Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Great Ouse

Catchment Flood Management Plan Consultation Draft Plan (January 2007)

Environment Agency i Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

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Environment Agency Kingfisher House Goldhay Way Orton Goldhay Peterborough PE2 5ZR Tel: 08708 506 506

Environment Agency ii Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Please send any comments about this consultation document by 30th March 2007 to:

Lucy Harper Regional Strategic and Development Planning Environment Agency Kingfisher House Goldhay Way Orton Goldhay Peterborough PE2 5ZR

E-mail address: [email protected]

Environment Agency Office Anglian Region, Central Area

Environment Agency Project Executive Roy Lobley

Environment Agency Project Manager Lucy Harper

Consultant Royal Haskoning

Consultant Project Manager Matthew Hardwick

Document History:

Draft final draft CFMP v1.0 6th October 2006 Issued to Environment Agency for review by Project Team and Steering Group Draft final draft CFMP v2.0 8th January 2007 Issued to Environment Agency for review by Consultation Group

Environment Agency iii Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Foreword

Many areas of England and Wales have suffered serious flooding in recent years. In consequence the issue of flooding is very much to the fore, and of concern, to those living in flood risk areas. Future climate change is expected to increase the risk of flooding and continuing development pressures to cope with an ever-growing population must be accommodated and managed against this background.

Flood risk management is complex with many links to other policy areas at both national and local level. Government strategy is for an all-embracing approach setting the management of flood risk within the broader concept of a catchment as a whole and Catchment Flood Management Plans (CFMPs) are a key component of this.

CFMPs will look to the future over 50 – 100 years taking a broad view at the catchment scale considering the many factors such as climate change, development, land use change and land management to develop and agree sustainable policies for the future management of flood risk. Key to this will be the engagement of the many organisations involved.

The Plan will not just focus on traditional engineered methods of flood management but will explore all potential solutions working with nature wherever possible to produce sustainable solutions for the benefit of all.

Environment Agency iv Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Contents Contents ...... v List of tables...... vii List of figures...... ix Executive summary...... 1 1 Introduction ...... 4 1.1 Background 4 1.2 Great Ouse CFMP: Aims and scope 5 1.4 Involving others 10 1.5 Monitoring, review and evaluation of the CFMP 11

2 Catchment overview ...... 13 2.1 Definition and extent of the Great Ouse Catchment 13 2.2 Topography 18 2.3 Geology and hydrogeology 18 2.4 Geomorphology 23 2.5 Soils 24 2.6 Land use and land management 27 2.7 Hydrology 32 2.8 Environment and heritage 44 2.9 Communities and the local economy 60

3 Current flood risks and management ...... 64 3.1 History of flooding 64 3.2 Sources and probability of flooding 65 3.3 Consequences of flooding 83 3.4 Summary of flood risk 111 3.5 Existing flood risk management 113

4 Future changes ...... 121 4.1 Introduction 121 4.2 Future scenarios 121 4.3 Assessment of future flood risk 127 4.4 Flood risk at key locations 135

5 Catchment objectives ...... 136 5.1 Introduction 136 5.2 Catchment opportunities and constraints 136 5.3 CFMP objectives 142

6 Policy appraisal...... 146 6.1 Introduction 146 6.2 Policies for the Great Ouse catchment 147

7 Delivering the CFMP ...... 161

Environment Agency v Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 7.1 Action plan 161 7.2 Inter-relationships between selected policies and actions 175

List of abbreviations ...... 177 Glossary of terms ...... 180 References ...... 194

Appendix A – Responsibilities for flood Risk Management and Associated Activities

Appendix B - Environmental Report

Appendix C – Communication plan

Appendix D – Environmental features

Appendix E – Landscape character

Appendix F – Main sites identified for current and future wetland creation

Appendix G – Flood Risk

Appendix H – Policies relevant to the Great Ouse CFMP

Appendix I – Current flood defence improvements

Appendix J – Results of the sensitivity tests

Appendix K – Results of the scenario tests

Appendix L – Strategic flood storage assessment

Appendix M – Policy appraisal

Environment Agency vi Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 List of tables

Table 1.1 Programme for development of the Great Ouse CFMP 12 Table 2.1 Sub-catchment overview 14 Table 2.2 Overall distribution of land use on the catchment 27 Table 2.3 Comparison of urban development in the UK 28 Table 2.4 Relative importance of tributaries to Bedford Ouse 35 Table 2.5 Flood peak travel on Bedford Ouse 35 Table 2.6 Relative importance of sub-catchments 39 Table 2.7 Time of travel of flood peak for given rivers 39 Table 2.8 BAP habitats in the Great Ouse catchment 46 Table 2.9 Summary of Joint Character Areas 48 Table 2.10 Chemical and biological General Quality Assessment grades (2004) for the Great Ouse catchment 55 Table 2.11 Population distribution within the catchment 60 Table 2.12: Community statistics 61 Table 3.1 Tide levels 79 Table 3.2 Assessment of risk to people 87 Table 3.3 Average Annual Damages (AAD) for high impact areas 101 Table 3.4 Isolated settlements during a 1 in 100 year (1% AEP) flood event 103 Table 3.5 Summary table of existing flood risk to property for the high impact areas 104 Table 3.6 Analysis of fenland areas within Flood Zone 3 106 Table 3.7 Infrastructure potentially at risk 107 Table 3.8 Environmental assets at risk of flooding 109 Table 3.9 Summary of flood risk 111 Table 3.10 Main River defences 114 Table 4.1 Historical trends in population numbers across the Great Ouse catchment 122 Table 4.2 Historical trends in household numbers across the Great Ouse catchment 122 Table 4.3 Housing targets for the Great Ouse catchment 123 Table 4.4 Predicted sea level changes 125 Table 4.5 Future scenarios 127 Table 4.6 Future flood risk issues 128 Table 4.7 Impact of future scenarios on economic flood risk (% AAD increase per sub catchment) 130 Table 4.8 Impact of climate change on flood risk to people and property 130 Table 5.1 Strategic storage assessment for selected rivers 138 Table 5.2 Extra volumes due to climate change requiring storage 139 Table 5.3 Strategic storage assessment for the Fens 139 Table 5.4 Opportunities and Constraints 140 Table 5.5 Objectives for the Great Ouse CFMP 143

Environment Agency vii Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 6.1 Six policy options 146 Table 6.3 Eastern Rivers summary table 151 Table 6.4 Southern Rivers summary table 153 Table 6.5 Bedford Ouse summary table 156 Table 6.6 The Fens summary table 159 Table 7.1 Prioritised action 161

Environment Agency viii Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 List of figures Figure S1 Policy units and proposed policies...... 3 Figure 1.1 The Great Ouse CFMP area and adjacent CFMPs...... 6 Figure 1.2 The CFMP process ...... 7 Figure 1.3 Links between flood risk management plans and the wider planning framework.....9 Figure 2.1 Main features ...... 15 Figure 2.2 Administrative councils and districts ...... 16 Figure 2.3 Hydrology and IDB areas...... 17 Figure 2.4 Topography...... 19 Figure 2.5 Great Ouse bed levels...... 20 Figure 2.6 Solid geology...... 21 Figure 2.7 Drift geology ...... 22 Figure 2.8 - Comparison of river flows and bed levels in the Tidal River since 1998 ...... 24 Figure 2.9 Soil type...... 25 Figure 2.10 Soils - Winter Rainfall Acceptance Potential (WRAP) ...... 26 Figure 2.11 Land Use ...... 29 Figure 2.12 Agricultural Land Classification ...... 30 Figure 2.13 Prospective urban development in the Great Ouse catchment ...... 31 Figure 2.14 Annual rainfall distribution...... 33 Figure 2.15 Flow hydrographs at key location ...... 34 Figure 2.16 - Relative Influence of flows in the Great Ouse and the Ouzel ...... 36 Figure 2.17 - Relative contribution and timing of the Great Ouse, River Ivel, River Kym, and Alconbury Brook ...... 37 Figure 2.18 - Flood response on the River Ivel and River Flit...... 38 Figure 2.19 - Relative influence and timing of flows to Byrons Pool and Cambridge...... 40 Figure 2.20 - Timing of flows on the River Lark and Kennet...... 41 Figure 2.21 - Flood response on the Little Ouse and tributaries to Thetford...... 42 Figure 2.22 - Flood response on the River Wissey ...... 43 Figure 2.23 Designated nature conservation sites of national, European and international interest...... 49 Figure 2.24 Designated nature conservation sites of international importance...... 50 Figure 2.25 UK BAP habitats...... 51 Figure 2.26 Navigation ...... 54 Figure 2.27 Chemical water quality (GQA, 2004)...... 57 Figure 2.28 Biological water quality (GQA, 2004)...... 58 Figure 2.29 River Water Quality Objectives ...... 59 Figure 2.30 Scheduled Ancient Monument sites...... 63 Figure 3.1 Flood Map for the Great Ouse catchment...... 67 Figure 3.2 Flood Zone mapping for Bury St Edmunds and Thetford...... 68

Environment Agency ix Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.3 Flood Zone mapping for Bedford and Alconbury/Alconbury Weston ...... 69 Figure 3.4 Flood Zone mapping for Towcester, Biggleswade, Beeston, Sandy and Blunham .70 Figure 3.5 Flood Zone mapping for Newport Pagnell and Hemingford Grey, Needingworth and St Ives ...... 71 Figure 3.6 Flood Zone mapping for Huntingdon and Godmanchester, and Swavesey ...... 72 Figure 3.7 Flood Zone mapping for St Neots and Eaton Socon, and Offord Darcy and Offord Cluny...... 73 Figure 3.8 Flood Zone mapping for Henlow and Clophill...... 74 Figure 3.9 Flood Zone mapping for Fenny Stratford and Letchworth ...... 75 Figure 3.10 Flood Zone mapping for Olney and Stotfold ...... 76 Figure 3.11 Flood Zone mapping for King’s Lynn and Great Chesterford ...... 77 Figure 3.12 Flood Zone mapping for Sawston and Mildenhall ...... 78 Figure 3.13 Tidal areas...... 82 Figure 3.14 Social Flooding Vulnerability Index and number of properties at risk from a 1 in 100 year (1% AEP) flood event for high impact areas ...... 86 Figure 3.15 Flood depths for Bury St Edmunds and Thetford...... 90 Figure 3.16 Flood depths for Bedford and Alconbury/Alconbury Weston...... 91 Figure 3.17 Flood depths for Towcester, and Biggleswade, Beeston, Sandy and Blunham ....92 Figure 3.18 Flood depths for Newport Pagnell and Hemingford Grey, Needingworth and St. Ives ...... 93 Figure 3.19 Flood depths for Huntingdon and Godmanchester, and Swavesey...... 94 Figure 3.20 Flood depths for St Neots and Eaton Socon, and Offord Darcy and Offord Cluny 95 Figure 3.21 Flood depths for Henlow and Clophill...... 96 Figure 3.22 Flood depths for Fenny Stratford and Letchworth ...... 97 Figure 3.23 Flood depths for Olney and Stotfold...... 98 Figure 3.24 Flood depths for Great Chesterford and Sawston...... 99 Figure 3.25 Flood depths for Mildenhall ...... 100 Figure 3.26 AAD damages in high risk areas ...... 105 Figure 3.27 Flood defences ...... 118 Figure 3.28 Flood warning areas...... 119 Figure 3.29 Location of level/flow gauges ...... 120 Figure 4.1 Historical trends in household numbers across the Great Ouse catchment...... 122 Figure 4.2 Chart comparing AADs across the catchment...... 133 Figure 5.1 Strategic flood storage areas...... 137 Figure 6.1 Policy units and proposed policies...... 148

Environment Agency x Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Executive summary

Introduction A Catchment Flood Management Plan (CFMP) is a policy document for catchment-wide flood risk management. CFMPs look 50 to 100 years ahead; their policies set the framework for future flood risk management decisions. It is important for us to produce this CFMP in partnership with other organisations and people who have an interest in the CFMP area. Working in partnership will encourage co-operation between different agencies and5 enable all parties to make informed decisions about how best we can manage flood risk at a catchment scale. In this Consultation Draft Plan, we present our findings from the Draft Main Stage. In the Draft Main Stage we have developed an assessment of future flood risk, identified opportunities and constraints for managing future flood risk, and developed draft flood risk management policies for the catchment.

Catchment Overview The Great Ouse CFMP covers a total area of 8,587Km2. The River Great Ouse is the primary river system. It starts in Northamptonshire near Brackley and passes through several towns before crossing the Fens and flowing into The Wash downstream of King’s Lynn. Other significant rivers in the catchment include the Tove (Towcester), Ouzel (east of Milton Keynes), Cam (Cambridge), Ivel (Biggleswade), Lark (Bury St Edmunds / Mildenhall), Little Ouse (Thetford) and Wissey (south of Downham Market). Great Ouse at St Ives Current Flood Risk Issues We have found that flooding has a significant impact on people in close proximity to all major rivers, drains and brooks. Floods have consequences to people, properties and the environment. For the existing situation, we estimate that approximately 158,000 people and 39,000 properties are at risk of flooding from a 1 in 100 year (1% AEP) flood event. We estimate associated damages of £41.5m to property and £5.2m to agriculture across the catchment.

In an extreme flood many major roads would be flooded including the A1, A11, A14, A43, and A6. This would limit evacuation routes and isolate a number of settlements. An extreme flood would also cause the electricity supply, telecommunications, water supplies and waste water treatment to be at risk. Infrastructure is particularly at risk of flooding in the Bedford Ouse sub-catchment.

Flooding can have both a negative and a positive effect on the environment. Our analysis suggests that within the Great Ouse catchment, flooding could impact 94 Sites of Special Scientific Interest (SSSIs), 109 Scheduled Ancient Monuments (SAMS) and various other designated sites. Flooding across the catchment would also have an impact on fisheries, water resources, landscape and tourism.

Future Flood Risk Through future changes in urban development, land use management and climate change, it is likely that flood risk in the Great Ouse catchment will increase. We have identified climate change as the most important factor affecting future flood risk. We have shown that climate change, compared with existing conditions, increases the impact of flooding by 85 per cent for a 1 in 100 year (1% AEP) flood event. Urban development and land use/management, in particular intensification of agriculture, are also likely to be important factors for future flood risk in some areas of the Great Ouse catchment. The implementation of measures such as source control in urban areas could potentially compensate for some of the increase in flood risk due to climate change.

Opportunities and Constraints The Great Ouse catchment provides many opportunities for sustainable flood risk management practices that can also deliver benefits for other functions, such as habitats, heritage, landscape and recreation. For example, we believe that a key opportunity for catchment wide sustainable flood risk management is to reduce flood risk in the Fens by storing water in the upper areas of the catchment.

Environment Agency 1 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 These opportunities and constraints have fed into the set of objectives for the Great Ouse Catchment that we have used to appraise the policy options for the catchment.

In all of our CFMPs we work with the following 6 policies for the management of flood risk:

Policy Policy Option 1 Withdraw current flood risk actions; 2 Reduce current flood risk actions and accept that flood risk will increase with time; 3 Continue with current flood risk actions but accept future increases in flooding due to climate change; 4 Continue with current flood risk actions and respond to future change (for example urban development and climate change); 5 Take further action to reduce flood risk; 6 Take action to increase flooding in some areas to reduce flood risk in others.

In this Draft Main Stage we have selected draft flood risk management policies by analysing the impact of each policy on flood risk to people, property and the environment, both for the current and the future situation. We have based this policy appraisal on the objectives for the catchment as defined in cooperation with our Steering Group, taking into account the guidance for a Strategic Environmental Assessment. The proposed policies are shown in Figure S1.

To achieve the proposed policies we have prepared an action plan; high priority actions have been determined for each of the policy units shown in Figure S1. An important action is a catchment wide hydrological study for the Great Ouse and its tributaries, aiming to provide information on catchment interactions; this increased understanding is required to carry out more detailed flood risk management studies for specific locations identified. A monitoring group will regularly review and monitor the CFMP, ensuring that it is implemented as proposed and achieves the policy and actions of the CFMP.

Environment Agency 2 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure S1 Policy units and proposed policies

Environment Agency 3 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 1 Introduction

Flooding occurs naturally and puts people, property and the environment at risk. We expect flood risk to increase in the future in response to changes in climate, land use and land management practice. We cannot prevent all flooding, so the best way we can deal with flood risk is to take a long-term approach that works with nature. We want to manage flooding in a sustainable way that is both fair and affordable.

Bedford Ouse, Welches Dam

1.1 Background

Flood risk management

Flood risk management is the way in which we aim to understand and manage the causes and consequences of flooding in a sustainable way. In many locations, constructing and maintaining defences will not be economically or environmentally justifiable in the long-term. We need to manage flood risk in other ways. For example, we use flood forecasting and flood warning to inform people of flooding, we maintain maps of flood risk areas, and try to inform and influence the planning process.

Flood risk management will adopt a strategic approach where we will target and prioritise our investment and resources to those areas where flood risk can most effectively be reduced. This approach requires partnership with organisations and individuals who have an interest across the catchment. As part of our Strategy for Flood Risk Management we also have to look at the catchment as a whole and take account of how actions in one part of the catchment can affect flood risk in another part. We are introducing Catchment Flood Management Plans (CFMPs) to ensure that all interested people and organisations develop and agree strategic flood risk management policies.

It must be recognised that we cannot reduce flood risk to every individual person or property across England and Wales. We need to target our efforts to those people in greatest need. Our policies are about setting the right strategic approach so that we take the best and most sustainable actions. We therefore need to understand the extent, nature and scale of current and future flood risk across the whole catchment before choosing certain policies. We need to decide at this stage where to take further action to reduce or sustain flood risk, where we need to change the way we currently manage flood risk, or where we need to take little or no action.

Planning for the future

A CFMP is a high level strategic planning tool through which we will seek to work with other key decision-makers to identify and agree long-term policies for sustainable flood risk management.

CFMPs assess flood risk so that we can identify the causes, magnitude and location of flood risk throughout the catchment. Potential future changes affecting flood risk are also assessed as part of the CFMP process, such as, development and land use change, climate change, and changes to rural land management.

The Great Ouse CFMP identifies broad policies for sustainable flood risk management that make sense in the context of the whole catchment over the next 50 to 100 years. It will not determine specific flood risk reduction measures or management approaches for flooding issues in the catchment. Whilst it is not possible to understand in detail what will occur in 50 to 100 years time,

Environment Agency 4 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 general trends can be projected to test the sustainability of the CFMPs policies. The CFMP will be reviewed in five to six years to reflect changes in the catchment.

A CFMP will lead to the preparation of strategies from which the implementation of flood control measures could follow. Flood control measures are more likely to receive funding if backed by a CFMP.

A CFMP incorporates a Strategic Environmental Assessment (SEA), which is an environmental assessment used for plans and programmes. Appendix B shows where the SEA requirements are discussed in this document.

1.2 Great Ouse CFMP: Aims and scope

The location of the Great Ouse CFMP along with adjacent CFMPs is shown in Figure 1.1. The CFMP will look at broad scale issues so that we can set catchment wide policies that will guide future flood risk management decisions.

The Great Ouse CFMP aims to:

• reduce the risk of flooding and harm to people, property and the natural, historic and built environment caused by floods; • maximise opportunities to work with natural processes and to deliver multiple benefits from flood risk management, and make an effective contribution to sustainable development; • support the implementation of EU Directives, the delivery of Government and other stakeholder policies and targets, and our Environmental Vision; • promote sustainable flood risk management; • inform and support planning policies, statutory land use plans and implementation of the EU Water Framework Directive; and • assist and inform future local plans.

The main objective of a CFMP is to develop policies to guide the management of flood risk within the catchment now and in the future. Policies that take into account the likely impacts of changes in climate, the effects of land use and land management, bring real benefits and contribute towards sustainable development.

Environment Agency 5 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 1.1 The Great Ouse CFMP area and adjacent CFMPs

Environment Agency 6 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

The Draft CFMP Stage builds on our understanding of flood risk that we developed during the Scoping Stage, and leads to the Final Plan (see Figure 1.2).

Figure 1.2 The CFMP process

Environment Agency 7 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 The main functions of this report are to:

• undertake a high-level strategic assessment of current and future flood risk from all relevant sources (i.e. rivers, sewers, groundwater, etc) within the catchment, by understanding the components that constitute the risk (i.e. both probability and impact) and the effect of current risk reduction measures. The scale of risk should be broadly quantified in economic, social and environmental terms;

• finalise future scenarios used for assessing future flood risk in response to feedback from consultation on the Scoping Report;

• identify opportunities and constraints within the catchment for reducing flood risk through strategic changes or responses, such as changes in land use, land management practices and/or the flood defence infrastructure;

• identify the major opportunities for flood risk management to maintain, restore or enhance the total stock of natural and historic assets;

• review and finalise the specific objectives identified in the Scoping Report, following consultation;

• identify long term policy options for specific locations or areas (known as policy units); Policy units are determined through analysis of the catchment vision, flood risk assessment and issues;

• appraise and where possible, quantify the impacts of alternative policies against the specific CFMP objectives and future scenarios;

• select the preferred policies for each policy unit; and

• identify and prioritise strategic studies, actions or projects that will manage flood risk within the catchment, and assign responsibility to ourselves, other operating authorities, local authorities, water companies or other key stakeholders.

1.3 Links with other plans

CFMPs aim to manage flood risk in an integrated and sustainable way. This CFMP has been influenced by Government policies, national plans and strategies. These include:

• EU Water Framework Directive (WFD) (2000); • “Making Space for Water” (Defra, 2004); • “Future Flooding” – The Foresight report from the Office of Science and Technology (April 2004); and • “The Climate is Changing: Time to get Ready” (Environment Agency, March 2005).

The Water Framework Directive (WFD) is one of the most influential pieces of European legislation to date, designed to integrate the way we manage water bodies across Europe and requiring all inland and coastal waters to reach "good status" by 2015. The WFD aims to protect and enhance our water environment, promote sustainable water consumption, reduce water pollution and lessen the effects of floods and droughts. The WFD updates all existing European legislation and promotes a new approach to water management through river basin planning.

In addition, we have reviewed the following local and regional plans and strategies:

• East of England Plan, Draft Revision to the Regional Spatial Strategy 14 (East of England) (December 2004); • Regional Planning Guidance for East Anglia to 2016 (RPG 6) (November 2000); • Draft Revised Regional Planning Guidance for the South East to 2016 (RPG 9) (December 2000); • Cambridgeshire and Peterborough Structure Plan (2003);

Environment Agency 8 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 • Bedfordshire and Luton Structure Plan 2016 Deposit Draft (November 2002); • Buckinghamshire County Structure Plan 1991-2011 Deposit Draft (March, 1996); • Northamptonshire County Structure Plan 1996-2016 (undated); • Norfolk Structure Plan (1999); • Suffolk Structure Plan (2001); • The Wash Shoreline Management Plan (December, 1996); • The Wash – Which Way Now? A Draft Management Plan for the Wash Estuary System (February 2004); • The North West Norfolk Catchment Abstraction Management Strategy (CAMS) (March 2005); • The Upper Ouse and Bedford Ouse Catchment Abstraction Management Strategy (CAMS) (March 2005); • The East of England Regional Habitat Biodiversity Targets (2004); • Bedfordshire and Luton Local Biodiversity Action Plan (undated); • Cambridgeshire Local Biodiversity Action Plan (undated); • Buckinghamshire and Milton Keynes Local Biodiversity Action Plan (2000-2010); • Suffolk Local Biodiversity Action Plan (2000); and • Norfolk Local Biodiversity Action Plan (undated).

Further details of regional strategies and policies can be found in Appendix H.

CFMPs sit within the wider statutory and non-statutory planning framework in England and Wales (illustrated in Figure 1.3).

Figure 1.3 Links between flood risk management plans and the wider planning framework

SFRAs

Environment Agency 9 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 As shown in Figure 1.3 the CFMP has an important link with the land use planning process. This relationship operates at two levels: 1) a strong link to the Regional Spatial Strategy (RSS) and 2) a link to the local development frameworks. The CFMP also has an important link with rural land management plans.

The Great Ouse CFMP is being developed with strong links to the River Nene CFMP. Flood risk in the Fens is increased due to links between the River Great Ouse, the River Nene and the Middle Level Commissioners’ drainage systems. The potential for failure of a flood embankment somewhere in the Fens presents additional risk.

In addition, flood management for The Wash has already been considered in The Wash Shoreline Management Plan (SMP), due for revision in 2006. The Great Ouse CFMP will sit alongside this SMP and will therefore focus on non-coastal flooding. However, the CFMP will still address the impact of the tide on rivers.

With regard to implications of the Habitats Directive on the Great Ouse CFMP, any actions that are likely to interact with any European site such as Sites of Community Importance (SCIs), Special Areas of Conservation (SACs) and Special Protection Areas (SPAs), will require an assessment to ensure there are no adverse effects on the site. The assessment should determine, on the basis of objective information, if any proposed actions will have a significant effect on the European site (either alone or in combination with other plans and projects). Following this assessment, and the advice of the relevant nature conservation body, the plan or project may be authorised if the competent authority is certain that it will not adversely affect the site.

CFMPs are essential to allow us to approach flood risk management in a strategic and active way. In developing CFMPs and SMPs, we can plan to reduce flood risk whilst making the most of opportunities to deliver multiple benefits. These will include the environmental objectives set out in River Basin Management Plans under the Water Framework Directive.

The European Commission (EC) has recently proposed a new directive on the assessment and management of flood risks (the Floods Directive). This aims to reduce the risk to human health, the environment and economic activity associated with flooding. We will have to prepare Flood Risk Management Plans (FRMPs) under the Floods Directive, and these will sit alongside the River Basin Management Plans. The FRMPs we prepare in the future will build on our CFMPs and SMPs.

1.4 Involving others

There are many organisations, groups and individuals with an interest in how flood risk is managed, including local authorities, Internal Drainage Boards, water companies, conservation bodies and the public. Their involvement is vital to the success of the CFMP both in formulating and implementing policies. We will work together with these organisations and decision makers in order to encourage co-operation between different agencies and to enable all parties to make informed decisions about how best to manage flood risk in the Great Ouse catchment. We anticipate this plan will be used by:

• Our organisation (The Environment Agency) to guide internal investment in flood risk management activities (e.g. flood risk mapping, data management, asset management and flood incident management) and support other activities within the catchment (e.g. river basin management planning under the Water Framework Directive);

• The regional and local government authorities to inform spatial planning activities, sustainability appraisal/Strategic Environmental Assessment and emergency planning;

• Internal Drainage Boards and water companies to inform the planning of their activities in the wider context of the catchment;

• Government and devolved government departments for use in planning future funding and policy development; and

• The public to enhance its understanding of flood risk and integrated flood risk management.

Environment Agency 10 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Our lines of communication for the Great Ouse CFMP are set out in the Communication Plan, which can be found in Appendix C. The Communication Plan is a live document and will be updated when there are revisions to the programme and personnel. The Communication Plan identifies each organisation and representative of the Board, Project Team and Steering Group, as well as other consultees who form the Consultation Group. Core Project Team members include the Project Executive, Environment Agency Project Manager, Environment Agency Project Assistant, and the consultant’s Project Director and Project Manager. Other Environment Agency Staff act as additional members of the Project Team and provide specialist advice throughout the CFMP process. The Project Team oversee the development of the CFMP and provide an understanding of flood risk management issues across the catchment. The Project Team is an essential point of reference for data collection.

The purpose of the Steering Group is to guide the technical delivery of the CFMP, to focus data collection, and to provide information regarding flood risk management from a wide range of organisations. Individual members of the Steering Group have been chosen for their knowledge of the catchment and their ability to influence policy within their own organisation. The organisations that are represented on the Steering Group are:

• Environment Agency; • Internal Drainage Boards; • Royal Society for the Protection of Birds (RSPB); • Natural England; • National Farmers Union (NFU); • East of England Regional Assembly; and • Regional Flood Defence Committee (RFDC).

The reports produced at various stages in the development of the CFMP are circulated to a wider Consultation Group to ensure the views of other organisations are taken into account.

1.5 Monitoring, review and evaluation of the CFMP

We will be working with partners on the steering and consultation groups to implement the CFMP, and we will regularly review and monitor the CFMP so that we:

• Manage the implementation of the CFMP; • Ensure that the CFMP is being implemented as proposed; and • Ensure that we are achieving the policy and actions of the CFMP.

We will monitor the performance of the CFMP by readily quantifiable indicators or outcomes. We will report the performance against these annually.

Following the publication of the CFMP, we will appoint an Implementation Manager who will be accountable for:

• Establishing implementation group(s) for the CFMP; • Monitoring delivery of the CFMP; and • Reporting on delivery of the CFMP.

Implementation groups will influence the delivery of actions contained in the CFMP. The composition of the implementation group is likely to mirror the membership of the steering groups and project teams, and will include representatives from the lead organisations identified in the action plan.

The implementation group will be able to request the review of a CFMP, or part of it, before the due date.

Environment Agency 11 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 The current timetable for the Great Ouse CFMP process is provided in Table 1.1 below, including all project stages and consultation periods. We are currently at the consultation stage of the Draft CFMP.

Table 1.1 Programme for development of the Great Ouse CFMP

CFMP Stage Details Timing Project start-up • Start-up meeting and formation of October 2004 the project team Inception • Formation of the Steering Group October 2004 to January 2005 • Initial data gathering • Develop initial catchment understanding Consultation • Initial consultation with the Steering January 2005 Group Scoping • Collate additional information January 2005 to November 2005 • Understand current flood risk management issues and their management • Scope future scenarios • Identify catchment objectives and opportunities and constraints • Produce the scoping report Consultation • Consult with Steering Group November 2005 to January 2006 Draft CFMP • Consider consultation responses January 2006 to January 2007 • Finalise future scenarios and assess their impacts • Develop opportunities and constraints • Identify policy options and policy units – select preferred options following appraisal • Consult with steering group Consultation • Consult with interested parties January 2007 Final CFMP • Review consultation responses April 2007 • Produce final CFMP • Post adoption statement Monitor and review Ongoing

Environment Agency 12 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2 Catchment overview

This section of the Consultation Draft Plan describes the characteristics of the Great Ouse catchment. We have used environmental information (for example, topography, geology, soils, geomorphology, hydrology, landscape, heritage, habitats, species, and land use) to highlight the catchment features that may contribute to flood risk, that could be affected by flooding, or that provide opportunities and constraints for flood risk management.

2.1 Definition and extent of the Great Ouse Catchment

The Great Ouse CFMP covers an area of 8,587km2 which is drained by the River Great Ouse and its tributaries. The CFMP area extends from Northamptonshire in the west to Norfolk and Suffolk in the East. The southern boundary of the CFMP is defined by the catchment boundaries of the River Twins, Clipstone Brook, River Hiz, River Cam, River Granta, River Kennett, River Lark and Little Ouse River. The Wash forms the Northern boundary of the CFMP.

Bedford Ouse 1998at Welches Dam The main features of the Great Ouse catchment are shown in Figure 2.1. The catchment is predominantly rural and the major land use is agricultural. Significant urban areas include Milton Keynes, Cambridge, Bedford and King’s Lynn, with many smaller market towns such as Buckingham, St Neots, St Ives, Ely and Thetford. The M11, M1, and A1(M) motorways, numerous A roads, rail links to the capital, and King’s Lynn Docks are important parts of the transport infrastructure in the catchment. Nine County Councils fall wholly or partly within the catchment area and, in addition, there are twenty five District/Borough Councils and one Unitary Authority. These administrative areas are shown on Figure 2.2.

The majority of the watercouses within the Great Ouse catchment are man-made and heavily modified, either for flood defence, navigation, or land drainage purposes. Modifications include completely artificial cut-off channels, channel realignment and re-sectioning, bank reinforcement, weirs / locks and loss of floodplain channel diversity. The River Great Ouse is the primary river system, which starts in Northamptonshire near Brackley (see Figure 2.1). It then passes through Buckingham, Newport Pagnell, Bedford, St Neots, St Ives, and Earith, then crosses the Fens before flowing into The Wash downstream of King’s Lynn. Downstream of Brownshill Staunch near Earith the river is tidal. Other significant rivers in the catchment include the Tove (Towcester), Ouzel (east of Milton Keynes), Cam (Cambridge), Ivel (Biggleswade), Lark (Bury St Edmunds / Mildenhall), Little Ouse (Thetford) and Wissey (south of Downham Market).

The tidal Ouse falls within the Wash Shoreline Management Plan boundary as far inland as the A47 bridge at King’s Lynn. In this area, the scope of the SMP and this CFMP overlap. Whereas the SMP focuses on tidal flooding from the Wash, the CFMP focuses on fluvial flooding from upstream and from the tributaries. The CFMP does take into account the influence of tidal levels on the outflow capacity of the rivers.

The Great Ouse and its tributaries form five separate sub-catchments within the CFMP area based on their different hydrological characteristics. These are:

• The River Great Ouse upstream from the tidal boundary (called the Bedford Ouse) and its tributaries; • The tidal River Great Ouse (called the Ely Ouse), the Fens and the Fenland Rivers; • The North West Norfolk Rivers; • The upstream sections of the Cam and its tributaries (called the Southern Rivers); and

Environment Agency 13 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 • The upstream sections of the other tributaries that drain at Denver (Rivers Lark, Little Ouse and Wissey and their tributaries, called the Eastern Rivers).

An overview of the sub-catchments is given in Table 2.1.

Internal Drainage Boards (IDBs) undertake flood management activities across a substantial part of the catchment. There are four principal IDB groups: the Ely Group, the Bedford Group, the King’s Lynn Consortium and the Middle Level Commissioners. The drainage areas covered by the IDBs are shown in Figure 2.3

We have permissive powers to manage flood risk on the Main Rivers in the catchment. Ordinary watercourses and much of the low lying ground are managed by local authorities and the IDBs. Anglian Water and the local authorities manage urban surface water drainage, see Appendix A.

Table 2.1 Sub-catchment overview

North Bedford Southern Eastern West Sub Catchment The Fens Total Ouse Rivers Rivers Norfolk Rivers Population (x 1,000) 762 249 158 89 202 1460 Area (Km2) 3,108,900 1,098,860 1,684,960 818,577 1,873,233 8,586,530 Number of residential 352 113 73 41 96 675 properties (x 1000) Number of commercial 31 11 7 4 8 61 properties (x 1000) Motorways (km) 53 42 0 0 0 0 A-class roads (km) 314 130 83 47 93 667 Railways (km) 226 110 78 22 133 569 Sites of Special 41,448 14,794 387,446 14,406 52,567 510,661 Scientific Interest (km2)

Environment Agency 14 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.1 Main features

Environment Agency 15 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.2 Administrative councils and districts

Environment Agency 16 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.3 Hydrology and IDB areas

Environment Agency 17 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.2 Topography

The topography of the Great Ouse catchment is shown in Figure 2.4. The highest areas are located in the southern and western parts of the catchment with elevations of around 170m ODN (Ordnance Datum Newlyn). Downstream (east) of St Ives are the low-lying Fens comprising about one fifth of the total catchment area. This low lying land is at an elevation close to mean sea level.

The source of the River Great Ouse is located in the highest part of the catchment. The river flows east through relatively steep terrain from its headwaters, before the topography flattens downstream of the River Cam/Lark and Bedford Ouse confluence. River flows downstream of this point are much slower, where the bed slope becomes much flatter and where the floodplain widens through the Fens before reaching the sea. The bed level of the Great Ouse from its source in the west to The Wash in the east is shown on Figure 2.5.

2.3 Geology and hydrogeology

The underlying solid geology of the Great Ouse catchment is shown in Figure 2.6. Chalk dominates the south eastern area of the CFMP whilst mudstone becomes dominant in the northwest, and limestone at the very western end of the catchment. The chalk is permeable containing many cracks and fissures, and in many places is covered only by surface soils. If the surface soils are permeable, rain can easily percolate down into the rock. This reduces the amount of water that flows across the ground surface into rivers. As a result, rivers underlain by chalk deposits tend to have a slower and less significant response to rainfall events. In contrast the mudstone, found in the north west of the catchment, is relatively impermeable so rain cannot easily percolate leading to more run-off and faster responses to rainfall events.

The drift geology at the surface is illustrated in Figure 2.7. At the upstream end of the catchment, gravelly clays lie over the mudstone and limestone. The gravelly clays are relatively impermeable; rain is therefore unable to penetrate into the ground and runs across the surface to the nearest river. Rivers in this part of the catchment therefore tend to react very quickly to rainfall events with a much greater likelihood of flooding, even in places where the underlying solid geology consists of chalk.

In the lower part of the catchment, particularly the Fens, thick deposits of peat or mud cover the mudstone. The peat deposits are dominant in terms of hydrology, and like the chalk are highly permeable. However, the ability of these deposits to adsorb water is constrained by the small difference between the ground surface level (close to mean sea level) and high water table. Once the water table reaches the ground surface no more water can be adsorbed and flooding will occur.

Across the catchment there are distinct localised changes in the geology leading to very different run- off rates between areas and along the course of a river. For example the relatively impermeable clayey soils found in the most upper reaches of the Rivers Lark and Little Ouse run into permeable sandy soils around Mildenhall and Thetford, leading to reduced run-off.

Environment Agency 18 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.4 Topography

Environment Agency 19 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.5 Great Ouse bed levels

Environment Agency 20 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.6 Solid geology

Environment Agency 21 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.7 Drift geology

Environment Agency 22 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.4 Geomorphology

Geomorphology is the study of features and processes operating upon the surface of the Earth.

River Geomorphology is the study of landforms associated with river channels and the processes that form them. It considers the processes of sediment transfer – erosion, transport, and deposition – in river channels and also the relationship between channel forms and processes.

Disruption of sediment transfer in the fluvial/tidal system can have an impact on flood risk through:

1. triggering channel change and, hence, altering water levels associated with a particular flow. 2. promoting erosion and deposition that adversely impacts performance and integrity of existing flood defence structures. 3. delivering potentially polluted sediment to rural floodplains and urban areas. 4. damaging valuable aquatic, riparian and floodplain habitats.

The Great Ouse is a heavily regulated lowland river, where much of it has been heavily engineered for flood defence and land drainage purposes. Modifications include river regulation on many tributaries for navigation purposes, artificial cut-off channels, channel re-alignment and re-sectioning, bank reinforcement, weirs/locks and loss of floodplain connectivity through implementation of flood embankments. All these modifications, together with land use and climate change have altered the sediment load that reaches the watercourses, and the river has adjusted its channel shape accordingly.

A significant proportion of the Great Ouse catchment is used for farming, and therefore the land adjacent to the watercourses presents a source of fine sediment to the river system. The dense drainage network and tributaries enable efficient transfer of this sediment to the main Great Ouse river. The catchment characteristically has shallow gradients, especially downstream of Earith, and hence low stream power. The large volume of sediment and inability to transfer this sediment, results in the Great Ouse being very sensitive to sedimentation problems. Sediment tends to accumulate in or around in-channel structures, such as bridges, culverts and outfalls, reducing their ability to function properly and thus increasing the risk of flooding as the river channel’s ability to hold and convey water is reduced. This is exacerbated by the vegetation growth, and therefore regular maintenance to clear accumulated sediment is required. Such maintenance activities can have both beneficial and detrimental effects on biodiversity and need to be carried out in ways which are sensitive to the environment.

Geomorphological issues within the Great Ouse system are significantly influenced by tidal processes. The tidal Great Ouse River, particularly from the Wash to Earith, shows significant sediment accumulation, most notably when flows from the Bedford Ouse are low. The natural river flow scours accumulated sediment and transports it back towards The Wash. Releases from the Ely Ouse river system to the tidal river via Denver Sluice are also effective in scouring sediment back to The Wash.

Records show that if sediment accumulates due to repeated tidal flows, and the river flows are low, then the bed level at Stowbridge can reduce drainage from the Ouse Washes. Figure 2.8 shows a clear relationship between bed level in the tidal river and river flows following a period of dry weather, based on empirical studies in the 1990s. In addition, the graph shows that the increase in normal river flows from the Bedford Ouse reverses this process and removes sediment from this area. This confirms that river flows are sufficient to maintain low bed levels throughout the tidal zone.

Environment Agency 23 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.8 - Comparison of river flows and bed levels in the Tidal River since 1998

Flow and Highest Mean Mile Bed Level in the Tidal River (1998-2005)

102 101.5 190 101 100.5 170 100 150 99.5 99 130 98.5 98 110 97.5 97 90 (mSLD) 96.5 96 70 95.5 50 95 94.5 30 94 93.5

Highest mean mile bed level in the Tidal River 10 93 92.5 -10 Jul-98 Oct-00 Apr-01 Jun-97 Jan-98 Jun-03 Jan-04 Feb-99 Mar-00 Feb-05 Aug-99 Nov-01 Dec-02 Aug-04 Sep-05 May-02 Time

Actual Bed Level Predicted Bed level using regression equation Offord Flow Denver Flow

Although existing information relating to geomorphology for the Great Ouse is limited, the flood risk management polices in this CFMP will consider the sediment transfer system, ensuring that we maintain or improve the existing conservation value. Furthermore, by working with natural processes, we will aim to promote restoration of the watercourse and floodplain where the opportunity arises.

2.5 Soils

The solid, drift geology and soil type (Figures 2.6, 2.7 and 2.9 respectively) have a direct bearing on how rain water is absorbed into the ground and on the proportion that flows into rivers.

In the West the soil mainly consists of clay, with pockets of chalk and sand to the south; sand, gravel, and chalk become dominant in the east of the CFMP area, with some pockets of mixed clay. In addition, the Fens consist of large pockets of silt, particularly north-west of King's Lynn.

Figure 2.10 shows how the geology and the topography of the catchment combine to determine the ability of the surface soil to accept water during the winter period and how this varies across the catchment. The figures show that those areas categorised as class 1 or 2 (with a high winter rain acceptance potential) are well drained soils such as sand and gravels (found along the river valleys of the Bedford Ouse Ouse catchment) and peat and mud (found down in the lower catchment areas). These soils more readily allow water to enter the ground and to move below the surface. Areas with class 3 or 4 (with a lower winter rain acceptance potential) are poorly drained soils such as gravelly clays (found in the upper catchments). Poorly drained soils can force more water to move over the surface of the land as run-off, and as a result increase the rate at which water reaches the river, leading to quicker rising river levels.

Environment Agency 24 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.9 Soil type

Environment Agency 25 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.10 Soils - Winter Rainfall Acceptance Potential (WRAP)

Environment Agency 26 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.6 Land use and land management

The way people use the land affects both the probability and the consequences of flooding. For example, developed areas, with paving and buildings, can considerably increase rainwater run-off, thereby increasing the probability of flooding. We have examined the possible impacts of changes to land management on river flows in Section 4. At the same time, the type of land use in the floodplain influences the consequences of flooding, i.e. the more people, properties and environmental assets in the floodplain, the higher the potential consequences of flooding will be.

The Great Ouse catchment contains a mixture of land uses with agriculture comprising 65% of the total catchment area, while urban development represents approximately 7% of the total catchment area. This shows the relative importance of agriculture to countryside management in the CFMP area. The distribution of land use is shown in Figure 2.11 and detailed in Table 2.2. Figure 2.11 shows that the Fens area is dominated by arable land, in comparison to the more varied land use in the surrounding areas. Woodland makes up 9% of the Great Ouse catchment and this is primarily located in the Eastern Rivers and Bedford Ouse sub-catchments. Grassland, which could have multiple uses such as livestock grazing or pasture, is evenly spread across the sub-catchments but is particularly dominant in areas which have a poorer agricultural grade (Figure 2.12) and are therefore less suitable for crops.

Table 2.2 Overall distribution of land use on the catchment

Land Use Area (km2) % Arable 5,583 65 Grassland 1,602 19 Woodland 743 9 Urban 585 7 Other 74 <1 Total 8,587 100

The Agricultural Land Classification system allows agricultural land to be graded from best (Grade 1) to worst (Grade 5). Agricultural land of Grade 1, 2 and 3 is among the best and most versatile; nationally only about one third of agricultural land is of this quality. The distribution and quality of land in the Great Ouse catchment is shown in Figure 2.12. Approximately 44% of the agricultural area is of Grades 1 and 2; 45% is Grade 3; and 11% Grades 4 and 5. This highlights the high value of agricultural land within the catchment. Most of the high value agricultural land is located in Cambridgeshire and Norfolk. The lower grade land is mainly found on the higher parts of the catchment where the soils are more gravelly (see Figure 2.7). This division is reflected by less intensive agricultural activity in the higher parts of the catchment compared to the intensive agriculture in the Fens. Within the Fens, the local economy is heavily reliant on the highly productive soils.

Land management

The way agricultural land is managed can influence flood risk by affecting surface water run-off generation and sediment, for example:

• Intensive livestock grazing leads to soil compaction and promotes surface water run-off; and • Growing of crops such as Maize which cover less of the soil surface, makes the land more prone to erosion and surface water run-off.

Land management practices which could potentially mitigate flood risk are encouraged as part of the Environmental Stewardship Scheme. The Environmental Stewardship Scheme is a new agri- environment incentive, which replaces both the Environmentally Sensitive Areas (ESAs) and the Countryside Stewardship Scheme. It provides funding to farmers and other land managers in England to deliver effective environmental management on their land. The Environmental Stewardship Scheme is a potential mechanism through which agricultural land can be used to mitigate flood risk. The scheme could provide opportunities in the Great Ouse catchment which would benefit nature

Environment Agency 27 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 conservation, local communities, and flood risk management. Such opportunities could include the creation of multi-functional wetlands, or conversion of arable land to grassland, in appropriate locations.

There are three stewardship ‘streams’; with the greatest opportunities are likely to come under the Higher Level Stewardship (HLS), which targets high priority situations and areas. Flood protection is a specific objective of the HLS, which aims to:

• make land ‘available’ for flooding; and • implement resource protection measures that will reduce the likelihood of localised flooding incidents.

These aims will be achieved by encouraging land management options that reduce surface water run- off and/or promote storage of floodwater. Management options under the HLS include cattle grazing supplements which would allow economically viable maintenance of converted grassland. As mentioned previously, the opportunity to convert arable land to grassland and change to farming practices requiring less drainage has potential flood management benefits, through a reduction in surface water run-off. The new single farm payment scheme should also encourage similar changes in farming practices and management, as environmentally friendly farming approaches will be better acknowledged and rewarded.

As well as government policy influencing how agricultural land is used and protected, other key factors including consumer demand, climate change, availability of water resources, and the productivity of soils will drive the future of agricultural land use.

Urban development

The extent and location of urban areas define the distribution of impermeable surfaces. Areas that do not allow water to soak into the ground promote surface water run-off and cause a more rapid response to rainfall, and there will be increased flooding if measures are not put in place to tackle this. Urban areas may also be at risk from surface water flooding, ground water flooding and from sewer flooding caused by overloading of the sewerage system during storms (detailed later in Section 3)

The area of urban development in the Great Ouse catchment compared with other similar sized catchments around the country is shown in Table 2.3. Even though the urban extent of the Great Ouse catchment appears to be low (see Figure 2.1) there are many areas which are rapidly growing, such as Milton Keynes. The location and growth of the major urban areas in the catchment over the past 100 years are shown in Figure 2.13. Some of the key urban areas and their populations are detailed in Section 2.9.

Table 2.3 Comparison of urban development in the UK

Catchment Area (km2) Percentage Urban Catchment Thames (downstream to 10,000 8.8% Teddington Weir) Trent (downstream to 8,225 14.6% Cromwell Weir) Severn to Sandhurst 9,986 5.5%

Great Ouse 8,587 7% Source: FEH Handbook

Environment Agency 28 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.11 Land Use

Environment Agency 29 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.12 Agricultural Land Classification

Environment Agency 30 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.13 Prospective urban development in the Great Ouse catchment

Environment Agency 31 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.7 Hydrology

2.7.1 Catchment rainfall

Much of the Great Ouse catchment lies within one of the driest parts of the UK, however, heavy or prolonged rainfall is still the most common cause of flooding. The areas of greatest precipitation occur in the western and north eastern extremes of the catchment with over 700 mm/year of rainfall. Much of the central part of the catchment has less than 600mm/year of rainfall. In comparison, the average rainfall for England is 838 mm/year (1971-2000, source: Met Office). The annual rainfall distribution over the catchment is shown on Figure 2.14.

The dominant flood season is from late autumn to early spring (October-March) when ground conditions are wettest. However, summer flooding can also occur due to short, high intensity, local storms. This is a problem in areas underlain by clay soils or in urban areas where the local drainage system is overwhelmed. Flash storms in the summer are known to have occurred in Newport Pagnell (prior to the recent flood defence scheme), Bury St Edmunds, Bedford (prior to the recent flood defence scheme), Ely, Towcester (prior to the recent flood defence scheme), Leighton Buzzard, Buckingham, Sandy, Biggleswade and the Alconburys.

2.7.2 Fluvial flows

Hydrological units

The Great Ouse catchment consists of three main hydrological units: - the Bedford Ouse: River Great Ouse including tributaries, from the source to the tidal limit at Brownshill Staunch; - the Ely Ouse: River Great Ouse downstream of Brownshill Staunch including the tributaries that drain at Denver; this unit includes the Fens, the Southern Rivers and the Eastern Rivers (see Table 2.1); and - the Norfolk rivers that drain directly into the Wash.

The text below gives an overview of typical flood development in each of these three units, illustrated by historic flood event hydrographs. Figure 2.15 shows how the flow varies with time at key locations throughout the catchment for the 1 in 100 year (1% AEP) flood event.

Environment Agency 32 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.14 Annual rainfall distribution

Environment Agency 33 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.15 Flow hydrographs at key location

Environment Agency 34 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Bedford Ouse

Overall The catchment is orientated south west to north east and so is susceptible to rainfall from typical English winter frontal systems moving across the catchment from the south west. Widespread winter rainfall is common. Much of the Bedford Ouse catchment has soils of moderate or low winter rain acceptance potential (see Figure 2.10). As a result, rainfall can cause rapid and relatively large run- off which can turn into floods. The tidal limit of the Bedford Ouse is at Brownshill Staunch. The most important man-made flood storage areas in this reach are the Towcester Flood Alleviation Scheme FAS and the Milton Keynes storage lakes (see Figure 2.3); these flood storage areas allow upstream and/or urban areas to be drained quickly while preventing high flows affecting downstream areas.

The main tributaries of the Bedford Ouse are the Tove, the Ouzel and the Ivel. Table 2.4 indicates their importance in relation to the main River Great Ouse, based on approximate peak flows from FEH.

Table 2.4 Relative importance of tributaries to Bedford Ouse

Tributary Location of Distance from 1% peak flow of 1% peak flow of confluence source (km) tributary (m3/s) Great Ouse upstream (m3/s) River Tove Stony Stratford 37 90 160 River Ouzel Newport Pagnell 53 150 250 River Ivel Roxton 135 140 350

The peak flow from the River Ivel reaches the confluence more than a day in advance of the peak flow from the Great Ouse catchment. In consequence, the peak flow downstream of the confluence is dominated by the Great Ouse flow rather than the contribution from the Ivel.

At successive confluences along the Great Ouse, the peak flow rate is dominated by flow from the Great Ouse catchment rather than by the joining tributaries. Because of this, it has been possible to develop, by experience, typical times of travel for the flood peak. Times between some key points are shown in Table 2.5.

Table 2.5 Flood peak travel on Bedford Ouse

From To Distance (km) Average Time Rate of Travel of (km/hr) Flood peak (hours) Brackley Buckingham 19 9:00 2.1 Buckingham Stony Stratford 18 8:30 2.1 Stony Stratford Newport Pagnell 16 8:00 2.0 Newport Pagnell Bedford 67 41:30 1.6 Bedford Roxton 15 11:00 1.4 Roxton Offord 17 12:30 1.4 Offord Huntingdon 8 5:00 1.4 Huntingdon Earith 21 16:00 1.3

The following paragraphs describe the characteristics of these sections of the catchment, following the river from the source to the tidal boundary at the downstream end.

Brackley – Stony Stratford The catchment from the source to the River Tove confluence near Stony Stratford is predominantly rural. There is some flood storage influence on flows through spreading over the rivers’ floodplain, but this is not a major feature.

Environment Agency 35 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Stony Stratford – Newport Pagnell Between Stony Stratford and Newport Pagnell there is a wide floodplain. There are inflows to the Great Ouse from Milton Keynes, notably from Loughton Brook.

Confluence with River Ouzel At Newport Pagnell there is the confluence with the River Ouzel, whose flow includes much of the drainage run-off from Milton Keynes. Figure 2.16 uses an event in the autumn of 2000 to illustrate that it is the flow from the Great Ouse catchment and not from the joining River Ouzel that dominates the peak flow rate in the River Great Ouse.

Figure 2.16 - Relative Influence of flows in the Great Ouse and the Ouzel

The charts show flows at Newport Pagnell Main Hourly Rainfall (Foxcote) (on the Great Ouse) and at Willen (on the 7 Ouzel). 6 At each site there is a rapid response to the first 5 rainfall, reflecting local discharges to the two 4 rivers from Milton Keynes and the respective 3 local sub-catchments. The second burst of Rainfall (mm) Rainfall 2 rainfall, early on 29th-30th October, also 1 produces a rapid response. However, as flows 0 27-Oct-0028-Oct-00 29-Oct-00 30-Oct-00 31-Oct-00 01-Nov-00 02-Nov-00 at Willen start to decline the main flow from the

Channel Flow upstream Great Ouse catchment arrives, giving

90 a dominant peak on 31 October. The net flow

Combined flow downstream on the Great Ouse will largely be a function of this flow, rather than that from the 80 Willen Newport Pagnell Main Ouzel. Both flows decline quite quickly and Combined flow have subsided by early on 2nd November. 70

Flow (m³/s) 40

Newport Pagnell Main 30

Willen 20

0 27-Oct-0028-Oct-00 29-Oct-00 30-Oct-00 31-Oct-00 01-Nov-00 02-Nov-00

Newport Pagnell - Roxton From Newport Pagnell to Bedford the flood peak remains fairly constant as there is little floodplain to give attenuation and only a small intermediate catchment area. Flow from the Marston Vale catchment enters at Bedford. Between Bedford and Roxton there is also little floodplain to give flow attenuation.

Roxton - Huntingdon Near Roxton there is the confluence with the River Ivel, whose flow includes input from the River Hiz to the south, and from the River Flit to the south west past Shefford. The Ivel has floodbanks which preclude use of the floodplain until flows exceed about a 1 in 30 year flood event. Between the Ivel confluence and Huntingdon principal tributaries are the River Kym, Brampton Brook and Alconbury Brook, all from the west. These tributaries have a rapid response to rainfall. The relative contribution and timing of flows in this area is illustrated by Figures 2.16 and 2.17.

Figure 2.17 illustrates the relative contribution and timing of the River Great Ouse and its tributaries in this river stretch, based on flow records from the flood event of April 1998. In this event there was

Environment Agency 36 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 particularly high rainfall, equivalent of a 1 in 130 year flood event or greater, over the upper part of the Great Ouse catchment as well as over the catchments of the River Kym and Alconbury Brook. The flow record from St Ives, downstream of Huntingdon, unfortunately stops part way through the event. Again, the overall conclusion is that the flow from the upper Great Ouse catchment dominates the peak flow.

Figure 2.17 - Relative contribution and timing of the Great Ouse, River Ivel, River Kym, and Alconbury Brook

Daily Rainfall (Hockliffe) The charts show a rapid reaction to 40 rainfall at Roxton, from the local Great 35 Ouse catchment, followed by a reaction 30 25 on the Ivel, Kym, and Alconbury Brook. 20 In this instance the flows at Meagre 15 Farm and Brampton are notably higher Rainfall (mm) 10 than at Blunham on the Ivel. This is 5 0 because the Ivel overtops its banks so 07-Apr-98 08-Apr-98 09-Apr-98 10-Apr-98 11-Apr-98 12-Apr-98 13-Apr-98 14-Apr-98 the Ivel does not get higher, but the flow does, making the flow recording at Channel Flow Blunham misleading. In reality the 250 Blunham flow will be greater than is Blunham (Ivel) shown on the graph. Roxton (Great Ouse) Meagre Farm (Kym) St Ives The flow at Offord is seen to rise as Offord (Great Ouse) 200 flows from the Great Ouse, Ivel and Brampton (Alconbury Brook) Offord Kym contribute together. Similarly, the St Ives (Great Ouse) flow at St. Ives rises rapidly, matching the rise at Offord and reflecting the

150 coincident increase in flow from Roxton Alconbury Brook as seen at Brampton.

The more local flows then start to Flow (m³/s) Flow diminish on 11th April. Part way 100 through the 11th April, however, the Brampton flow from the upper catchment at the Great Ouse arrives, as seen by the record at Roxton This is the dominant Meagre Farm 50 flow contribution, giving the greatest flow at Offord and then downstream. The tributary contributions have Blunham declined significantly by this time.

0 07-Apr-9808-Apr-9809-Apr-98 10-Apr-98 11-Apr-98 12-Apr-98 13-Apr-98 14-Apr-98

Figure 2.18 illustrates the flood response along the River Ivel and its tributary the River Flit, showing rainfall and flow records from an event in early January 2003.

Environment Agency 37 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.18 - Flood response on the River Ivel and River Flit

River Ivel Rainfall (Dec 2002) 10 The event followed after a similar, but 9 Flitw ick Letchw orth lesser, event a few days earlier; the 8 Potton decline of the earlier event is seen in 7 6 the flow record for Blunham.

5 st 4 Rainfall from 31 December 2002 into nd 3

Hourly Rainfall (mm) Rainfall Hourly 2 January 2003 produced a flow 2 reaction at Arlesey, on the Ivel near its 1 confluence with the River Hiz. 0 31-Dec-02 01-Jan-03 02-Jan-03 03-Jan-03 04-Jan-03 05-Jan-03 06-Jan-03 However, this reaction is quite modest Time compared to the reaction at Shefford, on the River Flit. The flow at Blunham, near the confluence of the Ivel and the River Great Ouse, is initially dominated River Ivel Flows (Dec 2002) by flow from the River Flit but later is 35 Arlesey (Ivel sustained by other run-off contribution 30 Upstream) Blunham (Ivel north of Arlesey. Dow nstream) 25 Shefford (Flit)

20 A similar form of response was seen in April 1998, except in that event the 15

Flows (m3/s) relative flow contribution from the River 10 Flit was less than seen in January 5 2003.

0 3 1-Dec-02 0 1-Jan-03 0 2-Jan-03 03-Jan-03 04 -Jan-03 05-Jan-03 06 -Jan-0 3

Time

Huntingdon – Earith Between Huntingdon and Earith there is a very wide floodplain, allowing significant flood storage and flow attenuation before the river reaches Earith and the Ouse Washes. It is common for high flood levels to be sustained for a week or more in this area as flood waters enter and leave storage over the floodplain.

Ely Ouse

Overall The Ely Ouse catchment is the eastern and southern part of the Great Ouse catchment draining to Denver. The catchment area includes the South Level, a fenland area whose drainage is managed by Drainage Boards. Most of the catchment is flat and has soils with a very high or high winter rain acceptance potential (see Figure 2.10). As a result, the reaction of river flows to rainfall is slow and moderate compared to the Bedford Ouse catchment. The catchment is almost wholly rural. There are a number of man-made flood storage areas; the most important are the Ouse Washes (also referred to as the Hundred Foot Washes), the Flood Relief Channel and Adventurer’s Fen.

The Ely Ouse to Denver collects flood flow from three directions: - the Old West River and its tributaries (to the south west); - the Cam and its tributaries (to the south); - the Lark, Little Ouse and Wissey (the Eastern rivers).

Table 2.6 indicates the importance of the tributaries in relation to the main River Great Ouse, based on approximate discharge values from FEH and broadscale modelling at locations just upstream from the relevant confluences.

Environment Agency 38 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 2.6 Relative importance of sub-catchments

Tributary 1% peak flow (m3/s) River Great Ouse (Earith) 340 River Cam 170 River Lark 70 River Little Ouse 100 River Wissey 50

Flood levels in the Ely Ouse and adjoining embanked rivers (including the Old West River) are controlled by flood management intervention at the Denver sluice complex. The intervention aims to ensure sufficient depth of water for navigation at normal times, yet hold water down to safe levels at time of flood. The text below describes how the Southern and Eastern sub-catchments and the Fens area respond to rainfall, leading up to conclusions about relative timing of peaks.

Typical time of travel for flood peaks on some of the Ely Ouse tributaries have been measured. Travel times between some key points are shown in Table 2.7 below:

Table 2.7 Time of travel of flood peak for given rivers

River From To Time of Travel of flood peak (hours) Rhee Wimpole Burnt Mill (Hasling 24 field) Cam Great Chesterford Dernford 15 Cam Dernford Byrons Pool 10 Cam Byrons Pool Jesus Sluice 3 (Cambridge) Little Ouse Knettishall County Bridge, 20 Euston Thet Bridgham Thetford 24

River Cam The Cam catchment to Byrons Pool contains sub-catchments for the Cam itself, the River Rhee and Bourn Brook to the west and the River Granta to the east. None of the rivers have an extensive floodplain, so there is only limited flow attenuation through natural flood storage. Although the southern part of this catchment rises on chalk, groundwater flow from the chalk is not seen as a factor in flood flows.

Figure 2.19 illustrates the relative influence and timing of flows to Byrons Pool, showing rainfall and flow or stage records from an event in February 2001. Stage records are only included where no equivalent flow record is available. The example shows that the Rivers Cam and Rhee dominate overall flood flows.

Environment Agency 39 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.19 - Relative influence and timing of flows to Byrons Pool and Cambridge

Hourly Rainfall (Elmdon) th 6 Rainfall on 12 February produces a

5 rapid reaction to flow in all the rivers flowing to Byrons Pool. On the Rhee 4 and Granta there is an initial rapid rise 3 followed by a further rise in flow 2 Rainfall (mm) sustained over about a day. The 1 reaction on the Cam, as seen at 0 11-Feb-01 12-Feb-01 13-Feb-01 14-Feb-0115-Feb-01 16-Feb-01 17-Feb-01 Chesterford, and on Bourn Brook is more transient. The effect at Byrons Channel Flow or Stage Pool, as seen by stage recordings, is 14 an initial rapid rise rather than a Chesterford flow (Cam) sustained level as the Rhee Stapleford flow (Granta) contribution continues while flows from Burnt Mill flow (Rhee) 12 Burnt Mill (Rhee) the other rivers decline. The effect at Chesterford (Cam) Bourn Brook stage Byrons Pool stage (Cam) Byrons Pool is also seen at Jesus Jesus Lock stage (Cam) Lock, Cambridge. 10 Overall, the dominant flood flows are initially from the River Cam and later Byrons Pool stage 8 from the River Rhee.

Flow (m³/s) andStage(m) Jesus Lock stage

2 Stapleford (Granta) Bourn Brook stage

0 11-Feb-0112-Feb-01 13-Feb-01 14-Feb-01 15-Feb-01 16-Feb-01 17-Feb-01

Downstream of Cambridge, the River Cam soon becomes an embanked river crossing the South Level. It has tributaries, such as Soham Lode, from the east.

Eastern Rivers

The eastern catchment rivers, the Lark, Little Ouse and Wissey, react slower to rainfall than is usual elsewhere in the Great Ouse catchment.

The River Lark is embanked for a distance upstream of Mildenhall, so floodplain storage is only used in floods greater than about 1 in 20 years return period. Figure 2.20 illustrates that the flow peaks on the Lark and its tributary the River Kennet occur at least 24 hours after the peaks of the rainfall.

Environment Agency 40 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.20 - Timing of flows on the River Lark and Kennet

st Daily Rainfall (Burrough Green) Rainfall on 31 December 2002 14 produces a flow reaction on both rivers 12 the following day with further rain on 10 2nd January increasing the flow. Flow 8 peaks are at least 24 hours later, with a 6 fairly rapid decline thereafter. Rainfall (mm) Rainfall 4 Flow in the River Kennet is broadly in 2 proportion to that in the River Lark 0 31-Dec-02 01-Jan-03 02-Jan-03 03-Jan-03 04-Jan-03 05-Jan-03 06-Jan-03 bearing in mind their respective catchment areas. The peak in the Channel Flow Kennet is broadly 18 hours earlier than 16 that in the Lark. The peak flow at Temple (Lark) Temple, a little to the east of 14 Beck Bridge (Kennet) Mildenhall, arises about 36 hours after Temple the peak of the rainfall.

8 Flow (m³/s)

6 Beck Bridge

0 31-Dec-0201-Jan-03 02-Jan-03 03-Jan-03 04-Jan-03 05-Jan-03 06-Jan-03

The River Little Ouse and its tributaries upstream of Thetford have areas of floodplain which is utilised in flood events. Downstream of Thetford the river valley is more defined so floodplain storage is not a notable feature. Flood response on the Little Ouse and tributaries to Thetford is even slower than on the other rivers, as illustrated by Figure 2.21, based on the same January 2003 event. Note that the rainfall pattern for the Little Ouse catchment in this event was different from the situation on the Lark.

Environment Agency 41 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.21 - Flood response on the Little Ouse and tributaries to Thetford

There is a slow reaction to rainfall on all Hourly Rainfall (Mundford Road) the tributaries, Sapiston Brook and the 8 Little Ouse to County Bridge as well as 7 the River Thet to Melford. Peak flows 6 5 arise over two days after the rainfall 4 and there is no initial rapid reaction to 3 the rain. The response time of the Rainfall (mm) 2 tributaries are similar to the flow at 1 Abbey Heath, just downstream of 0 Thetford, becoming almost a simple 29-Dec-02 30-Dec-02 31-Dec-02 01-Jan-0302-Jan-0303-Jan-03 04-Jan-0305-Jan-03 06-Jan-03 07-Jan-03 aggregation of the separate tributary Channel Flow 30 inflows.

Rectory County Bridge, Euston Melford (Thetford) 25 Abbey Heath Abbey Heath

Melford 15 Flow (m³/s)

County Bridge 10

Rectory

0 29-Dec-02 30-Dec-02 31-Dec-02 01-Jan-0302-Jan-0303-Jan-03 04-Jan-0305-Jan-03 06-Jan-03 07-Jan-03

Flood response on the River Wissey is gradual, and peaks about 36 hours after the centroid of the rainfall. This is illustrated by Figure 2.22, based on records for an event in January 2002.

Environment Agency 42 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.22 - Flood response on the River Wissey

River Wissey Rainfall (Jan-Feb 2002) 8 Rainfall over 26th/27th January gave a 7 Carbrooke flow response at Northwold peaking on th th 6 the 28 . Further rainfall on the 30 5 January gave a second peak early on st 4 1 February.

Hourly Rainfall (mm) 2

0 26-Jan-02 27-Jan-02 28-Jan-02 29-Jan-02 30-Jan-02 31-Jan-02 01-Feb-02

Time

River Wissey Flows (Jan-Feb 2002) 7

6 Northwold combined 5

3 Flows (m3/s) Flows 2

0 26-Jan-02 27-Jan-02 28-Jan-02 29-Jan-02 30-Jan-02 31-Jan-02 01-Feb-02 Time

Relative timing of flood peaks From the foregoing, the time from the centroid of rainfall to peak flow reaching the Ely Ouse/cut off channel system at the South Level area is generally a little over 36 hours (Cam, Lark, Wissey) but is longer, at about 3 days lag, for flow from the Little Ouse.

Analysis of land drainage pumping from Burnt Fen, in the South Level, between the Little Ouse and Ely Ouse rivers, shows that rain on one day will initiate pumping on the next day. Taking this response as typical of the South Level, and combining it with the rivers’ response as described above, it seems that the separate peak discharges to the Ely Ouse/Cut Off Channel system are likely to be broadly coincident in their timing. An exception is flow from the Little Ouse, which would peak later than from other sources.

Norfolk Rivers

The Norfolk Rivers are the Nar, the Babingley, the Ingol and the Heacham. They are independent systems that discharge either to the tidal reach of the Great Ouse downstream from Denver, or directly into the sea. The Nar downstream of Marham is embanked across the lowland to King’s Lynn. In the past these banks have breached when river levels have got too high, flooding adjacent farmland and some properties. The recently completed flood improvement scheme aims to reduce flooding problems to an acceptable level.

Environment Agency 43 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.8 Environment and heritage

2.8.1 Introduction

The Great Ouse CFMP area contains numerous sites of national, European, and international importance, supporting a rich diversity of flora and fauna. The following is a summary of the numbers of designated and non designated sites within the Great Ouse catchment:

• 2 Special Protection Areas (SPAs) and 1 potential SPA; • 11 Special Areas of Conservation (SACs); • 8 Ramsar sites; • 242 Sites of Special Scientific Interest (SSSIs); • 1078 Scheduled Ancient Monuments (SAMs); • 27 National Nature Reserves (NNRs); and • 1,815 County Wildlife Sites.

2.8.2 Statutory designated sites

A range of sites within the Great Ouse CFMP area have been designated for protection due to their nature conservation or geological conservation value. These include both national and international designations. The locations of all the statutory designated sites associated with the natural environment are shown in Figure 2.23 and 2.24. Within the Great Ouse CFMP area there are 16 sites of European and or international interest, these are summarised in Table D.1 in Appendix D. Amongst these key European and international sites, perhaps the most commonly known is the Ouse Washes.

The Ouse Washes, is an extensive area of seasonally flooded wet grassland (‘washland’) lying between the Old and New Bedford Rivers. Its principal role is as a floodwater storage system during winter months and occasionally during the spring and summer. It is one of the country's few remaining areas of extensive washland habitat. The cycle of winter floodwater storage along with traditional summer grazing by cattle and hay production has given rise to a mosaic of rough grassland and wet pasture with a rich biodiversity.

The Ouse Washes is designated as a Ramsar site and Special Protection Area (SPA) for supporting nationally and internationally important numbers of wintering waterfowl, and nationally important numbers of breeding waterfowl. It is also designated as a Special Area of Conservation (SAC)1 primarily for supporting spined loach (Cobitis taenia).

Much of the conservation importance of the Ouse Washes is due to its continued use as functional washland, with extensive winter flooding and traditional forms of agricultural management, including grazing and mowing of permanent grassland and rotational ditch management.

In recent years, spring flooding and summer flooding (April-October) has adversely affected both the breeding birds and the traditional washland management regime. Severe siltation in the tidal Great Ouse is a factor affecting the drainage of the Ouse Washes. The new sluice at Welmore Lake has, however, improved the speed of removal of water since its completion in 1999. Nutrient enrichment, due to high phosphorus concentrations in the spring and summer water, also continues to be a problem, likely to result in the decline of some plant, fish and invertebrate species.

Works to restore an acceptable flood regime would be extensive and costly (in the order of £50 to £87 million), and there is a high risk that they could have an unacceptable knock-on effect on other parts of the Fens. In view of the cost and the high risks and uncertainties, this approach is not being pursued. A decision has been taken to replace the degraded habitat of the Ouse Washes, by creating approximately 1,000 hectares of wet grassland habitats in the Fens.

1 All sites designated as SACs also form part of the European network of Sites of Community Importance (SCI). Environment Agency 44 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Due to the level of protection afforded to the Ouse Washes, even with the compensatory habitat, the nature conservation value cannot be allowed to decline any further. With this in mind further work needs to be done to improve water management in the Washes, e.g. improvements in drainage from the site or improved attenuation of summer floods.

The catchment also contains 242 Sites of Special Scientific Interest (SSSIs), that are comprised of over 500 component parts (Figure 2.23). The sites range in size from 0.6ha to 18,000ha.

Natural England has assessed the Conservation Status of each SSSI, with a view to achieving the Government's Public Service Agreement target of 95% of SSSI land to be in 'favourable' or 'recovering' condition by 2010. Of the 94 SSSIs that fall within the 1 in 100 year flood extent, 73 have at least one unit considered to be in unfavourable status. Of those 73, there are 20 SSSIs for which water related issues (e.g. water levels, water abstraction, inappropriate drainage, etc.) directly contribute to the unfavourable status. These are detailed within Table D.2 in Derby Fen, North West Norfolk Appendix D. However, it should also be noted that there may be indirect impacts of water level management / flood management that can contribute to the site’s unfavourable status, for example scrub encroachment in part resulting from low water levels. Any operations which could damage the special interest of the site would require Natural England’s permission.

There are also 27 National Nature Reserves within the catchment, which have been designated for their important natural features.

2.8.3 Non-statutory designated sites

Whilst the Old Bedford River (part of the Ouse Washes SSSI) and the River Nar are the only riverine SSSIs in the catchment, all the major rivers in the catchment (excluding the lodes) are County Wildlife Sites (CWSs). Examples are: the Rivers Cam, Rhee, Granta, Great Ouse, Lark, and Little Ouse. Further County Wildlife Sites in the catchment (which total 1815) include; Micklemere wetland near Bury St Edmunds, Norah Hanbury-Kelk Meadows near Barton Mills, Kingfisher’s Bridge wetland near Wicken, and Ely Beet Pits. Although these are generally small, they do form an important network of sites which can provide links between some of the larger designated sites listed (e.g. SSSIs).

There are several sites within the catchment which have been identified for current and future wetland creation. Further information on three key sites (Great Fen, Needingworth Wetland and Wicken Fen) has been included in Appendix F.

2.8.4 Important habitats and species

A UK Biodiversity Action Plan (BAP) was adopted in 1994 following the Rio Earth Summit. This plan includes Action Plans for over 400 species and habitats and sets out the essential work required to ensure the conservation of these key habitats and species. These actions are taken forward by local BAPs and for a selection of these, the Environment Agency is identified as the lead organisation to take this action forward. The Great Ouse catchment is included within the Cambridgeshire BAP, and parts of the Norfolk, Suffolk, Bedfordshire and Luton, and Buckinghamshire and Milton Keynes BAPs.

Environment Agency 45 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 We have a Biodiversity Action Strategy for Anglian Region that takes forward many of the actions to conserve the habitats and species listed within the BAPs. We also contribute towards Government targets to bring 95% of all Sites of Special Scientific Interest in England into favourable condition by 2010 through our Flood Risk Management Strategy (2003 – 2008).

The BAPs covering the Great Ouse CFMP detail objectives and actions for a range of vulnerable habitats and species found within the catchment. Habitats found within the catchment are shown in Figure 2.25 and summarised in Table 2.8 below.

Table 2.8 BAP habitats in the Great Ouse catchment

Feature Total Number Total Area % (Based on Area) Saline Lagoons 2 30.69 0.12 Undetermined Grassland 144 2693.16 10.24 Undetermined Woodland 39 81.786 0.31 Upland Hay Meadows 1 9.34 0.04 Upland Oakwoods 23 134.11 0.51 Wet Woodland 613 6901.79 26.24 Lowland Meadows 123 4259.44 16.20 Lowland Mixed Deciduous Woodland 138 2333.27 8.87 Maritime Cliff and Slope 1 0.28 0.00 Purple Moor Grass and Rush Pastures 91 1181.32 4.49 Reedbeds 56 7631.38 29.02 Fens 69 1043.33 3.97 TOTAL 1300 26299.94 100

Those habitats and species particularly relevant to catchment flood management are detailed within Appendix H, and include amongst others: Fens, reedbeds, wet woodland, water vole, otter, great crested newt, white-clawed crayfish, and Desmoulin’s whorl snail.

In addition, there are also a number of other environmental documents and initiatives with implications for catchment flood management including:

• Integrated Washland Management for Flood Defence and Biodiversity (English Nature Research Report No. 598, 2004); • 50 year Vision Map for Cambridgeshire and Peterborough; • County Vision for Norfolk; • Regional Biodiversity Map (Environment Agency Regional Biodiversity Forum, 2005); • Regional Biodiversity Audit (Environment Agency Regional Biodiversity Forum); • Anglian Region Joint Strategy and Water Resources for Wetland Creation (Cranfield University, 2000); • A Vision for Nature Conservation in the Norfolk Coast AONB 1997-2022 (English Nature, The National Trust and Norfolk Wildlife Trust); • The State of England’s Chalk Rivers (English Nature and Environment Agency); • River Audit for the River Nar (Environment Agency, English Nature and King’s Lynn Consortium of Internal Drainage Boards); • The Great Fen Project (Whittlesea Mere); • The Regional Woodland Strategy ‘Woodland for Life’ (EERA and the Forestry Commission); • The Greater Peterborough Green Grid Strategy (Peterborough City Council and Partners); • The Green Infrastructure Strategy for Cambridgeshire (Cambridgeshire Horizons and Partners); • Discovering the Flit Valley: Local Heritage Initiative (Wildlife Trust, Greensand Trust, Local Authorities and communities);

Environment Agency 46 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 • Needingworth Wetland Project; • Wicken Fen; • Great Ouse Strategy Project (Report prepared by Hull University, 2005); • Wet Fens Partnership Strategy (Local Environment Agency team); • Cavenham-Icklingham Heaths SSSI Floodplain Storage to Achieve Biodiversity Objectives (Local English Nature team); • The Wash Estuary Strategy Group Initiative (Wash Estuary Strategy Group); • Wetland habitat creation on River Babingly, Norfolk (Local English Nature team); • Huntingdonshire Wet Woodlands and Wet Meadows Project (Huntingdonshire District Council, Forestry Commission, FWAG, and the Wildlife Trust); • The Bedfordshire Wet Woodland Project (Forestry Commission, FWAG, Beds County Council, Environment Agency, DEFRA, and English Nature); • The Norfolk Wet Woodland Project (Forestry Commission, FWAG, Norfolk County Council, Environment Agency, DEFRA, and English Nature); • The Ivel and Ouse Countryside Project (Bedfordshire Rural Communities Charity); and • The Peterborough Wet Woodland Project (Forestry Commission, Peterborough City Council, Peterborough Environment City Trust, Environment Agency, English Nature, and the Wildlife Trust).

2.8.5 Landscape

Flooding has the potential to indirectly affect the landscape character of the catchment. The landforms of the catchment have been formed by river and tidal processes, and have subsequently been modified by man. Some vegetation forms within the landscape are affected by the pattern of flooding, for example, the species composition of some habitats rely on periodic inundation. Changes to flood risk management could alter the pattern of flooding and hence, change some of the natural features within the landscape.

The Norfolk Coast, which forms the northern boundary to the CFMP (see Figure 2.23), is designated as an Area of Outstanding Natural Beauty (AONB). The Norfolk Coast AONB was designated in 1968, and is now managed by the Norfolk Coast Partnership, which works closely with local authorities and National Bodies. It has a total area of approximately 450 km2, extending up to 6km inland. The area comprises a diverse landscape from high boulder clay cliffs east of Weybourne, through the remote marsh coastlands, to the silt expanses of the Wash.

The area includes a variety of habitats of unique scientific and ecological value including salt-marsh, intertidal flats, dunes, shingle, grazing marsh and ancient woodland. These habitats provide home to a range of important plant and animal species including sea lavender (Limonium bellidifolium), sea heath (Frankenia laevis), sandwich tern (Sterna sandvicensis) avocet Recurvirostra avosetta, marsh harrier Circus aeruginosus, natterjack toad (Bufo calamita), and otter (Lutra lutra). A small part of the Chilterns AONB also lies within the south west portion of the Great Ouse catchment.

There are twelve Joint Character Areas (described by the Countryside Agency) that fall within the catchment: North West Norfolk, The Fens, Mid Norfolk, Breckland, South Suffolk and North Essex Clayland, South Norfolk and High Suffolk Claylands, Chilterns, Upper Thames Clay Vales, Bedfordshire and Cambridgeshire Claylands, Bedfordshire Greensand Ridge, East Anglian Chalk, and Yardley-Whittlewood Ridge. Joint Character Areas (also called Landscape or Countryside Character Areas) combine both English Nature’s Natural Areas and the former Countryside Commission’s Countryside Character Areas. These were first devised as a means of describing the essential character of distinct areas of the English countryside, based on the landscape, wildlife and natural features. They are now widely used for a range of applications, including the targeting of Defra’s Environmental Stewardship scheme. The important features of these are detailed in Appendix E and summarised in Table 2.9.

Environment Agency 47 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 2.9 Summary of Joint Character Areas

Joint Character Area Key Features North West Norfolk • Large-scale arable and grassland landscape. • Huge estates giving a unified and well-managed quality to the landscape. • Wide road verges with uniform hawthorn hedges set well back and well-maintained. • Large and widely spaced villages. The Fens • Large-scale, flat, open landscape. • A hierarchy of rivers, drains and ditches provide a strong influence throughout the area. • Roads, rail and settlements are largely on raised banks or islands respectively. • Rich and varied intensive agricultural land use. Mid Norfolk • Variable geology and topography, with extensive sand and gravel. • Predominantly arable, with variable field sizes. • Relatively well-wooded. Breckland • Vast commercial conifer plantations. • Distinctive large-scale landscape. • Unique geology. South Suffolk and North Essex • Broadly flat, chalky, boulder clay plateau dissected by undulating Clayand river valley topography. • Predominantly arable with wooded appearance. • Remnant ancient countryside. South Norfolk and High Suffolk • Numerous Saxo-Norman and medieval churches. Claylands • Almost entirely arable. • Few major transport routes. Chilterns • Extensive areas of beech woodland. • Chalk hills and plateau. • Small fields and dense network of ancient hedges. Upper Thames Clay Vales • In Buckinghamshire, the Vale is a predominantly pastoral landscape. • Brick-built buildings reflect the widespread use of the local clay as a building material. Bedfordshire and • Predominantly an open and intensive arable landscape. Cambridgeshire Claylands • Settlements clustered around major road and rail corridors (A1 and M1). • Man-made reservoir at Grafham Water. • Gently undulating topography and plateau areas, divided by broad shallow valleys. Bedfordshire Greensand • Number of historic parklands and estates. Ridge • Existing and redundant sand quarries especially around Leighton Buzzard. • Mixed land use. East Anglian Chalk • Distinctive, open, variable topography of the Chalk. • Long straight roads. • Large-scale rolling downland, mainly arable. • Ash-dominated woodland. Yardley-Whittlewood Ridge • Shallow soils. • A strong historic landscape character with extensive areas of ancient woodland. • Mixed land uses of pasture, arable and woodland. • Low density of settlement.

Environment Agency 48 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.23 Designated nature conservation sites of national, European and international interest

Environment Agency 49 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.24 Designated nature conservation sites of international importance

Environment Agency 50 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.25 UK BAP habitats

Environment Agency 51 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.8.6 Legislation

In line with the requirements of the Water Framework Directive (WFD), which imposes a requirement for member states to achieve "Good Ecological Status” or “Good Ecological Potential” on all bodies of surface water by 2015, we will ensure that our decisions on flood risk management, in the Great Ouse catchment, are based on a good understanding of any potential impacts on biodiversity. The integration of SEA within the CFMP further strengthens the appreciation of the potential effects of future flood risk and flood risk management on the environment. We will aim to, wherever possible, develop policies which do not compromise the needs of the natural environment, and embrace any opportunities identified for the enhancement and conservations of important species and habitats.

One of the problems faced by ourselves is how to improve the status of the affected reaches for fish and the wider biodiversity. Opportunities for environmental improvements and the reconnection of the historical floodplain are limited by factors such as the flood risk to property, potential disruption to navigation and possible impairment of currently designated wildlife interests. This is of concern due to future obligations under the EU Water Framework Directive (WFD). The River Great Ouse has been subjected to extensive modification, either for flood defence, navigation, or land drainage purposes. These uses constrain the potential to rehabilitate the river into a more natural state. At present, the watercourses within the catchment have not had their Water Framework Directive (WFD) classification finalised. We anticipate that many will be classified as heavily modified, if they are considered at risk of failing Good Ecological Status by 2015 due to irreversible morphological changes. The Directive indicates that even for a heavily modified water body, Good Ecological Potential should be achieved. To date, much of the rehabilitation work in the Great Ouse catchment has been fragmented and has traditionally targeted single species. As a result, rehabilitation programmes have been largely ineffective. A more strategic approach to rehabilitation is needed to ensure that the Great Ouse catchment achieves “Good Ecological Status” or “Good Ecological Potential” in the future. The CFMP offers the opportunity to make a significant contribution to this process.

2.8.7 Fisheries

The Freshwater Fish Directive was adapted in 1978 to protect and improve fresh waters that support fish life. The Directive requires the designation of appropriate rivers and lakes into two categories of water:

• those suitable for salmonids (mainly salmon and trout but also grayling); and • those suitable for cyprinids (including carp, tench, bream, roach, chub and minnows).

There is a diverse range of fisheries habitats within the Great Ouse catchment covering both salmonid and cyprinid habitats. The habitats range from the drains and slow moving rivers in the lower catchment, to the fast flowing upper reaches of the Great Ouse. The majority of these rivers and drains also support recreational fishing.

The Upper Ouse and its tributaries predominantly support coarse fish with a small population of brown trout (Salmo trutta). Native brown trout populations are also found in the upper reaches of the Rivers Heacham, Babingley, Nar, and Bedford Ouse. The Upper Ouse above Bedford is an excellent fishery for fast flowing species such as chub (Leuciscus cephalus), dace (Leuciscus leuciscus), roach (Rutilus rutilus) and barbel (Barbus barbus). The Bedford Ouse by contrast is a typical lowland river and holds good numbers of species preferring slower flows, such as bream (Abramis brama), tench (Tinca tinca) and perch (Perca fluviatilis).

The Middle Level System and other drain networks in the catcment, hold large numbers of coarse fish including pike (Esox lucius) and eel (Anguilla anguilla). Migratory eel (Anguilla anguilla) and sea trout (Salmo trutta) have also been known to migrate up the Nar, and the Great Ouse as far as St Ives. Various river systems within the catchment, however, have locks and weirs which can restrict these migratory species.

Estuary species such as flounder (Platchthys flesus) and smelt (Osmerus eperlanus) are found up to and beyond the tidal limit of the Great Ouse.

Environment Agency 52 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

There are also large numbers of stillwaters in the catchment; these provide both coarse and game fishing.

For the catchment in general, the river systems do not currently provide the optimum environment to sustain healthy fish populations. The heavy modification of the River Great Ouse in the past has resulted in channelisation of rivers, regulation of flow, detachment of the main channel from the floodplain, and general impoverishment of the floodplain system. The consequences of these activities are all detrimental to biodiversity and fisheries. They eliminate important breeding, nursery, refuge and feeding habitats and constrain natural ecological processes which results in poorly-structured plant and animal communities.

2.8.8 Tourism and recreation

The catchment has a wealth of tourist attractions. These include coastal resorts such as Hunstanton, attractive countryside, renowned nature conservation sites such as the Ouse Washes, market towns and villages, the waterways of the Fens and heritage cities and towns such as Cambridge, Ely and Bury St Edmunds. The tourist industry is important to the catchment both in terms of the jobs it provides and the money it brings into the area. There is a variety of recreation activities carried out on, or near the water including: walking, bird watching, angling, horse riding, cycling, waterskiing, boating and canoeing, picnicking and visiting water side areas. The catchment benefits from a vast network of bridleways, footpaths (e.g. the Ouse Valley Way, Kingfisher Way and Nar Valley Way), national cycle routes, and river access for boats and canoes. There are also numerous riverside and waterside parks for recreation and leisure purposes, including Grafham Water Nature Reserve, and Hinchingbrooke Country Park.

The Great Ouse and some of its tributaries, some of the fenland watercourses, and the Grand Union Great Ouse at St Ives Canal provide about 240 km (150 miles) of navigable waterway within the catchment. This includes the recently opened Relief Channel navigation, which runs between Denver and King’s Lynn. Several authorities are responsible for Navigation including British Waterways and the Environment Agency. Existing navigation waterways are shown on Figure 2.26.

Additional proposed waterways (subject to approval) include the Nar canal, the Bedford to Milton Keynes Link and the Fens Waterways Link between the River Witham, the Middle Level and the Ouse. These are also shown on Figure 2.26.

Changes to flood risk management could impact upon a number of tourism and recreational sites and cause temporary disruption to the use of these sites and their activities.

Environment Agency 53 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.26 Navigation

Environment Agency 54 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.8.9 Surface water quality Maintaining water quality is vital for many uses including spray irrigation, fisheries, amenity and conservation, and the CFMP will seek to ensure that water quality is not adversely affected by any flood risk management operations.

There are two general schemes for reporting on surface water quality in rivers, these are: the General Quality Assessment (GQA) scheme; and the Water Quality Objectives (WQO) scheme. The GQA scheme grades key stretches of watercourse in terms of chemical, biological, nutrient and aesthetic character, whereas the WQO scheme sets clear water quality targets.

The GQA scheme, using water quality data collected on a three year basis, allows us to monitor trends in water quality, so we can identify degrading rivers and take action where necessary. Chemical GQA grades (‘A’ to ‘F’) represent pollution from common sources such as agriculture and waste treatment works, by measuring the presence of dissolved oxygen, biochemical oxygen demand, and ammonia. Biological GQA grades (‘A’ to ‘F’) are based on macro-invertebrate communities, which are invertebrates that can be seen with the naked eye (e.g. insect larvae). Macro-invertebrates have varying tolerances to pollutants, so can be used to give an indication of pollution, by their presence or absence, and abundance, compared to what would be expected if the water was in good environmental condition.

Chemical and biological GQA grades (2004) for monitored watercourses in the Great Ouse catchment are shown in Figure 2.27 and Figure 2.28. Table 2.10 summarises the distribution of these grades in the catchment.

Table 2.10 Chemical and biological General Quality Assessment grades (2004) for the Great Ouse catchment

Chemical GQA Percentage of catcment (%) A (Very Good) 6 B (Good) 42 C (Fairly Good) 25 D (Fair) 14 E (Poor) 13 F (Bad) 0

Biological GQA Percentage of catchment (%) A (Very Good) 39 B (Good) 35 C (Fairly Good) 20 D (Fair) 5. E (Poor) 0.4 F (Bad) 0

The chemical GQA data presented in table 2.10 and figure 2.27 shows that over 70% of the Great Ouse catchment has a water quality of fairly good to very good, with approximately 27% rated as fair to poor. Whereas the biological GQA data presented in table 2.10 and figure 2.28 shows 95% of the catchment to be rated as fairly good to very good, with approximately 5% rated as fair to poor.

River reaches that are monitored for their water quality also have River Quality Objectives (RQOs) which are based on the recognised uses of a river.

A River Quality Objective (RQO) is a target used to help protect and improve river water quality. We give each river a target from our River Ecosystem (RE) classification scheme that, if met, would support a particular type of habitat. This classification system ranges from 1-5, where 1 represents water of very good quality suitable for all fish species, and 5 represents water of poor quality which is

Environment Agency 55 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 likely to limit coarse fish populations. RQOs are used to set discharge consents and to carry out other water quality planning activities. Generally, the water quality target is higher for rural watercourses and lower for those in urban areas.

The RQOs for the Great Ouse catchment are shown in Figure 2.29. These show that the majority of the water courses are required to achieve at least fair water quality; a realistic target for such heavily modified reaches. Many of the upper river reaches are required to achieve at least good quality.

These RQOs may change in light of new legislation, for example the EU Water Framework Directive. This Directive requires Member States to work towards, and achieve at least “Good Ecological Status” in all bodies of surface water. However, some water bodies (artificial water bodies and heavily modified water bodies) will only have to achieve “Good Ecological Potential”. The Directive is mainly concerned with ecological status (water chemistry, water resources and water hydromorphology) of water ecosystems, although this has significant implications for flood risk management.

There are several watercourses designated as Eutrophic Sensitive Areas under the Urban Waste Water Directive. These include Foxcote Reservoir, Grafham Water and the River Great Ouse (Ouzel to Welney).

2.8.10 Groundwater quality

The EU Water Framework Directive requires Member States to identify and assess groundwater and groundwater-fed terrestrial systems. All flood risk management measures will need to consider what environmental measures, in relation to groundwater resources and quality, will be required to comply with the Directive. This also will in turn affect the selection of flood risk management policies within this CFMP.

The issue of groundwater protection is important as a significant proportion of public water supply for the catchment comes from groundwater sources. The major aquifers within the Great Ouse CFMP area include: the Great Oolite, Chalk and Woburn Sands and alluvial sand and gravel aquifers which are located in the Upper Ouse and Bedford Ouse. There are also significant aquifers located in the north-west Norfolk area, this includes, the Sandringham sands and chalk aquifer. There are no substantial aquifers in the Old Bedford and Middle Level areas.

Throughout England, nitrate levels of surface water and groundwater are increasing. This is a concern as the nitrate has to be removed before water can be supplied to customers. Much of the catchment, including parts of Cambridgeshire, Bedfordshire, Buckinghamshire, Norfolk and Suffolk, have been designated as either groundwater and/or surface water Nitrate Vulnerable Zones (NVZs) in accordance with the EC Nitrates Directive. This Directive is an environmental measure designed to reduce water pollution by nitrate from agricultural sources and to prevent such pollution occurring in the future.

Environment Agency 56 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.27 Chemical water quality (GQA, 2004)

Environment Agency 57 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.28 Biological water quality (GQA, 2004)

Environment Agency 58 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 2.29 River Water Quality Objectives

Environment Agency 59 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2.8.11 The historic environment

The Great Ouse catchment is rich in heritage sites, ranging from Conservation Areas in small villages, through to Scheduled Ancient Monuments (SAMs). The location of the SAMs is shown in Figure 2.30. There are 1078 SAMs in the catchment, of which 109 are at risk of flooding, including, St Ives Bridge, Alconbury Bridge, West Acre Priory, remains of Elstow Manor House, and the Roman site at Olney.

Many of the towns and villages within the catchment owe their distinctive character to the streets and buildings within them. In addition, many town centres in the catchment contain listed buildings and Conservation Areas, for example Barton-Le-Cley, Toddington, and Leighton Buzzard Conservation Areas. Any changes to either the water table or water quality may impact upon the preservation of both buried archaeological deposits, and buildings and structures above the ground. Drying of the ground may damage buried organic deposits, while flooding can Alconbury Bridge lead to extensive damage to the structure of existing buildings. In general, archaeology is best preserved by maintaining it in either constant wet or constant dry conditions.

Much of the built environment within the Great Ouse catchment is also considered to be of exceptional quality, from the historic cores of the major towns and cities, to the medieval market towns and the many attractive and historic villages.

2.9 Communities and the local economy

The Great Ouse catchment is predominantly a rural community with below average population densities. For example East Anglia (covering Cambridgeshire, Norfolk and Suffolk) has the lowest population density of all the English regions. The majority of the population live in the smaller towns, villages and hamlets scattered across the catchment with the rest of the population (40% in East Anglia) living in the cities and larger towns (e.g. Cambridge, Bury St Edmunds, Milton Keynes, Bedford, King’s Lynn and Huntingdon). Milton Keynes is the largest town in the catchment and has the highest population, though due to the rural nature of the Great Ouse catchment, this represents only 14% of the total catchment population. Table 2.11 below shows the population distribution within the catchment.

Table 2.11 Population distribution within the catchment

Population 2001 Location % (Local Authorities) Milton Keynes (Local Authority) 207,000 14% Bedford (Local Authority) 148,000 10% Kings Lynn and West Norfolk (Local Authority) 135,000 9% Huntingdon (Local Authority) 157,000 10% Cambridge (Local Authority) 109,000 7% Bury St. Edmunds (Parish) 98,000 6% Leighton Buzzard (Parish) 32,000 2% Hitchin (Parish) 30,000 2% Thetford Parish) 22,000 1% March (Parish) 19,000 1% Newport Pagnell (Parish) 15,000 1% Other towns and villages 563,000 37% Total 1,521,000 100%

Environment Agency 60 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Outside the main towns and cities, the population densities drop significantly, particularly in the more remote rural areas. These areas are often far from most services and facilities, and those local services that exist are often poor. But, in many respects, the quality of life is high: there is less congestion, less pollution and less crime than other regions. Being a largely rural catchment, agriculture has always been important to the region. Although employment in the industry has fallen significantly, it remains important to the economy and for its impact on the countryside, especially within the intensively farmed Fens region.

Economic growth rates have been high in the catchment but uneven. The decline in employment in agriculture and traditional manufacturing industries, structural changes to employment patterns and limited inward investment have all had a major impact on the economy of the more isolated north and east of the catchment (exacerbated by poor transport links from east to west). Increasing and more stable industries across the rest of the catchment include research and technology industry (focused around Cambridge), manufacturing, ports (Wisbech and King’s Lynn), business, finance, service and tourism.

Alongside economic growth rates, population growth has also been high, largely fuelled by inward migration to the area. This increasing population has led to increased housing demand, which in turn, has put pressure on water supply, especially as the catchment contains some of the driest parts of the country (East Anglia is the driest). Table 2.12 shows some key community indicators for the Local Authorities in the Great Ouse catchment, derived from the 2001 census data (see www.statistics.gov.uk/census2001). Note that these numbers are valid for the total areas of the Local Authorities.

Table 2.12: Community statistics

Kings Lynn East Milton Hunting- Forest Parameter England Bedford Cambridge and West Cambridg Keynes don Heath Norfolk eshire North Easter Bedford Bedford Southern West Bedford The Hydrological Unit N/A n Ouse Ouse Rivers Norfolk Ouse Fens Rivers Rivers No. of residents 207,05 147,91 49,138 108,863 135,345 156,954 55,510 73,214 (x1,000) 7 1 % Unemployment (people aged 16- 3.4 2.97 3.13 2.28 2.57 2.01 2.20 2.21 74) % Households 23.9 16.0 21.9 31.8 18.5 14.2 17.1 14.8 without a car % Elderly People (65 and over) 16.0 10.28 14.86 13.19 21.32 12.94 14.90 16.41 % People with Limiting Long- 18.2 14.06 15.59 13.73 20.41 13.55 14.45 15.17 term illness General Health 9.2 7.11 7.31 6.41 9.61 6.26 6.81 7.06 ‘Not Good’ Indices of Deprivation: Rank * 204 167 218 150 291 275 282 of Average Score (2004) * Community deprivations varies across England -based on a rank scale from 1 to 354 (a score of 1 indicates the highest level of deprivation

Environment Agency 61 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 We have selected the characteristics in Table 2.12 because they form part of the Social Flood Vulnerability Index (SFVI), a standardised measure that we use to assess the vulnerability of communities to flooding. The value of the SFVI can range from 1 to 5, where 4 and 5 represent the most vulnerable. The majority of the Great Ouse catchment has a low SFVI value of 2 or 3. See 3.3.1 for more detailed information, focused on the areas at risk of flooding.

Environment Agency 62 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 2.30 Scheduled Ancient Monument sites

Environment Agency 63 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 3 Current flood risks and management

In this section we assess the nature and location of flood risk to people, property and the environment in the Great Ouse catchment, and how we currently manage these risks. Flood risk is a combination of two components: the likelihood (or probability) of a particular flood event and the impact (or consequence) that the event would cause if it happened. We have described the causes of flooding and their potential impacts in economic, social and environmental terms.

3.1 History of flooding

Some of the notable widespread flood events in the catchment are:

• 1929 – Heavy rainfall in May 1929 caused significant flooding in Cambridge, and substantial damage in High Wycombe. • 1946 - River Linnett overflowed its banks in July 1946 after heavy rainfall, causing flooding in Bury St. Edmunds. • 1947 – Widespread fluvial flooding across the catchment was caused by a combination of rapid snowmelt, heavy rainfall and lack of channel maintenance. • 1953 – Extreme meteorological conditions resulted in a North Sea tidal surge, which led to significant coastal flooding. It also caused breaching of the tidal river flood embankments between King’s Lynn and Downham Market. • 1968 – After heavy rainfall in early July, this event affected the Bedford Ouse catchment; this was followed by more heavy rainfall in the Ely Ouse catchment in September, causing problems in the Thetford area, Bury St. Edmunds and Newmarket. • 1978 – In January 1978 a tide level of 5.94m ODN, the highest on record, was reached at King’s Lynn. The effect was widespread damage with many properties flooded. This subsequently led to major improvements to the King’s Lynn defences, completed in 1991. • 1987/1988 – There was a succession of flood events in 1987/1988, with high rainfall intensity occurring in August 1987, October 1987 and January 1988. A combination of saturated soil and high rainfall contributed to flooding occurring over the whole catchment. • 1992 – Heavy rain following a long dry period overwhelmed the River Ouzel, and caused severe flooding in Newport Pagnell and Leighton Buzzard. • 1993 - Flooding from ordinary watercourses resulted in 26 properties on Maple Drive, Shefford being affected; probably the worst recorded instance of non Main River flooding in Mid Bedfordshire District Council. • 1998 – The Easter event affected most of the Anglian Region due to saturated soils over the catchment followed by heavy rainfall. • 2001 – Heavy rainfall in October 2001 caused severe flooding in both Cambridgeshire and Essex. • 2003 – This most recent flood event was caused by prolonged rainfall and saturated soil. After a wetter than average last three months in 2002, the soil in the Anglian Region was heavily saturated and the rivers base flows were relatively high. High and prolonged rainfall followed in December 2002 and early January 2003 resulting in some 200 properties flooding over the Great Ouse catchment. • 2003 - There were many instances of flooding from ordinary watercourses, surface run off and the overloading of foul and surface water drainage systems during the January 2003 event, the most significant of which occurred in Pilgrim Close, Harlington, where 6 properties suffered from internal flooding. • Groundwater flooding has also been recorded in various areas in 1969, 1979, 1987-1988 and 2001.

Environment Agency 64 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 The list illustrates that flooding within the Great Ouse catchment is mainly associated with high rainfall for extended periods of time, sometimes in combination with snowmelt. In addition, the Great Ouse catchment has suffered from tidal flooding, most notably in the King’s Lynn area, such as the events in 1953 and 1978. Groundwater has also been noted as a major source of flooding throughout the catchment more recently. Flooding from ordinary watercourses, surface run off and the overloading of foul and surface water drainage systems is less well documented than flooding from Main Rivers. However, we are aware that these events can cause considerable damage and distress in many locations.

Throughout the last decades, flood defences throughout the Great Ouse catchment have been raised and strengthened in response to events. Examples are the works following the 1953 major tidal event, when flood defence improvements were made at King’s Lynn. Flood protection throughout the Fenland has also been significantly improved, to reduce the likelihood that these low-lying areas would get flooded to a depth of 2m. The construction of flood relief channels, raised embankments, and implementation of sluices enable controlled discharge of flood waters from the Fenland. The major floods of 1953 also resulted in the creation of the National Storm Tide forecasting Service, which today is known as the Storm Tide Forecasting Service (STFS) operated by the Met Office.

Our approach to dealing with floods has changed in recent years as we recognise it is not sustainable to try to prevent all flooding. Through flood risk management, we can reduce the probability of flooding from rivers and sea by managing the land, river systems, and flood and coastal defences. We also work to reduce the damage floods can do through effective land use planning, flood forecasting and flood warning.

3.2 Sources and probability of flooding

3.2.1 How floods arise in the catchment

History shows that there are many possible sources of flooding in the Great Ouse catchment. CFMPs seek to identify and understand all sources of flood risk in order to enable effective flood risk management. Flooding in the catchment could arise from the following sources:

• Fluvial; • Tidal; • Surface water; • Sewer; and • Groundwater.

Any, or a combination, of these sources can lead to increased flood risk, however, certain sources are more prevalent across the Great Ouse catchment.

Flooding in the catchment generally results from overtopping, or in some cases failure, of flood defences. In particular, the flat topography and raised watercourses of the Fens, could lead to significant flooding following embankment failure.

Rainfall running over land and into the river network dominates fluvial flooding in the catchment, particular during the winter months, as a result of prolonged wet weather and saturated ground. Flooding resulting from high groundwater is much less common but certain areas of the catchment are susceptible, particularly within settlements on the eastern side of the Great Ouse catchment including Bury St Edmunds and Ixworth. Tidal flooding affects a small portion of the catchment in areas where either tidal, or a combination of tidal and fluvial sources can lead to flood events. Discharges from sewage treatment works do impact river base flows and can contribute to flood flows during prolonged rainfall events. Licensed abstractions, such as water supply, do not have a material effect on flood flows.

Environment Agency 65 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 We publish a Flood Map which shows areas of land prone to flooding from rivers or the sea (www.environment-agency.gov.uk/subjects/flood). The map is based on flood zones which are defined in the Governments Planning Policy Statement 25 (PPS25) as follows:

• Zone 1: little or no risk with an annual probability of flooding from rivers and the sea of less than 0.1%;

• Zone 2: low to medium risk with an annual probability of flooding of 0.1 to 1.0% from rivers and 0.1 to 0.5% from the sea (termed “extreme flood area” in the Environment Agency’s Flood Map); and

• Zone 3: high risk with an annual probability of flooding of 1.0% or greater from rivers and 0.5% or greater from the sea (termed “without defences flood area” on the Environment Agency’s Flood Map).

The existing Flood Map for the Great Ouse catchment is shown on Figure 3.1. The Flood Map represents the extent of flooding if flood defences were removed.

The sources of flooding in the Great Ouse catchment are detailed in the following sections.

3.2.2 River flooding

The dominant flood season for the Great Ouse catchment is winter (October to March), when prolonged rainfall results in saturated ground conditions. Further rainfall cannot easily be absorbed into the ground and instead runs off the land directly into rivers. Where rivers have a limited capacity, this can result in overtopping of the banks and water spilling out onto the floodplain causing flooding. Whilst this is the common flood situation, there have been instances in the summer months when, even though ground conditions are generally dry, intensive rainstorms, often over short periods of time, result in flash flood events that overwhelm channel capacity as river levels rise and fall rapidly. Example instances have been on the River Lark in July 1968, resulting in flooding at Bury St Edmunds; and on the River Ouzel in September 1992, giving notable flooding at Newport Pagnell and Leighton Buzzard.

The very nature of the low gradients in the Great Ouse Catchment, means that many rivers are very sensitive to sedimentation. A significant amount of sediment supplied from the upper catchment and agricultural land can result in rivers becoming silted-up, which reduces their capacity, and may cause more frequent flooding. Sedimentation resulting from tidal processes is also a problem in the Fenland area, once again reducing the channels’ ability to hold water. Sedimentation problems are discussed in more detail in Section 2.4.

In-channel structures, such as bridges and culverts, can also contribute to localised flooding, as they cause water to back-up and overtop river banks, or become blocked due to high sediment or debris loads. Rapid flood events can also occur if a flood defence or drainage structure should fail. The collapse of an earth embankment, either due to pressure of water or through seepage weakening the structure, can cause areas behind that defence to become flooded very quickly. Many of the watercourses downstream of Earith have raised earth embankments, and failure of these would result in rapid flooding of the land adjacent to that watercourse. Furthermore, numerous IDB watercourses throughout the Great Ouse catchment are not embanked and therefore failure of their defence system, such as pumps, would cause flooding.

Potential flood extents in areas of greatest flood risk (identified using our Flood Map) are shown in Figures 3.2 - 3.12. The flood maps show that flood risk is greatest in settlements where properties have been built along the watercourse, with many places experiencing development on both sides of the river. An overview of typical flood development in the Bedford Ouse, the Ely Ouse and the Norfolk Rivers is included in Section 2.7.

We have calculated flood depths for main settlements in the Great Ouse catchment using broad-scale computer modelling. We discuss these results in Section 3.3.

Environment Agency 66 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.1 Flood Map for the Great Ouse catchment

Environment Agency 67 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.2 Flood Zone mapping for Bury St Edmunds and Thetford

Bury St Edmunds

Thetford

Environment Agency 68 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.3 Flood Zone mapping for Bedford and Alconbury/Alconbury Weston

Bedford

Alconbury/Alconbury Weston

Environment Agency 69 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.4 Flood Zone mapping for Towcester, Biggleswade, Beeston, Sandy and Blunham

Towcester

Biggleswade, Beeston, Sandy and Blunham

Environment Agency 70 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.5 Flood Zone mapping for Newport Pagnell and Hemingford Grey, Needingworth and St Ives Newport Pagnell

Hemingford Grey, Needingworth and St. Ives

Environment Agency 71 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.6 Flood Zone mapping for Huntingdon and Godmanchester, and Swavesey

Huntingdon and Godmanchester

Swavesey

Environment Agency 72 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.7 Flood Zone mapping for St Neots and Eaton Socon, and Offord Darcy and Offord Cluny St Neots and Eaton Socon

Offord Darcy and Offord Cluny

Environment Agency 73 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.8 Flood Zone mapping for Henlow and Clophill

Henlow

Clophill

Environment Agency 74 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.9 Flood Zone mapping for Fenny Stratford and Letchworth

Fenny Stratford

Letchworth

Environment Agency 75 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.10 Flood Zone mapping for Olney and Stotfold

Olney

Stotfold

Environment Agency 76 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.11 Flood Zone mapping for King’s Lynn and Great Chesterford

King’s Lynn

Great Chesterford

Environment Agency 77 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.12 Flood Zone mapping for Sawston and Mildenhall

Sawston

Mildenhall

Environment Agency 78 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 3.2.3 Tidal flooding

The Wash SMP deals with issues of coastal protection and tidal inundation, and there are estuary strategies that cover all risks influenced by tidal processes within or around The Wash. In this CFMP we are considering tidal risk that is not covered by the SMP or by estuary strategies and the influences of the tides on the fluvial system (i.e. tide locking), which may affect the drainage of the whole catchment.

The tidal range in The Wash during spring tides is about 6m, falling to approximately 3m during neaps. This is the highest tidal range that occurs on the east coast of England, which can be further increased by storm surges. King's Lynn was affected by a surge residual (an increase caused by the surge) of up to 2m during the 1953 floods. The tidal limit on the River Great Ouse is Brownshill, just upstream of Earith, although the river as far upstream as St Ives is still affected by the tide. The tide has an effect both on drainage into the Great Ouse from certain tributaries, and on the deposition of silt along the river. Further information on the siltation problem is included in Section 2.4.

Some tributaries drain into the main rivers by gravity alone, whilst others require pumps to overcome the difference in levels. The gravity drain outfalls affected by the tide include:

• Heacham River (gravity discharge through the sea defences); • Ingol River; • Babingly Brook outfall; • Mill Fleet; • Nar Outfall (gravity with automated penstock to prevent tidal inundation); • Flood Relief Channel; • West Lynn Drain; • Billy Kirkham Sluice; • Ely Ouse at Denver Sluice; • Ouse Washes at the John Martin Sluice; • Mepal Outfall; and • Old Bedford Sluice.

A high tide can prevent rivers from discharging into the sea, a process known as tide locking. This problem is increased when a high tide coincides with high river flows, causing river and streams to ‘back-up’. The Ely Ouse lodes are man-made watercourses that drain the chalk uplands. They flow north-west across low-lying fenland into the River Cam and the Ely Ouse, but do not contribute to the drainage of this area because the banks are higher than the surrounding fenland. The lodes’ discharge is normally by gravity to the main rivers, but when high water levels in the main rivers prevent gravity discharge, the lodes’ discharge is pumped. Failure of the pumps may result in flooding of the drained areas.

Areas directly subject to the effects of the tide are indicated on Figure 3.13. Tide levels derived from Admiralty Tide Tables (ATT, 2006) and the Extreme Tide Levels for use in Anglian Region (Posford Duvivier, 1999) are indicated in Table 3.1 below.

Table 3.1 Tide levels

Mean High Water Peak level due to 200 year Extreme Tide Tide Levels Springs MHWS tides (recorded) mODN mODN mODN Hunstanton 3.65 Not known 5.88 King’s Lynn 3.77 5.94 6.07 Tail Sluice - - 6.12 Denver - 4.58* 5.77 Earith - 4.11* 3.60 *These values include a considerable element due to the river flow from upstream.

Environment Agency 79 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 The existing Flood Map is shown in Figure 3.1. Tidal flooding is a risk at Hunstanton, Heacham and King’s Lynn, with Hunstanton and Heacham being mostly affected by tidal flooding and King’s Lynn by a combination of river and tidal influence. As part of the Great Ouse CFMP we have carried out a broad assessment of the impact of tide locking on the high rivers flows and the ability to drain into the sea.

3.2.4 Surface water and sewer flooding

Overflowing surface water drains can lead to flooding, either due to under capacity of drainage or failure of a drainage system, such as blocked pipes, mechanical breakdown or operational errors. Gravity drained systems can back up due to an inability to flow into the river because of high river levels occurring in the receiving watercourse. Individually these impacts usually have little consequence for the wider catchment, however, due to their widespread occurrence these impacts cannot be ignored. The problem is exacerbated because many of the older surface water drainage systems were designed with a lower standard of protection than is in force today. However, even the present day standards are generally lower than those required for protection against fluvial flooding.

In some urban areas, surface water (rainwater) and foul sewage is drained by a single sewer pipe. This is known as a combined sewer. Combined sewers often do not have the capacity to convey all flows during a significant event, therefore excess flows are discharged into adjacent watercourses via combined sewer overflows. Furthermore, during high flow events, excess flood water can flow out of the combined sewer system at manholes and flood roads and houses in the vicinity. Locations where combined sewers pose a flood risk to the Great Ouse CFMP area have not been identified. Recent developments now implement separate foul and surface water systems, and therefore they have a higher capacity compared to the old combined systems. However, even the separate systems have a limited capacity as they are generally designed to 1 in 30 year standard (3.3% AEP).

Under the planning process we advise the Local Planning Authorities (LPA), where appropriate, to ensure that new developments propose adequate surface water disposal. For large or sensitive sites a flood risk assessment or drainage strategy may be requested to ensure surface water is appropriately controlled.

Sustainable drainage systems (SuDS) aim to control surface water from runoff, in a way that mimics the runoff regime before the site was developed. This should ensure a reduction in runoff rates from the newly developed land. SuDS also aim to help control pollution from surface water through the filtering of silts and pollutants from the runoff e.g. runoff flowing over a grassed buffer strip before entering a watercourse. Ownership and maintenance of SuDS within new developments is essential to ensure long-term sustainability. However, this process is not always straightforward due to current limitations on the adoption and maintenance responsibilities associated with SuDS; there is a national SuDS working group who are looking into this.

Some examples of the places where we believe that surface water drainage issues are at a scale relevant to the CFMP are summarised below: a) The largest single location is Milton Keynes. In developing the new city of Milton Keynes a strategic surface water drainage system was put in place. This system uses purpose built flood balancing lakes to lessen storm water run-off before discharging to the Rivers Ouzel and Great Ouse. The original design intent was to restrict the peak discharge of the Main River to a rate equivalent to the pre-development discharge up to the 1947 flood event. The balancing lakes serve as storage areas to compensate for the floodplain lost under the Milton Keynes development. About 80% of the lakes’ capacity is provided for this function, with 20% being for reduction of local run-off. Drainage strategy studies in 2000 and 2003 have shown that the strategic flood mitigation should be effective in controlling flood risk up to a 1% annual probability standard (1:100 yr return period) even allowing for planned development to 2011. b) Surface drainage is also a concern for existing and prospective development in the Ouzel catchment and Marston Vale. In both of these locations, the Bedford Group of Drainage Boards, with others, have created a drainage strategy. The strategy permits individual developments to proceed with drainage flows then managed by the Drainage Boards’ systems.

Environment Agency 80 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 c) There are concerns that the River Hiz does not have the capacity to receive surface water from Hitchin, however no specific information has been provided to support this statement. d) Surface water in Cambourne (west of Cambridge) discharges into Bourn Brook, which has a history of flooding. However, through the planning process, measures have been put in place to ensure that Cambourne will not exacerbate the flooding of Bourn Brook. In particular, surface water balancing lakes (acting in a similar manner to those described above for Milton Keynes) were built to cater for a 1 in 200 year (0.5% AEP) storm event. e) King’s Lynn (including West Lynn) is an expanding urban area; surface water drainage from development is an issue for the receiving watercourses. The King’s Lynn Consortium of Drainage Boards has been active in managing improvements to the local drainage, by installing and maintaining pumping stations to discharge water during high flow events. f) In low lying areas the Internal Drainage Boards operate in such a way as to control water levels within their districts to provide irrigation and reduce flooding. This is achieved through a combination of controlled discharge to the main rivers and flow storage within the system of drains. The drainage districts are illustrated on Figure 2.3.

Flooding within the IDB areas is generally caused by high rainfall and low soil moisture deficit. The fenland drainage districts are also constrained by the rate at which water can be discharged into the Main Rivers (by gravity or pumping), and the flood storage capacity of the drainage area. Large areas of the fens can become waterlogged, resulting in standing water covering the fields. Consequently, flooding will occur if the outfall of the drainage area, or its capacity, cannot cope with the amount of water during a flood event. Many of the rivers that cross the Fens are higher than the surrounding ground level, therefore embankment failure will result in flooding.

A number of IDBs are currently undertaking, or have recently undertaken, hydrological studies and strategic reviews of their catchments. These studies consider climate change effects and potential improvements to the drainage systems, to inform the decision making process to achieve a standard of protection against a 1 in 100 year (1% AEP) flood event. An example is the strategic review undertaken by the Middle Level Commissioners which was completed in 2004. The study identified a number of deficiencies; one of which is resulting in the replacement of St Germans pumping station.

At a catchment scale surface water tends to pond in low spots, which is made worse by elevated drains, roads and railways which can divide the floodplain into compartments restricting flood flows in some areas. Table 3.6 shows the main roads and railways which are at risk of flooding and potentially dividing the floodplain.

3.2.5 Groundwater flooding

Flooding can also result from high groundwater levels if the water table rises above the ground level. Although groundwater can add to the flow of a river, this is not thought to have a notable influence on fluvial flooding in the Great Ouse catchment, but is more likely to affect low-lying areas of land and in urban areas where there are cellars and basements. Groundwater flooding is difficult to predict as it rarely follows a consistent pattern. The response time between a rainfall event and groundwater flooding is relatively long, and as a result groundwater flooding can last from a few days to a few weeks. Following the 2001 floods, groundwater flooding was shown to have affected properties in Bury St Edmunds along Barn Lane and Eastgate Street, as well as more than 20 businesses and homes in Newmarket High Street. Several roads were affected by the groundwater flooding including Snailwell Road, parts of the A14 around Newmarket, the A143 between Great Barton and Ixworth and in Thurston near the railway station. Toddington was also affected, along with roads near Ashwell Springs. The significant feature of this groundwater flooding was that it continued for many weeks and caused major disruption to traffic.

Surface water flooding can indirectly affect the quality of groundwater, through the mobilisation of pollutants from other systems. Furthermore, flood management schemes could affect groundwater flow paths and quality.

Environment Agency 81 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.13 Tidal areas

Environment Agency 82 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 3.3 Consequences of flooding

3.3.1 Context One of the key aims of the CFMP is to assess where in the catchment flood risk is the greatest and how this might change in the future. This will then allow flood risk management policies to be targeted to those areas of greatest need. It will also serve to provide a broad framework for other decisions, for example, where new developments might best be located in order to ensure sustainable management of future flood risk.

3.3.2 Methodology

The analysis of flood risk for any particular location comprises: • The estimation of flood probability and flood extent; and • The assessment of the damages caused by flooding.

This analysis was carried out to consider the impacts of flooding to three receptors:

1. People Including loss of life, injury and personal distress. Risks relating to individuals and groups of people, especially those that are more vulnerable to flooding.

2. Property and infrastructure Including loss or damage to buildings or infrastructure and the disruption of activities that have economic value.

3. Environment Loss, damage or benefit to the river environment, habitats and species and cultural, historical and recreational environment.

People

We determined the number of people at risk of flooding by identifying the number of people living within the 1 in 100 year (1% AEP) flood extent based on the National Property dataset (2004). We assessed the likely impact of flooding on these people, including the direct and indirect effects of flooding. We also assessed the vulnerability of communities to flooding across the catchment by calculating the Social Vulnerability Index with the aid of MDSF software (detailed in this section).

Property and infrastructure

One method to estimate flood probability within the catchment would be to build a broadscale computer model to assess flood risk for different return periods. Although some models exist, these have generally been developed for particular schemes and are too detailed and localised for use as a broad scale model. Further difficulties arise due to the large scale of the catchment, the complex interaction of the Bedford Ouse, Ely Ouse system and the Norfolk Rivers (as described in Section 2.7 and 3.2.1) and the uncertainties that arise when modelling flooding over large areas of flat low lying land. We decided, therefore, that it was inappropriate to build such a model, particularly taking account of the time and cost required and the uncertainty associated with the outputs. Instead, we have established the baseline analysis (i.e. the current conditions) of flood risk using the following method.

First we established those areas where the impact would be greatest; based on a study of Flood Zone 3 (the area with an annual probability of fluvial flooding of 1.0% or greater) identifying stretches of river that have more than 25 houses per linear kilometre. This information was then fed into the Modelling and Decision Support Framework (MDSF) software, (a computer program developed specifically for CFMPs) together with details of known flood defences i.e. the location and standard of protection, in order to calculate flood risk.

Environment Agency 83 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 The MDSF analysis takes into account the extent of flooding, the depth of flooding and the type of property and land at risk. It generates three measures of risk:

• Average annual damage to property. • Average annual damage to agriculture. • Social vulnerability; an index to indicate those who are vulnerable to flooding (long-term sick, socially disadvantaged and the elderly).

The economic value of damages is expressed as Average Annual Damages (AAD) and is an estimate of damages to residential and commercial properties, as well as agricultural land, for set return periods.

We recognised that this method could seriously underestimate the damages caused in the fenland areas, as they tend to be sparsely populated, and the Flood Zone itself is less reliable due to assumptions about the performance of flood defences in these low lying areas (MDSF can underestimate damages because it takes no account of flooding when defences fail). Instead, the assessment of the risk has been undertaken based on major sub-catchments.

For the areas not in the high flood impact areas or within the fenland areas the economic damages were calculated on the area of agricultural land within the Flood Zone 3 and the damage value of this land taken from the standard tables provided with the MDSF software.

We also identified settlements which were isolated from road networks and key infrastructure during a 1 in 100 year (1% AEP) flood event, based on Flood Zone 3.

Risk to infrastructure was determined by identifying key infrastructure (major roads, railways, schools, hospitals, fire stations and police stations) located within Flood Zone 3.

Environment

Environmental risk was determined by first identifying the environmental features located within Flood Zone 3. The likely impact of flooding on these features was assessed, including the impact of modifying/altering the associated watercourse and indirect affects of flooding.

For all of this work the following assumptions and limitations should be noted:

• In the use of the National property dataset, we assumed that the population was evenly distributed across the districts which in most cases will be untrue. • For the MDSF programme, flood defences have been included where these are known and maintained by the Environment Agency as of May 2005. • Model results from previous studies have been used wherever possible. • Although non Main Rivers have been taken into account (where they have been identified as high flood impact areas using the Flood Map), their hydrology and flood levels have been obtained through the Flood Estimation Handbook (FEH) method and steady state ISIS modelling. No calibrating of the results has been undertaken. The damages and number of properties generated through MDSF should therefore be considered with care and as an indication only of the scale of the flood risk. • Using the MDSF to generate flood areas on low-lying land next to embanked rivers can underestimate damages because it takes no account of flooding when the defences fail. • For the assessment of flood risk to people, infrastructure and environmental features there was a sole reliance on these categories falling with Flood Zone 3. This does not take into account the influence of localised topographical changes. Therefore the figures can only be regarded as a rough approximation, which is suitable for the CFMP but may be insufficient for more detailed analysis. • The future flood risk may change and it is recommended to carry out more detailed studies for future more detailed strategies.

Environment Agency 84 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 3.3.3 Risks to people

Flooding can cause stress and disruption by damaging property and belongings, and by causing social disruption. In extreme cases flooding can cause injury and loss of life. Table 3.2 summarises the number of people in all high-risk areas. Note that these numbers are a rough estimate based on population data from 2004.

Disruption due to flooding depends on the duration and depth of the flood, the assets that are affected and the level of damage. In the Great Ouse catchment, we expect that the most major disruption would be caused by flooding of roads and railways in the towns and villages and possibly by disruption of a number of schools, police stations and fire stations (see section 3.3.2). The extent of stress depends on a number of factors that are difficult to measure, such as how prepared people are, the level of warning and the time since the last flood event.

Recognising that flooding can have different impacts on different groups of people, we have considered the vulnerability of people to flooding. Some people are more vulnerable to flooding than others (e.g. the sick and elderly or socially deprived communities), which leads to a greater impact on bodily harm, stress and disruption. As mentioned in Section 2.9, we can get an indication of this variability from the Social Flood Vulnerability Index (SFVI), based on relevant population characteristics at the level of census districts. The SFVI is categorised into five bands where category 1 represents very low vulnerability, category 3 - average vulnerability and category 5 - very high vulnerability. The SFVI is generated by the MDSF programme and is based on the following four social groups:

• people aged 75 and over; • people suffering from a long term illness; • lone parent households; and • financially deprived households.

The number of people, average social vulnerability, water depths and velocities are identified in Table 3.2. The approximate population at risk, vulnerability of people to flood risk, and approximate water depths have been calculated using the MDSF software.

The largest numbers of people at risk are in the Bedford Ouse and The Fens sub-catchments. High numbers are at risk in the large towns, such as Bedford and Milton Keynes, which currently rely on flood defences to reduce the risk of flooding. Most areas within the Great Ouse catchment have a SFVI of 2 to 3, so generally of average vulnerability. The places with the highest vulnerability are Letchworth, Towcester and Whaddon with a vulnerability index of 4. Figure 3.14 shows the social vulnerability of the higher impact areas.

People within settlements identified as being completely isolated (cut off from surrounding towns, key infrastructure and emergency services) during a 1 in 100 year (1% AEP) flood event are shown in Table 3.4.

Environment Agency 85 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 3.14 Social Flooding Vulnerability Index and number of properties at risk from a 1 in 100 year (1% AEP) flood event for high impact areas

Environment Agency 86 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Flooding occurs much quicker in the upper parts of the catchment where it is steeper. In the low lying areas flood duration is longer and flood depths are smaller because the water can spread across a larger area. Flooding within the Fens is contained by embankments, and should these fail there will be greater flooding with depths up to 2m. Rapid embankment failure and the associated sudden flooding can cause further disruption and stress for people living in flood risk areas.

Table 3.2 Assessment of risk to people

Approx people at High Water depth Sub Source risk (1% Impact Average SFVI range (1% Velocity of flow Catchment of Flooding AEP Area AEP) without defences)

River Lark Bury St and River 96 3 0-1.5m Edmunds Medium/low slope with narrow Linnet floodplain; indicating medium-low velocities. High speed of flooding if River Thet defences fail. Thetford and Little 177 3 0-2m Eastern Rivers Ouse Steep/medium slope in upper River Great Buckingham 155 3 0-1.5m catchment with occasional areas of Ouse wide floodplain; indicating high velocities. (e.g. River Tove). Lower Clipstone catchment has medium slope with Leighton Brook and 577 2 0-1.5m narrow floodplain; indicating high-low Buzzard River Ouzel velocities. High speed of flooding if defences fail. River Great Bedford 4649 3 0-2.5m Ouse

Alconbury/Alc Alconbury onbury 170 2 0-2m Brook Weston

Towcester River Tove 40 4 0-1.5m

Biggleswade, Beeston, River Ivel 3084 3 0-3m Sandy, Blunham

River Great Newport Bedford Ouse Ouse and 708 2 0-3m Pagnell River Ouzel

River Great Huntingdon to Ouse and 6845 3 0-3m Needingworth tributaries

Drain to St Neots and River Great 2763 2.5 0-2m Eaton Socon Ouse Offord Darcy River Great and Offord 142 3 0-3m Ouse Cluny

Drain Barton Le towards river 52 2 0-0.5m Clay Rit

Environment Agency 87 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Approx people at High Water depth Sub Source risk (1% Impact Average SFVI range (1% Velocity of flow Catchment of Flooding AEP Area AEP) without defences)

River Great Lower Ouse and Shelton and 70 3 0-2.5m Drain to Stewartby River Til

River Ivel Henlow and and Henlow 200 2.5 0-1.5m Clifton Brook

River Great Brackley 82 2 0-3m Ouse

Tributary to Bromham River Great 78 2 0-4.5m Ouse

Clophill River Flit 178 3 0-1.5m Drain to Deanshanger River Great 70 2 0-1.5m Ouse Fenny Drain to 365 3 0-1m Stratford River Ouzel

River Great Ouse and Great Barford 404 3 0-1m Steep/medium slope in upper Drain to the catchment with occasional areas of river wide floodplain; indicating high velocities. (e.g. River Tove). Lower Letchworth Pix Brook 199 4 0-0.5m catchment has medium slope with River Great narrow floodplain; indicating high-low Olney 112 2 0-2.5m Ouse velocities. High speed of flooding if defences fail. Potton River Ivel 52 2 0-2m Drain to Riseley 102 2 0-0.75m River Kym Spaldwick Drain 55 2 0-1.5m

Stotfold Drain 192 3 0-1m

Wilden South Brook 144 2 0-1.5m

Un-named Kempston 923 N/D 0-1.5m tributary

River Nar (Kings Lynn, Downham Market), River Great Ouse (Kings Lynn), Olds East Sea Kings Lynn Bank and Shallow slope with narrow floodplain; and Gaywood 8476 N/D N/D indicating medium-low velocities. High Downham River (Kings speed of flooding if defences fail. Market Lynn), Puny and Pierpoint Drains (Kings

North West Norfolk Rivers Lynn-North Runcton), Tidal (Kings Lynn-West Lynn)

Environment Agency 88 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Approx people at High Water depth Sub Source risk (1% Impact Average SFVI range (1% Velocity of flow Catchment of Flooding AEP Area AEP) without defences)

River Cam and Bin Brook Cambridge (Cambridge), and 529 3 0-1.5m Hobsons Trumpington Brook (Trumpington ) Bar Hill to Cottenham 356 3 0-1.5m Medium/low slope with narrow Westwick Lode floodplain; indicating medium- Bourn Bourn Brook 104 2 0-1.25m low velocities. High speed of flooding if Newmarket River Snail 236 3 0-0.75m defences fail. Southern Rivers Little Upper Cam Chesterford to 484 2 0-2m and Granta Little Shelford

River Lark Mildenhall and Cut-off 303 3 0-2m Channel

Total 33172 - - -

The risk of harm to people depends largely on the depth and velocity of flooding. Modelled flood depths in settlements with the greatest number of people at risk per kilometre are shown in Figures 3.15-3.25.

Environment Agency 89 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.15 Flood depths for Bury St Edmunds and Thetford

Bury St Edmunds

Thetford

Environment Agency 90 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.16 Flood depths for Bedford and Alconbury/Alconbury Weston Bedford

Alconbury and Alconbury Weston

Environment Agency 91 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.17 Flood depths for Towcester, and Biggleswade, Beeston, Sandy and Blunham

Towcester

Biggleswade, Beeston, Sandy, Blunham

Environment Agency 92 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.18 Flood depths for Newport Pagnell and Hemingford Grey, Needingworth and St. Ives

Newport Pagnell

Hemingford Grey, Needingworth and St. Ives

Environment Agency 93 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.19 Flood depths for Huntingdon and Godmanchester, and Swavesey

Huntingdon and Godmanchester

Swavesey

Environment Agency 94 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.20 Flood depths for St Neots and Eaton Socon, and Offord Darcy and Offord Cluny

St. Neots and Eaton Socon

Offord Darcy and Offord Cluny

Environment Agency 95 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.21 Flood depths for Henlow and Clophill

Henlow

Clophill

Environment Agency 96 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.22 Flood depths for Fenny Stratford and Letchworth

Fenny Stratford

Letchworth

Environment Agency 97 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.23 Flood depths for Olney and Stotfold Olney

Stotfold

Environment Agency 98 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.24 Flood depths for Great Chesterford and Sawston

Great Chesterford

Sawston

Environment Agency 99 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.25 Flood depths for Mildenhall

Mildenhall

3.3.4 Risks to property and infrastructure

Risks to property have been assessed based on the MDSF analysis for high risk areas and the current Flood Zone 3 extent for the entire Great Ouse catchment (including lower risk areas). Risks to infrastructure have been assessed based on the Flood Zone 3 extent. Both give approximate values which are suitable for a CFMP, however, further assessment will be needed for individual schemes.

Property

We have estimated that there are approximately 39,000 properties at risk of flood damage across the entire catchment, with some 17,000 properties in the ‘high risk’ areas and some 22,000 properties in the ‘lower risk’ areas (including the Fens, see Table 3.3), during a 1 in 100 year (1% AEP) flood event.

Table 3.3 shows ‘high risk’ areas, highlighted as having risks of flooding to residential, commercial and industrial properties. Figure 3.26 shows the location of the ‘high risk’ areas. These are areas where there are more than 25 houses / km length of river lying within Flood Zone 3. Damage estimates to property and agricultural land are shown separately and the effect of flood defences, where present, is also indicated. The values in Table 3.3 include the effects of both river and tidal flooding and a combination of both where applicable. The largest numbers of properties at risk lie within the Bedford Ouse part of the catchment where there are several densely populated settlements lying within the floodplain. The towns at the highest risk are in two areas with dense settlements in the floodplain: Biggleswade, Beeston, Sandy and Blunham along the River Ivel and the stretch between Huntingdon and Needingworth along the Bedford Ouse (particularly Godmanchester, Hemingford Abbotts and St. Ives).

Industrial and commercial areas around the catchment may also be at risk of flooding from other sources, including poor local drainage systems and groundwater.

Environment Agency 100 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 3.3 Average Annual Damages (AAD) for high impact areas

Note: N/D (No available data) N/A (Not applicable)

Total AAD Total AAD No. of Damages Total AAD No. of Damages Total AAD Properties (£1,000)- Damages Properties (£1,000)- Damages High Sub Source Flooded Commercial (£1,000)- Flooded @ Commercial (£1000)- Impact Catchment of Flooding @1%AEP and Agricultural 1% AEP & Agricultural Area without Residential without with Residential with defences without defences defences with defences defences defences

River Lark Bury St and River 73 228 0.9 N/D N/D N/D Edmunds Linnet

River Thet Not available Thetford and Little 134 1,216 N/A N/A N/A

Eastern Rivers through MDSF Ouse

River Great Not available Buckingham 106 140 N/A N/A N/A Ouse through MDSF

Clipstone Leighton Brook and 189 505 0.47 N/A N/A N/A Buzzard River Ouzel

River Great Bedford 2354 4,826 12 203 1,675 N/D Ouse

Alconbury/Alc Alconbury onbury 119 1,023 1,.1 N/A N/A N/A Brook Weston

Towcester River Tove 32 508 4.3 32 507 4.3

Biggleswade, Beeston, River Ivel 1733 19,376 167 817 6,150 N/D Sandy, Blunham

River Great Newport Not available Ouse and 305 890 N/D N/D N/D Pagnell through MDSF River Ouzel

River Great Huntingdon to Ouse and 4404 17,837 107 3196 13,542 91.4 Needingworth

Bedford Ouse tributaries

Drain to St Neots and River Great 1469 3,268 11 N/A N/A N/A Eaton Socon Ouse Offord Darcy River Great and Offord 63 215 5 N/A N/A N/A Ouse Cluny

Drain Barton Le towards river 36 93 0.7 N/A N/A N/A Clay Rit

River Great Lower Ouse and Shelton and 40 195 0.7 N/A N/A N/A Drain to Stewartby River Til

River Ivel Henlow and and Henlow 114 365 8.8 N/A N/A N/A Clifton Brook

River Great Brackley 36 182 1.6 N/A N/A N/A Ouse

Environment Agency 101 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Total AAD Total AAD No. of Damages Total AAD No. of Damages Total AAD Properties (£1,000)- Damages Properties (£1,000)- Damages High Sub Source Flooded Commercial (£1,000)- Flooded @ Commercial (£1000)- Impact Catchment of Flooding @1%AEP and Agricultural 1% AEP & Agricultural Area without Residential without with Residential with defences without defences defences with defences defences defences

Tributary to Bromham River Great 30 147 0.3 N/A N/A N/A Ouse

Clophill River Flit 100 1,162 9.7 N/A N/A N/A Drain to Deanshanger River Great 29 87 0.6 N/A N/A N/A Ouse Fenny Drain to 174 758 0.4 N/A N/A N/A Stratford River Ouzel

River Great Ouse and Great Barford 247 209 9.4 N/A N/A N/A Drain to the river

Letchworth Pix Brook 109 664 0 N/A N/A N/A River Great Olney 68 192 23.3 N/A N/A N/A Ouse Potton River Ivel 26 155 0 N/A N/A N/A Drain to Riseley 40 264 0.6 N/A N/A N/A River Kym Spaldwick Drain 43 119 1.2 N/A N/A N/A Stotfold Drain 95 437 0.4 N/A N/A N/A

Wilden South Brook 57 411 4.4 N/A N/A N/A

Un-named Not available Kempston 356 676 N/A N/A N/A tributary through MDSF

River Nar (Kings Lynn, Downham Market), River Great Ouse (Kings Lynn), Olds East Sea Kings Lynn Bank and and Not available Gaywood 3260 526 N/D N/D N/D Downham through MDSF River (Kings Market Lynn), Puny and Pierpoint Drains (Kings

North West Norfolk Rivers Lynn-North Runcton), Tidal (Kings Lynn-West Lynn) River Cam and Bin Brook Cambridge (Cambridge), and 341 1,712 0.8 271 955 838 Hobsons Trumpington Brook (Trumpington )

Southern Rivers Bar Hill to Cottenham 137 292 11 N/A N/A N/A Westwick Lode Bourn Bourn Brook 40 50 1.3 N/A N/A N/A

Environment Agency 102 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Total AAD Total AAD No. of Damages Total AAD No. of Damages Total AAD Properties (£1,000)- Damages Properties (£1,000)- Damages High Sub Source Flooded Commercial (£1,000)- Flooded @ Commercial (£1000)- Impact Catchment of Flooding @1%AEP and Agricultural 1% AEP & Agricultural Area without Residential without with Residential with defences without defences defences with defences defences defences

Newmarket River Snail 107 276 0.4 N/A N/A N/A

Little Upper Cam Chesterford to 232 2,296 33 N/A N/A N/A and Granta Little Shelford

River Lark Mildenhall and Cut-off 145 632 1.1 N/A N/A N/A Channel

Total 16,843 61,932 417 4,519 22,829 96.5

Note – MDSF was used for all the above areas to determine damages. However, there were several areas in which there was reasonable doubt in the MDSF results, in which case, flood extents from previous studies were used.

There are also a large number of isolated properties, and small villages within the very extensive Great Ouse catchment floodplain, which are of importance to overall flood risk in the catchment. Simple analysis of properties within our flood map identified a total of 77 settlements which were completely isolated (cut off from surrounding towns and key infrastructure) during a 1 in 100 year (1% AEP) flood event (see Table 3.4)

Table 3.4 Isolated settlements during a 1 in 100 year (1% AEP) flood event

Sub- Isolated Settlements catchment

Eastern Freckenham, Garboldisham, Hargrave, Thurston, Walsham Le Willows, and Ivy Todd Rivers

Alconbury, Alconbury Weston, Brook End, Church End, Eaton Bray, Goldington, Graveley, Hatch, Hemingford Abbots, Hemingford Grey, Houghton, Hockliffe, Bedford Leckhampstead, Moor End, Loughton, Newnham, Passenham, Shelton, Furtho, Ouse Spaldwick, Stratford, Thornborough, Upper Dean, West Head, Woolstone, Wyton, St Ives, and Welches Dam North West Norfolk Grimston, Saddlebow, West Dereham, and Wiggenhall St Germans Rivers Southern Water End, Newmarket, Histon, and Bartlow Rivers Hay Green, Green End, Ingleborough, Longstanton, Lordsbridge, Marshland St James, Nordelph, Oxlode, Pondersbridge, Prickwillow, Purls Bridge, Ramsay, Ratton Row, Shippea Hill, Wyton, Barroway Drove, Bartlow, Clenchwarton, Emneth Hungate, Gold The Fens Hill, St John’s Fen End, Stowbridge, Ten Mile Bank, Terrington St John, Terrington St Clement, Three Holes, Tilney All Saints, Tilney High End, Tilney St Lawrence, Walpole Highway, Walpole St Andrew, Walpole St Peter, West Head, West Walton, Wiggenhall St Mary

Environment Agency 103 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

The results summarised in Table 3.5 below illustrate how river flooding is the dominant source of flooding to properties.

Table 3.5 Summary table of existing flood risk to property for the high impact areas

Number of properties at risk (for an annual probability of 1% Source of flooding river and 0.5% tidal flooding) Tidal 221 Fluvial-Tidal 3,520 Fluvial 13,320 Surface Water Diffuse throughout the catchment Sewer Few known incidents Groundwater Diffuse Total 17,061

Environment Agency 104 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.26 AAD damages in high risk areas

Environment Agency 105 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Economic damages

Our estimate of the economic damages to property, in the ‘high risk’ areas and the Fens, totals £41.5m during a 1 in 100 year (1% AEP) flood event. Property damages and agricultural damages shown on Tables 3.3 and 3.6 represent losses caused by direct flood inundation of farmland and property. Economic damages are larger where there are numerous densely populated settlements lying within the floodplain, such as the sections from Biggleswade to Blunham along the River Ivel, Huntingdon to Needingworth and Bedford along the Bedford Ouse, Thetford, Cambridge and King’s Lynn, and where there are large expanses of high grade agricultural land, in particular the Fens. Economic losses can also be caused from the flooding of shops, businesses, tourist areas, and agricultural land.

Flooding has an effect on the agricultural productivity of farm land, although the effect will depend on the crop and timing of the flood. Flooding can carry fresh sediment onto the floodplain, however, it can also carry pollutants, for example sediment from nearby mineral works (e.g. Pentney Sand and Gravel Pits). High river and rainfall levels, that do not cause direct flooding, can still impede land drainage, which reduces the productivity of land.

Agricultural damages in the ‘high risk’ areas, are shown in Table 3.3, total approximately £433,000 AAD. Much of the Fens was not deemed ‘high risk’ in terms of property numbers affected/km but this is due to the diffuse nature of the settlements. A separate, more representative, assessment of the Fens was therefore carried out based on Flood Zone 3.

The Fens region covers an area of approximately 2,000km2, which represents approximately 22% of the Great Ouse catchment. The average ground level of the Fens is approximately 1.6m AOD which places them under large risk if the current flood risk management measures are insufficient or should fail. Based on this assessment there are approximately 1,150 properties at risk during a 1 in 100 year (1% AEP) flood event.

The Fens also comprise the largest area of high class agricultural land with high economic value. The total agricultural potential value of land within the Flood Zone 3 is approximately £185,995,000; this corresponds to an AAD value of some £4,650,000 (see Table 3.6).

Table 3.6 Analysis of fenland areas within Flood Zone 3

Population Property for the Agricultural Total Number of estimated whole sub potential Agricultural potential AAD Properties AAD value Settlement Area (ha) catchment flood damage potential (properties+ estimated per sub- within value AAD (£1,000) agricultural) at risk catchment Flood (£1,000) (£1,000) (£1,000) Zone3 Wisbech 19,017 19,788 157 49 17,902 447 497 Southery 15,578 997 41 13 12,603 315 328 Fens Mildenhall and Burnt 10,449 1,075 41 13 9,880 247 260 Fen Langwood 18,357 2,042 41 13 15,569 389 402 Fen Middle level 89,058 19,770 412 130 96,532 2,413 2,543 Isleham Fen 8,905 493 329 104 7,905 198 301 Hilgay Fen 6,338 1,535 24 7 7,035 176 183 Ely Littleport 8,109 833 38 12 7,057 176 188 Burwell 7,654 976 15 5 6,515 163 168 Waterbeach Brandon 282 - 0 - 33 0.9 0.9 Aldreth 3,078 - 32 10 2,419 60 71,

Environment Agency 106 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Population Property for the Agricultural Total Number of estimated whole sub potential Agricultural potential AAD Properties AAD value Settlement Area (ha) catchment flood damage potential (properties+ estimated per sub- within value AAD (£1,000) agricultural) at risk catchment Flood (£1,000) (£1,000) (£1,000) Zone3 Smithy Fen 4,091 - 11 3 2,547 64 67 Total Fens 190,917 47,509 1,141 359 185,996 4,650 5,009 Area

Total Agricultural potential AAD for the entire catchment (including high risk areas and the Fens) is £5.2m.

Infrastructure

In addition to property and agricultural land, there is a significant amount of other infrastructure at risk of flooding within the catchment. We have assessed the impacts of flooding on infrastructure during a 1 in 100 year (1% AEP) flood. Table 3.7 provides an indication of the location of key assets within Flood Zone 3. These include schools, hospitals, fire stations, and police stations along with the main transport network. Welney Causeway

Table 3.7 Infrastructure potentially at risk

Asset at Risk Location Source of Flooding A Roads A1 Sandy to Biggleswade River Ivel A1066 Thetford River Thet Fenstanton West Brook A1096 Hemingford Grey River Great Ouse Parsons nr St Ives Parsons Drove Drain A11 Mildenhall River Lark Ouse Washes Hundred Foot Washes A1101 Mildenhall River Lark Wyton River Great Ouse A1123 St Ives Un-named Drain Trumpington Hobson's Brook A1134 Cambridge River Cam Croydon Mill River and River Cam or A1198 Rhee Waddon Un-named Drain Fenstanton West Brook Girton Cottenham Lode A14 Spaldwick Ellington Brook Hemingford Grey River Great Ouse A141 Wyton River Great Ouse A142 Newmarket River Snail A149 Dersingham The Ingol A4012 Leighton Buzzard Clipstone Brook

Environment Agency 107 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Asset at Risk Location Source of Flooding A4146 Leighton Buzzard Clipstone Brook Lower Shelton Un-named Drain A421 Bedford River Great Ouse A428 Bedford River Great Ouse A43 Brackley River Great Ouse A505 Walsworth River Purwell Clifton River Ivel A507 Clophill River Flit Stotfold Un-named Drain A5134 Bedford River Great Ouse A5140 Bedford River Great Ouse A5141 Bedford River Great Ouse Barton le Clay Un-named Drain A6 Clophill River Flit Bedford River Great Ouse A600 Shefford River Flit Clifton River Ivel A6001 Biggleswade River Ivel Sandy River Ivel A603 Bedford River Great Ouse

Railways Bedford River Great Ouse Offord Cluny River Great Ouse Godmanchester River Great Ouse Walsworth River Purwell Sandy River Ivel Leighton Buzzard Clipstone Brook Meldreth River Mel Cottle End near Olney River Great Ouse Hospitals None identified at direct risk Schools/ Colleges

(number affected) 1 Bedford River Great Ouse 2 Cambridge River Cam River Thet and Un-named 1 Caston Tributaries 6 Hemingford Grey River Great Ouse 2 Huntingdon River Great Ouse 1 Letchworth Pix Brook 1 Melbourn River Mel 1 Mildenhall River Lark 1 Offord River Great Ouse 1 Olney River Great Ouse 3 St Ives Un-named Drain 1 St Neots River Great Ouse

Environment Agency 108 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 2 Wilden South Brook Police Stations Bury St Edmunds River Lark and River Linnet Hemingford Grey River Great Ouse Riseley Riseley Brook River Tove and un-named Towcester tributaries

3.3.5 Risks to the environment

Changes to the flooding regime of environmental sites can have both direct impacts (such as inundation of dry habitats) and indirect impacts (such as deterioration in water quality). The impact of flooding on the status of these sites (which can be adverse or beneficial), is site specific and dependant on the habitats, species and landforms present. This is considered in more detail in Appendix D. The implementation of policies to manage flood risk can provide an opportunity to improve and enhance the existing biodiversity and ecological assets. For example, freshwater inundation is important for maintaining certain habitats, such as fen, marsh and swamp. There are opportunities to encourage seasonal flooding in parts of the catchment, which will ensure these areas are maintained and further areas are developed.

Risks to environmental assets have been assessed based on Flood Zone 3. Sites flooded during a 1 in 100 year (1% AEP) flood event are summarised in Table 3.8. The locations of the statutory designated sites, nature conservation, and historic sites are shown on Figures 2.23 and 2.24

Table 3.8 Environmental assets at risk of flooding

Total number Total number at Total area (Ha) Feature within catchment Area (Ha) risk (1 in 100 year at risk (1 in 100 event) year event) Site of Special 242 87113 94 5444 Scentific Interest (SSSI) Special Area of 11 110592 9 1270 Conservation (SAC) Special Protection 2 64541 2 2837 Area (SPA) Ramsar site 8 65074 5 2921 County Wildlife Site (CWS) 1815 39702 601 23600 National Nature Reserve (NNR) 27 3299 9 1879 Biodiversity Action Plan (BAP) Habitats 1300 26299 300 14027 Scheduled Ancient 1078 N/D 118 N/D Monument (SAM)

Statutory designated sites

The Great Ouse catchment includes numerous international, national, and European designated sites, which fall within the area estimated to be at risk of fluvial flooding. These are illustrated on Figures 2.24 and 2.25. There are 94 SSSIs, 9 SACs, 2 SPAs, 9 NNRs and 5 Ramsar sites at risk of flooding during a 1 in 100 year flood event. Natural England has assessed all SSSIs and provide a list of activities for each that would not be normally permitted. Those SSSIs identified as particularly

Environment Agency 109 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 vulnerable to damage from watercourse modifications are highlighted in Appendix D, this includes sites such as the Ouse Washes.

Non-statutory designated sites

Of the non-designated sites within the catchment, there are 601 CWSs at risk during a 1 in 100 year flood event. Flooding may affect the habitat and lead to damage of these sites.

Important habitats and species

Habitats and species can be affected by both increases and decreases in flooding. Impacts can be direct (such as inundation of dry habitats) or indirect (such as deterioration in water quality).

The following BAP habitats and approximate areas are at risk from a 1 in 100 year (1% AEP) flood event:

• Saline Lagoons (30ha, 0.12%) • Undetermined Grassland (2693ha, 10.24%) • Undetermined Woodland (81ha, 0.32%) • Upland Hay Meadows (9ha, 0.04%) • Upland Oakwoods (134ha, 0.51%) • Wet Woodland (6901ha, 26.24%) • Lowland Meadows (4259ha, 16.20%) • Lowland Mixed Deciduous Woodland (2333ha, 8.87%) • Maritime Cliff and Slope (0.5ha, 0.001%) • Purple Moor Grass and Rush Pastures (1181ha, 4.49%) • Fens (1043ha, 3.97%) • Reedbeds (7631ha, 29.02%)

These cover 1300 sites (26,300ha) of which 300 sites (14,000ha) are at risk of flooding during a 1 in 100 year (1% AEP) flood event.

Landscape

Flooding has the potential to indirectly affect the landscape character of the catchment. The landforms of the catchment have been formed by river and tidal processes, and have subsequently been modified by man. Some vegetation forms within the landscape are affected by the pattern of flooding, for example some habitats rely on periodic inundation for their species composition. Changes to flood risk management could alter the pattern of flooding and hence, change some of the natural features within the landscape (e.g. historic parklands and estates).

Fisheries

Flood risk management can have an impact on both river and stillwater fisheries. Many of the watercourses in the upper parts of the Great Ouse catchment have a ‘flashy’ response to flooding. This has the potential to displace small fish downstream. This is a particular problem as much of this catchment is heavily modified, typically with a lack of refuge and shelter areas for fish to escape the flows. During high rainfall events increased run-off and erosion from agricultural land can be detrimental to the fishery habitat. Fertilisers and sediments being washed off the land can affect the water quality of the surrounding watercourses; and result in spawning gravels becoming smothered.

Tourism and recreation

Public footpaths and cycleways are located along the banks of many of the watercourses within the catchment, including sections of the Ouse Valley Way and Nar Valley Way. Routes on the floodplain or on top of flood defence banks may be impassable or hazardous during flood events, and may remain waterlogged for several days. This will also include riverside angling sites. It must be noted that such recreational facilities are an accepted and appropriate use for floodplain areas, with the benefits far outweighing the disadvantages. Use of watercourses for sailing, rowing or boating may

Environment Agency 110 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 also be disrupted for short periods during flood events, or for longer if structures such as moorings and locks are damaged.

Within the catchment a number of tourism and recreational sites are at risk of flooding, including historic sites (e.g. Elstow Manor House and Olney Roman Site), conservation sites (e.g. Ouse Washes and Wicken Fen), and amenity sites (e.g. playing fields, caravan and camping sites).

Surface and groundwater quality

Surface water flooding can have direct and indirect effects on surface water quality. Flooding can result in increased suspended sediment levels from run-off and erosion, and can also lead to a transfer of pollutants into surface watercourses (e.g. stored sewage effluent or oil and other liquid matter on highways). Flood management schemes could indirectly affect surface water quality through hydrological changes such as altered flow regimes and flow pathways.

Historic environment

Any changes to the water table or the water quality may impact upon the preservation of both buried archaeological deposits and above ground historical assets. A reduction in flood risk to heritage assets will reduce the likelihood of flood damage and support their long-term preservation. However, reduced flooding could lead to drier ground conditions, which may affect other buried archaeological deposits. These impacts will, however, be localised and site specific.

Table 3.9 shows the environmental and historical assets at flood risk.

3.4 Summary of flood risk

Current flood risk in each of the sub-catchments covering the Great Ouse catchment is summarised in Table 3.9. We have based our calculations on broad scale modelling developed for the CFMP and our Flood Maps.

Table 3.9 Summary of flood risk

Potential AAD for High impact areas (with the Environmental People Properties exception of Sub Isolated Infrastructure and Historical at flood at flood the Fens sub Catchment Settlements at flood risk Assets at risk risk catchment flood risk where the AADs represents all studied areas) £1,444,000 SSSIs (59) Property A roads (1) SACs (3) Eastern AAD 7,360 803 6 Police SAMs (11) Rivers £900 Stations (1) NNRs (3) Agricultural CWSs (184) AAD A roads (21) SSSIs (17) £34,031,000 Bedford 67,211 16,242 27 Railways (7) SACs (1) Property Ouse Schools / CWSs (213) AAD

Environment Agency 111 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Potential AAD for High impact areas (with the Environmental People Properties exception of Sub Isolated Infrastructure and Historical at flood at flood the Fens sub Catchment Settlements at flood risk Assets at risk risk catchment flood risk where the AADs represents all studied areas) Colleges (18) SAMs (59) £475,000 Police Agricultural Stations (3) AAD SSSIs (6) £526,000 Ramsars (1) Property North West SACs (1) A roads (1) AAD Norfolk 23,649 8,979 4 NNRs (1) £0 Rivers CWSs (77) Agricultural SAMs (13) AAD

A roads (3) SSSIs (6) £3,869,000 Railways (1) Ramsars (1) Property Southern 11,085 2,632 4 Schools / SACs (1) £47,600 Rivers Colleges (2) CWSs (55) Agricultural SAMs (5) AAD Ramsars (2) SSSIs (21) £991,000 SACs (2) Property NNRs (5) AAD The Fens 48,718 10,428 36 A- roads (1) CWSs (72) £4,650,000 SPA (1) Agricultural SAMs (23) AAD

£41,493,000 Property AAD (with defences Total 158,023 39,084 77 - - where available) £5,173,500 Agricultural AAD

Environment Agency 112 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 3.5 Existing flood risk management

3.5.1 Introduction

Our management of flood risk does not just consist of the construction of hard defences and embankments, as this is not sustainable. We also manage flood risk by issuing flood warnings, raising public awareness and the maintenance of channels and defences. We also work to prevent inappropriate development, which may cause or worsen flooding, and when development is unavoidable we advise on flood resilient designs to reduce risk to life and damages. We aim to manage flood risk in the Great Ouse catchment by working with nature wherever we can to reduce the probability of floods occurring, and to minimize impacts to people, property and the environment when floods do occur. We do this by undertaking:

• flood mapping and data management; • strategic planning and development control; • flood defence asset management; and • flood incident management.

The flood risk management policies that we develop in this CFMP will guide future studies to identify the most appropriate measures to reduce flood risk, and guide our planning of new defences that are sustainable and environmentally sensitive. The CFMP will feed into strategies for flood risk management that will incorporate development control, flood forecasting, and flood warning.

3.5.2 Flood mapping and data management

Our flood map provides details of the areas at risk from a 100-year (1% AEP) and 1000-year (0.1% AEP) flood. They indicate the areas that are at risk of flooding from rivers and the sea.

We maintain and continually update our National Flood and Coastal Defence Database (NFCDD). This database is a single and easily accessible source of all data relating to flood and coastal defences. This allows us to make better informed and targeted decisions on flood risk management needs and the measures we can adopt to address these needs.

We have used the existing NFCDD database, previous reports and local knowledge to extract information on existing flood defence assets in the Great Ouse CFMP area and the standard of protection they provide (see below).

3.5.3 Strategic planning and development control

Development on floodplains increases flood risk to people, property and the environment. Development pressure comes from national and regional targets for housing and regeneration. Flood risk is increased with increases in impervious areas, and this means that areas will respond quicker to rainfall, and there will be more flooding if sufficient measures are not put in place.

The East of England Plan - Draft revision to the Regional Spatial Strategy (RSS) for the East of England, aims to ensure that development does not take place in areas that have an unacceptable flood risk, and that development does not increase flooding elsewhere. However, the East of England Plan does permit development in flood risk areas that are sufficiently protected by defences and where there are no other suitable alternatives. The plan proposes that 60 per cent of development will occur on previously developed land, thus limiting future increases in urban run-off which would contribute to future flood risk.

We support the planning system by providing information and advice for proposed new developments in line with Planning Policy Statement 25. We also advise developers to undertake flood risk assessments for all new developments. The policies we develop in the CFMP will feed into the

Environment Agency 113 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 planning system at a regional and local level by informing the East of England Plan and Local Development Frameworks.

3.5.4 Flood defence asset management

We have permissive powers under the Water Resources Act (1991) to provide flood protection on Main Rivers within the Great Ouse catchment. We use a number of approaches to achieve this including the construction of embankments, walls, storage reservoirs, flood gates or the removal of structures such as fords or the lowering of weirs (see Figure 3.29 for location of defences). The Standard of Protection (SOP) provided by these flood defences is variable. The protection provided for Main Rivers in the catchment is shown on Table 3.10. Lock at Denver Sluice Management of flood risk is not solely carried out by ourselves; there are other operating authorities involved, including Internal Drainage Boards (IDBs) and Local Authorities (LAs). IDBs are independent bodies, created under statute to manage land drainage in areas of special drainage need. There are 54 IDBs within the Great Ouse catchment, mainly operating within the Fenland areas. Each board operates within a defined area in which they are empowered under the Land Drainage Act (1991), to undertake flood defence works on the network of watercourses and pumping stations, other than on watercourses designated as "Main".

Local authorities have powers to undertake flood defence works under the Land Drainage Act (1991), on watercourses which have not been designated as Main and which are not within IDB areas.

Table 3.10 Main River defences

Location SOP Type of defences Bedford 1 in 100 years (1% AEP) Flood walls, flood boards, and embankments Ely Ouse system 1 in 100 years Embankments Kings Lynn 1 in 200 years (0.5%AEP) tidal Flood walls, flood gates, and and 100 years river pumps Tidal Ouse system 1 in 100 years Embankments Cambridge 1 in 100 years Flood walls and Flood Boards for short section of the town Towcester 1 in 50 years Storage reservoir, embankments, and flood walls Houghton 1 in 100 years Flood walls and embankments Wyton 1 in 100 years Flood walls and embankments Swavesey 1 in 150 years (0.6% AEP) Embankments Over/Willingham 1 in 100 years Embankments Newport Pagnell 1 in 50 years (2% AEP) Flood walls and embankments Blunham to Tempsford 1 in 20 years Embankments Sandy to Blunham 1 in 10 years (10% AEP) Embankments The Hemingfords 1 in 10 years (1 in 100 years Embankments due for completion) Biggleswade 1 in 6 years (16% AEP) Embankments Stonely 1 in 50 years Flood walls and flood gates

Defences along the Tidal River Ouse include embankments and outfall structures on most of the watercourses which feed into the Tidal Ouse. The locations of river outfalls affected by the tide are shown in Figure 3.13. The outfalls comprise of a mixture of pointing doors, sluices and pumps. King’s Lynn is defended from tidal flooding by a series of flood gates, including at Alexandra dock.

Environment Agency 114 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Current and proposed flood defence improvement programmes within the Great Ouse catchment, are listed in Appendix I.

As well as river flood defence structures, we also use flood storage areas to manage flood risk. These areas can store excess floodwater that can then be released after the peak flood flow has passed. The most important flood storage areas within the Great Ouse catchment are: the Ouse Washes (sometimes known as the Hundred Foot Washes), the Ely Ouse Flood Relief System, the River Nar Flood Alleviation Scheme (FAS), the Towcester FAS, Adventurer’s Fen and the Milton Keynes storage lakes. These flood storage areas are described in more detail below:

• The Ouse Washes, an area of land between the Old and New Bedford River is used for floodwater storage during winter months and occasionally during the spring and summer, in order to protect the surrounding land from flooding. The Ouse Washes are used when flows in the Bedford Ouse exceed its channel capacity; in this instance floodwater can be diverted from the Bedford Ouse to the Ouse Washes at Earith. In certain instances high river levels can occur at the same time as high tides. These corresponding high tides and high river levels impede drainage from the low-lying watercourses flowing into The Wash. This same problem also occurs when high river levels coincide with spring tides, which even at low tide, may be too high to allow a sufficient amount of water to drain out of the Bedford Ouse system. During these periods, the washes can be utilised to store the excess water and release it once tide levels are lower than river levels.

Ouse Washes

• The Ely Ouse Flood Relief System was built to protect the South Levels from flooding. The scheme was initiated after the 1947 flood, which flooded the South Levels after the embankments on the rivers crossing this area overtopped, and was designed to accommodate a repeat flood of the 1947 magnitude. The system includes a cut-off channel, flood relief channel, and two breaching sections. The cut-off channel connects the Rivers Lark, Little Ouse and Wissey at the point where they leave the upland, and start to cross the South Level between embankments. The cut-off channel flows to the sluice complex at Denver where it discharges to the flood relief channel. The flood relief channel flows from Denver to near King’s Lynn and discharges to the tidal Great Ouse via the Tail Sluice. The flood relief channel has a large storage capacity and can store flood water that cannot be discharged because of high tides. The breaching sections are located immediately north and south of the Denver complex and allow water from the flood relief channel and cut-off channel to flood farmland owned by the Environment Agency.

• The Towcester Flood Alleviation Scheme includes a reservoir on the River Tove upstream of Towcester. The reservoir has been designed to accommodate a 1 in 50 year flood event, protecting Towcester downstream.

• The Nar Flood Alleviation Scheme is a channel which connects the River Nar to the Flood Relief Channel. The connecting channel was constructed to divert flood flows from the River Nar in order to protect the river embankments from overtopping during a 1 in 25 year flood or below.

River outfalls affected by tidal conditions are shown in Figure 3.13.

Maintaining the flood defences, rivers and channels is a fundamental part of managing the catchment. On-going maintenance, monitoring and operation are necessary to keep the river and drainage network working properly. Current ways of managing flood risk include:

• weed cutting and removing silt to keep channels clear and to allow inspections;

Environment Agency 115 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 • flushing and dredging to clear outfall channels of silt build-up; • improvement of outfall flaps, for example River Babingly Outfall; • dredging to maintain channel depths; • protecting channel sides from erosion, for example mattressing on the tidal River Ouse and Hundered Foot River; • repairing overtopped and breached embankments; • vermin control and repairs following rodent infestation in embankments; • influencing the planning process to ensure any development is sustainable; • enforcement of Land Drainage Consents to works that may affect flood risk; • sandbagging to temporarily raise defences; • maintaining pumping stations; and • telemetry.

Environment Agency Land Drainage Consent is required for any works in, over, or under a designated Main River, or any works within the Byelaw distance of a Main River or Sea Defence. In Anglian Region the Byelaw distance from a Main River is 9m measured horizontally from the top of the bank (at bankfull level) or from the landward toe of a raised defence.

Our consent is also required for any works within an ordinary watercourse, which falls outside the jurisdiction of an Internal Drainage Board. This includes all works, whether temporary or permanent, which affect the flow of an ordinary watercourse.

3.5.5 Flood forecasting and incident management

Flood forecasting and incident management is about preparing for, dealing with, and reporting on flood incidents. We work with the Met Office, local authorities and the emergency services to minimise the consequences of flood incidents when they occur.

The Great Ouse CFMP area is divided into 37 Flood Warning Areas (FWAs). Seven of these are designated as tidal flood warning areas, with the remainder being river flood warning areas. Flood warning coverage is shown on Figure 3.28, with detailed locations of FWAs shown on Figure G1 in Appendix G. Flood warning areas are described further in Appendix G. In addition there are warning areas set up so that warnings can be issued to areas at risk from breached defences.

The basis for flood warning is the measurement of rising river levels at gauging stations. These gauges are generally located upstream of the risk area. Once a rain gauge and/or a river level gauge reaches pre-set levels, catchment conditions are assessed using: soil moisture deficit data, rainfall information from radar, and monitoring of telemetry for rainfall and river responses. When catchment conditions suggest that a flood is expected, a flood warning will be issued. The locations of rain gauges and level/flow gauges are shown in Figure 3.29.

A real time catchment forecasting model has been developed for the Bedford Ouse; it is being integrated into the National Flood Forecasting System (NFFS). NFFS forms a part of the National Flood Forecasting Modelling System Strategy (NFFMSS) established by our Head Office Flood Risk Management team. We are adopting NFFS as a standard flood forecasting tool. The system comprises a generic ‘shell’; this provides the user interface and data handling tool into which the Region’s flood forecasting models are input. The NFFS receives real time data from the Regional Telemetry System (SWANTEL) and our radar system, HYRAD, and will use this data to generate forecasts of levels and flows in the Region’s rivers. The system has also been developed to receive data from the Storm Tide Forecast Service (STFS) to produce real time forecasts for specified locations along the coast.

In autumn 2007, NFFS will be adopted as the primary tool for providing river and coastal flood forecasts in the Region. Currently the majority of river flood warnings are triggered once the water in a river has reached a pre-defined threshold. By using the flood forecasting models within NFFS we will be able to generate forecasts of levels and flows at specified locations within the Region’s river network with longer lead times. Lead times can be extended further where forecast rainfall from HYRAD is used as an input to the forecasting models. Increasing lead times ensures that the public and professional partners have more time to respond to warnings and take effective action.

Environment Agency 116 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

There is a programme to develop flood forecasting models across the Region and to integrate these models within NFFS. A model for the Rivers Cam and Granta is currently under development. Warnings for the tidal flood warning areas are based on astronomical tidal levels together with surge levels.

We are the lead organisation for issuing flood warnings to the public. We send tidal and fluvial flood warning messages as Flood Warning Codes:

• Flood Watch – Flooding of low-lying land and roads is expected. Be aware, be prepared, watch out. • Flood Warning – Flooding of homes and businesses is expected. Act Now! • Severe Flood Warning – Severe flooding is expected. There is extreme danger to life and property. Act Now! • All Clear – Flood Watches and Warnings are no longer in force in this area.

For further information on flood warnings see Appendix G or contact Floodline on 0845 988 1188. We use a variety of methods to disseminate our flood warning information; we use the media to broadcast warnings and send direct warnings to professional partners and members of the public.

Floodline Warnings Direct (FWD) was introduced in February 2006 to replace the Automated Voice Messaging (AVM) system. FWD is a national system. Where the service is available, FWD allows the public and our professional partners to register for FWD and receive flood warnings direct to their telephones, mobile phones, pagers or fax machines. They can also receive them by SMS text message or by email. In addition, warnings are posted on our website, and information is provided via the call-and-listen service ‘Floodline’ and on Teletext.

We work closely with our professional partners and engage in a range of public awareness activities to ensure all organisations, and those at risk, are ready to react to flooding when it occurs.

Environment Agency 117 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.27 Flood defences

Environment Agency 118 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.28 Flood warning areas

Environment Agency 119 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 3.29 Location of level/flow gauges

Environment Agency 120 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 4 Future changes

4.1 Introduction

Conditions in the Great Ouse catchment will not remain the same over the next 100 years. The processes and drivers that influence the way floods are generated and the damage they cause will change in the future. We must begin to recognise what these changes are likely to be and how the Great Ouse catchment is likely to respond. By understanding the future problems that we may face, we can take action now to make sure that we can manage those risks in the best, most sustainable way.

In this section of the report we assess how flood risk in the Great Ouse catchment may change in the future by identifying future scenarios and assessing their impact. A scenario is a possible future situation, which can influence either catchment processes or flood responses, and therefore the success of flood risk management policies/measures. There are three key drivers which define each future scenario: land management, urban development and climate change. Initially we have identified how each of these drivers may change in the future. We have then carried out sensitivity testing for each driver separately, and in various combinations, to determine what the impacts of different changes might be and how sensitive the catchment is to these changes. We have used this understanding to determine which future scenarios to use in our assessment of future flood risk.

In line with the UK Climate Impacts Programme (UKCIP), we have considered one time period: now to 2080. This will give us two points in time at which each scenario will be tested, now and 2080. Whilst we cannot know exactly what will happen in 80 years time, we can project general trends to work out the scale of change that would affect flood risk in the catchment. Since the plan will be reviewed at 5- 6 yearly intervals, future revisions can take account of increasing knowledge with respect to climate change and any of the other drivers considered.

4.2 Future scenarios

The important factors that will define each future flood risk scenario are urban development, land use and land management, and climate change; each of these is discussed in more detail below.

4.2.1 Urban development

Urban development can have a significant impact on flood risk as it:

• Creates more hard surfaces, and this increases rapid run-off and leads to increased flash flooding; • Increases use of water, which leads to increased abstraction and increased discharge from sewage treatment works; • Increases pressure for development in the floodplain.

In order to assess future urban development within the Great Ouse catchment, we have reviewed both historic and current census data, and future development targets within Regional Spatial Strategies and Local Plans.

Historical changes

The census data have provided the following information on the population numbers in different counties within the Great Ouse catchment:

Environment Agency 121 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 4.1 Historical trends in population numbers across the Great Ouse catchment

Population per county County 1881 1921 1961 2001 Cambridgeshire 190,000 270,000 350,000 455,600 Bedfordshire 154,259 206,462 380,837 381,600 Buckinghamshire 176,323 236,171 488,233 479,000 Norfolk 444,749 504,293 651,071 796,700

Note that these population numbers concern the whole of these counties, not just the parts within the Great Ouse catchment. The table indicates that Cambridgeshire and Norfolk have seen significant population increases since 1961, while the population of Bedfordshire and Buckinghamshire has remained stable.

The census also records that the average household size has nearly halved during the past century. In 1901 the average household size was 4.6 persons while in 1991 this had reduced to approximately 2.4 persons. Based on this data, we have estimated the corresponding number of houses in each county, see the table and graph below.

Table 4.2 Historical trends in household numbers across the Great Ouse catchment

Number of houses per county County 1881 1921 1961 2001 Cambridgeshire 38,000 67,500 116,667 227,800 Bedfordshire 30,852 51,616 126,946 190,800 Buckinghamshire 35,265 59,043 162,744 239,500 Norfolk 88,950 126,073 217,024 398,350

Figure 4.1 illustrates the growth that has occurred, in terms of urban extent, over the last 120 years.

Figure 4.1 Historical trends in household numbers across the Great Ouse catchment

450000 cambridgeshire based on census 400000 bedfordshire based on census 350000 buckinghamshire based on census 300000

norfolk based on census 250000

200000 Number of houses of Number 150000

100000

50000

0 1860 1880 1900 1920 1940 1960 1980 2000 2020 years

As Figure 4.1 shows, growth has increased steadily since 1921. For Cambridgeshire and Bedfordshire, the counties almost wholly included in the catchment, the average growth rate for the period 1921 to 2001 is approximately 1,900 dwellings per year.

Environment Agency 122 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Development targets

Current and emerging regional planning policy favours the expansion of existing towns with a higher density of housing plus expansion of areas already well served by transport routes. These include Milton Keynes, Bedford, Luton-Dunstable, the M11-A14 corridor including Cambridge, and King’s Lynn.

Regional Assemblies, through the Regional Spatial Strategies, have set their own housing requirement targets for the period 2001 to 2021. For the counties within the Great Ouse catchment, Table 4.3 shows the targets.

Table 4.3 Housing targets for the Great Ouse catchment

Housing targets per county County Net additional dwellings by 2021 Reference Cambridgeshire 89,300 Draft East of England Plan Bedfordshire 120,800, including 44,900 for Milton Milton Keynes Sub-regional Keynes alone Strategy and Draft East of England Plan Buckinghamshire 108,020 Milton Keynes Sub-regional Strategy and East Midlands Strategy Norfolk 72,600 Draft East of England Plan

However, parts of these counties fall outside the Great Ouse catchment. Therefore we have assessed the housing targets based on the areas within the catchment where development continues or is planned to happen, and have also considered counties which only have a section within the CFMP area. Therefore, for the Great Ouse catchment we anticipate an estimated target of 212,450 additional dwellings for the period 2001 to 2021. This is an average of 10,622 dwellings per year.

We have used local plans and planning information to assess where in the catchment the new housing developments will be located in relation to the sub-catchments and rivers. For example, for the area around Milton Keynes, the total housing allocation has been distributed to fall within the following sub-catchments: the Great Ouse (north side of Milton Keynes), Loughton Brook, the Ouzel and Broughton Brook, including some allowance for infill to the current town.

Figure 2.13 illustrates the locations where future developments are anticipated and their scale.

The Government’s target is for new housing to be at a density of 30 dwellings per hectare, with brownfield redevelopment made a priority (60% of all new housing should be brownfield redevelopment). However, at least one ‘new’ town is planned within the Great Ouse catchment. Moreover, we have examined local plans to determine expected greenfield development. Based on expected growth rates, existing development areas and available brownfield sites, around 70% of the planned growth in the Great Ouse catchment will be greenfield development.

Resulting estimate of urban development

As well as dwellings, urban development will include business and community development. Based on past growth for urban areas, such as Milton Keynes and planned growth indicated within local plans, we have estimated that an additional 25% developed area for business and 15% developed area for community infrastructure (such as schools) should be allowed for.

Overall, therefore, we expect the urban growth within the catchment to 2021 to be:

212,450 dwellings at 30 dwellings/ha: brownfield and greenfield= 7,082 ha Greenfield/housing development: 70% of total = 4,957 ha new build Add 25% for business development = 1,239 ha new build Add 15% community development = 744 ha new build Total new build = 6,940 ha

Environment Agency 123 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

This means that a total of approximately 6,940 ha of new urban development is anticipated from the year 2001 to 2021, corresponding to a growth rate of 347 ha/yr.

For context, the total area of the catchment is 858,700 ha, and the total area of current urbanisation is approximately 58,500 ha.

Beyond 2021 we have assumed that the historic urban growth rate of 62 ha/yr, based on the figures from 1920 to 2001, will remain constant until 2080. As an illustration, this would lead to an additional 5000 ha of land being developed (0.5 % of the total catchment area), up to 2080.

Influence of source control

In addition, we have considered the impact of source control for new developments. As land is developed, natural drainage patterns are disrupted. In most cases development will result in an increase in the proportion of impermeable cover (roads and footpaths). Traditional drainage systems are designed to remove rainwater from these surfaces as quickly as possible. This causes higher flow rates for shorter periods of time, often resulting in flooding downstream.

Source control techniques such as porous surfaces and purpose built ponds/wetlands are designed to intercept the water as close to the source as possible. This in turn allows the quantity of water discharged directly to the river to be either minimised or controlled. This not only reduces flood risk, but can also reduce any potential impact on water quality, help to replenish underground water resources, and help maintain flows in surface watercourses during dry weather. In our sensitivity testing we have assumed new development controlled run-off to the maximum extent such that future development had no additional impact on run-off.

Scenarios

In summary, we have tested the sensitivity of two scenarios for future urban development:

• Urban growth as projected from proposed and historical developments; and • Urban growth with full source control implemented.

4.2.2 Land management

Future land management, outside of the urban areas, will depend upon society’s aspirations and needs. It will be driven by policies implemented by both the UK Government and the EU. The pressures and drivers that will affect how land is used include the following:

• Opening of world markets, making agriculture in the UK less economically viable. • Growth in world population increasing demand for food production. • Shift to other farming practices, driven by market forces. • Shift in consumer preferences. • Drive to enhance and restore environmental habitats and landscape. • Drive to reduce CO2 emissions through the use of biofuels and carbon sinks. • Fuel prices could make importing of produce uneconomic. • Common Agricultural Policy reform and future policy changes.

Potential changes to land use could have a significant impact on flood risk. Potential changes include: any future afforestation, improved agricultural drainage over large areas or intensification of agricultural practices. In the Great Ouse catchment, as a response to the pressures and drivers mentioned above, we may experience either agricultural decline or intensification of practices. In addition, it is possible that changes to farming subsidies and the increased pressure for more sustainable farming practices will lead to areas of agricultural land becoming available for other purposes, including flood storage and conservation.

We have therefore tested the sensitivity of four scenarios for future agricultural activity:

Environment Agency 124 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

• Agricultural Intensification - Increase Standard Percentage Run-off (SPR) by 15%. SPR is a hydrology parameter used to represent catchment permeability. Increasing SPR tends to increase peak flows. Also reducing time to peak (Tp) of the flood by 2 hours; • Agricultural Intensification - Increase SPR by 15% and reduce Tp by 2 hours for 25% of arable land; • Agricultural Decline - Decrease SPR by 10% and increase Tp by 2 hours. This simulates improved ‘attenuation’ of water and results in lower peak flows. • Agricultural Decline – Decrease SPR by 10% and increase Tp by 2 hours for 25% of arable land.

4.2.3 Climate change

It is accepted that climate change will affect flooding in the UK. The main changes will be in rainfall patterns and sea levels. Changes in rainfall patterns could result in changes in the intensity and frequency of storms, and the depths and duration of seasonal rainfall. Such changes will affect the way in which the catchment responds. Changes in sea level can result in changes to the drainage of watercourses into the sea and the effects of tide locking.

Current estimates of sea level changes are outlined in Table 4.4; these estimates include both the rise in sea level due to climate change and large scale land movement.

Table 4.4 Predicted sea level changes

Environment Agency Region Allowance for Sea Level Change (mm/yr) North West and North East +4 Midland, South West, and Wales +5 Anglian, Thames and Southern +6

In line with the guidance, we have considered the impact of rising sea levels on the catchment using a value of 6 mm per year. Therefore, by 2080 sea level is expected to have risen by 50cm as a best estimate.

Climate change scenarios for the Great Ouse catchment, provided by the United Kingdom Climate Impacts Programme (UKCIP), suggest drier summers and wetter winters, with a 10-30 per cent increase in winter rainfall over the period from now until 2080 (classed as the medium-high scenario). In response to this, we expect both the severity and frequency of peak river flows to increase, due to increased surface water run-off generation.

The UKCIP medium-high climate change scenario indicates a potential increase in river inflows of up to 20% by 2080. For this CFMP, we have followed the recommended approach of a 20% increase in peak river flows above the present day condition, as the worst case climate change scenario. However, because we are still uncertain about how accurate climate change predictions are, we will use an upper limit of 20% and a lower limit of 10%.

In summary, we have tested the sensitivity of three scenarios for future climate change: • Upper limit of 20% river flow increase; • Lower limit of 10% river flow increase; • Sea level rise of 6 mm per year.

4.2.4 Sensitivity testing

To understand how future changes may affect the catchment it is important to understand what the impacts of the different changes might be. We carried out two types of analysis to test the sensitivity:

Environment Agency 125 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 a correlation analysis for the impact of sea level rise and a hydrological analysis for the other possible drivers.

Impact of sea level rise

We assessed the correlation between tide levels at King’s Lynn and corresponding levels upstream in the Tidal River Great Ouse at Denver Sluice. The correlation focussed on low tides, as it is at low tide that gravity discharge to the Tidal River can take place. It was found that low tide levels at Denver Sluice are not affected by equivalent low tide at King’s Lynn. The conclusion from this correlation exercise is that prospective future sea level, giving higher low tide levels at King’s Lynn, will not raise low tide levels at Denver Sluice and this will not lead to worsening conditions for gravity drainage into the Tidal River. This means that it is not necessary to take sea level rise into account in the assessment of future flood risk for this CFMP.

Hydrological analysis

We have constructed a broadscale hydrological model of the catchment in which we have divided the Great Ouse catchment into 85 different areas (known as sub-catchments) at particular locations along the watercourses in the area. For each sub-catchment, we constructed a hydrological model based on details given in the Flood Estimation Handbook (FEH). The model determined the peak flow and run-off volume, for a range of annual flood risk probabilities, from 50% (1 in 2 year) to 0.5% (1 in 200 year).

This model assesses the impacts of changes to key measures in the catchment on flow and flood volume. The results identify how sensitive different parts of the catchment are to the individual factors.

We applied the model to the present day situation, and then for each of the possible developments for land use change, urban development and climate change.

As listed in the sections before, the key scenarios that we tested for each future change driver are: increase run-off (SPR) by 15% (agricultural intensification); • decrease run-off (SPR) by 10% (agricultural decline); • time to peak of flood (Tp) decrease by 2 hours (improved agricultural drainage); • time to peak of flood (Tp) increase by 2 hours (agricultural decline, reduced agricultural drainage); • urbanisation increase at planned growth rates (to 2020) and historic growth (2020-2080); • urbanisation increase by 0% (i.e. 100% source control on new developments); • Increase peak flows by 10% (climate change); and • Increase peak flows by 20% (climate change).

The sensitivity analysis for key sites is shown in Appendix J. The analysis shows the percentage increase in peak flows for 1 in 100 year (1% AEP) flood event, for each of the drivers. The overall picture of the results matches the expected directions of change: climate change and urban development lead to a significantly increased likelihood of flooding. The results of the sensitivity analysis also clarify that the identified possible developments can produce a wide range of results. These findings form the basis for construction of the scenarios to assess future flood risk as described in section 4.2.5.

4.2.5 Scenario construction We have combined the three drivers (urban development, land use, and climate change) to create a range of scenarios of future conditions within the Great Ouse catchment. We have used the six combined scenarios as shown in Table 4.5 for the assessment of future flood risk for the 2080 time step as described in section 4.3.

Environment Agency 126 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 4.5 Future scenarios

Scenario Urban- Urban- Agri-culture as Agri- Agri-cultural Climate Climate reasoning isation isation existing cultural Inten- Change Change with Decline sification (10%) (20%) Source Control Worst Case 9 9 9

Can agricultur e combat 9 9 9 climate change

Most Likely 9 9 9

Impact of Source 9 9 9 Control

Best Case 9 9 9

Each scenario combines a possible future development for each of the three drivers: urban development, climate change and land use change.

4.3 Assessment of future flood risk

4.3.1 Introduction

This section describes how future flood risk will affect people, property and the environment. The three drivers, outlined in Section 4.2, will inevitably affect the frequency, duration and extent of flooding over the next 80 years. Areas currently at risk of flooding will become more at risk, whilst areas currently outside of the floodplain may become vulnerable as a result of development within the floodplain. The methodology used to investigate the future response of the catchment was not as detailed as that used for the current condition of the catchment. Instead of calculating new flood extents and depths, we used simple modelling techniques to establish the change in peak river inflows, as a result of urbanisation, land use/land management changes and climate change. From these changes in flow we could then calculate the resulting (potential) damages at key locations across the catchment.

4.3.2 Future probability of flooding

This section describes the modelling results in terms of peak flow changes across the catchment, and then predicts the implications of these changes on flood risk to people, property and the environment.

Environment Agency 127 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 4.6 below summarises the impact of the future scenarios on peak flows at key locations. Full results are shown in Appendix K. Generally, an increase in calculated peak flows means that there will be an earlier onset of flooding, and that for a given event (for example the 1% AEP flood), the flood extent and flood depth will be larger.

Table 4.6 Future flood risk issues

Location Issue Rivers Lark • In the worst case scenario, calculations suggest that the peak flow and volume at Bury St and Linnet Edmunds and Mildenhall will increase by up to 25% in the long-term (up to 2080) • Agricultural intensification, if applied to all arable land, could have a significant impact (>5% increase in peak flows) on the sub-catchment of Mildenhall. • It must be noted that these rivers react slower to rainfall than the rest of the Great Ouse catchment, so the increased peak flow may not necessarily lead to increases in the extent and depth of flooding. Rivers • Agricultural decline, if applied to all arable land, would have a significant impact (>5% decrease Cam and in peak flows) on the sub-catchment of Saffron Walden. This would reduce the added risk that Granta climate change is likely to provide. • Agricultural intensification, if applied to all arable land, would have a significant impact (>5% increase in peak flows) on the sub-catchments of Cambridge and Saffron Walden • Current damage estimations are large on parts of the upper Cam and Granta, with damage increases of up to 88% expected under the worst case scenario. • The floodplain of these catchments is narrow and reacts quickly to rainfall. Therefore, the impacts of climate change, urbanisation, and future land use changes may increasingly lead to increased flood risk to people and property. Bedford • Current damage estimations are large on many parts of the Bedford Ouse, in particular the Ouse Huntingdon to Needingworth area, where damage increases by 119% under the worst case scenario. • The results show that due to the small size of the Toddington sub-catchment, there would be a 55% increase in peak flow following future urbanisation under the worst case scenario. • Agricultural intensification, if applied to all agricultural land would lead to significant increases in peak flows (>5%) to the sub catchments of Toddington, St Neots, Bedford, Buckingham, Brackley, and Broughton with increases of 22%, 7%, 7%, 11%, 14% and 15% respectively. • The existing properties at risk would be at risk more often and will potentially be flooded to a greater depth. Further properties in the areas, that are not currently at risk may be at risk under the future scenarios. Rivers • Agricultural intensification, if applied to all arable land, would lead to a significant increase in Thet and peak flow (>5%) to the sub-catchment of Thetford with increases in flow of 10%. Little Ouse River • Agricultural intensification has the most impact on sub-catchments along the River Wissey with Wissey increases in peak flow of 7% at Watton. Bury Brook • Flood risk along the Brook is currently low due to an existing adequate level of protection. However, calculations show that Ramsay and Broughton will be at higher risk under many of the future scenarios. River Flit • The results show that future urbanisation in the sub-catchments of Flitwick and Shefford would lead to increases in peak flow of 14% and 9% respectively. River Ivel • Urbanisation will result in significant increases in peak flows at Biggleswade and Sandy, with increases of 9%,and 5% respectively. This highlights the need for drainage planning in line with development (e.g. source control) which would also relieve the added effects of climate change. • This upper catchment river is very sensitive to flow changes and increases in depth and extent of flooding are likely, causing more areas, properties and people to be affected. River Ingol • Agricultural decline, if applied to all agricultural land, would lead to a reduction in flows by 14% in the sub-catchment of Dersingham, potentially limiting the effects of climate change (10% increase in flows expected for climate change scenarios). Cottenham • Locations along the Lode are not currently at high flood risk, however, the sub-catchments of Lode Cottenham and Westwick will be put at possible risk. As such, estimated damages at the sub- catchments of Cottenham and Westwick are predicted to increase by 71% and 229% respectively. Alconbury • The flashy nature of the brook already causes flooding at locations including Alconbury and Brook Alconbury Weston. At these particular locations, the worst case scenario predicts a 114% increase in estimated damages (AADs).

Environment Agency 128 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Location Issue River Tove • Towcester is currently protected by flood defences. However, further measures may be needed under the future scenarios. These estimate damage increases by 99%, in the worst case scenario. • Agricultural intensification also has the potential to increase flood risk. Increases in peak flow of 16% are predicted with the intensification of all arable land. Clipstone • Current estimated damages (AADs) will increase in two of the major sub catchments; Newport Brook and Pagnell and Leighton Buzzard, with increases of 111% and 69% respectively. River • Agricultural intensification, if applied to all agricultural land, would lead to an 11% increase in Ouzel peak flow through Leighton Buzzard. Rivers Hiz • Urbanisation, without the influence of source control, will lead to a 10% increase in peak flow at and Hitchin, thus illustrating the need to incorporate source control during development in order to Purwell minimise any future food risk, in particular the increased risk associated with climate change. Pix Brook • The results show that due to the small size of the Letchworth sub-catchment, the catchment would have a 40% increase in peak flow following future urbanisation. River Nar • The Nar downstream of Marham is embanked to King’s Lynn. However, in the past these banks have breached, along with several drains being overwhelmed, leading to flooding at King’s Lynn and the surrounding area. Under the worst case scenario there would be an estimated increase in damages of 68%, which could increase the area, properties and people affected. • Agricultural intensification, if applied to all agricultural land, would lead to an 8% increase in peak flow through King’s Lynn.

The table illustrates that in many locations, the impacts of climate change (which is the driver that causes the greatest increase to future flooding), can be partly reduced through a decline in agricultural intensification, and through the use of source control within any new urban development.

4.3.3 Future flood risk to people

The impacts on people living and working within communities at risk of flooding will become more significant as flooding becomes more frequent and prolonged and as the flood extent and flood depth increases. As development within the floodplain continues, the number of people and potential for flooding of residential, commercial and industrial property is likely to increase. This will result in more frequent flooding of areas currently at risk, in addition to properties in the floodplain which were previously not vulnerable to flooding. The increased risk could result in higher levels of stress and the potential for increased casualties will increase, particularly among vulnerable sectors of the community (see Section 3.3.1).

Table 4.7 below shows that climate change could lead to large increases in the number of people affected by flooding, in particular in the Eastern, Bedford Ouse, and Southern rivers catchments, where the number of affected people approximately doubles by 2080.

The number of settlements identified as isolated from road networks and key infrastructure, during a 1 in 100 year (1% AEP) flood event, is also likely to increase.

4.3.4 Future flood risk to property

Flood related impacts on property will become more significant in the future, if current flood risk management measures do not change. Increases in frequency, duration and depth of flooding will affect properties currently identified at flood risk. In addition, property outside the current floodplain may be at risk of flooding in the future as the extent of flooding increases. Any new developments within the floodplain will inevitably experience increased flooding.

We investigated future flood risk under the proposed future scenarios, with a focus on the ‘most likely’ scenario. Figure 4.2 shows Average Annual Damages (AADs) for the most likely scenario for 2080, compared to the present day. Table 4.8 summarises the average increase of the annualised damages within each sub-catchment and for all the scenarios from Table 4.5. All numbers are the percentage increase of the AAD. The full results for the scenario tests for all towns are shown in Appendix K.

Environment Agency 129 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 4.7 Impact of future scenarios on economic flood risk (% AAD increase per sub catchment)

Can Impact Climate agriculture Existing Worst Most of Sub Change combat Best Case AAD (100 Case Likely Source Catchment AAD climate % year) % % Control % change % % Eastern Rivers 1,551,000 69 86 64 74 69 31 Bedford Ouse 54,859,000 89 124 97 117 89 53 North West Norfolk 580,000 50 64 45 60 50 18 Southern Rivers 4,745,000 52 69 48 64 52 17 The Fens 796,000 30 56 35 47 30 4

*AAD values in the table above represent both high and low risk areas

Table 4.7 illustrates that for all sub-catchments, damages will increase significantly over the next 80 years under all scenarios. The greatest increases are within the densely populated Bedford Ouse catchment, in comparison to the less densely populated Fens catchment. Note that this does not include agricultural damages (agricultural AAD), but we know that these would also be greatly increased under the future scenarios. The impacts of climate change (which is the driver that causes the greatest increase to future flooding) can be partly reduced through a decline in agricultural intensification and through the use of source control with new urban development.

Table 4.8 shows that climate change would lead to large increases in the number of properties affected by flooding, in particular in the Eastern, Bedford Ouse, and Southern rivers catchments, where the number of affected properties approximately doubles.

Table 4.8 Impact of climate change on flood risk to people and property

Number of Number of people Properties potentially potentially Property affected by High affected by damages under Sub Source flooding in 2080 Impact flooding in 2080 the climate Catchment of Flooding (number in Area (number in change scenario brackets shows brackets shows (AAD) existing 1 in 100 existing 1 in 100 year situation) year situation)

River Lark and Bury St Edmunds 243 (96) 448 (73) 384,022 River Linnet

River Thet and Thetford 448 (177) 339 (134) 2,083,035

Eastern Rivers Little Ouse

River Great Buckingham 372 (155) 254 (106) 301,697 Ouse

Clipstone Leighton Buzzard Brook and 1385 (577) 454 (189) 745,948 River Ouzel Bedford Ouse River Great Bedford 11158 (4649) 5649.6 (2354) 3,301,837 Ouse

Environment Agency 130 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Number of Number of people Properties potentially potentially Property affected by High affected by damages under Sub Source flooding in 2080 Impact flooding in 2080 the climate Catchment of Flooding (number in Area (number in change scenario brackets shows brackets shows (AAD) existing 1 in 100 existing 1 in 100 year situation) year situation)

Alconbury/Alconbury Alconbury 289 (170) 202 (119) 1,988,353 Weston Brook

Towcester River Tove 96 (40) 77 (32) 883,401

Biggleswade, Beeston, Sandy, River Ivel 5243 (3084) 2946 (1733) 19,351,000 Blunham

River Great Newport Pagnell Ouse and 1699 (708) 732 (305) 1,705,075 River Ouzel

River Great Huntingdon to Ouse and 11637 (6845) 7487 (4404) 29,063,186 Needingworth tributaries

St Neots and Eaton Drain to River 4697 (2763) 2497 (1469) 5,610,135 Socon Great Ouse

Offord Darcy and River Great 241 (142) 107 (63) 403,380 Offord Cluny Ouse

Drain towards Barton Le Clay 125 (52) 86 (36) 149,167 river Rit

River Great Lower Shelton and Ouse and 168 (70) 96 (40) 335,031 Stewartby Drain to River Til

River Ivel and Henlow and Clifton 340 (200) 194 (114) 553,201 Henlow Brook

River Great Brackley 197 (82) 86 (36) 300,885 Ouse

Tributary to Bromham River Great 187 (78) 72 (30) 303,330 Ouse

Clophill River Flit 427 (178) 240 (100) 1,986,451 Drain to River Deanshanger 168 (70) 70 (29) 131,467 Great Ouse Drain to River 1,148,928 Fenny Stratford 621 (365) 296 (174) Ouzel

River Great Ouse and Great Barford 687 (404) 419 (247) 405,316 Drain to the river

Letchworth Pix Brook 339 (199) 185 (109) 1,099,690 River Great Olney 190 (112) 116 (68) 279,180 Ouse Potton River Ivel 88 (52) 44 (26) 217,673

Environment Agency 131 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Number of Number of people Properties potentially potentially Property affected by High affected by damages under Sub Source flooding in 2080 Impact flooding in 2080 the climate Catchment of Flooding (number in Area (number in change scenario brackets shows brackets shows (AAD) existing 1 in 100 existing 1 in 100 year situation) year situation) Drain to River Riseley 173 (102) 68 (40) 407,109 Kym Spaldwick Drain 94 (55) 73 (43) 207,941 583,111 Stotfold Drain 326 (192) 162 (95)

641,643 Wilden South Brook 245 (144) 97 (57)

Un-named 1,592,392 Kempston 2215 (923) 854 (356) tributary

River Nar (Kings Lynn, Downham Market), River Great Ouse (Kings Lynn), Olds East Sea Bank and Kings Lynn and Gaywood 804,367 9323 (8476) 3586 (3260) Downham Market River (Kings Lynn), Puny and Pierpoint Drains (Kings Lynn-North North West Norfolk Rivers Runcton), Tidal (Kings Lynn-West Lynn)

River Cam and Bin Brook Cambridge and (Cambridge), 1,580,302 819 (529) 529 (341) Trumpington Hobsons Brook (Trumpington)

Cottenham 527,346 Bar Hill to Westwick 552 (356) 212 (137) Lode 92,397 Bourn Bourn Brook 161 (104) 62 (40)

360,693 Newmarket River Snail 366 (236) 165 (107)

Southern Rivers

Little Chesterford to Upper Cam 3,382,869 750 (484) 359 (232) Little Shelford and Granta

River Lark 872,601 Mildenhall and Cut-off 470 (303) 225 (145)

Channel

Environment Agency 132 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 4.2 Chart comparing AADs across the catchment

Environment Agency 133 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 4.3.5 Future flood risk to the environment This section describes the expected future impacts on environmental receptors. Even though risk to environmental assets has not been modelled under future scenarios, we can expect increases in flooding frequency, extent, depth and duration, which will potentially increase the flood risk to the assets that we highlighted in section 3. The increased extent of flooding may also lead to additional assets being at risk of flooding.

Designated / non-designated sites and important habitats / species

The impact of flooding on designated and non-designated sites (which can be adverse or beneficial), is site specific and dependant on the habitats, species and landforms present. This is considered in more detail in Appendix D. In general terms, increased flooding/inundation associated with the future scenarios, in particular climate change, has the potential to enhance some lowland sites notified for wetland and floodplain habitats, such as the Ouse Washes. The reconnection of the riparian floodplain to the main watercourse will allow for the reworking of the river channel and also increase the extent of wetland and wet grassland habitats, thereby creating varied conditions for flora and fauna. Increased flooding could also have detrimental effects on lowland sites notified/designated for drier habitats such as woodland and/or hay meadows.

Landscape

Flooding has the potential to indirectly affect the landscape character of the catchment. Some vegetation forms within the landscape are affected by the pattern of flooding, for example, the species composition of some habitats relies on periodic inundation. Changes to flood risk management could alter the pattern of flooding and hence, change some of the natural features within the landscape. Increased flooding in the future could increase the magnitude of these indirect impacts on the landscape character due to an increased volume of water and longer periods of inundation.

Fisheries

Increased flooding could increase the magnitude of impacts on both riverine and stillwater fisheries. Climate change predictions suggest wetter winters and drier summers, with winter river inflows increasing by up to 20%. Increased rainfall, in the winter, could exacerbate detrimental effects on environmental receptors such as fisheries e.g. increased surface water run-off, leading to erosion and increased sedimentation and silt deposition. The drier summers could also affect fisheries and other environmental receptors e.g. due to low river flows and reduced water inundation.

Navigation and recreation

As the frequency and duration of flooding increases over the next 80 years, navigational and recreational facilities, including footpaths, cycle ways and bridle paths, are likely to be more affected for longer periods of time following a flood event.

Water quality

Historic environment

Any changes to the water table or the water quality may impact upon the preservation of both buried archaeological deposits and above ground historical assets. The reduction in flood risk to heritage assets will reduce the likelihood of flood damage and support their long-term preservation. However, reduced flooding could lead to drier ground conditions, which may affect other buried archaeological deposits. These impacts will, however, be localised and site specific.

Environment Agency 134 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Increases in flooding frequency, depth, duration, and associated changes to the water table may increase the magnitude of impacts upon both these buried and archaeological deposits and above ground structures.

4.4 Flood risk at key locations

4.4.1 Key communities

We expect that future developments will have the largest impact in the Bedford Ouse, Eastern Rivers and Southern Rivers. The impact in North West Norfolk and in the Fens is smaller, although still highly significant.

In the existing situation, the majority of flood risk to people and to property occurs in the Bedford Ouse sub-catchment. As illustrated in Figure 4.2, this particularly concerns three areas with dense settlements in the floodplain: the stretch from Biggleswade to Blunham along the River Ivel, the stretch from Huntingdon to Needingworth along the Bedford Ouse (particularly St. Ives, Hemingford Grey and Godmanchester) and finally St Neots and Eaton Socon. Our scenarios indicate that these will still be the areas with the highest flood risk to people and property in 2080.

In the Eastern Rivers and Southern Rivers current flood risk is relatively limited, in relation to the total area and population of the sub-catchment. The main settlements at risk are Thetford in Eastern Rivers, and Cambridge / Trumpington and Great Chesterford in Southern Rivers. Our scenarios indicate that the number of people at risk could increase by 50%, and the risk to property by even more up to 2080.

Flood risk in North West Norfolk rivers is concentrated in King’s Lynn and Downham Market. Our scenarios indicate that future development will cause a significant increase in flood risk to property, but the increase of the risk to people is limited.

Finally, flood risk in the Fens is strongly dominated by agricultural flood risk. An important impact of future scenarios could be a significant increase of the number of isolated settlements.

4.4.2 Environmental assets

The expected increased probability of flooding in 2080 can have both beneficial and adverse impacts. Particular sites where the impact can be positive are lowland sites with wetland and floodplain habitats (such as the Ouse Washes). Impacts would be negative for lowland sites with woodland and hay meadow habitats (such as St Neots Common). In addition, increased flooding could have an adverse, but very site specific impact on the preservation of historical assets.

Environment Agency 135 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 5 Catchment objectives

5.1 Introduction

The overall objective of the Great Ouse CFMP is to develop sustainable policies for the long-term management of flood risk within the catchment. This will take into account the opportunities and constraints of the catchment, along with expected future changes in flood risk due to climate change, changes in land use and land management practices, and urban development. Based on discussions with the Project Team and Steering Group, and comments made during the consultation, we have refined and reduced the draft catchment objectives and opportunities and constraints drawn up during the Scoping Stage of the CFMP process and have made them specific to the Great Ouse catchment.

This section outlines opportunities and constraints for management of flood risk within the catchment and identifies the finalised set of catchment objectives for the Great Ouse CFMP. These form the basis of the selection of flood risk management policies; see Section 6.

5.2 Catchment opportunities and constraints

The Great Ouse catchment provides many opportunities for sustainable flood risk management practices that can also deliver benefits for other functions, such as habitats, heritage, landscape and recreation. It is essential that the CFMP identifies these opportunities, on a strategic level, and takes account of them when setting objectives, appraising policies and proposing actions for future studies. There are also constraints on flood risk management in the catchment which have been identified. As CFMPs cover a broad time scale (50 to 100 years), it is important to consider that although opportunities may seem unrealistic in the short term, they could be achievable in the longer term.

We have identified opportunities from 3 sources: • Modelling to identify locations where flood storage is physically possible; • Existing policies and plans; and • Catchment understanding, using the knowledge and information from the Steering Group and wider consultees.

Opportunities for upstream storage

We believe that a key opportunity for catchment wide sustainable flood risk management is to reduce flood risk in the Fens by storing water in the upper areas of the catchment. For example, under the climate change scenario, the 100 year (1% AEP) flood in the Bedford Ouse will cause a volume of twenty thousand cubic metres of water to flow to the Fens. By storing water at several locations within the catchment, this volume of water will be spread out over a longer period, thereby reducing peak water levels. This will have a direct effect on flood risk along the downstream sections of the Great Ouse. It will also benefit the wider Fenland area, as spreading the volume of flood water over a longer period of time along with lower river levels will reduce the risk of tide locking. This will therefore reduce the risk of river water backing up and breaching embankments. The provision of upstream storage can benefit other functions (habitats, recreation, and mineral extraction) however, there are also potential constraints such as the existing use of the floodplain, legal constraints, designations and costs.

As part of this CFMP we have analysed the physical possibilities and limitations of reducing flood risk through storage. We have determined the extra volume of flood water due to climate change in the 100 year (1% AEP) flood event that would reach the Fens from the five most important rivers. Then we have carried out a geographical analysis to determine the maximum amount of storage volume that would be possible in the sub-catchments of those rivers. The required and available storage volumes are shown in Table 5.2; all of the possible storage sites that we have identified in our analysis are listed in Table 5.1; the location of these sites is shown in Figure 5.1.

Environment Agency 136 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Figure 5.1 Strategic flood storage areas

Environment Agency 137 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 5.1 Strategic storage assessment for selected rivers

Water Course Site No Storage Volume (m3) 1 894,250 2 2,658,500 3B 3,264 4 3,551,500 4B 261,120 5 996,667 5B 470,250 Great Ouse 6 3,524,320 7 510,000 9 2,241,375 10 3,001,350 1 894,250 2 2,658,500 3B 3,264 Sub Total 18,112,596 1 1,166,000 2 1,111,250 3 585,375 4 378,250 Little Ouse 5 1,968,000 6 876,000 7 249,375 8 240,000 Sub Total 7,256,750 1 769,533 2 2,371,500 3 1,188,000 Wissey 4 622,533 5 393,333 6 2,287,500 Sub Total 7,632,400 1 1,628,389 2 609,945 Lark 3 289,800 4 676,467 Sub Total 3,204,600 1 492,000 2 400,000 3 139,433 Kennet 4 352,557 5 512,000 6 642,833 Sub Total 2,538,824 0 1,267,922 1 160,050 2 327,000 3 1,078,800 4 775,500 Cam 5 1,755,000 6 911,200 7 1,195,593 8 349,707 9 418,717 Sub Total 8,239,488 Total 46,984,659

Environment Agency 138 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Table 5.2 Extra volumes due to climate change requiring storage

River Extra storage volume required Maximum available volume due to climate change (million m3) (million m3) Great Ouse 20.16 18.11 River Cam 1.95 8.24 River Lark 0.55 3.20 River Wissey 0.96 7.63 River Little Ouse 1.62 7.26 Total (reaching the Fens) 25.23 28.87

For the River Great Ouse the maximum available storage volume required is in the order of magnitude of 90%. For the tributaries the available volume is easily sufficient. This means that there is an opportunity that storage can provide a significant compensation for the effects of climate change in the Great Ouse catchment. This needs further investigation at a strategy level.

In addition to the current storage within the catchment we have identified a further 1,205 million cubic metres within the Fens which could be created to accommodate the extra volumes of water under climate change, see Table 5.3. It is recognised, however, that areas identified for future flood storage may include isolated properties, minor roads, and high grade agricultural land. Therefore, further investigation will be required at a strategy level to assess the feasibility of such measures.

Table 5.3 Strategic storage assessment for the Fens

Watercourse Site No Storage Volume (000m3) Counter drain, Ouse Washes 1 59.8 Hundred Foot Water 2 169.1 Counter drain, Ouse Washes 3 44.8 Hundred Foot Water 4 34.9 Counter drain, Ouse Washes 5 77.9 Hundred Foot Water 6 56.2 Hundred Foot Water 7 26.0 Old Bedford River 8 81.5 Hundred Foot Water 9 29.1 Bedford Ouse and Old West River 10 9.3 Bedford Ouse 11 5.3 Cut off channel and River Wissey 12 4.3 Cut off channel and River Wissey 13 4.2 River Wissey 14 18.3 River Wissey 15 46.2 River Little Ouse 16 148.9 Ely Ouse and River Litte Ouse 17 60.7 River Little Ouse 18 33.0 River Little Ouse 19 13.1 Ely Ouse 20 35.5 River Lark 21 39.4 Ely Ouse and River Lark 22 41.6 Ely Ouse 23 10.6 Ely Ouse 24 49.4 Ely Ouse 25 5.1 Soham Lode 26 28.5 Old West River and River Cam 27 31.5

Environment Agency 139 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Old West River 28 11.3 Old West River 29 2.8 Old West River 30 6.0 Old West River 31 20.4 Total 1204.7

General opportunities and constraints

General opportunities for flood risk management are listed in Table 5.4 along with other functions that could benefit and potential constraints. In addition, there are some general constraints that can be relevant for all flood risk management responses:

• legal and administrative framework; • economic viability; • availability of funding; • existing and planned functions, including development, environmental designations, navigation, industrial use and recreation; • lack of compensatory habitat; and • Impact on flood risk elsewhere in the system.

Table 5.4 Opportunities and Constraints

Non-flood risk Opportunity management function Constraints that also benefits Use opportunities from the Ouse People, society and Potential conflicts with Washes Project, such as increased communities. water level requirements storage of flood water to reduce flood The environment. for habitats. risk and benefit other functions. Property, assets and infrastructure. Use former mineral extraction sites for Mineral extraction. Existing or potential flood storage (existing mineral Property, assets and functions of flood plain extraction plans for Earith, infrastructure. (habitats, development). Cambridgeshire, Bedfordshire & Luton). Use proposed recreational Recreation. Potential use. developments such as Cambridge sport People, society and lakes and Bedford rowing lake. communities. Combine flood storage reservoirs with Water supply. water supply reservoirs. Property, assets and infrastructure. Use opportunities from ongoing Navigation Potential conflicts with navigation projects (Fens Waterway People, society and water level requirements Link, Great Ouse Waterway Plan) for communities. for habitats. flood risk management, such as improvement of water movement by desiltation, and improving access. Restoration of rivers by removing Fisheries, habitats and Existing functions of river artificial channels and flood banks to the environment. banks. create natural river channels and widen Biodiversity. the floodplain. This will create People, society and opportunities to restore lost habitats. communities. Removal of weirs to restore the natural Fisheries, Habitats and Existing functions of flow of rivers. This will also help the the environment. weirs. movement of fish throughout the river system. Use the new Milton Keynes Waterway Navigation and recreation. Recreation.

Environment Agency 140 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Non-flood risk Opportunity management function Constraints that also benefits for flood risk management, e.g. for flood People, society and Navigation. storage or improvement of conveyance communities. (flow capacity). Restoration of engineered channels in Environment and habitats. Existing development. urban areas. Make more space for rivers by removing Environment and habitats. un-sustainable defences (less likely for Maintenance costs. Upper Ouse, more likely for rural sub- catchments such as River Ivel). Make space for the rivers by moving Environment and habitats. Existing agricultural use. embankments in the Fens further back Infrastructure. from the river. Navigation. De-intensify land use (afforestation, Agriculture (through Development of reduction of drainage) to reduce run-off grants). economy. (most likely in upper parts of the Uncertainty about the catchment). effects of land use on run-off. Provide advice on opportunities for flood People, society and risk management as the Regional communities. Spatial Strategy is reviewed and The environment. updated. Property, assets and infrastructure. Advise that developments from RSS14 People, society and (the Regional Spatial Strategy for the communities. East of England) take account of The environment. sustainable flood risk management. Property, assets and infrastructure. Maximise re-use of domestic to reduce Environment pressure and runoff into drains and watercourses. Work with planning authorities to reduce People, society and Existing functions inappropriate development in the communities. Development plans. floodplain. The environment. Property, assets and infrastructure. Avoid automatic redevelopment of People, society and Development plans, existing brownfield sites in floodplain communities. brownfield development where floodplain restoration or flood The environment. targets (PPS3). storage is possible. Property, assets and infrastructure. Use large scale habitat development Habitat, environment and projects, such as Marston Vale, Wicken, recreation. and Great Fen, for flood risk People, society and management e.g. for flood storage. communities. Property, assets and infrastructure. Use developments for the 2012 Olympic Use for the Olympic Games as opportunities for flood risk People, society and Games. management e.g. development of communities. training facilities for watersport and use of existing rowing lakes for storage

Environment Agency 141 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 In addition, there are several opportunities to reduce flood risk by developing integrated flood risk management further: • Improve understanding of catchment processes, which will result in improved decision making and management. • Increase co-operation between those groups who have an interest in flood management, e.g. flood management and land drainage organisations. Information on good practice should be shared across the catchment, the area and the region, in particular with the River Nene catchment. • Develop a single register of flooding incidents across all relevant organisations. • Increase public awareness of the causes and risks of flooding.

5.3 CFMP objectives

The objectives define the goals: clear targets of delivery for the CFMP. The objectives provide the necessary framework for development and appraisal of sustainable policies (see Section 6).

During the Scoping Stage we developed draft catchment objectives based on the opportunities and constraints that we identified from existing legislation, plans, strategies, and measures already in place to manage environmental, economic and social issues. Since the Scoping Stage we have held discussions with consultees, and used comments made during the consultation period, in order to refine and reduce the draft objectives. From this work we have developed a core set of final objectives against which CFMP policies can be appraised. The main changes between the draft and final objectives is that they now reflect catchment specific objectives, indicators and targets that take into account the key components of flood risk (or receptors significantly adversely affected by flooding) as well as relevant policies, plans, and targets promoted by others (e.g WFD and BAP). The final objectives for the Great Ouse catchment are shown in Table 5.5. These objectives relate to people, property, development and regeneration, mineral abstraction, conservation, water quality and cultural heritage, and reflect the desires of various organisations for the management of flood risk in the catchment. Each objective also has a related indicator and target attached to it; these terms are defined below:

• Objective: a statement of what we want to achieve, for example to reduce flooding at a particular location, improve sustainability, etc.

• Indicator: a measure of values over time to show how we are progressing towards achieving the objective.

• Target: what we hope to achieve within a specific time.

Environment Agency 142 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Table 5.5 Objectives for the Great Ouse CFMP

OBJECTIVE SUB-OBJECTIVE INDICATORS TARGETS Reduce flood risk and optimise flooding benefits 1 Minimise Flood Damage to • Manage the risk of flooding to • Reduce the potential AAD by as much as is justified according to investment rules. People and Property (SEA people and the built (indicator a) material assets, population, environment including: • No deaths due to flooding. (indicator d) climatic factors, human a) Flood damage value over • Improved surface water drainage so current national target standards of protection are health) o Properties and industry; time achieved as appropriate to the situation (highway and urban development). (indicator a) • All flood defence systems to be in the condition required by the performance specifications. b) Number of properties in the (indicators a & e) o Key buildings and undefended floodplain • Management strategy for operation of the tidal river (Earith to Kings Lynn) and associated transportation routes. sluices, particularly in respect of silt deposition, to meet the requirements for minimum flow, c) Affected hospitals, police water level and tributary discharge, navigation and biodiversity.(indicator a) stations, fire stations, schools • Management strategy for flood contours along main rivers. (indicator b) • Avoid/minimise flood related and strategic roads • Ensure that emergency services infrastructures (hospitals, firestations, and secondary health risk. schools) remain accessible and free from flooding during an extreme flood at 0.1% annual d) Number of deaths due to probability. (indicators a & c) flooding • Maintain and improve, where • Improved flood warning. (indicator c & d)

appropriate, the standard of • Improved monitoring for flood risk management. (indicators a, b, c, d & e) defences. e) Condition of the standard of defences, particularly those • Improved flood forecasting. (indicators a, c & d) where breaching may give rapid • Increase public awareness of flood risk (indicators a, c & d) inundation 2 Manage flood risk such as to • Avoid increased flood risk f) Change in flood risk due to • No increase in flood risk. (indicator f) achieve development and due to new development. new development • Achieve growth targets for development as contained in the Regional Spatial Strategies and regeneration objectives at • Encourage development g) Availability of suitable land the Local Plans. (indicator g) Regional and Local outside the floodplain. for development • No overruling of Environment Agency objections. (indicator h) Government level without h) Planning authority • Identify where a water management strategy, linking surface water, foul water treatment detriment to existing response to Environment and discharge and water supply, is needed to cope with existing and future development. property, ensuring Agency objections to (indicator f) developments do not development on flood risk

increase flooding elsewhere, grounds and where possible reduce flooding.(SEA population) 3 Ensure that prospective • Manage impacts on mineral i) Frequency and depth of • Mineral plan not impacted upon due to flood management. (indicator i) mineral abstraction resources. flooding at existing and • Mineral extraction sites reused for flood management and biodiversity improvement possibilities are retained planned mineral extraction (SEA material assets) sites wherever possible. (indicator i)

Environment Agency 143 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 OBJECTIVE SUB-OBJECTIVE INDICATORS TARGETS 4 Optimise joint use of the • Avoid damage to current j) Evaluation of flood risk • Increase in joint use of the floodplain. (indicators j & k) floodplain and river corridor recreational facilities. management nature • Maximise access to and use of watercourses to help people’s health and well being. for flood risk management, conservation and (indicators j & k) nature conservation and • Promote tourism and recreation initiatives • Navigations use maintained or increased. (indicator k) recreation functions (SEA k) Usage of waterways for recreation associated with the human health, population, river. navigation (Frequency of fauna, flora, biodiversity, high flows preventing water) • To manage and maintain operation of navigation and navigation structures for the impacts on Air or Water benefit of the river and users. Draught

Protect and Enhance Biodiversity 5 Protect and enhance where • Creation/protection of l) Habitat connectivity in the • 50 projects completed for habitat restoration or creation. (indicators l & m) possible, the nature additional areas of nature floodplains • Desired wetland creation not inhibited by flood management. (indicators l, m & n) conservation value within the conservation value. m) Achievement of BAP • Improvement in the environmental quality of chalk streams. (indicator m) catchment (SEA flora, fauna, objectives and targets • Maintain condition of the Ouse Washes as described in 2003 and seek to improve. biodiversity, water) • Meet UK and Local n) Conservation objectives for (indicators m & n) Biodiversity Action Plan designated county, • Maintain or improve the condition of the county, national, European and internationally (BAP) objectives and targets national, European and designated environmental sites. (indicators l, m & n) for habitats and species. international environmental sites • Avoid damage to designated and non-designated wildlife

sites (county, national, European and international) and protected species.

Environment Agency 144 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 OBJECTIVE SUB-OBJECTIVE INDICATORS TARGETS 6 Maintain water quality • Achieve and or maintain o) Variation in biological and • No detrimental change in ecological status. (indicators o, p & q) standards and improve “Good Ecological Status” or • Opportunities sought to achieve “Good Ecological Status” / “Good Ecological Potential”. chemical GQA grades. where feasible (SEA flora, “Good Ecological Potential” of (indicators o & q) fauna, biodiversity, water) watercourses (EU Water p) Change in River Habitat Framework Directive). This classification. objective encompasses water q) Change in River quality which is only a part of the overall ecological status. Ecosystem grade. The definition of good will r) New measures for the vary throughout the classification system catchment as the nature of the watercourse varies. developed as a result of the WFD

Heritage and Landscape 7 Preservation of heritage – to • Avoid damage to and, where s) Number of designated or • No detrimental effects to designated sites and features. (indicator s) protect and enhance cultural appropriate, enhance the other significant sites or • Reduction in the number of historic assets adversely affected by flooding. (indicator t) heritage and landscape sites and settings of their settings adversely character (SEA Heritage designated assets. affected by flood including architectural and management proposals. archaeological heritage) • Reduce flood risk to designated sites and features t) Number of historic assets (such as Scheduled Ancient where damage currently at risk of damage, through Monuments, archaeological occurs as a result of flooding. remains, Listed Buildings, flooding. Conservation Areas, Historic Parks and Gardens, Registered Battlefields, World Heritage Sites)

Environment Agency 145 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

6 Policy appraisal

6.1 Introduction

The Great Ouse CFMP aims to identify the most sustainable flood risk management approaches for the Great Ouse catchment. This involves identifying preferred policies for the different parts of the catchment. To do this, we have divided the CFMP area into smaller areas, called policy units (see Section 6.2). Policy units are areas within the CFMP where the same flood risk management policies will be applied. For each policy unit, preferred policies are chosen from the six nationally available policies shown in Table 6.1 below:

Table 6.1 Six policy options

Policy Option Policy

No active intervention (including flood warning and maintenance), continue to monitor 1 and advise; Reduce existing flood risk management actions (accepting that flood risk will increase 2 with time); Continue with existing and alternative actions to manage flood risk at the current levels 3 (accepting that flood risk will increase over time from this baseline; Take further action to sustain the current scale of flood risk into the future (responding to 4 the potential increases in flood risk from urban development, land use change and climate change); 5 Take further action to reduce flood risk (now and/or in the future); Take action to increase the frequency of flooding to achieve benefits locally or 6 elsewhere (which may lead to an overall flood risk reduction).

The decision regarding which policy to apply to each policy unit has been guided by the Steering Group using the policy appraisal process based on the nine objectives discussed in Section 5.

We assessed which policy option/s best met the catchment objectives for the policy units. For this assessment we have:

• considered the key processes that create flooding and associated risks, now and in the future (see Sections 2 and 3); • assessed how flood risk in the Great Ouse catchment may change in the future by identifying future scenarios (land management, urban development and climate change) and assessing their impact (see Section 4); • identified suitable policy units based on flood processes and flood risks; • looked carefully at all the relevant environmental, social and economic objectives; opportunities, and constraints (including legal requirements) identified within the catchment (see Section 5); • thought about ways of managing flood risk that we could use in the catchment; • reviewed the available policy options (listed below) to identify those that are most suitable; • evaluated each of the screened policy options against the environmental, social and economic objectives within the catchment; • tested the robustness of the policies against the future scenarios.

We ensured that all information and data collected throughout the study and consultation had been considered in order to decide the policy/policies for each policy unit. Policy appraisal forms used for

Environment Agency 146 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 each policy unit are found in Appendix H, and the final appraisal decisions and findings are summarised in Section 6.2. The Policy Appraisal forms include:

• a summary sheet describing the unit, its flood risks, and proposed policy/policies including justification for each; • form PA1 for screening of policy options against appraisal objectives; and • form PA2 summarising the strengths and weaknesses for each policy option.

The appraisal objectives incorporate all parameters of the Strategic Environmental Assessment (SEA) (Directive 2001/42/EC – the ‘SEA Directive’) to take into account possible effects on the environment including; biodiversity, population, human health, fauna, flora, soil, water, air, climatic factors, material assets, cultural heritage, and landscape.

6.2 Policies for the Great Ouse catchment

The policy units, where the preferred policies will be implemented, are based on our current knowledge of flood risk and processes in the catchment including:

• drivers of future levels of flood risk; • dominant flood producing mechanisms; • position in the catchment; • type of river and floodplain topography; and • type of ‘receptor’ – economic, social or environmental.

We have selected five policy units which are:

1. Norfolk West Norfolk Rivers; 2. Eastern Rivers; 3. Southern Rivers; 4. Bedford Ouse; and 5. The Fens.

The Great Ouse catchment is split into the upper river system of the Bedford Ouse, which runs from the source down to the tidal limit at Brownshill Staunch. The tidal limit marks the beginning of the main central system, the Fens Rivers. The Fens river system receives water from not only the Bedford Ouse Rivers but also the Southern Rivers and the Eastern Rivers before finally draining out into the Wash. The final river system, the North West Norfolk Rivers, drains directly into the Wash.

Figure 6.1 shows the policy units, together with the proposed policies for each. One policy will not include all the flood risk management issues in one policy unit, therefore each policy unit requires a number of different policies to consider all its issues.

Environment Agency 147 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Figure 6.1 Policy units and proposed policies

Environment Agency 148 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

The following tables summarise the problem or risk and show the policy we have selected and the reasons why. We have also described the broad responses; opportunities and constraints; broad assessments; and risks and uncertainties for each policy unit.

Tables 6.2 North West Norfolk Rivers summary table

North West Norfolk Rivers Policy Unit 1 Includes the larger settlements of King’s Lynn and Downham Market. Problem / Risk Mainly rural catchment with significant flood risk at King’s Lynn. P2 for smaller watercourses where flood risk can be allowed to increase. Policy P5 for King’s Lynn, West Lynn, Downham Market and North Runcton. P6 should be adopted where there is the opportunity to use areas as active floodplain.

People and Property: There are approximately 23,600 people at risk of flooding in a 1% AEP; this increases to approximately 23,800 people in the future with the added influence of climate change. The damages caused by flooding in a 100 year (1% AEP) event is approximately £525,900 AAD at the high risk areas (King’s Lynn, North Runcton and Downham Market.). The amount of damages in these locations is likely to increase to approximately £870,400 AAD with the added influence of future climate change.

Environment: This unit contains extensive areas of national, international and European sites of importance which are at risk of river flooding, including 6 SSSIs, 1 Ramsar and 1 SAC. The % area of these sites likely to be inundated with flood water during a 100 year (1% AEP) flood event is highlighted in Appendix H. In the future, increased flooding could have adverse or beneficial effects depending on the habitats, species or landforms present. The area is also of high heritage and landscape interest with 13 SAMs, 1 AONB and 2 Joint Character Areas at risk during a 100 year (1% AEP) flood event. Future increases in flooding frequency, depth, duration, and associated changes to the water table may increase the magnitude upon these historic sites. The current indirect effects of flooding, which landscape designations could suffer from (e.g. changes in vegetation), are likely to increase in magnitude in the future due to the increased volume of water. A large part of the river corridor is used for angling, cycling, walking, horse riding, and boating activities Why the chosen which are currently disrupted for short periods of time during a flood event, however policy was increased frequency and duration of future flooding is likely to lengthen these periods of selected disruption.

Social: Flooding can cause stress and disruption by damaging property and belongings, and by causing social disruption. The extent of stress depends on a number of factors that are difficult to measure, such as how prepared people are, the level of warning and the time since the last flood event. Increased flooding in the future could increase these social impacts. People living within settlements at risk of becoming completely isolated during a flood event will be significantly disrupted. There are 4 settlements which become isolated during a 1 in 100 year (1% AEP) flood event including Grimston, Saddlebow, West Dereham and Wiggenhall St Germans (see Table 3.4).

Overall Assessment: The CFMP identified that further action to reduce flood risk should be taken at King’s Lynn, Downham Market and North Runcton where damages total £525,900 in a 100 year (1% AEP) event. We have adopted policy 6 where there is the opportunity to use areas as active floodplain. Policy 2 will be chosen for areas which we are currently protecting but which might no longer need to be protected, for example areas of reduced industrial or agricultural activity or areas where development has moved away from the floodplain. In these cases, we could reduce the current standard of protection, for example lowering flood defences, reducing maintenance costs etc.

Environment Agency 149 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Opportunities to improve flood risk management include: • changing land use/land management practices in order to intercept surface water run-off and reduce peak flood flows. Such changes would benefit both conservation and flood risk management; • the use of flood risk management strategies in King’s Lynn, North Runcton and Downham Market (see Section 7). These studies should identify what further actions can be taken to manage flood risk at these locations. The study will also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain; • reduce runoff from future development by application of source control such as porous surfaces and purpose built ponds/wetlands; • prevention of inappropriate development in the narrow floodplains; and • work together with Local Authorities, Anglian Water, Internal Drainage Boards and private companies to manage flood risk in an integrated manner. Policy unit-wide Opportunities & Constraints Constraints to flood risk management include: • economic viability of flood alleviation schemes and maintenance; • existing development currently at risk; • the effects of climate change; • Internationally and nationally important habitats and species; • Important heritage sites (archaeological, architectural and ancient environmental material); • rural economic activity including high quality agricultural land; • a lack of areas within the catchment for large-scale floodplain storage; • use of the rivers for navigation; and • land-use and planning policy, which presupposes redevelopment of brownfield sites in the floodplain.

• Impact of sea level rise and siltation in the Tidal Ouse which will impede drainage out to the Wash and therefore, increase flood risk within this policy unit. • The accuracy and resolution of the broad scale modelling means there is considerable uncertainty in the detail of flooding across the Great Ouse catchment. This is particularly true for catchments with vast areas of floodplain, complex local-scale drainage systems, and recent flood defences which have not been picked up by the model. • We have only provided a high level, strategic view of flood risk in the CFMP and the assessment has focussed on strategic areas affected. Where we have highlighted areas where there needs to be more work carried out to manage flood risk, a more detailed flood risk management study will assess where certain measures are practical and can be Risks, implemented. Uncertainties & • The risk from groundwater is an issue within this policy unit; however the extent of this Dependencies risk has not been defined or quantified. We are aware of a groundwater model being produced for this region; these results will be fed into subsequent strategy studies. Similarly, flood risk associated with sewers has not been clearly defined or quantified. We are aware that flooding from sewers is a widespread, diffuse and short-term problem. Therefore, there is an opportunity to improve integration of flood risk management and work with other interested parties such as Anglian Water. • There is currently some uncertainty about how effective land management and vegetation cover is in altering run-off characteristics on a large scale. It is known to work well locally, but we do not yet know its effect on the catchment as a whole, and thus how effectively land use/management changes could reduce flood risk in the policy unit.

Environment Agency 150 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 6.3 Eastern Rivers summary table

Eastern Rivers Policy Unit 2 Includes larger settlements of Thetford, Bury St Edmunds, Swaffham, Walsham-Le- Willows and Attleborough. Rural catchment with significant urban areas, including Bury St Edmunds and Thetford. Apart from flood defences in Bury St Edmunds, flood risk management measures only Problem / Risk include river channel maintenance and flood warning. Surface water flooding may occur in other smaller villages near minor watercourses. P2 for areas where channel maintenance can be reduced. P3 for other areas. Policy P5 for Thetford and Bury St Edmunds where there is significant risk of flooding P6 should be adopted where there is the opportunity to use areas as active floodplain.

Flood risk is currently managed to an acceptable level in most of the flood risk areas. Flooding poses a particular problem in Thetford and Bury St Edmunds, thus further actions to reduce flood risk at these locations will be required.

People and Property: There are approximately 7,300 people at risk of flooding in a 100 year (1% AEP) flood event; this increases to approximately 10,000 people in the future with the added influence of climate change. The damages caused by flooding in a 100 year (1% AEP) event is approximately £1,444,000 AAD at the high risk areas (Bury St Edmunds and Thetford). The amount of damages in these locations is likely to increase to approximately £2,600,000 AAD with the added influence of climate change.

Environment: This unit contains extensive areas of national and European nature conservation sites which are at risk of river flooding, including 59 SSSIs and 3 SACs. The % area of these sites likely to be inundated with flood water during a 100 year (1% AEP) flood event is highlighted in Appendix H. In the future, increased flooding could have adverse or beneficial effects depending on the habitats, species or landforms present. The area is also of high heritage and landscape interest with 11 SAMs and 4 Joint Character Areas. Future increases in flooding frequency, depth, duration, and associated changes to the water table may increase the magnitude upon these historic sites. The current indirect effects of flooding, which landscape designations could suffer from (e.g. changes in Why the chosen vegetation), are likely to increase in magnitude in the future due to the increased volume of policy was water. A large part of the river corridor is used for angling, cycling, walking, horse riding, selected and boating activities which are currently disrupted for short periods of time during a flood event, however increased frequency and duration of future flooding is likely to lengthen these periods of disruption.

Social: Flooding can cause stress and disruption by damaging property and belongings, and by causing social disruption. The extent of stress depends on a number of factors that are difficult to measure, such as how prepared people are, the level of warning and the time since the last flood event. Increased flooding in the future could increase these social impacts. People living within settlements at risk of becoming completely isolated during a flood event will be significantly disrupted. There are 6 settlements which become isolated during a 1 in 100 year (1% AEP) flood event including Freckenham, Garboldisham, Hargrave, Thurston and Walsham Le Willows (see Table 3.4).

Overall assessment: We have selected policy 5 for Thetford and Bury St Edmunds as they are the major settlements at risk of flooding within this policy unit. Within Thetford and Bury St Edmunds we will need a combination of minor works, extensions of existing defences and possible upstream storage areas to take further action to manage flood risk. We have adopted policy 6 where there is the opportunity to use areas as active floodplain Flood storage areas within this policy unit will also benefit the Fens area downstream. We have attached policy 3 to areas within the catchment where flooding currently causes no major disruption and where future risk is insignificant. The flood risks in other settlements are small and, following assessment, flood risk management can probably be reduced so policy 2 would be suitable. Changes in land use and improved drainage control will benefit

Environment Agency 151 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 all areas within the policy unit.

Constraints to flood risk management include: • economic viability of flood alleviation schemes; • existing development currently at risk; • the effects of climate change; • Internationally and nationally important habitats and species; • Important heritage sites (archaeological, architectural and ancient environmental material); • rural economic activity including high quality agricultural land; • use of the rivers for navigation; and • land-use and planning policy, which presupposes redevelopment of brownfield sites in the floodplain. • The accuracy and resolution of the broad scale modelling means there is considerable uncertainty in the detail of flooding across the Great Ouse catchment. This is particularly true for catchments with vast areas of floodplain, complex local-scale drainage systems, and recent flood defences which have not been picked up by the model. • We have only provided a high level, strategic view of flood risk in the CFMP and the assessment has focussed on strategic areas affected. Where we have highlighted areas where there needs to be more work carried out to manage flood risk, a more detailed Risks, flood risk management study will assess where certain measures are practical and can be Uncertainties & implemented. Dependencies • The risk from groundwater is an issue within this policy unit, however the extent of this risk has not been defined or quantified. We are aware of a groundwater model being produced for this region; these results will be fed into subsequent strategy studies. Similarly, flood risk associated with sewers has not been clearly defined or quantified. We are aware that flooding from sewers is a widespread, diffuse and short-term problem. Therefore, there is an opportunity to improve integration of flood risk management and work with other interested parties such as Anglian Water.

Environment Agency 152 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 6.4 Southern Rivers summary table

Southern Rivers Policy Unit 3 Includes larger settlements of Cambridge, Saffron Walden, and Newmarket. The main river in the unit is the River Cam. The Cam catchment contains sub-catchments of the River Rhee, Bourn Brook and River Granta. The floodplain of this catchment is narrow and the rivers can react quickly to heavy rainfall. The Cottenham Lode system is a reactive catchment; this can lead to localised flooding. Bassingbourn, Croyden, Wendy, and parts of Cambridge are protected from a 1 in 100 year (1% AEP) flood event by flood Problem / Risk defences. Flood risk at these locations, both now and in the future, is sustainable; however flood risk remains unacceptable in several parts of the catchment (Cottenham, Westwick, Great Chesterford and Sawston). This unit encompasses one of the fastest growing areas in the East of England. The area is under pressure for more development, which has the potential to increase flood risk in the catchment. P2 for areas where channel maintenance can be reduced. P3 where current flood risk measures are modest and can be sustained. Policy P5 where current flood risk measures are insufficient for both the current and future flood risk (in the River Cam and the Cottenham Lode system). P6 should be adopted where there is the opportunity to use areas as active floodplain.

People and Property: There are approximately 11,000 people at risk of flooding in a 100 year (1% AEP) flood event; this increases to approximately 15,000 people in the future with the added influence of climate change. The damages caused by flooding in a 100 year (1% AEP) event is approximately £3,869,000 AAD at the high risk areas (Great Chesterford, Sawston, Cambridge and Trumpington on the River Cam; and Cottenham and Westwick on Cottenham Lode). The amount of damages in these locations is likely to increase to approximately £6,105,000 with the added influence of climate change.

Environment: The unit contains extensive areas of national and European nature conservation sites which are at risk of river flooding, including 6 SSSIs, 1 Ramsar, and 1 SAC. The % area of these sites likely to be inundated with flood water during a 100 year (1% AEP) flood event is highlighted in Appendix H. In the future, increased flooding could have adverse or beneficial effects depending on the habitats, species or landforms present. The area is also of high heritage and landscape interest with 5 SAMs and 3 Joint Character Areas. Future increases in flooding frequency, depth, duration, and associated changes to the water table may increase the magnitude upon these historic sites. The current indirect effects of flooding, which landscape designations could suffer from (e.g. changes in Why the chosen vegetation), are likely to increase in magnitude in the future due to the increased volume of policy was water. A large part of the river corridor is used for angling, cycling, walking, horse riding, selected and boating activities which are currently disrupted for short periods of time during a flood event, however increased frequency and duration of future flooding is likely to lengthen these periods of disruption.

Social: Flooding can cause stress and disruption by damaging property and belongings, and by causing social disruption. The extent of stress depends on a number of factors that are difficult to measure, such as how prepared people are, the level of warning and the time since the last flood event. Increased flooding in the future could increase these social impacts. People living within settlements at risk of becoming completely isolated during a flood event will be significantly disrupted. There are 4 settlements which become isolated during a 1 in 100 year (1% AEP) flood event including Water End, Newmarket, Histon and Bartlow (see Table 3.4).

Overall assessment: Within the Southern Rivers policy unit, flood risk is significant, particularly on the upper and middle Cam and the Cottenham Lode system. There is potential in the unit to reduce flood risk through strategic floodplain storage, upgrading of urban drainage, and land use changes. Further strategy studies will be required to select appropriate flood risk management measures for the policy 6, 5, 3 and 2 areas. Policy 6 will be used where there is the opportunity for strategic catchment-wide use of the

Environment Agency 153 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 floodplain to temporarily store large volumes of water, and hence benefit downstream areas, for example, the Fens Policy Unit. This could also enhance the conservation value of the policy unit. The estimated damages in this policy unit are substantial totalling £3,452,000 during a 100 year (1% AEP) flood event at the identified high risk areas of Great Chesterford, Sawston, Cambridge, Trumpington, Cottenham and Westwick. The risk at these locations is unsustainable, thus the areas need further protection and require a policy 5. Elsewhere within this policy unit, the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (policy 3). Furthermore, it may be suitable to reduce our flood risk management actions at certain locations so a policy 2 could be implemented. We will need an assessment to identify specific locations where this can be applied.

Opportunities to improve flood risk management include: • the use of a catchment-wide hydrological study to identify flood storage areas and identify possible wider benefit from flood risk management schemes. This would complement current floodplain and river restoration initiatives currently in development such as the Great Ouse Strategy Project. These newly created wetland areas will benefit nature conservation, communities and flood management, as well as contributing towards the objectives of the EU Water Framework Directive. • the use of a flood risk management strategy on the River Cam and its tributaries (see Section 7). These studies should identify what further actions can be taken to mange flood risk at Great Chesterford, Sawston, Cambridge, Trumpington, Cottenham and Westwick. The study will also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain. • prevention of inappropriate development in the floodplain and in high groundwater risk areas; • reduce runoff from urban development using SUDS to increase the time to peak flow. Land use changes involving conversion of arable land to grassland/woodland, which could increase attenuation in the catchment and reduce peak flood flows. Such changes Policy unit-wide would benefit both conservation and flood risk management. Opportunities & Constraints Constraints to flood risk management include: • economic viability of flood alleviation schemes; • existing development currently at risk; • the effects of climate change; • Internationally and nationally important habitats and species; • Important heritage sites (archaeological, architectural and ancient environmental material); • rural economic activity including high quality agricultural land; • a lack of areas within the catchment for large-scale floodplain storage; • use of the rivers for navigation; • suitable space available for the planned growth within the unit, taking into account flood risk; and • land-use and planning policy, which presupposes redevelopment of brownfield sites in the floodplain.

Environment Agency 154 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 • The accuracy and resolution of the broad scale modelling means there is considerable uncertainty in the detail of flooding across the Great Ouse catchment. This is particularly true for catchments with vast areas of floodplain, complex local-scale drainage systems, and recent flood defences which have not been picked up by the model. • We have only provided a high level, strategic view of flood risk in the CFMP and the assessment has focussed on strategic areas affected. Where we have highlighted areas where there needs to be more work carried out to manage flood risk, a more detailed Risks, flood risk management study will assess where certain measures are practical and can be Uncertainties & implemented. Dependencies • The risk from groundwater is an issue within this policy unit, however the extent of this risk has not been defined or quantified. We are aware of a groundwater model being produced for this region; these results will be fed into subsequent strategy studies. Similarly, flood risk associated with sewers has not been clearly defined or quantified. We are aware that flooding from sewers is a widespread, diffuse and short-term problem. Therefore, there is an opportunity to improve integration of flood risk management and work with other interested parties such as Anglian Water.

Environment Agency 155 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 6.5 Bedford Ouse summary table

Bedford Ouse Policy Unit 4 Includes larger settlements of Bedford, Leighton Buzzard, Milton Keynes, Huntingdon and St Neots. The Bedford Ouse is a large sub-catchment with several settlements at risk (see below). Flood defence measures include a 1 in 100 year (1% AEP) standard of protection (SOP) for Bedford, parts of St Neots, Kempston, Thornborough, Shefford, Huntingdon, and parts Problem / Risk of Towcester, and a large sustainable drainage system for Milton Keynes providing 1 in 100 SOP. In addition, channel maintenance is carried out for smaller villages and towns throughout the sub-catchment. P2 for areas where channel maintenance can be reduced. P3 for other areas. Policy P4 for large urban settlements. P5 for areas with significant risk of flooding. P6 for whole policy unit.

People and Property: There are approximately 67,000 people at risk of flooding during a 100 year (1% AEP) flood event; this increases to approximately 92,000 people in the future with the added influence of climate change. The damages caused by flooding in a 100 year (1% AEP) within the high risk areas listed below is approximately £34,031,000 AAD:

Alconbury/Alconbury Weston, Towcester, Biggleswade, Beeston, Sandy, Blunham, Newport Pagnell, Godmanchester, Holywell, Huntingdon, Needingworth, Swavesy, Wyton, Brampton, St Neots, Eaton Socon, Offord Darcy, Offord Cluny, Barton Le Clay, Lower Shelton, Stewartby, Henlow, Clifton, Stevenage-Little Wymondley, Brackley, Bromham, Clophill, Fenny Stratford, Graveley, Great Barford, Letchworth, Olney, Potton, Riseley, Spaldwick, Stotfold, Wilden and Kempston

The amount of damages in these locations is likely to increase to approximately £74,130,000 with the added influence of climate change.

Environment: This unit contains extensive areas of national and European nature conservation sites which are at risk of river flooding, including 17 SSSIs and 1 SAC. The % area of these sites likely to be inundated with flood water during a 100 year (1% AEP) flood event is highlighted in Appendix H. In the future, increased flooding could have adverse or Why the chosen beneficial effects depending on the habitats, species or landforms present. The area is also policy was of high heritage and landscape interest with 59 SAMs and 6 Joint Character Areas. Future selected increases in flooding frequency, depth, duration, and associated changes to the water table may increase the magnitude upon these historic sites. The current indirect effects of flooding, which landscape designations could suffer from (e.g. changes in vegetation), are likely to increase in magnitude in the future due to the increased volume of water. A large part of the river corridor is used for angling, cycling, walking, horse riding, and boating activities which are currently disrupted for short periods of time during a flood event, however increased frequency and duration of future flooding is likely to lengthen these periods of disruption.

Social: Flooding can cause stress and disruption by damaging property and belongings, and by causing social disruption. The extent of stress depends on a number of factors that are difficult to measure, such as how prepared people are, the level of warning and the time since the last flood event. Increased flooding in the future could increase these social impacts. People living within settlements at risk of becoming completely isolated during a flood event will be significantly disrupted. There are 27 settlements which become isolated during a 1 in 100 year (1% AEP) flood event including Brook End, Church End, Hemingford Abbots, Hemingfod Grey and Spaldwick (see Table 3.4).

Overall Assessment: Flood risk in the Bedford Ouse catchment is significant. There is potential in the unit to reduce flood risk through strategic floodplain storage, upgrading of urban drainage, and land use changes. Further strategy studies will be required to select

Environment Agency 156 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 appropriate flood risk management measures for the policy 6 5 3 and 2 areas.

Policy 6 will be used where there is the opportunity for strategic catchment-wide use of the floodplain to temporarily store large volumes of water, and hence benefit downstream areas, for example, the Fens Policy Unit. This could also enhance the conservation value of the policy unit.

The CFMP has identified that the estimated damages in this policy unit are substantial and flood risk is unsustainable at the following locations where further action should be taken to reduce flood risk (policy 5): Alconbury/Alconbury Weston, Towcester, Biggleswade, Beeston, Sandy, Blunham, Newport Pagnell, Godmanchester, Holywell, Huntingdon, Needingworth, Swavesy, Wyton, Brampton, St Neots, Eaton Socon, Offord Darcy, Offord Cluny, Barton Le Clay, Lower Shelton, Stewartby, Henlow, Clifton, Stevenage-Little Wymondley, Brackley, Bromham, Clophill, Fenny Stratford, Graveley, Great Barford, Letchworth, Olney, Potton, Riseley, Spaldwick, Stotfold, Wilden and Kempston.

Further Action should be taken at Milton Keynes and Bedford in order to sustain the current scale of flood risk (policy 4).

Elsewhere within this policy unit, the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (policy 3). Furthermore, it may be suitable to reduce our flood risk management actions at certain locations so a policy 2 could be implemented. We will need to undertake an assessment to identify specific locations where this can be applied.

Environment Agency 157 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Opportunities to improve flood risk management include: • the use of a catchment-wide hydrological study to identify flood storage areas and identify possible wider benefit from flood risk management schemes. This would complement current floodplain and river restoration initiatives currently in development such as including the Great Ouse Waterway and Wetland Project, the Ivel and Ouse Countryside Project, the Huntingdonshire Wet Woodlands and Wet Meadows Project, and the Bedfordshire Wet Woodland Project. These newly created wetland areas will benefit nature conservation, communities and flood management, as well as contributing towards the objectives of the EU Water Framework Directive. • the use of flood risk management strategies on the River Ivel and its tributaries, Tove, Ouzel, Bedford Ouse, Kym, Twins, Ellington and Brampton Brook and Alconbury Brook (see Section 7). These studies should identify what further actions can be taken to mange flood risk at high risk locations. The study will also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain. • prevention of inappropriate development in the floodplain and in high groundwater risk areas. • reduce runoff from urban development using SUDS to increase the time to peak flow. Policy unit-wide • land use changes involving conversion of arable land to grassland/woodland, which could Opportunities & increase attenuation in the catchment and reduce peak flood flows. Such changes would Constraints benefit both conservation and flood risk management.

Constraints to flood risk management include: • economic viability of flood alleviation schemes; • existing development currently at risk; • the effects of climate change; • Internationally and nationally important habitats and species; ; • important heritage sites (archaeological, architectural and ancient environmental material); • rural economic activity including high quality agricultural land; • a lack of areas within the catchment for large-scale floodplain storage; • use of the rivers for navigation; and • land-use and planning policy, which presupposes redevelopment of brownfield sites in the floodplain. . • The accuracy and resolution of the broad scale modelling means there is considerable uncertainty in the detail of flooding across the Great Ouse catchment. This is particularly true for catchments with vast areas of floodplain, complex local-scale drainage systems, Risks, and recent flood defences which have not been picked up by the model. Uncertainties & • We have only provided a high level, strategic view of flood risk in the CFMP and the Dependencies assessment has focussed on strategic areas affected. Where we have highlighted areas where there needs to be work carried out to manage flood risk, a detailed flood risk management study will assess where certain measures are practical and can be implemented.

Environment Agency 158 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Table 6.6 The Fens summary table

The Fens Policy Unit 5 Includes the tidal River Ouse, relief channel, cut-off channel, the embanked sections of the Rivers Lark, Little Ouse, Wissey, Cam and the extensive network of drains. Problem / Risk Rural catchment with significant environmental designations situated within the policy unit. P2 for areas where channel maintenance can be reduced. P3 for areas where flood risk is acceptable. Policy P4 for isolated properties and areas with major flood defences. P6 for the whole policy unit where there is the opportunity.

People and Property: There are approximately 48,000 people at risk of flooding in a 100 year (1% AEP) flood event; this increases to approximately 54,000 people in the future with the added influence of climate change. The damages caused by flooding in a 0.1% AEP within Mildenhall, Kings Ripton to Wistow, Wisbech, Langwood Fen, Isleham Fens, Hilgay Fen, Southery Fen, Ely, Littleport, Burwell, Waterbeach, Aldreth and Smithey Fen is approximately £991,000 AAD. The amount of damages in these locations is likely to increase to approximately £1,213,000 AAD with the added influence of climate change.

Environment: The unit contains extensive areas of national and European nature conservation which are at risk of fluvial flooding, including 21 SSSIs, 2 Ramsar sites, 2 SACs and 1 SPA. The % area of these sites likely to be inundated with flood water during a 100 year (1% AEP) flood event is highlighted in Appendix H. In the future, increased flooding could have adverse or beneficial effects depending on the habitats, species or landforms present. The area is also of high heritage and landscape interest with 23 SAMs and 1 Joint Character Area. Future increases in flooding frequency, depth, duration, and associated changes to the water table may increase the magnitude upon these historic sites. The current indirect effects of flooding, which landscape designations could suffer from (e.g. changes in vegetation), are likely to increase in magnitude in the future due to the increased volume of water. A large part of the river corridor is used for angling, cycling, walking, horse riding, and boating activities which are currently disrupted for short periods of time during a flood event, however increased frequency and duration of future flooding is likely to lengthen these periods of disruption. Why the chosen policy was Social: Flooding can cause stress and disruption by damaging property and belongings, selected and by causing social disruption. The extent of stress depends on a number of factors that are difficult to measure, such as how prepared people are, the level of warning and the time since the last flood event. Increased flooding in the future could increase these social impacts. People living within settlements at risk of becoming completely isolated during a flood event will be significantly disrupted. There are 36 settlements which become isolated during a 1 in 100 year (1% AEP) flood event including Ten Mile Bank, Green End, Ramsay St Mary’s and Pondersbridge (see Table 3.4).

Overall Assessment: Within the Fens policy unit flood risk is significant, particularly in Mildenhall and Ramsey where damages total £768,000. There is also the potential for significant damage to the high grade agricultural land that exists within this policy unit. The agricultural damages caused by flooding in a 100 year (1% AEP) flood event amount to approximately £4,600,000 AAD. Policy 6 will be used where there is the opportunity for strategic catchment wide use of the flood plain, which could be used to temporarily store large volumes of water and hence benefit other areas in the Fens Policy Unit. It could also have the potential to enhance conservation value within some areas. The current flood risk is accepted and is at a sustainable level, but may require further action as the changes in climate and land use occur due to increases in surface run off and river flows. For these locations, a policy 4 will be suitable. Elsewhere within this policy unit, the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (policy 3). Furthermore, it may be suitable to adopt a policy 2 at certain locations and reduce our flood risk management actions. We will need an assessment to identify specific locations where this can be

Environment Agency 159 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 applied.

Opportunities to improve flood risk management include: • creation of additional wetland areas, this would benefit nature conservation, communities and flood management; • the use of a Fens flood risk management strategy (see Section 7). This study should identify further actions to sustain the current scale of flood risk in the future for some isolated settlements and areas with major defences; • re-instatement of functional floodplains; • storage of large volumes of water could be used to enhance agricultural productivity during low flow summer months; • increase the number of areas accessible for recreation; • enhancement of the water level management at environmentally designated sites, for example in the three major wetland creation sites: Great Fen, Needingworth wetland and Wicken Fen; and Policy unit-wide • prevention of inappropriate development in the floodplain and in high groundwater risk Opportunities & areas. Constraints

Constraints to flood risk management include : • rural economic activity including high quality agricultural land; • internationally and nationally important habitats and species; • important heritage sites (archaeological, architectural and ancient environmental material); • use of the rivers for navigation; • economic viability of flood alleviation schemes; • the effects of climate change; and • land-use and planning policy, which presupposes redevelopment of brownfield sites in the floodplain.

• The accuracy and resolution of the broad scale modelling means there is considerable uncertainty in the detail of flooding across the Great Ouse catchment. This is particularly true for catchments with vast areas of floodplain, complex local-scale drainage systems, and recent flood defences which have not been picked up by the model. • We have only provided a high level, strategic view of flood risk in the CFMP and the Risks, assessment has focussed on strategic areas affected. Where we have highlighted areas Uncertainties & where there needs to be more work carried out to manage flood risk, a more detailed Dependencies flood risk management study will assess where certain measures are practical and can be implemented. • The largest risk is the uncertainty of sea level rise and siltation in the Tidal Ouse. This could have implications on drainage rates within this policy unit. • Restrictions on use of existing designated sites as temporary flood storage units.

The appraisal confirms that the policies we have chosen are appropriate and help achieve many of the objectives for managing flood risk. Reducing flood risk management actions leads to an increase in flood risk against many objectives but can provide opportunities for enhancing wildlife. Increasing flood risk management actions reduces flood risk but may not be cost effective.

The policy option choices we make in some parts of the catchment and the measures we use to implement them will affect other parts of the catchment. Therefore, hydrological and flood risk management studies should be carried out to consider the implications of any actions on the rest of the catchment (see Section 7).

Environment Agency 160 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 7 Delivering the CFMP

In this section of the report we provide information about the action plan. This chapter also details what we believe to be the inter-relationships between selected policies and actions, and how we will monitor and review the plan.

7.1 Action plan

In the CFMP we have selected the most appropriate policies for the different policy units. We have suggested strategic flood risk management responses that could achieve these policies. This is the first step towards implementation of the CFMP flood risk management policies. The actions need to be prioritised, this is described in Table 7.1; Table 7.2 outlines the actions we have suggested. We have worked with other authorities, organisations and groups to develop policies and actions, so that everyone can adopt the plan as a way forward for managing flood risk. Whilst most actions are our responsibility, we would like to promote and encourage a working relationship with other groups so that we can improve flood risk together. We aim to strengthen existing links and to continue to work together to achieve the actions from the CFMP.

Table 7.1 Prioritised action

Priority Results(s) of action

High • Contributes to a significant reduction in flood risk within high risk areas. • Being clear about the current level of risk in areas where this is not known but could have a major effect. • Likely to increase sustainability and could give substantial economic benefits if implemented early.

Medium • Contributes to general reductions in flood risk. • Being clear about the current level of risk in areas where this is not known but could have an impact. • May not achieve immediate benefits, but should reduce flood risk over the medium term. • Likely to provide cost effective reductions in flood risk, which is viable if developed together with other aims such as environmental improvements.

Low • Has the potential to reduce flood risk over the long term. • Deals with potential flood risk that may occur in the future.

Environment Agency 161 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

ALL POLICY UNITS

Action Lead Partner Timescale Priority Catchment wide hydrological study- Develop a high level hydrological Environment Agency 2007-2009 High study for the River Great Ouse and its tributaries. Initially the study will Strategic and bring together available hydrological studies and models. From this Development Planning information the study will assess how catchment wide flood risk problems, Team such as climate change and development, can be addressed through floodplain storage. The study will build on the CFMP and locate suitable areas for floodplain storage. The study could also be used to investigate breach scenarios throughout embanked sections of the Great Ouse catchment.

The catchment wide hydrological study will identify flood storage areas and identify possible wider benefit from flood risk management schemes. The study will also identify gaps in the coverage of models across the catchment and recommend that individual river studies develop models to fill these gaps. Liaise with Department of Culture, Media and Sport (DCMS) to identify Environment Agency 2007-2011 Medium specific opportunities for flood risk management from planned Olympics Planning Liaison Team 2012 developments. Liaise with planning authorities to ensure that update cycles of the Regional Environment Agency 2007-2011 Medium Spatial Strategy are used in order to take specific opportunities for flood risk Planning Liaison Team management. Liaise with planning authorities to make sure that brownfield sites within the Environment Agency 2007-ongoing Medium floodplain are not automatically redeveloped. Planning Liaison Team

Identify opportunities to reduce runoff from landuse by future de- Environment Agency 2007-2008 Medium intensification. Strategic and Development Planning Team Encourage rigorous planning control to restrict new development in the Local Planning 2007-2100 High floodplain. Authorities, Environment Agency Planning Liaison and Development Control

Environment Agency 162 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 ALL POLICY UNITS

Action Lead Partner Timescale Priority teams

Continue to improve flood warning and emergency planning processes Environment Agency 2007-2100 Medium Flood Incident Planning Team, Emergency Services and County and Parish councils across the catchment

Encourage environmental stewardship schemes to reduce flood risk to Natural England, NFU, 2007-2027 Low vulnerable areas. Environment Agency Fisheries, Recreation and Biodiversity team Undertake a study to investigate problems with surface water and sewer Anglian Water, County 2008-2018 High flooding and propose options for work to reduce this. Councils and Highway Authorities Promote the use of sustainable drainage systems where appropriate. Local Planning 2007-2100 High Authorities, Environment Agency Planning Liaison and Development Control teams Increase flood awareness and education. Environment Agency 2007-2027 Low Flood Incident Management and External Relation teams

Environment Agency 163 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 POLICY UNIT 1: NORTH WEST NORFOLK RIVERS The preferred policy for this unit is to work with natural processes and make more use of floodplains for water storage. For example create flood storage areas or washlands upstream of a risk area.

VISION

North West Norfolk Rivers policy unit is a mainly rural catchment. The main rivers in this unit are the River Nar, River Ingol, Heacham River, and Babingly Brook. There are a significant number of people and properties at risk from main river flooding. Within the 1 per cent AEP flood extent there are 23, 000 people at risk and £526,000 AAD. Current flood risk management measures include channel maintenance and flood warning. This policy unit is relatively independent from other areas.

The CFMP has identified that further action to reduce flood risk should be taken at the following locations: King’s Lynn, Downham Market and North Runcton (P5). The catchment wide hydrological study will identify flood storage areas to reduce flood risk at the catchment scale. These storage areas may be located within this policy unit and would reduce flood risk at the places listed above. This may mean that no other flood risk management measures would need to be taken. The King’s Lynn and Downham Market flood risk management studies should investigate this. The flood risks in other villages are small and, following assessment, flood risk management can probably can be reduced (P2).

Action Lead Partner Timescale Priority King’s Lynn and North Runcton flood risk management study- This study EA Strategic and 2012-2014 High should identify what further actions can be taken to manage flood risk at Development Planning King’s Lynn and North Runcton (P5). The study must investigate flood risk Team from the River Great Ouse, River Nar, Puny and Pierpoint Drains, and the Old

Environment Agency 164 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 East Sea Bank and Gaywood River. The study must take account of the outputs of the catchment wide hydrological study, King’s Lynn Tidal Defences Strategy Review and The Wash SMP. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain (P6). Downham Market flood risk management study- This study should identify EA Strategic and 2012-2014 Medium what further actions can be taken to manage flood risk at Downham Market Development Planning (P5). The study must take into account the outputs of the catchment wide Team hydrological study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain (P6). The Tidal Great Ouse flood risk management study- To continue to NCPMS (Steve Peck) 2006-2008 High develop this study and implement its outputs. Asset System Management Plan- A detailed plan of works to continue with EA Asset System 2008-2010 Medium our existing or alternative actions to manage flood risk at the current level. Management (North) The plan should be applied to the whole Bedford Ouse policy unit except those areas where we have suggested P5 or P4. Asset System Management Plan- This plan should identify specific locations EA Asset System 2008-2010 Medium where we can reduce our existing flood risk management actions. The plan Management (North) should be applied to the whole Bedford Ouse policy unit except those areas where we have suggested P5 or P4.

Environment Agency 165 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 POLICY UNIT 2: EASTERN RIVERS The preferred policy for this unit is to work with natural processes and make more use of floodplains for water storage. For example create flood storage areas or washlands upstream of a risk area.

VISION

Eastern Rivers policy unit is a rural catchment. The main rivers in this unit are the River Lark, River Wissey and Little Ouse River. There are a number of people and properties at risk from main river flooding. Within the 1 per cent AEP flood extent there are 7,300 people at risk and £1, 444, 000 AAD. Current flood risk management measures include river channel maintenance and flood warning. Flood defences help to protect Bury St Edmunds. Surface water flooding may occur in other smaller villages near minor watercourses. Flood risk is currently managed to an acceptable level in most of the flood risk areas and flooding only poses a minor and short-term problem. Actions in this policy unit will influence the Fens.

The CFMP has identified that further action to reduce flood risk should be taken at Bury St Edmunds and Thetford (P5). The catchment wide hydrological study will identify flood storage areas to reduce flood risk at the catchment scale. These storage areas may be located within this policy unit and would reduce flood risk at the places listed above. This may mean no other flood risk management measures would need to be taken. The River Lark and Little Ouse River flood risk management studies should investigate this. Elsewhere within this policy unit the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (P3). Furthermore, it may be suitable to reduce our flood risk management actions at certain locations (P2).

Action Lead Partner Timescale Priority River Lark and tributaries flood risk management study- This study EA Strategic and 2010-2012 Medium should identify what further actions can be taken to manage flood risk at Bury Development Planning St Edmunds (P5). The study must take into account the outputs of the Team

Environment Agency 166 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 catchment wide hydrological study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). Little Ouse River and its tributaries flood risk management study- This EA Strategic and 2010-2012 Medium study should identify what further actions can be taken to manage flood risk at Development Planning Thetford (P5). The study must take into account the outputs of the catchment Team wide hydrological study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain (P6). Asset System Management Plan- A detailed plan of works to continue with EA Asset System 2008-2010 Medium our existing or alternative actions to manage flood risk at the current level. Management (North) The plan should be applied to the whole Eastern River policy unit except those areas where we have suggested P5. Asset System Management Plan- This plan should identify specific locations EA Asset System 2008-2010 Medium where we can reduce our existing flood risk management actions (P2). The Management (North) plan should be applied to the whole Eastern Rivers policy unit except those areas where we have suggested P5.

Environment Agency 167 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 POLICY UNIT 3: SOUTHERN RIVERS The preferred policy for this unit is to work with natural processes and make more use of floodplains for water storage. For example create flood storage areas or washlands upstream of a risk area.

VISION

The main rivers in this unit are the River Cam, River Rhee, Bourn Brook, and the River Granta. The floodplain of this catchment is narrow and the rivers react quickly to heavy rainfall. There are a significant number of people and properties at risk from main river flooding. Within the 1 per cent AEP flood extent there are 11,000 people at risk and £3,869,000 AAD. Current flood risk management measures include channel maintenance and flood warning. Flood defences help to protect Cambridge, Bassingbourn, Croyden and Wendy.

The unit encompasses one of the fastest growing areas in the East of England. The area is under pressure for more development and there is a need to provide more space for housing, as well as for business growth in urban and rural areas. All of this growth has the potential to increase flood risk in the catchment. Actions in this policy unit will influence the Fens.

The CFMP has identified that further action to reduce flood risk should be taken at the following locations: Great Chesterford, Sawston, Cambridge, Trumpington, Cottenham and Westwick (P5). The catchment wide hydrological study will identify flood storage areas to reduce flood risk at the catchment scale. These storage areas may be located within this policy unit and would reduce flood risk at the places listed above. This may mean no other flood risk management measures would need to be taken. The River Cam and tributaries flood risk management study should investigate this. Elsewhere within this policy unit the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (P3). Furthermore, it may be suitable to reduce our flood risk management actions at certain locations (P2).

Environment Agency 168 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Action Lead Partner Timescale Priority River Cam and tributaries flood risk management study- This study EA Strategic and 2010-2012 Medium should identify what further actions can be taken to manage flood risk at: Development Planning Great Chesterford, Sawston, Cambridge and Trumpington on the River Cam; Team and Cottenham and Westwick on Cottenham Lode (P5). The study must take into account of the outputs the catchment wide hydrological study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs or by restoring the natural floodplain (P6). This study should also review Bin Brook Flood Alleviation Scheme to assess whether it is appropriate within the context of strategic flood risk management. Asset System Management Plan- A detailed plan of works to continue with EA Asset System 2008-2010 Medium our existing or alternative actions to manage flood risk at the current level Management (North) (P3). The plan should be applied to the whole Southern Rivers policy unit except those areas where we have suggested P5. Asset System Management Plan- This plan should identify specific locations EA Asset System 2008-2010 Medium where we can reduce our existing flood risk management actions (P2). The Management (North) plan should be applied to the whole Southern Rivers policy unit except those areas where we have suggested P5.

Environment Agency 169 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 POLICY UNIT 4: BEDFORD OUSE The preferred policy for this unit is to work with natural processes and make more use of floodplains for water storage. For example create flood storage areas or washlands upstream of a risk area.

VISION

The main river in this policy unit is the Great Ouse. Tributaries include the rivers, Twins, Tove, Ouzel, Ivel, Alconbury Brook,and Kym. There are a significant number of people and properties at risk from main river flooding. Within the 1 per cent AEP flood extent there are 67,000 people at risk and £34,031,000 annual average damages. Current flood risk management includes flood warning and channel maintenance in smaller villages and towns throughout the unit. Flood defences help to protect Bedford, Towcester, Milton Keynes, St Neots, Kempston, Thornborough, Shefford, and Huntingdon. Strategic catchment wide use of the floodplain could be used to temporarily store large volumes of water, and hence benefit downstream areas including the Fens Policy Unit.

The CFMP has identified that further action to reduce flood risk should be taken at the following locations: Alconbury/Alconbury Weston, Towcester, Biggleswade, Beeston, Sandy, Blunham, Newport Pagnell, Godmanchester, Holywell, Huntingdon, Needingworth, Swavesy, Wyton, Brampton, St Neots, Eaton Socon, Offord Darcy, Offord Cluny, Barton Le Clay, Lower Shelton, Stewartby, Henlow, Clifton, Stevenage-Little Wymondley, Brackley, Bromham, Clophill, Fenny Stratford, Graveley, Great Barford, Letchworth, Olney, Potton, Riseley, Spaldwick, Stotfold, Wilden and Kempston (P5). Further action should be taken to sustain the current scale of flood risk into the future at Milton Keynes and Bedford (P4).

The catchment wide hydrological study will identify flood storage areas to reduce flood risk at the catchment scale. These storage areas may be located within this policy unit and would reduce flood risk at the places listed above. This may mean no other flood risk management measures would

Environment Agency 170 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 need to be taken. The studies identified by this CFMP should investigate this. Elsewhere within this policy unit the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (P3). Furthermore, it may be suitable to reduce our flood risk management actions at certain locations (P2).

Action Lead Partner Timescale Priority Ivel and its tributaries flood risk management study- This study should EA Strategic and 2008-2010 High identify what further actions can be taken to manage flood risk at Development Planning Biggleswade, Beeston, Sandy, Blunham, Potton and Stotfold on the River Team Ivel; Barton Le Clay and Clophill, on the River Flit; Henlow and Clifton on Henlow Brook; Graveley, and Stevenage-Little Wymondley on the River Hiz; and Letchworth on Pix Brook (P5). The study must take into account the outputs of the catchment wide hydrological study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). River Tove flood risk management study- This study should identify what EA Strategic and 2008-2010 Medium further actions can be taken to manage flood risk at Towcester (P5). The Development Planning study must take into account the outputs of the catchment wide hydrological Team study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). River Ouzel flood risk management study- This study should identify what EA Strategic and 2008-2010 Medium further actions can be taken to manage flood risk at Fenny Stratford and Development Planning Newport Pagnell (P5). The study should identify further actions to sustain the Team current scale of flood risk into the future at Milton Keynes (P4). The risk of flooding to Newport Pagnell and Milton Keynes from the Great Ouse should be incorporated. The study must take into account the outputs of the catchment wide hydrological study, and consider the implications of any actions on the rest of the catchment. The Bedford Ouse flood risk management study- This study should EA Strategic and 2009-2011 High identify what further actions can be taken to manage flood risk at: Development Planning Godmanchester, Holywell, Huntingdon, Needingworth, Eaton Socon, Team Swavesy, Wyton, Offord Darcy, Offord Cluny, Lower Shelton, Stewartby, Brackley, Olney, Wilden, Bromham and Kempston (P5). The study should

Environment Agency 171 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 identify further actions to sustain the current scale of flood risk into the future at Bedford (P4). The study must take into account the outputs of the catchment wide hydrological study, and consider the implications of any actions on the rest of the catchment. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). The study should also review Godmanchester flood alleviation scheme to assess whether it is appropriate within the context of strategic flood risk management. Ellington and Brampton Brook flood risk management study- This study EA Strategic and 2008-2010 Low should identify what further actions can be taken to manage flood risk at Development Planning Spaldwick on Ellington Brook and Brampton on Brampton Brook (P5). The Team study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). River Kym flood risk management study- This study should identify what EA Strategic and 2008-2010 Medium further actions can be taken to manage flood risk at Riseley and St Neots Development Planning (P5). The risk of flooding to St Neots from the Great Ouse should be Team incorporated. The study must also consider actions which will attenuate/balance flood flows by creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). River Twins flood risk management study- This study should identify what EA Strategic and 2008-2010 Low further actions can be taken to manage flood risk at Thornborough (P5). The Development Planning study must also consider actions which will attenuate/balance flood flows by Team creating washlands and balancing reservoirs, or by restoring the natural floodplain (P6). Alconbury Brook Asset System Management Plan- This plan should EA Asset System 2008-2010 Medium review Alconbury and Alconbury Weston schemes to assess whether they are Management (South) appropriate within the context of the CFMP and strategic flood risk management. Asset System Management Plan- A detailed plan of works to continue with EA Asset System 2008-2010 Medium our existing or alternative actions to manage flood risk at the current level Management (South) (P3). The plan should be applied to the whole Bedford Ouse policy unit except those areas where we have suggested P5 or P4. Asset System Management Plan- This plan should identify specific locations EA Asset System 2008-2010 Medium where we can reduce our existing flood risk management actions (P2). The Management (South) plan should be applied to the whole Bedford Ouse policy unit except those areas where we have suggested P5 or P4.

Environment Agency 172 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

POLICY UNIT 5: THE FENS The preferred policy for this unit is to work with natural processes and make more use of floodplains for water storage. For example create flood storage areas or washlands upstream of a risk area.

VISION

The Fens is very rural policy unit. The main watercourses in this unit include the Cranbrook/Counter Drain, The Old West and The Hundred Foot. There area significant number of people and property at risk from river flooding. Within the 1 per cent AEP flood extent there are 48,000 people at risk and £991,000 of annual average damages.

The Fens policy unit has been heavily engineered for flood defence and land drainage purposes. Modifications include completely artificial cut-off channels, channel realignment, and extensive flood embankments. Overall, despite the extensive human influence on the landscape there are extensive areas of environmental importance. The Denver Complex forms the focus of the flood defence system; it protects the low lying land from flooding by the rivers and sea. Actions in the three policy units upstream will influence flood risk in the Fens, and actions in the Fens could have some influence on the drainage of the policy units further upstream.

Strategic catchment wide use of the floodplain could be used to temporarily store large volumes of water, and hence benefit downstream areas within the unit. For some isolated settlements and areas with major defences the current flood risk is accepted and is at a sustainable level, but may require further action as changes in climate and land use occur (P4). Elsewhere within this policy unit the risk of flooding is small and sustainable; continuing with our current flood risk is therefore appropriate (P3). Furthermore, it may be suitable to reduce our flood risk management actions at certain locations (P2).

Environment Agency 173 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Action Lead Partner Timescale Priority The Fens flood risk management study- This study should identify further EA Strategic and 2012-2014 High actions to sustain the current scale of flood risk into the future for some Development Planning isolated settlements and areas with major defences (P4). The study must Team take into account the outputs of the catchment wide hydrological study, Cranbrook/Counter Drain flood risk management strategy, the St Germans pumping station contribution, the Ouse Washes habitat creation project, and consider the implications of any actions on the rest of the catchment. Many of the studies/strategies already progressing within the Fens policy unit are investigating the storage of flood water. However, any further actions within this policy unit must also consider attenuating flood flows, or restoring the natural floodplain (P6). Asset System Management Plan- A detailed plan of works to continue with EA Asset System 2008-2010 Medium our existing or alternative actions to manage flood risk at the current level Management (North) (P3). The plan should be applied to the whole Fens policy unit except those areas where we have suggested P4. Asset System Management Plan- This plan should identify specific locations EA Asset System 2008-2010 Medium where we can reduce our existing flood risk management actions (P2). The Management (North) plan should be applied to the whole Fens policy unit except those areas where we have suggested P4.

Environment Agency 174 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

7.2 Inter-relationships between selected policies and actions

Where we have selected different policies within policy units this may have an affect. For example, as a response to increasing flood risk caused by climate change and urbanisation, we may have to raise flood defences in places where we have selected policies 4 or 5. This could raise water levels in other areas where policies 2 and 3 may apply. We must ensure that any schemes proposing improvements to existing defences or new flood defences do not significantly raise water levels elsewhere.

The CFMP policies should work with and complement other plans and will:

• inform and oversee the way in which we manage flood risk for different catchments; • inform WFD River Basin Management Plans about opportunities and constraints to flood risk management and sustainable flood risk management policies; • become the statutory flood risk management plans required under the proposed EU Floods Directive; • inform regional and local planning guidance about flood risk and future flood risk management policies for different areas; • work with CAMS which manage low flows within the CFMP area; • work with plans to manage surface water and sewer flooding in the CFMP area; • inform flood risk and strategy studies for watercourses in the Great Ouse CFMP, The Wash Shoreline Management Plan and the Tidal Ouse Flood Risk Management Study; and • work with environmental management plans for designated sites.

7.3 Monitoring, review and evaluation

We will be working with partners on the Steering and Consultation groups to implement the CFMP. We will need to regularly review and monitor the CFMP so that we can:

• manage the implementation of the CFMP; • check that the CFMP is being implemented as proposed; and • check that we are achieving the policy and actions of the CFMP.

We will monitor the performance of the CFMP by using indicators and/or outcomes these will be used in annual reports to measure our performance. Following the publication of the CFMP, we will establish an Implementation Manager who will be accountable for:

• setting up implementation group(s) for the CFMP; • monitoring delivery of the CFMP; and • reporting delivery of the CFMP.

Implementation groups will influence the progress in the delivery of the action plan. Members of the Steering Group, Project Team and representatives from lead organisations identified in the action plan will form the implementation group. The implementation group will be able to request a review of the CFMP before a formal review in carried out in five years time. The formal review will reflect significant changes in flood risk or will inform/ influence other plans, such as the Water Framework Directive. The review will consider the following:

• new planning and modelling tools; • the effects of recent significant flood events and urban development; • developments in understanding about climate change; • changes in national policy guidance; and • the most up-to-date information on flood outlines, environmental baseline data, property databases and improved flood estimates.

Environment Agency 175 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Following this review, we may revise the CFMPs flood risk management policies. The CFMP will remain a live document that changes, as there are improvements in our understanding of flood risk throughout the catchment.

Environment Agency 176 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 List of abbreviations

AAD Average Annual Damage

AONB Area of Outstanding Natural Beauty

BAP Biodiversity Action Plan

CAMS Catchment Abstraction Management Strategies

CFMP Catchment Flood Management Plan

CG Consultation Group

COW Critical Ordinary Watercourse

CRoW Countryside Rights of Way Act

CWS County Wildlife Sites

Defra Department for Environment, Food and Rural Affairs

DEM Digital Elevation Model

DTM Digital Terrain Model

DTLR Department for Transport, Local Government and the Regions

EERA East of England Regional Assembly

ESA Environmentally Sensitive Areas

ESRI Environmental Systems Research Institute

EU European Union

FEH Flood Estimation Handbook

FRM Flood Risk Management

FWAG Farming & Wildlife Advisory Group

FWD Flood Warning Direct

GIS Geographical Information System

HAT Highest Astronomical Tide

IDB Internal Drainage Board

IFM Indicative Floodplain Map

IFSAR Interferometric Synthetic Aperture Radar

LiDAR Light Detection and Ranging

LBAP Local Biodiversity Action Plans

LCA Landscape Character Area

Environment Agency 177 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

LEAP Local Environment Area Plan

LNR Local Nature Reserve

MAFF Ministry of Agriculture, Fisheries and Food

MDSF Modelling and Decision Support Framework

MHWS Mean High Water Springs

NFCDD National Flood and Coastal Defence Database

NFU National Farmers Union

NMR National Monument Record

NNR National Nature Reserve

ODN Ordnance Datum Newlyn

PPG25/PPS25 Planning Policy Guidance soon to be replaced by Planning Policy Statement 25: Development and Flood Risk

PT Project Team

RPG Regional Planning Guidance

RSPB Royal Society for the Protection of Birds

RSS Regional Spatial Strategy

RQO River Quality Objective

SAC Special Area for Conservation

SAM Scheduled Ancient Monument

SEA Strategic Environmental Assessment

SFRA Strategic Flood Risk Assessment

SFVI Social Flood Vulnerability Index

SG Steering Group

SMD Soil Moisture Deficit

SMP Shoreline Management Plan

SNCI Sites of Nature Conservation Importance

SoP Standard of protection

SPR Standard percentage run-off

SSSI Site of Special Scientific Interest

SPA Special Protection Area

STW Sewage Treatment Works

SuDS Sustainable Drainage Systems

Environment Agency 178 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Tp Time to Peak

SPR Standard Percentage Run-off

UDP Unitary Development Plan

WFD Water Framework Directive

WLMP Water Level Management Plan

Environment Agency 179 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Glossary of terms

Appraisal The process of defining objectives, examining options and evaluating costs, benefits, risks, opportunities and uncertainties before a decision is made.

Agri-environmental schemes Schemes to conserve and improve the rural environment, including Environmental Stewardship, Countryside Stewardship Scheme and Environmentally Sensitive Areas. Schemes often provide financial incentives for land managers to adopt environmentally beneficial land management practices.

Alluvial Soil or sediments deposited by a river or other running water.

Aquifer A geological stratum (or rock layer) that bears water.

Area of Outstanding Natural Beauty (AONB) Areas of Outstanding Natural Beauty (AONBs) were formally designated under the National Parks and Access to the Countryside Act of 1949 to protect areas of the countryside of high scenic quality that cannot be selected for National Park status due to their lack of opportunities for outdoor recreation (an essential objective of National Parks). The Countryside Agency (soon to be Natural England) is responsible for designating AONBs and advising Government and others on how they should be protected and managed. Further information on AONBs can be found at http://www.aonb.org.uk/

ArcMap A Geographical Information System (GIS) computer Package produced by ESRI.

Attenuation In relation to flooding, the impact of the floodplain on the shape of a flood hydrograph (reducing flood peak and increase flood duration) due to a combination of storage and resistance. Flood attenuation provided by 'natural storage' has increasingly been considered as a useful complement to conventional flood defences in certain situations, e.g. flood attenuation areas that can be used to cope with overflow when river levels rise. By allowing floodwaters on to these open spaces, downstream properties can be better protected.

Average Annual Damage (AAD) Depending on its size (or severity), each flood will cause a different amount of flood damage. The average annual damage is the average damage in pounds per year that would occur in a designated area from flooding over a very long period of time. In many years there may be no flood damage, in some years there will be minor damage (caused by small, relatively frequent floods) and, in a few years, there will be major flood damage (caused by large, rare flood events). Estimation of the average annual damage provides a basis for comparing the effectiveness of different floodplain management measures (i.e. the reduction in the annual average damage).

Benefits Those positive quantifiable and unquantifiable changes that a plan will produce, including damages avoided.

Biodiversity The living component of the natural world. It embraces all plant and animal species and communities associated with terrestrial, aquatic and marine habitats. It also includes genetic variation within species.

Biodiversity Action Plan (BAP) An agreed plan for a habitat or species, which forms part of the UK’s commitment to biodiversity. For further information consult the BAP website: http://www.ukbap.org.uk

Environment Agency 180 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Birds Directive European Community Directive (79/409/EEC) on the conservation of wild birds. Implemented in the UK as the Conservation (Natural Habitats, etc.) Regulations (1994). For further information consult Her Majesties Stationary Office website: http://www.hmso.gov.uk/si/si1994/Uksi_19942716_en_1.htm

Boulder Clay Residue deposited by glaciers as they retracted at the end of the ice ages. It consists of a mixture of rock fragments, clay, sand and gravels.

Calcerous Of, or containing, carbonate of lime or sandstone.

Catchment A surface water catchment is the total area that drains into a river. A groundwater catchment is the total area that contributes to the groundwater component of the river flow.

Catchment Abstraction Management Strategies (CAMS) CAMS are strategies for management of water resources at a local level. They will make more information on water resources allocation publicly available and allow the balance between the needs of abstractors and those of the aquatic environment to be determined in consultation with local interested parties.

Catchment Flood Management Plan (CFMP) Catchment Flood Management Plans (CFMPs) are a large-scale strategic planning framework for the integrated management of flood risks to people and the developed and natural environment in a sustainable manner.

Catchment Opportunities and Constraints Key catchment issues, which are identified based on a combination of catchment characteristics (e.g. designated areas requiring protection or enhancement), government policy/targets (e.g. Defra ‘High Level Targets’, 1999) and/or catchment initiatives (e.g. existing local authority strategies). Catchment policies/measures should aim to ‘take account of constraints’ and ‘promote opportunities’ through the CFMP appraisal framework (economic, environmental and technical). Designated sites have Water Level Management Plans (WLMPs) that set out water level management needs in certain parts of the catchment and some floodplain areas have nature conservation or heritage interest that benefit from increased incidence of flooding.

Catchment Policies The outputs of the CFMP, which are the stated policies for flood risk management within a defined flood risk area, based on the generic catchment policies.

Coastal Squeeze The term 'coastal squeeze' is applied to the situation where the coastal margin is squeezed between the fixed landward boundary (artificial or otherwise).

Communication Plan A plan that sets out the CFMP consultation programme, and specific arrangements for internal (Environment Agency) and external consultation.

Confluence The point where two or more streams or rivers meet.

Consultation Group A group of consultees representative of the stakeholders who should be consulted on the CFMP as agreed with the Project Board. The Consultation Group should be identified within the Communication Plan.

Environment Agency 181 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Conservation Areas Designated by Local Authorities as any area of ‘special architectural or historic interest’, whose characteror appearance is worth protecting or enhancing. This ‘specialness’ is judged against local and regionalcriteria, rather than national importance, as is the case with listed buildings. For further information referto English Heritage website: http://www.english heritage.org.uk/

Conveyance (in relation to water) The systematic and intentional flow or transfer of water from one point to another

County Wildlife Site (CWS) / Site of Nature Conservation Importance (SNCI) County Wildlife Sites and SNCIs are designated at a local level and are included within local or unitary development plans for their regional or local conservation interest. However, they have no statutory protection. Further information on these designations can be found at http://www.naturenet.net/status/sinc.html

Countryside Character Areas Countryside Character Areas are sub-divisions of England, each with a broadly cohesive countryside character. There are 159 Character Areas in England on which strategies for both ecological and landscape issues can be based. The Countryside Agency (soon to be Natural England) extensively uses this framework to describe and shape objectives for the countryside, for its planning and management.

Countryside and Rights of Way Act (CRoW) The Countryside and Rights of Way (CRoW) Act 2000 came into force on 30 January 2001. The Act applies in England and Wales and has five parts: 1. Access to the Countryside 2. Public Rights of Way and Road Traffic 3. Nature Conservation and Wildlife Protection 4. Areas of Outstanding Natural Beauty 5. Miscellaneous and Supplementary Of these, Part 3 is the most relevant in terms of catchment flood management as it gives biodiversity a statutory basis, revises SSSI notification procedures, greatly increases protection for SSSIs and strengthens the advisory role of EN / CCW, increases the scope of some wildlife offences and increases penalties. For further information refer to Her Majesties Stationary office website: http://www.hmso.gov.uk/acts/acts2000/20000037.htm

Critical Ordinary Watercourses (COWs) Stretches of non-main watercourse that have been defined as critical in terms of flood risk management through consultation between the Environment Agency and Local Authorities.

Culvert A covered channel or pipeline which is used to continue a watercourse or drainage path under an artificial obstruction.

Damages An amount of money used to compensate for loss or injury to person or property.

Defra Department for Environment, Food and Rural Affairs, the department of central government responsible for flood management policy in England.

Designated Historic Features / Assets English Heritage (EH) is the national body responsible for identifying and protecting historic buildings by recommending the most important of them for “listing”. There are three grades of listed buildings depending on their relative importance: • Grade I buildings are those of exceptional interest; • Grade II* buildings are particularly important buildings of more than special interest; and • Grade II buildings are of special interest, warranting every effort to preserve them.

Environment Agency 182 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Local authorities have the power to designate Conservation Areas in any area of “special architectural or historic interest”, whose character or appearance is worth protecting or enhancing. These qualities are judged against local and regional criteria, rather than national importance, as is the case with listing buildings. In England the prime sources of information on recorded archaeological remains will be the Sites and Monuments Records (SMR) and the National Monuments Record (NMR). The SMR should contain information about all known archaeological remains. For further information refer to the English Heritage website: http://www.english-heritage.org.uk

Digital Elevation Model (DEM) A digital elevation model is a representation of the topography of an area and gives the elevation of the upper surface whether it is the ground, vegetation or a building.

Digital Terrain Model (DTM) A digital terrain model is a representation of the ground surface with buildings and vegetation removed. With airborne techniques automated filters have been developed which can detect buildings and remove them and fill the gap with interpolated data.

Discounted In finance, discounting is the process of finding the current value of an amount of cash at some future date, and along with compounding cash form the basis of time value of money calculations. The discounted value of a cash flow is determined by reducing its value by the appropriate discount rate for each unit of time between the time when the cashflow is to be valued to the time of the cash flow. Most often the discount rate is expressed as an annual rate.

Drift Geology In geology, drift is transported rock debris overlying the solid bedrock. The transport mechanisms can include rivers and glaciers. Glacial drift is a general term for the coarsely graded sediments of glacial origin. In the UK the term drift is commonly used to describe any deposits of quaternary age.

DTLR Department for Transport, Local Government and the Regions. The former department of central government responsible for policy on planning and other issues. Now replaced by the Department for Communities and Local Government (DCLG) (formerly known as the Office of the Deputy Prime Minister (ODPM)).

East of England Plan - Draft revision to the Regional Spatial Strategy (RSS) for the East of England The RSS sets out a strategy to guide planning and development in the East of England to the year 2021. It covers economic development, housing, the environment, transport, waste management, culture, sport and recreation, mineral extraction and implementation. The RSS aims to improve the quality of life, and sets out proposals which will influence where we choose to work and live and how we move about the region. It also seeks to address issues such as social exclusion, the need for regeneration and the impact of climate change.

East of England Regional Assembly (EERA) The East of England Regional Assembly (EERA) exists to promote the economic, social and environmental well-being of the region. It consists of a partnership of elected representatives from the 54 local authorities in the East of England and appointed representatives from social, economic and environmental interests (Community Stakeholders).

Ecology/Ecological How living things relate to their environment and surroundings.

Environment Agency Non-departmental public body responsible for the delivery of government policy relating to the environment and flood risk management in England and Wales.

Environment Agency 183 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007

Environment Agency Vision Our ‘vision’ for the environment and a sustainable future is: ‘A healthy, rich and diverse environment in England and Wales, for present and future generations’ To achieve the targets that will make the ‘vision’ a reality we have identified nine key ‘themes’ or ‘frameworks for change’ through which it will work for a more sustainable future. 1. A better quality of life: We will work with all sectors to enhance the quality of the environment and the services it provides – for business, anglers, the boating community and other users of the waterways, farmers, planners and all sections of the community. 2. An enhanced environment for wildlife: We will ensure that its activities and those it authorises do not threaten key species and habitats; 3. Cleaner air for everyone 4. Improved and protected inland and coastal waters: We will work to clean up polluted waters and to reduce the risk of further pollution; 5. Restored protected land with healthier soils. 6. A ‘greener’ business world 7. Wiser sustainable use of natural resources 8. Limiting and adapting to climate change 9. Reducing flood risk: We will improve flood defences and information on flood risks For further information refer to our website http://www.environment-agency.gov.uk

Environmentally Sensitive Areas (ESA) ESA schemes were introduced by the Ministry of Agriculture, Fisheries and Food (MAFF; predecessor to Defra) in 1987 and are designated under the provisions of sections 18 and 19 of the 1986 Agriculture Act and Environmentally Sensitive Area (Stage II) Designation (Amendment)(No2) Order 2001. They were governed by Defra and offered incentives (on a 10 year agreement with a 5 year break clause) to encourage farmers to adopt agricultural practices which would safeguard and enhance parts of the country of particularly high landscape, wildlife or historic value. These schemes have now been superseded by the Environmental Stewardship Scheme. Further details can be found on Defra’s website: http://www.defra.gov.uk/erdp/schemes/esas/default.htm

Eutrophication The enrichment of waters by inorganic plant nutrients causing changes such as increased production of algae and/or other aquatic plants affecting the quality of the water.

Eutrophic Sensitive Areas Eutrophic Sensitive Areas require the installation of nutrient removal at all sewage treatment works (STW) serving a population of more than 10,000 by 2004.

Farming & Wildlife Advisory Group Formed in 1969, FWAG exists to provide farmers, landowners and our other clients with the best opportunity for environmental gain through cost effective, quality solutions.

Evaporation/Transpiration The process where a liquid (water) changes into a gas (water vapour) / Loss of water through evaporation by plants.

FEHCALC Spreadsheet designed by John Packman from the Centre for Ecology and Hydrology, Wallingford to calculate peak flows, based on the rainfall-run-off methodology detailed in the Flood Estimation Handbook. Procedures are outlined within the MDSF guidelines.

Flood Estimation Handbook (FEH) See ‘Flood Defence’

Flood Defence A structure (or system of structures) for the alleviation of flooding from rivers or the sea. Flood Estimation Handbook (FEH) provides the current methodologies for estimation of flood flows for the UK.

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Floodline Warnings Direct (FWD) The Environment Agency’s flood warning dissemination system. Floodline Warnings Direct is an internet based telecommunications system which disseminates flood warnings using a variety of media channels, i.e. telephone, fax, sms and email.

Floodplain Any area of land over which water flows or is stored during a flood event or would flow but for the presence of flood defences.

Flood Map The Flood Map is the Environment Agency's public face map for floodplain information. It shows the flood extents, which ignore defences, the location of raised defences, and the area benefiting from defences. Available on the Environment Agency's website, it also provides information on the likelihood of flooding to general areas of land.

Flood Risk The level of flood risk is the product of the frequency or likelihood of the flood events and their consequences (such as loss, damage, harm, distress and disruption).

Flood Risk Management The activity of modifying the frequency or consequences of flooding to an appropriate level (commensurate with land use), and monitoring to ensure that flood risks remain at the proposed level. This should take account of other water level management requirements, and opportunities and constraints. It is not just the application of physical flood defence measures.

Flood Zones Flood Zones have been produced by the Environment Agency in response to Planning Policy Guidance (PPG 25) and to provide planning authorities with quality assured flood risk data. The zones show the area at risk if there were no defences and are classified as follows:

Zone 1 - annual probability of flooding of less than 1000:1 (0.1%) Zone 2 - annual probability of flooding between 1000:1 (0.1%) and 100:1 (1.0%) for fluvial flooding or 200:1 (0.5%) for coastal flooding. Zone 3 - annual probability of flooding greater than or equal to 100:1 (1.0%) for fluvial flooding or greater than or equal to 200:1 (0.5%) for coastal flooding

Fluvial Pertaining to a watercourse (river or stream).

Freshwater Fisheries Directive Designation EC Directive 78/659/EEC on the Quality of Fresh Waters Needing Protection or Improvement in order to Support Fish Life (‘The Freshwater Fish Directive’) aims to protect and improve water quality and forms part of the Environment Agency’s water quality monitoring programme. Under the Directive, the UK Government was required to designate two categories of water: those suitable for salmonids (waters that have the potential to support fish of the family Salmonidae, mainly salmon and trout but also grayling) and those suitable for cyprinids (from the family Cyprinidae plus pike, perch and eel). The Directive sets standards to safeguard freshwater fisheries, mainly relating to the quality of the water, and requires that certain designated stretches of water meet these standards in order to enable fish to live or breed. For further information please consult our website: http://www.environment-agency.gov.uk/

Geographical Information System (GIS) A GIS is a computer-based system for capturing, storing, checking, integrating, manipulating, analysing and displaying data that are spatially referenced.

Geomorphology The sediment erosion, deposition of transport processes that create the topography and shape of a river and its floodplain.

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Grey water Household grey water is the water from sinks, baths, the washing machine i.e. all used household water excluding toilet water.

Groundwater Water occurring below ground in natural formations (typically rocks, gravels and sands).

Habitats Directive In 1992 the European Community adopted Council Directive 92/43/EEC on the Conservation of natural habitats and of wild fauna and flora (EC Habitats Directive). The main aim of the EC Habitats Directive is to promote the maintenance of biodiversity by requiring Member States to take measures to maintain or restore natural habitats and wild species at a favourable conservation status, introducing robust protection for those habitats and species of European importance. In applying these measures, Member States are required to take account of economic, social and cultural requirements and regional and local characteristics. For further information please consult our website: http://www.environment-agency.gov.uk/

Headwaters The source of a river may be a lake, a marsh, a spring, or a collection of headwaters. Headwaters are small streams that create the river.

Highest Astronomic Tide (HAT) The highest tide that can occur due solely to the arrangement of the moon, sun and planets.

Historic Flood Map The Historic Flood Map shows the mapped extents of known historical flooding.

Hydrograph Hydro- meaning water, and -graph meaning chart. • a record through time of discharge (flow) in a river, or • a record through time of water level in an aquifer, measured in a well.

Hydrological Model Estimates the flow in a river arising from a given amount of rainfall falling into the catchment. Such models typically account for factors such as catchment area, topography, soils, geology and land use.

Inception Report Provides a detailed description of the work undertaken during the CFMP Inception phase. This includes a summary of catchment data collection and preliminary understanding of the main issues to be considered for effective flood risk management during subsequent phases of the CFMP process.

Indicative Floodplain Maps (IFMs) Maps showing the Environment Agency’s best estimate of the extent of the floodplain. These cover all Main Rivers and some ordinary watercourses. The floodplain is defined as the area having a 1% annual risk of fluvial, or a 0.5% annual risk tidal inundation. Defended areas are also shown. These maps are sometimes referred to as Section 105 maps. These maps were superseded by the flood map in October 2004.

Indicative Standard of Protection The range of level of protection to be considered for flood defences, based upon the use of the land being protected. They do not represent any entitlement to protection or minimum level to be achieved.

Interferometric Synthetic Aperture Radar (IFSAR) Interferometric Synthetic Aperture Radar is a comparison of two or more radar images collected at slightly different geometries. This process extracts phase differences caused by changes in elevation relative to a reference point, producing Digital Terrain Elevation data. The technique is able to collect large areas of high-resolution data quickly and affordably no matter the conditions, night or day.

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Internal Drainage Board (IDB) IDBs are long established bodies operating predominantly under the Land Drainage Act 1991 and have permissive powers to undertake work to secure drainage and water level management of their districts and undertake flood risk management works on ordinary water courses within their districts (i.e. watercourses other than ‘main river’). Much of their work involves the maintenance of rivers, drainage channels and pumping stations, facilitating drainage of new developments and advising on planning applications. They also have statutory duties with regard to the environment and recreation when exercising their permissive powers.

Inundation To cover with water - especially flood waters.

Landscape Character Areas see ‘Natural Area Profiles’.

Land Use Various designations of activities, developments, cropping types, etc for which land is used.

Land Management Various forms of activities relating to agricultural, forestry, etc practice.

LiDAR Light Detection and Ranging (LIDAR) is an airborne mapping technique, which uses a laser to measure the distance between the aircraft and the ground.

Local Authority Development Plans These statutory land development plans generally cover a 10-year period from the date of their adoption. However, the local authorities currently review these plans on a 5- yearly basis. A District Council and a Unitary Authority will produce a Local Plan and a County Council produce a Structure Plan. A Structure Plan guides the Local Plans of several District Councils.

Local Biodiversity Action Plan (LBAP) A local agenda (produced by the local authority) with plans and targets to protect and enhance biodiversity and achieve sustainable development. We are committed to Biodiversity Action Plans and work with central government (Rio Earth Summit, 1992) to realise LBAP objectives.

Local Environment Agency Plan (LEAP) An Environment Agency non-statutory plan based on the river basin (or sub-catchments or groups of smaller catchments) providing environmental baseline information and actions/objectives for that river basin (largely superseded the National Rivers Authority’s Catchment Management Plans (CMPs)).

Local Nature Reserve (LNR) Local Nature Reserves are designated under the National Parks and Access to the Countryside Act 1949 by Local Authorities (which must have some legal control over the site) in consultation with English Nature for their locally important wildlife or geological features. They are generally intended for education and amenity in addition to conservation. For further information refer to the English Nature website http://www.english-nature.org.uk/special/lnr/lnr_search.asp

Ministry of Agriculture, Fisheries and Food (MAFF) The former Ministry of Agriculture, Fisheries and Food - The functions of MAFF have been taken over by the Department for Environment, Food and Rural Affairs (Defra)

Mean High Water Springs (MHWS) The average of the Spring Tides which occur every two weeks.

Main River Watercourses defined on a ‘Main River Map’ designated by Defra. We have permissive powers to carry out flood defence works, maintenance and operational activities for Main Rivers only. Responsibility for maintenance however rests with the riparian owner (the land owner).

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Mire Type of bog or form of wetland.

Modelling and Decision Support Framework (MDSF) The Modelling and Decision Support Framework - a GIS based decision support tool developed specifically to assist the CFMP process through automation of parts of the analysis. Further information can be found at:http://www.mdsf.co.uk

National Farmers Union (NFU) The National Farmers' Union represents the farmers and growers of England and Wales. Its central objective is to promote successful and socially responsible agriculture and horticulture, while ensuring the long term viability of rural communities.

Morphology The study of form or shape e.g. the shape of river channels and how this changes overtime by processes of erosion and sedimentation.

National Nature Reserve (NNR) NNRs have been established to protect the most important areas of wildlife habitat and geological formations in Britain, and as places for scientific research. They are either controlled by Natural England or held by approved bodies such as Wildlife Trusts. NNRs have Reserve Management Plans that are updated every 5 years.

National Monument Record The NMR is one of the largest publicly accessible archives in the UK and the biggest dedicated to the historic environment. It is maintained by Natural England and is based at the National Monuments Record in Swindon where it has public search rooms.

National Parks The National Park Authority's duties and powers are derived from a number of Acts of Parliament and statements of Government Policy, most recently the Environment Act 1995. The Statutory purposes of National Parks, which the Authority has the duty to pursue, are: • to conserve and enhance the natural beauty, wildlife and cultural heritage of the area • to promote opportunities for the understanding and enjoyment of the area's special qualities by the public. In pursuing these purposes, we also have a duty to seek to foster the economic and social well being of the communities within the National Park, but without incurring significant expenditure in doing so. For further information please consult the National Park Authorities website: http://www.anpa.gov.uk/

National Flood and Coastal Defence Database NFCDD is a database of all flood and coastal defences, available to all Operating Authorities in England and Wales. The development of the National Flood and Coastal Defence Database (NFCDD) is a requirement under the Defra High Level Targets for flood and coastal defence operating authorities. The Environment Agency is leading the development but is working in partnership with local authorities and internal drainage boards to ensure the successful delivery of the database.

Natural Area Profiles and Landscape Character Areas (LCAs) Natural Areas are sub-divisions of England, each with a characteristic association of wildlife and natural features. There are 120 Natural Areas in England and each has a unique identity resulting from the interaction of wildlife, landforms, geology, land use and human impact. Further information about Natural Areas can be found on English Nature’s website: http://www.englishnature.org.uk/science/natural/NA_search.asp. Landscape Character Areas - The Countryside Character Initiative is a programme of information and advice on the character of the English countryside. It includes systematic descriptions of the features and characteristics that make the landscape and guidance documents on how to undertake Landscape Character Assessment. Further information about Landscape Character Areas can be found on the Countryside Agency’s website: http://www.countryside.gov.uk/

Environment Agency 188 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Non-Main River Non-Main Rivers are all watercourses not designated as Main River’s (see above). The Local Authority has permissive powers to maintain but as for Main Rivers responsibilities to do so rest with the riparian owner.

Ordnance Datum Newlyn Ordnance Datum Newlyn (ODN) is a traditional vertical coordinate system, consisting of a tide gauge datum with initial point at Newlyn (Cornwall) and a Terrestrial Reference Frame observed by spirit levelling between 200 fundamental bench marks across Britain. Each bench mark has an orthometric height only (not ellipsoid height or accurate horizontal position). This coordinate system is important because it is used to describe vertical positions of features on British maps (for example, spot heights and contours) in terms of height above mean sea level. The word Datum in the title refers, strictly speaking, to the tide gauge initial point only, not to the national levelled bench marks.

Planning Policy Guidance Note 25: Development and Flood Risk (PPG25) One of a series of Planning Policy Guidance notes (PPGs) issued by DTLR to advise local planning authorities and developers. While PPGs are not statutory, planning authorities are obliged to consider them in preparing plans and determining planning applications. PPG25, issued in July 2001, raises the profile of flood risk, which should be considered at all stages of the planning and development process and on a catchment-wide basis. It emphasises the need to act on a precautionary basis and to take account of climate change. It provides advice on future urban development in areas subject to flood risk, subjecting proposals to a sequential response (dependent on the degree of risk) and promotes the concept of Sustainable Drainage Systems (SuDS) in new development or redevelopment. PPG25 is soon to be replaced by Planning Policy Statement 25: Development and Flood Risk. For further information please refer to the Office of the Deputy Prime Ministers planning website: http://www.planning.odpm.gov.uk/ppg25/

Pre-feasibility Study A pre-feasibility study is a preliminary study to determine if a feasibility study or project appraisal is warranted.

Present Value The value at the present time of a future sum of money. It is equal to the amount that, if invested today, would grow as large as the future sum, taking into account the interest rate that it will earn.

Problem Areas Areas within the catchment identified as being at significant risk from flooding.

Probability of Occurrence The probability of a flood event being met or exceeded in any one year.

Project Team The Project Team is responsible for the production of the CFMP, and comprises key Environment Agency staff assisted by staff from consultants.

Ramsar Site The Ramsar Convention on Wetlands of International Importance, Especially as Waterfowl Habitat (1971) imposes a requirement on the UK Government to promote the wise use of wetlands and to protect wetlands of international importance. This includes the designation of certain areas as Ramsar Sites, where their importance for nature conservation (especially with respect to waterfowl) and environmental sustainability meet certain criteria. Ramsar sites receive SSSI designation under The Countryside and Rights of Way (CRoW) Act 2000 and The Wildlife and Countryside Act 1981 (as amended). Further information can be located on the RAMSAR Convention on Wetlands website: http://www.ramsar.org/

Regional Planning Guidance (RPG) Planning Guidance issued for the East Midlands and Yorkshire and Humber by the Government Office for the East Midlands Regional Assembly and the Yorkshire and Humber Assembly. Regional Spatial Strategy’s (RSS) replace RPGs.

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Regional Spatial Strategy (RSS) The replacement for Regional Planning Guidance.

Risk Assessment Considerations of the risks inherent in a project, leading to the development of actions to control, mitigate or accept them.

River Quality Objective (RQO) Rivers and canals are monitored under the requirements of the Water Resources Act, 1991. This legislation empowered the Secretary of State for the Environment and for Wales to set statutory water quality objectives to secure specific water quality standards. To meet this requirement we, as the nominated statutory body, have introduced the River Quality Objective (RQO) classification system. Currently, RQOs are classified using a River Ecosystem (RE) Classification, which is based on a set of chemical water quality parameters defined within the EC Freshwater Fish Directive (78/659/EEC). There are five river ecosystem classes, from RE1 to RE5. The RQO classification system provides an indication of the water quality conditions that we would like to see in all significant rivers but there are no legal requirements directly connected with it. Instead, the RQO system provides an indication of the 'ideal' quality of waters and thereby, provides an indication of their relative importance. For further information consult our website: http://www.environment- agency.gov.uk

Royal Society for the Protection of Birds (RSPB) The RSPB is a UK charity working to secure a healthy environment for birds and other wildlife. The RSPB was founded in 1889 and since then has grown into Europe's largest wildlife conservation charity with more than a million members

Scenario A possible future situation, which can influence either catchment flood processes or flood responses, and therefore the success of flood risk management policies/measures. Scenarios will usually comprise combinations of the following: urban development (both in the catchment and river corridor); change in land use and land management practice (including future environmental designations); or climate change.

Scheduled Monuments, Scheduled Ancient Monuments To protect archaeological sites for future generations, the most valuable of them may be “scheduled”. Scheduling is the process through which nationally important sites and monuments are given legal protection by being placed on a list, or ‘schedule’. English Heritage identifies sites in England, which should be placed on the schedule by the Secretary of State for Culture, Media and Sport. The current legislation, the Ancient Monuments and Archaeological Areas Act 1979, supports a formal system of Scheduled Monument Consent for any work affecting a designated monument. Further information can be found on English Heritage’s website: http://www.english-heritage.org.uk

Section 105 Section of the Water Resources Act under which Floodplain Mapping is carried out. Level A was the initial Section 105 modelling, level B modelling has been undertaken to look at key areas in more detail. For further detail refer to Her Majesty’s Stationery office website: http://www.hmso.gov.uk/acts/acts1991/Ukpga_19910057_en_12.htm

Shoreline Management Plan (SMP) Non-statutory plans to provide sustainable coastal defence policies (to prevent erosion by the sea and flooding of low-lying coastal land), and to set objectives for the future management of the shoreline. They are prepared by us or maritime local authorities, acting individually or as part of coastal defence groups.

Social Flood Vulnerability Index (SFVI) The SFVI is a scoring calculated with the aid of MDSF to illustrate social impacts due to flooding. The social impact is based on assessing the population at risk together with an index of social vulnerability. The calculation is made on the basis of census Enumeration

Environment Agency 190 Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, January 2007 Districts, as data are available on this basis. The number of people at risk of flooding in each Enumeration District is based on the proportion of properties in each District in the flood risk area.

Site of Special Scientific Interest (SSSI) Sites of Special Scientific Interest (SSSIs) are notified under the Wildlife and Countryside Act 1981 (as amended) and the Countryside and Rights of Way (CRoW) Act 2000 for their flora, fauna, geological or physiographical features. Notification of a SSSI includes a list of operations that may be harmful to the special interest of the site. The Wildlife and Countryside Act 1981 (provisions relating to SSSIs) has been replaced by a new Section 28 in Schedule 9 of the CROW Act. The new Section 28 provides significantly enhanced protection for SSSIs. All cSACs, SPAs and Ramsar sites are designated as SSSIs. For further information refer to English Nature’s website: http://www.englishnature.com.

Soil Moisture Deficit Plants will extract water from the soil when there is insufficient rain to match evaporation or transpiration, creating a soil moisture deficit. This deficit increases until there is further rainfall to refill the available water capacity.

Special Area of Conservation (SAC), Candidate Special Area of Conservation (cSAC) An internationally important site for habitats and/or species, designated as required under the EC Habitats Directive. A cSAC is a candidate site, but is afforded the same status as if it were confirmed. SACs are protected for their internationally important habitat and non-bird species. They also receive SSSI designation under the Countryside and Rights of Way (CRoW) Act 2000; and the Wildlife and Countryside Act 1981 (as amended). For further details refer to the Joint Nature Conservation Committee website http://www.jncc.gov.uk

Sites of Community Importance (SCIs) Sites on Community Importance are those which contribute significantly to the maintenance or restoration of Favourable Conservation Status in the biogeographic region in which it occurs. The sites have been adopted by the European Commission from a list of cSACs identified by Member States but not yet formally designated by the government of each country.

Special Protection Area (SPA), Proposed Special Protection Area (pSPA) A site of international importance for birds, designated as required by the EC Birds Directive. A pSPA is a proposed site, but is afforded the same status as if it were confirmed. SPAs are designated for their international importance as breeding, feeding and roosting habitat for bird species. The Government is required to consider the conservation of SPAs in all planning decisions. SPAs receive SSSI designation under the Countryside and Rights of Way (CRoW) Act 2000 and the Wildlife and Countryside Act 1981 (as amended). For further details refer to the European Commission: website: http://europa.eu.int/ and the Joint Nature Conservation Committee website: http://www.jncc.gov.uk/ukspa/sites/spalistA-C.htm

Steering Group The Steering Group oversees the production of the CFMP, and is expected to comprise key Environment Agency staff together with staff from other operating authorities or major stakeholders, where appropriate.

Strategy Plan A long-term (usually 50 years or more) documented plan for river or coastal management, including all necessary work to meet defined flood and coastal defence objectives for the target area. A Strategy Plan is more detailed and usually covers a smaller area than a CFMP.

Strategic Environmental Assessment (SEA) The application of environmental assessment to earlier, more strategic, tiers of decision-making policies, plans and programmes. For further detail please consult Defra’s website: http://www.defra.gov.uk

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Strategic Flood Risk Assessment (SFRA) A broad scale assessment of flood risk carried out by a unitary authority or district council. Such documents are drafted so that proposed developments can be quickly appraised to Planning Policy Guidance.

Structure Plan A statutory plan comprising part of the Development Plan that is prepared by County Councils or a combination of unitary authorities, containing strategic policies that cover key planning issues over a broad area and provide a framework for local planning, including Unitary Development Plans (UDPs) and the Local Plan/Local Development Frameworks.

Surface Water Water in rivers, estuaries, ponds and lakes.

Sustainability A concept which deals with mankind’s impact on the environment through development. Sustainable development is ‘development which meets the needs of the present without compromising the ability of future generations to meet their own needs’ (Brundtland Report, 1987). The degree to which flood risk management options avoid tying future generations into inflexible or expensive options for flood defence. This usually includes consideration of other defences and likely developments, as well as processes within a catchment. It should also take account, for example, of the long-term demands for non-renewable materials.

Sustainable Drainage Systems (SuDs) A sequence of management practices and control structures designed to drain surface water in a more sustainable fashion than some conventional techniques (may also be referred to as sustainable drainage techniques).

Telemetry The means by which a data signal is transferred to a remote control centre by the telephone network.

Time to Peak (Tp) The time, in hours, between the centroid of a rainfall event and the peak of the resulting flood wave at a particular location. A short time to peak generally indicates a ‘flashy’ catchment where floods occur rapidly after rainfall. Longer times to peak are characteristic of lowland catchments or those with attenuating water bodies.

Unitary Development Plan (UDP) A statutory plan produced by unitary authorities, comprising part of the Development Plan and written in two parts: Part I – a written statement which contains the authority’s general policies for their area; Part II – both a written statement and an ordnance plan, describing the policies in detail and illustrating them on a geographical basis. A UDP replaces Local Plans within unitary authorities.

Water Framework Directive (WFD) European Community Directive (2000/60/EC) on integrated river basin management. The WFD sets out environmental objectives for water status based on: ecological and chemical parameters; common monitoring and assessment strategies; arrangements for river basin administration and planning; and a programme of measures in order to meet the objectives. For further detail consult the European Commission website: http://europa.eu.int

Water Level Management Plan (WLMP) A document setting out water level management requirements in a defined floodplain area (usually a SSSI), which is designed to reconcile different requirements for drainage.

Whole Life Cost A systematic approach balancing capital with revenue costs to achieve an optimum solution over a project’s whole life.

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Wildlife and Countryside Act The Wildlife and Countryside Act 1981 (as amended) is the principal mechanism for the legislative protection of wildlife in Great Britain. The Act is divided into four parts: Part I is concerned with the protection of wildlife, Part II relates to the countryside and national parks (and the designation of protected areas), Part III covers public rights of way, Part IV deals with miscellaneous provisions of the Act. The designation of protected species is included in Schedules 1, 5 and 8 of the Act, which list protected birds, protected animals and protected plants, respectively.

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References

Admiralty Tide Tables 2006

A Draft Management Plan for the Wash Estuary System (February 2004)

Bedfordshire and Luton Local Biodiversity Action Plan (undated)

Bedfordshire and Luton Structure Plan 2016 Deposit Draft (November 2002)

Buckinghamshire and Milton Keynes Local Biodiversity Action Plan (2000-2010)

Buckinghamshire County Structure Plan 1991-2011 Deposit Draft (March, 1996)

Cambridgeshire and Peterborough Structure Plan 2003

Cambridgeshire Local Biodiversity Action Plan (undated)

Catchment Flood Management Plans Volumes 1 & 2 Guidance, July 2004, Environment Agency/Defra/Welsh Assembly Government

CEH Wallingford: Heavily Modified Waters in Europe: Case study on the Great Ouse Catchment. Submitted to Environment Agency and Defra

East of England Plan, Draft Revision to the Regional Spatial Strategy 14 (East of England) (December 2004)

Extreme Tide Levels for use in Section 105 Surveys Environment Agency Anglian Region, January 1999, Posford Duvivier

FCDPAG3 Flood and Coastal Defence Project Appraisal Guidance – Economic Appraisal, 1999, MAFF

Milton Keynes and South Midlands Sub-Regional Strategy (March 2005)

Modelling Decision and Support Framework (MDSF) Procedures Version 3.0, Environment Agency, 2004

Norfolk Local Biodiversity Action Plan (undated)

Norfolk Structure Plan (1999)

Northamptonshire County Structure Plan 1996-2016 (March 2001)

Northamptonshire County Structure Plan 1996-2016 (undated)

Regional Planning Guidance for East Anglia to 2016 (RPG 6) (November 2000)

Regional planning guidance for the south east to 2016 (RPG 9) (December 2000)

Replacement Buckinghamshire Structure Plan 2001-2016 Deposit Draft (September 2003)

Suffolk Local Biodiversity Action Plan (2000)

Suffolk Structure Plan 2001

The East of England Regional Habitat Biodiversity Targets (2004)

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The North West Norfolk Catchment Abstraction Management Strategy (CAMS) (March 2005)

The Upper Ouse and Bedford Ouse Catchment Abstraction Management Strategy (CAMS) (March 2005)

The Wash – Which Way Now? A Draft Management Plan for the Wash Estuary System (February 2004)

The Wash Shoreline Management Plan (1996)

UKCIP 02 Scientific Report - Climate change scenarios for the United Kingdom. (April 2002)

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