Dr Becky Briant, Department of Geography, Environment and Development Studies’ Birkbeck, University of London Programme Director: MSc Climate Change Management ( MSc Environment and Sustainability (

How has climate been changing? What is the evidence that it is due to humans? What are the projections for south-east England? The Thames and climate Mitigation vs adaptation Risk and adaptation in the Thames Drier summers Wetter winters - surface water flooding Sea level rise - tidal flooding

How has climate been changing? Surface temperature data from FAQ3.1, IPCC AR4 WG1 (2007)

Average summer temperatures in London Figure 1.2: London Draft Climate Change Adaptation Strategy adaptation

What is the evidence that it is due to humans? Global surface temperature for FAQ3.1, IPCC AR4 WG1 (2007) Carbon dioxide (ppm) and Methane (ppb), Figure 6.4, IPCC AR4 WG1 (2007)

How might climate change in the future? Regional trends Figure TS.28, using medium (A1B) emissions scenario from IPCC 4AR WG1 (2007)

What are the projections for south- east England? Summer mean temperature, medium emissions scenario, 50% probability 2020s2050s 2080s Degrees centigrade increase

What are the projections for south- east England? Summer precipitation, medium emissions scenario, 50% probability 2020s2050s 2080s Percentage change

What are the projections for south- east England? Winter mean temperature, medium emissions scenario, 50% probability 2020s2050s2080s Degrees centigrade increase

What are the projections for south- east England? Winter precipitation, medium emissions scenario, 50% probability 2020s 2050s 2080s Percentage change

A little hydrology… UN Environment Programme Technical Publication - Rainwater Harvesting And Utilisation An Environmentally Sound Approach for Sustainable Urban Water Management: An Introductory Guide for Decision-Makers :

Tides on the Thames The Thames at Teddington Weir Low tide in central London High tide in central London

Mitigate – reduce the worst impacts on the atmosphere Adapt – to change that will almost certainly happen - ‘a response to climate change that seeks to reduce the vulnerability of natural and human systems to climate change effects’

Mitigation Reduce greenhouse gas production by individuals, businesses, organisations and Government Reducing energy demand – e.g. better building design Switching to low-carbon energy sources UK Climate Change Act 2008 Ambitious targets – reduction of 80% compared to 1990 levels by 2050 Mandatory carbon accounting Five yearly national carbon budgets Investment in low-carbon technologies

Drier summers Wetter winters Surface water flooding – LCCAS ‘HIGH’ risk River flooding – LCCAS ‘MEDIUM’ risk Sea level rise Tidal flooding – LCCAS ‘LOW’ risk

Drier summers – water quantity Table 1 from: 2008 Thames Water Revised Draft Water Resources Management Plan (2013 draft plan from WRZ = Water Resource Zone; SWOX = Swindon and Oxfordshire; SWA = Slough, Wycombe and Aylesbury.

Drier summers – water quality C L E A N R A I N EVAPORATIONEVAPORATION ABSTRACTIONABSTRACTION DIRTYRUNOFFDIRTYRUNOFF CLEAN RAINCLEAN RAIN EVAPORATIONEVAPORATION ABSTRACTIONABSTRACTION DIRTYRUNOFFDIRTYRUNOFF

Adapting to drier summers Decreasing our water usage – rainwater harvesting

Wetter winters Flows at Teddington Weir : Typical summer's day – c. 3,000 million litres of fresh water Typical winter's day c. 4 x greater, sometimes c. 8 x (winter 1947 peak flow c. 20 x > than typical summer's day) ‘Future peak freshwater flows for the Thames, at Kingston for instance, could increase by around 40% by 2080.’ Thames Estuary 2100 Plan Consultation Document ( agency.gov.uk/homeandleisure/floods/ aspx). Urban areas particularly vulnerable to ‘surface water flooding’ because of fast delivery from storm water drains.

Areas at risk from surface water flooding in a 1 in 200 year rainfall event (Figure 3.4, London Climate Change Adaptation Strategy)

Why is London vulnerable to surface water flooding? Large amount of impermeable surfaces (roofs, pavements, roads) Clay-rich soils (also impermeable) Multiple owners / managers of systems Poor maintenance Increased risk because: Inappropriate drainage systems for future rainfall type Increased development Population growth

What can be done? Technologies: Green roofs Permeable hardstanding Planning / governance 2007 onwards – Drain London Forum (set up by GLA) Sustainable Drainage policy for new developments Planning permission required for non-permeable hardstanding > 5 m 2 Targetted maintenance relating to weather warnings Emergency planning

Sea level rise Global sea level rise: Figure 1, FAQ5.1, IPCC AR4 WG1 (2007) Thames sea level rise due to climate change estimated at between 20 and 90 cm by 2100 (TE2100 Plan)

Data taken from the UKCP09 website and plotted using Excel

Why is the Thames vulnerable to tidal flooding? Regional subsidence causing sea level rise Storm surge events raise sea level by up to 4 m, especially if: Coinciding with a high spring tide Coinciding with floodwater from upstream Climate change: Sea level rise m by 2100 (TE2100 state likely range m) Increased peak flows at Kingston by c. 40% by 2080

Storm surges (TE2100 Plan)

Storm surges Surge tide event at the Thames Barrier

1953 storm surge Figures 3 and 7, Risk Management Solutions (2003) Floods Retrospective. Available from: spective.pdf [ Accessed 20th November 2012] spective.pdf

Thames Barrier closures Thames Barrier closures 1982/83 to 2008/09 (Figure 3.2, London Climate Change Adaptation Strategy) Now: 1 in 2000 year event (0.05%) 2030: 1 in 1000 (0.1%) 2100: 1 in 100 (1%)

TE2100 Conclusions First 60 years ( ; ): Option 1.4 – Improve the existing defences (optimise defence repair and replacement) Criteria: increase protection on a small scale because sea level rises and storm surge increases modest, whilst minimising environmental and economic impact associated with larger structures Last 30 years ( ): Options 1.4 and 3.2 (New barrier at Long Reach) Criteria: reassess strategy based on actual sea level rise and new projections, try to avoid barrier for as long as possible because of ecosystem impacts and poor water quality due to impoundment