Recently at this year’s New Civil Engineer Flood Resilience Conference in the UK, Martin Lambley, senior product manager, climate resilience, at Wavin, delivered a clear and urgent message addressing one of the most pressing infrastructure challenges of our time: how we manage surface water in a changing climate.

Embracing a hybrid, integrated approach

Lambley’s core point was straightforward: the future of urban resilience lies not in choosing between grey or green infrastructure, but in embracing a hybrid, integrated approach that maximises the strengths of both.

©Meristem Design_ Royal Dock Rain Gardens.

©Meristem Design_Forest Road Rain Gardens SuDS.

He outlined the growing severity of the issue. Urbanisation is accelerating, with more than four billion people now living in cities. As impermeable surfaces replace natural land, the ability of cities to absorb and manage rainfall is shrinking. When combined with increasingly intense and frequent weather events caused by climate change, this creates a dangerous scenario – one where flash flooding can and does occur in areas historically unaffected.

Much of the infrastructure in place today simply wasn’t built to handle this level of demand. In regions like Dublin and many other cities, networks originally designed in the Victorian era are now operating under extreme stress.

Even modern stormwater systems – often designed for one-in-100-year events with a 40% climate change allowance – are being overwhelmed. Lambley highlighted the coastal city of Valencia, which in October 2024 experienced a year’s worth of rain in just eight hours.

Martin Lambley, senior product manager – climate resilience at Wavin.

“No one is designing for that,” he said.

So what’s the solution?

Grey infrastructure – pipes, tanks, channels - continues to play a critical role. It is engineered for reliability and performs well in high-flow scenarios. But it is expensive, difficult to adapt, and doesn’t offer the wider environmental benefits cities now need.

Green infrastructure - such as rain gardens, green roofs, and wetlands - offers significant advantages. It helps manage run-off, supports biodiversity, enhances water quality, and can cool urban areas. It improves both functionality and liveability. However, it often can’t function alone, especially under extreme weather stress. It requires space, time, and integration.

This is why Lambley promotes a “grey enabling green” philosophy - where smart, engineered systems support and optimise nature-based solutions.

He pointed to several successful real-world applications of this approach:

In Copenhagen, the response to repeated cloudbursts has become an international model. The city has implemented expanded sewer capacity and stormwater boulevards (grey), in tandem with green roofs, permeable pavements, and pocket parks (green), all integrated into a citywide strategy that prioritises both resilience and quality of life.

In Amsterdam, Wavin supported a smart water management project spanning 21 buildings. These 'blue-green roofs' temporarily store rainwater and release it slowly via evapotranspiration.

Equipped with smart soil moisture sensors, the system ensures irrigation happens only when needed, using captured rainwater. The result is a self-sustaining, climate-responsive system that both prevents flooding and generates high-resolution data to guide future planning.

Elsewhere, in the UK Wavin has supported urban regeneration projects that replace underused space with green infrastructure. In one initiative, more than 380 metres of rain gardens were installed, complemented by a below-ground attenuation system to handle extreme rainfall. A smart pump recirculates stored rainwater to irrigate the landscape – an example of grey infrastructure enabling green performance.

These case studies prove that we don’t need to choose between infrastructure types. When grey and green are combined, cities become more flood-resilient, more sustainable, and better prepared for climate-driven challenges.

But progress requires more than just good technology. As Lambley emphasised, designing smarter, greener cities demands collaboration – among engineers, planners, developers, local authorities, and communities. It also needs policy support, long-term funding, and public education. The framing must shift from 'grey or green' to 'smart and hybrid' – because the climate emergency isn’t waiting.

Lambley concluded with optimism: "We've moved beyond old debates that pitted hard infrastructure against soft. The real breakthroughs are now happening in the spaces where engineering meets ecology, where decisions are driven by data, and where infrastructure exists to support not just logistics – but life."

To discuss your project requirements, please contact projects.ie@wavin.com