Understanding Sustainable Drainage Systems (SuDS)

Sustainable urban drainage systems – also known as SuDS – have revolutionised traditional draining methods to reduce flooding and enhance water quality. But how?

This blog will help you understand sustainable urban drainage system design, including what SuDS are, how they work, and why they’re important.

What are SuDS?

Sustainable Drainage Systems (SuDS) are drainage solutions that provide alternatives to the direct channelling of surface water through networks of pipes and sewers to nearby watercourses (i.e rivers, streams, brooks, becks, culverts).

In natural environments, rainwater falls onto permeable surfaces and soaks into the ground – a process called infiltration.

sustainable drainage strategy

In urban areas, many surfaces are sealed by paving and buildings which means that natural infiltration becomes limited. Instead, to avoid flooding, drainage networks consisting of pipes and culverts divert surface water to local watercourses. In some cases, this has led to downstream flooding and the deterioration of river water quality. This is due to the overwhelming of foul sewers by surface water, resulting in a release of dirty water into rivers.

By mimicking natural drainage regimes, a sustainable drainage strategy works to reduce surface water flooding, improve water quality and enhance the amenity and biodiversity value of the environment by:

  • Storing or recycling surface water at source 
  • Lowering water flow rates to watercourses 
  • Increasing water storage capacity  
  • Reducing the transport of pollution to the water environment  

How do SuDS work? 

SuDS consists of a series of techniques that work together to form a management train.  As surface water flows through the system, flow rate is controlled and pollutants are removed.  The management train may include these stages: 

  • Source control methods to decrease the volume of water entering the drainage/river network by intercepting run-off water on roofs for subsequent re-use (e.g. for irrigation) or for storage and subsequent evapotranspiration (e.g. green roofs). 
  • Pre-treatment steps such as filter trenches or swales that remove pollutants from surface water prior to discharge to watercourses or aquifers. 
  • Retention systems which delay the discharge of surface water to watercourses by providing storage within ponds, retention basins or wetlands. 
  • Infiltration systems, such as soakaway designs and infiltration trenches that work by mimicking natural recharge and allowing water to soak into the ground.  

sustainable urban drainage system design

Why are SuDS important? 

When a natural environment is developed, an important part of the surface becomes impervious, i.e roads, buildings, car-parks etc. The aim of SuDS developed by expert drainage design consultants like ours here at Onn Point, is to reduce surface water flooding, improve water quality and improve the environment’s amenity biodiversity. 

Existing urban drainage systems unable to cope with excessive amounts of water cannot be overstated because without green infrastructure, the damage caused by flooding will only increase. 

A recent Climate Change Committee report has warned that almost 200,000 properties in England might have to be abandoned by 2050 because of sea levels rising1, and the Energy and Climate Intelligence Unit has predicted roughly 35,000 hectares of horticultural and arable land are at risk of flooding every three years2.  This means that by the 2080s, the risk of flooding could reach 130,000 hectares of high-quality land. 

So, to help reduce this risk, it is vital that solutions are put in place, and SuDS are a natural and highly effective solution.  

In Summary 

Representing a shift to more sustainable practices, the importance of SuDS cannot be overstated. By emulating natural processes and reducing the impact of urban development on watercourses, sustainable urban drainage system designs are creating healthier environments for both people and wildlife.   

They offer a holistic approach to managing water that fosters harmony between our infrastructure and the natural world, making our cities safe and livable for generations to come. The challenges of climate change and urbanisation must be addressed – and SuDS are a key way to do it.  

At Onn Point, our drainage design specialist team is committed to crafting professional sustainable urban drainage designs that seamlessly harmonise with the environment. Our expert SuDs reports can also help you understand exactly what is needed from your sustainable drainage design to meet the demands of your project.  

Get in touch with our team today and let us guide you towards a greener, more sustainable future.