The Senne on 5 October 2021. ©Bruxelles Environnement

The Senne returns to Brussels, hoping to clean up its reputation

If you ever visited Brussels, chances are you walked on top of its Senne river. You just couldn’t see it, hidden as it is, several metres underground.

The Senne along whose banks the Belgian capital developed and blossomed for a thousand years, disappeared from view between the 19th and 20th centuries. It was encased in giant pipes below the surface to protect residents from the rivers’ filthy waters and frequent floods.

Society has gone through some great transformations
— Benjamin Thiebaux

Now the reopening of a section of the Senne is marking the river’s comeback, anticipating a new era that may heal the waterways’ fraught relationship with Brussels residents.

©Bruxelles Environnement

From smelly to beauty queen

Unkindly known as ‘Brussels’ sewer’, a 200-metre portion of the Senne peeked out to see the light in northern Brussels on 5 October, after about a century and a half in the captivity of darkness.

With its clean waters now gently flowing and flanked by lush vegetation, the river was almost unrecognisable from the insalubrious version of itself whose memory is indelibly marked in black and white photographs.

Until the year 2,000, we used the Senne as a sewer
— Benjamin Thiebaux

So much has changed since those pictures were taken in the late 1800s, and the reasons for concealing the river are no longer there.

“Society has gone through some great transformations,” says Benjamin Thiebaux, the Project Manager who led the Senne reopening task force for Bruxelles Environnement, Brussels’ Environmental authority.

“Until the year 2000, we used the Senne as a sewer. Then the European Union said ‘Enough, you can no longer throw the city’s wastewaters directly into its river. You need to clean those waters and ensure that the river and its tributary are in good health and reach good biodiversity levels,’” adds Thiebaux.

Thiebaux is referring to the EU Water Framework Directive that urges states, cities and associations to clean up previously polluted rivers, lakes, groundwaters and bathing waters.

A detail of the Senne’s waters after the clean-up operation.

Swimming back to life

However, the cleanup operation and the two water treatment stations that have been cleansing the Senne’s waters over the past two decades can only go so far.

Until the river is trapped in its underground concrete armour, life can’t prosper in it, says Thiebaux: “The only way to do so is to guide the Senne back to the surface to bring up oxygen, light, and eventually life.”

We know that in cities we can have so-called ‘heat islands’...Bringing water back to the urban centre will allow us to lower temperatures
— Benjamin Thiebaux

With that in mind, for the first time in decades, Bruxelles Environnement returned the river back to the open air on 5 October. This complex operation took one year of work and the demolition of 1,996 tons of cement; previously wrapped around the Senne, the material has been recycled and used for the construction of new river banks in this location.

Albeit limited in scope to the reopening of one 200-metre long section, the project is bound to bring a cascade of benefits, not least to combat the effects of climate change.

“We know that in cities we can have so-called ‘heat islands’; that is, areas that are warmer than others located outside of urban areas. Bringing water back to the urban centre will allow us to lower temperatures in the city because water is cooler,” Thiebaux explains.

The reopening of the Senne on 5 October 2021

With the reopening of the Senne, residents will also be able to walk and relax along its banks as well as enjoy the new landscape.

What’s more, Brussels environment experts hope to foster the creation of a natural haven, help restore biodiversity here and allow animal species to prosper.

Some have already made an appearance. “In 2016 and 2019 we’ve noticed that some fish have returned,” says Thiebaux. “We know that they’re fragile, that this habitat is not yet ideal for them. We’re working on projects to improve the environment so that we can strengthen fish’s presence and help them come back,” he adds.

A long makeover

This year’s Senne recovery operation is only a prelude to what lies ahead. The river still mostly flows underground, sheathed in cement tubes.

After the installation of treatment stations in 2000 and 2007, waters are cleaner and more hospitable, but a great deal of work is still necessary before the river can be fully revived, Bruxelles Environnement experts say.

Benjamin Thiebaux, the Project Manager who led the Senne reopening task force for Bruxelles Environnement.

Fostered by modern needs and environmental constraints, the changes are bound to reshape Brussels residents’ relationship with its river.

Brussels’ cradle

Much like the Seine in Paris – with whom it shares a similarly-sounding name but no other connections – the Senne fostered Brussels’ growth and development, providing the right environment for urban life to prosper.

From the Early Middle Ages, around the year 1000, people started to move to Brussels and build homes along its banks. Incoming and outgoing goods travelled along the river.

Commerce grew, craftsmen multiplied, and windmill blades scooped away the Senne’s water, providing energy for local consumption.

As the population expanded, so did its needs; eventually, the river became overwhelmed by the job that would condemn it to its end: receiving wastewaters from Brussels and the villages around it.

The task proved too much: by the 19th century – with the city now counting over 140,000 people – the Senne had become an open-air sewage and a health threat. Its waters were dragging along dirt, human decay and industrial waste, spreading terrible smells, cholera and other diseases, especially among the lower classes that resided closer to the river.

Adding to this intractable situation, the floods that had afflicted locals for centuries became more frequent, further fuelling residents’ discontent.

The new Senne

The Anspach revolution

In 1867 Brussels’ Mayor, Jules Anspach, took the situation in hand and presided over a new urban planning, effectively declaring the Senne’s demise.

Anspach became the architect of an unprecedented operation that diverted the river and encased it in giant underground pipes; over time, new constructions multiplied above ground, taking the river’s place.

A first phase launched in 1871 to vault the river in the north and central Brussels addressed the most pressing health and flooding issues in those areas but left out other parts of the city and its periphery.

A second undertaking launched in 1930 and completed in 1955 sealed the Senne into underground collectors in all remaining districts, effectively finalising the river’s disappearance from the surface.

A cautious reception

Today’s reopening of the Senne didn’t come in response to popular demand, says Thiebaux, because most people don’t even know it existed or have never seen it.

For those who still remember the river when it was flowing in town, the waterway “may be hidden, but its memory is not,”, he adds.

“When we talk about the Senne to people who have been living here for a long time – and that’s a problem for us – they still think of it as sewage. They’re afraid that it will collect waste again, that it will have a foul smell,” Thiebaux remarks.

“So we talk to them and show the construction sites, the walking paths that we’ve created. There are no bad smells there and we have fish, ducks, frogs. It’s very cool.”

Daniela Berretta Eurocities Writer