Mud Bay Nature-based Foreshore Enhancements

Current climate scenarios project global sea-level rise. In British Columbia municipalities are advised to plan for at least 1 meter of sea-level rise by 2100 and 2 meters for 2200. Sea-level rise makes the Mud Bay region susceptible to coastal flooding.

With sea-level rise, coastal ecosystems, including tidal marshes, naturally adapt by migrating inland. In a natural landscape, this migration isn't an issue, as the ecosystem can expand landward. However, the presence of fixed structures, such as dikes, breakwaters, highways and railroads, hinders this natural process. This phenomenon is known as "Coastal Squeeze".

In Coastal Squeeze scenarios, coastal ecosystems retract, unable to extend inland. Confined between rising water on one side and hard infrastructure on the other, these ecosystems are essentially "squeezed" within fixed boundaries. As a result, these landscapes recede and reduce in area, leading to a loss of ecologically important intertidal habitat.

Unfortunately, in Mud Bay our coastal ecosystems are undergoing coastal squeeze. This is causing the gradual disappearance of our marshes, along with essential wildlife habitat and species.

Tidal marshes play a crucial role in flood protection, functioning as natural barriers that prevent erosion and reduce the impacts of flooding. They serve as natural flood defenses, absorbing wave energy and diminishing the effects of storm surges. Additionally, tidal marshes play a critical role in climate regulation by capturing atmospheric carbon dioxide and storing it underground, thus aiding in the battle against climate change.

Other benefits include:

• Water Quality Improvement: Tidal marshes play a key role in enhancing water quality. They act as natural filters, removing excess nutrients and harmful pollutants such as herbicides, pesticides, and other contaminants from the water.
• Wildlife Habitat: These marshes provide essential habitats for a wide range of species, including birds, fish, amphibians, and invertebrates. By supporting such diverse life, tidal marshes contribute significantly to the biodiversity of the region.
• Erosion Control: These marshes are effective in stabilizing shorelines and preventing erosion. They achieve this by trapping sediments with their plant roots and diminishing the impact of wave action.
• Recreation and Well-being: Beyond their ecological importance, tidal marshes offer a variety of recreational opportunities. They enhance human well-being through their natural beauty and provide activities such as bird watching, fishing, hiking, and educational experiences.

It is critically important to protect these marshes to prevent their disappearance from our coastlines.

Boundary Bay and Mud Bay, located in the southwest corner of Surrey, adjacent to the City of Delta and within the traditional territories of the Semiahmoo First Nation, feature a diverse array of habitat types and land uses. These include intertidal mud flats, estuaries, marshes, farmland, and suburban areas.

The 250-kilometer coastline of Boundary Bay is influenced by the fluctuating inflow of waters from the Salish Sea. Additionally, Mud Bay is affected by freshwater inputs from the Serpentine and Nicomekl Rivers, resulting in a distinct brackish influence in the bay and the formation of intertidal marshes.

A thriving tidal marsh relies on a continuous supply of sediments. For millennia, the gradual buildup of sediments across the delta’s floodplains was shaped by repeated seasonal flooding. However, significant human interventions beginning in the 19th century have altered the courses of our rivers. These changes, along with dredging and the construction of river training structures, have disrupted the natural distribution of sediments across the tidal flats.

The Serpentine and Nicomekl Rivers have been outfitted with dikes, floodgates, and sea dams to manage seasonal flooding and support agricultural activities. Since marsh ecosystems depend on sediment deposition for their growth, a deficit in sediment can result in loss of elevation and ecological degradation.

Additional pressures are further impacting Mud Bay communities, including tidal fluctuations, land subsidence, redevelopment and densification of land, grazing of marsh vegetation by resident invasive Canada geese and migratory snow geese, along with aging diking infrastructure.

These pressures pose significant and complex threats to our ecosystems and shorelines that require thoughtful, long-term, collaborative solutions. By understanding the challenges Mud Bay faces, we can collectively strategize on building a resilient future for Surrey's residents, its shoreline, and its wildlife.

The living dike concept involves elevating the natural marshes to adapt to rising sea levels. By constructing a gently elevated slope, the aim is to incrementally increase the marsh's overall elevation. Sediments and native marsh vegetation are placed on this raised slope, positioned on the foreshore in front of the dike, acting as an initial buffer against incoming waves. This strategy not only mitigates erosion but also supports the nourishment of plant and wildlife species.

A living dike adopts a sustainable approach to climate change, focusing on building resilience to sea level rise instead of continuously constructing higher dikes.

The Mud Bay Nature-based Foreshore Enhancements Project is one of the actions in the  Coastal Flood Adaptation Strategy (CFAS)  designed to help Surrey adapt to coastal flooding and sea-level rise. This project forms a part of Surrey's Disaster Mitigation and Adaptation Fund (DMAF) Program, which encompasses a total of  13 coastal flood adaptation projects .

The project aims to demonstrate the living dike concept by adding sediment and replicating the natural processes that facilitate the formation of a living dike. This deposited sediment is intended to nourish the foreshore area and support the growth of planted vegetation.

The outcomes of the Living Dike project will be used to improve our understanding of techniques of marsh construction and salt marsh restoration. The findings of this project will help inform future projects across BC and beyond, and aims to understand how we can:

• Combat rising sea levels sustainably,
• Build marsh resilience,
• Improve community resilience and
• Enhance ecological health and supporting species dependent on the tidal marsh.

The Mud Bay Nature-based Foreshore Enhancements Project is a partnership between City of Surrey, City of Delta and Semiahmoo First Nation.

The four stabilization techniques being tested aim to determine their effectiveness in erosion control and salt marsh restoration. These techniques vary in their levels of stability and the degree of intervention required, ranging from low to medium to high.

Oyster shell bags consist from biodegradable mesh filled with collected oyster shells. These bags are stacked in a line, serving as a permeable barrier between the elevated sediment of the pilot project and the adjacent tidal mudflats. They are designed to mitigate erosion and retain sediments, leveraging their permeable nature.

 Brushwood dams  consist of vertical wooden support poles staggered on opposite sides, with horizontal bundles of woven brushwood in between. Brushwood typically comprises of branches from bushes, shrubs, and small trees, such as willow or hardhack.

These dams are permeable and semi-flexible, widely used in the Netherlands and Germany for their effectiveness in reducing hydrodynamic forces and aiding in sediment retention and accumulation. The design allows water to flow through, diminishing wave action, thus providing high edge stability. While brushwood dams are anticipated to offer greater stability compared to the oyster shell bags, they are also more labor-intensive to construct.

Rock berms, built from well-graded cobbles, are positioned at the seaward edge of constructed salt marshes. They are expected to offer the highest level of stability among the four stabilization techniques and are among the easiest to construct. Compared to brushwood dams, rock berms are considered less labor-intensive to install.

Sand berms, in contrast to rockberms, require the least amount of intervention among the four stabilization techniques, though they are expected to offer lower stability. However, sand berms closely mimic a natural seaward edge and represent the most cost-effective option.

Take a look at the site in Mud Bay and explore the different stabilization techniques at the Surrey pilot site:

A healthy salt marsh acts as a natural barrier, safeguarding shorelines from erosion and flooding. The marsh vegetation, especially when located in front of a dike, serves to buffer and slow down incoming waves and promote sediment build up. This reduction in wave action decreases the erosive force and, consequently, lowers the risk of dike failure. This way marshes can function as a natural amplifier for flood infrastructure protection.

In addition to offering flood protection, salt marshes are recognized for their ability to improve water quality, store carbon, and support diverse fish and wildlife. Through the restoration of salt marsh habitats via the living dike, we aim to prevent the disappearance of our marshes due to coastal squeeze.

Mud Bay's rich ecosystem, which includes mud flats, eelgrass beds, and salt marshes, serves as critical habitat for a diverse array of wildlife. It is an essential breeding and feeding ground for various salmon species, including Chinook and coho, which play a crucial role in the marine food chain. Additionally, the area supports a wide range of migratory birds such as Western Sandpipers, Brant Geese, and Great Blue Herons. These species depend on Mud Bay as a crucial stopover during their migrations along the Pacific Flyway. Recognized as part of the Fraser Delta Ramsar Wetland of International Importance, Mud Bay is also the most significant overwintering location in Canada for migratory waterfowl, shorebirds, and raptors.

In addition to birds, Mud Bay's habitat is essential for marine mammals like harbor seals and sea lions, which are often seen along the coast. The mud flats and eelgrass beds provide a rich feeding ground for these mammals. The area is also home to a variety of invertebrates like Dungeness crabs and Pacific oysters, contributing to the region's biodiversity.

The Boundary Bay coastline is among the most crucial in British Columbia for supporting migratory and wintering waterfowl. The presence of these species, along with the unique environmental conditions of Mud Bay, underscores the importance of preserving this area not only for its ecological value but also for the role it plays in supporting local and migratory wildlife.

Various native salt marsh plant species, sourced locally, were planted on the living dike pilots to encourage growth and aid in the development of salt marsh vegetation. Utilizing species adapted to local conditions ensured that these plants could effectively replicate existing environmental conditions. This approach was anticipated to result in a more successful and resilient marsh ecosystem over the long term.

Seeds and plant material were collected for propagation and grown in nurseries. These nursery-grown species that were successfully tested on the pilot sites will then be planted on the future full-scale living dike, further ensuring the suitability and adaptability of the vegetation to the specific conditions of the area.

Species are evenly spaced across the marsh platform, including:

• Rushes
  • Baltic rush - Juncus balticus
  • Seacoast bulrush - Bolboschoenus maritimus
• Grasses
  • Foxtail barley - Hordeum jubatum
  • Tufted-hairgrass - Deschampsia cespitosa
  • Seashore saltgrass - Distichlis spicata
• Coastal Plants
  • Seaside arrowgrass - Triglochin maritima
  • Seaside plantain - Plantago maritima
  • Sea asparagus/ Pickleweed - Sarcocornia pacifica

By supporting salt marsh restoration using locally sourced plants, the living dike initiative enhances and expands this unique natural habitat, thereby enabling both the marsh and its diverse species to flourish.

The project is within the core territory of Semiahmoo First Nation and the traditional territories of the Katzie, Kwantlen, Sto:lo, and Tsawwassen First Nations.

As climate change progresses, coastal areas are facing heightened risks of more frequent and severe flooding, from storm surge to sea level rise. This situation necessitates urgent and innovative adaptation solutions to protect these vulnerable communities from potential damage. In response to these varied challenges affecting both communities and ecosystems, Semiahmoo First Nation, City of Surrey, and City of Delta are collaborating on the Mud Bay Nature-based Foreshore Enhancement project to bolster climate resilience. Additionally, communities and sectors in the region are uniting to develop coordinated actions on a regional level, focusing on safeguarding communities and the residential environment while seeking sustainable and long-term solutions for flood adaptation.

Community values and input hold significant importance for the City of Surrey and are consistently taken into consideration during the development of the living dike project. Both during the initial engagement phase and through ongoing community engagement, the input from the community is carefully considered.

Living with Water, funded by the Pacific Institute for Climate Solutions, is involved in the Mud Bay living dike pilot project. The Living with Water team consists of a diverse, multidisciplinary team of researchers and solution seekers that help communities prepare and adapt for sea-level rise and coastal flooding by adapting value-based thinking. The research team aims to explore answers to serious questions related to nature-based solutions and how they could be used in integrated, inclusive and boundary spanning adaptation strategies that contributes to the coastal resilience. They do so by foregrounding community values, Indigenous knowledge and perspectives in coastal adaptation planning. These values include:

If you want to learn more how Living with Water acts upon these values and how they are active in the Mud Bay region, click  here .

The initial phase of the project commenced in 2019. Both pilot sites, located in Surrey and Delta, were constructed in Spring 2023. The Mud Bay Nature-based Foreshore Enhancements project employs an adaptive management approach, wherein ongoing monitoring and analysis of results will guide the construction of the full-scale living dike planned for 2025.

Stay informed about the Mud Bay Nature-based Foreshore Enhancements Project and other Natural Infrastructure projects by checking out the  website of the City of Surrey  and following the  Living With Water  initiative.

For more information about Surrey's pilot project, please contact  coastal@surrey.ca .