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.
8What are the projections for south-east England?
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:
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.
9What are the projections for south-east England?
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:
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.
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
33
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.
34
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