Water

Abstracts from the 39th Flood and Coastal Management Conference, July 2004

Please see the main Conference page for details of ordering Conference proceedings or individual papers. Please note that the views expressed in Conference papers are those of the speaker and do not necessarily represent Defra views or Government policy.

Some Web links in the abstracts below have been converted from normal text by Defra to provide more immediate information on particular topics via the linked pages. The wording in any abstract that has been converted to a Web link is part of the original text. It should not be assumed that the content of the linked pages is supported or approved by the paper's author/s unless this is suggested by the text of the abstract.

Session 1: Strategic Decision Making

01-1 Strategic Options For Flood Management On The River Clyde In Glasgow

By: K M H Barr, (W.A Fairhurst & Partners), J W Fleming, (Glasgow City Council) P Lardet (Halcrow Group Ltd), R B Binnie (Halcrow Group Ltd) and J N Cooper (JBA Consulting)

Key Words: Strategic, Regeneration, Glasgow

Abstract: The aim of the River Clyde Flood Management Strategy is to develop a sustainable solution to manage both tidal and fluvial flood risks in Glasgow and to eliminate an increasing obstacle to regeneration of the Clyde Waterfront. The study is based on a catchment-wide approach to develop a solution integrating the constraints and opportunities related to hydrology and hydraulics, geomorphology, environment, planning and regeneration, amenities, transportation, urban drainage, navigation, geotechnics and the conditions of existing structures (quay walls, docks).

The paper presents the work carried out in 2003-2004 for the option identification stage - at catchment scale and along a detailed 50km river corridor - and discusses how the potential engineering options - direct defence, tidal barrier, upstream storage - can integrate with the aspirations for regeneration and constraints and opportunities identified within the catchment.

01-2 Applying Reliability Risk Analysis To Flood Risk Management

By: John Hother, CEng, (Proneta Ltd)

Key Words: Reliability Risk Analysis

Abstract: There is a recognised need to develop practical guidance and tools which genuinely support a wide range of decision-makers and information needs, within a coherent framework for risk, uncertainty and performance.

Failure Modes, Effects and Criticality Analysis (FMECA) is a technique for reliability risk analysis that is widely used in aerospace, automotive and electronics industries. However, it has certain features that make it valuable in the field of flood risk management.

It is a systematic way of collecting and analysing all the different failure modes, their causes, effects and consequences. Consequences may be characterised in different terms: environmental impact, social impact, financial impact, and safety hazard to people. It produces results that provide a sound basis for establishing corrective actions and prioritizing them.

Moreover, its flexibility allows it to be adapted to provide further benefits -

  • quantitative results by combining economics with the engineering analysis;
  • consolidation of a large failure-mode data set into concise results, usable in the decision-making process.

Examples of the results from case studies in other industries, using the adapted Reversionary Mode Analysis (RMA) form of FMECA, demonstrate how it could add value in its new role of flood risk management.

01-3 Strategic Environmental Assessment: Opportunities And Constraints For Flood and Coastal Management Strategies

By: Tom Matthewson, BSc MSc MCIWEM and Katie Prebble, BSc MRes MCIWEM Black and Veatch Consulting Ltd

Key Words: SEA, Flood Management

Abstract: The incorporation into UK law of the EU Strategic Environmental Assessment Directive brings with it new responsibilities and opportunities for flood and coastal management strategies. As a process, SEA undoubtedly has the potential to deliver environmental benefits and help ensure regulatory approval of the preferred options. Drawing on the authors' experience of preparing SEAs for flood and coastal management strategies, this paper reviews the application of SEA in this field, and seeks to recommend areas for development and improvement.

01-4 Comparing Apples And Oranges - The Use Of Appraisal Summary Tables In Decision-Making

By: John Ash, BSc, CEng, MICE, FCIWEM (Risk & Policy Analysts Ltd) and Teresa Fenn BSc, MRes. (Risk & Policy Analysts Ltd)

Key Words: Appraisal Summary Table, Decision-Making, Managed Realignment

Abstract: Decision making in any field, including flood risk management, requires the comparison of different types of impacts associated with a range of options in order to select a preferred option. One way of managing the information on which a decision is based is through the use of Appraisal Summary Tables (ASTs).

ASTs are tabular summaries of the main economic, environmental and social impacts of a proposed option, whether relating to a policy/programme, strategy or scheme and can include economic valuations, quantitative data and qualitative descriptors. The aim of the AST is to ensure transparency, i.e. to provide a structure in which all of the reasons for choosing a preferred option are set out in a clear and intelligible manner. In this way, the decision making process transforms from a 'black box' to a more auditable process.

This paper discusses how ASTs have been developed from their beginnings in transport and illustrates how they can be used in a whole range of applications. An example to show how the approach has been refined for use in the flood defence field is given, the key issues that this has raised and the potential solutions proposed. The example is based on the approach to selecting the most cost-effective managed realignment sites in the Humber Estuary.

Session 2: Planning and Risk Assessment

02-1 Floodplain Management In Norway - Integration Of Flood Risk Information Into Land Use Planning

By: Hallvard Berg and Tharan Fergus, Norwegian Water Resources and Energy Directorate

Key words: Flood Risk Information, Land Use Planning

Abstract: Floodplain management in Norway has been substantially developed after a major flood in 1995. A White Paper representing a national flood action plan and presenting several measures, such as strengthened flood forecasting, a flood inundation map programme and guidelines on land use in flood prone areas was put forward in 1997. According to the Planning and Building Act the municipalities are responsible for taking natural hazards into account in land use planning, and could be liable if damage occurs. NVE is responsible for river safety at national level and for guidance and control of local plans. The guidelines on land use planning in flood prone areas define differentiated safety levels along two dimensions: type of flood and type of asset. Together with detailed maps of flood prone areas, this has proved to be an efficient tool in improving safety against floods.

02-2 Development And Flood Risk: Guidance To The Construction Industry On Putting Planning Policy Guidance Into Practice

By: Dr James Lancaster, MCIWEM, (Arup Water), Marianne Scott (CIRIA), Craig Elliot (CIRIA), Dr Clive Marshall, CEng FICE FCIWEM (Arup Water) and Dr Martin Preene, CEng FICE MCIWEM CGeol FGS (Arup Water)

Key Words: None

Abstract: This paper reviews the new CIRIA Report C624 "Development and flood risk - Guidance for the construction industry", which is to be published this summer. It summarises the report to raise awareness of the recommendations developed in this key project. To promote an improvement in the sustainability of new developments, planning guidance relating to development and flood risk has recently been prepared for England, Wales, Scotland and Northern Ireland. However, the planning policy documents do not provide technical guidance on how flood risk should be assessed or what measures may be employed to reduce flood risks associated with developments. This means that the practical application of the new planning guidance presents a major challenge to developers, planners and regulators when considering the acceptability of a proposed development. Guidance has therefore been prepared on assessing flood risk within the planning process. This guidance has been developed to be applicable throughout the United Kingdom, and to be useful for all parties involved in the planning process.

02-3 Strategic Flood Risk Assessments

By: Roy Lobley, (Environment Agency), Peter Raspin, (Lincolnshire County Council) Stuart Birkett, (Boston Borough Council)

Key Words: Planning Policy Guidance Note 25, Flood Risk, Sequential Test.

Abstract: Part of the Environment Agency's vision is aimed at reducing flood risk by influencing planning activities to prevent 100% of inappropriate development inside floodplains. The Agency works with local planning authorities to achieve this by ensuring that flood risks arising from land use and climate change are recognised, understood and fully taken into account in planning decisions.

The Government also aims to reduce the risks to people and the developed and natural environment from flooding by discouraging further built development within floodplains and promoting best practise for the control of surface water run off.

This paper shows how the Agency has been working closely with local planning authorities, particularly within the relatively low-lying part of eastern England, to develop the use of Strategic Flood Risk Assessments so that the actual level of flood risk within the indicative floodplain can be determined. Thus allowing objective judgements to be made on future land allocations, on a risk-based approach, through the application of the sequential test as described in Planning Policy Guidance Note 25.

Local planning authorities consider that such assessments also facilitate evaluation of actual flood risk in the context of the land allocation sustainability criteria contained in Planning Policy Guidance Note 3 (Housing).

02-4 Automation Of Flood Contingency Plans: Introduction In The Netherlands And International Applicability

By: Jaap-Jeroen Flikweert (Royal Haskoning), Martin Whiting (Royal Haskoning), Camiel Coremans (IKM Engineering), Kees De Gooijer (HKV Lijn in Water), Ludolph Wentholt (STOWA)

Key Words: Operational Flood Management, Risk Reduction, Automation

Abstract: In the Netherlands, water boards are responsible for the performance of flood defence works. They use contingency plans to handle the complex situation during flood threat situations. Depending on the expected water level, responsibilities change and actions have to be taken. Recent flood threat situations have raised awareness that the human factor constitutes a significant risk. Consequently, an automated tool called Geautomatiseerd Draaiboek Hoogwater (GDH / Automated Flood Contingency Plan) was developed.

This paper outlines the problem of information management during floods, the benefits and risks of automation, the development process of the tool, the resulting tool and the implementation process. Based on this analysis, the practices and tools in the Netherlands are considered against how they may be applied in other countries.

Important conclusions:

  • Automation of information management can cause a significant improvement of safety against flooding: by using computers for what they are good at (storing information, handling predefined procedures), humans can focus on what they are better at: dealing with unexpected developments and making decisions based on incomparable criteria.
  • Successful development of a computer system for emergency situations requires a maximum of user input throughout the development process.
  • Throughout Europe, there is a development toward the use of automated tools for operational flood management, not only for prediction and warning, but also for action monitoring, communication, presentation and post event evaluation.

Session 3: Strategic Approaches

03-1 The Reality Of Shoreline Management Plans

By: Helen Jay, (Halcrow Group Ltd), Adam Hosking, (Halcrow Group Ltd), Alison Atkinson (Halcrow Group Ltd ) And Kevin Burgess ( Halcrow Group Ltd)

Key Words: None

Abstract: Shoreline Management Plans (SMPs) are strategic documents that provide "a large-scale assessment of the risks associated with coastal processes and presents a policy framework to reduce these risks to people and the developed, historic and natural environment in a sustainable manner" (Defra, 2001). The Interim Procedural Guidance for Production of Shoreline Management Plans, produced in June 2003 (Defra, 2003), set out the activities to be undertaken in the development of an SMP to meet these objectives. This Interim Guidance has now been applied on the first three SMP reviews (Figure 1) and the lessons learnt from those applications are now feeding into the finalisation of the guidance. This paper discusses the outcomes to date from the pilot SMPs, and the possible implications for the final guidance, due to be available by late summer 2004.

03-2 Flood Risk Management In Estuaries (Frame) - A Practical Review Of European Experiences

By: Mark Van Koningsveld (WL|Delft Hydraulics) and Tom Matthewson (Black and Veatch Consulting Ltd)

Key Words: Flood risk management, Estuaries, Flood Control Areas

Abstract: To inform the delivery of the FRaME demonstration projects, reviews have been commissioned to collect relevant international experience of flood control area (FCA) implementation. One of these studies, undertaken by Black and Veatch and WL|Delft Hydraulics, focuses on the review and evaluation flood control areas. From an initial quick scan phase, sites in the Netherlands, United Kingdom, Belgium and France were selected for more detailed analysis. The success or otherwise of the planning, design, implementation and operation of a specific flood control area in each site has been reviewed, using the 'frame of reference' analysis method. The analysis was conducted through the establishment of Key Performance Indicators, against which each site was assessed. Lessons that have been learnt relating to each site and more generally, have been identified to support the preparation of an FCA best practice manual.

03-3 Putting Flood Risk Management Into Practice: The Chesterfield Experience

By: Will Mcbain, MCIWEM, MIENVSC, FRGS, (Arup Water) John Turner CENG, MICE, (Environment Agency) PHIL REEVE ( East Midlands Development Agency)

Key Words: Chesterfield, Flood, Management.

Abstract: Chesterfield is typical of many towns and cities that suffer from complex and inter-related flooding problems. In Chesterfield these problems are associated with sections of Main River, Critical Ordinary Watercourse, ordinary watercourses, surface water drainage and sewerage. Flood risk mapping, development control and flood warning measures are being used by the Environment Agency to manage the flood risk in Chesterfield wherever possible. However, properties in many areas remain at unacceptable risk of flooding. The strategy for the implementation of flood management improvements is being developed by a Steering Group comprising the Environment Agency (EA), East Midlands Development Agency (EMDA) and Chesterfield Borough Council (CBC). Initial investigations have focused on floodplain restoration, sustainable drainage and flood balancing opportunities offered by an EMDA scheme to restore a heavily contaminated industrial site upstream of the city. This paper outlines the strategic approach being adopted, which not only draws heavily on Flood and Coastal Defence Project Appraisal Guidance Note 2 (FCDPAG2) 'Strategic Planning and Appraisal' and Policy Planning Guidance Note 25 (PPG25) 'Development and Flood Risk', but also incorporates a wider perspective on partnering, environmental enhancement and urban regeneration.

03-4 Dynamics Versus Constraints In Strategic Flood Management

By: Karen Thomas, (Environment Agency), Paul Turney, (Halcrow Group Ltd)

Key Words: None

Abstract: As a result of sea level rise and consequential coastal squeeze, the structural integrity of many of the flood and coastal defences within estuary systems is progressively declining and internationally designated salt marsh habitat is continuing to erode. Consequently, the Environment Agency aims to promote more sustainable flood management schemes for the protection of people's lives and property, and recreate coastal habitat in order to meet salt marsh conservation and regeneration targets.

However, the selection of strategic flood management options to achieve this aim is not only constrained by the relationships between the economic, technical and environmental issues but also the natural estuarine processes and political issues.

The aim of this paper is to highlight the key constraints to the strategic option appraisal process that have been encountered in the Essex Estuary Flood Management Strategies (EEFMS), and the application of innovative estuary morphology analysis to develop a more sustainable estuary shape. The specific constraints covered in this paper include uneconomic seawalls; contaminated land and refuse filled seawalls; hydrodynamics; conservation regulations; public perception; stakeholder objectives; and political will.

03-5 The Humber Estuary: Paull Holme Strays Opened, Alkborough On The Way

John Pygott BSc PhD MCIWEM (Environment Agency), Helen Richardson BSc MSc (Environment Agency), Keith Slaney CEng MICE MCIWEM,(Environment Agency) Philip Winn CEng MICE (Environment Agency)
Richard Ashby-Crane BSc MSc (Halcrow Group Ltd)
David Keiller MA PhD CEng MICE (Black and Veatch Consulting Ltd)

Key Words: Flood Defence, Managed Realignment, Habitat Creation

Abstract: The Environment Agency recently opened the managed realignment scheme at Paull Holme Strays on the Humber, and with other partners is preparing a very much larger realignment project further upstream on the Humber at Alkborough. Valuable lessons are being learned from both projects that will assist as the wider Humber Estuary Shoreline Management Plan is delivered, but they will have much wider application as well. The paper describes the projects and the issues that have been addressed during their promotion and implementation.

Session 4: Water Framework Directive Debate

04-1 Delivering River Basin Plans Through The Planning System

By: Hugh R. Howes, B.Sc. (Econ), M.R.T.P.I., Strategic Planning Advisor, Environment Agency

Key Words: Water Framework Directive: Sustainable Water Management:

Abstract: The European Water Framework Directive requires the Environment Agency to prepare ten River Basin Management Plans for England and Wales. By bringing major environmental issues to the forefront of the planning process River Basin Management Plans will have a significant role in advancing the sustainable development agenda. They will promote the concept of sustainable water management through:

  • Safeguarding the sustainable use of water
  • Protecting and restoring the status of aquatic ecosystems
  • Improving the aquatic environment through the reduction of hazardous substances
  • Reduce pollution to groundwater
  • Contribute to mitigating the effects of floods and droughts.

The Environment Agency is currently examining the role that town and country planning and other local authority functions could play in river basin planning. Characterisation, the use of derogations and the content of the programme of measures, all of which will ensure that 'water bodies' achieve 'good status' by 2015, will interact with the planning system.

The main points that have emerged so far are:

  • Policies relating to sustainable water management, together with an indication of how they are to be implemented, must be included in Regional Spatial Strategies (RSS) and Local Development Frameworks (LDF) to ensure the best prospect of achieving 'good status'.
  • Planning based implementation mechanisms will play a significant role in achieving sustainable water management as regards proposals for new development and consequent provision of infrastructure.
  • Achieving good status in areas where existing development predominates will be a question of retro fitting and therefore outside the planning process and planning related funding sources.
  • 'Characterisation' suggests that achieving good status will be more demanding than at first supposed.
  • Funding and implementation mechanisms will increasingly preoccupy both local planning authorities and the Environment Agency.
  • Much remains to be done in terms of costing and budgeting for the works needed to achieve good status. All actions in River Basin Management Plans must be fully costed with funding in place.
04-2 Shannon River Basin District Project

By: Alan G Barr, BSc PhD CEng MCIWEM MICE MIEI (Partner, Kirk McClure Morton) Grace Glasgow, MEng CEng EurIng MICE MIEI MCIWEM (Senior Associate, Kirk McClure Morton)

Key Words: Water Framework Directive, Article V Characterisation Report, Shannon River Basin District

Abstract: December 22, 2000, will remain a milestone in the history of water policies in Europe: on that date, the EU Water Framework Directive (WFD) was published in the Official Journal of the European Communities and thereby entered into force. The WFD establishes a framework for the protection of all waters including rivers and lakes, transitional waters (estuaries), coastal waters and groundwater with the overall objective of achieving good water status for all waters by 2015.

In Ireland, the main vehicle for delivering the objectives of the WFD is through the establishment of major River Basin District Projects, funded by the Irish National Development Plan, and outsourced to experienced Consultants. This paper outlines Ireland's approach to the implementation of the WFD at River Basin District level through the Shannon River Basin District Project. The Shannon is Ireland's largest river basin and is a nominated pilot River Basin District in which the EU Common Implementation Strategy is being tested.

The WFD requires the preparation of an Article V Characterisation Report for every EU River Basin District by December 2004. This paper focuses on the key issues relating to the Shannon Characterisation Report including Ireland's approach to the delineation of water bodies, risk assessment and relevant pollutants.

04-3 The Water Framework Directive And Flood Management - A Missed Opportunity?

By: Joe Morris, Tim Hess, Andrew Gill, Peter Howsam, Sue White, Institute of Water and Environment, Cranfield University

Key words: Water Framework Directive, Flood And Coastal Management, Water Quality

Abstract: The Water Framework Directive (WFD) is widely regarded as the most important piece of European legislation with respect to water and the environment, setting ambitious targets to be met in a very ambitious time-scale. The Directive adopts a River Basin (ie catchment) Management based approach which will require effective integration of land and water management.

Article 1 states that the purpose of the Directive is to establish a framework:

  • to prevent further deterioration and protect and enhance the status of aquatic and related ecosystems; "prevent" implies a strong / strict obligation.
  • to promote sustainable water use; "promote" implies a weak obligation.
  • to aim to progressively reduce and for priority substances eliminate, pollution from hazardous substances; "aim to" implies a moderate obligation
  • to ensure reduction/prevention of groundwater pollution; "ensure" implies a strong obligation
  • to contribute to the mitigation of the effects of floods and droughts; "contribute to" implies a weak obligation

The Directive on the one hand sets expectations for an integrated approach but on the other focuses predominantly on water quality. Although there appears to be relatively weak reference to flood management, there are important actual or potential links between flood management, sustainable water use, ecology and biodiversity. Flood management functions as they affect flood generation, conveyance and storage have major implications for the physico-chemical, biological and hydro-morphological dimensions of water quality that are specified in the WFD. In some areas, hydraulic systems designed primarily to serve flood management and drainage purposes may justify special treatment as 'artificial' or 'heavily modified water bodies', with special dispensation to accept relatively low ecological status.

The WFD has important implications for the selection of flood and coastal management (FCM) options as these interact with ecological water quality. For example: measures to control run-off and flood generation from agricultural and urban land can help to mitigate diffuse pollution risks in receiving waters; river maintenance operations can critically affect ecological status; and, washland and wetland creation can help to exploit potential synergy between ecological and flood management objectives.

The Directive also requires increased levels of stakeholder and public involvement in the planning / decision making processes. Flooding has been a key water issue of public concern in the last few years because of the increased number of people directly impacted.

In this context, the paper confirms the links, potential synergy and conflicts between the objectives and methods of the Directive and FCM. It concludes that the WFD provides an opportunity to integrate FCM with other land and water management functions. This does, however, require that the interrelations are understood by those involved. It also requires that immediate action is taken to ensure that FCM is properly recognised as a water related service in the characterisation of River Basins to be completed by the end of 2004.

04-4 Encouraging Active Involvement - How Exciting Can The Water Framework Directive Get!

By: Peter Fox, PhD MIEMA, (Environment Agency)

Key words: Water Framework Directive, Participation, Ribble

Abstract: The implementation of the Water Framework Directive offers new challenges. Whilst building on and extending the considerable efforts to protect and improve the water environment, the scope and objectives of the Directive represents a "step change" for water managers.

Involving people in all stages of the planning and implementation of the Directive is the subject of considerable debate. Whilst involvement is not argued, the extent and methods of engagement do not achieve such consensus.

This paper reviews some of the results of work on public participation undertaken on the Ribble Pilot River Basin, aiming to support the development of European and British best practice.

04-5 The EU Water Framework Directive: A Wake-Up Call

By: Jan Brooke, Environmental Consultant

Key Words: EU Water Framework Directive; Heavily Modified Water Bodies; River Basin Management Plans

Abstract: Widely described as the most far-reaching water legislation ever to emerge from the EU, the Water Framework Directive (WFD) aims to provide a new, integrated approach to water protection, improvement and use. Whilst many of the provisions are welcome - and in some cases much needed - the Directive is nonetheless likely to have significant ramifications for all those involved in the use and management of water bodies and associated habitats.

Taking the Directive at face value, it appears to offer both significant opportunities and some real challenges to flood and coastal management. This paper, which is intended to be thought-provoking, discusses the possible practical consequences of requirements such as:

  • Achieving good ecological status
  • Ensuring no deterioration in water status
  • Allowing new developments which affect water status only if certain criteria are met

In the author's experience, until comparatively recently, the WFD had suffered from a low political profile and low awareness amongst stakeholders - none more so than in flood and coastal defence. However, whilst the WFD implementation process is already well-advanced, there are still opportunities to influence the process.

Ultimately, the implications of the Directive for flood and coastal management will depend on ensuring that decisions taken during the various phases of WFD implementation reflect the needs of the sector, and that such decisions are balanced, proportionate and scientifically robust. In order to facilitate this process, those involved at an operational level throughout the wider flood defence industry need to get informed, get involved and, in particular, ensure that the potential practical implications of WFD implementation for flood management are highlighted, acknowledged and properly dealt with.

Session 5a: Environment

05a-1 Rye Harbour Farm - Maximising The Benefits For Habitat Creation

By: Anita Ferguson, (Environment Agency) Philippa Harrison, (Environment Agency)

Key Words: Strategic Land Acquisition, Vegetated Shingle, Compensatory Habitat

Abstract: Rye Harbour Farm was purchased by the Environment Agency (EA) in March 2003 to enable the development of Pett Sea Defence scheme. This paper reviews the background to the sea defence scheme, the need to provide compensatory habitat and additional benefits to be gained from the land purchase. These include the securing of land for the footprint of a secondary embankment and the economic and environmental gains from sourcing construction material from the site. It also explores the future uses for Rye Harbour Farm once it has been utilised by the scheme. Various options are discussed which fulfil EA objectives, for example its use as a Strategic Land Acquisition for Habitats Regulations purposes, contribution to Biodiversity Action Plan (BAP) targets and wider EA Biodiversity, Recreation and Flood Risk Management objectives.

05a-2 Flood Defence Standards And Designated Sites

By: John Ash(Risk & Policy Analysts Ltd), Teresa Fenn. (Risk & Policy Analysts Ltd), Tim Collins (English Nature) and Zoe Masters, (English Nature)

Key Words: Flood Risk, Standards, Designated Sites.

Abstract: The management of flood risk on the coast and in estuaries frequently impacts on conservation sites, many with international and national designations. Recent practice has often been to provide a high standard of protection in an effort to preserve such sites. The present guidance in FCDPAG3 suggests an indicative standard of between 50 and 200 years for international sites.

However, many coastal and estuarine sites have developed with a history of regular or intermittent flooding such that a high standard of protection may not be appropriate. English Nature (EN) recognises the need to advise on appropriate standards of defence based on the conservation requirements for a particular site, but there is little information relating to 'what may be appropriate'.

A methodology has been developed for use by EN staff to inform decisions on appropriate standards of protection. It uses information relating to designations and citations, flood history and management of the site, key features, habitats and species to assess the impacts of do-nothing. If doing nothing is considered inappropriate for the site, the impacts of a flood on the key features, habitats and species are assessed. From this, an estimate of the appropriate standard of defence is obtained. This paper describes the methodology and gives an example of how it can be used to determine an 'appropriate standard of defence'.

05a-3 Habitat Compensation And Flood Management: Criteria And Issues To Be Addressed In The Design And Delivery Of Compensation Packages

By: Dr Chris. McMullon (English Nature) and Tim Collins, (English Nature)

Key Words: Flood Management, Compensation, Conservation

Abstract: Where flood management operations are deemed to adversely affect the integrity of European sites, but are considered necessary in the overriding public interest, the Secretary of State must, under the Habitats Regulations 1994, secure compensation measures before granting the relevant permissions. This has led on many parts of the coast to a search by operating authorities for habitat compensation opportunities. Issues relating to the quality, quantity and location of potential compensatory habitat have been raised. There is therefore a need for clear guidance on the design, delivery and approval of such compensatory measures required for flood management operations. This paper was developed by English Nature as guidance to operating authorities in response to this requirement. It sets out a series of criteria for use in the evaluation of the suitability and adequacy of compensatory measures. It provides guidance on the most appropriate location, size and quality of any compensatory habitat as well as issues of timing, site security and sustainability. Advice is also provided on the responsibilities of the key organisations involved in the habitat compensation process.

05a-4 Easton Broad: Achieving Sustainable Flood Management for Nature Conservation on the Suffolk Coast

By: Robert Harvey MA (Natural Sciences) Richard Crowder BSc (Engineering), PhD, CEng, MCIWEM, MICE Alan Frampton BSc (Ocean Science) Corinna Morgan BSc (Geography)
Daniel van der Leer BEng, MSc (Computational Modelling), PhD (Halcrow Group Ltd)
Stuart Barbrook BEng (Civil Engineering) Merle Leeds BSc (Geography)
Peter Doktor BSc (Environmental Sciences), MSc, AIEMA (Environment Agency)

Key Words: None

Abstract: Easton Broad River valley contains England's second largest freshwater reedbed, supporting breeding bitterns and marsh harriers, together with a saline lagoon. Both the reedbed and the lagoon are protected from the sea by a shingle ridge, through which the river drains and which is itself an important conservation feature, vulnerable to both breaching and overtopping. The site is a Special Protection Area for Birds, a candidate Special Area of Conservation, a Ramsar Site and a National Nature Reserve.

Easton Broad Flood Management Project is unusual because there are few built assets, which can be valued using traditional economic techniques, at risk. Instead, the project focuses on finding a sustainable approach to conserving the freshwater and brackish nature conservation features of the river valley. Holding the existing defence line on a rapidly eroding coast is considered unsustainable. The study considered the options of continued profiling of the beach or alternatively allowing the beach to adopt a natural profile subject to increased over-topping and landward migration. The implications of these approaches were studied using hydrodynamic and water quality modelling to predict the effects of both marine and fluvial flooding, including the effects of saline intrusion on freshwater habitat. To protect the freshwater interests in the majority of the river valley, a realigned defence, comprising an earth bank across the existing reedbed, was proposed.

Session 5b: Flood Management in Practice

05b-1 Working With Natural Processes In Urban Environments

By: Helen Dangerfield (Babtie Group) and Richard Copas (Environment Agency)

Key Words: Morphological Processes, Restoration, Management

Abstract: The benefits of enhancing rivers in urban environments are beginning to be recognised both in terms of environmental gain and flood risk management. The extent to which natural riverine and floodplain processes have been incorporated into the design of river enhancement or restoration schemes has often been limited by a lack of understanding about how river systems will respond if hard constraints are removed.

Natural processes determine the extent of sediment sourcing, transport and storage both at a reach and throughout the wider river network. The relationship between sediment dynamics and hydraulic geometry is important in assessing how change in any one parameter will impact on the functioning of the channel both in terms of flood management and environmental value.

This paper draws on examples of three projects where geomorphological techniques and principles have been used to support the planning and implementation of restoration or enhancement of natural processes. The recognition of local and catchment scale constraints on morphological processes can contribute to catchment scale planning in urban environments.

05b-2 Flood Problems In The City Of Gdansk

By: Ewa Jasinska and Wojciech Majewski Institute of Hydro-Engineering, Polish Academy of Sciences

Key Words: Gdansk, Flood, Flood Management

Abstract: This paper gives a general overview of the flood problems and especially in the city of Gdansk with regard to methods of the flood protection used in the past and at present. Gdansk, the Polish medieval old city, is situated on the Baltic coast in the lowland area at the mouth of the Vistula River. The city of 460 thousand inhabitants is a very important economic, cultural, scientific and industrial centre. It is one of the most flood-endangered urban agglomerations in Poland.

Detailed analysis indicates that the flood threat in the Gdansk region may come from three directions. From the old branch of the Vistula (Dead Vistula), which has a direct connection with the Gulf of Gdansk, from the main Vistula River in case of high discharges, and especially during ice cover in the mouth region, and from the moraine hills in case of high precipitation. These hills are now intensively urbanized, and in July 2001, the severe flash flood, resulting from extremely high rain, invaded Gdansk causing considerable losses.

The mathematical model was developed including a complicated system of rivers and channels in Gdansk, and calculations were carried out for various schemes. It was found necessary to construct almost twenty small reservoirs on the streams flowing from the moraine hills, to decrease a rapid runoff from this area. In addition, two flood polders are also planned in case of an extreme discharge in main rivers and a simultaneous increase of water level in the Gulf of Gdansk.

05b-3 Derivation Of Design Flood Estimates For The River Uck Near Uckfield - Problems And Solutions

By: David Macdonald, MSc MCIWEM, (Black & Veatch Consulting Ltd)

Key Words: Uck Floods Data

Abstract: This paper describes the history of flooding in Uckfield Town and the derivation of flood magnitude frequency estimates for the River Uck catchment to help evaluate potential flood alleviation measures. The key issues surrounding the use of the streamflow data available for the Uck at Isfield Weir, and the historic flood data for Uckfield Town, are described together with the problems experienced when applying the standard methods recommended in the Flood Estimation Handbook. Details are given about the judgements made when selecting the most appropriate design flood estimates, the lessons learnt during the studies, and the improvements that might be affected in similar future studies.

05b-4 Hillfarrance Flood Defence Scheme

By: Chris Bown BSc CEng MICE MCIWEM (Black & Veatch Consulting Ltd) David Wright BSc CEng MICE MCIWEM (Black & Veatch Consulting Ltd)

Key Words: None

Abstract: The village of Hillfarrance had a long history of flooding and the frequency of events was very stressful for many residents. A flood diversion channel was constructed in summer 2003 to by-pass the low capacity channels through the village. The extent was limited to a minimum required to provide a flow route away from the village properties, making full use of the upstream and downstream floodplains.

The paper describes the development of the scheme and discusses issues relating to the promotion of schemes for small rural communities, the need to concentrate on the relief of property damage whilst accepting less damaging flooding elsewhere and the risk of other bodies and individuals not accepting cost effective compromises.

Session 6a: Waves and Water Levels

06a-1 The CoastView Project: Video Technology For The Coastal Manager

By: Julie Richards and Jane Rawson, (Environment Agency) Mark Davidson, (University of Plymouth)

Key Words: Coastal State Indicators, Video, Coastal Manager

Abstract: The CoastView Project is an EC project, funded through the Fifth Framework Programme, which combines scientific research with the views of end-users, specifically coastal managers. This project is aligned with the Processes Theme of the EA/Defra R&D Programme.

The objective of the project is to simplify the task of the manager, by the development of Coastal State Indicators (CSIs). These define important coastal parameters that are identifiable by the use of video images. The CSIs are directly related to management issues, by providing information about the current state and evolutionary trends of the coastal environment, and will have relevance to flood defence and coastal protection, as well as ecosystem protection, navigation and recreation. Within the UK the project has focussed on Teignmouth, Devon; a site which has flood defence and coast protection issues, as well as tourism, navigation and shipping, and industry issues. European project partners, both end-users and scientific researchers are examining sites in Spain, Italy and the Netherlands.

The project uses relatively simple video technology, combined with the production of complex algorithms, to provide generic tools applicable to the management of almost any coastline. This paper will focus on the involvement of the Environment Agency as an end-user, providing input to the project by helping to make CSIs applicable to managers.

06a-2 Joint Probability Best Practice Guide: Practical Approaches For Assessing Combined Sources Of Risk For Flood And Coastal Risk Managers

By: Ian Meadowcroft (Environment Agency), Peter Hawkes (HR Wallingford) Suresh Surendran (Environment Agency)

Key Words: Joint Probability, Waves, Surge, River Flows, Design, Risk Assessment

Abstract: This paper introduces new Best Practice Guidance to support the wider introduction of joint probability methods for flood and coastal risk management. An interim version of the Guidance has already been produced. The final version is due to be published in December 2004, following evaluation and feedback from users. We view this as an important development that will support moves to a more integrated risk management approach.

Many flood and erosion risks depend on extreme combinations of events rather than individual extremes. Examples include coastal sites (waves and water levels), estuaries (tidal surge and freshwater flows) and urban areas (drainage of local rainfall combined with high tide or river levels). Joint probability studies aim to quantify the probability of extreme conditions and are used to provide information on the 'source' of risk for design or assessment studies.

A major programme of joint probability research has been carried out over the last few years. The initial emphasis was on methods for coastal defence design and assessment, resulting in development and dissemination of the JOIN-SEA software. More recently (Defra / Environment Agency R&D Project FD2308) the joint probability technique has been extended to a far wider range of applications including fluvial, tidal and coastal cases. Most of this work has focussed on different variable pairs but the later R&D has also included studies into the spatial correlation of extremes.

Using a common statistical approach, recent R&D has greatly extended the range of cases for which the joint probability method can be used. It has provided 'atlases' of some of the key correlation parameters, and has begun to examine the possible impacts of climate change on joint probability.

A new Best Practice Guidance Report is in preparation and a draft version will be produced before the Conference. This paper and the conference presentation seek to:

  • illustrate the applications of joint probability techniques
  • raise awareness and understanding
  • invite feedback from end users
06a-3 Developing An Improved Understanding Of Storm Surge Propagation In The Solent

By: Ivan Haigh, (ABPmer Ltd) Nick Cooper (ABPmer Ltd), John Harris (ABPmer Ltd) Richard Swift (ABPmer Ltd) Patrick Butcher,(Environment Agency) Ian Tripp (Environment Agency) and Tim Kermode (Environment Agency)

Key Words: Storm Surges, Water Levels, Numerical Model

Abstract: This paper presents an overview of the methods used in a study that investigated surge propagation in the Solent, central southern England, and describes some of the key findings that are important in improving understanding of the key physical processes and process-interactions involved. Previously, the level of understanding of surges in the Solent has been lower than the more researched areas of eastern and western Britain, but this has been improved upon in this study through a detailed literature review, analyses and cross-correlation of data from tidal gauges both throughout the English Channel and specifically within the Solent, and the development and application of a high-resolution numerical model of the Solent that is capable of replicating both external and internal components of surges. Results from the study are presently assisting the Environment Agency in flood risk planning in the Solent.

06a-4 Tides - A Level Of Confidence

By: David Worth, BEng CEng MICE MCIWEM, (Posford Haskoning) Tim Hunt, BEng CEng MICE (Environment Agency)

Key Words: Tide Levels; Trend; South West England

Abstract: Flood management around tidal waters needs sound information on event conditions that may arise. These set criteria for evaluating defences, assessing vulnerable areas and thereby guiding planning policy. Often in the past key factors, such as values for extreme tide levels, have been chosen for each locality in isolation. In practice this has proved to be an unreliable process. Despite tide levels being analysed multiple times over the years there can still be a wide disparity of answer between adjoining sites, and with levels between data points and in estuaries being overlooked. It is therefore appropriate to consider the wider "coastal catchment" scale so there will be greater consistency and confidence in parameter values adopted. This paper presents a practical example of wide scale extreme tide level derivation, considering the whole South West region from Avonmouth to Christchurch. The spatial analyses of Dixon and Tawn are improved. Tide levels and surge event tide curves are derived for all points along the coast, estuaries and tidal rivers. The coincidence and impact of fluvial discharge and wave action is described. Confidence limits are discussed. The experiences, which could usefully be applied elsewhere, are linked to flood risk management needs.

06a-5 Violent Wave Overtopping Discharges and the Safe Use Of Vertical Seawalls

By: Tim Pullen (HR Wallingford), William Allsop (HR Wallingford / University of Southampton), Jon Pearson (University of Edinburgh) & Tom Bruce (University of Edinburgh)

Key Words: Wave Overtopping, Field Measurements, Hazards.

Abstract: Current guidance on levels of safe overtopping discharge that can be tolerated by members of the public are often based on arbitrarily set values with little validation. Generally these values will indicate a mean discharge, but will not take into account how the overtopping is distributed across the seawall. This paper presents improved guidance for the design of seawalls, with particular emphasis on vertical and similar seawalls protecting urban areas, and the overtopping volumes and their velocities that can be tolerated.

Recent field measurements of violent overtopping during storms at Samphire Hoe, Kent, UK, have been conducted as part of the EU 5th framework and Defra / EA funded CLASH project. Laboratory measurements have also been made in smaller scales under CLASH and the UK EPSRC funded VOWS projects. Accurate measurements of individual wave-by-wave volumes have provided new data on how overtopping discharges are distributed under different conditions.

The results to be presented demonstrate a good agreement between methods for predicting wave overtopping and the recent field measurements. In particular the paper will describe how wind speeds affect the potential hazard of any given overtopping event.

Session 6b: Construction

06b-1 The Potential Use of Alternatives to Primary Aggregates in Coastal and River Engineering

By: Craig Elliott (CIRIA), Alan Brampton (HR Wallingford), Michael Wallis (HR Wallingford)

Key Words: Aggregates, Recycled, Waste, Re-Use.

Abstract: This paper reports on a recent CIRIA study, carried out in collaboration with HR Wallingford, to assess the potential for using recycled/re-used (secondary) aggregate and construction and demolition waste as aggregate for coastal and river engineering.

The objectives were to:

  • Reduce the impact of river and coastal construction on natural resources by promoting the use of alternative materials in place of primary aggregate and other materials.
  • Enable the construction industry to provide more sustainable and cost-effective solutions for river and coastal engineering.
  • Raise awareness of the potential use of secondary aggregate and recycled/reused materials as aggregate.
  • Reassure designers and constructors of the appropriateness for use of alternatives to aggregates.
  • Help overcome barriers to the use of alternatives to aggregates in a strategic and co-ordinated way.
  • Produce a best practice guide on the above.

The demand from coastal and river engineering works for primary aggregate is increasing and is expected to expand further. It is recognised that this demand will need to be met, in part, by alternatively sourced aggregate. This paper reviews the availability of secondary and waste materials for application to river and coastal engineering and how designers and engineers can apply them.

06b-2 Corton Coast Protection

By: Paul Patterson, (Waveney District Council) Mark Glennerster (Halcrow Group Ltd) and Gillian Millarv (Halcrow Group Ltd)

Key Words: Consultation; Public Relations; Problem Solving,

Abstract: Corton Village defences suffered a spate of failures over the period 1999 to 2001 that closed the frontage to public access and threatened the security of mainly tourism based cliff top development. The prevailing management policy for the frontage was one of long term Hold the Line. However, the economic justification for this position was marginal and there were increasing concerns over strategic sustainability. Public and political expectations for protection and restoration of amenity were high. Studies revealed that a revised management approach to deliver short term (20 year) protection, followed by acceptance of erosion, was justified under prevailing policy assessment criteria. The development of options to deliver this policy was constrained by relatively low benefit values. Construction was hampered by severe access limitations requiring high levels of innovation and flexibility by the contractor. Great effort was expended at every stage of project promotion and delivery to engage the public in ownership of scheme objectives. The process has introduced a policy of managed retreat to a community that has previously benefited from one of long term Hold.

06b-3 "Partners in the Wet" (A Contractors View)

By: Phillip Sanderson, Van Oord NV

Key Words: Partnering, ECC, Contractor

Abstract: In the wake of the Latham and Egan Reports, the Engineering and Construction Contract ("NEC") has been increasingly used in the UK as a means to facilitate a proactive partnering approach in the project team rather than the reactive adversarial approach commonly associated with and contemplated by the more traditional forms of contract.

NEC ECC "Option C - Target Contract with Activity Schedule" (with a capped Gain / Pain Share) is an option favoured by many Employers and Contractors. In this scenario, the Contractor is paid "Actual Cost" plus a "Fee" and if this is less than the Target Cost; a share of the savings. The so-called "Contractor's (Gain) Share" is however normally capped to limit any unwarranted benefit accruing to the Contractor from a generously established / comfortable Target Cost. In the event that the Actual Cost plus Fee exceeds the Target Cost, then the Contractor is only paid an agreed percentage of the additional cost - the unpaid element being the Contractor's (Pain) Share.

Van Oord ACZ is pleased to participate as a Preferred Contractor in two distinct Frameworks for the Environment Agency programme of flood defences in England and Wales. Namely, the National Contractors Framework, and the Combined Beach Management Framework. These Frameworks apply the principles of Partnering by using the tools available within the Engineering and Construction Contract ("NEC").

06b-4 Construction Of Dorney Bridge on the Maidenhead, Eton And Windsor Flood Relief Channel By Jacked Box Tunnelling

By: Douglas Allenby, BSc(Hons) PhD CEng FICE (Edmund Nuttall Ltd) John Ropkins, BSc CEng MICE (John Ropkins Ltd)

Key Words: Non-disruptive, Construction, Box culverts

Abstract: Jacked box tunnelling is a non-disruptive technique for constructing a new underpass, culvert or subway beneath existing railway and highway infrastructure. It was used to install a 23m wide, 9.5m high by 50m long reinforced concrete culvert beneath the London to Bristol main line railway near Taplow, Buckinghamshire, and is the largest jacked box tunnel in the United Kingdom.

Known as Dorney Bridge the culvert forms a vital link in the 11.8km long Maidenhead, Eton and Windsor Flood Relief Channel designed to prevent flooding of urban areas during peak flows of the River Thames.

The paper describes the technique which enabled the culvert to be tunnelled at shallow depth beneath the mainline railway without disrupting either the tracks or the train services. Design and construction aspects of the project are covered and the measures used to control ground disturbance, including the first use of ground freezing on a jacked box tunnel project, are explained.

Other applications of the technique are briefly reviewed and conclusions drawn on its use in the future.

06b-5 Standards For The Repair Of Buildings Following Flooding

By: Dr Stephen Garvin (BRE Scotland), Marianne Scott (CIRIA), Craig Elliott (CIRIA)

Key words: Standards, Repair, Buildings, Flooding

Abstract: Recent flooding events across the United Kingdom have highlighted the devastating impact that flooding can have on people's lives, property and business. However, there are currently no direct incentives for insurers or building owners to consider improving the standards of flood repair or resistance of properties. Although, it is unlikely that the effects of flooding can be eliminated completely, practical steps can be taken to reduce the cost of flood damage and to speed up recovery times.

A CIRIA research project, incorporating detailed research work carried out by BRE, aims to provide detailed specifications for the repair of walls, floors and sanitary fittings, services and fixtures. The guidance is intended for use by professionals within the construction industry i.e. those directly involved in repair work. The guidance uses a risk based approach to identify the standards of repair required and also provides good practice with regard to decontamination and drying of flooded buildings.

This work has been conducted as part of a collaborative programme of research linking in with the Environment Agency's flood management strategy.

Session 7: Sustainability

07-1 Integrated Flood Management

By: Avinash Tyagi, (World Meteorological Organization), Joachim Saalmüller, (World Meteorological Organization)

Keywords: Integrated Flood Management, Integrated Water Resources Management, Flood Policy.

Abstract: Increased population pressure and changing rainfall patterns have contributed to an increase in loss of human life and economic loss due to flooding. International and in many cases national policy initiatives have not adequately addressed flood issues and the underlying challenges.

The concept of Integrated Flood Management integrates land and water resources development in a river basin within the context of Integrated Water Resources Management (IWRM), with a view to maximizing the net benefits from flood plains and minimizing loss to life from flooding. For flood management to be carried out within the context of IWRM, river basins should be considered as integrated systems. Socio-economic activities, land-use patterns, hydro-morphological processes, etc., need to be recognized as constituent parts of these systems. A consistent approach needs to be applied to all forms of possible intervention. The entire hydrological cycle is considered rather than differentiating between floods and droughts when planning water resources development.

The aim of IFM is to put in place well-functioning integrated measures for flood management. For this, the linkages between various relevant sectors become very important. Thus, the most important key will be co-operation and co-ordination across institutional boundaries, noting that the mandates of many institutions will either cover only part of the river basin or extend well beyond the basin boundary. At the core of integration is effective communication across institutional and disciplinary boundaries, which can take place only if there is a perception of common interest. Emphasis should be on the adoption of flexible strategies and of an adequate mix of structural and non-structural measures, tailored to each flood-prone region (characterized by their various physical, social, cultural and economic aspects) - recognizing the importance of evaluating differing options and their relative advantages and disadvantages.

A participatory and transparent approach which includes a representative range of stakeholders in the decision making process is another key component of IFM. The degree of public participation can differ from region to region. However, it should not be assumed that such stakeholder involvement will necessarily result in a consensus. Therefore, a methodology for managing conflicts, possibly a formal system of conflict resolution, needs to be developed.

07-2 River Gowy And Thornton Brook Flood Alleviation Scheme

By: Celia McNally, CEng MICE (Environment Agency) & Nigel Wilder, CEng MICE (NCPMS)

Key Words: Sustainable development, Partnering

Abstract: This paper outlines the issues that made this a unique and, for the participants, a groundbreaking project that is resulting in a sustainable solution with significant environmental benefits: -

  • The creation of a major new wetland nature reserve enhancing what is already Cheshire's best example of a grazed wet grassland system, with a host of rare and interesting plants, insects and birds. This reserve will store potentially harmful floodwaters.
  • A new flood risk management system to protect the Shell and Castrol oil refineries (the second largest in the country) thus ensuring continued production at the plants and helping prevent the River Gowy from breaking its banks. Flooding over the refinery previously had the potential to take contaminated waters into the River Mersey estuary downstream thus causing pollution to a site of international importance for birds.
  • A strong public-private-charity partnership between The Environment Agency, Shell UK and Cheshire Wildlife Trust.
07-3 Sustainable Flood Management On The River Alt

By: Jonathan Wright, BSc MEng CEng MICE MCIWEM, (WS Atkins Consultants Ltd)

Key Words: Flood, Sustainable, Realignment

Abstract: The River Alt catchment covers 240 km2, including part of urban Liverpool and rural West Lancashire. The lower reaches incorporate some 4000ha of rich arable land, which has been created from tidal marshland over 700 years, and which is drained by a network of ditches and low-level satellite pumping stations. The whole area is defended from tidal and fluvial inundation by river and coastal embankments and a main pumping station capable of discharging the Alt at all stages of the tide.

A catchment flood management strategy and feasibility study have identified the key issues and compared the relative merits of various options, all of which are still under consideration. This paper focuses on one of these options - managed realignment - which offers a more sustainable alternative to the current energy intensive operating regime. This would involve the creation of around 130ha of semi-natural wetland flood storage by setting back river embankments, allowing the replacement of the main pumping station with tidal gates. Energy use would thus be reduced and the river would be allowed to function in a more natural manner, with benefits to wildlife and BAP targets.

07-4 Investing In Sustainability For Flood Warning & Defence

By: Alan Knott, BEng(Hons) CEng FIEE, (Parsons Brinckerhoff), Peter Kydd, BSc CEng MICE MCIWEM, (Parsons Brinckerhoff Ltd), Chris Cheek, BSc, MSc, CEng, MIEE (Parsons Brinckerhoff Ltd)

Key Words: Sustainability, Sustainable Development, Flood Warning & Defence, Investment Strategies

Abstract: Investment in Flood Warning and Defence in England & Wales is justified on a range of economic, environmental and social factors. The benefits of protection by defence and / or early warning and effective flood management are relatively easy to identify and yet many of them are difficult to quantify in economic terms. The avoidance of damage to property is relatively easy to quantify as a financial cost however the environmental and social effects of flooding are much more intangible. Much work has been done to highlight the social effects of flooding and this has resulted in significant investment in high profile, regular public awareness campaigns and the establishment of on-line information networks and advisory services. One aspect that has not received as much attention from an investment perspective however is the environmental impact of flooding and the associated effects of river and coastal defences.

Sustainability is seen as a key consideration in the development of our built environment and in this paper the authors combine their experience in this area with that of flood defence schemes, flood warning investment strategies and catchment management systems to draw out the sustainability benefits and consider ways in which these normally intangible factors can be valued.

07-5 Whole Life Costing for Flood and Coastal Defence

By: Jonathan Rogers MEng PhD CEng MICE (Mouchel Parkman), John Dora BSc CEng MICE, (Network Rail), Zoë Hutchison BSc CEng MICE (Mouchel Parkman)

Key Words: Costs, assets, management

Abstract: The work described in this paper forms part of Network Rail's Structures Annual Cost Profile (SACP) project undertaken by Mouchel Parkman (then Mouchel). The principal objective of the work was to estimate the minimum whole-life cost of maintenance to deliver the optimum service life of Network Rail's structural assets. SACP was developed, by Network Rail (then Railtrack), as a tool to aid the development of policy and strategy for long-term asset management, accounting for existing asset condition and future interventions. Taking a national perspective, it is unlike previous work in this area where asset management plans were prepared for short-term consideration at a territorial level.

Network Rail's assets include bridges, culverts, tunnels, earth structures and coastal and estuarial defences. This paper outlines the work undertaken for the coastal and estuarine defence component of the project.

The outline methodology is presented, which gives funders and decision-makers a useful tool for determining prioritisation of long-term budgets and budget mechanisms.

The estimates prepared for the 100 year period covered by the SACP are based on modelling, using a whole-life cost process, of the maintenance and replacement options for a representative sample of each asset type; the preferred option being that with the lowest whole-life cost.

The SACP process is based upon a Bayesian statistical model allowing efficient use of available data. The modelling process involves developing rules that are applied to every asset on the network to determine a preliminary estimate of costs (the "Preliminary Cost Model"). Sample assets are examined in much greater detail (using the "STructures Asset Management Process (STAMP)") and the results are combined within the statistical model (the "Engineering Cost Model") to provide the final cost profile.

Session 8: Policy Forum

08-1

At the last Flood and Coastal Management Conference, Defra proposed to develop a new strategy for flood and coastal erosion risk management for England. The aim of this is to update the existing Strategy for Flood and Coastal Defence, which was published by MAFF and the Welsh Office in 1993 and now needs updating in the light of drivers for change.

Session 9: Short Papers

09-1 Practical Steps Towards Improved Data And Information For Flood And Coastal Management

By: Keiran Millard MPhil. MSc. Beng (HR Wallingford Ltd), Jonathan Mccue BSc (Atkins Ltd.) Suresh Surendran PhD (Environment Agency)

Key words: Data Management, Standards, Strategy

Abstract: Agency/Defra's aim of flood and coastal management is "to reduce the risk to people, property and environment and to encourage sustainable development". Those responsible for Flood and Coastal Management (FCM) need a system that allows the assessment of risks now and in the future and an optimum programme of management interventions to achieve the above outcome. However, understanding how 'data' and 'information' impacts on this system is difficult to conceptualise because the FCM system is complex, with many stakeholders and multiple components of drivers and responses contributing before, during and after a flood event.

The joint Defra / Environment Agency R&D programme commissioned a research project (FD2314) under the Risk Evaluation and Understanding of Uncertainty Theme, to develop a strategic approach to FCM data and information, covering the whole 'cycle' of collection, dissemination and use of data for decision-making. The purpose of this project was to understand current data and information practices, and to suggest what opportunities exist to improve data and information management for FCM.

The R&D process included review, information gathering, conceptual modelling and consultation to arrive at a well-founded series of recommendations which would support data and information management. The conceptual framework used for this study considered FCM in the context of the Government's standard 'Source / Pathways or Barrier / Receptor / Consequence' (SPRC) approach to risk management (Defra/Agency 2002). A second framework was used to help understand how the topics in FCM relate to data and information management. This data management framework builds on work previously undertaken for the FCM industry on effective data management (CIRIA 2000, Agency 2002).

The results from the study are presented in the following chapters according to the five information management principles reported in FD2314/TR (Defra/Agency 2004) along with the proposed implementation plan.

09-2 Coastal Conservation And Flood Management

By: Tim Collins, BSc (English Nature) and Angela Moffat, BSc PhD (English Nature)

Key Words: Conservation, Management, Consultation

Abstract: English Nature is developing a new strategy for the conservation of the coastal and marine environment: - Our coasts and seas: A 21st century agenda for their recovery, conservation and sustainable use. This paper explains how this 'Agenda' refreshes English Nature's objectives for England's coasts and seas; it will act as a catalyst for future action. The ecosystem approach is central to the Agenda. It integrates the management of land, water and living resources and promotes conservation and sustainable use whilst recognising that people are an integral component of ecosystems.

09-3 Managing Urban Flood Risk - the Missing Dimension

By: Richard Kellagher (HR Wallingford Ltd) & Bridget Woods Ballard (HR Wallingford Ltd) John Packman (Centre for Ecology and Hydrology)

Key Words: None

Abstract: Relatively little attention has historically been given to the high insurance losses from urban flooding, but recent events mean that these flood risks are rising up the public agenda. The legacy of past development provides today's planners and engineers with significant challenges in building a sustainable future.

Threats to urban conurbations from poor management of runoff peak and volume include:

  • Flooding from ordinary watercourses;
  • Hydraulic overloading of sewers;
  • Buildings obstructing overland flow paths and flood ways; and
  • Local risks in high intensity storms when water cannot reach the drainage system safely.

The requirement to address urban flooding is compounded by the anticipated impacts of changes in climate, the requirements to provide better environmental protection, and the increasing demand for development, with several million houses to be built in the next few decades. New technical solutions are needed to meet this challenge. This includes understanding the risks in urban areas through whole catchment modelling, defending property with temporary defences, the use of source control and sustainable drainage to mitigate development impacts, and planning overland flood paths and temporary storage areas to reduce risks posed by inadequate sewer capacity and surcharging. However technical competence is one half of a coin, the other side of which is the mechanism of governance needed to ensure efficient and competent implementation of the best way forward.

This paper summarises current research into techniques to deal with flood management and mitigation and provides an overview of some of the deficiencies of the current responsibilities for flood management.

09-4 Flood Risks To People

By: David Ramsbottom, CEng MICE MCIWEM, (HR Wallingford Ltd), Suresh Surendran, (Environment Agency) Edmund Penning-Rowsell, (Flood Hazard Research Centre) Pete Floyd, (Risk & Policy Analysts Ltd)

Key words: Flood, Risk, People

Abstract: An aim of the Government's Flood and Coastal Defence Policy is to reduce risk to people and it is a priority area of the Defra/Agency Joint Flood and Coastal Defence R&D Programme. A Defra/Environment Agency research project is being undertaken in two phases, to develop a method to quantify flood risks to people. The purpose of the research is to enable Defra and the Environment Agency to identify the locations where there is a significant risk of loss of life or serious harm to people as a result of flooding.

09-5 Towards Best Practice Application Of Flood Forecasting Models

By: Kevin Tilford, MCIWEM (WS Atkins Consultants Ltd)
and Kevin Sene, CEng MICE MCIWEM (WS Atkins Consultants Ltd)
Rahman Khatibi CEng MICE MCIWEM (Environment Agency)

Key Words: Flood, Forecasting, Guidelines

Abstract: Flood warning systems can often provide an alternative or complement to the construction of flood defences. Flood forecasting models are increasingly being used to extend the accuracy and lead time of flood warnings in order to extend the coverage of the flood warning service and to permit the operation of washland and other storage systems to reduce the risk of flooding. Given the considerable investment planned in forecasting model development over the next few years, it is important to apply a consistent and cost effective approach to model selection, and in 2001-02 a set of guidelines was developed for the Environment Agency for use by practitioners to ensure consistency in approach and auditability. The guidelines summarise best practice based on consultations with practitioners and exploratory modelling studies, and consider not only the technical aspects of model selection, but also economic and operational factors.

09-6 Best Practice In Coastal Flood Forecasting

By: Peter Hawkes (HR Wallingford) Paul Sayers (HR Wallingford Ltd)
Rahman Khatibi (Environment Agency)

Key words: Flood Forecasting, Nearshore Modelling, Flood Mapping.

Abstract: A series of R&D projects was commissioned within the Flood Forecasting and Warning theme of the UK Government joint Defra / Environment Agency Research Programme for Flood Management. Unlike other more general forms of weather or ocean forecasting, flood forecasting focuses specifically on the probability of flooding, which depends on weather, ocean and defence conditions.

Defra commissioned HR Wallingford, Posford Haskoning and WS Atkins, under R&D Project FD2206, to produce best practice guidelines for coastal flood forecasting (CFF) services in England and Wales. The purpose of the project was to investigate ways of improving CFF and to provide best practice guidelines for the future development of CFF services. The objectives were to:

  • identify present and future flood forecast needs and aspirations
  • categorise available methods (for coastal flood forecasting) and identify advantages, disadvantages and inconsistencies
  • short-list a range of suitable (coastal flood forecasting) options and appraise their performance with regard to meeting present and future needs
  • outline the way forward for coastal flood forecasting including necessary R&D to fill any identified deficiencies in present practice
  • review existing initiatives and develop a common understanding of requirements and an associated best practice framework for coastal flood forecasting.

In risk assessment, one should consider all potential threats and all potential failure modes. In benefit / cost assessment, one should consider all costs throughout the life of the scheme and attempt to place values on intangible benefits. This paper attempts to introduce the same 'overall' approach to CFF. The aim is to maintain or enhance lead-time (i.e. the time between forecasting / warning and arrival of the impending floods) whilst meeting the requirements of the at-risk population in terms of the accuracy and reliability of forecasts. The paper will be of interest to anyone involved in flood forecasting, actions to mitigate forecast damage, or assessment of losses due to coastal flooding.

09-7 Hiflows-UK

By: Peter Spencer, (Environment Agency), Tim Palmer, (Black & Veatch Consulting Ltd), Paul Wass, (JBA Consulting)

Key Words: None

Abstract: This paper describes the HiFlows-UK project to extend and update the flow data and supplementary station information used with the Flood Estimation Handbook (FEH). The objectives were to:

  • Add recent data and additional gauging stations
  • Review data to produce a single authoritative dataset
  • Improve background information to assist users of the FEH to make valid decisions
  • Make data widely available via the internet
  • Establish structures and procedures for future updating and dissemination
09-8 Representing Land Use Change - The New Forest Experience

By: Angela Ogier, CPEng MIPENZ MICE,(Halcrow Group Ltd) Bryan Harvey,(Halcrow Group Ltd) CEng MICE and Alastair Pitcher (Environment Agency)

Key Words: Catchment Flood Management Plans, Flow Routing, Land Use Change

Abstract: Large-scale catchment-wide models are gaining importance given the need to develop catchment flood management plans. The modelling of land use change is integral to this process. However, it is not always practical to develop a highly detailed, hydrodynamic model of the catchment. A hydrologic routing model based on the Flood Estimation Handbook (FEH) rainfall-runoff method allows catchment-wide land use changes to be accounted for at a macro scale.

Simulating the effects of Forestry Commission Inclosure decommissioning in the New Forest required this type of large-scale modelling. The degree of change resulting from this regeneration of natural forest conditions was uncertain and needed to be assessed to see if forest restoration constituted a valid flood risk management option. A catchment-wide hydrologic routing model was created using iSIS and adjustments to the FEH parameters were made to simulate the altered catchment. The quantum of change was measured from the resultant hydrographs.

09-9 Coastal And Estuarine Managed Realignment: Design Issues

By: Craig Elliott (CIRIA) & Daniel Leggett (Babtie Group)

Key Words: None

Abstract: Coastal features, such as saltmarshes, mudflats, beaches, shingle ridges and sand dunes, act as natural flood defences and play an important role in flood management. They help absorb wave and tidal energy at the coast and can evolve, through time, to accommodate some of the impacts of sea level rise. The coastline is also a vital asset to the UK's biodiversity with some 1200 nationally protected sites and 180 internationally protected sites, designated for their biological or earth science interest features. Additionally, the coastline provides intrinsic landscape value with, for example, over 1500 km of Heritage Coast in England and Wales. There are many pressures on the coastline (e.g. development) that may impact upon the environment and require mitigation or compensation for those impacts. We therefore need to manage our coastlines with appropriate regard for the reduction of risks to coastal settlements and industries, alongside the conservation of habitats, biodiversity, geodiversity, heritage and landscape. Using adaptable natural coastal landforms and processes as part of this work can help ensure sustainable coastal management.

Managed Realignment can offer a long-term, sustainable, option for management of coasts and estuaries. It can reduce the pressures on flood defences by relocating them inland to lower energy environments or removing them to better manage flood risk over a wider area such as an estuary or coastal embayment. It can also compensate, or mitigate, for loss of habitat as a result of coastal "squeeze" (i.e. the loss of habitat seawards of flood defences) or development. Managed Realignment offers the potential for habitat creation and re-creation opportunities. The technique can, potentially, reduce resource use in comparison with hard defences by enabling the re-use of materials extracted from a site during construction. This can reduce the impact, and on occasion the cost, of construction compared with traditional approaches. In some circumstances however, costs might be higher in the short term, with savings only being realised in the longer term through the achievement of a more self-sustaining form of flood management and reduction in maintenance costs (Owen, 1984, Leggett & Dixon, 1994). It is also important to recognise that Managed Realignment might be applied to achieve land management targets (such as for biodiversity, landscape, public access, or other social purposes) outside of flood management needs and hence the cost compared with other management solutions may be more acceptable.

09-10 New Tools For Flood Level Estimation - Conveyance And Afflux Estimation Systems

By: Dr Mervyn Bramley, CEng FICE FIWEM, (Defra / EA Engineering R&D Theme Advisor)

Key Words: None

Abstract: Accurate estimation of flood water level underpins almost all sectors of flood risk management. Two new support tools - the Conveyance Estimation System (CES) for river flow and the Afflux Estimation System (AES) for bridges and culverts - have been commissioned by UK flood management authorities to ensure that best available methods relevant to conditions in the UK are used for flood risk management. Commercial versions of river flow software incorporating the CES are being released in 2004. The AES will be available in 2005. Open code versions of the estimation systems will be made available to researchers and software developers so that they can work with the system and feed back improvements to other users.

09-11 Establishing A Performance-Based Asset Management System For Flood Defences (PAMS)

By: Paul Sayers (HR Wallingford) and Jonathan Simm (HR Wallingford Ltd)
Fola Ogunyoye (Posford Haskoning), Ian Meadowcroft (Environment Agency)

Key Words: None

Abstract: An important element of flood risk management is managing flood defence assets such as channels, walls, embankments, gates and pump systems. This activity requires information, tools and techniques to assist decision-makers to ensure that assets perform as required under a range of conditions. Current approaches are relatively crude and not fully consistent with a risk-based approach. Improved decision-making will require important technical issues to be addressed, related to assessing risk and managing performance in a manner linked to the assessed risk.

A programme of research leading to a Performance-based Asset Management System (PAMS) will take measured steps to develop a risk-based approach for identifying and prioritising works to manage existing defences. This will support improved inspection, operation, maintenance and renewal of flood defence systems, helping the Agency and other operating authorities to reduce flood risk.

PAMS sits within and supports the Agency's Water Management Asset Strategy. Key issues emerging for water management asset management include:

  • Need for risk-based system asset management plans
  • Measurement of asset performance - move from asset condition to asset performance
  • Whole-life management of assets and asset systems
  • Prioritisation across capital and maintenance / operational expenditure
  • Design assets to meet multiple criteria
  • Respond to climate change

PAMS forms part of the overall data, modelling and decision framework being developed for flood risk management in England and Wales. The risk-based approach will follow the framework set out in the Review of Risk, Uncertainty and Performance (Defra / Environment Agency, 2002), available on the Agency web site. It will use risk information including that derived from country-wide assessments based on the RASP High Level Methodologies (Risk Assessment for Strategic Planning - see http://www.rasp-project.net/) and utilise more the detailed risk assessment methodologies being developed through RASP. PAMS will also draw on many other R&D projects for knowledge on behaviour, performance and reliability of a wide range of asset types.

This short paper outlines progress towards the development of PAMS, the next steps, and the longer term plan.

09-12 Floodsite - Integrating European Research On Flood Risk Management

By: Dr Paul Samuels CEng CMath FIMA MICE MCIWEM (HR Wallingford Ltd)
Mark Morris CEng MICE MCIWEM (HR Wallingford Ltd)
Eur Ing Paul Sayers CEng MICE (HR Wallingford Ltd)

Key Words: Flood Risk Assessment, Sustainability, Flood Warning

Abstract: The first round of the Sixth Framework Programme of the European Commission (2002-2006) includes an "Integrated Project" on flood risk management, called FLOODsite. HR Wallingford is coordinating this €14 Million project, which commenced on 1 March 2004 with funding from the EC (€9.7M) and associated national projects and contributions.

FLOODsite is the largest ever EC research project on floods, and is scheduled to take 5 years. It brings together scientists from many disciplines along with public and private sector involvement. The project consortium includes 36 institutions throughout the Member and Acceding Countries of the EU and the project addresses the environmental, ecological and socio-economic aspects of floods in order to provide a European approach to the management of flood risks from rivers, estuaries and the sea.

FLOODsite has key actions on:

  • Research on sources of flooding, the effectiveness of defences and the impact of floods;
  • Management of flood risks, from long-term planning to new technologies for flood warning;
  • Developing knowledge from analysing real flood cases in Belgium, the Czech Republic, France, Germany, Hungary, Italy, the Netherlands, Spain, and the UK;
  • Dissemination of this knowledge to professionals and the public.

This short paper describes the background to FLOODsite and its relation to UK policy and practice.

09-13 The Flood Risk Management Research Consortium Its Formation And Objectives

By: Dr Stephen Huntington, FREng, FICE, FCIWEM (HR Wallingford)
Prof Ian Cluckie, FREng, FICE, FCIWEM, FRMetSoc (University of Bristol)
Prof Garry Pender, FICE, FCIWEM (Heriot-Watt University) Prof Colin Thorne (University of Nottingham)

Key Words: None

Abstract: The EPSRC, in collaboration with the Defra/EA Joint R&D programme on Flood and Coastal Defence, NERC, the Scottish Executive and UKWIR, have agreed to fund an interdisciplinary research Consortium investigating the prediction and management of flood risk. The concept behind this innovative joint funding arrangement is that it allows the Consortium to combine the strengths of fundamental and near-market researchers and research philosophies in a truly multi-disciplinary programme. The research portfolio for the Consortium has been formulated to address key issues in flood science and engineering, while being consistent within the agreed objectives of the funders. The portfolio will include:

  • the short-term delivery of tools and techniques to support more accurate flood forecasting and warning, improvements to flood management infrastructure and reduction of flood risk to people, property and the environment;
  • the establishment of a programme of high quality science that will enhance our understanding of flooding and improve our ability to reduce flood risk through the development of sustainable flood management strategies.

Session 10: Best Practice in River Engineering

10-1 2D Modelling Of Floodplains - Is It Worth The Effort?

By: Jon Wicks, (Halcrow Group Ltd), Bill Syme, (WBM Pty Ltd), Mohamed Ahmed Ali Mohamed Hassan, (HR Wallingford Ltd), Binliang Lin, (Cardiff University) Owen Tarrant, (Environment Agency)

Key Words: Floods, Modelling, 2D

Abstract: Recent advances in computer hardware/software combined with increased availability of sufficiently accurate digital terrain data (eg LiDAR and SAR) means that 2D modelling of floodplain flow can now be considered for use in most flood risk management studies. However, 2D modelling is not necessarily the most appropriate technique and even when it is the appropriate technique there are many types of 2D models from which to select. Potential benefits of 2D modelling include more accurate flood depths and extents, facilitation of application of emergent Defra/Agency assessment methodologies (eg RASP), and, when combined with good visualisation software, improved communication of study results to non-modellers (including planners and the public).

A high profile comparative application of a range of 2D methods to a Tidal Thames embayment is discussed in this paper. The findings are generalised to provide best practice recommendations for the selection of a method that is appropriate for specific types of study. Combined 1D/2D approaches are considered to provide the best way forward for many floodplain modelling projects.

10-2 A Comedy Of Errors - Ten Modelling Mistakes - We Wish We Had Never Made

By: Jonathan Bartlett, MA, CEng, FCIWEM, MICE, (Black and Veatch Consulting Ltd).

Key words: Hydrology, Modelling, Design

Abstract: Mathematical modelling has become a trusted and essential part of river engineering and is the basis of wide-ranging flood defence strategy and costly designs. Technical improvements have been made as to the robustness and computational accuracy of such models. We have all become much more proficient in the building and calibration of models and in their subsequent use. However there are a number of basic mistakes that seem to be made over and over again by practitioners. This paper describes ten of these errors - maintaining strict anonymity for the modellers involved. It is hoped that this paper will remind senior practitioners of their less glorious moments, and hopefully prevent numbers of younger modellers from making the same mistakes.

10-3 A Practical Approach To Uncertainty In Conveyance Estimation

By: Caroline Mcgahey (HR Wallingford Ltd) and Dr Paul Samuels CEng CMath FIMA MICE MCIWEM (HR Wallingford Ltd)

Keywords: Flood Modelling, River Resistance, Uncertainty

Abstract: Water level prediction is essential for the management of flood management risks through strategic planning, risk mapping, scheme design, forecasting and warning, and channel operation and maintenance. Flood level predictions based on existing software provide no indication of the associated uncertainty. This uncertainty arises from many factors including approximations to the fluid mechanics, natural variability in river resistance and the use of judgement or experience in applying models. These all produce differences between assessment of river channel capacity and its "true" value. In 2001, the Environment Agency commissioned the development of a new conveyance estimation system to reduce the uncertainty associated with flood level predictions. A key component of this work was to quantify the uncertainty in water level for a given flow rate, and present it in a manner which can be readily interpreted by the user and enable better, more informed decisions. This paper provides insight into the selected approach, essentially driven by the identified end-users and their needs, together with a sensitivity analysis of the parameters contributing to the uncertainty.

10-4 Good Practice In Design And Management Of Flood Embankments

By: Mark Morris, (HR Wallingford Ltd), Dr Mervyn Bramley, (Environment Agency) and Dr Philip Smith, (Posford Haskoning)

Key Words: None

Abstract: A guide on good practice in the inspection, planning, design and management of the 35 000km of flood and coastal defence embankments in England and Wales has been produced under the Defra / Environment Agency R&D Programme (Project FD2411). The process of benchmarking current practice confirmed the need for a guide that draws together the wealth of practical experience and new knowledge and sets this out within a logical framework developed specifically for flood defence embankments. The resulting risk-based management framework builds on an understanding of function, condition and performance. It adopts a holistic approach to consider the geotechnical and hydraulic processes that can affect embankment performance and sets out a step-by-step approach to prioritising the need for inspection, investigation and remediation. A Good Practice Guide presents key issues, current knowledge and understanding, and sets out recommended actions and references for the mains areas of need identified by practitioners. The approach set out by the guide will be presented together with a selection of illustrations showing how practical knowledge, engineering judgement and scientific principles can be applied.

10-5 Catchment Modelling For Catchment Flood Management Plans

By: David Ramsbottom, CEng MICE MCIWEM, (HR Wallingford Ltd) Darren Lumbroso, CEng MICE MCIWEM (HR Wallingford Ltd) and Mark Davison, (HR Wallingford Ltd)

Key Words: Catchment, Flood, Modelling

Abstract: Catchment Flood Management Plans (CFMPs) are being undertaken for all river catchments in England and Wales. Catchment modelling is required to predict the effect on flood risk of future land use change and climate change, and possible future flood management policies. A method of catchment modelling has been developed as part of the Modelling and Decision Support Framework (MDSF).

This paper briefly describes the catchment modelling approach recommended for CFMPs and application to several catchments including the Thames upstream of Teddington. Issues arising from experience in using the approach are also discussed.

Session 11: Planning for the Future

11-1 Climate Change and Flood Frequency In the UK

By: Nick Reynard (CEH Wallingford), Sue Crooks (CEH Wallingford), Rob Wilby (Environment Agency) And Alison Kay (CEH Wallingford)

Key Words: Flood Frequency, Climate Change, Downscaling, Uncertainty.

Abstract: Global warming is predicted to cause significant changes to the world's climate, but uncertainties remain about the precise nature of these changes. This is particularly true with regard to possible changes at a regional or local level and to changes in the climate extremes that produce catchment flooding. Such changes might include more frequent short-duration, high-intensity rainfall or more frequent periods of long-duration, sustained rainfall of the type responsible for the Autumn 2000 floods. To address the uncertainty surrounding this issue, Defra guidance on flood defence scheme appraisal currently suggests sensitivity allowances for climate change, for example a 20% increase in peak flows over the next 50 years.

The need to further develop this policy and guidance on climate change impacts is being informed by improved modelling capabilities and climate change scenarios. For example, statistical rainfall models and fine resolution regional climate model data are now available to drive the hydrological models used to investigate the potential impacts of climate change on flood flows. CEH-Wallingford has been commissioned by Defra and the Environment Agency to use these data sets and models to assess the impacts and this paper describes the final project results for a range of catchments across the UK.

The results from this research show a wide range of impacts on peak flows, showing both increases and decreases, depending on the location and the characteristics of the catchments. However, all but the most extreme increases are within the 20% range of sensitivity testing currently recommended by Defra. Until more specific regionalised guidance, or guidance based on responses due to catchment characteristic can be provided this appears to remain an appropriate response to the uncertainty in climate change impacts on peak flows over the next 50 years.

11-2 The Impact Of Climate Change Upon Coastal Defence Structures

By: