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How can communities be better prepared for floods?

Jan 16, 2016

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“Floods - Past and Present Issues” Address given to The Royal Scottish Society of Arts 11th February 2002 Edinburgh by Professor George Fleming FREng FRSE FICE FASCE. - PowerPoint PPT Presentation

  • Floods - Past and Present Issues

    Address given to The Royal Scottish Society of Arts11th February 2002Edinburgh

    by

    Professor George Fleming FREng FRSE FICE FASCEProfessor of Civil Engineering, University of Strathclyde Managing Director of EnviroCentre Chairman, ICE Presidential Commission Undertaking a Technical Review of Flooding in England and Wales

  • How can communities be better prepared for floods?Why is it not yet a requirement of the Building regulations that the lowest floor of a building on a flood plain is above the 1 in 100 year flood level?Should all buildings on flood plains be constructed of flood resistant materials?Why is there no national strategy for such mitigation systems?Could a national flood insurance programme be linked with these requirements?

  • -V-

  • INTRODUCTION

  • England and Wales - 2000River Tay - 1993River Ness - 1989The Clyde - 1977Bristol - 1968 Lynmouth - 1952Medway - 1814

  • Risk Expenditure CycleRisk Expenditure Cycle

  • Depute Prime Minister John Prescott MP described the severe weather and flooding that dramatically disrupted parts of the country in Autumn 2000 as a wake-up call to the impacts of climate change.

  • THE HISTORICAL CONTEXT

  • A flood is a great flow of water, causing overflow and inundation (Chambers, 2000(2)). The factors causing a flood to occur are extremes in meteorology and hydrology, coupled with changes to river hydraulics caused by land use and alterations to river geomorphology

  • The Forth & Clyde and Union Canal

  • Development in Flood Plains

  • HISTORICAL FLOOD ESTIMATION

  • Historical Data Collection

  • Risk of a one in 100 year flood eventOnly possible once in 100 yearsOne in 100 chance of flooding

    X

  • Regional Flood Frequency Curve: Scotland (Biswas & Fleming, 1966)Regional Flood Frequency Curve: Great Britain (NERC, 1975)Regional Flood Frequency Curves

  • Regional Flood Frequency Curve: Scotland (Biswas & Fleming, 1966)Regional Flood Frequency Curve: GB(NERC, 1975)1.02.03.04.05.0123456780-1Ty12510255001001000xxxxxxxxAnalysis of Flood Frequency Curves

  • Flood Estimation Techniques

  • THE CURRENT PROBLEM

  • economiccommercial disruptionservices disruptionflood typedepth of floodingflood velocityrate of flood risewave actionflood predictionsource of floodingreliability of forecastingwarning timesocialflood awarenessresilience of populationnature of housingsocial disruptionflood protectiontype of defencedcbackground conditionsnumber of properties at riskenvironmentalclimate change environmentally sensitive areaslong and short term impacts economicinfrastructure at riskpotential agricultural lossesflood typeflood predictionsocialflood protectiondesign standardcondition of defencebackground conditionsenvironmentalflood riskflood riskFactors Affecting Flood Riskflood history

  • Effect of Constraining Flood Plains

  • Effect of Constraining the Flood Plain

  • Leigh Barrier in Operation

  • Flood Defences at Gainsborough

  • FUTURE FLOODING ISSUES

  • Projected Effects of Climate Change on Run-Off for Clyde Catchment

    Flood chance in any year

    (return period)

    5

    10

    20

    30

    50

    70

    100

    200

    500

    Year 2000 runoff

    (m3/s)

    678

    798

    931

    1005

    1114

    1191

    1254

    1411

    1680

    Predicted 2050s runoff

    (m3/S)

    Design event rainfall +10%

    750

    884

    1033

    1116

    1239

    1324

    1396

    1572

    1875

    Increase in runoff (%)

    9.6

    9.7

    9.9

    9.9

    10.0

    10.1

    10.1

    10.2

    10.4

  • Presidential Commission to Review Flooding in England and WalesInstitution of Civil Engineers One Great George StWestminsterLondon, SW1P 3AA

    Tel: 0207 665 2232www.icenet.org.uk/presidential.html

  • CONCLUSIONS

  • How can communities be better prepared for floods? A: For flood risk to be more clearly explained to both professional and lay person.Why is it not yet a requirement of the Building regulations that the lowest floor of a building on a flood plain is above the 1 in 100 year flood level? A: Building on the flood plain needs to be carefully assessed. There is more to do than a simple building regulation.Should all buildings on flood plains be constructed of flood resistant materials? A: Existing buildings need flood proofing. New buildings on flood plains need to have flood resistance designed in as well as flood impact designed out.Why is there no national strategy for such mitigation systems? A: There is an emerging strategy in England and Wales to manage flood risk. A similar strategy has to be developed in Scotland which takes us beyond just flood warning.Could a national flood insurance programme be linked with these requirements? A: Flood insurance programme must be consumer-driven and be flexible. A national flood insurance programme would be as complicated as it was ineffective.

  • Warning systems will be important, but a flood management system must be introduced in order that community and profession can work together and learn to live with our rivers.