Technical Focus

SUDS: A NATURAL, BUT SCIENTIFIC, SOLUTION TO FLASH FLOODING

What can those in the built environment do to help mitigate the risks of flash flooding? Martin Lambley – Wavin Stormwater Management Product Manager, North West Europe, UK and Ireland – explains how having more sustainable drainage systems, or SuDS, can support the UK in building climate-resilient cities.

Ahead of COP26, the Environment Agency has reported that climate change is exacerbating the pressure on our water environment, with more flooding, more droughts and more extreme weather events. Emma Howard Boyd, the agency’s Chair, said we risk disastrous situations, such as the recent flooding in Germany, coming to the UK’s shores if the country does not quickly become more resilient.

With climate change making flood incidents more frequent and severe, our built environment needs to change the way it deals with stormwater and flooding. As the construction industry strives forward, aiming to bounce back from the pandemic, now is the time to start incorporating more innovative flood mitigation systems into both new projects and existing urban spaces. SuDS needs to be carefully considered in the planning phase of a development.

We need to start by looking at why climate change is causing more extreme weather events. Essentially, it’s because warmer atmospheres are able to hold on to moisture for longer, meaning when it does rain, we’re seeing more intense downpours over a shorter period. These can quickly overwhelm traditional urban drainage systems, often leading to disruption, damage and hazardous situations for the population.

The key issue with flash flooding is not being able to remove the high level of excess water away quickly enough. What’s needed here are solutions where excess water can be collected swiftly, but managed in the local environment in a controlled manner, and this is where SuDS (sustainable drainage systems) come in.

SuDS combine the natural filtration features found commonly in rural environments with mass-water storage systems to create a truly holistic and reliable solution. Rather than a pipe-based approach, SuDS recreate the natural process of surface water management.

There’s no question that SuDS will prove evermore valuable as we start to see more extreme weather events. Solely surface-based SuDS, which manage excess water while mimicking naturallyfound ponds and waterways, are effective but often require large amounts of space, which is not always available. This can be extremely difficult, or even sometimes impossible, to achieve in urban settings. With the pressure on converting as much space as possible to residential areas, the longterm viability of surface-based Finding opportunities for SuDS

Below-ground SuDS, such as Wavin’s Q-Bic Plus, which come in the form of geocellular attenuation tanks, can be used to enhance the resilience of urban areas. These solutions, along with elements such as permeable paving, can prove valuable when it comes to managing high volumes of surface water without taking up as much above-ground space.

These geocellular structures are particularly beneficial when compared to conventional tanks or large diameter pipes, thanks to their spatial versatility, ease of installation and maintenance, as well as the option for infiltration through a geotextile liner in suitable soils. They capture excess water quickly, but then slowly and gradually filter it back into the natural landscape, which ensures that the surrounding environment is not overwhelmed with water, either during, or after, the rainfall.

Incorporating both options into urban designs is a significant step forward in proactively addressing the impact of climate change, but also improving our overall drainage infrastructure on the huge scale that’s needed.

There is already a requirement that SuDS are considered as part of new developments under the National Planning Policy Framework, but making new builds more climate resilient won’t be enough on its own. Urban designers need to start looking at retrofitting SuDS into many existing areas. Below-ground SuDS are the ideal solution here, and offer fantastic opportunities for increasing the flood resilience of our cities, without having a major impact on design schemes.

Added value with sustainable drainage

As well as providing a sustainable management tool which deals with flood water, there are other benefits that come from incorporating SuDS into towns and cities.

For example, they’re proven to boost biodiversity levels in surrounding areas. A holistic approach to SuDS, including natural, surface-based elements, can support the creation of environments in which flora and fauna thrive. With the Government currently looking at plans to make biodiversity net gain a requirement for all new developments, using SuDS is a fantastic way to futureproof projects.

Another advantage of SuDS is their ability to improve water quality in the surrounding environment. Traditional drainage systems allow a multitude of contaminants, such as animal waste, litter and fertilisers, to be mixed in with surface water runoff. A comprehensive SuDS solution on the other hand, separates surface water runoff from sewage, thanks to its ability to lower the flow rate and increase natural filtration. This, in turn, lessens the burden on local authorities as water isn’t processed unnecessarily and prevents pollutants from flowing into natural water bodies.

When looking at the future of our built environment and its resilience against climate change, SuDS are a clear solution which need to be taken advantage of in new developments and retrofitted into existing ones. It’s sometimes seemingly small steps that make the biggest difference when it comes to climate action. By improving the capacity and water control capabilities of our drainage infrastructure, we can effectively mitigate the impact of climate change, protect the population and safeguard our towns and cities.  www.wavin.com