High-water line

Generally speaking, the high-water line is the boundary between water property in the domain of the State and private property.

Delimitation of water property in the domain of the State is a review that enables the position of the boundary between water property in the domain of the State and private property to be established. State water property generally begins at the high-water line.

Definition of the high-water line

For tidal areas, the high-water line is the average elevation of the highest March tides observed over a 19-year period of time. In areas not subject to tides, the high-water line corresponds to the boundary of a lake or watercourse at full bore, without overflow or flooding. The high-water line is dynamic and can vary over time under the effects of natural erosion and alluviation.

The high-water line used as a property boundary is determined on the basis of surveyor analysis. Other boundaries may be statutory, as is the case for a parcel of the rivière Richelieu.

Effects of shoreline work

The position of the high-water line for shoreline property in its natural state varies with natural erosion and alluviation. However, the position can be changed through human intervention such as excavation or backfilling. The shoreline is then said to be anthropogenic.

When shoreline becomes anthropic, the high-water line boundary no longer varies and must be set to its position prior to human intervention.

Last update: February 23, 2023


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