Clean Foundation Northumberland Strait Coastal Restoration Project Tidal Crossing Assessments – Antigonish County

126 Portland St • Dartmouth, NS • B2Y 1H8 • Phone: (902) 420-3474

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Northumberland Straight Costal Restoration Project Antigonish County

Table of Contents INTRODUCTION...... 1 Methodology ...... 1 SITE DESCRIPTIONS ...... 4 Antigonish Landing ...... 4 Captains Pond ...... 8 Frasers Marsh ...... 12 Mahoneys Beach ...... 16 Southside Harbour...... 20

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Northumberland Straight Costal Restoration Project Antigonish County

INTRODUCTION

About the Project: The Clean Foundation’s Northumberland Strait Coastal Restoration Project is funded by the Department of Fisheries and Oceans Canada’s Coastal Restoration Fund. The project aims to restore up to 15 hectares of saltmarsh habitat in the Northumberland Strait region of mainland Nova Scotia while working to increase local communities’ capacity to improve their coastal resilience through workshops, volunteer opportunities, and open access to the project’s technical data.

What is a Saltmarsh? A saltmarsh is a coastal wetland that is regularly flooded by brackish or saltwater tides. They can be found in the intertidal zone between land and open water, where they are underwater at high tide and exposed at low tide. Saltmarshes are home to many species of flora and fauna, some of which are uniquely found in these habitats. A variety of salt- tolerant grasses make up the majority of saltmarsh vegetation and their distribution is important in distinguishing the high and low marsh areas.

Reason for Inventorying: Coastal wetlands in Nova Scotia have been heavily impacted by human activity over the last 400 years, resulting in the loss and degradation of these ecosystems. Among many other reasons, saltmarshes are valuable as they protect infrastructure, support our economy, provide recreational space, and much more. Quantifying the loss and degradation of these wetlands allows us to understand the state of our coasts and plan strategically for the future. Identifying degraded habitat and at-risk infrastructure along the Northumberland Strait to will help inform where restoration projects are needed and feasible.

Methodology

Basic Desktop Assessment: Beginning in May 2018, potentially degraded saltmarsh sites were initially identified through a Basic Desktop Assessment (BDA). The scope of the assessment covered the north shore of Nova Scotia, focusing on saltmarshes along the Northumberland Strait. The BDA involved analysis of pre-existing data sets with the use of ArcGIS and Google Earth. Road and water networks were intersected with known wetland systems to determine where water crossing structures (including culverts and bridges) should exist. From there, saltmarshes at these crossing points were studied for signs of degradation. Historical aerial imagery was also referenced to confirm changes at a site. The BDA resulted in identification

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Northumberland Straight Costal Restoration Project Antigonish County

of over 500 sites within the counties of Antigonish, Colchester, Cumberland, and Pictou. These are considered “Level 1” sites.

In the summers of 2018 and 2019, 39 of the 500 sites were visited in person to conduct a Tidal Barrier Audit and/or deploy water level loggers. These are considered “Level 2” sites.

Figure 1: Potentially degraded saltmarsh sites identified in Antigonish County, Nova Scotia. Level 1 sites were investigated via a Basic Desktop Assessment only. Level 2 sites were also visited in person for a Tidal Barrier Audit and/or the deployment of water level loggers.

Tidal Barrier Audits: Conducting a Tidal Barrier Audit (TBA) involved in-person evaluation of several parameters at a site. The suspected barrier was assessed on structural integrity and condition, dimensions and placement, and the nature of the impact it was having on the site. Vegetation was surveyed on both sides of the potential barrier in order to compare species composition, distribution, and state with that of a “healthy” saltmarsh. Site hydrology (water characteristics) was assessed through observation, as well as through the

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Northumberland Straight Costal Restoration Project Antigonish County

use of a water quality sampling meter, when possible. Telltale signs of flow restriction, such as erosion, pooling, or stagnant water, were recorded. If wildlife was present during the TBA this was noted. Photos of the potential barrier and the landward and seaward sides of the system were taken during the visit.

Water Level Loggers: At 21 of the Level 2 sites, water level loggers were deployed to monitor the flow of tidal and fresh water at a site. In most cases, a logger was placed on either side of the barrier so that restrictions in flow caused by the barrier could be quantified. Differences in water levels on either side of a potential barrier are a good indicator of how and to what extent the flow of water is being restricted. The water level loggers record the height of the water above their sensors in meters using the Canadian Geodetic Vertical Datum of 2013 (CGVD2013) as a reference.

Restoration: Three sites were selected from the 39 Level 2 sites as primary candidates for restoration work. These sites will be restored as part of the 15 hectares of habitat under the Northumberland Strait Coastal Restoration Project. These are considered “Level 3” sites and are not further documented in this text.

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Northumberland Straight Costal Restoration Project Antigonish County

SITE DESCRIPTIONS

The following text describes the Level 2 sites within Antigonish County, Nova Scotia. Site descriptions summarize the information gathered through the Basic Desktop Assessment, Tidal Barrier Audit, and water level logger deployments.

Antigonish Landing

Summary: This site is located in Antigonish County where a dirt footpath off of Landing Road crosses channels flowing into Rights River, as shown in Figure 2. The barrier is the dyke that the footpath sits on, which makes two crossings: a shorter crossing where the dyke is in adequate condition and completely restricts flow, and a longer crossing where the dyke is failing in one section and partially restricts flow. Water level logger data was collected at this site. The water levels recorded in Figure 3 illustrate the tidal restriction at the site. Levels on both sides of the barrier are in-sync, indicating that adequate flow is able to pass through the section of failing dyke. Note that water level loggers were deployed to monitor the longer crossing and likely do not reflect the level of restriction experienced on either side of the shorter crossing.

Area of site: 5.39 Hectares

Recommendations: Install an open bottom culvert in the portion of the dyke that makes the shorter crossing. Remove the failing section of the dyke, OR; Replace the portion of the dyke that makes the longer crossing with a boardwalk that allows for tidal flow underneath.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 2: Aerial view of the Antigonish Landing site. The barrier, circled in orange, is a footpath path off of Landing Road. There is an impoundment to the north of the barrier.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 3: Water levels at the Antigonish Landing site. The x-axis represents the date and time water level loggers recorded readings. The y-axis represents the height of the water above the loggers’ sensor in meters, based on the Canadian Geodetic Vertical Datum of 2013. The water level on the seaward side of the barrier is shown in blue. The water level on the landward side of the barrier is shown in orange. The values are synchronized; tidal flow is accommodated.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 4: Seaward side, Antigonish Landing site. Figure 5: Landward side, Antigonish Landing site.

Figure 6: Along the footpath, Antigonish Landing site.

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Northumberland Straight Costal Restoration Project Antigonish County

Captains Pond

Summary: This site is located in Antigonish County where an artificial channel connects Captains Pond to Antigonish Harbour, as shown in Figure 7. The barrier is a steel bridge that crosses the channel, connecting Southside Harbour road. While the bridge is in good condition, it is undersized and has resulted in a bottleneck and high velocity flow. To deflect wave energy away from the toe of the bridge, the structure has been equipped with armour rocking and secondary wooden walls. Water level logger data was collected at this site. The water levels recorded in Figure 8 illustrate the tidal restriction at the site. The water level on the landward side of the structure is consistently lower at high tide and higher at low tide than the water level on the seaward side. This indicates that flow is being somewhat restricted in and out of the system.

Area of Site: 76.85 Hectares

Recommendations: Replace the bridge with one that makes a longer crossing to create a wider channel.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 7: Aerial view of the Captains Pond site. The barrier, circled in orange, is a bridge that is part of Southside Harbour Road. The channel connecting Captains Pond and Antigonish Harbour is artificial.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 8: Water levels at the Captains Pond site. The x-axis represents the date and time water level loggers recorded readings. The y-axis represents the height of the water above the loggers’ sensor in meters, based on the Canadian Geodetic Vertical Datum of 2013. The water level on the seaward side of the barrier is shown in blue. The water level on the landward side of the barrier is shown in orange. The values are not synchronized; incoming and outgoing tides are not accommodated. Partial tidal restriction.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 9: Seaward side, Captains Pond site. Figure 10: Landward side, Captains Pond site.

Figure 11: Bridge from the seaward side, Captains Pond Figure 12: Bridge from the landward side, Captains Pond site. site.

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Northumberland Straight Costal Restoration Project Antigonish County

Frasers Marsh

Summary: This site is located in Antigonish County where Monks Head Road crosses a channel that flows into Captains Pond, as shown in Figure 13. There are two barriers at this site. The first is a perched steel culvert that passes through the tall dyke that the road sits on. Further landward, there is an old crossing which is in poor condition. Where the dyke of the old crossing dips down, the remnants of a wooden box culvert can be seen. These remnants raise the level of the channel bed and restrict flow. Water level logger data was collected at this site. The water levels recorded in Figure 14 illustrate the tidal restriction that the current crossing poses at the site. Water levels on the landward side of the barrier are not associated with those on the seaward side except during extremely high tides. This indicates that the culvert does not allow fresh or tidal water to flow through it until it exceeds a certain level. Note that water level loggers were deployed to monitor the current crossing and do not reflect the addition restriction caused by the old crossing.

Area of site: 43.12 Hectares

Recommendations: Remove the dyke and wooden box culvert of the old crossing. Replace the culvert under Monks Head Road with a bridge, OR; Replace the culvert with a larger, open bottom culvert, placed at a lower elevation.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 13: Aerial view of the Frasers Marsh site. The barriers, circled in orange, are a culvert passing under Monks Head Road and a dyke to the south of the road. There is impounded water to the south of the barriers.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 14: Water levels at the Frasers Marsh site. The x-axis represents the date and time water level loggers recorded readings. The y-axis represents the height of the water above the loggers’ sensor in meters, based on the Canadian Geodetic Vertical Datum of 2013. The water level on the seaward side of the barrier is shown in blue. The water level on the landward side of the barrier is shown in orange. The values are not synchronized; neither tides nor freshwater storm discharge are accommodated. Complete tidal restriction.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 15: Seaward side, Frasers Marsh site. Figure 16: Landward side, Frasers Marsh site.

Figure 17: Culvert from the landward side, Frasers Marsh Figure 18: Remnants of culvert in dyke on the landward site. side, Frasers Marsh site.

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Northumberland Straight Costal Restoration Project Antigonish County

Mahoneys Beach

Summary: This site is located in Antigonish County where a driveway off of Mahoneys Beach Road cuts off a marsh from Antigonish Harbour, as shown in Figure 19. The barrier is the dyke that the driveway sits on, which forms a complete restriction across the eastern side of the marsh. The driveway is in adequate condition. The former marshland on the landward side of the barrier has been further modified and is now mowed. Water level logger data was collected at this site. The water levels recorded in Figure 20 illustrate only the water levels on the seaward side of the barrier. From this information it can be determined how much tidal inundation the restricted marsh would see if the barrier was not present.

Area of site: 2.19 Hectares

Recommendations: Install an open bottom culvert under the driveway. Reduce mowing to restore saltmarsh grasses. Collect further elevation data around the site to identify additional tidal barriers.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 19: Aerial view of the Mahoneys Beach site. The barrier, circled in orange, is a driveway off of Mahoneys Beach Road. The area to the west of the barrier was saltmarsh.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 20: Water levels at the Mahoneys Beach site. The x-axis represents the date and time water level loggers recorded readings. The y-axis represents the height of the water above the loggers’ sensor in meters, based on the Canadian Geodetic Vertical Datum of 2013. The water level on the seaward side of the barrier is shown in blue. As there is no water on the landward side of the barrier, a landward water level logger was not deployed.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 22: Landward side, Mahoneys Beach site.

Figure 21 Seaward side, Mahoneys Beach site.

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Northumberland Straight Costal Restoration Project Antigonish County

Southside Harbour

Summary: This site is located in Antigonish County where Southside Harbour Road crosses a channel flowing into Pomquet Cove, as shown in Figure 23. The wooden bridge connecting Southside Harbour over the channel is in good condition and does not appear to restrict tidal flow. On the landward side of the bridge there are remnants of an old crossing, which may restrict flow. There are two beaver dams further landward. Water level logger data was collected at this site. The water levels recorded in Figure 24 illustrate the lack of tidal restriction under the bridge. Levels on the seaward and landward sides of the structure are nearly synchronized. Note that water level loggers were deployed to monitor the bridge and do not reflect any restriction caused by the old crossing or beaver dams on the landward side of the system.

Area of site: 1.95 Hectares

Recommendations: Collect level logger data on either side of the old crossing to determine if it poses a restriction to tidal flow. Remove the dyke of the old crossing if it is a barrier.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 23: Aerial view of the Southside Harbour site. The suspected barrier, circled in orange, was a bridge that is part of Southside Harbour Road. There are remnants of an old crossing to the east of the road which may be a barrier.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 24: Water levels at the Southside Harbour site. The x-axis represents the date and time water level loggers recorded readings. The y-axis represents the height of the water above the loggers’ sensor in meters, based on the Canadian Geodetic Vertical Datum of 2013. The water level on the seaward side of the barrier is shown in blue. The water level on the landward side of the barrier is shown in orange. The values are synchronized; tidal flow is accommodated.

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Northumberland Straight Costal Restoration Project Antigonish County

Figure 25: Seaward side, Southside Harbour site. Figure 26: Landward side, Southside Harbour site.

Figure 27: Bridge from the seaward side, Southside Harbour site.