Erosion of the banks of the St. Lawrence: we must work with nature

While the estuary and St. As the Gulf of Lawrence faces a shortage of oxygen, the river’s shores are eroded, which has direct consequences for surrounding communities as well as local ecosystems. Here is an analysis by Jacob Stolle and Damien Pham-Van-Bang, professors at the National Institute for Scientific Research (INRS).


ANALYSIS – The shores of St. The Lawrence River is eroding. It is important for the infrastructure, the economy and the well-being of the inhabitants. It exposes communities to flooding and can destroy local ecosystems.

Under the threat of a climate catastrophe, in-depth reflection is needed to enable adaptation to a changing climate in St. Lawrence.

On Prince Edward Island, the average erosion is about 0.3 meters per year. In New Brunswick it is about 0.5 meters per year. But in Quebec it’s closer to 2 meters a year! And that rate of erosion is expected to increase as climate change is expected to raise sea levels and bring water closer to local communities. More and stronger storms will bring bigger waves to the coastline, and reduced sea ice will give winter storms access to the coastline, the country’s contact with the sea.

The latest report from the UN’s Intergovernmental Panel on Climate Change (IPCC) calls for transformational adaptation, to completely rethink the way we adapt to climate change to include more sustainable solutions.

As professors of coastal engineering, we work to develop immutable solutions for adaptation to climate change in coastal and estuarine environments. We work with communities, businesses and nonprofits to better understand how natural systems can be used to protect coastlines from erosion and flooding.

Traditional approaches are no longer suitable

In Quebec, about 97% of the coastal infrastructure is what we call “hard”. You can see these dikes and breakwaters along St. Lawrence River, intended to maintain or promote shoreline.

This approach is recommended worldwide as most design manuals, research and case studies focus on hard infrastructure; we have been using them for centuries. These types of infrastructure-based adaptation methods are well established and proven to solve short-term problems without taking up much space on the coast.

The problem with hard infrastructure is that it does not adapt to a changing climate. As such, it often requires maintenance and redevelopment and can inhibit the natural development of the coastline. This is called the “coastal squeeze”.

Coastal pinching is particularly problematic when coastlines are designed to address acute symptoms (such as localized flooding) rather than address the underlying problem. These limitations, if not handled properly, tend to crowd out or exacerbate the problem.

Examples can be seen in Kamouraska Bay, where the reclamation of land using dykes for agricultural purposes has caused the loss of three quarters of the marsh ecosystem over the past century. In addition, these dikes were overcome during recent floods and trapped saline water on agricultural land.

Working with nature in a changing climate

The consequences of climate change are becoming more and more apparent. Its effects are felt throughout St. Lawrence: Beaches are eroding and more communities are at risk of flooding. Societies must adapt.

One of the main approaches proposed to adapt to the effects of climate change is “nature-based solutions”. These are coastal protection systems designed to include or mimic natural ecosystems to protect and stabilize the coastline.

An example where nature-based solutions have been applied is in Forillon National Park, where hard infrastructure protecting a road had disrupted the natural coastal dynamics and caused the loss of the local beach. Scientists worked with the park service to move the road away from the shore and rebuild the beach to allow the beach to return naturally.

Another example is the realignment of the Belcher Street seawall in Nova Scotia. For this project, researchers worked with farmers and local governments to move a levee to divert floodwater from the local community to areas that once stored water overflowing from the river. This also allowed the water to return to the floodplain, restoring the local wetland ecosystem.

An interdisciplinary and participatory approach

Nature-based solutions are not just about planting plants and walking away. It is a comprehensive system based on a multidisciplinary and participatory approach that requires working with local ecosystems, communities and economies to find solutions.

This can range from protecting local wetlands to greening hard infrastructure to increase ecological value, for example creating habitat for oysters and fish species.

Our research team is busy testing solutions developed jointly by interdisciplinary groups in our large wave channel. This channel, the largest in North America, allows us to test and optimize solutions and technologies in a controlled environment before implementing them in the real world.

For example, we are currently investigating how restoration of coastal marshes can protect against coastal erosion and reduce wave energy. With the knowledge gained from the experiments, we can develop guidelines to help engineers incorporate marsh restoration into future projects.

Customize solutions for St. Lawrence

In general, the biggest challenge in implementing nature-based solutions is the lack of understanding and guidance regarding their performance in cold regions like Canada. Internationally, several guidelines have recently been published, but they tend to be high-level without specific details on how to implement them.

Therefore, as researchers, we must test solutions that are relevant for St. Lawrence, in the laboratory or in simulation models to predict how they will react in reality.

It is also important to establish comprehensive and interdisciplinary monitoring programs after the implementation of these solutions to develop a deeper understanding of how they work.

Act now to solve tomorrow’s problems

To face an uncertain climate future, it is important to aim for proactive planning. Nature-based solutions are complex and time-consuming to develop, as they require an understanding of the entire system. The search for funding to implement pilot projects is also time-consuming. The search for innovative solutions therefore requires time and different skills, especially of the local community.

Although provincial and federal governments have begun to implement long-term programs that integrate sustainable solutions, it is important to realize that the breadth of the St. Lawrence is now eroding and will continue to erode.

We must act quickly to solve tomorrow’s problems.

Jacob Stolle, assistant professor, coastal and river hydrodynamics, National Institute for Scientific Research (INRS) and Damien Pham-Van-Bang, associate professor, National Institute for Scientific Research (INRS)

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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