I grew up on the serene riverbanks of rural West Bengal in India, alongside the Ganga (Ganges) River. This majestic waterway stirred in me a passion the way rivers influence and are influenced by their environments led me to explore fluvial geomorphology.

Suman Bhattacharyya is a PhD candidate at the department of geography at the University of British Columbia.

I could not have guessed as a child playing on the banks of the Ganga that it would bring me to Vancouver and its own majestic Fraser River. As a UBC Sustainability Scholar I had the opportunity to work this summer on a project focused on gravel mining’s impact on salmon habitat and identifying potential flood management strategies for the Chilliwack/Vedder River—a completely new and eye-opening experience for me.

What are the impacts of gravel extraction on salmon habitat?

The Chilliwack and Vedder rivers, tributaries of the Fraser River, are crucial habitats for various salmon species, including chinook, chum, coho, and pink salmon. The Chilliwack River flows into the Vedder Canal, which plays a key role in the river system’s management and flood control.

This system faces unique challenges in protecting salmon habitats while managing floods. Gravel mining is prevalent in this basin, historically carried out to meet local gravel demands and maintain flood levels designed for rare, significant events. Historically expected once every 200 years, such cataclysmic events are happening with greater frequency as our planet warms and climate patterns become more unpredictable. Since 1990, the Vedder River Management Area Committee has overseen gravel removal from the waterway.

Once conducted annually, since 1998 gravel removals have been conducted every other year to address concerns about the destruction of salmon habitat every other year when pink salmon are returning to spawn. 

An angler on the Vedder River. Photo by Kelsey Van Steele.

As a physical geographer working with the Watershed Watch Salmon Society, my research over the past few months has focused on the adverse effects of gravel mining on salmon habitats and exploring natural flood mitigation techniques as alternatives in this delicate ecosystem.

Numerous studies show a direct link between mining activities and their impacts on salmon habitat. Gravel removal, whether part of a flood-control plan or to meet local construction needs, alters the riverbed and disrupts the natural flow of sediment, degrading spawning habitat in the river. On top of that, the removal of logs and woody debris to facilitate gravel extraction destroys essential shelter and hiding spots for young salmon.

And it’s not just salmon directly. Gravel beds support a diverse community of invertebrates, which serve as a primary food source for young salmon. Increased fine sediment and silt during and after gravel removal can clog gravel beds, reducing oxygen availability and increasing egg and alevin mortality rates.

What are some other options?

One key strategy is reconnecting floodplains. By re-establishing natural river-floodplain dynamics we allow rivers to access their floodplains during high-flow events. This dissipates flood energy and creates diverse habitats for salmon without destroying their critical spawning grounds through gravel mining.

A massive gravel mining project in Chilliwack’s Vedder River will damage important pink salmon spawning habitat. The amount of gravel to be removed from the river, an estimated 360,000 cubic meters, is over three times more than what has been taken in the past. Please send a letter to the Minister of Environment asking him to either cancel the project or scale it back. Your letter will also go to the Minister of Water, Land and Resource Stewardship, Nathan Cullen and Parliamentary Secretary for Watershed Restoration, Fin Donnelly.

Recent research published by the UBC Department of Forestry suggests that reintroducing the historical Sumas Lake as part of a flood adaptation strategy could be a viable option. Diverting high streamflow from the Vedder Canal to the Sumas Prairie,a historical floodplain system, could be an effective solution for the Lower Fraser region. This approach would require the acquisition of strategic properties to allow flooding and relocating people and infrastructure to areas outside floodplain. While it may seem challenging in the densely populated area, it could be more cost-effective compared to investing in traditional flood infrastructure, such as dikes and pump stations. It has the added benefit of offering a way to potentially rectify historical injustices.

The contrast between my childhood home along the Ganga River and my current home near the Fraser River is striking. In West Bengal, rivers are deeply integrated into life and culture. Though they face significant environmental pressures – such as illegal sand mining – flooding is a common phenomenon and the ways communities adapt to it are quite remarkable. The concept of “Living with Floods” practiced in flood-prone regions like West Bengal and Assam provides valuable insights that could be applied elsewhere, particularly given the anticipated increase in flooding due to global warming. The practices I saw growing up have been instrumental in my current research, helping me apply what I learned in a new context that supports salmon conservation efforts in B.C. 

Our goal is to restore the river’s natural balance and improve conditions for salmon and other aquatic species to thrive. This involves advocating for stronger regulations and more rigorous monitoring to ensure that mining activities do not harm the river’s health.

Research specifically on the impacts of gravel mining on salmon is limited. The effects on salmon survival and populations are often unclear due to the difficulties in conducting long-term studies and maintaining consistent monitoring efforts.

We need to foster more collaboration between scientists, policymakers, and local communities. Combining traditional ecological knowledge with scientific insights is key to developing effective and sustainable river management practices. Whether British Columbia or West Bengal, by working together, we can better address the complex issues facing our river systems and ensure their health for future generations.

Suman Bhattacharyya is a PhD candidate at the department of geography at the University of British Columbia. His research interests include studying and modeling the impacts of climate change on river flows, with a particular focus on extreme events like floods, and identifying their changes and drivers.