Meandering Streams: How Natural Curves Support a Healthy River

Have you ever noticed the way the Elk River curves throughout the land in braided, wavy, snake-like patterns? Those bends are an important part of a natural, healthy flow of a river. Roughly 14,000-10,000 years ago, powerful glaciers carved our flat-bottomed U-shaped river valley. The wide floodplain leaves a lot of room for meandering, and while the source and destination stay the same, its path evolves and carves diverse habitats.

Slow Moving Water
In the valley bottom, the slope of the land is gentle, causing the water to flow slowly. Slower moving water gives the river time to curve, erode its outer banks, and deposit sediment along the inner bends. Like a running track, the outside of a bend is a longer distance, so water has to move faster to make it around: fast water carves out the riverbank. On the inside, water moves slower, and sediments have time to settle out. Small undulations slowly get carved into large riverbends, and this is what creates that familiar meandering pattern. As the river wanders it creates new pathways that lead to side channels, wetlands, and oxbow lakes. 

Benefits of Meandering
The side sections aren’t just leftover water, they’re essential ecosystems! Wetlands are spaces of remarkable biodiversity. They range in habitat from shallow water, mud, and vegetation, all of which works together to provide homes for fish, amphibians, birds, insects, and mammals. These bodies of water also play a crucial role in water management. Wetlands act like sponges that absorb excess water during floods - the plants work to retain water that would otherwise overflow into unwanted areas such as urban zones and roadways. Furthermore, the plants and mud help to filter sediment, nutrients, and pollutants from the water, making them great natural environmental cleaners.

The Power of Trees
Vegetation along the streambank shapes how rivers meander. Tree roots work to hold together the soil, limiting how quickly water along the outer bank erodes the bank. Research shows that stream banks that have been clear cut have higher erosion rates. While slow channel changes are good and diversify the habitat, quick erosion can increase sediment levels to the point of damaging ecosystems. Excess sediment fills gaps in the stones at the bottom of the river which usually provide safe havens for water bugs and fish eggs.

Although overhanging trees or branches may be hazards for river users, they actually add ecological complexity to the river. Fallen wood slows the current, creates sheltered spaces for fish, and adds nutrients to the water. Moreover, extra shade helps to keep water temperatures nice and cool, just how the fish like it.

Let Natural Curves Be
Meandering rivers are nature at work, creating balance for aquatic life and the landscapes around them; but they’re inconvenient for humans. Our permanent infrastructure (i.e., roads, buildings, railroads etc.) relies on a stable environment, so we use stones, dikes, retaining walls, and other artificial riprap to prevent erosion. This causes river channelization, and you only have to look at an example like the Rhine River in Germany or streams between Penticton and Osoyoos to see what channelized streams look like. 

Wetlands give way to farm fields and roads, and past stream meanders are only seen through property lines and faint groundwater channels. In channelized streams, with no wetlands and backchannels, the water has nowhere to go but through the channel. This means that during intense flooding events, the power of moving water (and therefore the damage potential) is greater. 

At the end of the day, it’s not viable to let the river meander wash away expensive infrastructure, and riprap is often necessary. We should at least consider the importance of the river meander, and work with nature, not against it, whenever possible.