dr becky briant, department of geography, environment and development studies’ birkbeck,...

Climate Change and the River Thames

Climate Change and the River ThamesDr Becky Briant,Department of Geography, Environment and Development Studies Birkbeck, University of London

Programme Director:MSc Climate Change Management (http://www.bbk.ac.uk/study/2013/postgraduate/programmes/TMSCLIMC_C)MSc Environment and Sustainability (http://www.bbk.ac.uk/study/2013/postgraduate/programmes/TMSENSUS_C)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 climateMitigation vs adaptationRisk and adaptation in the ThamesDrier summersWetter winters - surface water floodingSea level rise - tidal floodingHow has climate been changing?Surface temperature data from 1979-2005FAQ3.1, IPCC AR4 WG1 (2007)

Figure here with a map showing changes from 1970-2000.

Global average increase of 0.74 deg C since 1850, but not experienced the same in different parts of the world3Average summer temperatures in London 1950-2006Figure 1.2: London Draft Climate Change Adaptation Strategy http://www.london.gov.uk/priorities/environment/consultations/climate-change-adaptation

4What is the evidence that it is due to humans?Global surface temperature for 1850-2006FAQ3.1, IPCC AR4 WG1 (2007)

Carbon dioxide (ppm) and Methane (ppb), Figure 6.4, IPCC AR4 WG1 (2007)Dont want to get bogged down here in my MSc this section takes 3 lectures and we still only scratch the surface. However, key points are: Broadly coincident trends in CO2 (also other GHGs) and temperature (have figures)Plausible mechanism for linking themChemical fingerprinting of CO2 in the atmosphere links it to fossil fuel burning

Globally averaged Earth surface temperature (combined land and sea HadCRUT3) for 1850-2006 relative to the 1961-1990 mean - Houghton (2009) Figure 4.1a based on FAQ3.1, Figure 1 of IPCC AR4 WG1 (2007)

5How might climate change in the future? Regional trendsFigure TS.28, using medium (A1B) emissions scenario from IPCC 4AR WG1 (2007)

Hard to estimate exactly, both because of uncertainties in how the climate system works and because of uncertainties in how much we will emit

Scenarios to see how much climate might change if we emitted different amounts of GHG

Global forecasts range from 1 deg C to 6 deg C by 2100 if you include the full errors on each estimate. (cf. 0.75 deg C rise since 1850)

Often people plan for somewhere in the middle of that range but recent emissions have been near the high end of the range, so that may be optimistic.

Anyway, global means are not so useful, so this is a mid-range projection of how temperatures might rise in different parts of the world by the last decade of the century.6What are the projections for south-east England?

http://ukclimateprojections.defra.gov.uk/

Summer mean temperature,medium emissions scenario, 50% probability2020s2050s2080sDegrees centigrade increaseN.B. Only projections uncertainties in how much we will emit, of which types of GHG and where; as well as uncertainties in climate modelling. However:

UK Climate Projections 2009 project gives some ideas of how climate may change in the UK in the next 40 years

Table 1.1 (LCCAS) UK Climate Projections 2009 for London (2050s medium emissions scenario)Rising temperaturesSummers will be warmer, with the average summer day12 being 2.7C warmer and very hot days6.5C warmer than the baseline average. By the end of the century the hottest day of the yearcould be 10C hotter than the hottest day today.Winters will be warmer, with the average winter day being 2.2C warmer and a very warm winterday 3.5C above the baseline.More seasonal rainfallSummers will be drier, with the average summer 19 per cent drier and the driest summer39 per cent drier than the baseline average.Winters will be wetter, with the average winter 14 per cent wetter and the wettest winter33 per cent wetter than the baseline average.Tidal surgesTidal surges (see Chapter 3 for description) are not projected to increase in frequency, though theheight of a one-in-fifty-year tidal surge is projected to increase by up to 70cms by the end of thecentury.Sea level riseSea levels are projected to rise by up to 90cms by the end of the century. An extreme projectionof a 2-metre increase has been generated using the latest ice-sheet modelling published after theIPCC (Intergovernmental Panel on Climate Change) Fourth Assessment report.

7What are the projections for south-east England?

http://ukclimateprojections.defra.gov.uk/Summer precipitation,medium emissions scenario, 50% probability2020s2050s2080s

Percentage changeN.B. Only projections uncertainties in how much we will emit, of which types of GHG and where; as well as uncertainties in climate modelling. However:

UK Climate Projections 2009 project gives some ideas of how climate may change in the UK in the next 40 yearsTable 1.1 (LCCAS) UK Climate Projections 2009 for London (2050s medium emissions scenario)Rising temperaturesSummers will be warmer, with the average summer day12 being 2.7C warmer and very hot days6.5C warmer than the baseline average. By the end of the century the hottest day of the yearcould be 10C hotter than the hottest day today.Winters will be warmer, with the average winter day being 2.2C warmer and a very warm winterday 3.5C above the baseline.More seasonal rainfallSummers will be drier, with the average summer 19 per cent drier and the driest summer39 per cent drier than the baseline average.Winters will be wetter, with the average winter 14 per cent wetter and the wettest winter33 per cent wetter than the baseline average.


http://ukclimateprojections.defra.gov.uk/Winter mean temperature,medium emissions scenario, 50% probability2020s2050s2080s

Degrees centigrade increaseN.B. Only projections uncertainties in how much we will emit, of which types of GHG and where; as well as uncertainties in climate modelling. However:



http://ukclimateprojections.defra.gov.uk/Winter precipitation,medium emissions scenario, 50% probability2020s2050s2080sPercentage change

N.B. Only projections uncertainties in how much we will emit, of which types of GHG and where; as well as uncertainties in climate modelling. However:


10The Thames and climateA little hydrology

UN Environment Programme Technical Publication - Rainwater Harvesting And UtilisationAn Environmentally Sound Approach for Sustainable Urban Water Management: An Introductory Guide for Decision-Makers: http://www.unep.or.jp/Ietc/Publications/Urban/UrbanEnv-2/4.aspTides rise and fall by 7 m / day (TE2100, Environment Agency)InputsOutputsTo understand the impacts of a changing climate on the River Thames, we need to understand how temperature and precipitation translate into the workings of a river system. So, this diagram explains the main inputs and outputs to the hydrological system of a river.

Inputs:Rainfall straight to river across various types of land some pollutedRainfall to river through groundwater some more pollutionRainfall very fast to river through sewers in urban areas some pollution

Outputs:Evaporation from river, also from land higher as temperatures riseAbstraction for use by public

Both these will be affected by drier summer and wetter winters

Tidal inputs (extra level of complexity) water rises and falls by 7 m a day, meets freshwater at Teddington Weir (TE2100, 2009)

Will be affected by sea level rise12

Tides on the ThamesThe Thames at Teddington WeirLow tide in central LondonHigh tide in central London

Mitigation vs adaptationMitigate reduce the worst impacts on the atmosphereAdapt 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

MitigationReduce greenhouse gas production by individuals, businesses, organisations and GovernmentReducing energy demand e.g. better building designSwitching to low-carbon energy sourcesUK Climate Change Act 2008Ambitious targets reduction of 80% compared to 1990 levels by 2050Mandatory carbon accountingFive yearly national carbon budgetsInvestment in low-carbon technologiesDefinition of mitigationAct on CO2 advert16Risk and adaptation in the ThamesDrier summersWetter wintersSurface water flooding LCCAS HIGH riskRiver flooding LCCAS MEDIUM riskSea level riseTidal flooding LCCAS LOW riskDrier summers water quantityTable 1 from: 2008 Thames Water Revised Draft Water Resources Management Plan (2013 draft plan from http://www.thameswater.co.uk/about-us/5373.htm). WRZ = Water Resource Zone; SWOX = Swindon and Oxfordshire; SWA = Slough, Wycombe and Aylesbury.

Some statistics about water use in London and scarcity of the resource Table from Thames Water SWOX = Swindon and Oxfordshire SWA = Slough, Wycombe and AylesburyDrier summers threaten an already scarce resource

18Drier summers water qualityCLEAN RAINEVAPORATIONABSTRACTIONDIRTY

RUNOFFCLEAN RAINEVAPORATIONABSTRACTIONDIRTY

RUNOFFExplain how drier summers lead to lower water quality19Adapting to drier summersDecreasing our water usage rainwater harvesting

20Wetter wintersFlows 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 (http://www.environment-agency.gov.uk/homeandleisure/floods/125045.aspx).Urban areas particularly vulnerable to surface water flooding because of fast delivery from storm water drains.Flood risk

Teddington Weir is where the Thames becomes tidal - typical summer's day c. 3,000 m ltrs fresh water pass over it. Typical winter's day at least four times greater, sometimes eight times. Winter 1947, peak flow at Teddington c. 61,698 m ltrs a day, c. three times > typical winter's day, > 20 times typical summer's day.TE2100 potential for increases in peak flows in, e.g. Kingston by 40% by 2080s

Exacerbated by stormwater drainage

21Areas at risk from surface water flooding in a 1 in 200 year rainfall event (Figure 3.4, London Climate Change Adaptation Strategy)

Surface water flood risk is poorly understood and the highest risk for London22Why is London vulnerable to surface water flooding?Large amount of impermeable surfaces (roofs, pavements, roads)Clay-rich soils (also impermeable)Multiple owners / managers of systemsPoor maintenanceIncreased risk because:Inappropriate drainage systems for future rainfall typeIncreased developmentPopulation growthAll from LCCAS

Risk will increase because:Most drainage systems designed for high frequency, low volume rainfall (which is less likely under future CC low frequency, high volume rainfall is projected)Many drains and gullies poorly maintained, so not even providing moderate levels of serviceProjected increase in winter rainfall and heavy rainfall eventsPermeability low because of increased development23What can be done?Technologies:Green roofsPermeable hardstandingPlanning / governance2007 onwards Drain London Forum (set up by GLA)Sustainable Drainage policy for new developmentsPlanning permission required for non-permeable hardstanding > 5 m2Targetted maintenance relating to weather warningsEmergency planning

Drain London Forum has DEFRA funding to undertake strategic analysis of flood risk in London, prioritise high risk flood areas and develop a framework for collaborative action.

Planning permission but recent changes to permitted development re extensions could make roof areas greater anyway, so may offset gains relating to hardstanding.24Sea level rise tidal floodingSea level riseGlobal 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)Climate change causes sea levels to rise due tothermal expansion of the oceans (warmer water takes up more space)Melting of glaciers and polar ice

N.B. South-east England already sinking 1.5 mm / year due to natural processes, which will give a 13 cm sea level rise by 2100 even without climate change

Range of tides probably stays the same, but if overall sea level is higher, higher tides will also be higherTE2100 estimates between 20 cm and 90 cm climate change induced sea level rise by 2100Already 1.5 mm / year natural sinking of the land adds c. 13 cm26

Data taken from the UKCP09 website and plotted using ExcelWhy is the Thames vulnerable to tidal flooding?Regional subsidence causing sea level riseStorm surge events raise sea level by up to 4 m, especially if:Coinciding with a high spring tideCoinciding with floodwater from upstreamClimate change:Sea level rise 0.2 - 2 m by 2100 (TE2100 state likely range 0.2-0.9 m)Increased peak flows at Kingston by c. 40% by 2080Thames Estuary esp vulnerable to flooding. SE Britain tilting downwards and SL rising. High tide in central London rising c. 75cm per century. Also - when an area of low pressure - perhaps hundreds of miles across - moves eastwards across the Atlantic towards the British Isles, it raises the level of seawater beneath it by up to a third of a metre. If this 'plateau' of sea water passes north of Scotland and then down into the shallow basin of the North Sea, perhaps further heightened by strong winds from the north, it can cause excessively high surge tides in the Thames Estuary of up tofour metres leading towards London. When a surge tide also coincides with a spring tide (which occur twice monthly), flooding would be a serious possibility.E.g. Sat 31 Jan 1953 to 1 Feb 1953. High spring tide and storm plus tidal surge meant water level locally exceeded 5.6 metres above mean SL.

TE2100: SL rise in Thames over the next century due to thermal expansion of the oceans, melting glaciers and polar ice likely to be betw 20cm & 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. 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 2080.

28Storm surges(TE2100 Plan)

Storm surgesSurge tide event at the Thames Barrier

Pretty bad with a lowish one but can be fatal 1953 - Over 600 square kilometers (150,000 acres) of land were flooded and 307 lives lost in the U.K., while in the Netherlands over 1,800 people were drowned.301953 storm surge

Figures 3 and 7, Risk Management Solutions (2003). 1953 Floods Retrospective. Available from: www.rms.com/publications/1953_Floods_Retrospective.pdf [ Accessed 20th November 2012]

UK - Canvey Island, Essex, completely inundated, 58 deaths

N.B. similar event Jan 1978, but better evacuation so no deaths and fewer casualties. Also better sea defences all raised by 2 m.

Netherlands had defences, but in poor state of repair.31

How are we protected at present?

Flood barriers at the present day (LCCAS) integrated system comprising the Thames Barrier, 185 miles of floodwalls, 35 major gates and over 400 minor gates.

These photos = key ones downstream of the Thames Barrier at Woolwich.

32Thames Barrier closuresThames 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%)LCCAS

Barrier doesnt just protect against storm surges (tidal flooding closures shown here)

Fluvial flooding closures keep out the tide when river levels are running very high anyway, so that they dont get even higher when the tide comes in. Protects West London.

N.B. each closure of the Thames Barrier also results in the closure of the other gates and barriers along the Thames (integrated system)

Barrier currently provides protection for a 1 in 2000 year return tidal period event (explain return period)

Without upgrading, this will fall to 1 in 1000 (0.1%) by 2030 and 1 in 100 (1%) by the end of the century

Number of times Thames Barrier can be closed effectively and safely = c. 70 times per year. As SL rises, more tidal closures, less fluvial closures possible, so increased flood risk in West London. Need to plan for this.

Also increasing urban areas downstream of the Thames Barrier TE2100 project to assess risks and options

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Showing 1-3 only because 4 not really considered because of predictions that reckon storm surges wont get relatively worse by the end of the century so you dont need a full on barrier with locks.

So: These results give greater certainty that we have been planning for the right potential range of water levels this century, and the current Defra guidance for sea level rise in the Estuary is appropriate. Our previous worst-case scenario for increases in maximum water levels can be revised down from +4.2 m to +2.7 m. This worst-case scenariois highly unlikely, but gives us an extreme to test our options against. Such a reduction in worst case scenario for this century means that a tide-excluding estuary barrage will not be necessary to manage flood risk this century and can be dropped from our final options. We are confident that our plan can cope with a changing climate and we can measure with confidence how much adaptation will be needed for different climate change scenarios.

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TE2100 ConclusionsFirst 60 years (2010-2025; 2025-2070):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 structuresLast 30 years (2070-2100):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

dr becky briant, department of geography, environment and development studies’ birkbeck,...

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