Floods: Past and Present Issues

1. “Floods - Past and Present Issues”Address given to The Royal Scottish Society of Arts11th February 2002EdinburghbyProfessor George Fleming FREng FRSE FICE FASCE Professor of Civil Engineering, University of StrathclydeManaging Director of EnviroCentreChairman, ICE Presidential Commission Undertaking a Technical Review of Flooding in England and Wales

2. 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?

3. -V-

4. INTRODUCTION

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

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

7. 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.

8. THE HISTORICAL CONTEXT

9. 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

10. The Forth & Clyde and Union Canal

11. 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

12. HISTORICAL FLOOD ESTIMATION

13. Historical Data Collection

14. “Risk of a one in 100 year flood event” • Only possible once in 100 years • One in 100 chance of flooding X 

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

16. Q / Q x x 5.0 x Analysis of Flood Frequency Curves 4.0 x x x 3.0 x 2.0 1.0 T 2 5 10 25 100 500 1000 y1 -1 0 1 2 3 4 5 6 7 8 Regional Flood Frequency Curve: Scotland (Biswas & Fleming, 1966) Regional Flood Frequency Curve: GB (NERC, 1975) x

17. Flood Estimation Techniques

18. THE CURRENT PROBLEM

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

20. Effect of Constraining Flood Plains

21. Effect of Constraining the Flood Plain

22. Leigh Barrier in Operation

23. Flood Defences at Gainsborough

24. FUTURE FLOODING ISSUES

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

28. Presidential Commission to Review Flooding in England and WalesInstitution of Civil Engineers One Great George StWestminsterLondon, SW1P 3AATel: 0207 665 2232www.icenet.org.uk/presidential.html

29. CONCLUSIONS

30. 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.

31. 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.