ENVIRONMENT
Goodman International Ltd.
Phase 2, Unit 2
Centrum West
Burton-upon-Trent
FLOOD RISK ASSESSMENT
www.bwbconsulting.com
P/2016/01529Received 21/10/2016
B W B C o n s u l t i n g L t d : R e g i s t e r e d i n E n g l a n d 5 2 6 5 8 6 3
ENVIRONMENT
Goodman International Ltd.
Phase 2, Unit 2
Centrum West
Burton-upon-Trent
FLOOD RISK ASSESSMENT
Birmingham
Livery Place, 35 Livery Street, Colmore Business
District, Birmingham, B3 2PB
T: 0121 233 3322
Leeds
Whitehall Waterfront, 2 Riverside Way, Leeds LS1
4EH
T: 0113 233 8000
London
11 Borough High Street
London
SE1 9SE
T: 020 74073879
Manchester
4th Floor Carvers Warehouse, 77 Dale Street
Manchester, M1 2HG
T: 0161 233 4260
Nottingham
Waterfront House, Station Street, Nottingham
NG2 3DQ
T: 0115 924 1100
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Limitations
All comments and proposals contained in this report, including any conclusions, are based on information available
to BWB Consulting during investigations. The conclusions drawn by BWB Consulting could therefore differ if the
information is found to be inaccurate or misleading. BWB Consulting accepts no liability should this be the case, nor
if additional information exists or becomes available with respect to this scheme.
Except as otherwise requested by the client, BWB Consulting is not obliged to and disclaims any obligation to update
the report for events taking place after:-
(i) The date on which this assessment was undertaken, and
(ii) The date on which the final report is delivered
BWB Consulting makes no representation whatsoever concerning the legal significance of its findings or the legal
matters referred to in the following report.
All Environment Agency mapping data used under special license. Data is current as of August 2016 and is subject
to change.
The information presented and conclusions drawn are based on statistical data and are for guidance purposes only.
The study provides no guarantee against flooding of the study site or elsewhere, nor of the absolute accuracy of water
levels, flow rates and associated probabilities.
This report has been prepared for the sole use of Goodman International Ltd. No other third parties may rely upon or
reproduce the contents of this report without the written permission of BWB. If any unauthorised third party comes into
possession of this report they rely on it at their own risk and the authors do not owe them any Duty of Care or Skill
i
DOCUMENT ISSUE RECORD
Document Number CWS-BWB-EWE-XX-RP-EN-0001-FRA
BWB Reference BMW-2575-FRA
Status Revision Date of Issue Author Checked Approved
S2 P1 02/08/16
Julian O’Neill
BSc. MSc.
Keith Alger
BSc (Hons) MSc
Chris Dodd
BEng (Hons) IEng
MICE
S2 P2 09/08/16
Julian O’Neill
BSc. MSc.
Keith Alger
BSc (Hons) MSc
Chris Dodd
BEng (Hons) IEng
MICE
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EXECUTIVE SUMMARY
This Flood Risk Assessment (FRA) is compliant with the requirements set out in the National
Planning Policy Framework (NPPF) and the associated Planning Practice Guidance. It has
been produced on behalf of Goodman International Ltd. in respect of a planning application
for a warehouse development within Phase 2, Centrum West, Burton-upon-Trent (approximate
grid reference: 422460, 322670)
This report demonstrates that the proposed development is not at significant flood risk, subject
to the recommended flood mitigation strategies being implemented.
The site lies within close proximity to three Environment Agency Main Rivers. Correspondence
with the EA has confirmed that the site falls outside of the 1 in 1000 year Shobnall Brook
floodplain. The site is located within Flood Zone 2 of the River Trent (2.4km to the south).
Modelled flood depths are shown to be 0.44m across the formation plateau in the 1 in 1000
year flood event. The Tatenhill Brook, which is 2.1km to the west of the site, is shown to
contribute flood water during high flow events to an Unnamed Ordinary Watercourse (UOW)
which runs through the southern boundary of the site. It was therefore necessary to undertake
a hydraulic flood modelling exercise to understand the risk to the site from these two
watercourses. Results of the modelling show that due to recent realignment works undertaken
within the wider ownership, flood water will not spill onto the site in any event up to and
including the 1 in 1000 year.
Groundwater, canal overtopping, and surface water flooding are shown to pose a medium
risk to the development.
In order to mitigate risk of inundation from any of the sources of flooding the finished floor levels
of the development have been set at 47.30m AOD. This gives 1.3m of freeboard above the 1
in 1000-year event on the UOW, and 10mm of freeboard above the 1 in 1000 year event on
the Trent.
Based upon a drainage strategy undertaken by a 3rd party it is intended that surface water be
attenuated to 17l/s, a prorated rate using previously consented rate for the wider site. The
existing pond to the south west of the development will be used to attenuate surface water in
all events up to an including the 1 in 100 year + 30% allowance for climate change storm.
In compliance with the requirements of National Planning Policy Framework, and subject to
the mitigation measures proposed, the development could proceed without being subject to
significant flood risk. Moreover, the development will not increase flood risk to the wider
catchment area as a result of suitable management of surface water runoff discharging from
the site.
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CONTENTS PAGE
DOCUMENT ISSUE RECORD i
EXECUTIVE SUMMARY ii
CONTENTS PAGE iii
INTRODUCTION 1 Sources of Data 1 Existing Site 1 Proposed Development 3 Flood Risk Planning Policy 3 Other Relevant Policy and Guidance 4
POTENTIAL SOURCES OF FLOOD RISK 6 Fluvial Flood Risk 6 Flood Risk from Canals 9 Groundwater Flood Risk 10 Flood Risk from Reservoirs & Large Waterbodies 10 Flood Risk from Sewers 11 Pluvial Flood Risk 12 Effect of Development on Wider Catchment 13
FLOOD RISK MITIGATION 14 General Mitigation 14 Finished Levels 14 Safe Access 14 Surface Water Drainage 15
OUTLINE DRAINAGE ASSESSMENT 16 Outline Surface Water Assessment 16
CONCLUSIONS AND RECOMMENDATIONS 17
TABLES
Table 1.1 - Site Summary Table 2.1 - Pre-Mitigation Sources of Flood Risk Table 2.2 – UOW Modelled Flood Levels Table 5.1 - Summary of Flood Risk Assessment
FIGURES
Figure 1.1 - Site Location Figure 1.2 - Environment Agency Flood Map for Planning (Rivers and Sea) Figure 2.1 – 1 in 100 year + 20% modelled Flood Depths (UOW) Figure 2.2 - Environment Agency Reservoir Failure Flood Risk Map Figure 2.3 - Risk of Flooding from Surface Water Mapping
APPENDICES
Appendix 1 - Topographical Survey, Enabling Earthworks/ Diverted Watercourse Drawings
Appendix 2 - Development Proposals and Proposed Level Drawings
Appendix 3 - Environment Agency Correspondence
Appendix 4 - Canal and River Trust Correspondence
Appendix 5 - Drainage Layout (ref: 03-0059-101) and MicroDrainage calculation sheets
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INTRODUCTION
This Flood Risk Assessment (FRA) is compliant with the requirements set out in the
National Planning Policy Framework (NPPF) and the associated Planning Practice
Guidance. The FRA has been produced on behalf of Goodman International Ltd. in
respect of a planning application for the “Phase 2, Centrum West” warehouse
development in Burton-upon-Trent.
Table 1.1 - Site Summary
Site Name Phase 2, Centrum West
Location Burton-upon-Trent
NGR (approx.) 422460, 322670
Application Site Area (ha) 1.9 (Approximately)
Development Type Warehouse / Logistics
NPPF Vulnerability Less Vulnerable
EA Flood Zone Flood Zone 2
EA Office Sentinel House, Staffordshire
Local Planning Authority East Staffordshire Borough Council
Sources of Data
The report is based on the following information:
(i) Site Layout Plan by pHp Architects ref: 3747-3-101
(ii) Topographical Survey by BWB Consulting, ref: BMW/2155/SVY/001
(iii) Enabling earthworks drawings by Hydrock, ref: C14309-208
(iv) Watercourse diversion drawings by BWB, ref: BMW-2155-W100, W101, W102,
W103, W104
(v) Ordnance Survey 1:10000 scale mapping
(vi) Environment Agency consultation and model information
(vii) East Staffordshire Strategic Flood Risk Assessment
(viii) Hydraulic modelling of the Unnamed Ordinary Watercourse undertaken by
BWB Consulting
(ix) Surface Water Drainage Design by THDA ref: 03-0059-102-A
(x) British Geological Survey Drift & Geology Maps
Existing Site
The site is situated off Callister Way within Burton-upon-Trent, East Staffordshire. It is
bound by the A38 to the west, the Trent and Mersey Canal to the south east and a
proposed warehouse building to the north east (known as Centrum West, Phase 2). A
site location plan is included as Figure 1.1, which also includes key water features in
proximity to the site. Topographically the site is flat, as it has been prepared for the
proposed development. These enabling works were conducted after planning consent
was granted by East Staffordshire District Council, ref: P/2015/00891, and included the
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diversion and partial culverting of the Unnamed Ordinary Watercourse (UOW) which
flows on the southern boundary of the site.
Figure 1.1 - Site Location
Appendix 1 includes approved drawings showing the finished levels of the enabling
earthworks and details of the diverted watercourse, including general arrangement
and typical sections. The original topographical survey is also included for reference.
The remainder of this report assumes that the existing conditions on the site are those
which were consented under that enabling works application.
The site is situated upon bedrock geology including the Bromsgrove Sandstone
Formation which is overlain with the Mercia Mudstone Group. There are superficial
deposits recorded which include the Holme Pierrepont Sands and Gravels. The site is
also within an area designated by the Environment Agency as a Groundwater Source
Protection Zone; it is within an Inner zone (Zone 1), Outer zone (Zone 2) and Total
catchment (Zone 3). This designation is likely to be in relation to a groundwater
abstraction just south of the site.
Shobnall Brook
River Trent
Unnamed
Ordinary
Watercourse
Tattenhill Brook Estimated
location.
Eventually
outfalls to Trent
Trent and
Mersey Canal
Approximate Site
Location
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Proposed Development
The proposed development is for a distribution warehouse, with associated
infrastructure; including car parking spaces, and access to the link road which is to be
constructed as part of the ‘Phase 2’ development. A copy of the development layout
is available in Appendix 2.
Flood Risk Planning Policy
National Planning Policy Framework
The NPPF1 sets out the Government’s national policies on different aspects of land use
planning in England in relation to flood risk. Planning Practice Guidance is also
available online2.
The Planning Practice Guidance sets out the vulnerability to flooding of different land
uses. It encourages development to be located in areas of lower flood risk where
possible, and stresses the importance of preventing increases in flood risk off site to the
wider catchment area.
The Planning Practice Guidance also states that alternative sources of flooding, other
than fluvial (river flooding), should also be considered when preparing a Flood Risk
Assessment.
This Flood Risk Assessment is written in accordance with the NPPF and the Planning
Practice Guidance.
Flood Zones
The Flood Map for Planning has been prepared by the Environment Agency. This
identifies areas potentially at risk of flooding from fluvial or tidal sources. An extract from
the mapping is included as Figure 1.2.
The Environment Agency mapping shows the site to be located entirely within Flood
Zone 2 (Medium Probability) of the River Trent. This Flood Zone is defined in the NPPF as
land assessed as having between a 1 in 100-year and a 1 in 1000-year annual
probability of river flooding.
Environment Agency correspondence and model information confirm that the site is
outside of the 1 in 1000-year floodplain of the Shobnall Brook, which is discussed further
in Section 2.
A hydraulic modelling exercise to understand the risk to the site from the Unnamed
Ordinary Watercourse and catchment transfer flows from the Tatenhill Brook is
discussed in Section 2.
Table 2 of the Planning Practice Guidance classifies land use. Under these
classifications the proposed development use; storage and distribution and associated
infrastructure is considered to be ‘Less Vulnerable’.
1 National Planning Policy Framework, CLG, March 2012
2 Planning Practice Guidance. http://planningguidance.planningportal.gov.uk/.
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Table 3 of the Planning Practice Guidance identifies that a ‘Less Vulnerable’
development within Flood Zone 2 is considered to be ‘appropriate’.
Figure 1.2 - Environment Agency Flood Map for Planning (Rivers and Sea)
Other Relevant Policy and Guidance
Strategic Flood Risk Assessment
East Staffordshire Borough Council commissioned the production of two strategic flood
risk assessments for the borough in 2008, both of which contain information relevant to
the site location.
The Level 1 SFRA3 states that severe flooding along the entire length of the Shobnall
Brook occurred in July 1999. It indicates that much of the flooding in recent years in the
area has been attributable to blocking of grills/culverts. Extreme events in 1999/2000
caused overtopping of non-main rivers within the suburbs, mostly through the
3 East Staffordshire Borough Council Level 1 Strategic Flood Risk Assessment February 2008
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surcharging of culvert entrances. It does not however relate this information directly to
the site in question.
It also states that no problems have been observed on the Trent and Mersey Canal
and that locks regulate water level through the use of both fixed and manually
operated sluices and weirs. This maintains a freeboard of 300mm between normal
water level and top of bank. The SFRA does identify that although no problems have
been observed, any interaction with the Trent could increase flood risk from this source.
Flood mapping of the Shobnall Brook included as part of the SFRA is believed to have
been superseded by more recent Environment Agency hydraulic modelling –
discussed in Section 2.0.
Sequential Testing
The site is shown to lie within Flood Zone 2, so under the National Planning Practice
Guidance it is required to undergo a Sequential Test.
A Sequential Test was undertaken for a previously consented planning application for
a similar warehouse unit on the site (ref: PA/25617/023/JPM/PO), demonstrating the
development was suitable and as such passed the Sequential Test as part of the
permission which was granted.
Furthermore, the August 2008 East Staffordshire Borough Council SFRA identifies the site
as being suitable for employment purposes under reference ‘E26’.
Therefore, based on the history and precedent of previous applications on the site and
supporting detail from the SFRA it is not necessary to undertake the process again for
this application.
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POTENTIAL SOURCES OF FLOOD RISK
The table below identifies the potential sources of flood risk to the site, and the impacts
which the development could have in the wider catchment prior to mitigation. These
are discussed in greater detail in the forthcoming section. The mitigation measures
proposed to address flood risk issues and ensure the development is appropriate for its
location are discussed within Section 3.0.
Table 2.1 - Pre-Mitigation Sources of Flood Risk
Flood Source Potential Risk
Description High Medium Low None
Fluvial
X The site is located in Flood Zone 2 of
the River Trent.
X
The site is located outside of the
Shobnall Brook 1 in 1000-year
floodplain.
X
The Tatenahll Brook and the
Unnamed Ordinary Watercourse on
the site is shown to pose a low risk to
the site.
Canals X
The Trent and Mersey Canal
maintains a freeboard of 300mm
between the normal water level
and top of bank. There have been
no records of overtopping on this
section.
Groundwater X
Groundwater emergence from
bedrock is unlikely however there is
a risk that perched water may
bepresent within superficial
deposits.
Reservoirs and
waterbodies X
The site is shown to fall inside of the
area at risk of reservoir failure;
though the probability of this
occurring is very low.
Sewers X No sewers present within the site.
Pluvial runoff X Surface water flow routes are
present within the site.
Effect of
Development
on Wider
Catchment
X
The development will increase the
area of impermeable surfaces
leading to a potential increase in
runoff
Fluvial Flood Risk
There are three main rivers which are in proximity to the development site. The flood risk
from each of these has been confirmed through correspondence with the Environment
Agency. The Burton Tributaries flood modelling exercise was published in 2014; both the
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Shobnall and Tatenhill Brooks were part of that study. Correspondence from the
Environment Agency confirming flood levels is available in Appendix 3.
River Trent
The site lies in Flood Zone 2 (extreme flood extent) of The River Trent which is
approximately 2.4km south east of the site. Product 4 information from the Environment
Agency shows that the 1 in 1000-year flood level on the site is 47.29m AOD. The plateau
created by the above mention previous consented planning application (ref.
P/2015/00891) is identified to be at 46.85m AOD. Flood depths during that event would
therefore be approximately 0.44m in the external areas of the site.
Burton-upon-Trent is afforded protection from River Trent flooding due to the
Environment Agency maintained flood defences present (details in Appendix 3).
Breach analysis of the defences has been undertaken by the EA at several locations
for the 1 in 100-year event to identify the residual risk of flooding in such an eventuality.
Extents are shown not to reach the site, and therefore this risk pathway can be
excluded.
On the above basis the site is only considered to be at medium risk of flooding, from
extreme river flood events.
Shobnall Brook
The Shobnall Brook is the closest Environment Agency main river to the site, located
approximately 500m to the north. It flows in a south easterly direction before entering
culvert and being diverted along the canal in a north eastern direction away from the
site. Figure 1.1 shows its location.
As noted above, the EA have recently completed detailed modelling of the Shobnall
Brook which shows that the site is outside of the 1 in 1000-year floodplain.
Tatenhill Brook & Unnamed Ordinary Watercourse
The Tatenhill Brook is 2.5km to the south west of the site, and is shown by the Burton
Tributaries Study to have an extensive floodplain – associated with it being tide locked
by water levels on the Trent during high flow events. Mapping shows this floodplain to
potentially interact with that of the UOW. The UOW flows along the southern boundary
of the site and enters a culvert beneath the Trent and Mersey Canal at the north
eastern corner of the site, immediately south of the existing attenuation feature.
In order to determine the flood risk to the development from the UOW and Tatenhill
Brook, a 1 Dimensional – 2 Dimensional (1D-2D) hydraulic flood model was created. This
was undertaken using the Flood Modeller Pro, ESTRY and TUFLOW software packages.
The model links the existing Environment Agency ESTRY-TUFLOW representation of the
Tatenhill Brook produced as part of the Burton Tributaries Study (2014) with a Flood
Modeller Pro – TUFLOW model of the UOW created by BWB (2015/16). This connection
was created using the TUFLOW multi-domain link.
The “Adapting to Climate Change: Guidance for Risk Management Authorities4”
document has been used to ascertain the potential impact of climate change on the
proposed development. The site is within the Humber river basin district and is a ‘less
4 Adapting to Climate Change: Advice for Flood and Coastal Erosion Risk Management Authorities (2016), Environment Agency.
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vulnerable’ development in Flood Zone 2. It is therefore required for river flows to use
the ‘central allowance’ for climate change. Given the expected lifespan of the
development is in excess of 50 years; a 20% uplift on the 1 in 100 year flows should be
used as the design standard scenario.
Results of subsequent modelling show that while the floodplain from the Tatenhill Brook
spills into the upstream catchment of the UOW, peak flows are not significantly
impacted, but the hydrograph is extended. Flood levels from key events are available
in Table 2.1, interrogation locations are illustrated within Figure 2.1.
Given that the formation plateau level is 46.85m AOD, and the 1 in 1000 flood level at
the upstream node is 46.02m AOD, there is 0.83m of freeboard to the ground level of
the site even in the most extreme event. A sensitivity scenario also undertaken where
the UOW culvert beneath the Trent & Mersey Canal was blocked by 50% shows that
flood flows remain in bank, and levels are 20mm higher than the 1 in 1000-year event.
Figure 2.1 – 1 in 100 year + 20% modelled Flood Depths (UOW)
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Table 2.2 – UOW Modelled Flood Levels
FMP Model
Node
Return Period (years)
20 100 100+20%
100
(50% Blockage of
D/S Culvert)
1000
ConsWC_9 46.24 46.36 46.43 46.39 46.60
ConsWC_8 46.24 46.36 46.43 46.39 46.61
ConsWC_7 46.23 46.36 46.43 46.39 46.61
ConsWC_6 45.92 45.96 45.99 46.07 46.05
ConsWC_5 45.90 45.94 45.97 46.07 46.02
ConsWC_4 45.88 45.92 45.95 46.06 46.01
ConsWC_3 45.86 45.90 45.94 46.05 46.00
ConsWC_2 45.83 45.89 45.92 46.05 45.98
Flood risk from the UOW and Tatenhill Brook is therefore thought to pose a low risk to
the site.
Flood Risk from Canals
The Trent and Mersey Canal runs directly adjacent to the south eastern boundary of
the site. The SFRA states that no problems have been observed on the Trent and Mersey
Canal and that locks regulate the water level through both fixed and manually
operated sluices and weirs. This maintains a freeboard of 300mm between normal
water level and top of bank.
The Canal and Rivers Trust were previously contacted in relation to the full planning
application for the site to provide any relevant information on the relevant section of
the Mersey and Trent Canal (see Appendix 4).
The Canal and Rivers Trust confirmed that:
(i) All water for this navigation is passed down through the locks from the River
Trent at Wychnor, Alrewas, located approximately 9km south of the site
location.
(ii) There are no feeders or uncontrolled discharges into this section of the
navigation.
(iii) They are not aware of any records of overtopping from this section of the
waterway. Generally this section of the canal is protected by a 300mm
freeboard.
With the provision of 300mm of freeboard, the risk from the canal to the development
is considered low.
There is a residual risk that the canal could spill into the site, where upon flood water
would be intercepted by the unnamed ordinary watercourse. This residual risk should
be considered within the developments mitigation strategy.
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Groundwater Flood Risk
The site is situated upon bedrock geology including the Bromsgrove Sandstone
Formation which is in turn overlain with the Mercia Mudstone Group. There are
superficial deposits recorded which include the Holme Pierrepont Sands and Gravels.
The Mercia Mudstone Group is classified by the Environment Agency as a Secondary B
aquifer. Secondary B aquifers are considered to be predominantly lower permeability
layers which may store and yield limited amounts of groundwater due to localised
features such as fissures, thin permeable horizons and weathering.
The sands and gravels overlaying the Mudstone are classified as a Secondary A aquifer
and are considered to be permeable layers capable of supporting water supplies at a
local rather than strategic scale, and in some cases forming an important source of
base flow to rivers.
There is a borehole log available via the BGS GeoIndex web app within proximity to
the site. The borehole log describes the geology to include; 15m of Sands and Gravel,
183m of Mercia Mudstone Group and 132m of the Bromsgrove Sandstone Formation
(base not proven). There is the potential for perched water to be present within the
sands and gravels which are likely to be in continuity with the watercourses. During
periods of high flows and intense rainfall water levels within the sands and gravels may
rise to pose a risk to underground structures or construction methods.
The risk from this source is considered to be medium and further mitigation measures
for the proposed development are outlined within Section 3.0.
Flood Risk from Reservoirs & Large Waterbodies
Reservoir failure flood risk mapping has been prepared by the Environment Agency,
this shows the largest area that might be flooded if a reservoir were to fail and release
the water it holds. The map displays a worst case scenario and is only intended as a
guide. An extract from the mapping is included as Figure 2.2.
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Figure 2.2 - Environment Agency Reservoir Failure Flood Risk Map
This data indicates that the site is located within the reservoir failure floodplain (as
indicated within Figure 2.2). The modelled flood extent relates to Blithfield reservoir
which is operated by South Staffordshire Water Plc.
Given the stringent controls and legislation on reservoirs the Environment Agency have
stated a flood to the extent shown is extremely unlikely. Reservoirs are also inspected
regularly insuring safety works are carried out. As such it is considered that the site is not
at significant flood risk from this source in spite of the mapping, especially considering
the ‘Less Vulnerable’ status of the proposed development.
The overall risk posed by the source is considered to be low.
Flood Risk from Sewers
There are no sewers within the site, however, the topographical survey (Appendix 2)
shows that there is a surface water sewer network within Callister Way which was
provided with the infrastructure to serve the wider site.
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It is understood that the sewers that have been provided in the wider infrastructure
have been sized appropriately and the residual risk of sewer flooding would therefore
be the result of an extreme rainfall event or blocked gullies. In this event flood flows
would be in a south easterly direction following the topography of the site. The diverted
watercourse would intercept these flows and therefore minimise disruption to users or
areas outside the site.
The overall risk posed from the sewer source is considered to be low.
Pluvial Flood Risk
Risk of flooding from surface water mapping has been prepared by the Environment
Agency, this shows the potential flooding which could occur when rainwater does not
drain away through the normal drainage systems or soak into the ground, but lies on or
flows over the ground instead. An extract from the mapping is included as Figure 2.3.
Figure 2.3 - Risk of Flooding from Surface Water Mapping
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The Environment Agency Surface Water flood maps show there to be a ‘low risk’
surface water flood route which runs through the site, as shown in Figure 2.3. There is
also an area of ‘medium risk’, where surface water may pond within the site. Though it
should be noted that this mapping exercise was undertaken prior to the enabling
earthworks. There is therefore unlikely to be any significant ponding on site, as it has
been flattened in preparation for the proposed development.
Hazard mapping of this low probability event shows that the majority of the surface
water flooding shown is low in nature, and could be managed using suitable mitigation
measures during construction of the development. Further mitigation measures are
recommended in Section 3.0.
Effect of Development on Wider Catchment
Displacement of Floodplain
There is no displacement of high risk fluvial floodplain. As the site lies within Flood Zone
2, there is a residual risk that there will be displacement of flood water in high
magnitude events. Under current NPPF guidelines there is no requirement to
compensate for that lost volume.
Development Drainage
The proposed development will have a modern standard of surface water drainage
which will ensure that no additional flow will be passed on to others within the
catchment.
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FLOOD RISK MITIGATION
Section 2.0 has identified the sources of flooding which could potentially pose a risk to
the site and the proposed development. This section of the FRA sets out the mitigation
measures which are to be incorporated within the proposed development to address
and reduce the risk of flooding to within acceptable levels.
General Mitigation
Temporary outfalls into the rivers during the construction phase will require discharge
consents from the LLFA. The discharge location points, the date when the discharge
will start, the duration of the discharge and the method of their installation will need to
be submitted. The flows from these outfalls would also need to be agreed.
Due to the location of the site within a Groundwater Source Protection Zone it will be
necessary during the construction for onsite refuelling facilities to take place in a
bunded area over an impermeable surface to prevent runoff and infiltration. Refuelling
activities should comply with the Environment Agency’s Pollution Prevention Guidance
by regular testing of the storage tanks and pipes. Any surface water runoff from these
areas will need to be routed through an oil separator before disposal.
There is the potential for groundwater to be encountered during construction. Where
significant groundwater is encountered within excavations alternative dewatering
system will need to be employed. The advice of a suitably experienced contractor
should be sought to determine the most viable option.
Finished Levels
Finished floor levels of the proposed warehouse are shown as 47.30m AOD. This provides
1.3m of freeboard above the UOW 1 in 1000-year flood level. This is also sufficient to
raise it nominally above 1 in 1000-year River Trent flood level. Drawings showing the
proposed development levels are available in Appendix 2.
The 47.3mAOD floor level is approximately 300mm above the downstream canal tow
path level. Therefore, should the canal spill into the site, it would overflow into the
downstream floodplain before it exceeded the floor levels.
The proposed finished level is 0.45m above the development plateau which will help
to mitigate and residual risk of ingress via pluvial runoff or groundwater. It is also
recommended to profile exterior ground levels away from the development towards
the closest drainage point.
Safe Access
Safe, dry pedestrian access to and from the proposed development can be provided
via the proposed access onto Callister Way on land outside the high risk floodplain of
watercourses in proximity to the site.
PHASE 2, SPECULATIVE UNIT, CENTRUM WEST, BURTON-UPON-TRENT
AUGUST 2016
CWS-BWB-EWE-XX-RP-EN-0001-FRA
15
Surface Water Drainage
To mitigate the development’s impact on the current runoff regime it is proposed to
incorporate surface water attenuation and storage as part of the development
proposals, discussed in detail within Section 4.0
PHASE 2, SPECULATIVE UNIT, CENTRUM WEST, BURTON-UPON-TRENT
AUGUST 2016
CWS-BWB-EWE-XX-RP-EN-0001-FRA
16
OUTLINE DRAINAGE ASSESSMENT
Outline Surface Water Assessment
This section of the report has been prepared in conjunction with THDA Consulting
Engineers, who have provided the strategy, including calculations and drawings, which
are available in Appendix 5.
Existing Site Runoff
Previously the wider site (including this application area) gained consent to discharge
at a rate of 86.8l/s that was based upon a site area of 9.93ha. This application concerns
a smaller portion of that wider site (1.9ha) therefore, the consented discharge rate for
this plot is worked out as 17l/s. (MicroDrainage calculation available within Appendix
5).
Drainage Hierarchy
Although infiltration testing has not been undertaken it is not thought soakaways are
viable due to ground water levels on the site.
Proposed Site Runoff
It is intended that the site runoff is limited to discharge at 17l/s in all events up to and
including the 1 in 100 + 30% allowance for climate change.
The vast majority of surface water will be routed through the existing pond to the south
west of the site, which was constructed for this purpose under a previous application.
It is proposed discharge will be limited using an orifice control.
The site has been split into several drainage catchments, with the parking area to the
north draining to one discharge point in the attenuation pond with an appropriately
sized oil separator. The HGV parking loading area and siphonic drainage system from
the warehouse roof drain to an alternative piped connection to the attenuation basin.
Again, an appropriately sized oil separator will be used to prevent pollution entering
the basin from the yard.
The proposed access road has been identified as a separate catchment, which
discharges via a drainage ditch towards the UOW, details of which can be seen in the
strategy drawing.
Detailed MicroDrainage simulations have been carried out and are available in
Appendix 5.
Exceedance Events
Exceedance events should be designed to route towards the attenuation basin or
UOW.
PHASE 2, SPECULATIVE UNIT, CENTRUM WEST, BURTON-UPON-TRENT
AUGUST 2016
CWS-BWB-EWE-XX-RP-EN-0001-FRA
17
CONCLUSIONS AND RECOMMENDATIONS
This Flood Risk Assessment (FRA) is compliant with the requirements set out in the
National Planning Policy Framework (NPPF) and the associated Planning Practice
Guidance. The FRA has been produced on behalf of Goodman International Ltd. in
respect of a planning application for the Phase 2, Centrum West, Burton-upon-Trent.
This report demonstrates that the proposed development is at an acceptable level of
flood risk, subject to the recommended flood mitigation strategies being implemented.
The identified risks and mitigation measures are summarised within Table 5.1:
Table 5.1 - Summary of Flood Risk Assessment
Flood Source Proposed Mitigation Measures
Fluvial
Development finished floor levels and thresholds are set above the 1 in 1000
year flood level for all watercourses that are shown to have a potential
impact on the site.
Groundwater Any residual flood risk from groundwater sources will be mitigated by raising
the development above surrounding ground levels. Detailed mitigation
maybe required during construction, as outlined in Section 3.0 of this report. Canals
Sewers The risk of the external sewer capacity being exceeded and any residual risk
of pluvial runoff affecting the site will be mitigated through creation of a flow
route through the site into the attenuation pond and positively drained areas Pluvial runoff
Impact of the
Development
The proposed drainage network on the site will not increase surface water
discharge from the site.
This summary should be read in conjunction with BWB’s full report. It reflects an assessment of
the Site based on information received by BWB at the time of production.
In compliance with the requirements of National Planning Policy Framework, and
subject to the mitigation measures proposed, the development could proceed without
being subject to significant flood risk. Moreover, the development will not increase
flood risk to the wider catchment area as a result of suitable management of surface
water runoff discharging from the site.
APPENDIX 1
Topographical Survey
Enabling Earthworks Drawings &
Diverted Watercourse Alignments
P/2015/00891Received 16/06/2015
47.1
0
46.2
7
So
46.66
46.65
46.03
47.11
47.20
45.95
45.9
8 46.8
446
.87
46.1
2
46.1
8
46.8
646
.80
45.9
1
47.00
47.02
46.8
847
.05
45.3
345
.37
45.23 45.3
5
45.80 45
.91
45.77
45.89
45.99
45.97
46.00
46.63
46.0
045
.86
Head
wall
Grass
Post and rai
l fence h
t 1.2m
LOW FLOW/ BASE
FLOW CHANNEL
0.3m DEEP
PROPOSED BACKWATER
0.5m DEEP
ROCK ARMOR
EROSION
PROTECTION
B
B
Trent and Mersey Canal
46.18
46.80
45.9146.01
46.9646.93
46.11 45.90
46.83
46.81
46.22 46.75
47.0546.91
46.1146.38
46.8047.26
46.99 47.15
47.7446.93
46.6946.75
47.67
47.68
46.97 47.12
47.79
47.64
46.73
45.9945.94
46.00 45.97
46.50 46.94 47.12 47.00
46.93
46.81
46.64
Pillar
Raised pipe
PROPOSED
RIFFLE
PROPOSED
ONLINE POOL
0.8m DEEP
2.5m WIDE
FLOOD FLOW
BED
A
A
C
C
I
I
I
I
50.00m
47.12
47.79
47.64
46.73 46.34
47.39
47.62
47.0947.00
47.36
47.05
46.4646.37
47.29
47.44
46.9946.98
47.38
47.11
46.40
46.9347.07
46.47 47.03
46.95
46.7846.80
46.85
46.6246.81
46.64Grass
1:3 EMBANKMENTS
1:3 EMBANKMENTS
4
5
.
2
9
3
D
D
O
rd
in
a
ry
B
ro
o
k
WL
46.9146.26
46.88
So
47.22
47.34
46.77
46.83
47.35
47.57
46.40
46.39
46.79
46.71
46.9146.96
46.36
46.31
46.93
47.1047.06
46.29
45.79
46.49
46.77
46.51
46.56
46.6446.74 46.88
45.37
46.73
46.38
46.5346.55 46.71
47.10
46.75
46.79
46.91
46.9045.34
45.11
45.3645.17 44.95
46.58
Headwall
Grass
Grass
BWB846.905
BWB946.750
EXISTING BED TO
BE DE-SILTED
REDUNDANT WATER COURSE
CHANNEL TO BE BACKFILL
AFTER DIVERSION IS
COMPLETE
NOTES
1. DO NOT SCALE THIS DRAWING. ALL DIMENSIONS MUST BE
CHECKED/ VERIFIED ON SITE. IF IN DOUBT ASK.
2. THIS DRAWING IS TO BE READ IN CONJUNCTION WITH ALL
RELEVANT ARCHITECTS, ENGINEERS AND SPECIALISTS
DRAWINGS AND SPECIFICATIONS.
3. ALL DIMENSIONS IN MILLIMETRES UNLESS NOTED
OTHERWISE. ALL LEVELS IN METRES UNLESS NOTED
OTHERWISE.
4. ANY DISCREPANCIES NOTED ON SITE ARE TO BE REPORTED
TO THE ENGINEER IMMEDIATELY.
5. EXCAVATED MATERIAL TO BACKFILL EXISTING CHANNEL
AFTER THE WATER VOLE HABITAT TO WHERE THE NEW
CHANNEL DISCHARGES.
KEY
c Copyright BWB Consulting Ltd
Drawing No. Revision
Drawing Status
Size
Drawing Title
Project Title
Scale
Reviewed
Drawn
A1
ISSUES & REVISIONS
Rev Date Details of issue / revision RevDrw
Client
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
P4BMW/2155/W100
PRELIMINARY
G. Littlewood
R. Green
1:200
WATERCOURSE
DIVERSION GENERAL
ARRANGEMENT
CENTRUM WEST
ENABLING WORKS
50m LONG CULVERT 750mm Ø
ALTHON H10_C_A HEADWALL WITH TRASH
SCREENS OR APPROVED EQUIVALENT
PIPE CONNECTI0N 450mm Ø CAPPED (PROPOSED OUTFALL FROM DEVELOPMENT
ALTHON H6C A HEADWALL WITH ALTHON HDPE 500mm
FLAP VALVE (580 X 610mm) OR APPROVED EQUIVALENT
TYPICAL CROSS SECTION WITH LOW FLOW
CHANNEL AND "BACK WATER"
100 YEAR PLUS CLIMATE
CHANGE FLOOD LEVEL.
NORMAL WATER LEVEL
(BASE FLOW)
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
0.40
0.3
TYPICAL CROSS SECTION WITH LOW FLOW
CHANNEL
NORMAL WATER LEVEL
(BASE FLOW)
100 YEAR PLUS CLIMATE
CHANGE FLOOD LEVEL.
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
EXISTING
BOUNDARY
FENCE LINE
0.3
100 YEAR PLUS CLIMATE
CHANGE FLOOD LEVEL.
NORMAL WATER LEVEL
(BASE FLOW)
TYPICAL CROSS SECTION OF RIFFLE
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
EXISTING
BOUNDARY
FENCE LINE
100 YEAR PLUS CLIMATE
CHANGE FLOOD LEVEL.
NORMAL WATER LEVEL
(BASE FLOW)
TYPICAL CROSS SECTION OF ON-LINE
POOL
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
PROPOSED GROUND PROFILE
NOT STEEPER THAN 1 IN 3
EXISTING
BOUNDARY
FENCE LINE
0.8
1.3
2.2
2.0
0.75
0.6
1.5
PIPE 750mm ø
PRECAST HEADWALL WITH
TRASHCREEN (ALTHON H10 _C_A)
PIPE
SURROUNDS
TRASH
SCREEN
Note:
Where pipework is located
under footpaths, verges and
other non-trafficked areas,
backfill material to be
agreed on site. Use of
struck material subject to
Engineer and Local
Authority approval.
Min. Trench Widths Vary According
To Pipe Dia. See Table Opposite.
Pipe Dia.
Varies See
Plan.
Note:
Applicable where pipework has more than
1200mm cover under trafficked areas or more
than 600mm under non-trafficked areas.
DOT Type 1 granular
backfill laid and compacted
in 150mm max. layers.
External Works construction
10mm dia. nom size
Pea gravel bedding
and surround.
Pipe Bedding Detail Type S
100
100
min.
min.
Min. Trench Widths Vary According
To Pipe Dia. See Table Opposite.
Min. Trench
Width (mm)
Pipe Dia. (mm)
Mass concrete encasement to be interrupted over
it's entire cross section @ each pipe joint using
'Korkpak' filler board by 'Servicised' or similar
approved.
Note:
No Mechanical compaction
techniques to be used within 300mm
of the crown of all pipework.
See Structural Engineers details for
pipework laid under buildings /
through foundations etc.
Pipe Bedding Detail Type A
Note:
Applicable where pipework has less than
1200mm cover under trafficked areas or less
than 600mm under non-trafficked areas.
150
150
Pipe Dia.
Varies See
Plan.
min.
min.
Grade ST4 mass concrete bed
and surround, 150mm thk min.
20mm nom. aggregate size.
DOT Type 1 granular
backfill laid and compacted
in 150mm max. layers.
External Works construction
Over 1200 Pipe Dia. + 1000
1050
1200
975
900
825
750
675
600
2300
2300
2000
1900
1600
1500
1450
1350
525
450
300
375
100
150
225
1200
1150
750
1050
550
600
700
Trench Widths:
Note:
Where pipework is located
under footpaths, verges and
other non-trafficked areas,
backfill material to be
agreed on site. Use of
struck material subject to
Engineer and Local
Authority approval.
NOTES
1. DO NOT SCALE THIS DRAWING. ALL DIMENSIONS MUST BE
CHECKED/ VERIFIED ON SITE. IF IN DOUBT ASK.
2. THIS DRAWING IS TO BE READ IN CONJUNCTION WITH ALL
RELEVANT ARCHITECTS, ENGINEERS AND SPECIALISTS
DRAWINGS AND SPECIFICATIONS.
3. ALL DIMENSIONS IN MILLIMETRES UNLESS NOTED
OTHERWISE. ALL LEVELS IN METRES UNLESS NOTED
OTHERWISE.
4. ANY DISCREPANCIES NOTED ON SITE ARE TO BE REPORTED
TO THE ENGINEER IMMEDIATELY.
c Copyright BWB Consulting Ltd
Drawing No. Revision
Drawing Status
Size
Drawing Title
Project Title
Scale
Reviewed
Drawn
A1
ISSUES & REVISIONS
Rev Date Details of issue / revision RevDrw
Client
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
Birmingham | 0121 233 3322
Leeds | 0113 233 8000
London | 020 7234 9122
Manchester | 0161 233 4260
Nottingham | 0115 924 1100
www.bwbconsulting.com
P2BMW/2155/W101
PRELIMINARY
A. Clifford
1:25
WATERCOURSE
DIVERSION TYPICAL
CROSS SECTION
CENTRUM WEST
ENABLING WORKS
REFER TO DRAWING
BMW/2155/W100 GENERAL
ARRANGEMENT FOR
SECTION LOCATIONS
HEADWALL ELEVATION SECTION HEADWALL CONSTRUCTION DETAIL
PIPE SURROUND DETAILS