Thames Estuary Pilot - FLOODsite · Thames Estuary Pilot EXECUTIVE SUMMARYOF TASK 24 April 2009...

Integrated Flood Risk Analysis and Management Methodologies

Thames Estuary Pilot EXECUTIVE SUMMARYOF TASK 24

April 2009

Report Number T24-07-01 Revision Number 2_0_P01

Task Leader HR Wallingford

FLOODsite is co-funded by the European Community Sixth Framework Programme for European Research and Technological Development (2002-2006)

FLOODsite is an Integrated Project in the Global Change and Eco-systems Sub-Priority Start date March 2004, duration 5 Years

Document Dissemination

PU Public PU PP Restricted to other programme participants (including the Commission Services)

RE Restricted to a group specified by the consortium (including the Commission Services)

CO Confidential, only for members of the consortium (including the Commission Services)

Co-ordinator: HR Wallingford, UK Project Contract No: GOCE-CT-2004-505420 Project website: www.floodsite.net

Executive Summary of Thames Pilot Contract No:GOCE-CT-2004-505420

T24_07_01_Thames_Pilot_Exec_Summary_V2_0_P01.doc 17/04/2009

DOCUMENT INFORMATION Title Thames Estuary Pilot - Executive Summary of Task 24 Lead Author Ben Gouldby Contributors Paul Sayers, Caroline McGahey, David Ramsbottom, Greer Kingston Distribution Public Document Reference T24-07-01

DOCUMENT HISTORY

Date Revision Prepared by Organisation Approved by Notes 15.12.07 1_0_Pn Ben Gouldby HR Wallingford draft 15.04.2009 1.1 Ben Gouldby HR Wallingford Text update. 17/04/09 2_0 Paul Samuels HR Wallingford Paul Samuels Final checking and approval

ACKNOWLEDGEMENT The work described in this publication was supported by the European Community’s Sixth Framework Programme through the grant to the budget of the Integrated Project FLOODsite, Contract GOCE-CT-2004-505420. DISCLAIMER This document reflects only the authors’ views and not those of the European Community. This work may rely on data from sources external to the FLOODsite project Consortium. Members of the Consortium do not accept liability for loss or damage suffered by any third party as a result of errors or inaccuracies in such data. The information in this document is provided “as is” and no guarantee or warranty is given that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and neither the European Community nor any member of the FLOODsite Consortium is liable for any use that may be made of the information. RELATED DOCUMENTS The full reports to which this summary relates are available from the FLOODsite Project Website at http://www.floodsite.net/ © 2009 Members of the FLOODsite Consortium


T24_07_01_Thames_Pilot_Exec_Summary_V2_0_P01.doc 17/04/2009 iii

CONTENTS Document Information i Document History i Acknowledgement i Disclaimer i Related Documents i Contents iii THAMES ESTUARY PILOT - EXECUTIVE SUMMARY OF TASK 24

1. Scope of the research in Task 24........................................................................................... 1 1.1 Overview .................................................................................................................. 1 1.2 Links with other FLOODsite tasks ........................................................................... 1

2. Principal results ..................................................................................................................... 3 2.1 The flood risk model................................................................................................. 3 2.2 Uncertainty and sensitivity method .......................................................................... 5

3. Application to the Thames Estuary ....................................................................................... 7 3.1 Background to flooding on the Thames.................................................................... 7 3.2 Future drivers of flood risk ....................................................................................... 7 3.3 Ongoing flood risk management studies .................................................................. 8 3.4 Results ...................................................................................................................... 8

4. Relevance to practice .......................................................................................................... 11 4.1 Flood risk model..................................................................................................... 11 4.2 Uncertainty and sensitivity method ........................................................................ 12

5. Remaining gaps in knowledge ............................................................................................ 12

6. Acknowledgements ............................................................................................................. 13

7. Disclaimer ........................................................................................................................... 13

8. References ........................................................................................................................... 13 Figures Figure 1 Task 24 links to other FLOODsite tasks 2 Figure 2 Task 7 Reliability tool, used to derive inputs to the Task 24 model 2 Figure 3 Conceptual backdrop of the flood risk model 3 Figure 4 Example output from the Rapid flood spreading model on the Thames Estuary 4 Figure 5 A Conceptual diagram showing the structure of the uncertainty and sensitivity method 6 Figure 6 Return period damages for the Thames System under a P3 policy High+ climate change scenario. 10 Figure 7 Change in risk through time, P3 Policy and High Level Option 2, under the Defra climate change scenario 10 Figure 8 Map showing annual probability of inundation (Thames Barrier not operated) 11 Figure 9 Contributions to defence overtopping volume for a given return period event (20, 80, 200 and 1000yrs shown) 12


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Thames Estuary Pilot - Executive Summary of Task 24 1. Scope of the research in Task 24 1.1 Overview The scope of Task 24 comprised: • Development of a model that quantifies flood risk • Application of the model to the Thames Estuary for the purposes of asset management and strategic

flood risk management. • Development of a method for quantifying uncertainty and sensitivity of the flood risk model. Sound flood risk management decision-making is underpinned by flood risk analysis. Traditional methods applied at regional and local-scales are often limited in their consideration of the potential for defences to fail. Ultimately this can lead to underestimates of the true risk and subsequent difficulties in justifying mitigation measures such as maintenance and replacement of defences. In FLOODsite, Task 24 has developed a methodology for assessing flood risk arising from fluvial and coastal sources that explicitly considers defence failures represented through fragility curves. This method requires consideration of numerous flooding scenarios involving multiple defence section failures and flood events ranging in severity. It has therefore been necessary to develop a purpose-specific flood spreading method that is capable of simulating many flood events in practical timescales. The flood spreading method has the unique capability of being able to track flood water from its origin (breached or overtopped defence), as it flows across the floodplain. This enables economic damages and risk to be attributed to specific defence sections. The method has been applied to the Thames Estuary, where outputs including spatial maps of flood risk, and defences attributed with residual risk have been used to support decisions relating to strategic flood risk management over the coming century. A method that enables the propagation of uncertainty through the modelling system has also been developed. The model comprises components that relate to the conceptual Source Pathway Receptor risk model. The inputs include information relating to extreme hydraulic loads on the defences, fragility of the flood defences, floodplain topography and the location of property and infrastructure in the floodplain. The primary outputs of the model are: • Spatial variation (typically presented in map format) of flood risk (typically expressed as Expected

Annual Damage (EAD). • Spatial variation (typically presented in map format) of flood inundation probability. • The contribution that each individual asset (flood defence structure) makes to the residual flood

risk.

1.2 Links with other FLOODsite tasks Task 24 has linked with a number of other FLOODsite Tasks. These links are illustrated in Figure 1. Particularly close links have been realised with Task 7, where a new reliability software tool (Figure 2) has been used to derive site specific fragility curves1 that are used within the Task 24 model. The Task 24 modelling system has also been extensively employed on Tasks 14 and 18.

1 Fragility curves express the probability of components of flood defences to fail under a range of loading conditions



Figure 1 Task 24 links to other FLOODsite tasks

Figure 2 Task 7 Reliability tool, used to derive inputs to the Task 24 model

Job n: TE2100

Version 1.0 User: BPG01-Jul-08 Date: 26-Jun-08

Structure Name EX8 Failure Mode Summary Name Calls Fail Ratio

Name Distribution Annual Reliability 1CrestH F (Fixed) 7.5 Annual Probability of Failure 0DissCoeff F (Fixed) 1 4 Converged YESGrassRevQ N (Normal) 1.05 0.07 Convergence Factor 0Grav F (Fixed) 9.81 4 Samples 2200InsSlopeAng F (Fixed) 17.49 4 Time Taken (seconds) 0KdKf N (Normal) 0.4 0.03 Mannings F (Fixed) 1 MBA1_1R F (Fixed) 1 4 MBA1_1S F (Fixed) 1 4 Min Samples 2000OverPercen F (Fixed) 1 4 Max Samples 100000StormD N (Normal) 3 0.65 Interval 200WaterL V (Variable) 7.5 0.01 8 Convergence Factor 0.001

Successive Intervals 1

Events Per year 1Optimise YESLog each Sample NOLog each LSE call NOFailure Mode Summary Yes

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Task 20 Uncertainty analysis

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2. Principal results 2.1 The flood risk model The flood risk analysis model developed on Task 24 is described in detail in Gouldby et al (2008a), an overview is provided here. The modelled flood system, depicted in Figure 3, shows a floodplain area protected from a river channel (or coast or estuary) by a series of n discrete flood defences (d1, d2… dn). Each defence section is considered to have an independent and different resistance to flood loading. These are characterised by, for example, different types of structure (i.e. different geometry or materials), crest levels or condition grade. Defence section parameters, for example crest level, are assumed to be constant within any given section. The floodplain area is discretised into a series of Impact Zones (z1, z2… zm). Any specified Impact Zone can be affected by flood water discharged through any of the defences that protect it.

Figure 3 Conceptual backdrop of the flood risk model

The hydraulic loads on the defences are defined as a continuous random variable and characterised by extreme value distributions associated with each defence. Defence failure (structural failure) is defined as a continuous random variable, conditional on load (these distributions are often referred to as fragility curves). During any flood event each individual defence section can exist in two possible states, failed or not failed with the likelihood of any particular state obtained with reference to the fragility curves. The continuous line of defence sections forms a defence system. The potential number of defence system states (combinations of failed/not failed defences), for any specified hydraulic load, is 2n. Flood volumes discharged through (or over) any given defence section during any flood event are a function of the state of each defence section and therefore the defence system state. The flood depth in any impact cell is a function of the defence system state. In practice, however, the number of defences in a system can often exceed 100 (i.e. more than 2100 possible defence system states). This can pose problems in terms of computational time to simulate the many thousands of flood events. The solution adopted to solve this problem is two-fold, comprising numerical approximation using a Monte-Carlo technique coupled with a computationally efficient hydraulic flood spreading method. The Monte-Carlo simulation approach involves the random sampling of defence system states based upon the defence fragility curves. The hydraulic flood spreading model involves the division of the

Impact Zones (IZ)

River

IZj

IZj+1

IZj+2 IZj+3

IZj+4

Flood Defences

Impact Cells (IC)

d1 d2 d3 d4



floodplain into a series of self contained topographical depressions (“basins”), known as Impact zones. For flood event hydraulic simulations, flood volumes obtained from each defence length are discharged into their neighbouring Impact Zones (these are termed adjacent Impact Zones.), which then become activated. The volume of water within an active Impact Zone is compared to the capacity of the basin and an excess volume is calculated and discharged into the appropriate neighbouring Impact Zone/s. The results obtained are a depth grid resolved to Impact Cell scale. To validate the quality of the hydraulic simulations the model has been compared with a hydrodynamic model that solves the 2D shallow water equations over a range of different flooding scenarios. Example output from the hydraulic spreading model is shown in Figure 4. With knowledge of the type, floor area and number of properties within each Impact Zone, it is possible to estimate the economic consequences of flooding due to property damage. Each modelled flood event (loading event and sampled defence system state) results in a flood depth grid over the floodplain area and hence a flood event economic damage. The hydraulic spreading model has the unique capability of being able to track the water as it propagates across the floodplain. This enables risk to be attributed to individual defence sections.

Figure 4 Example output from the Rapid flood spreading model on the Thames Estuary

The model quantifies flood risk at a specific point in time. The input databases can be modified to reflect future changes to the system associated with, for example, different: • climate change scenarios • asset maintenance strategies • Long term flood risk management strategies, including flood warning or resilience measures (so-

called receptor or non-structural responses). • floodplain development scenarios One of the primary uses of the model is, therefore, to analyse the performance of different flood risk management strategies within a benefit-cost framework. This model enables a quantification of the benefits of the flood risk management strategy



2.2 Uncertainty and sensitivity method It is important for decision-makers to be aware of the limitations associated with models. Risk modelling is an inexact science and uncertainties are present from numerous different sources. Where no data are available with which to ‘condition’ a numerical model, forward propagating uncertainty techniques are the only viable approach for uncertainty analysis. Of the options available, Monte-Carlo procedures are the most flexible, robust and therefore prevalent. These methods involve assigning probability distributions to input variables and propagating these through any given function or combination of functions (i.e. a model). These approaches can be computationally time consuming to implement, particularly where model structures are complex. A staged method (Gouldby and Kingston 2007) has therefore been developed on Task 24 that quantifies the uncertainty associated with the flood risk model. The scientific advances within the piece of work are the efficiencies that are achieved through selecting appropriate staging points within the overall model structure, to make the propagation of uncertainties achievable within a practical computational timeframe. Sensitivity analysis seeks to identify those input variables that contribute most to uncertainty on the output variable. The output of this analysis can be used to identify priorities in development of the model, for example, to target data gathering activities to the most important input variables. A technique for sensitivity analysis that has been used before in a variety of different fields is Variance Based Sensitivity Analysis (VBSA) (Saltelli et al. 2004). This has been proven to be a robust approach and offers a number of advantages over other approaches, such as local sensitivity analysis methods (see Saltelli et al. 2004). This method has therefore been adopted for this application. The model output variance, determined from the uncertainty analysis, is some function of the variance, or uncertainty, in the model inputs. By “fixing” the value of an input parameter of interest (in order to represent the case in which the value of this input is known with a high degree of certainty), while varying all others, the expected reduction in the output variance that can be determined. There is however, the possibility that combinations of input variables interacting with each other can contribute significantly to the variance of the model output. A conceptual diagram showing the structure of the uncertainty calculations is shown in Figure 5.

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3. Application to the Thames Estuary 3.1 Background to flooding on the Thames The Thames Estuary, located in the south-east of England, is an area of national importance. As host to London, the capital of England, over 1million people live in the floodplain area. The area comprises extensive Central and Local Government institutions. The Thames Estuary (in particular the outer estuary) also has a wide range of landscapes of high environmental value. These include national and international sites designated for protection such as saltmarsh, mudflats, freshwater grazing marsh and reed-beds. These areas support diverse species and provide habitats for wildfowl and waders, for example. The implications of flood risk management interventions on these areas are a primary consideration for the development of future plans. Flood risk arises on the Thames Estuary from a number of different sources: occurrences of high surges in the North Sea; fluvial flooding on the Thames and fluvial flooding on tributaries of the Thames. By far the greatest potential risk arises from tidal surges and in 1953 such an event caused widespread flooding and damage along the Thames floodplain. To counteract this threat the Thames Barrier and associated defences were constructed, becoming operational in 1982. As well as the Thames Barrier, nine other surge tidal excluding barriers have been constructed, downstream of the Thames Barrier, where tributaries join the Thames. Forecast and real time data on the tidal conditions in the North Sea are used to ensure these barriers and the Thames Barrier are closed simultaneously, prior to extreme tidal flood events in the Thames Estuary. Protection against fluvial flooding on the Thames is provided by fixed defences upstream of the Thames Barrier. There are approximately 280km of raised flood defences on the Thames with approximately 200km of tributary defences. These static defences vary in type, the most common are earth embankments, steel sheet piled vertical walls and concrete/brick structures. In extreme fluvial flow events on the Thames, closure of the Thames Barrier at low tide provides a storage volume upriver of the Barrier, thus minimising the risk of ‘backing-up’ of fluvial flows by the tide and maintaining conveyance in the upper estuary reaches (west London). Similarly protection against fluvial flooding on tributaries with barriers is provided by flood defences (which have a lower level than on the Thames) and closure of barriers at low tide.

3.2 Future drivers of flood risk Flood risk is a dynamic quantity and when developing a strategic flood risk management plan it is important to identify the future drivers of changing flood risk. Two of the primary drivers on the Thames Estuary are future floodplain development, increasing the number of people and property on the floodplain and climate change, which could see an increase in the frequency and severity of extreme events. With regard to the former, whilst there are difficulties in projecting future developments in the longer term, in the near term there are ongoing initiatives, for example, the Thames Gateway regeneration, that give an indication of the likely developments occurring over the near term (20-30 years). The Thames Gateway comprises nearly 10,000 hectares (more than 35 square miles) of land, running along the River Thames, east from the Isle of Dogs to the edge of London. It is now however, been identified as London’s prime growth corridor. The next twenty years will see partners working together to build on the success of Canary Wharf, Crossrail, and the 2012 Games, in order to make the most of the area’s extraordinary opportunities. Climate change can also influence future flood risk in a variety of ways, for example changes in: extreme sea level at high water (relative to land level, and including surge); extreme river flow; extreme rainfall (possibly for more than one duration); extreme wave conditions (deep water wave height and period); dependence between any relevant pairings of the above or mean sea level (relative to land level). The lowering of land level in London (isostatic effect) is also considered of significance for flood risk, UKCIP (2002). Estimates of the rise in absolute mean sea level (ice melt



and heat expansion effects) are provided, for different emissions scenarios in UKCIP (2002) and more recently, IPCC (2007). Whilst there is a significant amount of evidence to support the estimates of future sea level rise and other climate change related phenomena, there is still significant uncertainty associated with future projections.

3.3 Ongoing flood risk management studies During the course of the FLOODsite Research Project, the EA has undertaken a project to develop a long term flood risk management plan for the estuary, the so-called TE2100 Project. The aims of the TE2100 Project are (EA (2008)) detailed below: “Thames Estuary 2100 (TE2100) is an Environment Agency project to develop a tidal flood risk management plan for the Thames estuary through to the end of the century. The final plan will recommend what flood risk management measures will be required in the estuary, where they will be needed, and when over the coming century, based upon the climate changes and sea level rises we face. The plan will take into account the increasing flood risk due to: Climate change; rising sea levels; natural ageing of flood defence infrastructure; changes in land levels and new development in the tidal flood plain.”

3.4 Results The flood risk analysis model has been used in a preliminary investigation of the benefits of some potential risk management options. The pro-active management of flood risk promoted by the Environment Agency, and adopted within TE2100 sees a number of timed interventions, each seeking to manage risk within an acceptable zone. This concept recognises that risk is set to increase in the future as the drivers for change (climate change, continued development in floodplain and asset deterioration) all act on the system to increase risk. A definition of the core TE2100 management policies is provided in Table 1. The P1 Policy is regarded as the baseline or “do nothing” case, against which the other inventions are compared to determine the intervention benefit. Table 1: Policy definitions

Policy Number

Policy definition

P1 No active intervention (including flood warning and maintenance), continue to monitor and advise

P2 Reduce existing flood risk management actions (accepting that flood risk will increase with time)

P3 Continue with existing and alternative actions to manage flood risk at the current level (accepting that flood risk will increase over time from this baseline)

P4 Take further action to sustain the current level of flood risk into the future (responding to the potential increases in risk from urban development, land use change and climate change)

P5 Take further action to reduce flood risk (now and/or in the future) Table 2 summarises the intervention actions, including future date, for two High Level Options (HLO 1 and 2). The main difference between the two options is the introduction of flood storage systems in the outer estuary. These systems reduce the volume of water propagating upstream and therefore reduce the loading on upstream defences.



Table 2 Description of the HLO interventions

Epoch Intervention action HLO 1

2040 • Re-profile channel navigation channel (West London) • Managed retreat, in the Outer Estuary • Outer Estuary defences raised by 0.3m

2070 • Managed retreat in the Outer Estuary • Over-rotate the Thames Barrier, reduces upstream loads • Defences raised by 0.5m • Some new defences

2085 • Restore interim defences upstream of the Thames Barrier HLO 2

2040 • re-profile channel navigation channel (West London) • managed retreat, in the Outer Estuary • Defences raised by 0.3m

2070 • managed retreat in the Outer Estuary • flood storage areas • over-rotate the Thames Barrier • Defences raised by 0.3m • Some new defences, including managed retreat

2085 • Restore interim defences upstream of the Thames Barrier The interventions have been assessed against a range of climate change scenarios. These scenarios are referred to as: Defra (using the current guidance for England and Wales); Medium High (based on a Medium High emissions scenarios and High. The model has been run for a range of management intervention scenarios, over the 100 year appraisal period. Typically four epochs are modelled for a given intervention and climate change scenario. Some sample results from this analysis are presented below. Figure 6 shows some sample results for the P3 policy (routine maintenance). The Present Day risk is low at <£5m, reflecting the high degree of protection afforded by the existing system. The barriers and the existing defences, with crest levels set higher than a nominal 1000 year water level, restrict significant damages occurring in flood events with greater than 2000 year return periods. Under an intervention scenario whereby the state of the defences and the reliability of the barriers are assumed to be maintained at present day levels, the annual risk increases to £55m in the year 2100, if the UK recommended allowance for climate change is realised. This is more than an order of magnitude higher than the Present Day. If however, a more extreme climate change scenario is assumed, the risk can rise to almost two orders of magnitude higher than the Present Day. It is therefore evident that there is potential economic justification for implementing a risk management plan to mitigate this increase in risk. Figure 7 shows the risk profile through time of the P3 policy and HLO 2 under the Defra climate change scenario. There is little difference in risk profile between the two intervention scenarios until the middle of the century, where a divergence occurs. Under the P3 Policy, the EAD increases significantly when compared to the HLO 2, and by the end of the century the difference in risk under the P3 policy has risen to around a factor of 5 higher than the HLO 2. Closer inspection of the model results has shown that over 90% of the difference in risk profile, in this climate change scenario, can be attributed to a significant increase in risk in the Outer Estuary. This increase is due to the lower (than those upstream) defences in the outer estuary and the amount of sea level rise that occurs under the Defra climate change scenario. A flood inundation map for the Present Day P1 policy (Barriers not operated), is shown in Figure 8. Further discussion of these results is provided in Gouldby et al (2008b)



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Figure 8 Map showing annual probability of inundation (Thames Barrier not operated).

4. Relevance to practice 4.1 Flood risk model The flood risk methodology that has been developed on Task 24 has been utilised on the UK Environment Agency’s Thames Estuary 2100 Project (TE2100). This project involves the economic appraisal of different flood risk management interventions options over the coming century, and given the nature and value of the assets at risk, the study is recognised as being the most significant strategic flood risk assessment ever undertaken within the UK. Given the level of importance of the study, the model has been formally reviewed by a panel of over eight experts in the field. The panel concluded the model was fit for purpose and suitable for detailed economic appraisal of options. As well as being utilised on the Environment Agency’s TE2100 study, the model has also been applied for use in the Environment Agency’s National Flood Risk Assessment of England and Wales (NAFRA). This assessment is used for the economic justification of expenditure on flood risk management within England and Wales. The FLOODsite model has proven to be both computationally more efficient and more accurate than its predecessor. The work on the Thames has also been of high value to the Environment Agency’s Performance Based Asset Management (PAMS) Project. The pioneering work attributing residual risk to flood defence assets is of significant importance to asset management teams seeking to prioritise maintenance work. The modelling system has formed the basis for the pilot site studies performed on the Great Eau and West Bay in England. It is envisaged that this modelling approach will be a core module of the Environment Agency’s PAMS software system when it is developed. The Environment Agency has commissioned a study to translate the modelling system developed on Task 24, into a software product. This product will be known as the Modelling and Decision Support Framework 2 (MDSF2). This software product will be utilised by Environment Agency staff and other consultants for catchment scale flood risk analyses and other analyses related to strategic flood risk management.



4.2 Uncertainty and sensitivity method Every year, there is a requirement to identify the input variables that contribute most to the uncertainty on the national flood risk assessment. There is also a requirement to present information on the uncertainty associated with the analysis. The Environment Agency commissioned the application of the Task 24 uncertainty and sensitivity method to a number of catchments that comprise an element of the national flood risk assessment, with the specific aim of addressing these requirements. Example output from this study is shown in Figure 9. It is anticipated that this method will ultimately incorporated within the MDSF2 and the PAMS software products

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Figure 9 Contributions to defence overtopping volume for a given return period event (20, 80, 200

and 1000yrs shown)

5. Remaining gaps in knowledge There is a requirement to refine the assumptions of the flood risk model relating to breach size with latest methods being developed under FLOODsite and other research in progress. Whilst it has been largely established how these methods can be linked, this now needs to be implemented and trialled in practice. The staged uncertainty and sensitivity analysis should be combined with uncertainty analysis relating to cost, within the context of economic appraisal. This would enable a demonstration of decision making relating to flood risk management intervention options, using Utility Theory, which accounts for uncertainties in the relevant input quantities. Parts of the flood risk management sector are still sceptical about the use of risk and uncertainty analysis and demonstrating these approaches within the context of significant study like the Thames will lend significant credibility to these approaches. Consideration of the robustness of different intervention options requires significant further effort before these approaches can be established in practice.



6. Acknowledgements The authors would like to acknowledge the contribution of a number of other parties who have been instrumental in the success of FLOODsite and the Thames Estuary Partnership and without whom the value of the work would have been greatly diminished: • Mervyn Bramley – Independent Consultant

(Expert advisor to the Environment Agency’s Sustainable Asset Management R&D Theme)

• Chrissy Mitchell – Environment Agency (Manager of the Environment Agency’s Sustainable Asset Management Theme)

• Owen Tarrant – Environment Agency (TE 2100 – Technical leader)

• Suresh Surendran – Environment Agency (Manager of the Environment Agency’s Modelling and Risk R&D Theme)

7. Disclaimer Whilst there has been interaction between the TE2100 Project and this project, the information provided in this report presents philosophies and results of the FLOODsite Integrated Project and does not in any way represent output from the TE2100 Project.

8. References 1. Gouldby, B and G Kingston (2007). Uncertainty and sensitivity method for flood risk analysis.

FLOODsite research report, HR Wallingford. 2. Gouldby, B, Sayers P, Mulet-Marti J, Hassan M and Benwell D (2008a). "A methodology for

regional-scale flood risk assessment." Proceedings of the Institution of Civil Engineers, Water Management , Vol. 161, June.

3. Gouldby B, Tarrant O and Sayers P (2008b) “Application of a flood risk model to the Thames

Estuary for economic benefit assessment.” Sixth International Conference on Computer Simulation Risk Analysis and Hazard Mitigation.

4. Saltelli, A., S. Tarantola, F. Campolongo and M. Ratto (2004). Sensitivity Analysis in Practice

- A Guide to Assessing Scientific Models. Chichester, England, John Wiley & Sons, Ltd.

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