On Suffolk Street, Council Plans to Pilot Small “Rain Gardens” to Help with Drainage

It’s going to rain more in Dublin in the future, says Adrian Conway, Dublin City Council’s senior environmental engineer.

Climate change is triggering greater rainfall and more severe storms across north-western Europe, he said, at a meeting of the council’s environment committee last Wednesday.

Local authorities need to adapt city streets to cope with that, he said. “We are now adapting to climate change, not future climate change, although that is important, but existing climate change.”

For Dublin City Council, that means looking at innovative ways to use urban design to deal with the extra floodwater on streets, he said – including putting in “rain gardens” around the city, little patches of grass and plants that will soak up some of the water.

From Nature

At the meeting, Conway showed councillors a sneak peek of the new pedestrianised Suffolk Street – just south of College Green – where the council plans to pilot nature-based solutions for flooding.

A small patch of grass with a dip in the kerb that lets water drain towards it can help by “greening the city while also improving drainage and flooding”, said Conway.

In his vision, all future alterations to the public realm – so streets, squares and so on – in Dublin should incorporate these “nature-based solutions” to flooding.

A spokesperson for the council says it is “developing designs for an upgrade of the public realm at Suffolk Street”.

“The plans are at an early stage and following further development and local consultation, they will be brought forward to the planning stage early next year.”

The Problem

Northwestern Europe, including Ireland, is experiencing increased rainfall and will be vulnerable to flooding in the future, according to a major study on flooding in Europe published in the journal Nature this year.

Dubliners can expect more bouts of heavy rain, which the city’s drainage system isn’t designed to cope with, says Conway. “Drainage systems were built on an Irish weather pattern of constant rainfall but low intensity.”

Suffolk Street is a problem area for drainage, says Conway. “A lot of flooding has occurred as a result of our paving of the streets,” he says.

“Suffolk falls down to Grafton Street, Grafton Street falls to College Green and if you are at the bottom of that hill it is not very pleasant,” he said.

Unlike rural surfaces, urban surfaces are sealed. Urban runoff is also polluting, he said. “It’s full of not very nice materials: microplastics, rubber, hydrocarbons.”

Natural Solutions

For Suffolk Street, the idea is simple. “Basically it is a tree and a bit of planting around the tree. The water goes in one side and out the other. It is very simple,” he says.

The drainage system is still there as a backup. But Conway hopes that the tree and planting will soak up some of the water, he said.

In the designs, the pavement in the loading bays in Suffolk Street will also be permeable. That will help, but the green solutions are much better because they soak up water fully, he says.

The council has been talking about doing this for 20 years, says Conway.

“I’d like to get on and do a few of these in the city centre and suburban areas,” he says. “We can’t keep paving over everything and expect anything other than bad outcomes.”

The council should also be working with private developers, encouraging them to include green roofs and walls in their designs and encouraging householders not to pave over their gardens, says Conway.

“We have to show examples by doing things on the public side,” he says.

Rolling It Out

“I’m very impressed with the vision for Suffolk Street,” says Green Party Councillor Claire Byrne. “Have we any indication of how deliverable those solutions are and when we might see something happen?”

The design team are working on the plans at the moment, says Conway. There are plans for Castle Street and Francis Street in the pipeline too, he says.

“Wherever we are doing new public realm we should be doing something to contribute to this,” he said.

Robert Moss of An Taisce asked whether private developers are ever required to use natural drainage solutions, such as rooftop gardens or vertical planting, as part of their planning permission.

“Most private developers are now turning to green solutions even without much pressure,” said Conway. “There are a number of examples of people doing green walls and green roofs, rain gardens, and permeable pavements.”

The council is not requiring them to do it, but encouraging them to do so, he says. “It is becoming more and more of a thing.”

Green Party Councillor Michael Pidgeon, who chairs the committee, says he has seen nature-based solutions working well in Brussels and wondered how the committee could support this initiative.

Conway suggested that each time councillors are presented with a public-realm project, like a street upgrade, they could ask whether it’s incorporating these natural drainage solutions.