Two decades of change: the land

This is one of a series of articles using satellite imagery to chart the changing face of Fraser Valley communities—and the land on which they sit.

Previously: Abbotsford | Langley | Mission | Chilliwack | Small towns

If you want to learn about how to use online tools to explore changes across the Fraser Valley, please become an Insider Member. When the series concludes, Tyler will give members a step-by-step guide to how they can use the same techniques to survey changes in their neighbourhood, or across the world. Become an insider here.

Human change is quick. Change on a geologic time scale takes much longer to realize. Except, that’s not always true. Indeed, as fast as our communities have changed, the rivers that form the heart of the Fraser Valley may have changed even more.

Even as humans have tried to contain the valley’s rivers, aerial images show how rivers have pushed back, cutting through entire islands and forests, and seeding new ones in their wake.

Crescent Island

Many of the images here involve large-scale significant changes, but this one shows the gradual march of time—and water. Crescent Island north of Glen valley and just east of Silverdale sits at the centre of the Fraser. It’s hemmed in on both sides by dikes, which limits its movement. But even though it is constrained, the slowly evolving shape of the island shows the gradual shifting of the Fraser’s current.

The western end of the island has narrowed as the river has eroded its northern bank.

These images were taken at similar times of year, but water levels vary and throughout this set of images, it’s best to focus on the treed portions of islands and riverbanks. Sandbars illustrate where the water is shallow, but keep in mind that their absence doesn’t mean one does not lurk just out of sight. In the image above, you can see that on the eastern end of the island, the treed portion has slightly receded.

On the north side of the Fraser, you can see improvements to the Silverdale Wetlands.

Chilliwack islands

The Fraser River is constrained by man-made obstacles all across the valley. But it is allowed to run freer—and change directions—more in some places than others.

All throughout this area, the Fraser has rapidly shifted course over the last two decades. The image above shows the changes immediately south and east of the Harrison confluence. The river runs in two main channels here, but the mouth of the southern channel has radically changed over the last 20 years.

We can also see other frequently-changing aspects of river evolution. On the north bank, we can see the river eroding significant amounts of land. We can see that in the southernmost oval as well. In the two remaining highlighted areas, we see islands that had been mostly sandbars begin to grow considerable amounts of vegetation. As river erodes sediment from one area, it drops that material in another place. In such a way, the death of one island helps birth a new piece of terra firma.

The above image, which captures a huge expanse of land, shows that pattern even more clearly. The water in the 2022 image is clearly higher, but what is notable is how islands that had maintained large amounts of vegetation (suggesting they rarely flooded) have disappered under the water, while other sandy ones have sprouted new plants.

In the centre of the image, it appears that a major channel route is increasingly clogged with sand, suggesting the central channel now carries a larger share of the river’s water.

This image, of the river immediately east of the Agassiz-Rosedale Bridge (bottom left) probably shows the most significant change of any along the Fraser River.

It shows the river ploughing an entire new course directly south into the Fraser’s bank. The strength of that bank is notable given how significant the scale of the shift of the main current and the acute angle at which the water hits the earth.

Chilliwack/Vedder River

The Chilliwack/Vedder River (the watercourse changes its name at the Vedder Bridge) shows how a smaller river can also dramatically change course. Just upstream from the bridge, the river has ploughed a new more-southernly route through its narrow valley. That has left oxbows along its northern portion.

At the bottom-right corner, we can see how a shift in the trajectory of a bend can set up changes that occur downstream.

Just downstream of the bridge, the river also shifted. Twenty years ago, the river ran relatively straight. Today, its curves are more exaggerated. But they can only go so far—on its western and eastern edges, the river turns quickly as soon as it hits banks reinforced to protect nearby land and people.

The Hope bend

Note: the grainier image should say August 2022.

Because it’s the most prominent major bend in our area, we took a look at the Hope river’s course near Hope. But the imagery was relatively limited and that which existed doesn’t suggest significant ongoing change. That doesn’t mean nothing’s happening—in four years you can see the river eating away a slice of land on its northern edge and the expansion of a sandbar.

The Sumas dike

Finally, as promised in the Abbotsford instalment of this series, we have a closer look at the Sumas Prairie dike that failed in 2021. In June 2022, eight months after the dike failed and was rebuilt, a large amount of water water still sat at its base. The water was slowly receding though, a second image taken a month later showed.