strategic flood risk assessment supplement - Hambleton District ...

HAMBLETON DISTRICT COUNCIL
DESIGN AND MAINTENANCE - ENGINEERING
STRATEGIC FLOOD RISK
ASSESSMENT
SUPPLEMENT
JANUARY 2009

CONTENTS
INTRODUCTION Pages 3-4
DISCUSSION AND PLANS
STOKESLEY AREA
• Stokesley Pages 5-7
• Great Ayton Page 8
NORTHALLERTON AREA
• Northallerton Pages 9-11
• Brompton Page 12
THIRSK AREA
• Thirsk Pages 13-14
• Sowerby Page 15

INTRODUCTION
1.1 In January 2006 Hambleton District Council issued its’ Stage 1 Strategic Flood Risk Assessment
(SFRA) to support ‘Allocations’ in the Local Development Framework (LDF). The SFRA was
prepared under Planning Policy Guidance Note 25: Development and Flood Risk (published in
2001), this was replaced in December 2006 by Planning Policy Statement 25: Development and
Flood Risk.
1.2 The aim of PPS25 is to reinforce and strengthen planning policy in relation to flood risk and
development, introduce a more strategic approach and ensure a partnership approach to decision
making on planning applications and joined up thinking on flood risk management.
1.3 The aims of planning policy on development and flood risk are to ensure that flood risk is taken
into account at all stages in the planning process to avoid inappropriate development in areas at
risk of flooding, and to direct development away from areas at highest risk. Where new
development is, exceptionally, necessary in such areas, policy aims to make it safe without
increasing flood risk elsewhere and where possible, reducing flood risk overall.
1.4 The PPS25 introduces the flood risk approach of; appraise, manage and reduce. The production
of the SFRA supports appraising risk, by identifying land at risk and the degree of risk of flooding
from river, sea and other sources in our area.
1.5 A PPS25 Development and Flood Risk practice guide was published in June 2008 to offer
guidance on the implementation of PPS25.
1.6 This addendum SFRA document has been produced to supplement the January 2006 SFRA and
should be read in conjunction with the January 2006 document. Its purpose is to provide new
flood maps and update information where there have been changes since January 2006. The
addendum document follows the same format of the 2006 SFRA.
1.7 The new information provided in the document includes:
• Additional Flood Map
o Sowerby
• Revised Flood maps
o Brompton
o Great Ayton
o Northallerton
o Stokesley
o Thirsk
• Updated information
o Brompton, Northallerton and Romanby Flood Alleviation Scheme
o Thirsk Flood Alleviation Scheme
o Use of flood maps
1.8 Use of flood Maps
The flood map information is indicative rather than specific and users will have to consult with the
Environment Agency if further information is required where appropriate. The flood map
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information in the SFRA addendum is that issued in January 2009. The Environment Agency will
update the data as better information becomes available e.g. changes in hydrological river
response, observations following flood events or improved modelling techniques. Locations may
also be at risk from other sources of flooding that have not been surveyed here, such as high
ground water levels, overland run off from heavy rain, or failure of infrastructure such as sewers or
storm drains.
The SFRA January 2006 does identify areas at flood risk from other sources; these have been
identified through a process of consultation, though there may be flood risks from other sources
that are not identified in the SFRA.
When in doubt the Environment Agency should be consulted. The limits of the Flood Zones 2 and
3 are indicative of the area which could be affected by flood events and is largely based on
modelled data.
Where appropriate the flood maps show flood defences and for major defences the areas of
benefit from them. Where present, flood defences do not remove the chance of flooding and can
be over topped or fail in extreme weather conditions or where the flood event exceeds the design
standard of the defence. It does not show the effects of climate change.
1.8 Key to Plans
HDC requested sandbags
Oct 2000 to 2006
E.A. Flood Zone 2
0.1% annual flooding
probability
Main River
E.A. Flood Zone 3
1% annual flooding
probability
4

DISCUSSION AND PLANS
STOKESLEY AREA
• Stokesley
Flooding
The flood map for the Stokesley area has been subject to significant revision in comparison to the
flood maps included in the January 2006 SFRA. The revised flood maps follow a review by the
Environment Agency of their entire flood modelling data for the Stokesley area.
The new flood maps show increases in the flood zone 2 and 3 extents to the North and North West
of the town and removes or reduces the flood zone 1 islands in and around the southern residential
areas.
The increased flood zone 2 and 3 extents have reduced the flood zone 1 areas, the land
sequentially preferred for development, though there still remain significant areas of flood zone 1 to
the western side of the existing residential area. It is intended that these areas will be the focus for
new development.
The three flood map extracts show the Town, a more detailed extract of the flood zone 1 areas on
the western edge of the existing residential area and the Industrial Park area located to the south of
the town.
5

• Great Ayton
Flooding
The review of the Stokesley flood modelling data included the Great Ayton settlement as the village
formed part of the Environment Agency commissioned Upper Leven Flood Risk Management
Strategy study.
The review has changed the flood zone 2 and 3 extents on the land in the vicinity of Cleveland
Lodge, with the flood zones now aligned with the minor watercourse. The allocation for proposed
development at Cleveland Lodge is now all located in flood zone 1.
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NORTHALLERTON AREA
• Northallerton
Flooding
The proposed Brompton, Northallerton and Romanby Flood Alleviation Scheme planned to
commence in spring 2006 was not constructed. Tenders submitted for the scheme exceeded the
pre-tender cost estimates and it was not possible to increase the DEFRA grant aid to meet the new
anticipated scheme costs.
Stage one works, which were small scale relatively low cost measures which could be carried out in
a short time frame to provide an immediate reduction in flood risk were completed. These measures
included:
• Reconstruction of wooden hill bridge in Romanby, this reduced the restriction caused by the
bridge;
• Meanders on Willow Beck were straightened in the vicinity of Chantry Road, Romanby to
improve flows in the watercourse;
• Boundary treatments to properties on Chantry Road properties that back onto the Willow Beck
were reconstructed to introduce flood defence characteristics;
• Flood defences were constructed around Brompton School;
• The public highway and public open space areas on the southern end of Water End, Brompton
were lowered to create an overflow to improve watercourse flows in flood conditions.
The enmainment of ordinary watercourses associated with the proposed Flood Alleviation scheme
was enacted. This process confers main river status on critical ordinary watercourses (those
ordinary watercourses associated with flood risk affecting properties). The enmainment was
originally planned to be enacted on scheme completion, this was to allow the Environment Agency
to take over the maintenance of the Flood Alleviation scheme following its completion. The
Environment Agency can only carry out works on a main river, the enmainment of the watercourses
means that now only the Environment Agency under their permissive powers are able to progress a
Flood Alleviation Scheme for Brompton, Northallerton and Romanby.
The present position of the scheme is that the 2006 scheme is to be reviewed by the Environment
Agency in light of a new system, ‘outcome measures’ for prioritising funding of flood risk
management schemes. The scheme review is due to start in April 2009 and should take 12 months
to complete. The review is also intended to confirm the robustness of the proposed scheme and
help determine the scheme priority within the National programme of flood risk management
spending.
The 2 flood map extracts show Northallerton and Northallerton North. There are a number of small
amendments to the High Street area; these are shown for information but do not affect the
allocations. The more detailed Northallerton North plan has been included to show the flood risk in
the vicinity of the significant allocations proposed in this area.
9

• Brompton
Flooding
The revised flood map is included for information; there are some amendments in the centre of the
village to the flood zone 2 and 3 extents. The amendments do not affect the allocation site directly
though are adjacent to the allocation site.
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THIRSK AREA
• Thirsk
Flooding
Following the flooding that affected Thirsk and other areas in November 2000, Hambleton District
Council set up a Flood Forum to bring Agencies together to consider solutions for significant areas
at risk from flooding. The Forum looked to identify the lead agency to address problems at each
identified location. A number of options were considered for the flooding in the centre of Thirsk after
which the District Council commissioned Consultants JBA in 2004 to investigate the feasibility of
providing a Flood Alleviation Scheme for Thirsk. The Hambleton work indicated that there was
potential for an economically viable Flood Alleviation Scheme for Thirsk at that time, though further
work was required.
In April 2006 the responsibility for Cod Beck watercourse was transferred to the Environment
Agency (EA) as part of a national programme to rationalise powers for watercourses which posed
significant risk for property flooding. This process changed the watercourses’ status from ordinary
watercourse to that of having main river status. The main river status means that the EA have
permissive powers to carry out works on the watercourse including Flood Alleviation works. This in
effect made the EA the lead agency for flood alleviation in Thirsk.
EA work on developing a scheme for Thirsk was suspended later in 2006 following cuts in the
Agency’s budgets.
The present position on the scheme is that the EA has gained funding to recommence work on the
Thirsk investigation works in 2008. Consultants – Royal Haskoning were appointed to develop a
Project Appraisal Report (PAR) and commenced work in summer 2008. A PAR is a detailed study
of an area/community affected by flooding and is used by the EA to inform the prioritisation of
funding for Flood Risk Management Schemes. It is anticipated that the Thirsk PAR will be
completed in October 2009.
The flood map for Thirsk town has been included for information purposes and confirms changes
made to the flood zone 2 and 3 extents to the north eastern area of Thirsk in the vicinity of
Whitelass Beck.
13

• Sowerby
Flooding
The flood map has been included to show the flood zones and their relationship to the allocation
proposed for South West Sowerby. The existing flood zones do not extend to this allocation.
Detailed development specific Flood Risk Assessment will be required demonstrate that the
development can be developed safely without flood risk to the development itself or creating flood
risk elsewhere.
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Hambleton District Council
Civic Centre, Stone Cross, Northallerton, North Yorkshire DL6 2UU
Tel: 0845 1211 555 Fax: 01609 767248 Email: planning.policy@hambleton.gov.uk
www.hambleton.gov.uk
© HDC 2009