Neagh Bann CFRAM Study
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North Western - Neagh Bann CFRAM Study UoM 36 Hydrology Report IBE0700Rp0009 rpsgroup.com/ireland North Western – Neagh Bann CFRAM Study UoM 36 Hydrology Report DOCUMENT CONTROL SHEET Client OPW Project Title North Western – Neagh Bann CFRAM Study Document Title IBE0700Rp0009_UoM 36 Hydrology Report_F03 Document No. IBE0700Rp0009 DCS TOC Text List of Tables List of Figures No. of This Document Appendices Comprises 1 1 130 1 1 4 Rev. Status Author(s) Reviewed By Approved By Office of Origin Issue Date B. Quigley D01 Draft U. Mandal M. Brian G. Glasgow Belfast 08/11/2013 L. Arbuckle B. Quigley F01 Draft Final U. Mandal M. Brian G. Glasgow Belfast 31/03/2014 L. Arbuckle B. Quigley F02 Draft Final U. Mandal M. Brian G. Glasgow Belfast 11/08/2015 L. Arbuckle B. Quigley F03 Draft Final U. Mandal M. Brian G. Glasgow Belfast 08/07/2016 L. Arbuckle rpsgroup.com/ireland Copyright Copyright - Office of Public Works. All rights reserved. No part of this report may be copied or reproduced by any means without prior written permission from the Office of Public Works. Legal Disclaimer This report is subject to the limitations and warranties contained in the contract between the commissioning party (Office of Public Works) and RPS Group Ireland rpsgroup.com/ireland NW-NB CFRAM Study UoM 36 Hydrology Report – FINAL TABLE OF CONTENTS LIST OF FIGURES ................................................................................................................................. IV LIST OF TABLES .................................................................................................................................. VI ABBREVIATIONS .................................................................................................................................. IX 1 INTRODUCTION ........................................................................................................................ 1 1.1 OBJECTIVE OF THIS HYDROLOGY REPORT ........................................................................ 3 1.2 SUMMARY OF THE AVAILABLE DATA .................................................................................. 3 1.2.1 Summary of Available Hydrometric Data ......................................................... 3 1.2.2 Summary of Available Meteorological Data ..................................................... 5 2 METHODOLOGY REVIEW ........................................................................................................ 8 2.1 HYDROLOGICAL ANALYSIS ................................................................................................ 8 2.2 USE OF METEOROLOGICAL DATA ...................................................................................... 9 2.3 DESIGN FLOW ESTIMATION .............................................................................................. 9 2.3.1 Index Flood Flow Estimation ............................................................................ 9 2.3.2 Growth Curve / Factor Development .............................................................. 11 2.3.3 Design Flow Hydrographs .............................................................................. 11 2.4 HYDROLOGY PROCESS REVIEW ..................................................................................... 12 2.5 CATCHMENT BOUNDARY REVIEW AND HYDROLOGICAL ESTIMATION POINTS ..................... 14 2.5.1 Catchment Boundary Review ......................................................................... 14 2.5.2 Hydrological Estimation Points ....................................................................... 16 3 HYDROMETRIC GAUGE STATION RATING REVIEWS ....................................................... 18 3.1 METHODOLOGY ............................................................................................................. 18 3.2 RATING REVIEW RESULTS .............................................................................................. 19 3.3 IMPACT OF RATING REVIEWS ON HYDROLOGICAL ANALYSIS ............................................. 22 4 INDEX FLOOD FLOW ESTIMATION ...................................................................................... 24 4.1 MODEL 1 – BALLINAMORE .............................................................................................. 25 4.2 MODEL 2 – BALLYCONNELL ............................................................................................ 28 4.3 MODEL 3 - BALLYBAY ..................................................................................................... 31 4.4 MODEL 4 – CAVAN ......................................................................................................... 35 4.5 MODEL 5 – BUNDORAN AND TULLAGHAN ......................................................................... 40 4.5.1 Model 5a ......................................................................................................... 40 4.5.2 Model 5b ......................................................................................................... 40 4.5.3 Model 5c ......................................................................................................... 40 4.6 INDEX FLOOD FLOW CONFIDENCE LIMITS ........................................................................ 43 5 FLOOD FREQUENCY ANALYSIS AND GROWTH CURVE DEVELOPMENT ..................... 44 5.1 OBJECTIVE AND SCOPE .................................................................................................. 44 5.2 METHODOLOGY ............................................................................................................. 44 5.2.1 Selection of Statistical Distribution ................................................................. 44 IBE0700Rp0009 i Rev F03 NW-NB CFRAM Study UoM 36 Hydrology Report – FINAL 5.2.2 Forming a Pooling Region and Groups .......................................................... 44 5.2.3 Growth Curve Development ........................................................................... 44 5.2.4 Limitations in the FEH and FSU Studies ........................................................ 45 5.3 DATA AND STATISTICAL PROPERTIES .............................................................................. 45 5.3.1 Flood Data ...................................................................................................... 45 5.3.2 Pooling Region Catchment Physiographic and Climatic Characteristic Data 49 5.3.3 Statistical Properties of the AMAX series ....................................................... 51 5.4 STATISTICAL DISTRIBUTION ............................................................................................ 52 5.5 GROWTH CURVE ESTIMATION POINTS ............................................................................ 54 5.6 POOLING REGION AND GROUP FOR GROWTH CURVE ESTIMATION ................................... 55 5.6.1 Pooling Region ............................................................................................... 55 5.6.2 Pooling Group................................................................................................. 56 5.7 GROWTH CURVE ESTIMATION ........................................................................................ 56 5.7.1 Choice of Growth Curve Distributions ............................................................ 56 5.7.2 Estimation of Growth Curves .......................................................................... 57 5.7.3 Examination of Growth Curve Shape ............................................................. 58 5.7.4 Recommended Growth Curve Distribution for UoM 36 .................................. 62 5.8 RATIONALISATION OF GROWTH CURVES ......................................................................... 64 5.8.1 Relationship of Growth Factors with Catchment Characteristics ................... 64 5.8.2 Generalised Growth Curves ........................................................................... 65 5.8.3 Results for different parent pooling regions for UoM 36 ................................ 69 5.8.4 Estimated Growth Factors for UoM 36 ........................................................... 71 5.8.5 Comparison of the at-site growth curves with the pooled growth curves ....... 73 5.8.6 Growth factors for all HEPs in the UoM 36 .................................................... 77 5.9 COMPARISON WITH FSR GROWTH FACTORS .................................................................. 83 5.10 GROWTH CURVE DEVELOPMENT SUMMARY .................................................................... 83 6 DESIGN FLOWS ...................................................................................................................... 85 6.1 DESIGN FLOW HYDROGRAPHS ....................................................................................... 85 6.1.1 FSU Hydrograph Shape Generator ................................................................ 85 6.1.2 FSSR 16 Unit Hydrograph Method................................................................. 86 6.2 COASTAL HYDROLOGY ................................................................................................... 88 6.2.1 ICPSS Levels ................................................................................................. 88 6.2.2 ICWWS Levels ............................................................................................... 89 6.2.3 Consideration of ICPSS and ICWWS Outputs ............................................... 90 6.3 JOINT PROBABILITY .......................................................................................................