding and alter watercourses flow, promoting bank erosion and its impacts on natural environments and infrastructure.

Consequences 

Bank erosion has environmental, social, and the economic impacts:

Environmental

  • Deterioration of water quality due to the input of sediment and nutrients, promoting the proliferation of algae and aquatic plants
  • Disruption of aquatic and riparian habitats, reducing biodiversity
  • Increased flood risks and accelerated aging of water bodies

Social

  • Loss or degradation of waterfront land and recreational spaces (swimming, boating)
  • Negative perception of water bodies and reduced sense of attachment

Economic

  • Damage to infrastructure (roads, bridges, buildings) and drainage networks
  • Loss of fertile agricultural land and decreased land values of waterfront properties
  • Increased drinking water treatment and infrastructure repair costs

Prioritized issues

Bank erosion is among the six priority issues identified in the 2024-2034 Water Master Plan. For more information, consult the diagnostic 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