3. Present Situation

3.1 The Natural Setting

The Saint-Ours Canal lies within the climatic region of Montreal, recognized as the mildest region of Quebec. This area enjoys the longest number of days without frost, the longest period of sunshine, and the longest growing season.

The Saint-Ours Canal lies within the geomorphological area of the St. Lawrence Lowlands. Recent reworked deposits of alluvium cover surface deposits of silty clay that overlay clay schist bedrock. The Canal is in the area known as the Lower Richelieu, which starts upstream at the rapids lying between Saint-Jean and Chambly.

The east bank section of the site lies below Route 133. It is made up of fill that was added progressively as the need arose to give better access to the lock. The change in elevation and the limited space meant that the access route was restricted to a fairly steep slope. However, the rest of the site is more or less flat. The terrain drops off slightly upstream, and is liable to flood in the spring.

The relief of Darvard Island is more pronounced, with two small hills on a north-south axis. Their configuration forms a natural passage from the upper lock gate to the east tip of the dam. The island’s topography means that some slopes are difficult to negotiate lengthwise and require staircases. Heavy pedestrian use has made other slopes vulnerable to erosion. On the west bank, the land forms a shallow basin sloping gradually down to the river.

The natural vegetation is largely confined to Darvard Island and is dominated by a transitional species, red pine, and pioneer species such as birch and poplar. Red pine has colonized almost the whole island, along with white pine and basswood. American ash, red elm, and Saskatoon berry are found in the damper areas by the river. The red pine stand is reaching the upper limit of its lifespan and over the next few decades will likely deteriorate.16

The island is notable for its interesting full-growth ornamental vegetation, consisting of trees and shrubs growing beside the lock and the superintendent’s house. This vegetation is remarkable in its diversity and includes some magnificent specimens. The east bank has little vegetation and consists of large areas of mown lawn, while at the beginning of the century large deciduous trees grew on this bank and on the site of the old flourmill. On the other side of the river there is little to speak of except a row of Lombardy poplars along the shore.

Considered the most important tributary of the south shore of the St. Lawrence River, the Richelieu is also well-known to fishermen for its variety of fish species. The replacement of the old dam on the Saint-Ours Canal in 1969 increased the difference in ground level between the upper and lower river and eliminated the old fish ladder, a situation which endangered certain species.17

Recent studies showing the need to reopen a passage upstream past the Saint-Ours dam resulted in the construction of a new fish ladder, inaugurated in the summer of 2001.18

Most of the shore belonging to Parks Canada has an artificial appearance, with rocks piled along the western shore of the island and concrete walls running the length of the canal, the lock and the east bank of the river. Only the upper and lower ends of the filled-in section to the east have a more natural look.

16 This stand was formerly unable to regenerate owing to intense use by visitors, regular lawn mowing amongst the trees, and uncontrolled pedestrian traffic. Interventions occurring between 1995 and 1996 (shrubs were planted, paths were laid out, and a stop was put to lawn-mowing) have improved the likelihood that shrubs and herbaceous undergrowth will regenerate.

17 As early as 1998, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) identified the copper redhorse as an endangered species, as did Quebec’s Act respecting threatened or vulnerable species. The St. Lawrence Vision 2000 plan deemed its conservation to be a priority.

18 The new fish ladder on the western side of the river near Saint-Roch is made of reinforced concrete and encompasses a series of 16 basins over its 48.5-m length. The fish pass through a series of vertical slits to the far end. An adjacent fish ladder was built for eels. This is the first multi-species fish ladder ever built in Canada.

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