Foresight Flood and Coastal Defence Project:

Proposed Approach

Executive Summary:

1.1

This paper sets out one possible approach for implementing the Foresight project in Flood and Coastal Defences. It is intended as a 'straw-man' which will form the starting point for open discussion at the scoping seminar on 27th June. issues for discussion at that event are marked in italics. This document should be read in conjunction with 'Foresight: Flood and Coastal Defences Project Proposal' which explains the background and rationale for the project, and places the work in the context of existing research and reviews.

1.2

The project aims to produce a long-term (2030-2100) and holistic vision for future risk of fluvial and coastal flooding in the UK, and to consider the options for responding to that risk. The findings will then be used to inform policy and its delivery. The added value of Foresight will be to look far into the future, and to take a broad and holistic approach to the analysis. It is proposed to divide the work into two parts:

• Firstly, create plausible scenarios for future risk of fluvial and coastal flooding. To do that, we will need to identify and take account of the principle drivers: these will relate to climate change, evolving land use, and socio-economic changes. The resulting flood risk scenarios will then be assessed to determine their cost, in terms of economic, social and environmental factors. This will involve identifying the assets which will be at risk in the flooding scenarios (houses, nature reserves, power stations etc), and using metrics to assess the impact of the flooding.
• The second part of the project will identify a range of mitigation techniques that could be used to manage the fluvial and coastal flooding risk. It will start by looking at those which are currently in use, and consider the extent to which they can cope with future flood risk - as detailed in the flooding scenarios. The project will then evaluate new tools and techniques, to identify which could usefully be added to the flood manager's toolbox. A key consideration will be whether incremental changes to existing mitigation techniques will be sufficient, or whether a step change in approach will be needed.

1.3

Whilst the flooding scenarios will be constructed on a geographical/regional basis, it is expected that they will also expose a number of broad themes - such as the impact on the Government's sustainability agenda, threats to major urban settlements such as London, insurance, and implications for agricultural land use. These themes will be considered further when considering possible mitigation techniques.

1.4

Following the June 27 seminar, a roadmap for the project will be produced and posted on the Foresight website: (www.foresight.gov.uk) The main body of work for the project is expected to begin around September and be completed in the summer of 2003.

Derek Flynn, 24/06/2002

Foresight Flood and Coastal Defence Project: Proposed Approach

1. Introduction

1.1

This paper sets out one possible approach for implementing the Foresight project in Flood and Coastal Defences. It divides the project into component parts and suggests options for how these might be taken forward. It is not intended to be definitive, rather a 'straw-man' which will form the starting point for open discussion at the scoping seminar on 27th June. issues requiring clarification at the seminar are marked in italics.

1.2

This document should be read in conjunction with 'Foresight: Flood and Coastal Defences Project Proposal' which explains the background and rationale for the project, and places the work in the context of the considerable amount of existing and ongoing research in the field of flood and coastal defences.

1.3

The project aims to produce a long-term (30-100 years) and holistic vision for future flood risk in the UK, and to consider the options for responding to that risk (Note: 'flood risk' is taken to refer to both fluvial and coastal flooding throughout this paper). The findings will then be used to inform policy and its delivery. The added value of Foresight will be to look far into the future, and to take a broad and holistic approach to the analysis. To this end, it is proposed to divide the work into two parts:

• produce scenarios for the risk and extent of fluvial and coastal flooding over the next 30-100 years; and evaluate the significance of the flooding (taking into account economic, social and environmental factors;
• assess the techniques or responses which are available to meet the flooding risk, and the key issues associated with their use.

Identifying the issues which will affect future flooding:

2. Generating flooding scenarios, and assessing their impact:

2.1

There are a large number of issues which could potentially affect the future risk and severity of flooding. It will therefore be necessary to perform an initial broad-brush sift to identify which are the most important, and to focus attention on those - it will be important that we do not get bogged down in modeling fine detail when broader uncertainties may dominate. Subject to that caveat, it is expected that the most important factors will fall into the following categories:

• climate change: the existence of climate change is now well accepted, *1 however its magnitude remains uncertain - since it is influenced by future emissions levels (which are dependant on socio-economic factors), and because of deficiencies in existing climate models. A possible starting point for this project are the predictions in UKCIP02 *2- these correspond to four emission scenarios, which in turn are based on four socio-economic scenarios. However, these predictions have certain limitations. Firstly they do not fully extend to 2100 (they are based on 30 year averages, the last of which is centred on the 2080's). Secondly, the predictions from climate models around the world yield very different results. Finally, predictions relating to storm surges and wave heights are particularly uncertain. what climate change predictions should be used, and what needs to be done to address the existing limitations?
• land use and socio-economic trends: land use affects both the propensity of land to flood, and the damage which is subsequently caused. Rural land use, for example, affects the ability of the land to act as a sponge and thereby impacts on flooding risk. In contrast, the present trend towards urbanization will exacerbate rapid runoff - and when alongside rivers can prevent floodplains operating as natural storage areas. The UKCIP02 socio-economic scenarios may be used as a starting point in identifying future changes in land use and the future distribution of population and assets. however further development of these scenarios will be needed to produce the required information for this project. How best to choose and constrain the socio-economic scenarios? How important are socio-economic effects compared with climate change?
• wild-card events: these are low-probability events which would have a large impact. Examples might include, melting of the icecap on the Antarctic land mass (sea level rise), or a shift in the Gulf Stream (major climatic shift). what are the main wild-card events which should be considered?

*1 Climate Change 2001 - The Scientific Basis. Contribution of Working Group 1 to the Third Assessment Report of the Intergovernmental Panel on Climate Change. ISBN 0-521-01495-6

*2 Climate Change Scenarios for the United Kingdom. April 2002 www.ukcip.org.uk

Constructing Risk-based Flooding Scenarios: 2030-2100.

2.2

The aim is to create plausible and credible scenarios for future fluvial and coastal flood risk in different parts of the country, so that we can then assess the possible flood mitigation techniques against those requirements. Should we concentrate on producing large-area statistics, or smaller-area exemplars, or a combination? Also, a key factor which will influence the credibility of those scenarios, will be how we handle the various forms of uncertainty which impact on those scenarios - these will include uncertainties in the drivers (climate change, sea level rise, changes in land use etc) and uncertainties in how these factors translate to flooding risk (e.g. due to deficiencies in hydrological and other modelling techniques).

2.3

The flooding scenarios will depend on a great number of factors and could be built up is as follows (see Figure 1):

• Perform a broad-brush assessment to determine which factors should be taken into account in producing the scenarios, and which can be disregarded.
• Evaluate a 'do-nothing' scenario for flood risk: for selected climate change scenarios (e.g. based on the UKCIP02 scenarios), assess how the changing climate would affect the frequency and extent of flooding (say 30,60 and 100 years hence), were it to occur in present day Britain - assuming the current distribution of the population, and the current level of flood defence measures. the generation of this baseline remains a critical issue that needs to be clarified. What existing models could be used to produce this 'do-nothing' scenario, and how much new work would be involved? What measures of flood risk need to be produced? What needs to be taken into account to ensure robustness: for example, the specific hydrology of the location; the non-linearity between climate change (e.g. increased storminess, and changes in the amount of prolonged rain) and flooding; also combinations of factors (e.g. storm surges following periods of prolonged rain).
• Adjust the 'do-nothing' predictions for flood risk to take into account future land-use and socio-economic changes in the UK in 2030-2100. What work needs to be done to develop the land- use scenarios, and how should that be incorporated into the baseline model?
• Evaluate the risk of low-probability/high impact (wild-card) events - this would need to be done on a case-by-case basis

Evaluating the Impact of the Flooding:

2.4

Not all flooding is unwelcome. Whilst a flooded town might be disastrous, a flood might be desirable (or even necessary) to maintain a particular wildlife habitat. The first step in evaluating the impact of the flooding will therefore be to use the socio-economic and land use scenarios to determine what assets (properties, agricultural land, nature reserves) will be at risk in the flooding scenarios.

2.5

Metrics will then be used to assess the impact on the assets (and their inhabitants) which are at risk. It is proposed to do that by developing three measures - covering economic, social and environmental factors. These measures might, for example, enumerate houses at risk, or the amount of prime agricultural land under threat, or be much more complex. It is suggested that the three measures are kept separate to maintain transparency. how should these measures be constructed, and applied on a regional or national basis, so that the results are credible?

2.6

Certain critical assets may require special treatment. Nuclear power stations, for example, are immovable and, being situated on the coast, will be at increased risk from sea level rise, storm surges, and increased geomorphological activity. It is suggested that a small focused study be performed to assess the risk and impact on such critical assets. what other pieces of critical national infrastructure merit special attention? Further, it is expected that the impact of wild-card events will need to be considered on a case-by-case basis.

2.7

Whilst the flooding scenarios will be constructed on a geographical/regional basis, it is expected that the impact analysis will expose a number of broad themes which will cut across two or three of the measures - these will be useful in focusing our analysis of responses in the second part of the project. Examples might include: the implications of increased flood risk on the Government's sustainability agenda, *3 the Water Framework Directive, *4 insurance (properties becoming uninsurable will have broad implications for urban communities); threats to major urban settlements such as London; threats to critical coastal infrastructure; threats to our international obligations for preserving habitats/biodiversity *5 (responses may have implications for recreation land use, and rural economies); implications for agricultural land-use.

*3 Achieving a better quality of life. Review of progress towards sustainable development. Government Annual Report 2001 http://www.sustainable-development.gov.uk/
*4 the Water Framework Directive 2000/60/EC
*5 e.g. the EC Habitats and Species Directive 92/43/EEC, Conservation of Birds Directive 79/409/EEC, and the 1971 Ramsar Convention

3. Responding to the Challenge of Flooding

3.1

Having produced scenarios for the future extent, risk and impact of flooding, we now need to identify and investigate how the UK might respond to those challenges. a key issue will be whether incremental changes to existing responses will be sufficient, or whether a step change in approach will be required in certain cases.

Identifying possible responses:

3.2

Table 1 provides an indicative list of some of the responses identified so far - these will need to be fleshed out, and others identified through further consultation, in particular, the contribution of new science and engineering. The table groups the responses into three classes - techniques and planning tools which are already in use or being implemented; techniques which are not being implemented because of inhibiting factors (these may be cross-government or cross institutional issues, or the need for further scientific research and development); and further types of response - involving the application of new science and engineering, or new ideas from abroad.

Responding to the future flooding scenarios - general considerations:

3.3

Responses to flooding are essentially about planning for, controlling or modifying the flow of water as it moves through or over the land/coast. The aim of this part of the project is to assess and compare the different responses to flooding. This task is far more difficult that first appears:

• There is a considerable number of potential responses - all very different in nature, benefit and applicability, and some untested.
• Different responses need to be assessed in different ways. For example, the calculations used to assess the benefits of new building practices (in making existing houses resistant to flood damage and therefore insurable) will differ from those used to assess managed realignment (which will involve issues of land use). assessment techniques will need to be devised for different types of response.
• The applicability of a particular response will generally be location specific: for example, managed realignment might be cost effective for one stretch of coastline, but inappropriate ten miles away due to coastal geomorphology or differing land use - how then to assess the general applicability of a particular approach, as it is impractical to consider every possible location across the UK?
• Increasingly, different types of flood defence are combined in order to manage flood risk in an integrated and (increasingly) holistic way. This is already happening with Shoreline Management Plans, and Catchment Management Plans are following. how then to assess the usefulness of a particular type of response, when it will mainly be used in combination with a number of others?
• A comparison between different types of response is routinely made when designing flood defence schemes for specific locations. For example, the cost/benefit of 'managed realignment' versus 'reinforcing existing defences' are compared for shoreline management plans. *6 We need to ensure that any comparisons which we perform will add value over this existing work.

*6 DEFRA, June 2001. Shoreline Management Plans - A Guide for Coastal Defence authorities. www.defra.gov.uk

3.4

The key conclusion is that it is difficult to assess the usefulness of a particular type of response in isolation, without placing it in the context of other sorts, and without reference to specific locations in which it might be used. Instead, it is appropriate to consider different types of response as tools in the flood manager's toolbox - any of which may be combined to tackle the flooding risk in a particular catchment or shoreline. The question then becomes, is how comprehensive is our existing tool set, and what added value would particular new tools offer? what can we realistically do to inform the existing strategy for flood mitigation, and to inform the development of new tools?

Responding to the Future Flooding Scenarios - Evaluating Responses

3.5

We are bound to start by considering the extent to which flood defence measures which are existing or being newly implemented (i.e. the first category of Table 1) can cope with the future level of flood risk, and to what extent they can address the challenges inherent in the broad themes identified above. The shortcomings identified in our toolbox will provide the rationale for seeking new tools/techniques, and will provide guidance on where to focus our effort.

3.6

It is expected that consideration of the potential new tools (the second and third categories of Table 1) will need to start by taking a broad-brush look - in order to determine which are likely to be of most interest. what criteria should be used to make that choice? The subsequent method of analysis for each chosen tool will then need to be determined on a case-by-case basis. The analysis is likely to have the following broad stages:

• identifying existing work which has been used to assess the given response;
• devising an assessment methodology, taking into account economic, social and environmental factors - the methodology might include socio-economic studies, using existing research tools to investigate a given response, and case examples in particular locations etc.
• use the methodology to assess the response's usefulness, its complementarity with existing techniques, and its potential in contributing to the broader themes such as sustainability etc. This is likely to require consideration of case studies in critical locations;
• assess the response's general applicability across the UK (is the technique only relevant to one small location, or every catchment?);
• identifying and considering the factors which would inhibit its implementation/use.

Drawing the threads together and stimulating action.

3.7

All of the work of the project will be drawn together in a report, and used to stimulate and inform a wider debate with stakeholders, with a view to informing policy, and catalysing further action. As part of that process, a high-level group of stakeholders (drawn from the public and private sectors) is currently being constituted under the chairmanship of Elliot Morley - the Minister in DEFRA responsible for flooding. A key function of that group will be to act as a sounding board for the work of the project and its emerging conclusions. In that context, the membership will be drawn from organisations which would have an interest in taking forward the resulting recommendations.

4. What Happens Next?

4.1

The project team is currently being formed. Professor David King will head the project, supported by a team of civil servants. Several scientific experts will also work within the team.

4.2

The scoping of the project will continue through July 2002. Once this is complete, a plan for the project will be posted on the website (around August 2002).

4.3

The main work will start in September. Besides in-house studies, it is expected that a number of specialist seminars and events will be organised to inform the detailed parts of the project. In addition, web-based discussions on specific topics are likely to be held. Information about these, and all other aspects of the project will be posted on the Foresight website.

Return to defining the project page

Table 1: Flood Defence Measures

The following list is only meant to be indicative. Also, some of the techniques straddle more than one category.

Techniques and planning tools, which are already in general use or being implemented:

• Shoreline Management Plans (SMPs): 'Shoreline Management Plans - A Guide for Coastal Defence authorities'. DEFRA, June 2001
• Coastal Habitat Management Plans: 'An Interim Guide to Content and Structure' - English Nature, Environment Agency and the Centre for Coastal Marine Sciences
• Managed realignment
• Washlands: 'Sustainable flood defence: the case for washlands'. No 406 English Nature reports
• Improvements to hard defences
• Demountable defences
• Advanced engineering (e.g. Thames Barrier)
• Total catchment management plans (currently being piloted)
• integrated risk management - for example the RASP project, which seeks to build upon'National Appraisal of Assets at Risk of Flooding and Coastal Erosion in England and Wales', DEFRA 2001.

Techniques whose use is impeded because of inhibiting factors:

(these may be cross-government or cross institutional issues, or the need for further scientific research and development):

• Integration of land use (e.g. agricultural practices and crops) into total flood catchment management plans
• Use of building practices to make buildings resistant to flood damage
• Agri-environmental schemes - e.g. farmers 'farming water'
• New techniques in managed realignment
• Restoration of built-up flood plains
• Dual use of water supply reservoirs for flood storage

Further types of response - new science and engineering, or new ideas from abroad:

• Netherlands: large-scale purchase of land adjacent to rivers, and its integration into flood management schemes (to promote a shift from agriculture and building towards recreational facilities and habitat generation).
• Japan: use of compound (two stage) river channels to allow normal river flow for most of the year, with a broader flood channel used for recreational and temporary purposes, and available for occasional flooding.
• USA: availability of federally backed insurance funds to communities that agree to adopt and enforce flood plain management to reduce future flood damage.
• offshore wave and tidal energy generation - proposal from the Foresight Marine Panel. This would reduce the energy reaching the shore, thereby benefiting coastal defences. Including this additional benefit could secure the commercial viability of this alternative energy source.

Figure 1: suggested methodology for producing future fluvial and coastal flooding scenarios and evaluating their impact (separate studies of wild-card events and of critical coastal assets are not shown).