Daylighting is the process of uncovering a river that has been buried underground in a pipe or tunnel and bringing it back to the surface. Many water courses were originally covered over when they became polluted after the Industrial Revolution.
When a lid is taken off a river, sunlight is let in. This means that plants can begin to photosynthesise and a habitat can be established. Fish can also be accommodated by making adjustments to a channel. Quite often, because those who originally culverted a water course were thinking of it as a drain rather than a stream or river, there can be a pipe or jump that makes it impossible for fish to pass through, or it can be very wide, which allows room for flood water but means it’s too shallow for fish.
Daylighting also decreases flood risk. Originally, a lot of culverts were put in to tackle flood risk, but now we know that this isn’t really a good solution and in many cases, it makes the flood risk worse as culverts are vulnerable to collapse or blockage. During the 2012 floods, a block of flats in Newcastle had to be evacuated. Nobody knew that there was a lost river
in a pipe underneath. When a big storm caused the culvert to collapse, the river washed the foundations out from under the building and it was effectively left on stilts. Now they’ve spent several million pounds demolishing the flats and rebuilding them with a new culvert underneath rather than perhaps redesigning the site around an open stream.
Daylighting can also inadvertently improve water quality – by bringing pollution within sight of the local community. And open streams and rivers can also help to cool down urban heat islands, and bring many other economic and social benefits, such as improved health, although these can be more difficult to quantify.
If a stream or river can’t be physically daylighted, it can be culturally daylighted, by uncovering people’s awareness of it. Perhaps glass panels can be placed in the top of a culvert so people can see the water, or people’s attention can be drawn to its presence with signs or art works. In some places, there have been living-river walks, where a group of people all dress in blue and follow the route of a lost river.
It might not be the end solution, but generating awareness of a lost river makes people think a little more about pollution, and the fact that whatever goes down the nearest drain might end up in their hidden river. When community groups become aware of a lost river it can lead to them putting pressure on town planners to create development designs around a daylit river, perhaps including waterside apartments or riverside walks that can benefit the whole community. Awareness might not seem like much to begin with, but it’s actually the start of everything.
For my PhD I’m looking into captured streams – smaller waterways that have been diverted completely into the sewer system. That means a stream of clean water is unnecessarily going through the entire sewage treatment works. That reduces the capacity of the system and has a big knock-on effect in terms of water bills. Nobody is really sure how many captured streams there are, but Zurich – which has restored more than 15 kilometres of buried water courses – found that 15 per cent of the water reaching sewage works was from springs and captured streams.
Hunting for lost rivers is a case of trawling through old maps and written accounts to find mentions of streams. The contours of the land are also important. I use a contour map and GIS software to model the flow paths of streams. The software maps where water would run if it flowed naturally down a landscape. When these are matched up with historical maps, in most cases it fairly accurately predicts where hidden valleys are located, ones you might not even see on a normal map, or if you were standing in the area.
My hypothesis is that you can test for the presence of a captured stream within a city sewer because the tap water piped from outside the city will have a different chemical ‘fingerprint’ to the local ground water. I’m currently finding out if that’s true. It has involved collecting sewer samples once in the day, and once at night – at 4am when most people are in bed so there’s likely to be very little wastewater in the pipes and what’s left should be captured streams or other infiltration. I’ve been sampling day and night for the past three weeks and then analysing what I collected in the lab while it was still fresh, so I’ve not had much sleep.
Do you know of a daylighting project? You can add it to Adam’s world map of daylit rivers at www.daylighting.org.uk.
1987 Born in Gloucester
1999–2006 Attended Sir Thomas Rich’s School, Gloucester
2008, 2009 Summer intern at Water21, a Gloucestershire-based not-for-profit organisation that advises communities and landowners on flood and drought protection
2009 Awarded a BSc in geography from University College London
2010 Awarded an MSc in environmental water management from Cranfield University
2010–present Teaching undergraduate and Masters students, University of Sheffield
2010–present Studying for a PhD at the Catchment Science Centre, University of Sheffield
This story was published in the February 2014 edition of Geographical Magazine