Page 28 - Croydon

Drive in Couldson was severely affected and Local SuDS Specific Requirements
Local SuDS requirements
is a regular flooding hotspot.
The most recent significant groundwater
flooding event took place in 2013-2014 in
areas of Kenley and Purley, along the route of
Caterham Bourne, and around South
Coulsdon, along the route of Merstham
Bourne. Several groundwater observation
boreholes are located in and around the
Bourne catchment; in Woldingham and
Purley Bury. Instances of groundwater
flooding have been also reported in areas
around Upper Norwood; Thornton Heath and
Ashburton.
23
London Fire Brigade evacuations by boat in
Dale Road, February 2014 (Source: Croydon
Council - various officers)
New Addington, as well as the south of the
Borough, have been known to experience
foul sewer flooding during extreme rainfall
events caused by the foul sewer network
being inundated with surface water as a
result of legal and/or illegal connections to
the foul sewer network. Notable problem
areas include Caterham Drive, Marlpit Lane,
Chaldon Way and Coulsdon Road.
Croydon Council SuDS D & E Guide
possible, to accord with the London Plan
Drainage Strategies and Flood Risk
Assessments for all proposed major
developments within Croydon must comply
with the requirements of the London Plan,
National Planning Policy Framework (and
associated guidance) and the latest Croydon
Local Plan.
Local Plan Strategic Policy SP6.4 requires the
Council, as the Lead Local Flood Authority, to
work in partnership with the Environment
Agency, community groups, water and
highways infrastructure providers, developers
and other Lead Local Flood Authorities to
reduce flood risk, protect groundwater and
aquifers, and minimise the impact of all forms
of flooding in the borough. This will be
achieved by: a. Applying the Sequential Test
and Exception Test where required by Policy
DM25; b. Requiring major developments in
Flood Zone 1 and all new development within
Flood Zones 2 and 3 to provide site specific
Flood Risk Assessments proportionate with
the degree of flood risk posed to and by the
development, taking account of the advice
and recommendations within the Council’s
Strategic Flood Risk Assessment and Surface
Water Management Plan; c. Requiring all
development, including refurbishment and
conversions, to utilise sustainable drainage
systems (SuDs) to reduce surface water
run-off and provide water treatment on site;
and d. Requiring development proposals to
account for possible groundwater
contamination in Source Protection Zones 1
and 2.
Local Plan DM25.3 requires SuDS to be
included in all development to ensure runoff
is managed as close to the source as
© 2018 McCloy Consulting & Robert Bray Associates Croydon Council SuDS D & E Guide
managing flood risk in the Borough. The LPA
Sustainable Drainage Hierarchy; to achieve
better than greenfield runoff rates; to be
designed to be multifunctional and
incorporate sustainable drainage into
landscaping and public realm to provide
opportunities to improve amenity and
biodiversity; to achieve improvements in
water quality through a sustainable drainage
system management train; and to be
designed with consideration of future
maintenance.
London Borough of Croydon has suffered
significant surface water flooding due to
intense rainfall exceeding the capacity of the
existing drainage infrastructure; leading to
substantial overland flow and ponding of
surface water in low lying areas.
Ruskin Square, July 2017 (Source: © J & L
Gibbons / Sarah Blee)
Plans for regeneration, re-development and
densification within Croydon will present
further challenges to existing drainage
infrastructure. Re-development offers an
opportunity to reduce the volume of rate of
flow entering the sewer and will assist in
will seek to achieve less than Greenfield
Runoff rates from all re-development sites.
The southern part of the Borough, which is
widely underlain by Chalk, has potential for
infiltration discharge.
When a site is in Source Protection Zone 1
Local SuDS requirements
and 2, development proposals should
account demonstrate that the risk of
groundwater contamination has been
appropriately assessed and that the relevant
permissions have been sought from
Environment Agency
Local Planning Authority and
Stakeholder Engagement
All planning applicants are strongly advised
to seek pre-application advice from LPA prior
to development of scheme designs. The
’LLFA’s requirements for SuDS are illustrated
in Croydon Council’s website: https://www.
croydon.gov.uk/environment/flood-water/ 24
advice-to-planning-applicants.
Further information on SuDS can be found in
the same link.
Adoption and maintenance of SuDS
Croydon Council will consider adopting SuDS
features that are constructed in public spaces
if they provide benefits to Croydon residents.
© J & L Gibbons | Sarah Blee
Planning applicants are expected to submit a
site specific maintenance plan with all
drainage proposals, outlining the
management and maintenance of all surface
water drainage features over the
development’s lifetime, with confirmation of
how maintenance arrangements will be
funded.
© 2018 McCloy Consulting & Robert Bray Associates