Final Report Volume 1 - Main Report Dublin City Council Fingal County Council 29 April 2005 Final Report 9M2793 A COMPANY OF ROYAL HASKONING COASTAL & RIVERS 19 Baggot Street Lower Dublin 2 Ireland +353 (0)1 634 5353 Telephone +353 (0)1 634 5305 Fax [email protected] E-mail www.royalhaskoning.com Internet Document title Final Report Volume 1 - Main Report Document short title Status Final Report Date 29 April 2005 Project name Dublin Coastal Flooding Protection Project Project number 9M2793 Client Dublin City Council Reference 9M2793 Drafted by Owen Mc Manus/Ian Cooke/John Greenyer Checked by Eric Huyskes Date/initials check …………………. …………………. Approved by Steve Magenis Date/initials approval …………………. …………………. CONTENTS Page 1 INTRODUCTION 1 1.1 General 1 1.2 Scope, Objectives and Project Aims 1 1.3 Sponsoring Authorities 3 1.4 The Dublin Coastal Flooding Protection Project in the Context of the European SAFER Initiative 3 1.4.1 INTERREG III B 3 1.4.2 SAFER 3 1.5 Description of the Project Area 5 1.5.1 Fingal County Council 5 1.5.2 Dublin City Council 6 2 FEBRUARY 2002 EVENT 11 2.1 General Description 11 2.2 Weather Conditions 12 2.2.1 The General Situation 12 2.2.2 The Detailed Meteorological Situation 12 2.3 Marine and Irish Sea Conditions 13 2.4 Fluvial Conditions 13 2.5 UK Met Office Surge Model 14 3 FEBRUARY 2002 FLOODED AREAS 16 3.1 Introduction 16 3.2 Fingal County Council 16 3.2.1 Portmarnock to Baldoyle 16 3.2.2 Sutton 17 3.3 Dublin City Council 18 3.3.1 Dublin City Council – North City Flooding 18 3.3.2 East Wall – Royal Canal 19 3.3.3 East Wall - Other 20 3.3.4 River Liffey – Left Bank 20 3.3.5 Dublin City Council – South City Flooding 21 3.3.6 Sandymount 22 3.3.7 River Liffey – Right Bank 23 3.3.8 Merrion 23 4 DATA COLLECTION 24 4.1 Introduction 24 4.2 Proposal Data – Table 8.1 24 4.3 Post-Project Award Data – Table 8.2 25 4.4 New Surveys 25 4.4.1 Commissioning New Surveys 25 4.4.2 Topographic Survey 26 4.4.3 Bathymetric Survey 27 Dublin Coastal Flooding Protection Project 9M2793 Final Report 29 April 2005 5 ASSET CONDITION SURVEY 28 5.1 Structure of Asset Condition Survey 28 5.2 Information Collected 29 5.3 Presentation of Data 29 5.4 Extension of Asset Management Database 32 5.4.1 Background 32 5.4.2 Inspection of the Fingal County Coastline 33 6 PUBLIC INFORMATION CAMPAIGN 34 6.1 Format of Campaign 34 6.2 Leaflet Survey 34 6.3 Web-site 34 6.4 Public Information Meetings 35 6.5 Responses 35 6.6 Workshops & Stakeholder Meetings 35 6.6.1 Workshop No.1 35 6.6.2 Workshop No.2 36 6.6.3 Workshop No.3 38 6.6.4 Workshop No.4 40 7 OVERVIEW OF INTERNATIONAL BEST PRACTICE 43 7.1 Introduction 43 7.2 Towards the Development of Best Practice 43 7.3 Overview – Key Documents 44 7.4 Site Visits 47 7.5 Links to Strategy and Policy 48 8 REVIEW OF MEAN SEA LEVEL 49 8.1 Background 49 8.2 Historical Sea Level Rise 53 8.2.1 General 53 8.2.2 DCFPP – Tidal Data 54 8.2.3 Permanent Service for Mean Sea Level – Tidal Data 54 8.2.4 Comparison with Other Work 55 8.3 Future Predicted Sea Level Rise 56 8.3.1 General 56 8.3.2 Research and Reports in Ireland 57 8.3.3 Latest Guidance in the UK 57 8.3.4 UK Climate Impacts Programme 2002 (UKCIP02) 58 8.3.5 Intergovernmental Panel on Climate Change 2001 (IPCC(2001)) 59 8.3.6 Dublin Regional Studies 61 8.4 Dublin Coastal Flooding Protection Project Findings 62 8.4.1 General 62 8.4.2 Discussion 62 8.5 Recommendations 65 9 PROBABILISTIC ANALYSIS 66 9.1 Background 66 9.2 Data Collected 66 9.3 The Dublin Port Tide Gauge 67 9.3.1 General 67 Dublin Coastal Flooding Protection Project 9M2793 Final Report 29 April 2005 9.3.2 Historical Development of the Astronomical Tide 69 9.3.3 Historical Development of Mean Sea Level 70 9.3.4 Seiches 70 9.3.5 Surge 72 9.4 Correlation between Surge and Other Meteorological Parameters 74 9.4.1 General 74 9.4.2 Correlation between Surge and Meteorological Conditions 74 9.4.3 Correlation between Surge and River Discharge 76 9.5 Analysis of Extreme Water Levels at Dublin Port Tide Gauge 77 9.5.1 Introduction 77 9.5.2 Extreme Value Analysis of Recorded High Water Levels 78 9.5.3 Extreme Value Analysis of Tides and Surges 79 9.5.4 Joint Probability Analysis of Extreme Tides and Surges 81 9.5.5 Discussion 82 10 NUMERICAL MODELLING – OVERVIEW 84 10.1 Introduction 84 10.2 Numerical Models 84 10.2.1 SWAN Wave Transformation Model 84 10.2.2 FINEL2D – Tidal Model 85 10.2.3 ZWENDL - River Model 85 10.2.4 AMAZON – Overtopping Model 86 10.3 Data Collected 86 10.4 UK Met Office Forecast Models 87 10.4.1 Storm Surge Model 87 10.4.2 Shelf Seas Model 87 10.5 Forecast System 88 11 TIDAL HYDRODYNAMIC MODELLING 90 11.1 Introduction and Methodology 90 11.1.1 Introduction 90 11.1.2 Methodology 90 11.1.3 Tidal Hydrodynamics 90 11.1.4 Calibration & Validation 91 11.1.5 Calculation Runs 91 11.2 Model Construction 91 11.2.1 Finite Element Grid 91 11.2.2 Bathymetry 92 11.2.3 Boundary Conditions 92 11.3 Calibration and Validation of the FINEL Model 92 11.3.1 Calibration against 1st February 2002 Event 92 11.3.2 Validation 95 11.3.3 Conclusion 96 11.4 Water Level Scenarios 97 11.4.1 Warning Points and Tide Scenarios 97 11.4.2 Astronomic Tide 98 11.4.3 Local Surge 98 11.5 Predicting High Water Level 100 11.6 Conclusions and Recommendations 102 11.6.1 Conclusions 102 11.6.2 Recommendations 102 Dublin Coastal Flooding Protection Project 9M2793 Final Report 29 April 2005 12 WAVE AND OVERTOPPING MODELLING 104 12.1 Introduction 104 12.2 Methodology 104 12.3 Wave Modelling 105 12.3.1 Model Geometry and bathymetry 105 12.3.2 Validation 105 12.3.3 Wave Height, Wave Period and Water Level Combinations 107 12.3.4 Boundary Conditions 109 12.4 Overtopping Modelling 110 12.4.1 Warning Points 110 12.4.2 Boundary Conditions 110 12.4.3 Overtopping Quantities 111 13 HYDROLOGICAL ANALYSIS AND RIVER MODELLING 112 13.1 Introduction 112 13.1.1 General 112 13.1.2 Methodology 112 13.1.3 ZWENDL 113 13.1.4 Calibration 113 13.1.5 Simulations 114 13.2 Model construction 114 13.2.1 General 114 13.2.2 Geometrical data 115 13.2.3 Model schematisation 117 13.2.4 Hydrographic study and boundary conditions 119 13.3 Calibration of the ZWENDL model 125 13.3.1 Introduction 125 st 13.3.2 Calibration February 1 2002 period 126 13.3.3 Conclusion 131 13.4 Scenarios 131 13.4.1 Methodology 131 13.4.2 Simulations with different (outside) surge levels and river discharge 133 13.4.3 Simulations with different local wind surge levels 134 13.4.4 Analyses of the water levels and the prediction spreadsheet 135 13.5 Conclusions and recommendations 139 13.5.1 Conclusions 139 13.5.2 Recommendations 141 14 FORECAST SYSTEM & EARLY WARNING RESPONSE 143 14.1 Forecast system 143 14.1.1 Introduction 143 14.1.2 Development of transfer functions 143 14.1.3 Flood warnings 144 14.1.4 Trigger criteria 145 14.1.5 Fluvial Flood Warnings 146 14.1.6 Triton User Interface 147 14.1.7 User Manual and System Training 148 14.1.8 Future monitoring requirements 148 14.2 Early Warning System 149 14.2.1 The Components of an Early Warning System 149 Dublin Coastal Flooding Protection Project 9M2793 Final Report 29 April 2005 14.2.2 Requirements for Study Area 151 14.2.3 Option for the Development of an Early Warning System 152 14.2.4 Fluvial Considerations 154 14.2.5 Links to ERP and MEP 154 14.2.6 Strategic Recommendations 154 14.2.7 Work required 155 15 FLOOD HAZARD IDENTIFICATION AND FLOOD RISK DETERMINATION 156 15.1 Introduction 156 15.2 Flood Compartments 156 15.2.1 Methodology and Information Available 156 15.2.2 Identification of Low Lying Topographic Compartments 158 15.3 Drainage Considerations 161 15.3.1 General 161 15.3.2 Overview of Dublin Drainage System 161 15.3.3 Inspection of Outfalls Along Tidal Rivers 163 15.3.4 Issues Relevant to DCFPP 166 15.4 Detailed Assessment of Flood Hazard Areas 167 15.4.1 Methodology 167 15.4.2 Definition of Hazard Criteria and Design Parameters 168 15.4.3 Discussion on Results of Initial Flood Risk Analysis 178 15.4.4 Locations at Risk and Standard of Protection 181 15.4.5 Assessment of Potential Flood Damage Function 186 15.5 Flood Impacts and Assessment 187 15.5.1 Methodology 187 15.5.2 Damages as function of probability 187 16 STRATEGY AND POLICY FOR STUDY AREA 190 16.1 Introduction 190 16.1.1 Background 190 16.1.2 Process for Defining Policy and Strategy 190 16.2 The Business Drivers 191 16.2.1 The Statutory and Legal Context 191 16.2.2 The Geographical Context 192 16.2.3 Time Frame 192 16.3 Review of Key Documents 192 16.3.1 International References 192 16.3.2 Irish Flood Review Group Recommendations 199 16.3.3 Policy Areas 199 16.4 Present Practice and Aspirations 200 16.4.1 Consultation 200 16.4.2 Forum and Workshop 202 16.5 Policies and Strategies in Place 202 16.5.1 Emergency Response 202 16.5.2 GDSDS Policies 203 16.6 Summary of Present Practice and Aspirations 207 16.7 Dublin‟s Needs 214 16.8 Recommendations for Policy 215 16.8.1 Preamble 215 16.8.2 Recommendations 215 Dublin Coastal Flooding Protection Project 9M2793 Final Report 29 April 2005 17 FLOOD ALLEVIATION OPTIONS 225 17.1 Introduction 225 17.1.1 General 225 17.1.2 Other Projects 225 17.1.3 Assessment Criteria 226 17.2 Principal Findings of Asset Database and Emergency Works Report 227 17.2.1 General 227 17.2.2 Identification of Database Actions and Urgent Works 228 17.3 FINGAL COUNTY COUNCIL AREA.