North Western - Neagh Bann CFRAM Study UoM 06 Inception Report IBE0700Rp0003 rpsgroup.com/ireland Photographs of flooding on cover provided by Rivers Agency rpsgroup.com/ireland North Western – Neagh Bann CFRAM Study UoM 06 Inception Report DOCUMENT CONTROL SHEET Client OPW Project Title Northern Western – Neagh Bann CFRAM Study Document Title IBE0700Rp0003_UoM 06 Inception Report_F02 Document No. IBE0700Rp0003 DCS TOC Text List of Tables List of Figures No. of This Document Appendices Comprises 1 1 97 1 1 4 Rev. Status Author(s) Reviewed By Approved By Office of Origin Issue Date D01 Draft Various K.Smart G.Glasgow Belfast 30.11.2012 F01 Draft Final Various K.Smart G.Glasgow Belfast 08.02.2013 F02 Final Various K.Smart G.Glasgow Belfast 08.03.2013 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 the prior written permission of 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 North Western – Neagh Bann CFRAM Study UoM 06 Inception Report – FINAL ABBREVIATIONS AA Appropriate Assessment AEP Annual Exceedance Probability AFA Area for Further Assessment AMAX Annual Maximum flood series APSR Area of Potentially Significant Risk CFRAM Catchment Flood Risk Assessment and Management CC Coefficient of Correlation COD Coefficient of Determination COV Coefficient of Variance cSAC Candidate Special Area of Conservation DAHG Department of Arts, Heritage and the Gaeltacht DARD Department of Agriculture and Rural Development DOE Department of the Environment DTM Digital Terrain Model EIA Environmental Impact Assessment EPA Environmental Protection Agency ESB Electricity Supply Board EU European Union EV1 Extreme Value Type 1 (distribution) (=Gumbel distribution) FRA Flood Risk Assessment FRMP Flood Risk Management Plan FRR Flood Risk Review IBE0700Rp0003 i RevF02 North Western – Neagh Bann CFRAM Study UoM 06 Inception Report – FINAL FSU Flood Studies Update FSSR Flood Studies Supplementary Report GEV Generalised Extreme Value (distribution) GLO General Logistic (distribution) GIS Geographical Information Systems GSI Geological Survey of Ireland HA Hydrometric Area HEP Hydrological Estimation Point HGF Highest Gauged Flow HPW High Priority Watercourse ICPSS Irish Coastal Protection Strategy Study IFSAR Interferometric Synthetic Aperture Radar IRBD International River Basin District LA Local Authority LAP Local Area Plan LN2 2 Parameter Log Normal (distribution) MAF Mean Annual Flow MPW Medium Priority Watercourse NDHM National Digital Height Model NDTM National Digital Terrain Model NHA Natural Heritage Area NIAH National Inventory of Architectural Heritage NBIRBD Neagh Bann International River Basin District NPWS National Parks and Wildlife Service IBE0700Rp0003 ii RevF02 North Western – Neagh Bann CFRAM Study UoM 06 Inception Report – FINAL NWIRBD North Western International River Basin District OD Ordnance Datum OPW Office of Public Works OSi Ordnance Survey Ireland PEE Proportional Error Estimate PFRA Preliminary Flood Risk Assessment Qmed median of AMAX flood series Qbar mean average of AMAX flood series RA Rivers Agency RBD River Basin District RBMP River Basin Management Plan RMSE Root Mean Square Error SAAR Standard Average Annual Rainfall (mm) SEA Strategic Environmental Assessment SAC Special Area of Conservation SC Survey Contract SI Statutory Instrument SPA Special Protection Area SuDS Sustainable Urban Drainage System UoM Unit of Management WFD Water Framework Directive WP Work Package WWI Waterways Ireland IBE0700Rp0003 iii RevF02 North Western – Neagh Bann CFRAM Study UoM 06 Inception Report – FINAL TABLE OF CONTENTS 1 INTRODUCTION ........................................................................................................................ 1 1.1 OBJECTIVE OF THIS INCEPTION REPORT ............................................................................. 3 1.2 APPROACH TO PROJECT DELIVERY .................................................................................... 3 2 DATA COLLECTION ................................................................................................................. 5 2.1 DATA COLLECTION PROCESS ............................................................................................. 5 2.1.1 Initial Data Received ........................................................................................ 5 2.1.2 Data Requested................................................................................................ 8 2.2 DATA MANAGEMENT AND REGISTRATION .......................................................................... 11 2.3 DATA REVIEW ................................................................................................................. 11 2.3.1 Flood Relief / Risk Management Measures ................................................... 11 2.3.2 Historical Flood Data ...................................................................................... 13 2.3.3 Baseline Mapping ........................................................................................... 13 2.3.4 Hydrometric Data............................................................................................ 13 2.3.5 Meteorological Data ....................................................................................... 14 2.3.6 Land Use Data................................................................................................ 14 2.3.7 Planning and Development Information ......................................................... 15 2.3.8 Environmental Data ........................................................................................ 16 2.3.9 Soil and Geological Data ................................................................................ 18 2.3.10 Defence and Coastal Protection Asset Data .................................................. 18 2.4 DATA OUTSTANDING ....................................................................................................... 18 2.5 DATA GAPS .................................................................................................................... 18 2.6 CONCLUSION ................................................................................................................. 20 3 SURVEYS ................................................................................................................................ 21 3.1 CHANNEL & CROSS-SECTION SURVEYS ............................................................................ 21 3.2 FLOOD DEFENCE ASSETS ................................................................................................ 21 3.3 FLOODPLAIN SURVEY ...................................................................................................... 22 3.4 PROPERTY SURVEY ........................................................................................................ 22 4 PRELIMINARY HYDROLOGICAL ASSESSMENT AND METHOD STATEMENT ................ 24 4.1 HYDROMETRIC DATA ....................................................................................................... 24 4.1.1 Hydrometric data – UoM 06 ........................................................................... 24 4.1.2 Application of Hydrometric Data within UoM 06 ............................................. 28 4.1.3 Hydrometric Stations along modelled watercourses ...................................... 30 4.1.4 Rating Reviews – North Western – Neagh Bann CFRAM Study ................... 32 4.1.5 Summary of Hydrometric Data ....................................................................... 35 4.2 METEOROLOGICAL DATA ................................................................................................. 38 4.2.1 Daily Rainfall Data .......................................................................................... 38 4.2.2 Hourly Rainfall Data ....................................................................................... 40 IBE0700Rp0003 iv RevF02 North Western – Neagh Bann CFRAM Study UoM 06 Inception Report – FINAL 4.2.3 Rainfall Radar Data ........................................................................................ 42 4.2.4 Summary of Meteorological Data ................................................................... 42 4.3 HISTORICAL FLOOD EVENTS – SOURCES OF INFORMATION ................................................ 43 4.3.1 Hydrometric Data............................................................................................ 44 4.3.2 Historical flood Events .................................................................................... 45 4.4 PRELIMINARY ASSESSMENT OF PAST FLOODS AND FLOODING MECHANISMS ....................... 51 4.4.1 Past flooding history and selection of flood events ........................................ 51 4.4.2 Flood Mechanisms in UoM 06 ........................................................................ 52 4.4.3 Flood event behaviour and their frequency .................................................... 52 5 HYDROLOGICAL ANALYSIS METHOD STATEMENT ......................................................... 60 5.1 ANALYSIS OF HYDROMETRIC AND METEOROLOGICAL DATA ................................................ 60 5.1.1 Gauging Station Rating Review ....................................................................