Permeable retrofit is a way forward for SuDS

A new era for SuDS management begins this year, so says Jamie Gledhill of Brett Landscaping. Here he explains why permeable paving is key for futureproofing high-risk developments, and what developers and housebuilders need to know.

There is wide consensus across the higher echelons of the construction industry and government that the enactment of Schedule 3 of the Flood and Water Management Act 2010 in 2024 is an important step for the sector. For this to be successful, it will require regular collaboration across a range of regulatory and civic bodies, so housebuilders and developers need to ensure they are working with all partners to find satisfactory solutions to mitigate the risks of flooding on every high-risk development.

This is a significant challenge. The National Infrastructure Commission (NIC) report to the Government in November 2022 identified that there are currently 325,000 properties within England that are in a High Flood Risk area that have more than a 60% of being flooded in the next 30 years. A further 500,000 houses have been identified as being at risk of flooding within the next 100 years. 

As a result of the NIC recommendations the Government is following Wales in enacting Schedule 3 of the Flood & Water Management Act 2010 in 2024. This will require all new developments to introduce SuDS approaches to mitigate their impact on the drainage network and absorb surface water as close to source as possible. 

However, this will also have an impact on developments that require a retrofitted solution to address previously unforeseen issues, or to improve upon the existing SuDS provision on the site.

This is because as well as addressing the UK’s increasing extreme weather events, and issues like water scarcity, SuDS installations will now also need to increase water quality and add features that mimic nature to developments, enhancing biodiversity.

Achieving these new standards does not require reinventing the wheel. It actually allows housebuilders and developers to return to some tried and trusted solutions with the confidence to know that they will help to meet all the new requirements. Take the use of permeable paving, for example. 

While there may be some concern that it doesn’t present as ‘green’ to the naked eye, it is arguably the best SuDS system we have for minimising disruption to residents. Permeable paving works by allowing water to pass through it, rather than running off onto the surface and into the sewer system. Immediately, this decreases the amount of water flowing into a sewer system, reducing overflow.

Permeable paving can also help to improve water quality by reducing the amount of pollutants that are washed into the sewer system. This is because permeable paving allows water to filter through the aggregate packing and silt, which helps to remove pollutants.

There are several different types of permeable paving available, including porous asphalt, concrete pavers, and interlocking concrete pavers. The type of permeable paving that is best for a particular application will depend on a range of factors, including the amount of traffic that the paving will be subjected to and the climate, and that correct installation is key to success. If it is not installed properly, it may not be effective in preventing sewer overflows or improving water quality. 

Finally, because we are living in a time where project managers are under pressure to carefully manage budgets, retrofitted SuDS systems are a good way to help save money by reducing the need for expensive installation of conventional stormwater drainage systems, which can often involve ground engineering. 

When done well, SuDS can help to reduce the risk of flooding from rain and stormwater on a site and the risk of sewers being overwhelmed, by reproducing natural processes for irrigating water. The new requirements placed on housebuilders and developers from 2024 means there has to be more thought about how water moves around a site, and how it can be controlled, but the systems and expertise are already on hand and ready to assist the approach to a new era of SuDS management.

A good recent example is Brett Landscaping’s work with Severn Trent Water on a £76m project to reduce the flood risk on residential estates in Mansfield. Severn Trent and local authorities are working on retrofitting a series of SuDS measures across the town including bioswales, detention basins, raingardens, and approximately 50,000 m2 of Omega Block permeable paving. 

Part of the sustainable flood resilience project involves retrofitting permeable paving, within highway land such as residential parking areas on residential estates to tackle the runoff of surface water. The permeable paving has been designed as either infiltrating with a geotextile base or non-infiltrating with an impermeable liner with a return to the sewer system. 

Jamie Gledhill is engineering technical manager at Brett Landscaping