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Introduction to Flooding

Introduction to Flooding. by Environment Agency, Halcrow and Universities of Cardiff, Heriot Watt and Cambridge. General Background to Flooding. Background. Up to 5m people in U.K. are at risk from river and coastal flooding Annual average damage estimated at £0.7 bn

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Introduction to Flooding

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  1. Introduction to Flooding by Environment Agency, Halcrow and Universities of Cardiff, Heriot Watt and Cambridge

  2. General Backgroundto Flooding

  3. Background • Up to 5m people in U.K. are at risk from river and coastal flooding • Annual average damage estimated at £0.7 bn • Recent floods have been more frequent • Damage extent exacerbated by: • Extensive building on flood plains • Alterations to riverine channels • Changes in recorded rainfall patterns • Changes in land management use • Climate change expected to increase flooding

  4. Background • River flooding essentially a natural process that helps shape landscape • Flooding generally caused by high rainfall and inability of land to drain water effectively - aggravated further when ground saturated • Flooding frequently leads to serious water pollution and epidemiological problems • Flood damage extent often exacerbated by: • Inadequate flood warning systems • Use of crude hydroinformatics tools • Inadequately trained model users

  5. General Views

  6. Whole towns often affected by flooding

  7. Historic town of York – floods regularly

  8. York Castle does not flood though

  9. Buildings have increasingly been built on flood plain

  10. Commercial properties often badly affected by flooding

  11. Flood water can rise rapidly in steep catchment

  12. Embankment breaches often cause severe damage

  13. Fire service are key providers of emergency support

  14. Army also provides support under severe conditions

  15. Floods bring misery and stress to families

  16. Elderly and disabled often most affected

  17. River TaffSome Typical Challenges

  18. Typical weir built in past for flood control

  19. 1979 Flood – defences overtop causing rapid flooding

  20. Flood of 1979 – many properties flooded

  21. Sandbags used to defend against flooding

  22. Typical use of temporary defences

  23. Typical contamination after flooding

  24. Much of Western Cardiff below embankments

  25. Many old bridges throttle flow during floods

  26. Single span modern bridges cause less throttling

  27. Significant changes in resistance either side of river

  28. Hurricane KatrinaAugust 2005

  29. High sea surface temperatures fuel hurricane

  30. Hurricane Katrina from satellite

  31. Hurricane power illustrated by vessel on shore

  32. New Orleans levee protection and bathymetry

  33. Mississippi river pours into New Orleans

  34. Flooding of downtown New Orleans

  35. Flood Defence

  36. Thames Barrier – world’s largest movable flood barrier

  37. Flooding of Thames Estuary

  38. Protection of Property

  39. Floodguards International • State-of-art flood guards designed to protect homes and properties from flooding • Accessories designed to complement guards e.g. brick sealant and one-way toilet valves • Based on principle of arch dam design with pressure force used to enhance seal • Simple glass reinforced plastic (GRP) guards: • Permanent and unobtrusive narrow frame fixed around doors and air vents • Removable curved lightweight guards readily clipped in place before flooding

  40. Arch Dam Principle Mountain Mountain Arch Dam Water Pressure • Water pressure transmitted to dam • Forces then transmitted to mountain

  41. Flood Guard Principle House Wall Door House Wall Flood Guards Water Pressure • Water pressure transmitted to flood guard • Force then used to increase seal efficiency

  42. Without guards Protection of Patio Doors With guards

  43. Air Vent Protection

  44. Model of Seepage through Brickwork Aim:- Predict protection times and seepage for extended flooding • Research Centre’s model HEMAT used to predict seepage rates through brickwork and under wall foundations • Finite volume method solves flow equations • Irregular triangular mesh used to fit domain

  45. Triangular Mesh

  46. Model Results

  47. Summary of Floodguards Benefits • Based on state-of-the-art technology • Relatively inexpensive and lightweight • Frame can be fitted easily and concealed • Prevents flooding of properties through doors, windows, air vents etc • Prevents silt and sewage contamination

  48. Environment Agency

  49. Who Are They? • Have over 10,000 staff - mainly scientists, engineers, planners - responsible for environmental protection • Have an annual operating budget of over £0.5 billion • Work in following areas: • Air Quality – regulate release of pollutants • Conservation – important role, especially along rivers • Fish – monitor and study fish habits and ecology • Flood – warn public about flood risk and build defences etc • Land Quality – seek to prevent land from becoming polluted • Navigation – responsible for rivers, estuaries and harbours • Recreation – managing use of inland and coastal waters • Waste – regulate waste management through licencing • Water Quality – ensure quality of surface and ground water • Water Resources – monitor and issue abstraction licences

  50. Environment Agency produce Indicative Flood Maps

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