Provides some aquatic benefit as stone creates habitat complexity and cover Provides some ecological benefit as berm can be vegetated

Minimal maintenance requirements Smallest land and lakebed footprint

No added ecological or recreational benefits Slightly less effective erosion control compared to other concepts

Provides excellent aquatic benefits through addition of habitat features Provides some ecological benefit as berm can be vegetated Provides added recreational benefits including beach area and access for non-motorized boats

Some long-term maintenance required for beach nourishment Largest footprint on lakebed

Northwest Shoreline Existing Conditions

This focus area includes the section of shoreline on Algonquin Island that follows Seneca Avenue. The shoreline is currently protected by a seawall. The wall experienced regular overtopping during the high lake level events. During these events, sandbags were piled along the wall to provide temporary flood protection.

Sandbags installed behind a sheet pile wall along the northwestern shoreline of Algonquin Island.

Existing Algonquin Island seawall along Seneca Avenue. Source: Baird, 2017

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Aerial view of sandbags and pumps installed behind a sheet pile wall on Algonquin Island.

Northwest Shoreline Concept Designs

The following concept designs are being presented:

Northwest Shoreline Summary Video

Concept 1
Steel Sheet Pile Wall

Concept 1 involves installing a new steel sheet pile wall in front of the existing seawall. The new wall would be built to a higher elevation and the land adjacent to it would be raised.

Map of Algonquin Island Northwest Shore showing Sheet Pile Wall Treatment.

Algonquin Island - Concept 1: Steel Sheet Pile Wall. Source: Baird, 2022.

Cross-section of sheet pile wall treatment installed over the existing sheet pile wall.

Algonquin Island - Concept 1, Cross-section A. Source: Baird, 2022.

Advantages

Minimal maintenance requirements
Smallest land and lakebed footprint

Disadvantages

No added ecological or recreational benefits
Slightly less effective erosion control compared to other concepts

OVERALL EVALUATION RANKING: LOW

Concept 2
Impermeable Berm

Concept 2 involves installing an impermeable berm along the shoreline on top of the existing seawall. A stone buttress would need to be placed in front of the existing wall to provide structural support. This buttress could be built out of rip rap or stacked armourstone.

Map of Algonquin Island Northwest Shore showing an impermeable berm with a revetment.

Algonquin Island - Concept 2: Impermeable Berm. Source: Baird, 2022.

Cross-sections showing a shoreline revetment backed by an impermeable berm with a clay core.

Algonquin Island - Concept 2, Cross-section A with rip rap buttress. Source: Baird, 2022

Impermeable berm supported by a stacked armourstone wall

Algonquin Island - Concept 2, Cross-section B with armourstone buttress. Source: Baird, 2022

Advantages

Provides some aquatic benefit as stone creates habitat complexity and cover
Provides some ecological benefit as berm can be vegetated

Disadvantages

Increased footprint on lakebed

OVERALL EVALUATION RANKING: MEDIUM

Concept 3
Impermeable Berm and Nearshore Habitat

Like Concept 2, Concept 3 includes installing an impermeable berm along the shoreline on top of the existing seawall. Instead of a stone buttress, the existing seawall would be supported by beach fill which would create a sloping nearshore habitat with aquatic vegetation and rocky habitat features.

Map of Algonquin Island Northwest Shore showing a nearshore habitat treatment with an impermeable backshore berm.

Algonquin Island - Concept 2: Impermeable Berm and Nearshore Habitat. Source: Baird, 2022.

Cross-section of naturalized habitat shoreline with a backshore impermeable berm.

Algonquin Island - Concept 3, Cross-sections B. Source: Baird, 2022.

Digital rendering of a naturalized habitat shoreline with aquatic vegetation and habitat stone.

Algonquin Island - Concept 3, Rendering of Nearshore Habitat. Source: Baird, 2022.

Detailed digital rendering of a naturalized habitat shoreline being used by fish, birds and people.

Algonquin Island - Concept 3, Rendering of Nearshore Habitat. Source: Baird, 2022.

Advantages

Provides excellent aquatic benefits through addition of habitat features
Provides some ecological benefit as berm can be vegetated
Provides added recreational benefits including beach area and access for non-motorized boats

Disadvantages