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Denbigh flood risk management scheme case study


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Presentation made to North Wales Branch of the Institution of Civil Engineers on the Denbigh Flood Risk Management Scheme and community resilience measures that were carried out.

Presentation made to North Wales Branch of the Institution of Civil Engineers on the Denbigh Flood Risk Management Scheme and community resilience measures that were carried out.

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  • 1. Martin Wright Associates Coastal & flood risk management engineers Flood Risk Management and Community Resilience Denbigh Flood Risk Management Scheme
  • 2. INTRODUCTION Mike Wellington
  • 3. FLOODING IN THE UK• Autumn 2000 was the wettest autumn in England and Wales for over 270 years• Parts of the UK were inundated by floodwater, sometimes on several occasions• The Government invited the President of the Institution of Civil Engineers to establish a Commission to consider what approaches to managing fluvial flood risk are appropriate to the 21st century
  • 4. FLOODING IN THE UK• In 2001 ICE published ‘Learning to Live with Rivers’• This review supported the EA’s initiative in raising awareness of fluvial flooding concluding that ‘floods can only be managed not prevented, and that communities must learn to live with rivers• Traditional approach in the UK focused on Defences and managing the likelihood of flooding
  • 5. NEW APPROCHES TO FLOOD RISK MANAGEMENT• Following widespread flooding in England in the Summer of 2007, (Gloucester) Sir Michael Pitt undertook review of flood defences in the England.• Published in 2008 and made over 90 recommendations• Both Welsh Assembly Government and DEFRA keen to adopt a more holistic approach to how we deal with flood risk.• In addition to the traditional methods used to prevent flooding - such as building bigger and better defences now a greater focus on ensuring that the community at risk is fully aware of the potential consequences of a flood.
  • 6. RECOMMENDATIONS OF THE PITT REVIEW (ENGLAND)• increasing interest in alternative sustainable adaptation measures, e.g. property resilience measures to enable a flexible approach to adaptation• the public need to be aware of a flooding risk before they can take action to minimise it• the EA should work to raise awareness in flood risk areas identifying a range of mechanisms to warn the public, particularly the vulnerable, in response to flooding to reduce the impact of floods on individuals.• levels of awareness should be raised through education and publicity programmes
  • 7. RECOMMENDATIONS OF THE PITT REVIEW (ENGLAND)• the public should make up a flood kit• raising awareness of risks can build community resilience to flooding with a clear understanding of risk
  • 8. NEW APPROCHES TO FLOOD RISK MANAGEMENT• Welsh Assembly Government’s Environmental Strategy Plan recognised findings of Pitt and developed the New Approaches Programme - A new approach to flood risk management in Wales• The New Approaches programme is aimed at facilitating this change. The approach requires stronger partnership working, more robust public engagement and a focus on consequence management.
  • 9. DENBIGH FLOOD RISK MANAGEMENT SCHEME• In 2002, Denbighshire County Council carried out a Pre-Feasibility Study of a culverted watercourse (known as Henllan Brook) that flows through the town of Denbigh. The study focused on a specific length of the watercourse in the Lenten Pool area of the town where flooding is particularly prevalent and severe.• Work on the Project Appraisal Report (PAR) commenced in January 2009 with an enhanced scope to include a detailed strategic investigation of the entire length of the brook to ensure that any proposed improvements in the Lenten Pool area would not create new problems further downstream.
  • 10. DENBIGH FLOOD RISK MANAGEMENT SCHEME• In February 2009, the scope of the PAR was further extended as a result of the Council’s successful bid to Welsh Assembly Government (WAG) to be part of a Flood and Coastal Risk Management Programme that attracted European Union Convergence Funding• As a result of the above developments the content of the PAR was expanded to meet the aims and objectives of the strategic WAG programme - which in turn have been developed to be consistent with;a) WAG’s ‘New Approaches Programme’b) the recent Pitt Review andc) the European Union Directive on the assessment and management of flood risks
  • 11. Henllan Brook
  • 12. Historic Flooding in Denbigh
  • 13. Flooding Lenten Pool – October 2001
  • 14. DENBIGH FLOOD RISK MANAGEMENT SCHEME• Ordinary watercourse flowing through urban area• Culverted on an ad-hoc basis over past 200 years• Poor structural condition• Limited maintenance regime• Extensive commercial & residential development• Regular and severe flooding• 226 residential and 26 commercial properties at risk Problem
  • 15. Flood Paths and Properties at Risk
  • 16. DENBIGH FLOOD RISK MANAGEMENT SCHEME• No guidance from WAG or ‘toolbox’ regarding implementation of ‘New Approaches’• Rural community with large percentage of vulnerable adults• Community did not fully recognise or understand flood risk• Barriers to flood awareness raising that need to be overcome Challenges
  • 17. DENBIGH FLOOD RISK MANAGEMENT SCHEME• Public apathy• Denial of problem due to fears of property devaluation or inability to get insurance• Lack of Knowledge• Forgetting to act as serious flooding had not happened recently• Lack of motivation• Someone else’s problem Barriers to awareness raising
  • 18. Community Resilience
  • 19. HOLISTIC SOLUTION ADOPTED TRADITIONAL NEW APPROACH (FLOOD RISK MANAGEMENT)1) Improve existing infrastructure 1) Improve existing infrastructure 2) Increase built environment resilience 3) Raise public awareness 4) Enhance community resilience 5) Improve flood warnings 6) Better land use management 7) Improve emergency response/recovery 8) Develop better asset management 9) Collaboration with key stakeholders 10) Protect/enhance the environmentFlood Alleviation to Flood Risk Management
  • 20. REDUCING FLOOD RISK IN DENBIGHTRADITIONAL• 1,440m of new culverts ranging in size from 300mm to 2.1m x 1.0m• Combination of open cut and tunnelling• 635m of watercourse re-profiling and improvements• Repair of existing culverts• New screens• New flood storage areasImproving Existing Infrastructure
  • 21. Proposed works
  • 22. Phase One – A525 to Cysgodfa
  • 23. Phase One –Cysgodfa Improved Inlet Structure
  • 24. Phase 1A – Ruthin Road
  • 25. Intake Structure at Clwyd Avenue
  • 26. Phase 2 – Flow Attenuation
  • 27. Phase 2 – Wet Ponds
  • 28. Phase 2 – Attenuation Pond
  • 29. Phase 2 – Lodge Farm
  • 30. Phase 2 – Control structure
  • 31. Phase 3 – Lenten Pool
  • 32. Phase 3 – Lenten Pool (Tunnelling)
  • 33. Phase 3 – Lenten Pool (Auger boring)
  • 34. Phase 3 – Lenten Pool (Archaeology)
  • 35. NEW APPROACH - ENGAGING THE LOCAL COMMUNITY• Press Releases• Scheme logo and signage• Local advertising• Public Exhibitions and displays• Website and Social Media• Flood Risk Workshops• Weather centre• Visualisations RAISING PUBLIC AWARENESS
  • 36. Press release
  • 37. Scheme sign board
  • 38. Scheme logo
  • 39. Car Parking Advertisement
  • 40. Exhibitions
  • 41. - Home
  • 42. - FAQ
  • 43. facebook
  • 44. Twitter@DFRMS
  • 45. Text Alerts
  • 46. Community Action
  • 47. NEW APPROACH – EDUCATIONAL PRESENTATIONS• School visits and Flood Risk Workshops• Talks and interactive sessions• Relating the scheme to the curriculum• Questionnaires to take home to parents• Competitions and prizes• Weather centre• Visualisations RAISING PUBLIC AWARENESS
  • 48. How do you measure how effective it is? Getting a baseline and monitoring improvements using ACTIVOTERAISING PUBLIC AWARENESS
  • 49. Activote
  • 50. Activote
  • 51. Educational presentations
  • 52. 1. Options for solving flooding in Denbigh 2. What should be in a Personal Flood Plan? 3. What is in a flood kit?Flood Risk Workshops
  • 53. Flood Paths and Properties at Risk
  • 54. Personal flood plan
  • 55. Personal flood plan
  • 56. Flood kit
  • 57. Weather station
  • 58. Cost of Damages taken from the FHRC multi-coloured manual)
  • 59. How do you measure how effective it is? FLOOD RISK = LIKELIHOOD OF CONSEQUENCES OF FLOODING X FLOODING (Traditional (New Approaches) Approach) 1% risk reduction? Design Standard – 5% risk reduction?1 in 100 % (plus 20% c/c) 10% risk reduction? 25% risk reduction? Raising Public Awareness
  • 60.• Number of unique visitors: 1504• Number of pages: 18,000• Number of hits: 150,034 Scheme Website
  • 61. Temporary bridges Phase 1 removed Phase 2 Starts on Road Works in site Closure farmland School Exhibition Car park visits start in library adverts go liveScheme Website
  • 62. Phase 3 starts Constructionon site work complete Excavation of thrust pits Tunnelling Flooding advice works sent to residents Scheme Website
  • 63. Flood Risk Workshops• 540 pupils actively involved• By using the activote system it was possible to get instant feedback, 1 mark was awarded for the correct answer• At the end of each session two sets of average scores were recorded•A null hypothesis of:“no difference in respondent’s awareness of flooding afterparticipating in a flood risk workshop” was used. Educational and School visits
  • 64. 1.2 1.0 0.8 P(d) 0.6 0.4 P normal 0.2 P data 0.0 0.0 0.5 1.0 1.5 2.0 2.5• Number of points = n = 16 d(i)• Standard error of the sample = s = σd/√n = 0.570/4 = 0.143• Number of degrees of freedom = DF = n-1 = 16-1 = 15• Let D be the mean value of d(i) in the whole population; in order to find out the probability that D<0• t = (μd – D)/SE = (1.369 – 0)/0.143 = 9.605 with 15 degrees of freedom• P(T) from this result is approximately equal to unity and therefore we can reject the null hypothesis H0: μd <= 0; in fact, even t15,0.005 is only 2.947<< 9.605• Concluding that the Flood Risk Workshop are highly effective at raising awareness Educational and School visits
  • 65. PERSONAL FLOOD PLANS (MOST POPULAR ANSWERS)1. Contact members of the family and friends to ensure that they are safe2. Contact details of the council, EA and Emergency Services3. Have some sandbags ready in case of a flood4. Make sure that you have insurance5. Move valuables upstairs (or backup personal information or sentimental photographs to the internet) Flood Risk Workshop Feedback
  • 66. PERSONAL FLOOD PLANS (LEAST POPULAR ANSWERS)1. Flood barrier Flood Risk Workshop Feedback
  • 67. FLOOD KITS (MOST POPULAR ANSWERS)1. Food and water2. Torch3. First Aid Kit4. Mobile phones5. Life jacket6. Camera7. Radio Flood Risk Workshop Feedback
  • 68. FLOOD KITS (LEAST POPULAR ANSWERS)1. Lifeboat2. Armbands3. Umbrella Flood Risk Workshop Feedback
  • 69. Flood Risk on School Curriculum
  • 70. Flood Risk on School Curriculum
  • 71. • A register of local events was compiled• Events attended included: Denbigh Show Denbigh Plum Festival Denbigh Heritage Festival St David’s Day Festival Denbigh Past, Present & Future• 1600 members of the community engaged Public Engagement Exhibitions
  • 72. Displays were set up throughout the town at:• Denbigh Library• Foyer of Denbighshire County Council Office• Morrison Supermarket• Post Office and General Store• Community Centre• Public Houses Public Engagements - Displays
  • 73. • Denbigh Business Group • Rotary Group • Community Group • Identified Scheme ChampionsPublic Engagement – Community Groups
  • 74. • Facebook 121 regular visitors• Twitter 19 followers• Text Alert: 15 subscribers Social Media
  • 75. SCHEME LEGACYHow do you ensure public awareness and resilience is maintained?How long lasting is a public awareness campaign?Flood Risk Management Plan1. Understanding the Existing Risk and Potential Consequences to the Community2. Measures to Manage Risk3. Managing Future Risks – Action Plan4. Technical Summary FLOOD RISK MANAGEMENT PLAN
  • 76. Prior to scheme
  • 77. Community Action
  • 78.
  • 79. RECOMMENDATIONS• Flood awareness & resilience included in the National Curriculum• Funding for continuing awareness raising (post scheme) ring fenced• Consideration given to reducing design standards from 1 in 100 yr (plus 20% for climate change) to a lesser standard for the construction of new defences but use awareness and resilience measures to make up shortfall• Funding for design and development of schemes should be made available to enable better forward planning Flood Risk Management
  • 80. RECOMMENDATIONS• Flood risk management plans a mandatory operational tool linked to the MARP, could be similar to CDM Health and Safety file• Development of modern technology to reach wider community including socially excluded and vulnerable members of society• Use of social media is relatively inexpensive and should be developed to become the standard Flood Risk Management
  • 81. Effect of ‘new’ legislation and responsibilities • The Water Industry (Adoption of Private Sewers Regulations 2011) • Flood & Water Management Act 2010 requires Local Authorities to:  take the lead in managing the risk of all local floods  investigate flood events and publish results  develop, maintain and apply a local flood risk strategy  establish and maintain a register of structures & features relevant to flood risk  designate structures that are relevant to flood risk  build partnerships and ensure effective multi-agency working  approve, adopt and maintain SuDS on new developments  ensure flood resilience is incorporated into new buildings
  • 82. Martin Wright Associates Coastal & flood risk management engineers QUESTIONS ? For further information: or assistance please do not hesitate to contact: Martin Wright Associates 01244 677656 Mike Wellington Thank You