Hillingdon SuDS Design & Evaluation Guide

Detailed Design
Channels and rills
Sett Channels and rills keep rainwater at or
near the surface. This is important as it allows
water to flow directly into SuDS features
reducing cost, trip hazards and the
inconvenience of deep structures in the
landscape.
In some places a grated surface channel may
be more appropriate but the mesh size
should not be too small or the grating will be
prone to blockage.
A planted rill at Bewdley
School Science Block.
Collecting runoff from a road can be more
difficult where there is a path present and a
flush kerb inlet or chute gully may be needed.
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Use of pipes
Although SuDS are delivered without the
requirement for extensive piped networks,
short lengths of pipe can still be very useful
in providing connections under roads,
footpaths and other crossing points. Key
points to consider are as follows:
A granite sett channel collecting and conveying
runoff at Holland Park, London.
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Short lengths of pipework should allow
direct rodding from one end of the pipe
to the other without the need for internal
chambers.
Inlets and outlets should be designed so
that they are not prone to blockage.
An exceedance flow path should be
integrated into the development surface
above pipework to ensure that
unpredictable flows are directed SuDS
immediately after the crossing.
The depth of the downstream component
should not be artificially increased due to
a requirement for structural cover over
pipework. Different pipe materials or
Concrete pipe surround has been used here to
provide minimal cover for a driveway crossing at
Devonshire Hill, Haringey.
concrete surround can be considered to
minimise cover - as used for driveway
crossings at the Devonshire Hill project
above.
London Borough of Hillingdon SuDS D & E Guide
© 2018 McCloy Consulting & Robert Bray Associates