Civil Engineering: Drainage, SuDS and Flood Risk

Kelp Studio are civil and structural engineers working across London, Surrey, Sussex, Kent and Essex. Our civil engineering work covers everything below ground and around your building: drainage, sustainable drainage (SuDS), flood risk and the agreements you need with the water company and the council. Because we also design the structure, foundations, retaining walls and drainage are coordinated from the start.

Get a quote or call 020 3835 2633

Our civil engineering services

Drainage strategies and SuDS design
Surface water drainage strategies for planning, runoff and attenuation calculations, and SuDS such as soakaways, permeable paving, attenuation tanks and green roofs.

Flood risk assessments
Site-specific flood risk assessments for planning, prepared alongside the drainage strategy so both tell the same story.

Below-ground drainage design
Foul and surface water drainage layouts, levels and details for extensions, new homes and developments.

Percolation testing and soakaway design
Infiltration testing to BRE 365 and soakaways sized for your site and Building Control.

Water company agreements
Sewer connections (Section 106), sewer adoption (Section 104), sewer diversions (Section 185) and build-over agreements.

Utility searches
Locating existing sewers, water mains and services before design and construction starts.

Discharging planning conditions
Applications to discharge pre-commencement drainage and flood risk conditions, and responses to the council and Lead Local Flood Authority.

Who we work with
Developers, architects, planning consultants, builders, self-builders and homeowners, from single extensions to new housing developments.

Recent civil and structural work
• Meads Court, Bexhill-on-Sea: structural and below-ground drainage design to convert a disused commercial unit into shops and flats, with a new timber-frame storey on top.
• Downey Close, Hastings: a new townhouse development on a brownfield site in Hollington.
See more of our projects →

Flood Re: help with home flood insurance
Flood Re is a joint initiative between the Government and insurers that makes flood cover more affordable for homes at higher risk of flooding. It applies to most homes built before 2009. Its Build Back Better scheme can provide up to £10,000 towards flood resilience measures as part of an eligible insurance claim, and Flood Re is developing Flood Performance Certificates, planned to give lower premiums to homes with resilience measures in place.
We can assess your property’s flood risk and design the drainage and SuDS that help reduce it. Eligibility and cover are decided by Flood Re and your insurer. Visit Flood Re →

Common questions

What’s the difference between a civil and a structural engineer?
A structural engineer designs the parts of a building that carry load, such as beams, walls and foundations. A civil engineer deals with the infrastructure around it, such as drainage, flood risk and connections to sewers. We do both, so you have one point of contact.

When do I need a civil engineer?
Usually when your planning application needs a drainage strategy or flood risk assessment, when a drainage condition must be discharged before work starts, or when you need to connect to, divert or build over a public sewer.

Do you work on small projects?
Yes. Alongside developments, we regularly help homeowners with soakaways, drainage for extensions and build-over agreements. SuDS for homeowners →

12+ years’ experience · £1,000,000 PI insurance

Our structural design services →
Is my property at risk of flooding? →
SuDS explained: a plain-English glossary →