What is SuDS Drainage & Do I Need it?

SuDS, or Sustainable Drainage Systems, provide an efficient and natural approach to managing drainage around properties and developments. By reducing surface water runoff, temporarily storing water during storms and reducing peak flows, SuDs mimic the natural cycle of water management by retaining water where it lands.

SuDS drainage is often implemented in driveway construction, car parks, commercial developments, roads, industrial estates and urban areas. In some cases, SuDS isn’t required, especially when suitable permeable surface materials are used, but even then, it is often recommended that SuDS be considered. This is because it can provide faster and more efficient infiltration, suitable water treatment and enhanced flood risk management. In some cases, SuDS is required by law, regardless of the surface permeability, to help manage extreme rainfall, ensure long-term drainage resilience and protect downstream infrastructure.

The SuDs hierarchy

SuDS is placed into a hierarchical structure of three control categories. This is where SuDS is implemented on an increasing scale, depending on the scope of the area being managed.

Source control

Source control is fundamentally the best practice for SuDs. It is where water is managed in the area where it falls. This could be with permeable paving, infiltration trenches or green roofs.

Site control

Site control is the management of water runoff from a group of buildings or areas. This control method for SuDS is often incorporated through detention basins, swales or attenuation tanks.

Regional control

Regional control is where a SuDs drainage system is implemented as a large-scale feature to serve entire developments. In this instance, SuDS implementation comes from wetlands, retention ponds or balancing ponds.

SuDS drainage examples

SuDS can be implemented in many ways for small and large-scale developments. In some cases, it can be retrofitted to deliver further benefits to the local community and the environment. That being said, since 2015, ALL developments must incorporate SuDS unless it can be proven to be inappropriate. With the increased role of Lead Local Flood Authorities (LLFA), developers are advised to contact the relevant LLFA before submitting any planning applications to assess the most suitable SuDS drainage system for the land.

Suggestions could include:

Bioretention strips

Bioretention strips are vegetated areas with sand and gravel beneath them. They channel and filter water runoff vertically, allowing it to infiltrate the ground below or drain to a pipe that takes the water elsewhere. Flood risk is reduced due to the storage of the water runoff, and pollutants are removed as the strips filter the water as it passes through.

Detention basins

Detention basins are often used at the site level of SuDS, controlling the flow of water and attenuation of the runoff. As a result, they reduce flood risk by storing runoff and rainwater. Detention basins are often used in areas where treatment of runoff is required. Whilst useful as a SuDS, detention basins are also good for attracting wildlife, making the local area more attractive, educational and supportive of biodiversity.

Retention ponds

Retention ponds are commonly found at the regional level of the SuDS hierarchy. Beneficial when heavy rainfall occurs, they slowly release the water that’s been collected over time, allowing for controlled flow rates and a reduced chance of flooding. They should only be implemented in areas where there is sufficient land and require submerged aquatic vegetation for optimal results. Pollution is removed through sedimentation, and thanks to their size, retention ponds can withstand constant heavy rainfall, storing it and reducing flood risk.

Green roofs

Green roofs are a source control method and will often be found on both residential and commercial properties. In simple terms, green roofs have plants growing on them that soak up the rainfall by increasing infiltration and reducing runoff. They are easily retrofitted if the property structure can support it, so expert advice is advised if this is an avenue being considered.

Permeable paving

For most residential and commercial properties, a permeable surface for carparks, footpaths, driveway surfacing, and playgrounds is recommended. Water infiltrates it, reducing and delaying runoff and peak flow in watercourses.

Materials such as porous asphalt are advantageous. In many cases, they can drain as much as double their area. This allows more water to be stored and infiltrated than if it were to enter the watercourse directly. In many cases, with professional installation from a company like Tidey & Webb, a sub-base will deliver enhanced water treatment, removing any pollutants it may have picked up from the surface.

In most cases, such surfaces are easy to maintain, suitable for areas of high and low traffic and don’t require extra land space like some of the other SuDS methods developers consider.

Other SuDS methods

Other SuDS methods to be considered include:

• Swales – Shallow, broad vegetated channels that collect and move water to reduce peak flows in rivers.
• Wetlands – These shallow, marshy ponds treat surface water runoff through sedimentation and filtration, slowing the flow to allow for filtering.
• Rain gardens – Rain gardens are an infiltration method that increases the amount of water entering the soil, reducing runoff rates and surface water volume.

Do I need SuDS for my property or development?

Whether you need SuDS depends on a combination of site conditions, regulations and the type of development. Key considerations include:

Suds drainage regulations

Since 2015, most new developments in the UK must incorporate SuDS unless it can be demonstrated that they are inappropriate. The LLFA for the area can guide developers, with early consultation advised.

Surface permeability

Even if your residential or commercial property already has permeable surfaces in place, the addition of SuDS can be beneficial. With added flood resilience beyond what natural permeability achieves, improved water treatment and further levels of infiltration, retrofitted SuDS refine developments, making it more appealing to buyers and investors. However, effectiveness depends on site conditions, infiltration rates and soil type. Consulting a surfacing contractor for advice is advised before proceeding.

Site size and layout

Large sites such as roads, car parks, and high streets benefit from SuDS, even if permeable surface materials are installed. If impermeable surfaces, such as concrete or tarmac, are in use, retrofitting SuDS enhances the lifespan of the surface and can reduce continual expenditure. In commercial areas, such changes may also lead to an improvement in footfall as visitors won’t be perturbed by potentially flooded footpaths, roads or carparks.

Wider community, commercial and environmental benefits

With the implementation of SuDS, water quality can be improved, biodiversity supported, and more appealing recreational features created. Even if not required, such changes to the surface can help increase the long-term value and sustainability of a site.

Property developers and homeowners should consider SuDs if the site generates significant runoff, is deemed a high flood risk area or falls under planning requirements. Even for sites with permeable surfaces in place, SuDS provides additional benefits that could maintain or enhance property value. In commercial properties, SuDS may increase footfall and reduce the risk of accidents, injuries or reduced operating hours.

Tidey & Webb are the leading surfacing contractors for the South of England, expertly installing SuDs-compliant driveways, carparks, playgrounds and more. Contact our team today for a free quote or to discuss your surfacing requirements.