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Shorelines

• • Shoreline Photos

Shorelines and waterfronts are the most important part of the lake ecosystem. As much as 90% of things living in a lake are found in the shallow-water "ribbon of life" (the littoral zone). Natural shoreline vegetation will prevent soil erosion, and vegetation in the first 10 to 30 metres of shore land (the riparian zone) also controls erosion, reduces run-off into the lake, filters out excess nutrients, and shades and cools shallow water. A contiguous forest belt will provide another buffer.

Lac Mahon

Lac Mahon has about 5.2 km of shoreline. About 31% of the shoreline (riparian) zone is used for cottage/residential property, 55% is natural (mountain, lowland) and 14% includes infrastructure (hydro towers, road).

Natural vegetation cover is generally good, with pockets of ornamental cover (e.g. lawn). Much cottage and residential shoreline is natural, but there are altered shorelines (e.g. retaining wall, cleared beachfront, boat launch). About 40% of the littoral zone is marsh (see Wetlands).

• See riparian zone use, vegetation cover (using Google satellite), and shoreline maps, also Shoreline photos.

Guidelines

In Ontario, the Rideau Valley Conservation Authority has a target guideline of 75% natural shoreline cover (using a 30-metre riparian zone). Evidence from the Rideau Lakes suggests a link between shoreline cover and water quality - out of 10 lakes below the 75% target figure, 5 lakes had poor to very poor water quality.

RSVL has a protocol to assess the condition of lake shores using three criteria (ABV-7 has used this protocol for lakes at Kazabazua, see the report). 

• How much of the 15-metre riparian zone is natural, or is used for infrastructure, agriculture, forestry, or habitation.

• How much of the riparian zone is covered with natural vegetation, ornamental vegetation, or inert materials such as buildings or concrete (ABV-7 considers less then 40% natural vegetation to be insufficient).

• How much of the shoreline is natural, or is degraded by retaining walls, or bare soil (e.g. beachfront) or erosion caused by human activity.

Shoreline Protection

Under Quebec provincial law, lakes and shorelines are protected habitats, enforced by municipal regulation. Prohibitions (with some exceptions) include putting lawns down to shore, removing aquatic plants, adding sand to create a beach, and building docks on cribs. See Lakes and watercourses - Ours to save. 

In La Pêche, municipal bylaw 03-429 stipulates 15-metre riparian zones, or 30 metres in some cases. Permitted activities in riparian zones are limited, including construction work.

The MRC des Collines enacted Bylaw 137-09 in 2009 to get property owners to re-naturalize shorelines. Within a strip 5-metres from shore, lawn-mowing or any other vegetation control is prohibited, and the strip must be revegetated if not naturally vegetated, Residents may maintain a clear strip up to five meters wide for access to the water, (In Ontario, municipal plans are recognizing a 30-metre band of shoreline natural vegetation, see shorelines fact sheet.)

The MRC also identified priority actions in response to episodes of blue-green algae in Gatineau Valley lakes, caused mainly by phosphorous:

• • make sure that septic facilities are up to standard

  • avoid spreading fertilizers close to lakes

  • ban the use of detergents with phosphates

  • maintain shorelines in their natural state

  • let lawns go so that nature can take over again

  • replant shorelines with appropriate shrubs.

See Steps to improve the quality of Lake Mahon (2002). To these lists should be added that motor-boat prop wash not disturb the "internal load" of lake-bottom sediments bound with phosphorous. Shallow lakes like Mahon are particularly affected by this mixing action, which can happen to a depth of 15 feet - see this review, and the Boater's Code.