We have forgotten what a “natural” river looks like.

Britain’s rivers are in the spotlight due to an untreated sewage crisis and the pendulum of floods and droughts that are the hallmark of a warming world. But hidden in these political debates is a pervasive and underreported problem: People have simply forgotten what a natural river looks like.

This is important because it supports attitudes about the kind of rivers people expect to live by, and thus limits changes to the rivers people will be willing to accept. Scientific evidence suggests that radically different looking rivers are needed to cope with larger and more frequent floods and droughts, to increase biodiversity and store more carbon.

Why have we forgotten what our natural rivers look like? In the UK and most other developed economies, the network of streams and rivers has been managed, and in some cases physically modified, for more than 1,000 years to support more farms and later more industry.

It’s no wonder most people don’t realize that the rivers they grew up in, fish, swim or just walk in have nothing to do with the natural ecosystems they once were. History and culture have evolved around modified river systems.

In Britain, for example, 1,000 years of change has meant that 97% of rivers are broken up by barriers such as weirs. Things accelerated after the First World War with 36% of England and Wales’ river network, some 35,500km, undergoing major changes. And these are just the documented changes that much more were regularly maintained, such as the yearly removal of silt or vegetation.

Barrier in the river in the countryside
Have the dams of our natural river disappeared? Almost every river has at least one barrier like this one.
JoeEJ / shutterstock

In the early 1990s, I visited all the flood defense offices in England and Wales as part of a study wondering how much sediment is being removed from rivers, how much it cost and why we were doing it. It became clear that it was expensive and in many cases it was done simply because that is what happens on the 15th of October and woe betide you if you were late because the locals expected it. This expectation of river cleanup is still evident today in calls to dredge rivers after a major flood or sometimes to push gravel back into them.

There has been some increase in river restoration (or remodeling) with over 2,500km restored in the UK since the early 1990s. However, this represents less than 3% of the highly damaged river network and much more needs to be done. Although the sewage crisis dominates the headlines in the UK, the physical modification of rivers is also important.

Physical form of a river

A river’s appearance isn’t just aesthetic: things like the number and shape of channels, gravel banks and sandbanks, or the presence of vegetation or an eroding bank, influence how it acts as an ecosystem.

More complex and disordered rivers tend to store and slow the flow of water, sediment and nutrients. This creates a better habitat for plants and animals. It also means that these rivers do not deplete as many nutrients from the surrounding landscape and are able to store more carbon in the form of both living and dead plants (like peat, for example). Messy rivers release water slowly like a sponge, protecting against both floods and droughts.

Neill Mitchell
River or canal? The River Dee near Chester certainly didn’t look like this before humans arrived.
Neil Mitchell/Shutterstock

That said, modified rivers can provide efficient transportation of bulk cargo by ship, can protect against flooding in some cases, and provide hydroelectric power and food security for millions of people. Restoring more natural rivers therefore involves trade-offs. As early as 2004, a government report concluded that the UK needed to do something other than build higher and more costly flood defenses in the face of a future of more extreme and frequent flooding. But all too often these discussions ignore the many benefits of more natural rivers.

One option is to work more with nature to get benefits from our rivers and floodplains that aren’t simply based on food security, home construction, or flood protection. People want to interact with nature and recent studies show it’s good for you. But first we must learn to tell the story of how our rivers got the way they do and why natural rivers can be good for all of us. At least a better understanding of what we have lost and what the alternatives might be will offer a more balanced argument for or against more natural rivers.

Britain’s riverside landscape is the product of centuries of change. Some of these are here to stay nobody is suggesting turning London back into a floodplain again, for example, and we still need food and property to be protected. But we also need a more sophisticated understanding of why allowing some rivers to return to their natural shape and processes is vital to our future and the future of our ecosystems.

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Image Source : theconversation.com

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