Are you an architect, property developer, builder, planner or landowner who needs to know exactly what a SuDS report is? Then this is the blog for you. Read on to learn what you need to know about SuDS design, SuDS strategy and the SuDS report itself.

What Are SuDS and Why Will I Need a SuDS Assessment?

Sustainable Drainage Systems (SuDS) are a way of designing surface water run-off at a development so that it promotes natural drainage. This reduces the risk of overflowing local drainage networks and watercourses — flash flooding, for example.

A SuDS report establishes:

• How much surface water run-off the proposed development will produce, and its peak flow rate, compared to the existing run-off rates where applicable
• Flow pathways and exceedance routes
• Infiltration potential — how likely the water is to soak into the ground and be treated at source
• An outline or detailed SuDS strategy, in line with local and national policy, that follows the SuDS management train
• The existing site’s greenfield run-off rate
• Soakaway sizes, where infiltration is feasible
• The required attenuation, where infiltration is not feasible
• An outline or detailed design of the SuDS systems and surface water network — the level of detail depends on the size of the project, whether it falls within a critical drainage area, and each local authority’s requirements

This information lets our Civil and Environmental Engineers work out how feasible SuDS is for your site. Importantly, a SuDS report sets out the measures you can take so your drainage meets the requirements of national and local planning policy.

This is crucial for achieving planning permission — especially if your development sits in an area at high risk of flooding (Flood Zone 2 or 3) or in a known critical drainage area.

Planning authorities want to avoid increasing flood risk on the site or elsewhere. A SuDS report shows how the development reduces the burden on existing pipe networks, which matters most where those networks are already close to or at capacity.

Find this out before you submit your planning application. Give us a call, or check the validation requirements for your application.

Why Are SuDS Better Than Traditional Drainage?

SuDS manage surface water run-off in a more sustainable and ecologically friendly way than traditional piped drainage.

Where possible, SuDS treat surface water run-off at source and slow its flow. This reduces the risk of overflowing piped networks and ditches, and ultimately reduces the risk of flooding.

SuDS also improve water quality by reducing pollution, and they protect natural waterways and local habitats by reducing water quantity. On top of this, they enhance urban spaces by encouraging vegetation and wildlife, which increases biodiversity and amenity value.

Will I Need Other Drainage Reports Too?

Depending on the size, location and type of development, you may need a second-stage report. Authorities sometimes request this once they have accepted or conditioned the SuDS strategy.

This is known as ‘Detailed SuDS and Surface Water Network Design’. It provides comprehensive layouts, long sections and construction details.

A detailed drainage design models the drainage network. Not all planning applications require one, though. Depending on the size and nature of the development, the authority may request it as a planning condition to discharge. We can produce this alongside design drawings for Building Regulations approval and for construction.

Key Recommendations for SuDS Assessments

Too often, a SuDS assessment becomes a last-minute consideration — which leads to costly outcomes for you or your client. You can avoid these costs by involving a SuDS report specialist from the outset.

We usually complete the SuDS assessment as a desktop study, so you won’t normally need a site visit. However, if you’d like one of our engineers to come out on site, we can arrange this. We can also arrange for an engineer to carry out a BRE365 percolation test if one is required.

With a SuDS assessment, you achieve a sustainable drainage strategy with the right level of detail to minimise surface water run-off from your development — helping you secure planning application approval.

Nimbus Engineering’s SuDS Assessments

If you need a SuDS report, don’t hesitate to contact Nimbus Engineering. Thanks to our close relationship with Lead Local Flood Authorities (LLFAs), you’ll get the right solution for your project, whatever its size or location.

As Civil Engineering and Environmental Consultants, we give you early-stage advice on sustainable drainage designs to integrate into your development. This lets you work around any constraints or risks in a natural, ecological way that is also cost-effective and feasible to construct.

Many of our competitors are environmental consultants only, so they lack the construction-stage design experience to take their SuDS proposals through to a stage the client can actually build from. We bridge that gap.