Carlow concrete spaces given over to 'rain gardens'

Carlow has become the first county in Ireland to green its concrete spaces by retrofitting ‘rain gardens’ to improve water quality, reduce the risk of flooding and improve biodiversity.

Four nature-based solution projects have been completed within Carlow town, including one located on the Old Dublin Road, which features eleven rain gardens.

These gardens collect and filter surface water runoff and reduce the volume of surface water flowing into the traditional sewerage system.

“We wanted to reduce the amount of hardscape areas in Carlow town and investigate innovative measures that would both improve the aesthetics of the streetscapes and reduce the risk of surface water flooding,” said Barry Knowles, Senior Executive Engineer of Carlow Municipal District.

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“We were the first local authority to implement retrofitted raingardens in an urban streetscape.

“We couldn’t increase the area size because we were working adjacent to roads, so we had to retrofit the spaces we took from the hardscape, before greening and softening them.

“The idea is greening the grey - we’re introducing a rural element into an urban environment.”

This initiative is being showcased as part of #YourCouncilDay on July 5, which highlights the role of county and city councils in supporting people in their daily lives.

Each rain garden comprises a 400mm deep, free draining soil mix that cleans, stores and conveys runoff water to a drainage layer.

Completed in March, the Old Dublin Road project was planned, designed and managed in-house by Carlow Municipal District Office, through collaboration with Local Authority Waters Programme, and complements Carlow’s Climate Action Plan.

“In addition to environmental benefits, rain gardens have economic benefits, as they make Carlow more attractive to businesses,” said Mr Knowles.

“There are social benefits as well because people feel happier living in a greener landscape, rather than somewhere grey, hard and mundane.”

While evaluation of the project will continue over the next twelve months, early benefits include proven surface water capture and infiltration, with reduced pressure on down-stream sewer and local watercourses, such as the River Barrow.

Inlets in the kerb direct surface water runoff towards the rain gardens from the street, with existing gullies retained as an overflow mechanism if the gardens reach capacity.

“Most of Carlow town’s surface water enters road gullies which outfalls to combined sewers, consisting of surface water and foul water.

“In times of storm events, these sewers are designed to overflow to adjacent water bodies.

“The rain gardens reduce the surface water entering the combined sewers, reducing the risk of sewer overflow into local watercourses, thereby improving water quality.”

Suitable trees and plants were selected for the fluctuating conditions of the rain garden to enhance local biodiversity.

Such innovative projects have drawn international attention to Carlow town, which will be the only large urban town to represent Ireland in the Entente Florale Europe competition on July 12.

This prestigious Europe-wide environmental competition for villages, towns, cities, communities and public bodies highlights the importance of the green environment for quality of living.