The 2013/14 winter floods in the UK were caused by a series of powerful storms between December 2013 and February 2014 that led to widespread flooding. The heavy rainfall saturated the ground and overwhelmed drainage systems, causing river, coastal, and pluvial flooding. Majorly affected areas included the Somerset Levels and Thames Valley. The flooding had significant economic, social, and political impacts and highlighted the need to improve flood prevention and management in the UK.

1. 1
Flooding in the British Isles: An
Evaluation of Approaches to Flood
Protection and Mitigation
Henry Dawson
AQA extended project qualification

2. 2
Contents
1 Introduction .............................................................................................................................. 3
2 Types of flooding....................................................................................................................... 3
2.1 Coastal flooding.................................................................................................................. 3
2.1.1 Storm surges................................................................................................................. 3
2.1.2 Tsunamis...................................................................................................................... 4
2.2 Inland flooding.................................................................................................................... 5
2.2.1 Pluvial flooding............................................................................................................. 5
2.2.2 River (Fluvial) flooding...................................................................................................5
2.2.3 Groundwater flooding...................................................................................................6
3 Recent Flood Eventsin the UK ....................................................................................................6
3.1 2007 Summer Floods...........................................................................................................6
3.2 2013/14 Winter Floods........................................................................................................7
3.2.1 Causes.......................................................................................................................... 7
3.2.2 Economic Impacts.........................................................................................................8
3.2.3 Social impacts............................................................................................................... 9
3.2.4 Political impacts............................................................................................................ 9
4 Future..................................................................................................................................... 11
4.1 Why floodimpactswill increase......................................................................................... 11
4.1.1Climate changes........................................................................................................... 12
4.1.2 Urbanisation and population growth............................................................................ 13
4.2 What can we do to defend ourselves?................................................................................ 13
4.2.1 Engineeringflood control ............................................................................................ 14
4.2.2 Dredging..................................................................................................................... 15
4.2.3 Natural Flood Management Techniques....................................................................... 16
4.2.4 Planning policy............................................................................................................ 17
4.3 Evaluation of approaches to Flood Management................................................................. 17
5 Recommendations................................................................................................................... 18
5.1 General Recommendations................................................................................................ 18
5.2 Approaches to Flood Prevention in Study Areas .................................................................. 19
5.2.1 Somerset.................................................................................................................... 19
5.2.2 Thames Basin.............................................................................................................. 20
Summary of References Used...................................................................................................... 21

3. 3
1 Introduction
Floodinghasbeenaproblemforresidentsof the BritishIslessince the Romanera1
andcontinuesto
be a problemintothe 21st
century, with5 millionpropertiesandsignificantportionsof the nation’s
infrastructure underthreat2
.20th
centurytechnological advancesinmappingandflooddefences
have meantwarningandmitigationhasimprovedrapidly,leadingtoareductionindeathsand
greaterinformationonfloodingpatterns. However, the frequencyandmagnitude of floodingis
increasingdue toglobal temperature changes3
andcombinedwithincreasinglevelsof economic
propertyat riskof damage, thishasledto concernswhetherwe mustdomore to protectourselves
againstthisdevastatinghazard4
.
A floodoccurswhenwateroverflowsorinundateslandthat'snormallydry5
.Itthreatensalmostall
of the global humanpopulation,withanywhere whichrainfallsunderthreat.Howeverthisisnotthe
only cause of flooding,withshorttermthreatssuchas breacheddamsor rapidice meltingcausing
inlandfloodingof floodplains. Coastal floodingisalsoa majorissue,especiallyinthe BritishIsles-
due to the islandgeography.Thisoccurswhen hightidesand/orstormsbreachcoastal defences,
inundatinglowlyingand the heavilypopulatedcoastlinewithwater.
ThroughthisprojectI hope to describe the typesof floodingand ascertain theirvaryingpotential to
cause damage or lossof life withinthe BritishIsles.Withthe evergrowingconcernof the effects
anthropogenicglobal warmingwillhave,Iwill tryandpinpointsome of the possible futureimpacts
includingthe economiceffectsandpolitical consequences. Iwill examine variousapproachesto
floodpreventionandmitigationandseektomake policyrecommendations. My mainareasof focus
will be onthe floodingonthe Somersetlevelsand inthe ThamesValley duringthe winterof
2013/14, but thispaperwill alsoreferencefloodimpactselsewhere inthe UK.
2 Types of flooding6
2.1 Coastal flooding
Coastal floodingoccursintwo mainways:
2.1.1 Stormsurges
These are the mainformof coastal flooding7
.Theseare mainlycausedbyhighwindspushingwater
towardscoasts.This causesthe waterto ‘pile up’causinglarge wavesof up to 8m insome cases8
.
Thisrise in sealevelsisoftenassistedbylow pressuresinthe centre of the stormcausingwater
1 Roman and Medieval Sea and River Flood defences: English Heritage: 2011
2 Geographies of UK flooding2013/14: Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
3 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
4 Geographies of UK flooding2013/14: Conclusion:Colin Thorne:Geographical Journal:2014
5 National Geographic:Floods:Jim Richardson
6 Floodingin England- National assessmentof flood risk:1.1: Environment agency: 2008
7 Waikato Region Council:Coastal Flooding:
8 HurricaneKatrina approachingNew Orleans in 2007

4. 4
levelstorise upbyup to 1cm per1millibarchange inpressure9
.Howeverthese surgesare oftenonly
able to cause floodingwhencombinedwithahightide,overwhelmingflooddefences asseenin
Figure 1.
Figure 1: Storms and HighTides10
The most devastatingexample of thistooccur in the BritishIsleswasthe East Coastfloodof 1953. A
combinationof winds,gustingupto126mph, and extreme low pressure of 964mb, comparedto an
average of 1012mb11
ledtoa stormsurge of 5.6m above meansea level12
. 32000 people were
evacuatedoverthe course of thisdisasterwith330 dyingacrossthe westcoastof Englandand
Scotland and1800 losingtheirlivesinthe low lyingNetherlands13
.The economiccostswere also
large withthe equivalent(intoday’smoney) of 1.2billionpoundsworthof damage includingthe loss
of 160000 acres of floodedlandunusable foryearsandinfrastructure putoutof actionsuch as
powerstations,roadwaysandrailways14
.
2.1.2 Tsunamis
Tsunamisare giantwavescreatedby displacementsof
water.Thiscan be causedby earthquakesora large
bodyof material enteringthe water,suchasfollowing
a volcaniceruptionorlarge landslide (Figure 2).Whilst
indeepoceansthe wavesmayonlyrise up a few
incheshoweverastheyreachshallowerwaterthe
amplitude increasesanddragdecreasesthe velocity
and they can become wallsof waterseveral meters
high.OnBoxingDay 2004 one of the deadliest
tsunamiswascreatedbya 9.0 magnitude earthquake
beneaththe IndianOcean.Travellingat500kph15
and
9 Met Office:Storm Surge: 2014
10 Met Office:Storm Surge: 2014
11 National Oceanography Centre: Storm Surges and Coastal Flooding
12 Met Office:1953 Eastcoastflood- 60 years on: 2014
13 Met Office:1953 Eastcoastflood- 60 years on: 2014
14 Met Office:1953 Eastcoastflood- 60 years on: 2014
15 Paul Watson,Barbara Demick and Richard Fausset,Los Angeles Times, January 2, 2005
Figure 2: How a tsunami occurs

5. 5
up to 30m inheight,it affected12countries,takingmore than238000 lives, leavingmore than1.7
millionhomeless andcausingmore than$10 billionindamage16
.Althoughtheseeventscanbe
extremelydeadly,asprovenabove,itishighlyunlikelyforanymajorthreatto the BritishIsles.Thisis
due to the lack of subductive tectonicactivitywithinthe surroundingareas.Withthe nearest
subductionzone beingwithinthe Caribbean,modellinghassuggesteditwouldtake over5hoursfor
any wave toreach Britishshoresandwouldonlybe of 1 or 2 metersinheight;lowerthanmost
storm surgesinthe regionandunderthe capacity of many flooddefences17
.Thiscantherefore be
dismissedasamajor cause of coastal floodinginthe UK. 18
2.2 Inland flooding
2.2.1 Pluvial flooding
Althoughnotas well-knownassome othertypesof flooding, pluvial eventscanoccurwithout
warningandin areasnot prone to flooding. Eventsoccuraftershort,intense downpours,abovethe
capacityof drainage systemsorgroundinfiltration19
.Thisisoften aggravatedbythe reliance of local
authoritiesonVictorianeradrainage systems whichhave deteriorated due toinsufficient
maintenance20
orare of unsuitable designforcurrentdaydemands.Victorian-eradrainsoften
combine sewage anddrainage21
andasa consequence whendrainsover-flow sewage isbroughtto
the surface, increasingthe publichealthriskandenvironmentaldamage.
2.2.2 River(Fluvial)flooding
Riverfloodingnormallyoccurswhenthe rivercannotcope withthe volume of waterdrainingintoit
fromthe surroundingland ordrainage basin22
.Thiscanthenleadto overtoppingof the river,
inundatingthe areasadjacenttothe riverchannel known asthe floodplain,mainlyalongthe lower
reachesof the river.Thisis a natural processthat onlybecomesa riskto human life andproperty
whenthe floodplainhas beensubjecttodevelopment23
. Developmentcanalsoincrease the
magnitude of floods byincreasingsurface waterrunoff therefore increasingthe flowandspeedof
the waterenteringariverchannel24
.Thiscan be done throughdeforestation,decreasing
interceptionandtranspirationfeedback,orurbanisation-where pavingmeansnowaterisabsorbed
intothe groundleadingtomore enteringthe riverata giventime25
.The overpavingof greenspaces
has increasedrecentlywithmanyhouseholdspavingovergardenstocreate drivewayswith“Anarea
16 Phillip Allen Updates conference: Tectonic Hazards
17 British Geological survey:Could a Tsunami hit the British Isles:Brian Baptie
18 Physorg: Unique Japan tsunami footage boon to scientists:16th March 2011
19 Pluvial (rain related) floodingin urban areas- the invisiblehazard:Houston et al:JRF Foundation: 2011
20 Geographies of UK flooding2013/14:Urban Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
21 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
22 Environment Agency: Risk of floodingfrom rivers and seas
23 The British Geographer: Floods and River Management
24 The British Geographer: Floods and River Management: Human Causes of floods
25 The British Geographer: Floods and River Management: Human Causes of floods

6. 6
of vegetatedgardenequivalentto21 timesthe size of Hyde park was lostbetween1998 and 2006”
inLondonalone26
.
2.2.3 Groundwaterflooding
Groundwaterfloodingoccurswhenwaterlevelsinthe groundrisesabove the surface.Itusually
occurs inareas underlain byaquifersinpermeable rocks.These canbe regional andextensive,
aquifers,suchaschalkor sandstone,ormaybe more local sandand rivergravels underlainbyless
permeable rocks27
.
3 Recent Flood Events in the UK
3.1 2007 Summer Floods
The summerof 2007 sawrainfall of suchhighmagnitude it’ssurpassedanyMay-Julyrainfall since
1879 by over100mm28
(Figure 3).Thiswas due to a seriesof deepAtlanticdepressionsthatpassed
overthe BritishIsles. Forsome areasof Herefordinlate June (20th
) the 16hour rainfall total reached
134.88mm. This magnitude of stormshada probabilityof 0.1% of occurringina givenyear29
.This
causedwidespread floodingresultinginatotal
economiccostof £3.2billion30
andover55000 homes
and businesses affected31
.Areasthatwere
significantlyaffectedbythe Floodsincludedthe Rivers
Severn,ThamesandHumber. Howeverthiscannot
coverthe total impactsdue to the fact the impact on
people’slivesandlivelihoods,whichmaytake much
longertorecover, cannotbe expressedinmonetary
values32
.The impactof thisfloodingwasthe subjectof
the 2008 Pittreport that made 92 recommendations
as to how the UK couldmanage floodsinthe future33
.
These recommendations formthe basisforthe 2008
NAFRA paperbythe EnvironmentAgency34
.
Figure 3: Distribution of rainfall, June35
26 Guardian:London- where the streets are paved with gold, and the gardens with cement: John Vidal:8th June
2011
27 Floodingin England- National assessmentof flood risk:1.1: Environment agency: 2008
28 The summer 2007 floods in England & Wales- a hydrological appraisal:Marsh & Hannaford:Centre for
Ecology and Hydrology: 2007
29 The summer 2007 floods in England & Wales- a hydrological appraisal:Marsh & Hannaford:Centre for
Ecology and Hydrology: 2007
30 The costs of the summer 2007 floods in England:Chatterton et al:Environment Agency: 2010
31 BBC news: Floodingfacts and figures:6th December 2007
32 The costs of the summer 2007 floods in England:Chatterton et al:Environment Agency: 2010
33 2007 floods review: CabinetOffice: 2008
34 Floodingin England- National assessmentof flood risk:1.1: Environment agency: 2008
35 Met Office:Heavy rainfall/flooding- June2007

7. 7
3.2 2013/14 Winter Floods
A seriesof persistentwinterstormsand
heavyrainfall culminatinginthe wettest
Januarysince 176636
(Figure 4),when
recordsbegan,ledto significantflooding
across the BritishIslesincludingthe
SomersetLevelsandThamesValleywhere
the majorityof mediafocuswasdirected.
These floodswere well documentedwith
the EnvironmentAgencyissuing155 severe
floodwarnings37
.
Fig 4: Distribution of Rainfall Jan 2014 38
3.2.1 Causes
The firstmajor stormto hit the British
occurredbetween the 5-6th
December2013.
Thiswas an extreme eventcausingflooding
across Scotlandanda stormsurge that
batteredthe East coast,exceedingthe
heightof the 1953 storm surge inmany areas39
.Thisledto the highestevertides recorded inthe
Humberand Thames estuaries40
.Anotherstormonthe 18th
to 19th
of Decemberfollowedcausing
more floodingacrossNorthernIrelandandWestScotland41
.Thiswasthenfollowedbyasignificant
clusterof stormsacross Christmasthat generatedwidespreadfloodingacrosssouthernEnglish
countiesincludingDorsetandSurrey42
.Due tothiscontinuedrainfall the groundwasalready
saturatedwithdrainage systemsoverwhelmedby the time more stormsmade landfallonNew
Year’sEve.When these stormscontinuedintothe New Yearmanyriverside townsalongthe Severn
and Thamessufferedwide scale flooding43
.Additionallythe magnitude of these stormscoincided
withthe highspringtide renewingcoastal floodingacrossmuchof the westcoastof the Isles.
Althoughthe stormsreducedinquantityandmagnitude,until the endof January,rainfallcontinued
to put drainage systemsunderpressure withthe wettestJanuarysince 177644
(Figure 4).When
another6 stormsstruck at 2-3 day intervalsinearlyFebruaryitrenewedthe surface waterflooding
across manyareas and alsoincreasingthe floodedareaonthe Somersetlevelswith100cubic
36 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
37 Winter Floods 2013-14:House of Commons:2014
38 BBC news: 10 Key moments of the UK winter storms:17th February 2014
39 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
40 Geographies of UK flooding2013/14: Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
41 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
42 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
43 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
44 BBC news: January rainfall breaks records in parts of England:30 January 2014

8. 8
metresof pondedwater45
(Figure 5).Thisrainalsocausedanotheroutbreakof riverflood across
much of the Severnandthe Thamesto a greaterextentthanthe occurrence earlierinthe year46
.
For manythoughthe endof the storms didnotsignal the endof theirtroublesasthe persistent
heavyrainhad causedwatertablestorise to the highestlevelsin179 yearsinsome locations47
-
Chilgrove House Well,locatedonthe UpperChalkoutcropsof the SouthDowns48
- causinglong
durationgroundwaterfloodingintoMay201449
. There was alsolarge numberof sinkholesthat
appeared,includingone thatappearedwithinthe central reservation of the M2 motorway inKent50
,
whichcouldbe attributedtohighgroundwater tablesandthe level of watersaturation51
.
Althoughindividuallythesestormsandfloodingevents cannotbe ‘regardedasexceptional’of
magnitude asother
past events52
;the
close frequency and
the coincidentnature
of these events
causedwide spread
impactsoversuch a
continuedperiodof
time that meantthat
these floodshada
disproportionate
social,political and
economicimpact.
Figure 5: Flooding Somerset Levels53
3.2.2 EconomicImpacts
A popularfigure forthe average annual losses fromfloodingfloatedbythe mediais£1 billion54
whichPenning-Rowsell claims55
are linkedtoanoverestimation of floodlossesinthe National
Assessmentof FloodRisk56
.Penning-Rowsell believesthe annual averagelossdue tofloodingsince
45 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
46 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
47 British Geological Survey:Groundwater floodingin the UK- February 2014: 2014
48 Encyclopaedia of Hydrology and water resources: Herschy, Reginald W., Fairbridge,Rhodes W.: 1998
49 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
50 BBC news: 15ft-deep hole appears on M2 in Kent: 11th February 2014
51 Geographies of UK flooding2013/14:Physical Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
52 The recent storms and floods in the UK: Slingo et al: Met Office, Centre for Ecology and Hydrology: 2014
53 Guardian:Floodwaters recede but lifestill on hold for villagers of Somerset Levels: 16th March 2014
54 Guardian:UK flood clean-up costcould hit £1 billion,insuranceexperts warn: Hilary Osborne:20th February
2014
55 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
56 Floodingin England- National assessmentof flood risk:Environment agency: 2008

9. 9
1990 is£250 million(adjustedforinflation) andthatthe winterof 2013/14 was not exceptional in
comparison aslosses tothe nationare expectedtoreach£290 million57
.Thiscanbe linkedtothe
small numberof homes(7800) and businesses (3200) affected58
comparedto55000 in 200759
. In
part thisimpactcan be attributedtothe successof engineeringmethodsof floodprotectionsuchas
the installationof demountable floodbarriersatkeylocationsonthe RiverSevern60
.
3.2.3 Social impacts
Withmany arguingthat the blame lieswiththose whochoose tolive andworkinthese areasof risk,
there isincreasingpressure ondevelopers,insurersandlocal authoritiestoreduce the level of
developmentonfloodplains;areasthatare naturallydesignedtoflood61
. Howeveritshouldbe
notedthat developmentonfloodplainsisslowing62
andthatit inalmost100% of casesthe advice of
the EnvironmentAgencyondevelopmentinthese areasisfollowed63
.However,itcouldbe noted
that thisslowdown indevelopmentmaybe merelyareflectionof nationwide propertydevelopment
trendsfollowingthe recession64
.
Whilstmanyunderstandthe physical healthimplicationsof floodinglessunderstandthe mental
healthissuesthatmayoccur followingaprolongedandintense periodof floodingsuchas2013/14.
Penning-Rowsell arguesthatwhile the physical impacts,suchasrespiratoryproblemsfromthe
damp,reduce exponentiallytoalmostnone 2yearsafterthe floods;mental healthissuecontinueon
for muchlonger65
.Theyare hard to understandandtreat andare oftennotthe issue at the forefront
of peoplesmindandtherefore notmuchisdone tocombat the issue inthe aftermathof a flood.
3.2.4 Political impacts
Thorne believesthat the managementof floodriskanddevelopmentlargelydependonpublic
opinion66
andthis isagreed,inprinciple byBall andGreen.Theybelievethatwidespreadflooding,
such as 2013/14, can leadto publicoutcrytowardseitherpoliticians, fuellinganincrease inspending
on defences,ortowardspeople whochoose tolive or workinareas subjecttofloodrisk claiming
theyshouldlearntolive withit67
or be preparedtomove.Thisoccurred quite neatlypostthe
2013/4 floodswithone groupblamingthose whowere victimof the flooding,whoshouldof known
that theywere livingormovingintoahighriskarea, andanotherblamingthe EnvironmentAgency
57 The 2013/14 floods:what do they tell us about the overall flood risk in England and Wales:Edmund Penning-
Rowsell:2014
58 Geographies of UK flooding2013/14:Social Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
59 See ‘3 2007- A comparison’
60 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
61 Geographies of UK flooding2013/14:Social Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
62 Geographies of UK flooding2013/14:Social Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
63 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
64 Housingand economic linkages:4.2 The international impactof the recession on housing: Kamm and
Chivunga:Chartered Institute of Housing:2010
65 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
66 Geographies of UK flooding2013/14:Political Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
67 Future floodingand coastal erosion risks:Human behaviour:(section by) Ball and Green: Thomas Telford
London: 2014

10. 10
and government68
.WithNational newspapersoftencomingoutinsupportof those floodedwith
headlinessuchas “EA bosses…refuse £1.7 milliondredgingof keySomersetriversthatcouldhave
stoppedflooding”69
politicianshave appearedtoreactinfavourof savingface rather than
addressingmajorlongtermproblems. DavidCameron,the Prime Minister,criticisedhisownCabinet
Ministerincharge of Environment,foodandrural affairs:OwenPattersonandthe chairof the
EnvironmentAgency,LordSmithfordiscontinuingdredginginthe late 1990s70
.
“From the late 1990s – far too long – the Environment Agency believed
that it was wrong to dredge. Those of us with rural constituencies
affected by flooding have seen the effectiveness of some dredging.”71
David Cameron
“Now if it is good for some places, we need to make the argument that it
would be good for many more places. I have said that we are going to
see dredging on the [rivers] Tone and the Parrett in the Somerset Levels
because that would make a difference. But I believe it is time for Natural
England, the Environment Agency and the departments to sit round the
table and work out a new approach that will make sure that something
that did work, frankly, for centuries is reintroduced.”72 David Cameron
Thisledto Cameronpledgingtostartdredgingbefore the 1st
of April as longas the groundwas able
to supportthe weightof machinery (started29th
March 2014)73
.
68 Geographies of UK flooding2013/14:Political Geography of the Winter floods:Colin Thorne: Geographical
Journal:2014
69 Daily Mail:EA bosses spent£2.4 million on PR… refuse £1.7 million dredgingof key Somerset rivers that
could have stopped flooding: 10 February 2014
70 Geographies of UK flooding2013/14:Pointingthe finger- floodingand river management: Colin Thorne:
Geographical Journal:2014
71 Independent: David Cameron overrules Environment Secretary Owen Paterson to order urgent dredging in
Somerset to combat the flooding:Tom Bawden: 5th February 2014
72 Independent: David Cameron overrules Environment Secretary Owen Paterson to order urgent dredging in
Somerset to combat the flooding:Tom Bawden: 5th February 2014
73 BBC news: Somerset floods- River dredging begins on Parrett and Tone: 31st March 2014

11. 11
4 Future
744.1 Why flood impacts will increase
Figure 6 summarisesthe whythe riskandlikelihoodof floodingmayincrease inthe future. More
detailedanalysishighlightsavarietyof potential causes.
74 Floodingin England- National assessmentof flood risk:1.1: Environment agency: 2008
Figure 6: Aspects of Flood Risk

12. 12
4.1.1Climatechanges
While notan immediate threatclimatechange hasthe potential togreatlyincreasethe frequency
and occurrence of floodinginthe BritishIslesthroughrisingsealevelsandincreasedrainfall75
.Sea
levelshave beenrising‘atarate greaterthanthe meanrate of the past twomillennia’since the mid-
19th
century76
.Rising0.19m (+/- 0.02m) between1901 and 201077
. Increasingglobal temperatures
are projectedtocontinue thisrate of rise to a height above currentlevelsbetween0.52 to 0.98m by
210078
for RCP8.5 (Representative ConcentrationPathway)79
. RCP8.5is the highestemission
predictionwithCO2emissionsmodelledtorise fourfold80
.Whilstsealevelsare risingglobally,locally
the impactsmay vary. Inthe UK thisis largelydue toisostacticrebound,a post-glacial phenomena
causedby the disappearance of the glacial ice cover. Duringandsubsequenttothe ice melt,ashas
occurredin NorthWestScotlandsince the lastice age 12000 yearsago81
,the landhas experienced
upliftandtherefore relativelylowersealevels. Reboundhasbeendifferential acrossthe BritishIsles
withevidence of relative subsidence inthe
southernUK causinglocal sealevel increases. 82
There has beenanotable rise inperiodsof
heavyrainfall fallingonthe BritishIslesinthe
past half century83
;the frequencyof heavy
rainfall hasbeenfluctuatingbetween1-in-75
daysand 1-in-100 days since 2000. In
comparisonthe 5 year runningmeanbetween
1970 and 1980 didnot break1-in-100 daysand
fluctuatedtoas lowas 1-in-125 days84
. These
changescouldbe downto many natural factors.
Seasurface temperatureshave increasedby
0.85°C85
and itis “extremelylikelythatmore
than half the observedglobal averagesurface
temperature rise from1951 to 2010 was
causedby anthropogenic86
increasein
greenhouse gasconcentrations87
.Ithasbeen
suggested thatrainfall increasesinrelationto
temperature couldexceedthe simple
75 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
76 IPCC AR5 SMP: B4: 2014
77 IPCC AR5 SMP: B4: 2014
78 IPCC AR5 SMP: E6: 2014
79 World Meteorological Organization:Emission Scenarios
80 RCP8.5-A scenario of comparatively high greenhouse gas emissions :Keywan, Riahi,et al:2011
81 Science Museum: PastClimate- Iceages
82 The firstglobal warmingrefugees: Wilson:2002
83 Met Office:Statistics for December and 2012- is the UK getting wetter: 2013
84 The recent storms and floods in the UK: Has climatechange been a contributingfactor?: Met Office, Centre
for Ecology and Hydrology: 2014
85 IPCC AR5 SMP:B1: 2014
86 Adj. “caused by humans”
87 IPCC AR5 SMP:D3: 2014
Figure 7: Isostatic Rebound in the UK

13. 13
thermodynamicClausius-Clapeyronrelationship(6-7% increase per1°C)88
. These changesinsea
surface temperature andthe spatial patternswithinoceansleadtospatial differencesin
precipitationlevels89
;yetmore researchisneededtofullydeterminethe completeimpactof these
changes90
.
Withglobal temperature andsea levelssettorise,alongsidethe magnitudeandfrequencyof hydro-
metrological hazardsforhighlatitude NorthAtlantic91
,floodingcouldbecome evermore significant
inshapingBritonslives.Thismeansthe wayswe canmanage floodsare becomingevermore
importantinthe political spectrum92
andtocommunitiesof all scales.
4.1.2 Urbanisationandpopulationgrowth
Withthe 82% of the UnitedKingdom’spopulationlivinginurbanareas,upfrom 79% in 2000, there
isa growingconcernoverthe numberof people affectedbyfloods93
.Continuingdevelopmenton
floodplains,due tothe historical locationof manyurbanareas,has contributedtothe rapidlyrising
economiccostsof flood
eventsinthe UK94
. Heavily
urbanisedareascanalso
increase the magnitude of
floodsaspermeable areas
are replacedby
impermeable paving,
acceleratingrunoff (Figure
8) 95
.
4.2 What can we do
to defend ourselves?
Whilstflooddefencesare
neededtheymustbe well
plannedandassessedto
ensure theycanbe
sustainable andcost
effective.The riskaftera
majoreventsuchas the
winter2013/14 isthat many
88 The recent storms and floods in the UK: Has climatechange been a contributingfactor?: Met Office, Centre
for Ecology and Hydrology: 2014
89 The recent storms and floods in the UK: Has climatechange been a contributingfactor?: Met Office, Centre
for Ecology and Hydrology: 2014
90 Global WarmingPattern Forming: Sea Surface Temperature and Rainfall:Xieet al:University of Hawaii at
Manoa, National Center for Atmospheric research,Geophysical Fluid DynamicsLaboratory:2009
91 Trends and low frequency variability of extra-tropical cycloneactivity in the
ensemble of twentieth century reanalysis: Wanget al:2012
92 See ‘3.2.4 Political Impacts’
93 World Bank: Urban population:2014
94 The summer 2007 floods in England & Wales- a hydrological appraisal:Flood risk and vulnerability:Marsh &
Hannaford:Centre for Ecology and Hydrology: 2007
95 Effects of Urban development on floods:Konrad:USGS:2014
Figure 8: Impact of Development on Runoff

14. 14
of the decisionsmade posteventcanbe reactive ratherthan proactive inensuringfuture riskis
minimised96
.Anexample of thiswouldbe DavidCameron’sdecisiontooverrulethe Environment
Agencyandrestart dredgingalongthe riversTone andParretton the Somersetlevels97
.
4.2.1 Engineeringfloodcontrol
Flooddefencesandembankments
Floodwallsandembankmentsofferasimilarbuthave different requirements.Floodwallsare
effectively awall builttoprotectareasat risk fromflooding(Figure9).Whilstthisistheirprimary
aimtheycan alsobe usedto improve the aestheticappearance of the area,suchas the Perthflood
alleviationscheme98
.Thisissimilarlythe case withembankments;howeverthese are moundsof
natural material raisedtothe designcrestlevel andcanrequire amuch largerfootprintthana
floodwall99
.Anotherpossibilityisthe deploymentof temporaryanddemountable defenceswhen
and where theyare needed100
101
Figure 9: Flood Walls and Embankments
96 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
97 See ‘3.3.4 Political Impacts’
98 Flood walls and flood embankments: 9.2: Rickard:2009
99 Flood walls and flood embankments: 9.4: Rickard:2009
100 Flood walls and flood embankments: 9.1: Rickard:2009
101 Flood walls and flood embankments: 9.3: Rickard:2009

15. 15
Coastal barriers
Britainhas one of the largestmoveable floodbarriersinthe worldspanning540macross the mouth
of the RiverThames102
(Figure 10).Itclosesto protectLondonfromcoastal stormsurgesbut also
fromfluvial floodingfurtherupstream103
.In2014 itwas operatedarecord numberof times,48,
beatingthe previousrecordof 19 (2003) by some margin104
.
105
Figure 10: Thames Barrier
4.2.2 Dredging
Dredgingisa controversial issue withconflictcomingbetweenmanyfluvialanalystsandlocals. Itis
the processof removingsedimentfromthe riverchannel,eitherfromthe bedorthe sides,to
increase the conveyance capacityof the riverchannel106
. Byincreasingthe conveyance capacity the
aimis to increase the bankfull discharge whichinturn shouldnotonlyreduce the amountof
overbankfloodingbutalsoincrease the rate at whichanyfloodwatersare dispersed (Figure 11).
107
Figure 11: How Dredging Works
102 GOV.UK: Thames Barrier:2014
103 GOV.UK: Thames Barrier:2014
104 GOV.UK: Thames Barrier:2014
105 Telegraph:Thames floods- Thames Barrier closed for record 19th consecutivetide: 16th February 2014
106 Floods and Dredging- a reality check:2.1: Chartered Institution of Water and Environmental Management:
2014
107 BBC news: How do you stop flooding: 29th January 2014

16. 16
4.2.3 Natural FloodManagementTechniques
Natural floodmanagement maybe promotedby (Figure 12):
 Storingwater:Thiscan be done bymaintainingthe capacityof ponds,ditchesandreservoirs
or creatingnewstorage areas108
.Water meadowsare an example of this.Theyare areasof
landdeliberatelyallowedtofloodthenentrappedsothatwateristakenaway fromswollen
rivers109
 Slowingwater:This isachievedbyincreasingits resistance toflow;examples includecontour
plantingof treeseitheronriverbanksorthe widerfloodplain110
.
 Reducingflowconnectivity: Interruptingsurface flowsof watercanbe integratedintoeither
optionabove. Waterstorage areas or bufferstripsof grassand/ortreescan take awaya
pathwayof flow111
 Sustainable UrbanDrainage systems(SUDS):These lookatbothpastand future
infrastructure.Thorne describesthe needtoreplace the Victoriandrainage systemwhere
sewage anddrainage iscontainedinone channel whichcannot cope withthe currentand
future demandsplaceduponitinheavyrainfall events112
.Anotheroptionistouse
permeable paving113
andincrease greenareasthatallow infiltrationandtranspirationto
reduce runoff tomorphthe urbanhydrological cycle tobecome more like the natural
cycle114
.
Figure 12: Flood Mitigation Techniques
108 Natural Flood management: Houses of Parliament:2011
109 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
110 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
111 Natural Flood management: Houses of Parliament:2011
112 Geographies of UK flooding2013/14:Urban geography of the winter floods:Colin Thorne: Geographical
Journal:2014
113 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
114 Geographies of UK flooding2013/14:Conclusion:Colin Thorne: Geographical Journal:2014

17. 17
4.2.4 Planningpolicy
Planningpolicycanplaya significantrole inreducingthe future impactsof floodsbyrestricting
developmentinhighriskareas. The EnvironmentAgency adviseslocal authoritiesonriskof flooding
and makesrecommendationsonplanningpermissionthrough NAFRA115
thisincludedalarge scale
mappingof floodriskareasfor use byplanners,developers,insurersandthe general publicto
increase awareness.Inalmostall knowncasesthisadvice hasbeenfollowed;howeverthe majority
of casesthere isnot the informationonwhetherthe advice hasbeentakenornot116
.Thorne argues
that Flood-Re,areinsurance fundtoprotectinsurersfromwidespreadlossesafterfloodevents117
,
couldassistinslowingdevelopmentonfloodplainsasithasthe potential toprovide coverfor
existingpropertiesyetcoulddiscourage new,inappropriatedevelopments118
.
4.3 Evaluation of approaches to Flood Management
Whilstthere were some dramaticpicturesof housesinundatedwithwaterfollowingthe 2013/14
floodsthe realitywasthatthe impacts,giventhe magnitude of the total event,wasverylimited119
.
Worldclass flooddefencessuchasthe ThamesBarrierand the lessonslearntfrompastevents,such
as such 2007, ledto 3 millionpropertiesbeingprotected;a significantincrease onthe 100,000 in
2007120
. Anexample of aneffectiveandcosteffectiveapproachhasbeenthe use of demountable
floodbarrierinurbanareas alongthe SevernValley(Figure 13).Howeverthe ThamesBarrierhas
beenclosedarecord numberof timesin2014121
andis argueditmay be time for a replacement to
continue toprotectthe£200 billionworthof assetssittingonthe banksof the Thames122
.
123
Figure 13: Demountable Flood Barrier, Worcestershire
115 See ‘3.2.2 Economic Impacts’
116 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
117 Flood-Re explained:Association of British Insurers:2014
118 Geographies of UK flooding2013/14:Social geography of the winter floods:Colin Thorne: Geographical
Journal:2014
119 Geographies of UK flooding2013/14:Physical geography of the winter floods:Colin Thorne: Geographical
Journal:2014
120 Winter Floods 2013-14:House of Commons:2014
121 See ‘4.3.1 Engineering flood defences’
122 The Telegraph: The Thames Barrier has saved London- but is ittime for TB2: 18th February 2014
123 Local Government Association:Floods and erosion risk management: 2013

18. 18
Howeverwhilstincreasedprotectionisnotoftenseenasabad thing,there are some potential
pitfalls.Penning-Rowsell arguesthatasprotectionincreasesthe senseof safetyincreasesinparallel
leadingtomore developmentandtherefore more propertyatrisk.Thiscan setoff longterm cycle
where more developmentleadstothe needforbetterdefencesandvice versa124
.
While SUDSand uplandcatchmentmanagementhave proventobe effectiveatsmall scalestheywill
not significantlyreducethe impactsof a highmagnitude,longscale eventsuchasthe 2013/14
floods125
.Wide spreaduse mayhave the potential toreduce impacts butthishasyetto be proven.
Dredgingwill onlyhave alimitedeffectonconveyance of the channel unlessthe wholelengthis
dredged.Eventhen anymajorfloodwill have apeakflow manytimesgreaterthanthe bankfull
discharge andthenwill overtopthe sidesfloodingthe surroundingfloodplain126
.Itisanextremely
expensive operation,costing£6millionforthe 8kmstretch of the Tone andParrett127
; andmust be
repeatedasmaterial fromupstreamwill re-accumulateoverspanof 5-10 years128
,whichhas been
citedas the reasonit wasceasedinthe firstplace129
.Dredgingintidal riverareaswill have little- to
no positive impactasthe waterlevel isdeterminedbythe global sealevel.Itwill alsoincrease the
ease of whichtidal flowsandsedimentscanflow upthe river;thishas a potential toincrease the risk
fromstorm surges130
.
Anotherpotential impactof dredgingisanincrease inconveyance withoutincreasingcapacity.This
will increase flowvelocityandtherefore heightenthe floodriskdownstream aspeakflowsare not
slowedupstreamdue tocanalisation131
5 Recommendations
5.1 General Recommendations
Withtrendsshowinganincreasingfrequencyandmagnitude of future stormevents,investmentinto
flooddefencesandmitigationmustbe continuedinthe contextof anincreasingpopulationand
pressure of developmentforhousing. Howeversignificantadditional investmentinto flooddefences
isunfortunatelyveryunlikely.Thisisbecause of the opportunitycostof movingfundsfrommore
immediatelyobviousfundingareassuchas schoolsor the NHS whichmayleadto publicdisproval in
a time whenpoliticianswilldoanythingtowinvotes. Thishasledtocuts for fundingforLLFA’sbya
thirdfor 2015/16132
and an overall fall inflooddefence spendingby10% since the previous
government,excludingemergencydisasterrelief,leavingmore than half the UKsflooddefences
124 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
125 RGS Lecture Autumn 2014: Floodingin the UK- myths and realities:Edmund Penning-Rowsell
126 Floods and Dredging- a reality check:2.1: Chartered Institution of Water and Environmental Management:
2014
127 Waste and wastewater treatment: EA completes dredging of the Somerset Levels rivers:3rd November 2014
128 Floods and Dredging- a reality check:2.1:Chartered Institution of Water and Environmental Management:
2014
129 Geographies of UK flooding2013/14:Pointingthe finger: Colin Thorne: Geographical Journal:2014
130 Geographies of UK flooding2013/14:Pointingthe finger: Colin Thorne: Geographical Journal:2014
131 Floods and Dredging- a reality check:2.4:Chartered Institution of Water and Environmental Management:
2014
132 Guardian:Local Authority flood defence fundingcut by a third next year: 19th November 2014

19. 19
withminimal maintenance133
.These cutsoccurin the face of evidenceof the significantcostbenefit
of investinginflood andcoastal erosionriskmanagementhasacost benefitaveragingbetterthan1
to 8134
.
On a large scale, forthe magnitude of stormswe face inthe BritishIsles,hardengineering
techniquesare the mostlikelytosucceedinthe longterm:Examplesincludethe Thamesand
HumberBarriers.Howeverthismaynotbe the mostsuitable inall partsof the countryand it
requiressignificantresearchtounderstandwhatmethodswill give the bestvalueintimeswhere
governmentcutsare continuing.Thisisbecause the social impactof anyfloodingmustbe takeninto
account alongside the more obviouseconomiccosts.
To bestprotectthe BritishIslesfromsignificantlossesinfuture yearsanintegrated,proactive
response isneeded. Thisnotonlyinvolvescentral andlocal governmentsbutalsothe private sector
and the communityatrisk.There needstobe a longterm, ring-fencedfundingforfloodanderosion
riskmanagement.Thisprotectionfromchange in administrations wouldallow the smoothestand
mostefficientrunningof the longtermcontinuous projectsthatare requiredtoprotect the British
Isles.The response anddecisiononhowbesttoprotectareas mustbe influencedbybothtop-down
and bottom-upapproaches.Advice must be soughtfromleadingexpert organisations suchas The
EnvironmentAgency andthe FloodHazardResearchCentre atMiddlesex University.Alsoitis
importantforresidentsto be consultedandinformedof plans.The governmentandprivate sector
alsohave a responsibilitytochange the social mind-setof developmentonfloodplains.Firmssuch
as Flood-Re have the abilitytomake clearto developersof the riskandaddedcostof developing
these at-riskareas.Whilstengineeringadvancescandoso much to protectthe homesand
businesses’there isalimitation.Tofullyattempttominimisefloodriskswe mustchallenge the
social mind-set.We mustremove the thinkingthat‘thiswon’thappentome’.We musteducate the
population sotheycanmake theirownfullyinformeddecisionsonwhethertotake that significant
riskin developingandlivinginthese areas. Inthisonusmustfall onthe governmenttoprovide this
education of notonlythose currentlylivinginhighriskareasbutthe entire population.
5.2 Approaches to Flood Prevention in
Study Areas
Differentapproachesshouldbe adoptedinthe two
areas:
5.2.1 Somerset
The Somersetlevels (Figure14) have a low value in
termsof economicloss withasparse population.The
compensationhandedouttofarmersforagricultural
lossesonlyreachedthe 10s of millions135
and
therefore tocompletelymitigate thislow lyingarea
wouldbe an inefficientuse of money andresources.
Thisis a prime example of whereuplandcatchment
133 Guardian:Risks of floods in England up due to cuts in Government funding,say NAO: 5th November 2014
134 UK climatechangerisk assessment-government report: HM Government: 2012
135 What do the 2013/14 floods tell us about overall flood risk in England and Wales?:Penning-Rowsell:2014
Figure 14: Somerset Levels

20. 20
managementmaybe a more effective method.Whilstitmaynotalleviate floodinginthese areasit
may helptoslowsurface runoff thereforereducingthe pressure onflooddefencesfurther
downstreaminpopulationareassuchas Bridgwater. Anotherpossible solutionthathasbeen
suggestedisatidal barrierat the mouthof the RiverParrettas recommendedinthe Bridgwater
StrategicFloodDefence Infrastructure Planningalthoughthiswouldnotbe neededuntilatleast
2030136
. This barrierwouldoperate ona similarbasistothe Thames barrierand be usedto resist
hightidesandstorm surgesfromtravellingupstream.
5.2.2 ThamesBasin
The Thamesis an area that justifiesthe use of hardengineeringdefences. The significantlyhigher
population(5th
of the UKs population137
) andeconomicvalue lyingwithinthe Thamescatchment
area reliesonit.Whilstthe ThamesBarriercurrentlydoesanoutstandingjobprotectingLondon’s
residentsfromstormsurgesandhightidesthere isa needtoreplace itsoonerratherthan lateras
sealevelsrise.Furtherupstreaminthe Runnymede,WaltonandTeddington areas,where the
majorityof affectedpropertieswerein2013/14, it wouldbe beneficial to re-engineerweirs to
improve capacity andcreate floodchannelstodivertwaterawayfrompopulatedareas (Figure
15)138
. Howeverthese areasalsorequire anintegratedresponse withincreasedplanningcontrols on
floodplain development, the use of sustainable urban drainage furtherupstream,widerspreaduse
of permeable
pavingto slow
surface run off
and the creation
of floodbasins
that would
attenuate flood
peaksbystoring
wateron the
floodplain.
Figure 15: Lower
Thames Flood
Management
Proposals
136 Bridgwater Strategic Flood Defence InfrastructurePlanning- Final Report:Environment Agency, Sedgemoor
DistrictCouncil:2009
137 The river Thames Initiative- why monitor river catchment: Centre for Ecology and Hydrology
138 Lower Thames Flood Risk Management Strategy: Environment Agency: 2010

21. 21
Summary ofReferences Used
These are referencedinfull asFootnotestothe text.
LECTURE:Flooding- myths and realities:Edmund Penning-Rowsell
LECTURE: Presentation of the IPCC 5th installment: Dr David Adger
LECTURE: Tectonic Hazards:Stewart et al:Phillip Allen Updates
WEB: Met Office
WEB: Guardian
WEB: Daily Mail
WEB: Independent
WEB: BBC news
WEB: National Geogrphic
WEB: Waikato region council
WEB: National Oceanography Center
WEB: Los Angeles Time
WEB: British Geological Survey
WEB: World Meteorological Organization
WEB: Science Museum
WEB: World Bank
WEB: GOV.UK
WEB: Telegraph
WEB: Water and Wastewater treatment
PAPER: IPCC Ar5: Summary for Policy-Makers:2014
PAPER:Geographies of UK flooding2013/14:Colin Thorne: Geographical Journal:2014
PAPER: Future floodingand coastal erosion risks:Thorneet al:2014
PAPER: Global WarmingPattern Forming: Xieet al:University of Hawaii atManoa, National Center for
Atmospheric research,Geophysical Fluid DynamicsLaboratory:2009
PAPER: A global perspectiveon storms and floods in the UK: Slingo et al:Met Office: 2014
PAPER: National assessmentof flood risk:Environment Agency: 2009
PAPER: Housingand economic linkages:Kamm and Chivunga: Chartered Institute of Housing: 2010
PAPER: Floodingin England- National assessmentof flood risk: Environment Agency: 2008
PAPER: RCP8.5-A scenario of comparatively high greenhouse gas emissions :Keywan, Riahi,et al:2011
PAPER: The firstglobal warmingrefugees: Wilson:2002
PAPER: The recent storms and floods in the UK: Met Office, Centre for Ecology and Hydrology: 2014
PAPER: Trends and low frequency variability of extra-tropical cycloneactivity in the ensemble of twentieth
century reanalysis:Wanget al:2012

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PAPER: The summer 2007 floods in England & Wales- a hydrological appraisal:Flood risk and vulnerability:
Marsh & Hannaford:Centre for Ecology and Hydrology: 2007
PAPER: Effects of Urban development on floods: Konrad:USGS:2014
PAPER: Flood walls and flood embankments: Rickard:2009
PAPER: Floods and Dredging- a reality check: Chartered Institution of Water and Environmental Management:
2014
PAPER: Natural Flood management: Houses of Parliament: 2011
PAPER: Flood-Re explained:Association of British Insurers:2014
PAPER: Winter Floods 2013-14:House of Commons:2014
PAPER: Local Government Association:Floods and erosion risk management: 2013
PAPER: UK climatechange risk assessment-government report: HM Government: 2012
PAPER: What do the 2013/14 floods tell us aboutoverall flood risk in England and Wales?:Penning-Rowsell:
2014
PAPER: Bridgwater Strategic Flood Defence InfrastructurePlanning- Final Report: Environment Agency,
Sedgemoor DistrictCouncil:2009
PAPER: The river Thames Initiative- why monitor river catchment: Centre for Ecology and Hydrology
PAPER: Lower Thames Flood Risk Management Strategy: Environment Agency: 2010.
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