Greater Nottingham Strategic Flood Risk Assessment … · Strategic Flood Risk Assessment...

Greater Nottingham

Strategic Flood Risk Assessment

Non-Technical Summary

July 2008

Greater Nottingham SFRA Partnership Greater Nottingham SFRA

Non-Technical SummaryErewash Borough Council

Erewash Borough NTS - Final.doc/ July 2008 (i)

GREATER NOTTINGHAM STRATEGIC FLOOD RISK ASSESSMENT

Non-Technical Summary

Contents

1 EXECUTIVE SUMMARY 1 2 INTRODUCTION 5 2.1 Introduction to the Project 5 2.2 Background to the Study 6 3 STUDY AREA, CONTEXT AND METHODOLOGY 9 3.1 Study Area 9 3.2 Existing Flooding Information 10 3.3 Methodology 11 4. RESULTS 17 4.1 River Trent Corridor 17 4.2 River Erewash 18 4.3 River Derwent and Other Watercourses 19 4.4 Other Sources of Flooding 20 4.5 Summary of Results 20 5. PLANNING IMPLICATIONS 21 5.1 Other Sources of Flooding 21 5.2 Climate Change 21 5.3 Development behind Defences/Embankments 21 5.4 Functional Floodplain 22 5.5 Access and Egress 22 5.6 Surface Water Drainage in New and Redeveloped Sites 23 6. SITE-SPECIFIC FLOOD RISK ASSESSMENTS 25 7 REPORT CONCLUSIONS 27 8. GLOSSARY OF TERMS AND ABBREVIATIONS 29 9. FURTHER INFORMATION 33 Appendix 1 - Maps



Erewash Borough NTS - Final.doc/ July 2008 (ii)

Document issue details:

B&V project no. 120824 Client’s reference no. BV-N2/MDC/00026

Version no. Issue date Issue status Distribution

1 October 2007 Draft Report

(electronic copy only)

Erewash Borough Council Environment Agency

2 July 2008 Final Report

Erewash Borough Council Environment Agency Nottingham Regeneration Limited -(digital copy only)

Version no. Principal Authors Principal Checker Principal Reviewer

1 Naomi Wing, EA Jenny Palmer, B&V Tim Palmer, B&V Naomi Wing, EA

Dave Brown, EBC

2 Naomi Wing, EA Jenny Palmer, B&V Peter Savill, EA Naomi Wing, EA

Dave Brown, EBC

Notice:

This report was prepared by the Environment Agency, Erewash Borough Council and Black & Veatch Limited (BVL) solely for use by Broxtowe Borough Council, Environment Agency, Erewash Borough Council, Gedling Borough Council, Nottingham City Council, Nottingham Regeneration Limited, Nottinghamshire County Council, Rushcliffe Borough Council and Severn Trent Water (the Greater Nottingham SFRA Partnership). This report is not addressed to and may not be relied upon by any person or entity other than the Greater Nottingham SFRA Partnership for any purpose without the prior written permission of BVL. BVL, its directors, employees and affiliated companies accept no responsibility or liability for reliance upon or use of this report (whether or not permitted) other than by the Greater Nottingham SFRA Partnership for the purposes for which it was originally commissioned and prepared.

Whilst all reasonable care has been taken in this assessment we cannot guarantee that during the lifetime of the flood risk assessment water levels may not exceed those stated. The report has addressed the risk of flooding from the River Trent, River Erewash, River Derwent, River Leen, Fairham Brook, Nethergate Brook, Day Brook and other watercourses/sources specifically mentioned only, and the conclusions stated in it are based on our best estimate using available data with a precautionary approach taken where possible. We have not assessed flood risks from sources other than those specifically referred to. We must make it clear that the assessment of weather generated flooding is inexact and that analysis is limited by the accuracy and availability of recorded data. Higher water levels may occur in the future due to the actions or omissions of third parties, or to poor maintenance, blockage, storm events in excess of the design standard quoted, inaccuracy or unavailability of data. Flooding beyond that estimated in this report may also occur due to climate change.

In producing this report, BVL has relied upon information provided by others. The completeness or accuracy of this information is not guaranteed by BVL.



Erewash Borough NTS - Final.doc/ July 2008 1

1 EXECUTIVE SUMMARY 1.1.1 This non-technical document summarises the key findings of the Greater Nottingham

Strategic Flood Risk Assessment (SFRA) for Erewash Borough Council and is designed to communicate to planners, landowners and developers the results of the study as they relate to land use planning within the borough.

1.1.2 The SFRA has taken account of the River Trent Fluvial Strategy, the Stapleford Flood

Alleviation Scheme, the Environment Agency’s Flood Zone Maps and anecdotal information held by a variety of sources, including information on Nut, Golden and Ock Brooks.

1.1.3 Therefore, for the Erewash Borough Council area, the SFRA primarily consolidates and

expands upon existing flooding information to provide a more complete picture of flood risk and its impact on planning. As such, there are no significant changes from existing published information listed above.

1.1.4 The Environment Agency remains the key custodian of flooding information and data for

Erewash Borough Council. However, the aim of the SFRA is to provide a map-based planning tool that can be used by planning officers at Erewash Borough Council to inform the Local Development Framework (LDF) process and individual planning applications.

1.1.5 Current planning policy encourages Local Planning Authorities (LPA) to maximise

development on brownfield land sites within the urban area and therefore the SFRA focuses on the risk of flooding to the urban areas. However, due consideration has been given to the risk of flooding from all sources that may impact upon both the greenbelt and its villages and also any future requirement for expansion around existing urban areas.

1.1.6 The SFRA is a non-statutory document and does not itself provide a sequential approach

as required by Planning Policy Statement 25: Development and Flood Risk1 (PPS 25). The SFRA however, provides the evidence base (e.g. mapping, data etc.) needed to inform the application of a sequential test in the determination of individual planning applications. Erewash Borough Council will therefore have due regard to PPS 25 and the results of the SFRA when considering the future use of land.

1.1.7 PPS 25 advises that following application of the Sequential Test and Exception Test,

development should not normally be permitted where flood defences, properly maintained and in combination with agreed warning and evacuation procedures, would not provide an acceptable standard of safety taking into account climate change (PPS 25/Paragraph G2).

1.1.8 Maps 6-EBC-01 to 06 show the current flood risk to the borough together with the

predicted increase under a climate change scenario with both the existing and proposed defences in place. Site-specific flood risk assessments should take account of this information in appraising flood risk both now and in the future and in the design of developments that are safe, taking full account of the likely impacts of climate change.

1PPS25 = Planning Policy Statement 25: Development and Flood Risk, CLG, 2006. This has an accompanying Practice Guide published in June 2008.




1.1.9 Both PPS 25 and its accompanying Practice Guide stress that risks will be greatest close to flood defences and new development should be sited away from existing flood defences except in exceptional circumstances, where a flood risk assessment shows how the building and its users will be made safe (PPS 25/Paragraph G2 and PPS 25 Practice Guide/Paragraph 7.12).

1.1.10 Table D1 of PPS 25 explains that only water compatible and essential infrastructure uses

are appropriate in the functional floodplain, subject to being designed and constructed to:

• remain operational and safe for users during times of flood; • result in no net loss of floodplain storage; • not impede water flows; and • not increase flood risk elsewhere.

1.1.11 PPS 25 requires that safe access and escape is available to and from new developments in

flood risk areas (PPS 25/Paragraph 8). The PPS 25 Practice Guide explains that wherever possible, safe access routes should be provided which are located above design flood levels and where this is not possible, limited depths of flooding may be appropriate provided that the proposed access is designed with appropriate signage etc. to make it safe. The acceptable flood depth for safe access will vary depending on flood velocities and the risk of debris within the flood water (PPS 25 Practice Guide/Chapter 4/Paragraph 4.55).

1.1.12 Therefore, site-specific flood risk assessments should have due regard to the depths and

velocities of flood water as per Table 3.1 in Section 3 and to the hazard rating maps prepared as part of the SFRA and included in Volume 1 of the technical report.

1.1.13 PPS 25 requires that, as a minimum standard, major development proposals within the

borough shall not exacerbate the existing flooding situation in terms of surface water run-off generated. Further, it requires that the volumes and peak flow rates of surface water drainage leaving a developed site should be no greater than the rates prior to the proposed development, unless specific off-site arrangements are made (PPS 25, Paragraph F10).

1.1.14 Priority should be given to the use of Sustainable Drainage Systems (SUDS) and green

infrastructure in meeting the objectives of PPS 25 and should be considered as part of a site-specific flood risk assessment (PPS 25 Paragraphs 6, 8 and E3).

1.1.15 The SFRA does not provide specific flood risk information for individual sites. However,

those proposing development will need to utilise the flood dynamic maps, flood hazard information, general discussion in the SFRA and this Non-Technical Summary as the starting point for considering flood risk to development proposals.




Note for Developers/Landowners The Strategic Flood Risk Assessment (SFRA) represents the best currently available flooding information for the Erewash Borough Council area and should be the starting point for establishing the risk of flooding to sites. However, the SFRA does not replace the need for a site-specific flood risk assessment to look at the flood risk and mitigation options for your individual site. Further advice on the process for undertaking a site-specific flood risk assessment is included in Section 6 of this document. It is important that when considering flooding to your individual site, you give due regard to climate change and the impact of proposed flood mitigation measures on flood risk to land elsewhere. Further advice on flood protection measures can be found in the Department of Communities and Local Government (DCLG) publication entitled ‘Improving the Flood Performance of New buildings’ available at: http://www.planningportal.gov.uk/uploads/br/flood_performance.pdf and the Office of the Deputy Prime Minister (ODPM) publication ‘Preparing for Floods’ available at: http://www.planningportal.gov.uk/uploads/odpm/4000000009282.pdf?lang=_e The Environment Agency will expect a site-specific flood risk assessment to consider sustainable forms of surface water management (e.g. SUDS) in preference to traditional forms of drainage. Further advice can be found in the Construction Industry Research and Information Association (CIRIA) publication ‘SUDS Design Manual for England and Wales’ or www.ciria.org/suds/ The Environment Agency encourages pre-planning discussions, in particular of major developments, in order to establish the constraints to delivery of sites at the earliest opportunity. You should also discuss application of the flood risk Sequential Test with the Planning Case Officer at Erewash Borough Council.




This page is intentionally left blank.




2 INTRODUCTION 2.1 Introduction to the Project 2.1.1 In December 2006, Black and Veatch (B&V) began a study into flood risk from the River

Trent and its key tributaries through the Nottingham Core Housing Market Area on behalf of the Greater Nottingham Strategic Flood Risk Assessment Partnership (GNSFRA), which comprises:

• Broxtowe Borough Council • Environment Agency • Erewash Borough Council • Gedling Borough Council • Nottingham City Council • Nottingham Regeneration Limited • Nottinghamshire County Council • Rushcliffe Borough Council • Severn Trent Water.

2.1.2 The Strategic Flood Risk Assessment (SFRA) as a complete package, draws upon updated

river modelling and survey data to predict how the River Trent and its key tributaries will react during various storm events, including the key planning benchmark - the 1 in 100 annual chance flood event2.

2.1.3 For the Erewash Borough Council area, the SFRA primarily consolidates and expands

upon existing flooding information to provide a more complete picture of flood risk and its impact on planning. For the majority of the borough there are no significant changes from existing published information.

2.1.4 The SFRA differs from the Environment Agency’s Flood Zone Maps by providing flood

mapping based upon a snap shot in time of flood risk taking into account existing flood defences. The Flood Zone Maps ignore the presence of man made structures (e.g. flood defences, railway embankments etc.). The flood maps produced by the SFRA do not replace the Flood Zone Maps but compliment them by providing more detailed flooding information on the River Trent and its key tributaries. The Flood Zone Maps continue to provide valuable information on local watercourses.

2.1.5 The Environment Agency remains the key custodian of flooding information and data for

Erewash Borough Council. However, the aim of the SFRA is to provide a map-based planning tool that can be used by planning officers at Erewash Borough Council to inform the Local Development Framework (LDF) process and the determination of individual planning applications.

2.1.6 This summary document helps planners at Erewash Borough Council to have due regard

to flooding issues at the various stages of the planning process (e.g. Local Development Framework, Master Plans and planning applications) taking into account progress of the Environment Agency’s proposed Nottingham Trent Left Bank Flood Alleviation Scheme (FAS).

2 Probability of flooding is expressed in terms of the statistical likelihood of an event being exceeded in a given year, such as “the 1 in 100 annual chance flood event” or similar. This is often abbreviated as the 1 in 100 year flood, or simply the 100 year flood. It is essential to appreciate that the 1 in 100 chance flood may re-occur in less than 100 years.




2.1.7 This document also helps steer new development away from areas of highest risk by applying the flood risk Sequential Test as set out in Planning Policy Statement 25: Development and Flood Risk (PPS 25) and assist with emergency planning.

2.1.8 The primary outputs of the SFRA are:

• more accurate flood maps indicating areas of flooding at the 1 in 20, 1 in 100, 1 in 100 plus an appropriate allowance for climate change and 1 in 1000 annual chance flood events;

• flood dynamic plans illustrating depths and direction of anticipated flows and flood hazard plans attributing a hazard rating; and

• other sources of flooding maps consolidating factual and anecdotal evidence held by a variety of sources on other sources of flooding within the borough e.g. sewer flooding, drainage issues, groundwater flooding etc.

2.1.9 Flood hazard maps have been produced to provide information on the varying degrees of

risk within the floodplain based upon the predicted depths and velocities of flood water. Further information on flood hazard ratings is provided in Table 3.1. Breach maps have also been prepared to show the impact of failure of the flood defences on flood risk. Together, the flood hazard maps and breach maps will help inform land use planning decisions on the allocation of land for development and application of the flood risk Sequential Test.

2.1.10 Full copies of the report for all of the Local Planning Authorities (LPA) forming the

Greater Nottingham SFRA Partnership containing comprehensive technical information on methodology, modelling approach etc. are available for inspection at the Environment Agency’s offices in West Bridgford, Nottingham. Copies of the technical and this non-technical document as they relate to Erewash Borough Council are also available for public inspection at the Town Hall, Derby Road, Long Eaton and Ilkeston Town Hall, Wharncliffe Road.

2.1.11 This document summarises the key findings of the study for Erewash Borough Council

and is designed to communicate to planners, landowners and developers the results of the study as they relate to land use planning within the Erewash Borough Council area.

2.2 Background to the Study 2.2.1 In 2004 the Planning and Compulsory Purchase Act introduced comprehensive reforms to

the planning system which replaced Local Plans with LDFs. LDFs are a ‘portfolio’ of documents known as Local Development Documents (LDD), which outline the spatial planning strategy for the local area.

2.2.2 LDD should reflect the Government’s policies for sustainable development, which

includes avoiding new development in areas at risk of flooding and taking climate change impacts into account in the location and design of development (PPS 25/Annex A3).




2.2.3 This message is further reinforced in PPS 25 and its accompanying Practice Guide, which requires planners to take account of flood risk at all stages of the planning process in order to avoid inappropriate development in areas at risk of flooding and to steer new development toward areas of lowest flood risk (PPS 25/Paragraph 5).

2.2.4 In order for planners to do this, it is first necessary to appraise the risk of flooding from all

possible sources (e.g. rivers, sewers, groundwater, canals etc.) and the impact of climate change on flood risk and then to frame policies which seek to avoid flood risk to people and property, where possible. This is achieved through the preparation of a SFRA for the borough.

2.2.5 This SFRA was commissioned to provide information on the flood risk and the impact of

climate change on flooding within the Erewash Borough Council area so that decisions can be made on land use planning both at a policy level and on everyday planning applications, based upon sound science. However, the SFRA does not replace the need for developers to prepare site–specific flood risk assessments but rather it provides an overview of flood risk at a catchment-wide scale. Further advice on the requirements of site-specific flood risk assessments is included in Section 6.

2.2.6 When considering land use allocations and everyday planning applications, PPS 25

requires planners to demonstrate that a risk-based sequential approach has been applied. This risk-based sequential approach states that development should first take place in areas of lowest flood risk. Where there are no lower risk sites reasonably available, development proposals need to be safe, taking into account the vulnerability of land uses to flooding (PPS 25/Paragraphs 16 and 17).

2.2.7 If, following application of a Sequential Test, it is not possible, consistent with wider

sustainability objectives, for development to be located in areas with a lower probability of flooding then the Exception Test should be applied. The Exception Test requires development to:

• demonstrate that sustainability benefits outweigh the negative impact of

flooding; • be on developable previously-developed land or that there are no reasonable

alternative sites on developable previously-developed land; • be supported by a flood risk assessment that demonstrates that development

will be safe without increasing flood risk elsewhere; and • reduce overall flood risk where possible.

2.2.8 The SFRA is a non-statutory document and does not itself provide a sequential approach

as required by PPS 25. The SFRA however, provides the evidence base (e.g. mapping, data etc.) needed to inform the application of a sequential test in the determination of individual planning applications and to the allocation of land. Erewash Borough Council will therefore have due regard to PPS 25 and the results of the SFRA when considering the future use of land.




2.2.9 Paragraph 3.37 of the PPS 25 Practice Guide summarises the key role of a SFRA is to allow LPA to:

• fully understand flood risk from all sources within its area and also the risks

to and from surrounding areas in the same catchment; • inform the Sustainability Appraisal so that flood risk is fully taken account

of when considering options and in the preparation of LPA land use policies;

• prepare appropriate policies for the management of flood risk within LDD; • identify the level of detail required for site-specific flood risk assessments in

particular locations; and • enable planners to determine the acceptability of flood risk in relation to

emergency planning capability. 2.2.10 In terms of the PPS 25 Practice Guide, this SFRA constitutes a Level 2 assessment and

provides a comprehensive assessment of the risks of flooding both now and with an allowance for climate change; detailed flood hazard information; breach mapping; and an appreciation of the varying degrees of flood risk within a flood zone. A full list of the expected outputs of a Level 2 SFRA can be found in Paragraph 3.57 of the PPS 25 Practice Guide.

2.2.11 The Government has recently published Planning Policy Statement (PPS): Planning and

Climate Change3, a supplement to Planning Policy Statement 1 on Sustainable Development which sets out how planning should contribute to reducing emissions, stabilising climate change and taking into account unavoidable consequences.

2.2.12 A key decision-making principle of the PPS on Planning and Climate Change is that new

development should be planned to minimize future vulnerability in a changing climate. The SFRA provides information on the likely impact that climate change will have on flood risk in Greater Nottingham to inform land use planning decisions.

2.2.13 The Environment Agency has project managed and given technical advice to the GNSFRA

Partnership. However, as a specific consultation body, this involvement does not guarantee that the Environment Agency will support the LDD, rather it opens dialogue and helps identify areas of concern at the earliest possible stage in the plan-making process.

2.2.14 The SFRA will be reviewed when significant events occur, which require updates to the

mapping (e.g. flood event, relevant changes to planning policy, defence works or development affecting major floodplain compensation/ storage areas etc.).

3 PPS1 = Delivering Sustainable Development, CLG, 2005. This has a supplementary document entitled Planning Policy Statement: Planning and Climate Change, CLG, 2007.




3 STUDY AREA, CONTEXT AND METHODOLOGY 3.1 Study Area 3.1.1 Erewash Borough Council’s area covers 10,930 hectares of land, including several larger

urban areas. These include Long Eaton, Breaston, Sandiacre, Ilkeston and Borrowash, as shown on Map 6-NTS-01. There are three designated regeneration zones which are earmarked for major redevelopment. These are at Stanton south of Ilkeston, Long Eaton Town Centre and Ilkeston Town Centre. Erewash Borough Council has prepared a Master Plan for Stanton and Area Action Plans for Long Eaton and Ilkeston Town Centres showing the Council’s commitment to regeneration.

3.1.2 The watercourses within the borough which have been considered by the SFRA are shown

on Map 6-GEN-01. 3.1.3 The River Trent is the largest watercourse in Nottingham and enters Erewash Borough

Council’s area at its confluence with the River Derwent, approximately 1.5km east of Great Wilne leaving the borough at its confluence with the River Erewash.

3.1.4 Within the Erewash Borough Council area, there is also a risk of flooding from other

watercourses, predominantly the Rivers Derwent and Erewash but including others such as Nut, Ock and Golden Brooks as well as the very significant risk to Sawley and Long Eaton from the River Trent.

3.1.5 Current planning policy encourages LPA to maximise development on brownfield land

sites within the urban area and therefore the SFRA focuses on the risk of flooding to urban areas. However, due consideration has been given to the risk of flooding from all sources that may impact upon both the greenbelt and its villages and also any future requirement for expansion around existing urban areas.

3.1.6 An existing ISIS4 model of the River Erewash, produced by Jeremy Benn Associates Ltd

(JBA), has been used to produce a set of flood dynamic plans for between the M1 motorway bridge near Trowell and the railway bridge upstream of Attenborough Lakes. The plans show flood outlines for the 1 in 20, 1 in 100 and 1 in 1000 annual chance flood events. No flood mapping was available for the 1 in 100 annual chance flood event plus an allowance for climate change.

3.1.7 None of the other watercourses in this borough have been individually modelled (with

sufficient accuracy to allow flood maps to be produced). Therefore, the only other data available for the borough are the Environment Agency’s Flood Zone Maps. These maps were generated from a relatively simple modelling technique using NEXTMap data for the ground elevations. As NEXTMap has a limited vertical accuracy (+/-1m) the resulting flood outline can sometimes be misleading. Therefore, any development proposals highlighted as at risk from these watercourses should use the SFRA as a starting point, and include a site-specific flood risk assessment, which may require more detailed flooding information and supporting modelling as appropriate.

4 ISIS – a type of river modelling software




3.2 Existing Flooding Information

River Trent Corridor 3.2.1 In March 2005, the Environment Agency produced the River Trent Fluvial Strategy which

assessed the risk of flooding from the fluvial stretch of the River Trent from Stoke on Trent to the tidal limits at Cromwell Lock, downstream of Newark on Trent.

3.2.2 The River Trent Fluvial Strategy is a high level document and its purpose was to appraise

options to mitigate the flooding situation and to recommend future flood alleviation works. The Strategy established that the current flood defences through Nottingham do not provide the standard of protection required and recommended that new defences be constructed.

3.2.3 The Environment Agency is currently considering the alignment and height of these

proposed defences and their impact elsewhere. Subject to obtaining the appropriate permissions and funding, it is envisaged that construction of the Nottingham Left Bank FAS would start sometime after 2009.

3.2.4 The Nottingham Left Bank FAS covers some 27 km, beginning at Sawley and ending at

Radcliffe Railway Viaduct in Colwick. It will be designed to protect over 15,000 homes from flooding by the River Trent. The Environment Agency completed the West Bridgford Flood Alleviation Scheme in 2007.

3.2.5 National guidelines on the standard of protection offered by flood alleviation schemes are

set by the Department for Environment, Food & Rural Affairs (Defra). The West Bridgford FAS was designed to provide up to a 1 in 100 year flood protection for existing properties. It is expected that the Nottingham Left Bank FAS will offer a similar standard of protection. The proposed flood defences are designed to be adaptable to future increases in river levels associated with climate change although new development proposals will need to give careful consideration to the increased risk of flooding with climate change and some development behind the new defences may not be sustainable.

3.2.6 The model produced by the River Trent Fluvial Strategy is the basis for the SFRA flood

analysis. However, it has been necessary to update the model in order to provide information such as climate change flood outlines and hazard ratings, which are required for planning purposes and by PPS 25.

River Erewash

3.2.7 The River Erewash flows from Kirkby Woodhouse and flows into the Attenborough Lakes

which discharge into the River Trent. Along its length it flows through several urban areas to the west of Nottingham. These include Heanor, Eastwood, Ilkeston, Stapleford and Long Eaton.

Other Watercourses

3.2.8 Although the SFRA has concentrated on the risk of river flooding from the Rivers Trent and Erewash, information on the following watercourses has been included.

3.2.9 Nut Brook flows from near Mapperley, to the east of Ilkeston, past Kirk Hallam and joins

the Erewash south of Trowell. Golden Brook begins south of Risley, flows around Breaston and through Long Eaton before joining the Erewash at the Attenborough Lakes. Ock Brook flows through Ockbrook and Borrowash before joining the Derwent.




Other Sources of Flooding 3.2.10 Existing information has been collated on other sources of known flooding in Erewash

Borough Council’s area (e.g. surface water drainage, highway drainage, groundwater etc.) from a variety of anecdotal and factual sources including Severn Trent Water, an Erewash Borough Council Drainage Engineer and Parish Councils in the borough.

3.3 Methodology

River Trent Corridor 3.3.1 In order to build upon the existing River Trent Fluvial Strategy for planning purposes, it

was decided to undertake a linked one-dimensional/two-dimensional modelling5 exercise for the River Trent through the study area. This method provides more accurate information and representation of the floodplain than the previous modelling. This level of detail is critical for planning purposes and also because of the complexity of the floodplain through Nottingham.

3.3.2 First, it was necessary to obtain ground level data using a technique known as LiDAR

(Light Detection And Ranging). LiDAR detects ground levels by measuring the delay between a pulse of light emitted toward the ground and the time taken to receive the reflected signal back in the aircraft. The data were filtered to remove buildings and trees in order to give ground levels. For the River Trent corridor, the LiDAR data used has a vertical accuracy of +/15cm. This is well within the Environment Agency’s tolerance of +/-25cm.

3.3.3 The LiDAR data were reviewed and key structures that could obstruct or convey flood

water were highlighted e.g. canals, railway and road embankments etc. The consultants undertook site visits to record any key openings through the roads and railway embankments that may influence the flow of water in the floodplain. These structures and openings were then incorporated into the model.

3.3.4 Existing river models for the River Trent and its main tributaries through the study area

were included in the SFRA model of the River Trent e.g. the Rivers Erewash and Leen, so that a full picture of the risk of flooding and interaction of the River Trent with other watercourses could be formed.

3.3.5 The SFRA model was then run using flow data from the November 2000 flood event and

the resulting flood outlines compared against actual flooding data and photographs taken during November 2000. For the 41 observations that coincided exactly with the model predictions, there was an average difference in level of 158mm; the maximum was 379mm and the minimum 2mm. This exercise shows that the SFRA model calibrates well to the November 2000 flood providing confidence in the results and flood maps.

3.3.6 The calibrated and verified SFRA model was then run at a 50m coarse grid size for general

checks and testing and at a 15m fine grid size for producing the detailed floodplain maps. 3.3.7 Paragraph 4 of PPS 25 advises that present and future flood risk should be taken into

account in order to avoid, reduce and manage flood risk through positive planning. To accord with these requirements, the model was run at a 1 in 20, 1 in 100, 1 in 100 plus an allowance for climate change and 1 in 1000 annual chance flood event for the following scenarios:

5 See Volume 1 of the technical report for details.




3.3.8 For the defences breached scenarios, the SFRA model was run 14 times for the 1 in 100

annual chance flood event both with and without the proposed defences, each time with a breach in the flood defences at a different location. The purpose of this exercise was to understand the risk of flooding to developments immediately behind the flood defences and to map a maximum flood envelope.

3.3.9 The data on flood depths and velocities from each of the model runs was then translated

into a flood hazard rating by applying research undertaken by the Environment Agency and Defra6 (see Table 3.1). This information helps planners to understand the varying degrees of risk within a flood zone and informs emergency planning and evacuation decisions.

Table 3.1 – Flood Hazard Rating Table

Degree of Flood Hazard Hazard Rating Description

Low <0.75 Caution Flood zone with shallow flowing water or deep standing water.

Moderate 0.75 – 1.25 Dangerous for some

Danger: flood zone with deep or fast flowing water.

Significant 1.25 – 2.50 Dangerous for most people

Danger: flood zone with deep fast flowing water.

Extreme >2.50 Dangerous for all

Extreme danger: flood zone with deep fast flowing water.

6 Defra ‘Research on Flood Risks to People FD2321 Rev0.2 Phase2’ available at www.hydres.co.uk

With existing flood defences

With defences not breached

With defences breached

With defences not breached

With defences breached

With proposed flood defences




River Erewash 3.3.10 In 2005, JBA built a river model7 which extends along the River Erewash from close to

Kirkby Woodhouse (SK 4902 5489) to the confluence with the River Trent. In 2006, using the results from the JBA modelling study, B&V carried out a pre-feasibility study for the Stapleford FAS8, from the M1 motorway bridge just downstream of Trowell to the railway bridge just north of Attenborough Lakes. As part of this study, a 1 in 100 annual chance flood event outline was drawn along the River Erewash.

3.3.11 Included in the brief for this SFRA is that the 1 in 100 annual chance flood event plus an

appropriate allowance for climate change outline should be included on the plans. This outline was not available along the River Erewash and is therefore not included on the plans.

3.3.12 The approximate flood depths marked on the plan have been calculated by comparing the

1 in 100 annual chance flood event peak water level from the JBA study with the approximate ground levels. The ground levels have been taken either from the cross-sections in the model or from the threshold survey undertaken as part of the Stapleford FAS study. The causes of the flooding along the River Erewash, where known, have been added to improve the understanding of the floodplain maps produced. As the model has been built by JBA not all of the causes may be included on the plans.

3.3.13 It should be noted that due to the modelling methods used by JBA to model the area

between Toton weir and A6005 Nottingham Road, where the Erewash splits into a main and a by-pass channel, there are differences in the calculated 1 in 100 annual chance flood event levels in the two channels. As it would be expected that the flood levels in both channels would be broadly similar, this is not considered to be a realistic interpretation of the actual flooding situation. The Environment Agency is currently considering additional modelling to improve the predicted flood levels.

River Derwent Corridor

• Draycott

3.3.14 The village of Draycott lies at the edge of the River Derwent floodplain, but is only 3km

from the River Trent. As the area is relatively flat, the River Trent influences the water level in the River Derwent as far upstream as Borrowash Bridge. Draycott lies downstream of the maps available from the Environment Agency’s Derby Strategy.

3.3.15 The potential flooding indicated by the Flood Zone Maps show that there is some risk to

property on the southern edge of the village (see Map 6-GEN-02). A comparison of NEXTMap and LiDAR data indicated that NEXTMap elevations are, in general, higher than those defined by LiDAR. As LiDAR is generally more accurate than NEXTMap, this suggests that the flooding could be deeper and possibly more widespread than the Flood Zone Maps indicate.

• Ock Brook

3.3.16 This brook is made up of a number of smaller streams which converge at SK 4285 3618.

The brook then flows past the village of Ockbrook through Borrowash before flowing into the River Derwent.

7 River Erewash SFRM, Hydraulic Modelling Report, JBA, 2005 8 Stapleford Flood Alleviation Scheme, Viability Report, B&V, 2005




3.3.17 The LiDAR data at the downstream end of the brook suggests that the channel is better defined than NEXTMap shows (see Map 6-GEN-03). This may mean that water could be confined to a narrower flood outline than the Flood Zone Map indicates. However, at this downstream location, if the volume of water was to exceed the capacity of the channel, then flooding could be extensive on the lower lying left bank. Extensive flooding could also occur on the right bank for the upstream section near the village of Ockbrook, as shown on Map 6-GEN-03.

• Church Wilne 3.3.18 A comparison of the LiDAR and NEXTMap data near Church Wilne shows that both data

sets indicate the steeply rising ground at the edge of the floodplain. Therefore, the extent of flooding predicted by the Flood Zone Maps is probably correct. However, the ground elevations in NEXTMap are generally higher than the LiDAR data which suggests that the flooding might be deeper in some locations. Where the ground slope is less steep, these elevation differences mean that localised variations in the edge of the flood outline could occur; such as the example shown in Map 6-GEN-04.

• Nut Brook 3.3.19 This brook is made up of two main tributaries, which converge north of Kirk Hallam, (SK

4527 4108) and meet the River Erewash near Trowell; approximately 4km later. 3.3.20 As with the other brooks, Nut Brook has not been modelled and the only flood risk

information available is the Flood Zone Maps. Only NEXTMap data and OS maps are available to check the validity of these outlines. A comparison of five Landline spot heights on Merlin Way (near Stanton Works) shows that NEXTMap data are between 0.7m and 3.6m higher than the OS spot heights. This location is indicated on Map 6-GEN-05. As the flood outline was generated using NEXTMap data the flooding in this area could be more significant than the Flood Zone Maps indicate.

• Golden Brook

3.3.21 This brook starts at around SK 4535 3704 and runs for approximately 11km, joining the

River Erewash at SK 5080 3361 (see Map 6-GEN-06). 3.3.22 The original Flood Zone outlines show much of Long Eaton to be at risk of flooding.

However, the SFRA model of the River Trent shows that less of Long Eaton would flood during a 1 in 100 annual chance flood event on the River Trent than previously shown. However, those parts that do flood from the Trent may have a significant hazard rating. Areas of Long Eaton may also be at risk of flooding from Golden Brook. However, this cannot be quantified as there is model for the area.

3.3.23 The village of Breaston is located on high ground so there is little possibility of Golden

Brook causing flooding in the village. 3.3.24 Once the brook crosses the M1 motorway, it passes through the heavily urbanised area of

New Sawley. To the north of the brook the ground is still high and at little risk of serious flooding, though some localised flooding may occur. The area to the south is all low lying and there is a potential of flooding in this area. However, without a detailed hydraulic study, it is not possible to state the location and extent of this potential flooding.




• Borrowash 3.3.25 Borrowash is at the most downstream extent of the Environment Agency’s Derby

Strategy5 for which accurate flood maps are available. However, as the settlement is approximately 6m above the floodplain of the River Derwent, there is no risk of flooding from the Derwent. Other Watercourses

3.3.26 Only the Rivers Trent and Erewash have been modelled in this borough. The only data

available in the SFRA for Nut, Golden and Ock Brooks are the Environment Agency’s Flood Zone Maps. These maps were generated from a relatively simple modelling technique using NEXTMap data for the ground elevations. Plans have been drawn showing the existing level of knowledge around Draycott (at risk from the River Derwent), Church Wilne (at risk from the River Derwent) and along Ock Brook. Other Sources of Flooding

3.3.27 In order to understand other, non-main river sources of possible flood risk, information

was collated from the following sources and is discussed in Section 4.4:

• Drainage Engineer at Erewash Borough Council; • Sewer Flooding Manager and Asset Protection Manager at Severn Trent

Water; and • Parish Councils within the borough.




4. RESULTS 4.1 River Trent Corridor

Flood Risk with Existing Defences 4.1.1 The first scenario tested by the SFRA model was the existing situation which includes the

recently completed West Bridgford flood defences but does not take into account the proposed Nottingham Trent Left Bank FAS. The purpose of testing this scenario is to understand the short term flood risk to the borough until the flood defences from Sawley to Colwick have been completed.

4.1.2 The results of this scenario, as shown on Maps 6-EBC-01 to 03, indicate that during a 1 in

100 annual chance flood event, the existing defences at Sawley overtop leading to flooding throughout the area along Plant Avenue and several roads off Tamworth Road including Shaftesbury Avenue, Reedman Road and Netherfield Road. Most of the area between Tamworth Road and the existing defences floods.

4.1.3 The flood water flows north through Sawley underneath the railway along Tamworth

Road, flooding a considerable number of residential properties and the Acton Road Industrial Estate.

4.1.4 Most of the land and properties on the riverside of the defences in this area flood to depths

of between 1.09 – 3.41m, although two areas flood to depths of 6.25m and 7.05m. 4.1.5 The flood defences at Trent Meadows are also predicted to overtop during this event

leading to properties along Newbery Avenue, Owen Avenue and Meadow Lane flooding. The flood water flows along Meadow Lane leading to flooding on Barton Road, Chatsworth Avenue and Clifton Avenue. Once the flood water passes underneath the railway along Meadow Lane it also reaches a small industrial area.

4.1.6 The River Trent also floods the area of open land between the railway line and

Nottingham Road and the riding school. 4.1.7 In the 1 in 1000 annual chance flood event almost all of Sawley village between the river

and Draycott Road floods, with the exception of the church and surrounding area. The flood water crosses Draycott Road in two locations leading to significant flooding in the area between the road and the railway line.

4.1.8 Once the flood water passes under the railway line along Tamworth Road, the area around

Wilsthorpe Road and Ruskin Avenue floods and the flow path continues along Milldale Road and Wensleydale Road into New Sawley.

4.1.9 Properties between Wilsthorpe Road and Tamworth Road flood, almost as far north as the

Industrial Estate on Derwent Street. 4.1.10 In the Acton Road Industrial Estate the flooding is considerably more significant including

properties along Collingwood Road, Oakley’s Road, Cobden Street, Lower Brook Street and Fields Park Road. Included in this area are three schools, an ambulance station, a church, a library and a considerable number of residential properties.




Flood Risk with Existing Defences Improved

4.1.11 The second scenario tested by the model was the risk of flooding with the proposed Nottingham Trent Left Bank FAS in place. It was assumed that the proposed defences would provide a minimum of 1 in 100 year standard of protection against flooding with 200mm freeboard. Freeboard is an allowance added to flood defences to take account of a) uncertainty in assessing the flood levels (e.g. uncertainty in the flood modelling) and b) other physical effects (e.g. waves, settlement of flood banks) that have not been included elsewhere.

4.1.12 The Environment Agency is currently considering the alignment and height of the

proposed flood defences and their impact elsewhere. Subject to obtaining the appropriate permissions and funding, it is envisaged that construction would start some time after 2009.

4.1.13 This scenario is important to provide an indication of flood risk in the longer term and to

inform land use decisions to ensure that new development is sustainable. The results of this scenario are shown on Maps 6-EBC-04 to 06.

4.1.14 With the proposed Nottingham Trent Left Bank FAS in place, the borough will be

protected from flooding by the River Trent during a 1 in 100 annual chance flood event up to the limits of the proposed scheme at Radcliffe Viaduct.

4.1.15 During a climate change scenario, the proposed flood defences are expected to overtop and

show similar patterns of flooding to that predicted under the existing scenario (e.g. without the proposed flood defences) including an allowance for climate change. This is because the Environment Agency’s proposed defences are unlikely to be built to prevent flooding during a climate change scenario, which is close to a 1 in 1000 annual chance flood event.

4.2 River Erewash 4.2.1 The flood dynamic plans for the River Erewash through the Erewash Borough Council

area are included in Appendix 1 as Maps 2-FDP-01 to 10. 4.2.2 The plans show that during the 1 in 20 annual chance flood event, open land on either side

of the River Erewash floods in addition to some properties around Ilkeston Junction. 4.2.3 For the 1 in 100 annual chance flood event, the flood outline shows that flooding is limited

to pockets of property flooding along the length of the River Erewash. The area of Ilkeston Junction that floods increases slightly, and the flood depths vary between 0.19m and 1.26m. Further downstream an Industrial Estate at Gallows Inn and several properties on Brooke Street are shown to flood to a depth of around 2m.

4.2.4 Downstream of the M1, the 1 in 100 annual chance flood outline has been shown assuming that the existing defences have been breached. The flood outline without the defences breached was not available to the SFRA as it was not included in the JBA model built in 2005.

4.2.5 As the River Erewash passes between Stapleford and Sandiacre, it begins to cause

significant levels of flooding to both residential and non-residential properties. In Sandiacre, the outskirts of the Orchard Business Park and properties between the river and Town Street also flood almost as far downstream as the A52(T). Some flood water does get across Town Street to flood several more properties on Hall Drive and Edward Street.




4.2.6 In the area between the A52(T) and the A6005, water flows out of the River Erewash, assuming the existing defences breach, leading to flooding on Bennett Street, Bridge Street, Britannia Road, Hamilton Road, Royal Avenue, Hemlock Avenue and Dale Avenue.

4.2.7 During the 1 in 1000 annual chance flood event there is little difference between the 1 in

100 and the 1 in 1000 annual chance flood outlines upstream of Newton’s Lane at Cossall. Downstream of Newton’s Lane flooding of several isolated properties, garages and allotments occurs.

4.2.8 At Larklands, non-residential properties on the land between the River Erewash and the

Erewash Canal are shown to flood, during the 1 in 1000 annual chance flood event. Several more properties flood at Gallows Inn, again on land between the river and the canal.

4.2.9 In the area where Station Road crosses the River Erewash the extent of flooding during a 1

in 1000 annual chance event is much larger than for the smaller events. Some of the Orchard Business Park is shown to flood as are Gas Street, Cross Street, areas of Town Street, Bridge Street and the Council Offices and warehouses between Station Road and the A52(T).

4.3 River Derwent and Other Watercourses 4.3.1 Some areas of Draycott are shown to be at risk of flooding on the Environment Agency’s

Flood Zone Maps. Properties on Lime Grove, Derwent Street, and South Street flood in the 1 in 100 annual chance event (Flood Zone 3). For the 1 in 1000 annual chance event (Flood Zone 2) the area at risk of flooding expands to include the poultry farm and properties on Fowler Street, Sawley Road and Attewell Close.

4.3.2 Around Draycott there is a significant amount of agricultural land that is flooded by the

River Derwent. 4.3.3 As Ock Brook passes through the village of Ockbrook itself, the Flood Zone Maps show

that the only area where properties are at risk of flooding is on Cole Road where Ock Brook passes underneath.

4.3.4 In Borrowash, properties on either side of the channel (between 10-20m away) are at risk

from Ock Brook according to the Flood Zone Maps. There is no significant difference between 1 in 1000 annual chance flood event (Flood Zone 2) and 1 in 100 annual chance flood event (Flood Zone 3) outlines in this area.

4.3.5 The villages of Church Wilne and Great Wilne are both shown as being at risk of flooding

from the Rivers Derwent and Trent in the 1 in 100 annual chance flood event. 4.3.6 The Flood Zone Maps for both Nut and Golden Brooks indicate that only very localised

flooding is likely to occur.




4.4 Other Sources of Flooding

4.4.1 Anecdotal and factual information was gathered on other possible sources of flooding and this information is consolidated on Maps 1-OTH-01 to 03 (included in Volume 1 of the technical report). These maps indicate areas of drainage and sewer problems, flooding from surface water, sites where sandbags have been provided and identifies key assets such as balancing ponds, flood storage lagoons and sewage pumping stations.

4.5 Summary of Results 4.5.1 The primary source of flooding to the borough is the River Trent and flooding is expected

to impact upon Sawley, Long Eaton, and agricultural land at Attenborough Junction during a 1 in 100 annual chance flood event.

4.5.2 A significant number of local roads are predicted to flood during the 1 in 100 annual

chance flood event. 4.5.3 The Environment Agency has proposals to improve the standard of flood protection to

Sawley and Long Eaton, which are covered by the Nottingham Trent Left Bank FAS. 4.5.4 The SFRA predicts that climate change will increase flooding of the River Trent close to

the 1 in 1000 annual chance flood outlines and more extensive flooding is expected in New Sawley.

4.5.5 The SFRA shows similar patterns of flooding to the Environment Agency’s Flood Zone

Maps. 4.5.6 Significant pockets of flooding are expected to be caused by the River Erewash. 4.5.7 A number of settlements within the borough are at risk of flooding from the River

Derwent. This has not been specifically modelled as part of the SFRA although information on this flood risk has been included based on a variety of sources.

4.5.8 Ock Brook is shown to flood properties in Ockbrook and Borrowash during both the 1 in

100 and 1 in 1000 annual chance flood events. 4.5.9 The Flood Zone Maps for both Nut and Golden Brooks indicate that only very localised

flooding is likely to occur.




5. PLANNING IMPLICATIONS 5.1 Other Sources of Flooding 5.1.1 Planning Policy Statement 25 explains that all forms of flooding and their impact on the

natural and built environment are material planning considerations (Paragraph 3) and that a number of forms of flooding present a range of different risks (Paragraph C1).

5.1.2 PPS 25 is clear that flood risk assessments should consider all forms of flooding and Maps

1-OTH-01 to 03 (included in Volume 1 of the technical report) provide the starting point for this appraisal.

5.2 Climate Change 5.2.1 Paragraph 6 of PPS 25 states that policies should be framed for the location of

development which avoids flood risk to people and property where possible and manages any residual risk, taking account of the impacts of climate change.

5.2.2 A Working Draft of Practice Guidance to support the PPS on Planning and Climate

Change was published in March 2008 which provides guidance on how planning should secure new development and shape places resilient to the effects of climate change. The Working Draft Practice Guidance is available on the Department of Communities and Local Government website.

5.2.3 The flood dynamic plans (included in Volume 1 of the technical report) show the predicted

increase in flood risk under a climate change scenario for both the with existing and with proposed defences scenarios. Site-specific flood risk assessments should take account of this information in appraising flood risk both now and in the future and in the design of developments that are safe, taking full account of the likely impacts of climate change. Initially, such assessments should be based upon the allowances given in Table 5.1.

Table 5.1 – Climate Change Allowances from PPS 25/Annex B

Parameter 1990 - 2025 2025 - 2050 2055 - 2085 2085 - 2115

Peak Rainfall Intensity +5% +10% +20% +30% Peak River Flow +10% +20%

5.2.4 Where the advice of the Greater Nottingham SFRA is superseded by PPS on Planning and

Climate Change or with scientific developments, this information should be used to compliment the SFRA.

5.3 Development behind Defences/Embankments 5.3.1 PPS 25 advises that, following application of the Sequential Test and Exception Test,

development should not normally be permitted where flood defences, properly maintained and in combination with agreed warning and evacuation procedures, would not provide an acceptable standard of safety taking into account climate change (Paragraph G2).

5.3.2 Road and railway embankments and other linear infrastructure may hold back water or

create enclosures to form flood storage areas in addition to their primary function. This may or may not be a deliberate design. It is important that this is recognised, and where use of such infrastructure is proposed for flood management purposes discussed with the infrastructure owners (PPS 25/Paragraph G3 and PPS 25 Practice Guide/Paragraph 7.16).




5.3.3 The Practice Guide explains that raised embankments may offer a degree of flood protection. However, such structures should only be relied upon to protect new development following a flood risk assessment, which should investigate:

• whether the embankment is made of suitable materials to prevent seepage of

water through it, and is physically strong enough to maintain the pressure of water on one side;

• whether there are any culverts through the embankment or other gaps or holes that would let floodwater through;

• the performance of the structure during any recorded historical flood event; • the long-term Asset Management Plan provided by the owner of the

embankment; and • whether by holding water back, a structure may fall under the regulation

requirements of the Reservoirs Act (1975). 5.3.4 However, both PPS 25 and its accompanying Practice Guide stress that risks will be

greatest close to flood defences and local planning authorities should seek opportunities to set back developments and site new development away from existing flood risk management infrastructure (PPS 25/Paragraph G2 and PPS 25 Practice Guide/Paragraph 7.12).

5.4 Functional Floodplain 5.4.1 The functional floodplain is an area that would naturally flood during an event up to and

including the 1 in 20 year. However, areas that are prevented from doing so by existing infrastructure or solid buildings will not normally be defined as functional floodplain (PPS 25 Practice Guide/Paragraph 4.81).

5.4.2 Table D1 of PPS 25 explains that only water compatible and essential infrastructure uses

are appropriate in the functional floodplain, subject to being designed and constructed to:

• remain operational and safe for users during times of flood; • result in no net loss of floodplain storage; • not impede water flows; and • not increase flood risk elsewhere.

5.4.3 Examples of water compatible uses are flood control infrastructure, water treatment works,

sewage treatment works, sand and gravel workings and amenity open space. Examples of essential infrastructure are electricity generating power stations, strategic utility infrastructure and mass evacuation routes (PPS 25/Table D2).

5.4.4 Those proposing development should utilise the flood dynamic plans produced for the SFRA to establish whether the land falls within the functional floodplain, as defined above.

5.5 Access and Egress

5.5.1 PPS 25 requires that safe access and escape is available to and from new developments in

flood risk areas (PPS 25/Paragraph 8). The PPS 25 Practice Guide explains that wherever possible, safe access routes should be provided which are located above design flood levels and where this is not possible, limited depths of flooding may be appropriate provided that the proposed access is designed with appropriate signage etc. to make it safe (PPS 25 Practice Guide/Chapter 4/Paragraph 4.55).




5.5.2 Therefore, site-specific flood risk assessments should have due regard to the depths and velocities of flood water as per Table 3.1 in Section 3 and to the hazard rating maps included in Volume 1 of the technical report.

5.5.3 In some exceptional cases, developments or redevelopments will be proposed where the

building remains safe, but safe access cannot be guaranteed during a flood. In these cases, the Practice Guide advises that the potential implications of this should be considered when assessing the acceptability of the proposals and PPS 25 advises that the emergency services should be consulted on LDD and planning applications where emergency evacuation requirements are an issue (PPS 25/H11 and Practice Guide/Chapter 4/Paragraph 4.58).

5.6 Surface Water Drainage in New and Redeveloped Sites 5.6.1 PPS 25 requires that, as a minimum standard, major development proposals within the

borough shall not exacerbate the existing flooding situation and that volumes and peak flow rates leaving a developed site should be no greater than the rates prior to the proposed development, unless specific off site arrangements are made (PPS 25, Paragraph F10). Factual and anecdotal information on existing flooding problems is given on Maps 1-OTH-01 to 03 (included in Volume 1 of the technical report).

5.6.2 Paragraph F6 of PPS 25 also advises that surface water arising from a developed site

should, as far as is practicable, be managed in a sustainable manner to mimic the surface water flows prior to the proposed development, while reducing the flood risk to the site itself and elsewhere, taking climate change into account.

5.6.3 Priority should be given to the use of Sustainable Drainage Systems (SUDS) and green

infrastructure in meeting the objectives of PPS 25 and should be considered as part of a site-specific flood risk assessment (PPS 25 Paragraphs 6, 8 and E3).




6. SITE-SPECIFIC FLOOD RISK ASSESSMENTS 6.1.1 The outputs of the SFRA are focused upon establishing the risk of flooding and improved

flood mapping and modelling for planning purposes. These outputs are compatible with the requirement of Erewash Borough Council to produce a SFRA to inform preparation of the LDD, identify broad principles to assist the development control process and to quantify perceived constraints to redevelopment of brownfield land.

6.1.2 The SFRA does not provide specific flood risk information for individual sites. Therefore,

those proposing development will need to utilise the flood dynamic maps, flood hazard information and general discussion in the SFRA as the starting point for considering flood risk to development proposals.

6.1.3 A site-specific flood risk assessment may need to involve river modelling where built

development and flood mitigation measures require testing. 6.1.4 However, it is envisaged that the number of site-specific flood risk assessments needing to

be supported by river modelling will be reduced because the SFRA provides greater flooding information than currently available and the LDF process will aim to steer larger-scale development away from those areas of highest flood risk.

6.1.5 Paragraph 3.78 of the PPS 25 Practice Guide recommends that the approach shown in

Figure 6.1 is taken to scoping the requirements of a site-specific flood risk assessment. 6.1.6 The Environment Agency encourages pre-application discussion and offers a pre-planning

enquiry service where advice can be given on development proposals. As a minimum, this service requires submission of a site location plan or other means of site identification such as postal address or grid reference. Where further information is available (e.g. development proposals, ground level data, statement of development principles etc.) this should be provided with the enquiry.




Figure 6.1 – Scoping of Site Specific Flood Risk Assessment

Development Description and Location

e.g. review LDD, flood risk vulnerability classification

Definition of Flood Hazard e.g. identify all flood sources and

existing surface water arrangements for the site

Probability e.g. information from the SFRA covering

the site

Climate Change e.g. effects of climate change on flood risk for the lifetime of the development

Detailed Development Proposalse.g. details of development layout

Flood Risk Management Measures

e.g. how will the site be protected from flooding

Off Site Impacts e.g. incorporate SUDS in overall design

or justify why they are not suitable

Residual Risk e.g. assessment of flood-related risks that

remain after measures to protect site




7 REPORT CONCLUSIONS Spatial Policy

7.1.1 The SFRA and its findings will form part of the evidence base for the LDF and the

following issues have emerged:

• flooding needs to be considered holistically and due consideration needs to be given to all sources of flooding (e.g. sewer flooding, groundwater flooding, surface water drainage issues etc.);

• priority should be given to using sustainable forms of drainage and reducing overall rates and volumes of run-off in accordance with the principles of PPS 25.

7.1.2 Therefore, the LDF process should further develop the following issues:

• opportunities should be taken to work with other authorities in the Greater Nottingham conurbation to share best practice and knowledge in terms of flooding and sustainable surface water management with the common goal of reducing overall flood risk;

• the need to engage key stakeholders (highways, sewerage undertakers and emergency planners) in the development of policies in LDD to plan and design for the type of flood and to ensure safe and sustainable communities;

• the need to work with developers to ensure that the design of buildings in the future take into account flood resilience and resistance and the ability of people to safely access and exit buildings;

• the need to engage all those involved in drainage issues to investigate the adoption of surface water management measures in the future and make sure that approaches to surface water management are effective and deliverable; and

• the need to work with emergency planners and utilise their liaison opportunities with the emergency services to guarantee the safety of buildings and people within them and ease of evacuation during flooding events.




8. GLOSSARY OF TERMS AND ABBREVIATIONS Brownfield Land Land which is or was occupied by a permanent

structure, including the curtilage of the developed land and any associated fixed surface infrastructure. Also referred to as developable previously-developed land.

Defra Department of Environment, Food and Rural Affairs.

Exception Test The Exception Test as set out by PPS 25 requires development to provide wider sustainability benefits that outweigh flood risk, be on developable previously-developed land and be supported by a satisfactory flood risk assessment.

Flood Dynamic Maps A map showing the direction, average spot depth and cause of flooding.

Flood Risk Assessment (FRA) A study to assess the risk to an area or site from flooding, now and in the future, and to assess the impact that any changes or development on the site or area will have on flood risk to the site and elsewhere.

Flood Zone Maps Map published by the Environment Agency on the internet showing flood risk separated into three zones as defined in PPS 25. It does not show other sources of flooding such as surface water, groundwater, sewers, canals and reservoirs which also need to be included in the flood risk assessment which is needed to support a planning application.

Functional Floodplain An area that would naturally flood during an event up to and including a 1 in 20 annual chance flood event. However, areas that are prevented from doing so by existing infrastructure or solid buildings will not normally be defined as functional floodplain, in accordance with Paragraph 3.15 of PPS 25 Practice Guide.

Greater Nottingham Strategic Flood Risk Assessment Partnership (GNSFRA)

A collaborative project to produce floodplain mapping of the River Trent and its key tributaries.

Left Bank The river bank on the left side when viewed by a person stood facing downstream.




LiDAR A technique for obtaining ground level data, stands for Light Detection And Ranging.

Local Development Documents (LDD) Planning documents which form part of the Local Development Framework.

Local Development Framework (LDF) A folder of Local Development Documents prepared by district councils, unitary authorities or national park authorities that outline the spatial planning strategy for the local area.

Other Sources of Flooding Maps A map showing anecdotal and factual information on known sources of flooding other than rivers and streams e.g. sewer flooding, drainage issues etc. included in Volume 1 of the technical report.

Planning Policy Statement A statement of policy issued by central Government to replace Planning Policy Guidance notes and sets out general development principles.

Planning Policy Statement 25: Development and Flood Risk (PPS 25)

Sets out Government policy on development and flood risk. Its aims 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 of 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.

Planning Policy Statement: Planning and Climate Change - Supplement to Planning Policy Statement 1

Sets out how planning, in providing for the new homes, jobs and infrastructure needed by communities, should help shape places with lower carbon emissions and resilient to the climate change now accepted as inevitable.

Right Bank The river bank on the right side when viewed by a person stood facing downstream.

Sequential Test The flood risk sequential test as set out in PPS 25 requires development to first take place in areas of lowest flood risk.

Strategic Flood Risk Assessment (SFRA) A high-level document that strategically appraises all sources of flood risk impacting upon a study area and provides a planning tool to inform the planning process.




Sustainability Appraisal A statutory document under the Planning and Compulsory Purchase Act 2004 which requires LDD to be tested against sustainability criteria.

Sustainable Drainage Systems (SUDS) A collection of management practices and control structures designed to drain water in a more sustainable manner than some conventional techniques and replicate natural patterns of drainage.

.




9. FURTHER INFORMATION ‘Learning lessons from the 2007 floods’ by Sir Michael Pitt June 2008

The final report of the independent review into the lessons learned from the Summer 2007 floods, which contains 92 wide-ranging recommendations. The recommendations on building and planning reinforce the role of PPS 25 and presumption against building in high flood risk areas. Web Site: http://www.cabinetoffice.gov.uk/thepittreview.aspx

Future Water – The Government’s water strategy for England February 2008

The consultation document sets out the Government’s plans for water in the future, looking at the water cycle as a whole and every aspect of water use. Future Water builds upon the floods plan ‘Making Space for Water’ and sets out a new approach to managing surface water to promote sustainable drainage above ground. Web Site: http://www.defra.gov.uk/Environment/water/strategy/index.htm

Making Space for Water Consultation July 2004 First Government response March 2005

Making Space for Water is the Government’s strategy for flood and coastal erosion risk management for the next 20 years. The aim of the strategy is to reduce threat to people and their property; and to deliver greatest environmental, social and economic benefit consistent with sustainable development principles. Web Site: www.defra.gov.uk/environ/fcd/policy/strategy.htm

Planning Policy Statement 25: Development and Flood Risk (PPS 25)

This planning document sets out the Government’s national policies on different aspects of land use planning with the aim of ensuring flood risk is taken into account at all stages of the planning process and to avoid inappropriate development in areas at risk of flooding. Supported by a Practice Guide to provide information on implementation of the policies set out in PPS 25. Web Site: http://www.communities.gov.uk/pub/955/PlanningPolicyStatement25DevelopmentandFloodRisk_id1504955.pdf




River Trent Fluvial Strategy, March 2005

A high level document which assessed the risk of flooding from the fluvial stretch of the River Trent from Stoke on Trent to the tidal limits at Cromwell Lock, downstream of Newark on Trent and appraised options to mitigate against the flooding situation and recommended future flood alleviation works.

Corporate Plan This document sets out the vision and priorities for the borough from 2005 until 2008, including a better environment for all.

Community Strategy The Community Strategy sets out how the visions and priorities of the Corporate Plan will be delivered.




MAPS Map 6-NTS-01 Erewash Borough Council Location Plan Map 6-GEN-01 Watercourses covered in this volume Map 6-GEN-02 Draycott – Existing Knowledge Map 6-GEN-03 Ock Brook – Existing Knowledge Map 6-GEN-04 Church Wilne – Existing Knowledge Map 6-GEN-05 Nut Brook – Existing Knowledge Map 6-GEN-06 Golden Brook – Existing Knowledge Map 6-EBC-01 Flood Dynamic Plan of the River Trent (Existing Defences)

Erewash Borough Council (1 of 3) Map 6-EBC-02 Flood Dynamic Plan of the River Trent (Existing Defences)

Erewash Borough Council (2 of 3) Map 6-EBC-03 Flood Dynamic Plan of the River Trent (Existing Defences)

Erewash Borough Council (3 of 3) Map 6-EBC-04 Flood Dynamic Plan of the River Trent (Proposed Defences)



Erewash Borough Council (3 of 3) Map 2-FDP-01 Flood Dynamic Plan of the River Erewash (1 of 10) Map 2-FDP-02 Flood Dynamic Plan of the River Erewash (2 of 10) Map 2-FDP-03 Flood Dynamic Plan of the River Erewash (3 of 10) Map 2-FDP-04 Flood Dynamic Plan of the River Erewash (4 of 10) Map 2-FDP-05 Flood Dynamic Plan of the River Erewash (5 of 10) Map 2-FDP-06 Flood Dynamic Plan of the River Erewash (6 of 10) Map 2-FDP-07 Flood Dynamic Plan of the River Erewash (7 of 10) Map 2-FDP-08 Flood Dynamic Plan of the River Erewash (8 of 10) Map 2-FDP-09 Flood Dynamic Plan of the River Erewash (9 of 10) Map 2-FDP-10 Flood Dynamic Plan of the River Erewash (10 of 10)

Greater Nottingham Strategic Flood Risk Assessment … · Strategic Flood Risk Assessment...

Documents

Transcript of Greater Nottingham Strategic Flood Risk Assessment … · Strategic Flood Risk Assessment...