Developing SLR adaptation strategy for the Thames Estuary (TE2100) Jonathan Simm HR Wallingford, UK

Transcription

1 Developing SLR adaptation strategy for the Thames Estuary (TE2100) Jonathan Simm HR Wallingford, UK

2 Outline The Thames in context Use of indicators and tipping points The TE2100 journey Option development The final (consultation) plan Page 2

3 Thames in context Loadings (Sources) River Lee River Roding Barking Waves Canvey Island Westminster Fluvial Flows Richmond Greenwich Purfleet Tilbury Sea levels (tide Gravesendand surge) Legend Tidal flood risk area Tidal flood defences Thames Barrier Other barriers Flood control gates Teddington weir 10km Page 3

4 Thames in context Defences (in Pathways) River Lee River Roding Barking Canvey Island Westminster Purfleet Tilbury Richmond Greenwich Gravesend Legend Tidal flood risk area Tidal flood defences Thames Barrier Other barriers Flood control gates Teddington weir 10km Page 4

5 Thames in context what is at risk (Receptors) Central and Local Government >80,000 civil servants River Lee River Roding Barking Canvey Island Westminster Purfleet Tilbury Richmond Greenwich Gravesend Legend Commercial centre of the UK Tidal flood risk area Other barriers Tidal flood 250b Historical defencesannual contribution buildings of Flood control Thames Barrier gates Teddington weir significant cultural value 10km Page 5

6 Thames in context System Pressures Thames Gateway Project 200,000 new jobs and commercial development (incl. Olympic Park (2012)) Page 6

7 Broad input assumptions Sea level rise in the Thames over the next century due to thermal expansion of the oceans, melting glaciers and polar ice is likely to be between 20cm and 90cm. There remains a lot of uncertainty over the contribution of polar ice melt to increasing sea level rise. At the extreme, it may cause sea level to rise by a total of up to 2 m (including thermal expansion) although this is thought to be highly unlikely. Upper limit assumed to be 2.7m Climate change is less likely to increase storm surge height and frequency in the North Sea than previously thought. Future peak freshwater flows for the Thames, at Kingston for instance, could increase by around 40% by Page 7

8 Some questions What will London and the Thames Estuary look like in 100 years? How will public attitudes to flood risk and the environment change over this time? Flood risk today, and in the future? What are the best ways of managing this risk?.. ensuring Plan is adaptable to change and remains fit for purpose for 100 years?.. Presenting Plan ed in a way which promotes multipartner working (key Pitt recommendation) Page 8

9 TE2100 HEADLINE OBJECTIVES: To manage the risk of flooding to people, and minimise the adverse impacts of flooding to property and the environment; To adapt to the challenges that we will face from climate change; To support and inform the land use planning process to ensure appropriate, sustainable and resilient development in the tidal floodplain; To protect the social, cultural and commercial value of the tidal River, its tidal tributaries and its floodplains; To enhance and restore estuarine ecosystems to contribute to biodiversity targets and maximise the environmental benefits of natural floods. Page 9

10 The traditional response to floods in the Thames (picture courtesy: Rachael Hill, Environment Agency) Page 10

11 Indicator value (e.g. sea level rise) Tipping points: thresholds, lead times and decision points Threshold value of indicator when intervention is needed Decision point based on best estimate Predicted values of indicator based on rate of change Recorded values of indicator Date of review Lead time for planning and construction Time Page 11

12 Impact of change on Decision Points Indicator value (e.g. sea level rise) Threshold value of indicator when intervention is needed New Decision Point based on best estimate Decision Point in Plan New Decision Point based on best estimate Lead time for planning and construction Predicted values of indicator based on rate of change Recorded values of indicator Assumed values of indicator in Plan Date of review Change in date of Decision Point Time Page 12

13 Area of intertidal mudflat and saltmarsh (depends on Mean Sea Level rise and morphological change) Managed realignment area 1 Managed realignment area 2 Managed realignment area 3 Managed realignment area 4 Threshold 1 Present day area Area with no interventions Time Notes: 1. The portfolios of responses are designed to keep the area of mudflat and saltmarsh above present-day level. 2. The timing of realignments is to a large degree dependent on when existing defences would otherwise require replacement. Page Impact of Mean Sea Level increase (and other changes) on habitat area

14 Managing flood risk over the century Page 14

15 Risk indicator (probability x consequence) Pathway (e.g. beach, raised/non-raised defence and floodplain) Receptor (e.g. people and property) Source (River or sea) Performance' = risk mitigation (largely) Page 15

16 Damage to Properties (Res. + Commercial) ( Million) Expected Annual Damage Upper Bound = 119,971,588 Best Estimate = 102,483,258 Lower Bound = 85,209,508 Present day Barriers not working Expected annual damages By Flood cell Return Period (years) Upper Bound Best Estimate Low er Bound By Flood Area Page 16

17 The system model attributing risk to individual levees Contribution to risk due to overtopping Defence Unique identifier Rank Total Contribution Breach Contribution Overtop Contribution Contribution to risk due to breaching , ,041 23, , , , , , , , , , , , , , , ,060 3,932 98, ,961 95,964 2, ,216 45,124 34, , , , , ,511 50,524 23, ,386 73, ,857 67, ,973 63, , , , , ,090 32,023 30,066 Page 17

18 Project Closure The TE2100 journey TE2100 Consultation Plan TE2100 Final Plan PAR 1 PAR 2-4 ECOs HLOs Jan 2002 Jun 2003 Nov 2004 Jan 2010 Phase 0 Phase 1 Phase 2 Phase 3 Phase 4 Exploring the problem Project Scoping Understanding the Estuary Policy and Options Investigation and Appraisal Plan Finalisation, and approval Page 18

19 TE 2100 Policy Options 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 over time). P3 Continue with existing or alternative actions to manage and maintain flood risk at the current level (accepting that the likelihood and/or consequences of a flood will increase over time from this baseline). P4 Take further action to sustain current scale of flood risk into the future (responding to potential increases in flood risk from urban development, land use change, and climate change). P5 Take further action to reduce the risk of flooding (now and/or in the future). Page 19

20 Damage (Million ) Risk now and under future climate scenarios Present day and Year 2100, Return period/economic damage results 30,000 25,000 Year 2100, P1 Policy- Medium high EAD= 2.1 billion 20,000 15,000 10,000 Present Day P3 Policy EAD= 3 million 5,000 0 Return Period (Years) Page 20

21 Understanding the Estuary at a Local Level Chiswick City Barking Grays Canvey Island Hadleigh Putney Deptford Bexley High Halstow All Hallows Twickenham Gravesend Three phases of local studies and public meetings to find out what local communities think about their part of the Thames Estuary Page 21

22 Improve existing defences Flood Storage Page 22 New barrier Barrier with locks Hundreds of local FRM activities investigated and major changes to the asset system refined down to four, with two front runners

23 Max water level rise: 0m Defra UKCIP MH TE2100 H+ 1m 2m 3m HLO 1 TE2100 H++ 4m Improve Thames Barrier and raise d/s defences Existing system Over-rotate Thames Barrier and restore interim defences Flood storage, improve Thames Barrier, raise u/s & d/s defences HLO 2 Raise Defences Flood storage, restore interim defences Flood storage, over rotate Thames Barrier, raise u/s & d/s defences Latest climate change results for TE2100 H++ HLO 3a New barrier, retain Thames Barrier, raise defences New barrier, raise defences HLO 3b HLO 4 New barrage The final plan is a combination of approaches Page 23

24 98 TE2100 Actions.. Plan Over 8 Action zones.. and zone 0 covering the whole estuary Page 24 delivered through multi agency working

25 Likely Cost Profile The first 25 years Continuing investment and planning together 1.5 bn. The middle 15 years from 2035 to 2049 Renewal and reshaping the riverside 1.8 bn. To the end of the century from 2070 moving towards the 22 nd century 6bn to 7bn. Page 25

26 The detail.. The first 25 years 1.15bn the Assets 59m inter-tidal habitat creation 302m -- 3 rd party costs (FPM) The middle 15 years 1.65bn the Assets 29m inter tidal habitat creation 139m 3 rd party costs (FPM) To the end of the century 4.75.bn the Assets (new barrier?) 50m inter tidal habitat creation 1.2bn 3rd party costs (FPM) 1.5 bn. 1.8 bn. 6bn to 7bn. Page 26

27 TE2100 the first 25 Years Continue to maintain the current flood defence system including planned improvements Working with regional and local planning authorities to improve floodplain management Safeguard areas that may be required for future changes to flood managements Commencing work to create new habitats Monitor/Review the use of Thames Barrier for fluvial floods in West London Page 27

28 TE2100 the next 35 years and from 2070, moving into the 22nd century!!!! Replacing and upgrading defences upstream and downstream of Thames Barrier Continue working with regional and local planning authorities on riverside improvements Take informed decision on building a new barrier at Long Reach or other end of the century option Remaining habitat creation sites Construct new barrier or adapt Thames Barrier ~ 2070!!! Page 28

29 3 phases of stakeholder engagement March 2009: launch TE2100 plan consultation April/May 09: targeting key stakeholders/future implementation partners June to Aug 09: public awareness and engagement Final revision of Plan TE2100 plan public consultation Page 29

30 Conclusions TE2100 provides an overarching FRM strategy for the Thames Estuary for the next 100 years to adapt to changes including SLR New methods and science have been used Methods and lessons learnt potentially have wider application beyond TE2100 but time and resource provided would not be available to all FRM strategies Page 30

31 Developing SLR adaptation strategy for the Thames Estuary (TE2100) Questions?

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34 Early conceptual options Page 34

35 Indicator value (e.g. sea level rise) Thresholds, lead times and decision points Threshold value of indicator when intervention is needed Decision point based on best estimate Predicted values of indicator based on rate of change Recorded values of indicator Date of review Lead time for planning and construction Time Page 35

36 Indicator value (e.g. sea level rise) Thresholds, lead times and decision points Threshold value of indicator when intervention is needed Decision point based on best estimate Decision point taking account of uncertainty Band of uncertainty Predicted values of indicator based on rate of change Recorded values of indicator Date of review Lead time for planning and construction Time Page 36

37 2100 Annual number of closures of the Thames Barrier Threshold 3 Raise upriver defences Raise upriver defences New barrage or convert Thames Barrier to barrage (depends on Mean Sea Level rise) No. of closures with no interventions Threshold 2 Threshold 1 (70 closures per year) Note: The portfolios of responses are designed to keep the annual number of closures below 70. Thus the actual number of closures follows the dotted brown lines. Page 37 Time Impact of Mean Sea Level increase on defences upriver of the Thames Barrier