Overarching Report on the October 2011 Flood Event
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Eastern CFRAM Study Overarching Report on the October 2011 Flood Event IBE0600Rp0014 rpsgroup.com/ireland rpsgroup.com/ireland Eastern CFRAM Study Overarching Report on the October 2011 Flood Event DOCUMENT CONTROL SHEET Client: OPW Project Title: Eastern CFRAM Study Document Title: Overarching Report on the October 2011 Flood Event Document No: IBE0600Rp0014 DCS TOC Text List of Tables List of Figures No. of Appendices This Document Comprises: 1 1 29 1 1 1 Rev. Status Author(s) Reviewed By Approved By Office of Origin Issue Date F. Carragher D01 Draft A. Jackson G. Glasgow Belfast 20/12/2012 B. Quigley F. Carragher F01 Draft Final A. Jackson G. Glasgow Belfast 10/04/2013 B. Quigley F. Carragher F02 Final A. Jackson G. Glasgow Belfast 01/05/2013 B. Quigley Confidentiality statement; The information disclosed in this proposal should be treated as being strictly private and confidential and you are requested to take all reasonable precautions to maintain its status as such. You are requested to use and apply the information solely for the purpose of evaluating this proposal and are asked not at any time to disclose or otherwise make available the information to any third party except for those officers, employees and professional advisers who are required by you in the course of such evaluation to receive and consider the information and who agree to be bound by these non-disclosure terms. rpsgroup.com/ireland Eastern CFRAM Study Overarching Report on the October 2011 Flood Event – FINAL TABLE OF CONTENTS ABBREVIATIONS ............................................................................................................................... III 1 INTRODUCTION ..................................................................................................................... 1 2 DATA COLLECTION ............................................................................................................... 2 2.1 HYDROMETRIC DATA ...................................................................................................... 2 2.2 METEOROLOGICAL DATA ................................................................................................ 3 2.3 REPORTS ...................................................................................................................... 5 2.4 FLOOD EVENT RESPONSE .............................................................................................. 5 2.5 FLOOD EXTENTS ........................................................................................................... 5 3 SUMMARY OF REPORTS ...................................................................................................... 7 3.1 EPA-LA (HYDROMETRIC STATION REPORT) .................................................................... 7 3.1.1 09002 – Griffeen River at Lucan ..................................................................... 7 3.1.2 09009 – Owendoher at Willbrook Road .......................................................... 7 3.1.3 09010 – Dodder at Waldrons Bridge............................................................... 8 3.1.4 09011 – Slang at Frankfort ............................................................................. 8 3.1.5 09037 – Tolka at Botanic Gardens ................................................................. 8 3.1.6 09049 (Maynooth), 10002 (Rathdrum) & 10028 (Knocknamohill) ................... 8 3.1.7 Met Éireann Report (Appendix 1) ................................................................... 8 3.2 INTERIM REVIEW AND RECOMMENDATIONS FOR DCC ....................................................... 9 3.2.1 Overview of events ......................................................................................... 9 3.2.2 Flooding mechanisms and Impacts .............................................................. 10 3.2.3 Mitigation measures ..................................................................................... 11 3.2.4 Conclusions and recommendations .............................................................. 11 3.3 EASTERN CFRAM STUDY, HA09 INCEPTION REPORT ................................................... 12 3.3.1 Details of the October 2011 flood event ........................................................ 12 3.3.2 Behaviour & frequency ................................................................................. 13 4 HYDROLOGICAL ANALYSIS ............................................................................................... 14 4.1 09001 – RYEWATER AT LEIXLIP .................................................................................... 14 4.2 09002 – GRIFFEEN AT LUCAN ...................................................................................... 15 4.3 09010 – WALDRONS BRIDGE ....................................................................................... 16 4.4 09024 – MORELL BRIDGE ............................................................................................ 17 4.5 09035 – KILLEEN ROAD .............................................................................................. 17 4.6 09044 – KERDIFFSTOWN HOUSE .................................................................................. 18 4.7 09048 – ANNES BRIDGE .............................................................................................. 19 4.8 09049 – MAYNOOTH ................................................................................................... 19 4.9 09102 – CADBURYS .................................................................................................... 21 4.10 IMPACT ON CFRAM STUDY HYDROLOGY ...................................................................... 21 5 FLOOD EVENT SUMMARY .................................................................................................. 24 IBE0600Rp0014 i F02 Eastern CFRAM Study Overarching Report on the October 2011 Flood Event – FINAL 5.1 ANNUAL EXCEEDANCE PROBABILITY ............................................................................. 24 5.2 FLOOD EXTENTS .......................................................................................................... 27 6 CONCLUSION & RECOMMENDATIONS ............................................................................. 28 6.1 LIMITATIONS OF THE ANALYSIS ..................................................................................... 28 6.2 RECOMMENDATIONS .................................................................................................... 29 LIST OF FIGURES Figure 2.1: Location of Hydrometric Stations for Analysis ............................................................... 3 Figure 2.2: Met Éireann Daily Rainfall Sums for 23rd / 24th October 2011 ........................................ 4 Figure 3.1: Fitted GEV frequency curve to the observed AMAX records for Ryewater River at Leixlip (Hydr. Stn. 09001) ................................................................................................................... 13 Figure 4.1: Single Site Flood Frequency Analysis at 09001 .......................................................... 14 Figure 4.2: Single Site Flood Frequency Analysis at 09002 .......................................................... 15 Figure 4.3: Single Site Flood Frequency Analysis at 09010 .......................................................... 16 Figure 4.4: Single Site Flood Frequency Analysis at 09024 .......................................................... 17 Figure 4.5: Single Site Flood Frequency Analysis at 09048 .......................................................... 19 Figure 4.6: Single Site Flood Frequency Analysis at 09049 .......................................................... 20 Figure 4.7: Single Site Flood Frequency Analysis at 09102 .......................................................... 21 Figure 5.1: Estimated Fluvial and Pluvial Annual Exceedance Probabilities of the October 2011 Event 26 LIST OF TABLES Table 2.1: Hydrometric Data Available for Analysis ........................................................................ 2 APPENDICES APPENDIX A Flood Extent Maps 21 Pages IBE0600Rp0014 ii F02 Eastern CFRAM Study Overarching Report on the October 2011 Flood Event – FINAL ABBREVIATIONS AEP Annual Exceedance Probability AFA Area for Further Assessment AFF At-site Flood Frequency AMAX Annual Maximum flood series AREA Catchment Area BFI Base Flow Index CFRAM Catchment Flood Risk Assessment and Management DCC Dublin City Council DFI Dublin Flood Initiative ERBD Eastern River Basin District EV1 Extreme Value Type 1 (distribution) (=Gumbel distribution) EPA Environmental Protection Agency FARL Flood Attenuation for Rivers and Lakes FEH Flood Estimation Handbook FEM-FRAMS Fingal East Meath Catchment Flood Risk Assessment and Management Study FRA Flood Risk Assessment FRC FloodResilienCity (project) FRMP Flood Risk Management Plan FSR Flood Studies Report FSU Flood Studies Update GC Growth Curve GDSDS Greater Dublin Strategic Drainage Study GEV Generalised Extreme Value (distribution) GLO General Logistic (distribution) HA Hydrometric Area LA Local Authority LiDAR Light Detection And Ranging OD Ordnance Datum OPW Office of Public Works PFRA Preliminary Flood Risk Assessment Qmed median of AMAX flood series Qbar / QBAR mean average of AMAX flood series RBD River Basin District RFF Regional Flood Frequency SAAR Standard Average Annual Rainfall (mm) SDCC South Dublin County Council SuDS Sustainable Urban Drainage UoM Unit of Management IBE0600Rp0014 iii F02 Eastern CFRAM Study