Recently, the British Columbia government approved a gravel mining project along the Fraser River near Agassiz. The mining project is meant to mitigate erosion and flood concerns for the local community. This reach of the lower Fraser River, downstream of Hope, B.C. is often referred to as the “Gravel Reach”. The topography and geography of this reach is unique and interesting and can be considered a “wandering river” made up of many islands and side channels. Gravel extraction in this reach has become a contentious issue and flood control in general is often a very sensitive topic – balancing human safety, economics, and environmental integrity.
Over time, the lower Fraser River, like most rivers, experiences an ongoing process of erosion and deposition, and large volumes of gravel from the upper reaches of the river is transported through and deposited here. This is a natural process and the fish that use this reach of the river have adapted to, and therefore require, these gravel bars and side channels for spawning and rearing. Salmon, sturgeon, and a variety of other fish and aquatic organisms depend on these gravels and the unique habitat in this reach of the river.
Extensive development has also occurred along the Gravel Reach of the Fraser over the past several decades and continues to encroach on the river. This encroachment has likely altered the river’s natural processes of sediment transport, erosion and deposition: especially its connection to its floodplain. Floodplains not only store water during floods but also store sediment. When these floodplains are no longer available for these functions, the river can start to fill with sediment. As a result flood lines change and people that have built in these areas are at risk.
To protect homes and infrastructure from flooding, extensive diking has occurred since the 1950’s along the river. Diking interrupts the natural processes of a river including channel migration, erosion and deposition. Some of these dikes are now deficient due to changes to the river and were designed and constructed to a standard that would not be acceptable if constructed today. And so, flood concerns remain, and some groups push for large scale gravel extraction in an attempt to lower the river bed and flood profile. This is an oversimplified solution to a complex problem. In essence, gravel extraction treats the effects of the problem, not what has caused the problem and the results of this proposed work will definitely affect sensitive fish species and will not resolve the problem.
The risk to fish habitat is not necessarily just from the direct impact of gravel mining activities, but in the longer term effects that removing of large quantities of gravel can have on the whole system. As the Fraser River Gravel Reach Studies website of the UBC Department of Geography states, “Experience elsewhere has taught us that when large volumes of gravel are mined from rivers, the river changes dramatically and, with it, the river ecosystem. Our problem, then, is to find a way to manage the river to maintain or improve the existing flood protection while maintaining the ecological character of the river.”
Please click here to read a recent article regarding the gravel mining project.
Please watch the YouTube video below demonstrating how rivers can respond to gravel extraction.
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