Cabinet Member Report
Date:
Subject:
16th March 2009
Strategic Flood Risk Assessment
Summary
1. 1 Planning Policy Statement 25; Development and Flood Risk (PPS 25)
December 2006 requires that Local Authorities carry out a Strategic Flood
Risk Assessment (SFRA) to assess all forms of flooding within their area.
Although the SFRA is not itself a policy document the information it contains
can be used as a source for policy making and for flood risk management.
1.2 It is part of the Council’s evidence base, used to inform planning polices for
flooding in the Core Strategy and the City Management Development Plan
Document (DPD), as part of the Local Development Framework. The Core
Strategy Publication Draft – February 2009 sets out the strategic policies for
flooding within Westminster. However, the more detailed policies will be
contained in the City Management Development Plan. Consultation for this
document will be way of briefing notes and a number of pubic workshops
scheduled to take place between April and June 2009.
1.3 Although the Environment Agency Flood Maps designate a large part of south
Westminster as being within Flood Zone 3 (1 in 100 or greater annual
probability of river flooding or a 1 in 200 or greater annual probability of
flooding from the sea), Westminster has very good flood defences (i.e the
Thames Barrier and Embankment Wall) which reduce this to a 1 in 1000
annual probability.
1.4 To help in the preparation of the SFRA, Halcrow were appointed as
consultants to refine the Environment Agency flood risk map and to carry out
an assessment of surface water flooding, which are considered to be the
most likely forms of flooding within Westminster. Halcrow’s report (June 2008)
comprises Appendix 1 of the SFRA.
1.5 Halcrow have advised that flooding from surface water is a more likely
occurrence in Westminster (1 in 100 annual probability) than flooding from the
Thames. Ways for managing surface water are still emerging. However, in
anticipation of clear national guidance the draft SFRA sets out information on
the areas within Westminster which are most likely to be affected by this type
of flooding.
Recommendation
1. That the Draft Strategic Flood Risk Assessment (Appendix 1 of this report) is
approved for public consultation purposes.
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Cabinet Member Report
City of Westminster
Cabinet Member:
Date:
Classification:
Title of Report:
Report of:
Wards involved:
Policy context:
Financial summary:
Cabinet Member for Built Environment
16th March 2009
For General Release
Strategic Flood Risk Assessment
Strategic Director Built Environment
All
Planning Policy Statement 25: Development and
Flood Risk
Planning Policy Statement 12: Local Development
Frameworks
Planning and Compulsory Purchase Act 2004
There are no financial implications arising from
this report
Report Author:
Sally Alderman
Contact details
Sally Alderman
Telephone 020 7641 6063
Fax 020 7641 3050
salderman@westminster.gov.uk
or Collette Willis
Telephone 020 7641 2387
Fax 020 7641 3050
cwillis@westminster.gov.uk
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1.
Background
1.1
Planning Policy Statement 25; Development and Flood Risk (PPS 25) represents a
move away from only building defences to stop river and tidal flooding to a more
holistic understanding of flooding. This factors in the impact of climate change,
requires an assessment of all potential sources of flooding and introduces a risk
based management approach, including the use of strategic planning, to avoid
inappropriate development in high risk flood areas.
1.2
As well as providing an evidence base for the emerging Local Development
Framework Documents – The Core Strategy and the City Management Plan. The
details on the sources of flood risk contained within the SFRA (in particular the
information produced by Halcrow) can be used to inform the Council's strategic
approach to flooding. For example, the maps provided by Halcrow are currently
being used as a base to assist in the preparation of the Council’s contingency plan
for flooding. They are also of benefit to the external stakeholders such as the
Police, Fire and Utilities and major landowners and developers.
1.3
The SFRA will be updated in light of emerging legislation and guidance and as new
or improved data becomes available, as such it is never formally adopted.
2.
Summary of key issues in the Draft Strategic Flood Risk
Assessment
Introduction – Local Context and Objectives
2.1
The Environment Agency has designated some 16% of Westminster as within
Flood Zone 3 and, therefore, at a high risk of flooding from the Thames (this is
shown on Map 1in the draft SFRA). This designation, however, assumes no
existing defences. Westminster however benefits from very good defences. Flood
Zone 3 is already highly developed with an existing population of 45,000 residents
and contains essential London infrastructure such as Victoria main line station and
a number of London Underground stations.
2.2
The main objective of the draft SFRA is to ensure that the main risks of flooding in
Westminster are set out. Using this information Sections 5 and 6 of the SFRA
contain details of the city council’s emerging policy approach for development in
areas that may be susceptible to tidal/ fluvial and surface water flooding. The
information contained within the draft SFRA has been used as evidence to help
inform the strategic policies for flooding within the Core Strategy Publication Draft
2009 and will also be used to inform discussion and seek views in preparation for
the more detailed spatial policies for flooding to be contained within the City
Management Plan. The Council has worked with the Environment Agency in the
preparation of the draft SFRA. The Environment Agency remain the main contact
for existing occupiers who require details on how to safeguard their homes from
flooding.
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The Sequential Test and Exceptions Test
2.3
The Sequential Test and Exceptions Test are contained within PPS 25 and are a
‘policy test’. The overall aim of the Sequential Test is to steer new development to
areas with a lower probability of flooding. PPS 25 advises that preference should
be given to locating new development in Flood Zone 1. Only if there are no
reasonably available sites in Zone 1, then the flood vulnerability of proposed
development can be taken into account, to first direct development to Flood Zone 2
and then Flood Zone 3.
2.4
If following the application of the Sequential Test it is not possible or consistent
with wider sustainability objectives for the development to be located in zones of
lower probability of flooding (i.e. Zones 1 and 2) , PPS 25 advises that the
Exceptions Test can be applied. The Exceptions Test provides a method for
managing flood risk while still allowing necessary development to occur in Flood
Zone 3
2.5
2.6
Sources of Flooding in Westminster
(a) Flooding from the Thames
In the unlikely event of a breach in the Embankment wall, Halcrow have identified
the ‘residual risk zone’, (this constitutes the most likely area to be flooded within
Flood Zone 3) and a rapid inundation zone (concentrated around four low lying
areas close to the Thames) which would rapidly inundate to significant depths.
This assessment has enabled a more refined policy approach to flooding within
Zone 3. This is shown in Map 7 in the draft SFRA.
(b) Surface Water Flooding
Much of the information and detailed advice in PPS 25 in terms of land use
planning concerns flood risk from rivers and the sea and there is currently limited
national guidance on surface water flooding. In anticipation of more detailed
government advice the Council requested that Halcrow provide detailed modelling
for surface water flooding. This type of flooding has been identified by Halcrow as
a more probable occurrence (a 1 in 100 annual probability) in Westminster than
flooding from the Thames and they have identified 19 ‘Critical Surface Water
Flood Locations within Westminster (which are shown on Map 9 in the draft
SFRA). Halcrow have set out a number of technical recommendations for further
discussion, which will be included in the briefing note for flooding as part of the
public workshops for the City Management Plan, scheduled to take place between
April and June 2009.
2.7
(c) Flooding from Sewers
Flooding from sewers is a London Wide problem. The Thames Tideway Tunnel
project plans to address combined sewerage discharge into the Thames and is
due to be completed by 2020 (subject to detailed planning and funding). The
Council is in ongoing discussions with Thames Water about the implications of
this project for Westminster.
2.8
(d) Flooding from Groundwater
The groundwater level in London is being addressed by the General Aquifer
Research Development Investigation Team (GARDIT) and through increased
abstraction of groundwater by Thames Water. Flooding from rising groundwater is
not considered to be a major problem in Westminster, however the current
situation will be kept under review.
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2.9
(e) Flooding from Canals, Water Features and Water Mains
There are a number of canals and water features in Westminster but these present
minimal flood risk as they have limited surface water inputs. Water mains run
below all parts of Westminster and, many of which date from Victorian times. Good
management of infrastructure is the key to minimising the threat of flooding from
these sources. Thames Water aim to replace over 2,500km of water mains in
London by 2015.
2.10
3.
Towards a Policy Approach for flooding
PPS 25 advises that policies for flooding need to be balanced with other policy
objectives and national guidance. The complexity of existing development,
insufficiency of land to meet housing targets and wider sustainability objectives
means that it is difficult to carry out the Sequential Test for residential use and
social and community uses in Westminster. This and other matters regarding the
sequential approach to development, the requirement for the Exceptions Test and
the requirements to ensure the safety of development from flooding and
appropriate mitigation measures are set out in detail in Sections 5, 6 and 7 of the
SFRA. The Core Strategy Publication Draft policy (CS42 Flood Risk) is as follows:

Highly Vulnerable Uses will not be allowed within Flood Zone 3

Proposals for More Vulnerable Uses within Flood Zone 3 will take the potential for
flooding into account, particularly those areas at risk of rapid inundation. Within the
Rapid Inundation Zone, new residential units at ground floor level and extensions
to residential at basement level will not be acceptable.

All development proposals should take flood risk into account and new
development should reduce the risk of flooding.
Financial Implications
3.1 There are no financial implications arising from this report. The cost of consultation
will be met from existing LDF budgets.
4.
Legal Implications
4.1 The SFRA forms part of the evidence base for the Core Strategy and City
Management Development Plan Documents. The SFRA will be included along with
other evidence when the Draft Core Strategy is submitted to the Secretary of State,
for Publication Examination in May 2009.
5.
Staffing Implications
5.1 There are no staffing implications as a result of the recommendations of this report.
6.
Business Plan Implications
6.1 The Core Strategy is the first key document to be prepared by the City Council as
part of its LDF and will be the ‘spatial expression’ of the Westminster City Plan.
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7.
Consultation
7.1 Views are sought from key partners and stakeholders directly involved in flooding,
environment and the provision of infrastructure and from the wider community in
Westminster, including Members, residents groups and major land
owners/developers.
8.
Crime and Disorder Act 1998
8.1
There are no direct crime and disorder issues identified from this report.
9.
Health and Safety Issues
9.1 The SFRA will have a positive impact on health and safety issues which may arrise
from flooding in Westminster.
10. Human Rights Act 1998
10.1 There are no Human Rights Act implications arising from this report.
11. Conclusions and Reasons for the Proposed Decision
11.1 PPS 25 requires all Local Authorities to carry out an assessment of flooding in their
area. The draft Strategic Flood Risk Assessment sets out this information for
Westminster. The report seeks approval for public consultation of the draft SFRA.
Background Papers
The documents used or referred to in compiling the report were: 1.
2.
3.
Draft Strategic Flood Risk Assessment – Consultation Version March 2009.
Draft Cabinet Member Report – LDF – Publication Draft Core Strategy – February
2009
PPS 25.
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For completion by the Cabinet Member for Built Environment
Declaration of Interest

I have no interest to declare in respect of this report
Signed ……………………………. Date………………………………
Councillor Robert Davis DL, Deputy Leader & Cabinet Member for the Built
Environment

I have to declare an interest
State nature of interest …………………………………………………
…………………………………………………………………………….
Signed ……………………………. Date………………………………
Councillor Robert Davis DL, Deputy Leader & Cabinet Member for the Built
Environment
(N.B: If you have an interest you should seek advice as to whether it is
appropriate to make a decision in relation to this matter.)
For the reasons set out above, I agree the recommendation(s) in the report entitled:
Draft Strategic Flood Risk Assessment
Signed ………………………………………………
Cabinet Member for the Built Environment
Date …………………………………………………
If you have any additional comment which you would want actioned in connection
with your decision you should discuss this with the report author and then set out your
comment below before the report and this pro-forma is returned to the Secretariat for
processing.
Additional comment: …………………………………………………………………
………………………………………………………………………………………….
………………………………………………………………………………………….
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NOTE: If you do not wish to approve the recommendations, or wish to make an
alternative decision, it is important that you consult the report author, the Head of
Legal and Services, the Director of Finance and Resources, if there are staffing
implications, the Head of Human Resources (or their representatives) so that (1) you
can be made aware of any further relevant considerations that you should take into
account before making the decision and (2) your reasons for the decision can be
properly identified and recorded, as required by law.
Note to Cabinet Member: The decision will now be published and copied to the
Members of the relevant Policy & Scrutiny Committee and may not be
implemented until five working days have elapsed from publication to allow the
Policy and Scrutiny Committee to decide whether it wishes to call it in.
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