The first 5mm: Designing for interception under the National SuDS Standards
📅 Tuesday 17 November 2026 | 12:30–13:15 GMT
Standard 2 of the National Standards for SuDS asks that the first 5 mm of rainfall from most events does not run off to surface water or piped drainage. Meeting this requirement means showing where that water goes, not just that a tank can hold it.
Join Dr. Netsanet Mebrate in this 45-minute session to learn what is considered interception, which SuDS features qualify, when you need to model, and how to test the requirement in Flow.
What we’ll cover
- Why interception is different from attenuation
- Which SuDS features count and the conditions that apply to each
- When you need hydraulic modelling, and when calculations are enough
- Flow’s First Flush approval test
- Starting Level drain-down check
- What to do when a design fails and what to submit
- Q&A
Host: Brent Olivier
Latest roadmap showcase
You’ll see how the latest roadmap direction supports:
-
Clearer water quality assessment using a CIRIA C753 Simple Index approach.
-
Faster storage sizing with improved storage auto-design.
-
Better evidence of infiltration performance.
-
Safer and faster design iteration with undo/redo history.
-
Stronger design control through link type slope constraints.
-
Closer SmartTools and Flow alignment, including enhanced CAD-based editing and output control.
Martin Young is a drainage design expert with over 40 years of experience helping engineers, consultants, and developers navigate complex drainage challenges and secure planning permission.
As Director of The Drainage Designers, Martin leads a specialist UK consultancy advising on SuDS compliance, surface water design, and planning submissions. With a career spanning major infrastructure projects and senior roles at leading consultancies, he has an exceptional breadth of experience across the full drainage design lifecycle.
Dr. Netsanet Mebrate brings over 21 years of both academic and commercial experience within drainage design software. Having completed a PhD in Scientific Computation, he is involved in Flow's strategic roadmap at Causeway, conducts both technical and market research, and builds the training and support capability.
Who should attend?
Drainage designers and engineers working on schemes in England.
