“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 Professor 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?

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INTRODUCTION

England and Wales River Tay River Ness The Clyde Bristol Lynmouth Medway

Risk–Expenditure Cycle No flood Complacency Reduced expenditure Increasing risk Major flood Damage, distress, disruption, deaths Review Expenditure Reduced risk Risk–Expenditure Cycle No flood Complacency Reduced expenditure Increasing risk Major flood Damage, distress, disruption, deaths Review Expenditure Reduced riskNo flood Complacency Reduced expenditure Increasing risk Major flood Damage, distress, disruption, deaths Review Expenditure Reduced risk

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

floodplain early towns & settlements normally on local elevated areas or where the channel abuts higher ground on edge of floodplain floodplain later extensions to town on natural floodplain in part of the natural flood channel of the river Development in Flood Plains

HISTORICAL FLOOD ESTIMATION

Historical Data Collection

“Risk of a one in 100 year flood event” Only possible once in 100 years One 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) T y1y x x x x x x x Q / Q x Analysis of Flood Frequency Curves

Flood Estimation Techniques

THE CURRENT PROBLEM

economic commercial disruption services disruption flood type depth of flooding flood velocity rate of flood rise wave action flood prediction source of flooding reliability of forecasting warning time social flood awareness resilience of population nature of housing social disruption flood protection type of defence d c background conditions number of properties at risk environmental climate change environmentally sensitive areas long and short term impacts flood risk economic infrastructure at risk potential agricultural losses flood type flood prediction social flood protection design standard condition of defence background conditions environmental flood risk Factors Affecting Flood Risk flood 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

Presidential Commission to Review Flooding in England and Wales Institution of Civil Engineers One Great George St Westminster London, SW1P 3AA Tel:

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.