Page 40 - Bexley SuDS DESIGN & EVALUATION

Concept Design 7.4.6 Introducing sub-catchments When integrating SuDS into a development,

Many drainage designs adopt an approach
the site should be divided into sub-
where all flows are taken to the lowest point
catchments to maximise treatment and
of the site and attenuated in a single location,
storage capacity.
often referred to as a ‘pipe-to-pond’ or ‘pipe
to box’ approach.
The sub-catchment boundary is usually
defined as the surface area which drains to a
The ‘pipe to pond’ approach can result in
unsightly, polluted and sometimes hazardous
considered as a mini-watershed.
pond or basin features that offer little
amenity or wildlife benefit. The ‘pipe to box’ particular flow control, and can be
Flows are conveyed from one sub-catchment
approach results in below-ground structures to the next along one or more management
that provide no amenity or wildlife benefit at
trains, following the modified flow routes
all. All end of pipe solution may fill with silt determined early in the design process.
and generate management problems.
Each sub-catchment contributes flows to the
following sub-catchment or to an outfall.

35

Controlled flows are released from one sub-
catchment feature to the next, as here at Birchen
Coppice Primary School, Kidderminster.

London Borough of Bexley SuDS D & E Guide © 2018 McCloy Consulting & Robert Bray Associates