Climate AdaptationDaylighting Rivers: A Hidden Gem of Climate Adaptation

Daylighting Rivers: A Hidden Gem of Climate Adaptation

Karl Dickinson
Karl Dickinson
Change matters. It takes courage. As a writer - and citizen - I am inspired by stories of those who challenge the 'we've always done it this way' attitude. We can do better - it's time to listen to those who go against the grain.

Urbanisation in the post-industrial age led to the burial of waterways to make way for buildings, roads, and public spaces. Water, though, cushions the blow of climate change, so many cities are raising channels from the deep. It’s expensive, but the benefits pay dividends many times over.

In autumn 2024, images of cars piled up in the streets of Valencia, Spain, sent shockwaves through the international media. It seemed undisputable that climate change had come knocking at western Europe’s door.

The cost in human lives throughout the region exceeded 200, while the cost to insurers for the cleanup operation is expected to exceed $3.8 billion USD.

Flooding is a visual disaster. We see the disaster unfold and the aftereffects when the waters subside. This may be why the press fixated on damaged cars. This was altogether easier to depict than human suffering, and it stirred up more emotion than the 40,000+ European deaths caused by heat each year.

Much of the blame for Valencia’s deluge of mud and water has been heaped on ineffective early warning systems, giving the signal to evacuate too late. That could have saved lives, but wouldn’t have prevented the destruction.

Sensibly, some observers have urged Europe to learn from this disaster and invest in climate change mitigating infrastructure. The tragedy in Valencia is that existing protections did exist but have gradually been decommissioned. Some argue that it was not volumes of stormwater but the removal of dams in surrounding areas that condemned the region to drown.

Where Should All the Water Go?

There’s an irony that these dams were put in place after the last great flood in 1957.

It was this that also prompted authorities to divert the flow of the river, which cut through the city, further away from the centre.

In a turn of public triumph, the reclaimed land was not turned into a motorway, as originally suggested: it became Turia Gardens, an urban park stretching 9 km through Valencia, including the scenic old town.

It has become a tourist attraction in its own right since implementation in the early 1980s, but for locals it is a space for events and a green refuge on a hot Spanish afternoon.

Did this benefit Valencians during the flood? We don’t know categorically, but the ingenuity of leaving a drained riverbed sunk into the city may have acted as a kind of basin for some of the stormwater. It’s a concept replicated at Benthemplein square in Rotterdam, the Netherlands, where heavy rainfall is diverted to, stored in, and gradually released from in a safer, more controlled manner.

Turia Park absorbed some of the downpour that would have inundated buildings, sewer overflows, and similar essential infrastructure even more without it, although due to the amount of sedimentation filling the channel, it’s capacity for mitigating flood was admittedly decreased.

Daylighting - CityChangers.org
Turia Park beautifying Valencia. Image credit: iStock / agaliza

Water: A Hidden Enemy

Incidents like this are a reminder of the significance of nature in urban environments. It can be creator, destructor, or saviour – water especially.

It’s likely not to have crossed your mind as you wander the asphalted streets, but where we walk there were once streams, brooks, and rivers, a network of veins that drained water from the land, known as the bluebelt. When the Industrial Revolution arrived, transportation of goods shifted from canals to rail, making waterways – natural and human-made – obsolete and a waste of valuable space in economic terms. Add the boom in manufacturing and urban populations, coupled with poor sewage systems, and cities found they needed to cover waterways to hide an onslaught of pollution and disease.

This continued into the twentieth century. Melina Scholefield, who led Vancouver, Canada’s, Rain City Strategy, told us of a trend for redirecting inconvenient waterways through drains, culverts, and underground pipes as quickly as possible. Earth’s most valuable resource was treated like a waste product, shifted to outlets that emptied into distant rivers or seas.

Left undisturbed, the natural bluebelt would help shift stormwater away from harm. As increasingly seen year after year, if water isn’t given a route straight outta Dodge, it stays, and it destroys.

Which explains a recent trend in city planning for what’s called ‘daylighting’.

Reviving Urban Rivers: A Well of Examples & Benefits

Lauded as an effective nature-based solution in the fight against climate change, daylighting makes water visible again: bringing urban waterways back to the surface where they can be admired, used, and serve as habitats for local wildlife.

Deculverting, removing pipes, and deconstructing weirs that straighten channels also restores a more natural flow, which has many benefits.

For one, it flows slower, helping to restore greenery. A channel lined by green corridors attracts biodiversity, but also acts as a sponge, with vegetation sucking up a load of water as it passes.

This can alleviate flooding and increase volume capacity compared to the confined space in pipes causing a bottleneck and buildup upstream. Plus, open-air streams can rise and fall – at least, up until they burst their banks, buying time before flooding kicks in.

Daylighting in Action

Revealing and reviving once-obscured waterways can be combined too with ponds and pools. This is part of the daylighting programme that has uncovered 21+ km of narrow watercourses in Zürich, Switzerland, since the late 1980s. This proved to relieve demand on sewers and associated costs of water treatment.

In Sheffield, England, deteriorating concrete structures pose a danger and raise a potential greater threat of flooding. Ageing culverts are expensive and difficult to maintain, writes Simon Ogden, chair of the Sheffield Waterways Strategy Group. One collapsed in 2016, taking part of a carpark with it.

This was jumped on as an opportunity for daylighting the River Sheaf, complete with added park for the public enjoyment. Realistically, there’s scope for much more; the Sheaf still disappears under Sheffield’s main railway station, but enthusiasts have instead concocted a plan to glimpse the river via a lightwell from the platform.

Over in the USA, a project in Trenton, New Jersey, aims to create the Assunpink Greenway Park through the reemergence of the Assunpink Creek. This was delayed due to the COVID-19 pandemic, but is still the plan to regenerate a former brownfield site – what the Environmental Protection Agency describes as a chance “to fix an eyesore in the middle of downtown”.

Daylighting - CityChangers.org
A stream in Bad Wildbad, Germany. Image credit: Pexels / Joerg Hartmann

The Living Daylights

Indeed, the return of nature to urban centres is a major attraction of daylighting. It isn’t always combined with greenery, but when it is, the blue-green infrastructure appeals to our instincts – an innate ancestral longing for the look, smell, and feel of the wild.

It’s good for our physical wellbeing too. Vegetation and water have cleansing properties, helping draw out fresher air from a polluted atmosphere. A white paper from the organisation American Rivers states that streams are useful for removing unnatural nutrient pollution, and for making them less harmful to aquatic wildlife. Evaporation from exposed surface water cools the surroundings, mitigating the urban heat island effect.

For some, rediscovered streams are also a place to swim – it’s hard to do that on a motorway!

Refreshment for the Seoul

Some bright spark in South Korea must have been aware of all these advantages. The Cheonggyecheon river in Seoul, the peninsula’s democratic capital, is held up globally as a shining example of the daylighting.

This 11 km-long stream now flows where a domineering elevated highway once bore down on the people below, where the roar of engines would have throbbed had the traffic not been at an almost standstill for much of the time, Dr Soo Hong Noh tells us.

A professor of Yonsei University in Korea, who was involved in the redevelopment, he told CityChangers that the original tributary for the larger Hangang River was incrementally covered between 1932 and 1972 as the city’s economy and population exploded. Topped off with sewer lines, he remembers it being “dirty, smelly”.

Impacts of Seoul’s Daylighting Megaproject

The road was removed in 2003. Now it attracts more than 60,000 people each day, which, he says, is good news for the 60,000 stores that run the length of the stream, employing in excess of 200,000. Good news for everyone in fact: although the stream channel is artificial and clearly lined with concrete, it would hold enough rise in water to prevent a once-in-200-years flood event. The biodiversity increase is significant too, at 639%.

Dr Noh shares some further data on the impacts for the districts the river is seen in: he says that “pedestrian activity increased by 76% after the restoration”, while the vehicle volume decreased by 45%. He also notes an “increase in bus ridership by 15.1%, and subway ridership by 3. 3%”, as well as a 10% decrease in air pollution.

But Dr Noh is also a family man who talks of his grandchildren “catching minnows in the stream” or watching the big cranes who reside by the river. “It’s a few meters from you. It’s amazing. I think that’s most rewarding to me, watching how they enjoy the restoration.”

Daylighting - CityChangers.org
The Cheonggyecheon river revitalisation in Seoul, South Korea. Image credit: Unsplash / Sandi Benedicta

The Cost of Daylighting

In the 1950s, people turned out in droves to protest against turning Valencia’s former river into another high-volume motorway, and half a century later to celebrate the groundbreaking for the Cheonggyecheon project. Shows like these are a clear mandate for city leaders to restore urban waterways.

It comes at a price, of course. Valuable city centre land could bring in big bucks for a municipal administration were it sold for real estate. With daylighting, where existing structures must give way for the river, almost the opposite is true: one uncovering project in New York City, USA, is expected to come in at $133 million USD per mile because of the need to acquire real estate sitting on the river’s path. Other sources quote “a general rule of thumb of $1,000 per linear foot of daylighted stream”, because deculverting and landscaping is specialist and labour-intensive work.

It can pay off, though, and not just in green capital, health, and happiness.

Costs of Daylighting Pay Off

According to the Smithsonian Magazine, daylighting was incorporated into a regeneration project that started in 1995 in Kalamazoo, Michigan, where an investment of $18 million “has yielded hundreds of millions of dollars in private investment, increasing the city’s tax base”. A 2020 update on excavating the river Mark in the Dutch city of Breda from beneath car parks found that, with just two-thirds complete, the shift had led to an additional investment of €200 million in real estate along the river, about a 15% increase in spending and close to 300 extra jobs.

If nothing else, then the knock-on features of daylighting can help cities meet their government-imposed obligations to respond to the climate crisis. But if it helps prevent flooding in future, the upfront outgoings could come in cheaper than a cleanup operation or two, and definitely prove worthwhile in terms of lives saved.

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