Nations globally are grappling with the effects of climate change. In recent years, instances of extreme flooding and severe droughts have brought cities to a standstill and caused significant danger to life. Although a nation known for its rainfall, Ireland is facing similar challenges - something the 2008 floods highlighted. With a projected national rainfall increase of 20% over autumn and winter by 2050, alongside an up-to-40% increase in dry periods over summer, the reality of rolling droughts and floods is frighteningly close to home.
This backdrop of climate change, combined with urbanisation, is creating the perfect storm. Urban centres and parched greenfield sites simply can’t absorb the extreme rainfall events that are beginning to characterise winter months. Because water can’t soak directly into the soil, surface water run-off is increasing – overwhelming drainage networks and causing water bodies like rivers and lakes to overflow, resulting in flooding. But there are ways the Irish construction industry can work proactively to mitigate the effects of extreme rainfall and protect homes, businesses and people from flooding. One of the key ways to achieve this is through a commitment to sustainable drainage systems (SuDS).
How are SuDS different to traditional drainage systems?
SuDS help a developed site to manage rainfall and surface water as well as – and potentially better than – it would have done as a greenfield site. By managing surface water runoff as close to the source and surface as possible, SuDS mimic natural drainage and help water to naturally soak into the ground, evaporate from surface water and provide transpiration from vegetation. Mitigating flooding, reducing pollution, providing green spaces and creating amenities for the community, What makes an outstanding SuDS solution?
Successful SuDS schemes typically prioritise early stakeholder engagement and careful planning in order to create effective and cost-efficient solutions. There are a wide range of SuDS components available; including green roofs, rain gardens, tree pits, permeable paving, swales, perforated pipes, rainwater harvesting, soakaways and various types of underground attenuation and storage tanks.
Engineers, landscape architects, urban designers, local authorities, water companies and developers all have a role to play in developing SuDS schemes, with the best designs incorporating the four pillars of SuDS:
1. Managing water quantity
This pillar focuses on managing the volumes and flow rates of surface water runoff. By reducing the rate of rainfall runoff to the greenfield equivalent, this pillar uses a number of tools to attenuate the surface water to tackle the impact of everyday rainfall and high-intensity storms.
2. Managing water quality
The more development in an area, the greater the variety and volume of pollutants, particularly from transport. In managing water quality, SuDS works to remove pollution from the water and therefore prevent it from entering the natural environment –
3. Creating amenities
This refers to the place-making element of a great SuDS scheme, and an effective SuDS project should improve the quality, character or overall enjoyment of an area. With green spaces alone proven to have a positive impact on people’s mental health, SuDS can also provide spaces like playgrounds as well as beautify streetscapes and improve air quality.
4. Creating a habitat for biodiversity
The fourth pillar of SuDS seeks to mitigate some of the disruption that development and urbanisation cause for wildlife habitats and ecosystems. With good design, SuDS can provide shelter, food, foraging and breeding opportunities for a variety of wildlife species including plants, amphibians, invertebrates, birds, bats and other mammals.
Is a government mandate the most effective way to ensure SuDS?
With their strong contribution to place-making in urban areas, and ability to mitigate increasing flood risk, SuDS are seemingly an obvious choice for developers. However, although SuDS technology has been available for decades, it’s yet to become ubiquitous in new developments in Ireland. It would be easy to assume these superior systems are cost-prohibitive, but SuDS schemes have been proven to be no more expensive than traditional surface water management schemes and there’s also evidence that developers who incorporate SuDS can charge a price premium for their housing stock. With so much to gain, why is SuDS uptake not more prominent in Ireland? The experience of our UK neighbours might shed some light.
In recent years, Wales, Scotland, and Northern Ireland have raced ahead of England in providing a clear mandate on integrating SuDS and providing a pathway for adoption, which for a long-time was a barrier to wider SuDS implementation. Comparing the devolved nations, it’s increasingly clear that, without a government mandate, developers won’t take the initiative to upskill and move the market towards widespread SuDS installation. Lord Krebs’ summarised the situation, when he argued: “As long as developers have the automatic right to connect to existing drainage there is no incentive or need to implement sustainable drainage systems. England is lagging behind the devolved administrations – Northern Ireland has ended the automatic right to connect, in Scotland SuDS is a general requirement, and Wales has much more extensive standards through the implementation of Schedule 3 of the Flood and Water Management Act of 2010. Now is the time for the Government to respond to this amendment by saying yes, we agree this is a simple and straightforward way to ensure all the new homes to be built will be protected from flooding”. Responding to this stalemate, the UK.
How is SuDS uptake progressing in Ireland?
Irish legislation isn’t as stringent as some of the UK’s devolved nations, and SuDS is required on new developments except where the developer can demonstrate that its inclusion is impractical due to site circumstances. Despite this, SuDS are increasingly required by local authorities across new developments, re-development and retrofit projects. Dún Laoghaire Rathdown County Council, for example, is actively recommending the implementation of SuDS as part of new developments and re-developments; while the Dublin City Council Development Plan (2022-2028) has identified SuDS as preferred, firming up the city’s 2005 commitment to mandatory SuDS on new developments in the Greater Dublin Strategic Drainage Study. Dublin has also published clear SuDS requirements in its Dublin City Council Sustainable Drainage Design and Evaluation Guide. Around the country, councils like Wicklow County Council are following suit, and have made a firm commitment to SuDS. In its latest development plan, the council stated that it “requires all new development to adopt the SuDS approach”. But while there’s clear progress in some regions, others, like Cork, continue to exercise less stringent requirements for city development plans. Instead, Cork commits “where appropriate and possible…to encourage the use of SUDs”.
Moving SuDS forwards
Despite the differences in local planning policy, they outline national best practice for SuDS delivery. These standards mean that, where SuDS are built in Ireland, they should be installed to the highest standard, and their success will hopefully encourage developers to prioritise SuDS in future. While SuDS have achieved significant uptake in parts of Ireland, it’s vital the construction industry engages with other stakeholders to keep this momentum.
Ideally, all water management stakeholders will come together to strengthen regulations and deliver a coordinated, effective strategy for surface water. SuDS need to become a mainstream part of surface water management – a compulsory stage in developments and a key consideration in schemes to regenerate or improve existing urban environments. To find out more about the technology Wavin offers to help support your next SuDS scheme, take a look at our website.
