Preliminary Flood Risk Assessment (PFRA) Final guidance

Transcription

1 07/12/2010 Preliminary Flood Risk Assessment (PFRA) Final guidance Report GEHO1210BTGH-E-E i

2 07/12/2010 We are The Environment Agency. It's our job to look after your environment and make it a better place for you, and for future generations. Your environment is the air you breathe, the water you drink and the ground you walk on. Working with business, Government and society as a whole, we are making your environment cleaner and healthier. The Environment Agency. Out there, making your environment a better place. Published by: Environment Agency Rio House Waterside Drive, Aztec West Almondsbury, Bristol BS32 4UD Tel: enquiries@environmentagency.gov.uk Environment Agency All rights reserved. This document may be reproduced with prior permission of the Environment Agency. Further copies of this report are available from our publications catalogue: Hhttp://publications.environmentagency.gov.ukH or our National Customer Contact Centre: T: E: Henquiries@environmentagency.gov.ukH. ii

3 Executive summary This guidance helps Lead Local Flood Authorities (LLFAs) in managing local flood risk under the Flood Risk Regulations (the Regulations). It updates and replaces the living draft guidance which the Environment Agency issued in June It also supports Defra and WAG guidance on selecting and reviewing Flood Risk Areas. The Regulations implement the European Floods Directive. This provides a consistent approach to managing flood risk across Europe, through a six year planning cycle based on a four stage process of: undertaking a Preliminary Flood Risk Assessment (PFRA), identifying Flood Risk Areas, preparing flood hazard and risk maps and preparing flood risk management plans. This guidance focuses on the first two stages. Under the Regulations, and in line with responsibilities under the Flood and Water Management Act (the Act), LLFAs are responsible for undertaking a PFRA for local sources of flood risk, primarily from surface runoff, groundwater and ordinary watercourses. The PFRA is a high level screening exercise which involves collecting information on past (historic) and future (potential) floods, assembling it into a preliminary assessment report, and using it to identify Flood Risk Areas which are areas where the risk of flooding is significant. The following table summarises the main steps. 1 Set up governance & develop partnerships 2 Determine appropriate data systems 3 Collate information on past & future floods and their consequences 4 Determine locally agreed surface water information 5 Complete preliminary assessment report document 6 Record information on past & future floods with significant consequences in spreadsheet 7 Illustrate information on past and future floods 8 Review indicative Flood Risk Areas 9 Identify Flood Risk Areas 10 Record information including rationale The PFRA is based on existing and available information and should bring together information from national and local sources including the Flood Map for Surface Water and Strategic Flood Risk/Consequence Assessments. Information from the PFRA process will also feed into other assessments including local strategies under the Act. It is important to remember that the Regulations are not the only mechanism for managing local flood risk, or the main route for funding. In many cases the local strategy is likely to be a more appropriate and quicker route to manage risk in an area. We have used guidance from Defra and WAG and nationally available datasets to determine indicative Flood Risk Areas. LLFAs should review these areas using local information in the preliminary assessment report to determine their proposed Flood Risk Areas. This guidance sets out how the indicative Flood Risk Areas can be changed based on local evidence. LLFAs need to submit their preliminary assessment report to us by 22 June The report comprises a pdf document, a spreadsheet and, if a Flood Risk Area has been identified, a GIS layer. The European Commission s reporting process sets out minimum requirements to be met by Member states when producing a PFRA and this guidance incorporates these. The Environment Agency have a role to review, collate and publish the outputs. iii

4 Contents Executive summary iii Contents iv 1 Introduction Aim of this guidance Introduction to the Flood Risk Regulations River basin districts Roles and responsibilities Sources of flooding Links to other legislation and documents Flood and Water Management Act Surface water management plans Development and flood risk PPS25 and TAN Other relevant plans Strategic Environmental Assessment Directive Inspire Directive Cross border issues 6 2 Preliminary Flood Risk Assessment Introduction Exceptions Governance and partnership working Information sharing 10 3 Preliminary assessment report Introduction Sources, pathways and receptors Collating flood risk information 11 Probability and consequences 12 National information about past and future floods 12 Local information about past and future floods Information about past floods Surface runoff, groundwater and ordinary watercourses 13 National information about past floods 13 Local information about past floods Other sources of flooding Consequences of past floods Interactions with other sources of flooding 15 iv

5 3.5 Information about future floods Surface runoff 16 National information about future floods 16 Local information about future floods 16 Locally agreed surface water information Groundwater 17 National information about future floods 17 Local information about future floods Ordinary watercourses 18 National information about future floods 19 Local information about future floods Other Sources of flooding Interactions with other sources of flooding Consequences of future floods 20 National Receptor Dataset 20 Human health 20 Economic activity 21 Environment Climate change and long term developments 22 Climate change 22 Long term developments 22 4 Identifying Flood Risk Areas Aims and objectives Significance criteria Indicative Flood Risk Areas Local considerations Amending Flood Risk Areas Using the significance criteria 25 5 Review and publication The purpose of review Local Authority review Environment Agency review Modification and settling differences of opinion Review criteria Publication and submission to Europe 29 Glossary 30 v

6 1 Introduction The PFRA is a high level exercise based on existing and available information. It should bring together information from a number of available sources such as the Environment Agency s national information (such as the Flood Map for Surface Water) and existing local products such as Strategic Flood Risk Assessments (SFRAs) and Surface Water Management Plans (SWMPs) in England and Strategic Flood Consequence Assessments (SFCAs) in Wales. 1.1 Aim of this guidance This guidance aims to help Lead Local Flood Authorities (LLFAs) meet their duties to manage local flood risk and deliver the requirements of the Flood Risk Regulations. It updates and replaces the living draft guidance which the Environment Agency issued in June 2010 and supports Defra and WAG guidance on selecting and reviewing Flood Risk Areas. This guidance replaces the living draft and provides our final guidance to LLFAs on the structure and content of PFRAs and on determining Flood Risk Areas. The main changes in the guidance are: change in focus from immediate actions to provision of more technical detail on how to complete the assessment, and what the final outputs look like, inclusion of information on identifying significant Flood Risk Areas. 1.2 Introduction to the Flood Risk Regulations The Flood Risk Regulations 2009 (the Regulations) implement the requirements of the European Floods Directive. The aim of the Directive is to provide a consistent approach to managing flood risk across Europe. It establishes four stages of activity within a six year flood risk management cycle. Figure 1 shows the stages of the cycle, the products required and the timescale for LLFA delivery. The timescales for the publication of the outputs by the Environment Agency are also set out in the Regulations, matching those of the Directive and corresponding to the need to report to the European Commission. To meet these timescales, LLFAs will need to submit their PFRAs to us by 22 June 2011 to allow time for review, collation, publication and reporting. This guidance is focused on the first two stages in the process. The preliminary assessment report from the first stage is used to provide evidence for the second stage of identifying Flood Risk Areas. The identification of Flood Risk Areas will establish where the final two stages of preparing hazard and risk maps and flood risk management plans are required. Separate guidance will be prepared for these final two stages. The hazard and risk maps will show the likely extent, depth, direction, speed of flow and probability of possible floods and their consequences. The flood risk management plans will set out what the risk management objectives are, the measures proposed to achieve those objectives and how the measures are to be implemented. The cycle starts again in 2016, so it is important to ensure that information is maintained and kept up to date for future use and to support other flood risk assessments (such as SWMPs, SFRAs / SFCAs) and as part of local strategies. In the next cycle, more information will be mandatory for floods that occur after 22 Dec

7 Figure 1 Stages of the Flood Risk Regulations 1 Preliminary Flood Risk Assessment Preliminary Assessment Report for each LLFA Deadline 22/06/ Identify Flood Risk Areas Where the risk of flooding is significant Deadline 22/06/ Prepare Flood Hazard and Flood Risk Maps For Flood Risk Areas Deadline 22/06/2013 Develop Flood Hazard and Risk Maps 4 Prepare Flood Risk Management Plans For Flood Risk Areas Deadline 22/06/ River basin districts The Directive requires reporting at the scale of a river basin district. The Regulations require the Environment Agency to prepare Preliminary Assessment Maps for the river basin districts. These have been generated for the eleven river basin districts that are partly or fully in England and Wales. Information on the maps can be found in annex 4. They show river basin district boundaries, the coastline, land use and topography. LLFAs do not need to do anything further with these maps. We will collate information from LLFAs to report at a river basin district level. 1.3 Roles and responsibilities The Regulations define new responsibilities for flood risk management based on the recommendations of the Pitt Review. These are consistent with the Flood and Water Management Act. Boxes 1 and 2 summarise the key terminology and responsibilities. Box 1 Flood risk management responsibilities Environment Agency the competent authority for managing risk from main rivers, the sea and large raised reservoirs. Lead Local Flood Authority responsible for managing local flood risk in particular from ordinary watercourses, surface runoff and groundwater. In relation to England, the LLFA is the unitary authority for the area, or if there is no unitary authority, the county council. In relation to Wales, the LLFA is the county council or the county borough council. Internal Drainage Boards (IDBs) are not responsible for producing outputs under the Regulations, but in many parts of the country they play an important part in local flood risk management. They are independent bodies responsible for land drainage operating predominantly under the Land Drainage Act They may also undertake flood defence works on ordinary watercourses within their district Sources of flooding LLFAs are responsible for assessing risk from sources of flooding other than main rivers, the sea and reservoirs. In particular this includes surface runoff, groundwater and ordinary watercourses and any interaction these have with drainage systems and other sources of flooding including sewers. The interaction of flooding from main rivers, the sea and reservoirs with local sources will need to be taken into account. An example might be where an ordinary watercourse floods when a main river backs up. 2

8 Box 2 Sources of flooding Main river watercourses legally defined and marked as such on the main river map. Generally they are larger streams or rivers, but can be smaller watercourses. The Environment Agency has legal responsibility for them. The sea coastal flooding can occur as a result of a combination of high tides and stormy conditions. If low atmospheric pressure coincides with a high tide, a tidal surge may cause serious flooding. We are responsible for managing risk from sea flooding. Reservoirs we are responsible for regulating large raised reservoirs under the Reservoirs Act We currently regulate reservoirs over 25,000 m³ in capacity. This will reduce to10,000m³ by the commencement of provisions of the Flood and Water Management Act. Reservoirs below this size are unlikely to present significant flood risks in the context of the Regulations. On this basis there is no need for LLFAs to include information on reservoirs in their PFRAs. Local flood risk flood risk from sources other than main rivers, the sea and reservoirs, principally meaning surface runoff, groundwater and ordinary watercourses. Surface runoff rainwater (including snow and other precipitation) which is on the surface of the ground (whether or not it is moving), and has not entered a watercourse, drainage system or public sewer. Flooding from surface runoff is sometimes called pluvial flooding. Note that the term 'surface water' is used generically to refer to water on the surface. Groundwater water which is below the surface of the ground and in direct contact with the ground or subsoil. It is most likely to occur in areas underlain by permeable rocks, called aquifers. These can be extensive, regional aquifers, such as chalk or sandstone, or may be more local sand or river gravels in valley bottoms underlain by less permeable rocks. Ordinary watercourse any river, stream, ditch, cut, sluice, dyke or non-public sewer which is not a main river. Artificial water bearing infrastructure includes reservoirs (see above), sewers, water supply systems and canals. Flooding from canals that are non main river should be included in a PFRA. LLFAs do not need to assess flooding from sewers, unless wholly or partly caused by rainwater or other precipitation entering or otherwise affecting the system. Floods of raw sewage caused solely, for example, by a sewer blockage do not fall under the Regulations. The Regulations also do not apply to floods from water supply systems, e.g. burst water mains. Other other rare sources of flooding are mentioned in the Floods Directive and include snowmelt and tsunamis. Snowmelt would count as precipitation and so could lead to surface runoff. Tsunamis are a form of flooding from the sea. It is anticipated that that the main focus of LLFAs in their PFRAs will be ordinary watercourses, surface runoff and groundwater. 1.4 Links to other legislation and documents Flood and Water Management Act The Flood and Water Management Act 2010 (the Act) aims to improve both flood risk management and the way we manage our water resources. It assigns specific responsibilities to risk management authorities for different sources of flooding. This includes a new lead role for local authorities in managing local flood risk and a strategic overview/oversight role for all flood risk in England/Wales for the Environment Agency. The Regulations are consistent with the responsibilities defined in the Act. The Act gives us responsibility for producing a national strategy for Flood and Coastal Erosion Risk Management (FCERM) for England. The strategy will build on existing approaches to FCERM and promote the use of a wider range of measures to manage risk in a co-ordinated way. We are currently consulting on the national strategy. The Welsh Assembly Government (WAG) are responsible for producing the National 3

9 Strategy for FCERM in Wales, and consulted on the development of the strategy between June and October The national strategies will provide the framework for local strategies which LLFAs are to develop and implement under the Act. These will be based on an assessment of risk which should incorporate evidence gathered as part of the PFRA process. Figure 2 illustrates this relationship in England, demonstrating the links between the national strategy, local strategies and the outputs required under the Regulations. Figure 2 FCERM planning framework The Local Government Group is writing guidance for LLFAs on how to develop local strategies. This is expected to be available in early The Regulations are not the primary mechanism for managing overall local flood risk or the main route for funding. Rather, they are intended to focus only on specific areas of the most significant risk. In many cases the local strategy is likely to be a more appropriate and quicker route to manage the risk in an area, providing a better evidence base and leverage for funding Surface water management plans In England, some LLFAs are leading and co-ordinating the production of SWMPs for key locations. They consider flood risk from surface runoff, groundwater and ordinary 4

10 watercourses and the interaction with flooding from main rivers, the sea and sewers. There are approximately 70 SWMPs currently being undertaken with Defra funding. The aim of a SWMP is to provide a greater understanding of local flood risk and to develop action plans to manage the risks. The preparation and risk assessment phases of SWMPs are directly relevant to PFRAs. The preparation phase identifies who should be involved, clarifies roles, sets aims and collates data so a risk assessment and shared understanding can be developed. The same initial activities were recommended in the PFRA living draft guidance. Information gathered for a SWMP on past and modelled future flooding can be included in the preliminary assessment report. Where the SWMP risk assessment phase has been completed, the detailed mapping can be used to review the indicative Flood Risk Areas (see section 4). The assessment of options and development of an action plan in a SWMP will assist in the preparation of flood risk management plans. Where planned SWMPs have not yet started, the PFRA will help inform their development and where more detailed work is required Development and flood risk PPS25 and TAN15 SFRAs and SFCAs are spatial planning documents, prepared by the local planning authority, which provide an evidence base to inform strategic plans and decisions on planning applications. They are likely to contain useful information relating to local flood risk which can be used in a PFRA. During the production of SFRA/SFCAs, data is normally gathered from key partners including us, water companies and IDBs. Some SFRA/SFCAs contain modelled information on predicted surface water flood risk, which may be more representative of local conditions than our national datasets (see section 3.5.1). This information should be included in the preliminary assessment report and used to inform the review of the indicative Flood Risk Areas. Conversely, SFRA/SFCAs are living documents which may be updated when new information becomes available. Data gathered in the PFRA process can be used for this purpose Other relevant plans There are a number of other plans containing useful information relating to local flood risk which can be used in a PFRA, or which a PFRA might inform. These include: Catchment Flood Management Plans (CFMPs) non-statutory plans produced by the Environment Agency. There are 77 plans covering England and Wales providing an overview of the flood risk across each river catchment and recommending ways of managing those risks now and over the next years. They consider all types of inland flooding, but not flooding directly from the sea. CFMPs will be a useful source of information on historic flooding and may provide some information on local sources of flood risk. They can also be used to identify interactions with flooding from rivers. Shoreline Management Plans (SMPs) non-statutory plans led either by Local Authorities or the Environment Agency. They provide a large scale assessment of the risks associated with coastal processes and help reduce these risks to people and the developed, historic and natural environments. They include an assessment of flooding from the sea and therefore can be used to identify interactions with local flood risks. Multi-agency Flood Plans (MAFPs) developed by Local Resilience Forums to help organisations involved in responding to a flood work together better. They may provide information on particularly vulnerable receptors not identified by national datasets. 5

11 1.4.5 Strategic Environmental Assessment Directive The Strategic Environmental Assessment (SEA) Directive (2001/42/EC) is implemented in the UK by The Environmental Assessment of Plans and Programmes Regulations 2004 (Statutory Instrument No.1633). Its objective is to provide for a high level of protection of the environment and to contribute to the integration of environmental considerations into the preparation and adoption of plans and programmes with a view to promoting sustainable development. The flood risk management plans required under the Regulations fall under the scope of the SEA Directive. Although this means SEA does not need to be formally considered until the start of the plan, it is important that the environment is taken into account from the beginning of the process. The Regulations to a large extent build in the consideration of the environment as the preliminary assessment report and the selection of Flood Risk Areas must consider significant consequences of flooding on the environment. Information collected during the PFRA can be used to develop the SEA documentation later in the process Inspire Directive The INSPIRE Directive (2007/2/EC) is implemented in the UK by the INSPIRE Regulations Its main aim is to improve the quality, consistency and accessibility of spatial data sets and services for environmental data to ensure they can be shared and integrated seamlessly into applications with minimal manual intervention. Further information can be found in guidance produced by the Association for Geographic Information The INSPIRE Directive A Brief Overview. Box 3 The general principles of INSPIRE 1. Data should be collected only once and kept where it can be maintained most effectively. 2. It should be possible to combine seamless spatial information from different sources across Europe and share it with many users and applications. 3. It should be possible for information collected at one level/scale to be shared with all levels/scales; detailed for thorough investigations, general for strategic purposes. 4. Geographic information needed for good governance at all levels should be readily and transparently available. 5. It should be easy to find what geographic information is available, how it can be used to meet a particular need, and under which conditions it can be acquired and used. INSPIRE is being implemented under UK Location, an initiative to improve the sharing and re-use of public sector location information. A set of short guides are available aimed at data managers, data providers and publishers. The tasks described in this guidance document should be carried out in accordance with the principles above. The INSPIRE Directive requires that data quality is recorded. The templates for recording past and future flooding (the preliminary assessment report spreadsheet) have taken this into consideration. 1.5 Cross border issues As the Floods Directive requires reporting at a river basin district scale there are particular arrangements for the river basin districts which cross the border between England and Scotland (the Northumbria and the Solway Tweed river basin districts). These are addressed by the Flood Risk (Cross Border Areas) Regulations We have agreed the use of this guidance in the English parts of the cross border areas with the Scottish Environment Protection Agency (SEPA). English LLFAs in the cross border areas should complete their PFRAs using this guidance and submit their 6

12 preliminary assessment reports and Flood Risk Areas to us. Our review will be informed by a Cross Border Advisory Group established to support and advise on the completion of the PFRAs. The final determination of Flood Risk Areas in the English parts of the cross border areas will be made jointly by the Secretary of State in England and Scottish Ministers. Although there are no particular cross border arrangements required between England and Wales, LLFAs should be aware of the importance of partnership working. 7

13 2 Preliminary Flood Risk Assessment The PFRA is a high level screening exercise to identify areas of significant risk. When people talk about a PFRA document, they are usually referring to a preliminary assessment report. The PFRA is the exercise, rather than the product. 2.1 Introduction The PFRA involves: collecting information on past (historic) and future (potential) floods, assembling the information into a preliminary assessment report, identifying Flood Risk Areas. LLFAs are only required to undertake a PFRA for local sources of flooding, but they should consider any interaction between local sources and flooding from the sea, main rivers or reservoirs. The table on the following page summarises the main steps which should be undertaken in developing a PFRA. It provides information on the activities, approximate timescales and resource estimates for completing the tasks. The living draft guidance published in June 2010 advocated that LLFAs make an immediate start on the first three tasks. The steps outlined represent the main technical tasks involved in developing a PFRA, in addition to which LLFAs will need to plan their internal review and approval processes (see section 5). 2.2 Exceptions The Regulations contain two options for exception which allow LLFAs to gain exemption from the requirement to prepare a PFRA. Firstly, under Regulation 33, an exception can be applied if an assessment has already been undertaken, or will be completed by 22 December 2010 enabling the identification of areas of significant flood risk. This relies on the use of a pre-existing assessment (or one prepared before December 2010) to remove the need for a new assessment. To apply the exception under Regulation 33, the assessment will need to: cover the entire LLFA area, consider local risk (in particular risk from surface runoff, groundwater and ordinary watercourses), be fit for the purpose of identifying Flood Risk Areas using Defra and WAGs guidance. Secondly, under Regulation 34 an authority may decide to produce flood hazard and risk maps together with flood risk management plans for their entire area, instead of using the PFRA to identify selected areas where maps and plans are required. While this might initially appear to be an attractive option, it is likely to be more costly and demanding overall in most cases. LLFAs should be aware of the implications, particularly the need to map and plan for the whole area to the level required. 8

14 Table 1 PFRA steps Activity Further information Suggested timeline * 1 Set up governance This was identified as an This may & develop immediate action in the living already have partnerships draft guidance. been 2 Determine appropriate data systems 3 Collate information on past & future floods and their consequences 4 Determine locally agreed surface water information 5 Complete preliminary assessment report document 6 Record information on past & future floods with significant consequences in spreadsheet 7 Illustrate information on past and future floods 8 Review indicative Flood Risk Areas 9 Identify Flood Risk Areas. 10 Record information including rationale. This was identified as an immediate action in the living draft guidance. Consider collaboration with other partners. Collation of information on past floods was identified as an immediate action in the living draft. LLFAs should use the Flood Map for Surface Water to help complete the section on future floods. Locally gree which information best represents surface water flood risk. A template is provided to assist LLFAs, however the format of the report can be flexible. It is important to complete the spreadsheet and not alter any fields as this will form the basis of the UK s reporting to the European Commission. Summary map should be provided for each source of information. Indicative areas are only an initial national assessment based on the consequences of flooding. These should be reviewed using local information in the preliminary assessment report. Flood Risk Areas must be meaningful areas for LLFAs to map and plan. Provide information in preliminary assessment report and spreadsheet and completed. This may already have been completed. End of December End January 2011 Complete by end March 2011 Complete by end March 2011 Complete by end March 2011 February 2011 February March 2011 March April 2011 Resource estimates * 2 5 days 2 5 days days 1 5 days 2 5 days 1 5 days 1 5 days 1 2 days 0 10 days 0 5 days provide spatial information. * Timescales and resources are only estimates The size of each LLFA, the scale of flood risk and the amount of work already done varies considerably. Each LLFA will need to take into account the requirements for review and their local circumstances. 9

15 The Environment Agency is exercising an equivalent exception option (Regulation 32) due to the extensive flood mapping and planning already undertaken for main rivers, reservoirs and the sea. This will be continued and expanded to meet the requirements of the Regulations. We will be producing flood hazard and risk maps and flood risk management plans for these flood risk sources for the entire river basin network. The Regulations require LLFAs to determine whether to pursue an exception by 22 December If a LLFA is proposing to apply an exception, they should write to their local Environment Agency office to confirm their approach. We do not have the power to decide whether a LLFA can use an exception option, but we can provide advice. If a LLFA is applying for exception under Regulation 33 they should provide us with a copy of their assessment by 22 December Governance and partnership working Partnership working is essential in the management of local flood risk. LLFAs should ensure that appropriate partnerships are in place, which will help the collection and sharing of data, and the effective management of the PFRA process. The importance of working together is reflected in Regulation 35 of the Regulations and Section 13 of the Act which require relevant authorities to cooperate with one another. 2.4 Information sharing A crucial part of a PFRA is the task of collating available and readily derivable data and information on flooding to provide an assessment of flood risk. Regulation 36 gives LLFAs the power to require information from other authorities. The same powers are also provided in the Flood and Water Management Act (Section14). We are currently consulting on guidance on implementing Sections 13 and14 of the Flood and Water Management Act, within the framework of our National FCERM Strategy in England consultation. The Environment Agency encourages the use of information sharing arrangements setting out a mutually agreed framework. This will enable staff who supply and receive information to plan their work more efficiently. The arrangements are not legally binding, but the information provided under them will be covered by legal licences that give terms and conditions of use. 10

16 3 Preliminary assessment report A preliminary assessment report provides a high level summary of significant flood risk, based on available and readily derivable information, describing both the probability and harmful consequences of past and future flooding. The development of new information is not required, but new analysis of existing information may be needed. The report includes: Document (template is provided in annex 1). The length will vary depending on the size of the LLFA and the amount of information available. In general it may be about pages, but it could be longer. Spreadsheet (template is provided in annex 2). It is important that records are provided in the spreadsheet and that the spreadsheet is not altered as this forms the basis for the information which will be reported to the European Commission. GIS layer of the Flood Risk Area(s). 3.1 Introduction The purpose of the preliminary assessment report under the Regulations is to provide the evidence for identifying Flood Risk Areas. The Environment Agency has included provision for the Flood Risk Areas within the preliminary assessment report template to keep the information and decisions in one document. Although not a requirement of the Regulations, a preliminary assessment report will also provide a useful reference point for all local flood risk management and so inform local strategies. 3.2 Sources, pathways and receptors The Floods Directive provides a framework to assess and manage flood risks in order to reduce adverse consequences for human health, the environment (including cultural heritage) and economic activity. Within this framework, it is important to use a consistent approach so decisions are robust and transparent. We use the source, pathway, receptor (S-P-R) model as a framework for describing flood risk. This is defined in Environment Agency / Defra R&D Project FD2302 Risk and Uncertainty Review. Figure 2 shows flooding from local sources (from Making Space for Water HA4a). Source refers to the origin of a hazard (e.g. heavy rainfall, strong winds and surge). Pathway is the connection between a particular source and a receptor that may be harmed. For example, the pathway may consist of the flood defences and flood plain between flow in a river channel (the source) and a housing development (the receptor). In local flood risk management, pathways could be flow routes like roads and gullies. Receptor is what may be harmed. For example, in the event of heavy rainfall (the source) flood water may flow across the flood plain (the pathway) and flood housing (the receptor) that may suffer material damage (the harm or consequence). 3.3 Collating flood risk information To prepare a preliminary assessment report, LLFAs should gather information about past and future floods. This should be collated from a range of available or readily derivable sources. Some information will be limited to specific locations, and available locally, whilst other information will be part of large national datasets. Whilst LLFAs may need to collate information from partners, they do not have to embark on creating local flood histories for example by researching archived local newspapers. 11

17 Figure 2 Flooding from local sources Probability and consequences Flood risk is defined by Regulation 3 as "a combination of the probability of the occurrence with its potential consequences". Information about past and future flood risk should include information about both probability and consequences. The probability of flooding should be expressed as a chance and/or probability, making reference to a time period. For example: a chance, for example... a 1 in 100 chance of flooding in any given year or a probability, for example... a 1% annual probability of flooding Return periods (for example a 100 year flood) should not be used to summarise the chance of flooding, as this can suggest that a flood may not happen again for another 100 years. The consequences of flooding can be adverse (harmful) or positive. It may include consequences for human health, the social and economic welfare of individuals and communities, infrastructure, and the environment (including cultural heritage). For PFRA, the consequences may be expressed using indicators of what could be affected by flooding, such as the number of people and the potential loss of life, the number and type of economic assets that could be damaged, or the area of agricultural land that could be affected (see section 3.5.6). National information about past and future floods Several relevant national datasets are available or imminent, and should be included in the preliminary assessment report. The following sections provide further details on what the national datasets are, why they should be used, where to access them, and how to include the information. 12

18 Local information about past and future floods Information about past and future floods will be available from a range of people and places. Flooding records may be held by parishes and councils, highways and drainage departments, water companies, fire and rescue services and other partners. Information may also be found in other documents such as SFRAs / SFCAs, SWMPs, MAFPs and CFMPs. LLFAs should check with relevant partners to get the most up to date versions of these. Strategic Flood Partnerships as outlined in the Pitt recommendations will provide a valuable starting point for collation of relevant information. 3.4 Information about past floods LLFAs should gather all available and readily derivable information on past floods (historic floods or historic flood events). LLFAs should include information on past floods even if the exact source of the flooding is not known, or if the flood was due to a combination of sources. Past floods of a kind that are not likely to occur now can be ignored, for example if drainage has been improved or defences built to reduce flooding. The reporting requirements are described below. Preliminary assessment report document - Contains a map or maps of past floods, including extent and conveyance routes, and a summary table and description of consequences (this will not be reported to the European Commission so a format can be chosen to reflect local needs). - We suggest LLFAs use the summary maps, table and description as an opportunity to provide a summary of all the information readily available on past floods, not just those with significant consequences. Although not required by the Regulations, this will be useful for local strategies. Preliminary assessment report spreadsheet - This is where more detailed information is recorded. This is only required for past floods with significant consequences, and the majority of fields are optional. - Each flood event should be reported as a row in the spreadsheet; records must be provided in this format, as they will be reported to the European Commission. LLFAs only need to record information on floods which had significant harmful consequences. Information on past floods often does not include information on the consequences, or the description is either vague or unreliable. Although no definition is provided in the legislation on what significant means, LLFAs should be mindful of the significance criteria when determining whether past floods are harmful Surface runoff, groundwater and ordinary watercourses National information about past floods 13

19 Table 2 national sources of data on past floods Source Availability Description Historic Flood Map Flood Event Outlines (FEOs) Integrated Surface Water Management Group (ISWMG) data British Hydrological Society Chronology of British Hydrological Events Historic Surface Water and Groundwater (HSWGW) Geodatabase Available from DataShare. Covers England & Wales Available from your local Environment Agency office. Covers England & Wales. Available from WAG. Covers Wales only. Available from Dundee University. Covers England & Wales This will be available from DataShare. We are aiming to release this data soon. A merged, unattributed flood extent for records of flooding from rivers, sea and groundwater only, and derived from appropriate Flood Event Outlines (details of which are provided below). It does not include point flooding records. Data is updated every three months. Some of this is also included in the Flood Map for rivers and the sea. An attributed spatial flood extent data for records of flooding from all sources, mainly captured by the Environment Agency. This information is limited and does not include point flooding records. FEOs for groundwater and surface water are included in the HSWGW Geodatabase. A compilation of historic surface water data submitted to WAG by local authorities and Welsh Water. This data has also been added to the HSWGW Geodatabase below; LLFAs wanting a standalone copy of this data can request it from WAG. This contains information which will complement existing instrumental records of rainfall, runoff, snow, etc. It covers Great Britain up to Records of exceptional precipitation and runoff events form the major part of the database, and will be of interest to hydrological practitioners and researchers when investigating the past variability of British catchment systems. A database of mainly point source data submitted to the Environment Agency by: fire services, local authorities and water companies. Information is limited as only a third of organisations approached responded to the request for data, and some of the data submitted was not included as it did not meet the required standards. It will include the national groundwater flooding database produced for Defra, the ISWMG data for Wales, and surface water and groundwater FEOs from our National Flood and Coastal Defence Database. Local information about past floods Local information about past floods will be available from a wide range of sources, as described in section 3.3. Some local information may have already been shared with the Environment Agency and may be included in the national information described above. LLFAs should be aware of this to avoid duplicating information. When compiling the HSWGW Geodatabase, some water companies have shown us their data on flooding, but have not given us permission to share their data through this database. If LLFAs do not see any records from a water company for their area they may wish to contact them directly to request information. 14

20 3.4.2 Other sources of flooding British Waterways may hold information about past flooding from canals, and where the canal is not a main river, it should be collated. British Waterways can provide a standard information pack to LLFAs. This will include the locations of canals and their associated structures, and records of overtopping and/or breach events. They can be contacted at: Water.Information@britishwaterways.co.uk. We are not aware of any other national sources of information about past floods from other sources of flooding. Local information about past floods from other sources may be available from the partners Consequences of past floods National information about past floods described in section contains limited information on the consequences of past floods and local information will vary. Local Environment Agency offices may have some information about the consequences of flooding, particularly in relation to ordinary watercourses. Where information about the consequences of past floods is missing, the National Receptor Database (see 3.5.6) could be used to estimate consequences should the flood recur. If a LLFA chooses to do this, they should refer to our guidance on how to count property numbers. This has been produced to make sure property counts are consistent and therefore comparable (available from Datashare). Alternatively, a simpler comparison using Ordnance Survey mapping may be sufficient to conclude that recurrence of a past flood would have significant consequences. If consequences are estimated, for example, by counting affected property numbers, it is important to record the method used (alongside the consequence information in the preliminary assessment report spreadsheet). If there is no information about the consequences of a past flood, it should not be considered to have had significant harmful consequences. In this case, it could be included in the summary map(s), table and description of past flooding, but should not be recorded in the preliminary assessment report spreadsheet. The spreadsheet contains fields for recording the significant consequences of each past flood for human health, the economy, the environment, and cultural heritage Interactions with other sources of flooding Flooding is often the result of water from more than one source, or water building up because another source (such as a river, or the sea) has prevented it from discharging normally. Information about past flooding will often be about an unknown source (i.e. it is not clear where the water came from), or flooding as a result of interactions between sources (in which case two or more sources may be recorded). The national information about past floods may contain information about flooding as a result of interactions between sources of flooding. However, there is no additional national information which deals solely with this issue. Local information about past floods is also likely to include information about flooding from interactions between sources of flooding. If it is clear that flooding is from two or more sources, it should be recorded. Where the source of flooding is not known, this should also be recorded. 15

21 3.5 Information about future floods If a location does not have a recorded history of past floods, it does not mean that there is no risk of flooding. To ensure flood risk is assessed objectively LLFAs should consider where flooding might occur in the future, rather than only reacting to floods in the past. This is an important principle for local flood risk assessment, because such flooding is often very localised, perhaps the result of an individual storm cloud. Future floods, or future flood risk, is otherwise known as potential flooding, or potential flood risk. Information about future floods is usually produced by computer models. The reporting requirements are described below. Preliminary assessment report document - Contains a map or maps of future floods, and a summary table and description of their consequences (this will not be reported to the European Commission so a format can be chosen to reflect local needs). - We suggest LLFAs focus this summary on their 'locally agreed surface water information', including other sources where appropriate. Preliminary assessment report spreadsheet - This is where more detailed information is recorded, including a description of the assessment method, and the consequences for human health and economic activity. - Each flood event should be reported as a row in the spreadsheet; records must be provided in this format, as they will be reported to the European Commission Surface runoff National information about future floods The Environment Agency has two national datasets showing surface water flooding available to LLFAs: Areas Susceptible to Surface Water Flooding (AStSWF) Flood Map for Surface Water (FMfSW). Information on what these datasets show, how they were created and where they are likely to be more or less representative is available to LLFAs 1. Each flood event should also be reported separately. The AStSWF dataset contains one rainfall event, with three susceptibility bandings: less, intermediate and more. The FMfSW contains two rainfall events, divided into two depth bandings: 1 in 200 rainfall and 1 in 200 rainfall deep, as well as 1 in 30 rainfall and 1 in 30 rainfall deep. The surface water maps are not designed to assess the risks from other sources of flooding. However, as these datasets use a 2D representation of the ground, they route surface runoff into channels and depressions. As flooding is dependent on topography and depressions, flooding from ordinary watercourses and groundwater may occur in the same places as flooding from surface runoff. Local information about future floods Local information may have been produced to inform a SFRA / SFCA, SWMP or another local study or plan. In many cases, studies such as these will have used the 1 What are Areas Susceptible to Surface Water Flooding, What is the Flood Map for Surface Water and 'Using surface water flood risk information are all available from DataShare. 16

22 AStSWF information. However, in a few cases, LLFAs or others may have commissioned additional flood modelling to better understand the risk from surface runoff in their area. Information from the Environment Agency's national datasets might have been used in local studies and plans, and therefore LLFAs should be careful not to duplicate information. The following box explains locally agreed surface water information. This is not a requirement under the Regulations, but does inform the PFRA process because this information should play an important part in identifying Flood Risk Areas. Locally agreed surface water information Environment Agency guidance on using surface water flood risk information recommends that LLFAs should: review, discuss, agree and record, with us, water companies, IDBs and other interested parties, what surface water flood data best represents local conditions. This is known as locally agreed surface water information. LLFAs should determine what locally agreed surface water information means early within the PFRA process (we recommend within two months from the release date of this guidance). The benefit of this will be to assist LLFAs in identifying Flood Risk Areas. Locally agreed surface water information could be made up from both: local information on future flooding from surface runoff for part of the LLFA (such as one District Council, or one town, or an IDB district) one of the national datasets provided by the Environment Agency (for the remainder of the LLFA). If this is the case, the summary map(s), table and description should state where each is the locally agreed surface water information and present that information. LLFAs should record available information on local drainage capacity in their preliminary assessment report. This information will inform any future revision of the FMfSW and/or flood hazard mapping under the Regulations. The Environment Agency may request a copy of 'locally agreed surface water information' where this is local information (rather than part of a national dataset) to inform our strategic overview/oversight roles in England and Wales Groundwater National information about future floods There are four national datasets providing information on groundwater flooding. Each has limitations, which may include: cost, resolution, coverage (for example, England only), classifications (it may or may not be linked to an estimated flood probability) and hydrogeological coverage (for example, only chalk; or only consolidated aquifers). As identified earlier, the mechanisms of overland flow and ponding in topographic depressions have an obvious relationship with surface water flooding. Above ground locations identified at risk of surface water flooding, that lie within an area susceptible to groundwater flooding, may also be susceptible to groundwater flooding. The consequences of future flooding from groundwater (in the areas susceptible to groundwater flooding) are therefore not additional to those counted and recorded for the future surface water flooding maps. 17