The National Preliminary Flood Risk Assessment (Pfra)
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THE NATIONAL PRELIMINARY FLOOD RISK ASSESSMENT (PFRA) OVERVIEW REPORT MARCH 2012 2019/RP/001/D FLOOD RELIEF & RISK MANAGEMENT DIVISION ENGINEERING SERVICES OFFICE OF PUBLIC WORKS ACKNOWLEDGEMENTS The Office of Public Works (OPW) would like to acknowledge and thank all those who have contributed towards the preparation of the Preliminary Flood Risk Assessment (PFRA), including: − Bord Gáis − Dept. of Agriculture, Fisheries and Food − Dept. of Environment, Community and Local Government o National Monuments o National Parks and Wildlife Service − Eircom − Environmental Protection Agency − ESB − Geological Survey of Ireland − Health Service Executive − National Roads Authority − Waterways Ireland The OPW also acknowledges those who have undertaken, or assisted with, the technical assessments that have provided information to enable the PFRA to be undertaken, namely Bird Watch Ireland, Compass Informatics, HR Wallingford and RPS. The OPW would in particular like to thank consultants Mott MacDonald who have worked closely with the OPW in the development and implementation of the PFRA, as well as undertaking many of the technical assessments. CONTENTS GLOSSARY 1. INTRODUCTION................................................................................................1 1.1. PRELIMINARY FLOOD RISK ASSESSMENT (PFRA) ...........................1 1.1.1. The ‘Floods’ Directive...........................................................................1 1.1.2. The CFRAM Studies...............................................................................2 1.2. PUBLIC CONSULTATION ON THE PFRA...............................................2 2. PFRA PROCESS .................................................................................................3 2.1. OVERVIEW OF PFRA APPROACH...........................................................3 2.2. FLOOD RISK................................................................................................3 2.3. FLOOD HAZARD – SOURCES OF FLOODING.......................................4 2.4. CONSEQUENCES OF FLOODING ............................................................4 3. HISTORIC FLOOD RISK ASSESSMENT......................................................5 3.1. INTRODUCTION .........................................................................................5 3.2. AVAILABLE HISTORIC FLOOD INFORMATION..................................5 3.3. NATURAL SOURCES OF FLOOD RISK...................................................6 3.3.1. Defining Spatial Areas for Analysis.......................................................6 3.3.2. Historic Hazard .....................................................................................6 3.3.3. Historic Risk...........................................................................................7 3.4. INFRASTRUCTURAL SOURCES OF FLOOD RISK................................8 3.4.1. Local Authority Infrastructure...............................................................8 3.4.2. ESB Infrastructure .................................................................................9 3.4.3. Waterways Ireland Infrastructure..........................................................9 3.5. USE OF HISTORIC HAZARD AND RISK OUTCOMES..........................9 4. PREDICTIVE ANALYSIS ...............................................................................11 4.1. INTRODUCTION .......................................................................................11 4.2. INDICATIVE FLOOD MAPPING.............................................................11 4.2.1. Indicative Fluvial Flood Mapping.......................................................12 4.2.2. Indicative Seawater Flood Mapping....................................................14 4.2.3. Indicative Groundwater Flood Mapping.............................................14 4.2.4. Indicative Pluvial Flood Mapping.......................................................15 4.2.5. Tsunami Floods....................................................................................16 4.2.6. Infrastructural Sources of Flooding ....................................................17 4.3. POTENTIAL CONSEQUENCES...............................................................17 4.4. INDICATIVE FLOOD RISK ANALYSIS .................................................18 4.4.1. General Methodology ..........................................................................18 4.4.2. Describing Flood Risk .........................................................................19 4.4.3. Flood Risk for Point Receptors............................................................20 4.4.4. Flood Risk to the Environment ............................................................20 4.4.5. Flood Risk to Agriculture.....................................................................21 4.4.6. Flood Risk to Roads and Rail ..............................................................21 4.4.7. Infrastructural Sources of Flooding ....................................................21 PFRA Main Report (i) March 2012 4.5. POTENTIAL IMPACTS OF CLIMATE CHANGE...................................22 4.6. USE OF PREDICTIVE HAZARD AND RISK OUTCOMES ...................22 5. CONSULTATIVE PROCESS..........................................................................23 5.1. CONSULTATION TO DATE.....................................................................23 5.2. PUBLIC CONSULTATION PROCESS.....................................................23 6. OUTCOMES ......................................................................................................25 6.1. THE DESIGNATION OF AFA S.................................................................25 6.1.1. Guiding Principles for Designation of AFAs.......................................25 6.1.2. Probable and Possible AFAs ...............................................................26 6.2. NATURAL SOURCES OF FLOODING....................................................26 6.2.1. Flood Risk to the Environment ............................................................26 6.2.2. Flood Risk to Agriculture.....................................................................27 6.2.3. Flood Risk from Tsunamis ...................................................................27 6.2.4. Areas Benefiting from Flood Relief Schemes.......................................28 6.3. INFRASTRUCTURAL SOURCES OF FLOODING.................................28 6.3.1. Urban Storm-Water Drainage Systems ...............................................28 6.3.2. Reservoirs ............................................................................................28 6.3.3. Water Supply System............................................................................29 6.3.4. ESB.......................................................................................................29 6.3.5. Waterways Ireland...............................................................................29 6.4. CROSS-BORDER COORDINATION........................................................29 7. FINAL DESIGNATION OF AFAS..................................................................31 PFRA Main Report (ii) March 2012 APPENDICES APPENDIX A ARTICLES 4 AND 5 OF THE EU ‘FLOODS’ DIRECTIVE APPENDIX B TECHNICAL PFRA REPORTS APPENDIX C HISTORIC FLOOD RISK ASSESSMENT Appendix C.1 Records of No. Past Flood Events per Location Appendix C.2 Records of Financial Damage for Past Floods Appendix C.3 Records of No. of Properties Flooded During Past Floods Appendix C.4 Records of Past Floods Related to Infrastructure APPENDIX D RECEPTOR VULNERABILITIES APPENDIX E PREDICTIVE FLOOD RISK ASSESSMENT OUTCOMES Appendix E.1 Predictive Analysis Outcomes for Fluvial and Coastal Flood Risk Appendix E.2 Predictive Analysis Outcomes for Groundwater Flood Risk Appendix E.3 Predictive Analysis Outcomes for Pluvial Flood Risk Appendix E.4 Predictive Analysis Outcomes for Environmentally Designated Sites Appendix E.5 Maps of Predictive Agricultural Flood Risk APPENDIX F PROBABLE AND POSSIBLE AREAS FOR FURTHER ASSESSMENT PFRA Main Report (iii) March 2012 (Blank Page) PFRA Main Report (iv) March 2012 GLOSSARY TERMS USED Area for Further Areas where, based on the Preliminary Flood Risk Assessment (AFA) Assessment, the risks associated with flooding are potentially significant, and where further, more detailed assessment is required to determine the degree of flood risk, and develop measures to manage and reduce the flood risk. Communities Cities, towns, villages or townlands where there are a collection of homes, businesses and other properties Consequences The impacts of flooding, which may be physical (e.g., damage to a property or monument) or a disruption (e.g., loss of electricity supply or blockage of a road). Flood Extent The extent of land that has been, or might be, flooded. Flood extent is often represented on a flood map. Hazard Something that can cause harm or detrimental consequences. In this report, the hazard referred to is flooding. Indicative This term is typically used to refer to the flood maps developed under the Preliminary Flood Risk Assessment. The maps are developed using simple methods, and generally national datasets, and are hence approximate, and not highly detailed, with some local anomalies. Point Receptor Something that might suffer hamr or damage as a result of flood, that is at a particular location that does not cover a large area, such as a house, office, monument, hospital, etc. Receptor Something that might suffer