Paving for a rainy day – By Brian Kent, national technical director at Tarmac 

As many of us Brits are aware, the weather in the UK is famously unpredictable and probably why we’re known for discussing the weather – a lot. Yet, despite high-profile examples of flash flooding and extreme heat, too often our preoccupation with the changing climate has seen little action. 

A lot has changed over the last decade. We are in a climate emergency, with an increasing frequency of flood events and water conservation a priority, and many people and businesses are doing their utmost to make more sustainable choices. 

Following last year’s summer and the reminders to conserve water, it’s no surprise the subject of sustainable drainage systems (SuDS) has been explored further, nonetheless with less precedence than needed, until now.  

It has been a whole 13 years since the Pitt Review first recommended that sustainable drainage systems should be included in all new housing developments. In the intervening period, the legislation required to enforce this approach has not been fully implemented and driven forward as we had hoped. 

A big change for developers – the legislation we’ve been waiting for 

Currently, the planning system requires developers to include SuDS, but only in major developments – those of more than 10 homes. 

In 2024, this will change and mandatory sustainable drainage systems in all new developments over 100m2 – or those including more than one property – will be implemented via Schedule 3 of the Flood and Water Management Act 2010.  

Well-designed sustainable drainage is widely recognised as the best way to manage flooding risks and pollution overflows – both serious challenges faced across the country. 

Modern drainage systems have evolved over the years, meaning developers have much higher quality, proven products at their disposal. This has a two-fold benefit. New builds are better protected against flooding, while slower water run-off supports the stability of the surrounding natural landscape.  

The next generation of porous asphalts  

Tarmac’s UltiPorous range provides effective water management by capturing surface rainwater and holding it back, delaying it from entering local drainage systems.  

The range performs in the same way as regular asphalt but can safely manage rainfall of over 5,000mm / hour. For context, England had a total rainfall of 90.5mm in January this year, which was higher than average. Conventional paved surfaces are designed to shed water. Unfortunately, with the extreme rain we are faced with throughout the year, this can mean we see large volumes of water rapidly entering water courses and resulting in local flooding. 

Crucially, rainwater passes through the porous asphalt system and is treated at source to prevent solid particulates, heavy metals and organics from contaminating ground water supplies. By dealing with surface water run-off as close to its origins as possible, before it enters the water course, it significantly reduces the risk of localised flooding. 

Used as part of a wider SuDS system, the UltiPorous range can filter, clean and release rainwater slowly into the sub soil or alternatively collect it in a reservoir for harvesting as grey water – allowing water to be reused for things like flushing the toilet or washing the car. 

Cost effective, easy to install 

Compared to alternative surfacing systems, the UltiPorous range offers a cost effective and easy to install solution. It delivers benefits over the whole-life of its installation too and requires no maintenance of gulleys or drainage channels and, perhaps most importantly, is safer for pedestrians.  

With good slip-resistance combined with its monolithic surface, the UltiPorous range is much less likely to develop trip hazards than, for example, block paving. For local authorities and asset owners this can give peace of mind that car parks and driveways will be both safe for walking and secure from flooding.  

With new legislation coming into place next year, SuDS will become a necessary consideration for any developer not implementing them already. Drainage systems, such as UltiPorous, can contribute to a more sustainable built environment, as we deliver more resilient homes and public spaces.  

 As our climate and weather patterns are set to become more unpredictable, and the case for conserving water more pertinent, there’s no need to wait until 2024 to start laying the groundwork in preparation for a rainy day.  

Tarmac has been supplying porous pavements for 20 years for a range of applications from supermarket car parks, residential adoptable roads and parking areas.

For more information, visit: