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Eastern CFRAM Study HA09 Inception Report

IBE0600Rp0008_F02/Aug2012

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Eastern CFRAM Study

HA09 Inception Report

DOCUMENT CONTROL SHEET

Client OPW

Project Title Eastern CFRAM Study

Document Title IBE0600Rp0008_HA09 Inception Report_F02

Document No. IBE0600Rp0008

DCS TOC Text List of Tables List of Figures No. of This Document Appendices Comprises 1 1 144 1 1 5

Rev. Status Author(s) Reviewed By Approved By Office of Origin Issue Date

D01 Preliminary Various M Brian G Glasgow Belfast Internal Feb 2012 D02 Draft Various M Brian G Glasgow Belfast Mar 2012

F01 Draft Final Various M Brian G Glasgow Belfast July 2012

F02 Final Various M Brian G Glasgow Belfast Aug 2012

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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 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.

Eastern CFRAM Study HA09 Inception Report – FINAL

TABLE OF CONTENTS

1 INTRODUCTION ...... 1 1.1 OBJECTIVE OF THIS INCEPTION REPORT ...... 3 1.1.1 Hydrometric Area 09 ...... 3 1.1.2 Dodder CFRAM Study and Tolka Flood Study ...... 3 1.2 APPROACH TO PROJECT DELIVERY ...... 4 2 DATA COLLECTION ...... 5 2.1 DATA COLLECTION PROCESS ...... 5 2.1.1 Hydrometric Area 09 ...... 5 2.1.2 Dodder CFRAM Study and Tolka Flood Study ...... 11 2.2 DATA MANAGEMENT AND REGISTRATION ...... 12 2.3 DATA REVIEW – HYDROMETRIC AREA 09 ...... 12 2.3.1 Flood Relief / Risk Management Measures ...... 12 2.3.2 Historical Flood Data ...... 25 2.3.3 Baseline Mapping ...... 25 2.3.4 Hydrometric Data ...... 25 2.3.5 Meteorological Data ...... 26 2.3.6 Land Use Data...... 26 2.3.7 Planning and Development Information ...... 26 2.3.8 Environmental Data ...... 30 2.3.9 Soil and Geological Data ...... 32 2.3.10 Defence and Coastal Protection Asset Data ...... 32 2.3.11 Greater Strategic Drainage Study (GDSDS) Data ...... 34 2.4 DATA REVIEW – DODDER CFRAM STUDY AND TOLKA FLOOD STUDY ...... 38 2.4.1 Dodder CFRAM Study ...... 38 2.4.2 Tolka Flood Study ...... 40 2.5 DATA OUTSTANDING ...... 40 2.5.1 Hydrometric Area 09 ...... 40 2.5.2 Dodder CFRAM Study and Tolka Flood Study ...... 41 2.6 DATA GAPS ...... 42 2.6.1 Hydrometric Area 09 ...... 42 2.6.2 Dodder CFRAM Study and Tolka Flood Study ...... 43 2.7 CONCLUSION ...... 44 3 SURVEYS ...... 45 3.1 CHANNEL & CROSS-SECTION SURVEYS ...... 45 3.2 FLOOD DEFENCE ASSETS ...... 45 3.3 FLOODPLAIN SURVEY ...... 45

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3.4 PROPERTY SURVEY ...... 46 4 PRELIMINARY HYDROLOGICAL ASSESSMENT AND METHOD STATEMENT ...... 48 4.1 HYDROMETRIC DATA ...... 48 4.1.1 Hydrometric data – HA09 ...... 48 4.2 METEOROLOGICAL DATA ...... 62 4.2.1 Daily rainfall data ...... 62 4.2.2 Hourly rainfall data ...... 64 4.2.3 Rainfall Radar Data ...... 66 4.3 HISTORICAL FLOOD EVENTS – SOURCES OF INFORMATION ...... 66 4.3.1 Hydrometric Data ...... 67 4.3.2 Historical Flood Events ...... 68 4.4 PRELIMINARY ASSESSMENT OF PAST FLOODS AND FLOODING MECHANISMS ...... 90 4.4.1 Past flooding history and selection of flood events ...... 90 4.4.2 Flood Mechanisms in HA09 ...... 91 4.4.3 Flood event behaviour and their frequency ...... 91 5 HYDROLOGICAL ANALYSIS METHOD STATEMENT ...... 98 5.1 ANALYSIS OF HYDROMETRIC AND METEOROLOGICAL DATA ...... 98 5.1.1 Gauging Station Rating Review ...... 98 5.1.2 Hydrometric Data ...... 98 5.1.3 Rainfall Data Analysis ...... 98 5.2 MODEL CONCEPTUALISATION ...... 99 5.2.1 HA09 Hydraulic Models ...... 99 5.2.2 Hydraulic Model Calibration ...... 101 5.3 HYDROLOGICAL ESTIMATION POINTS ...... 103 5.3.1 HEP Categories ...... 103 5.3.2 Catchment Boundaries ...... 104 5.4 ESTIMATION OF DESIGN FLOW PARAMETERS ...... 105 5.4.1 Design Flow Estimation ...... 105 5.4.2 Phase 1: Derivation of Growth Curves for HA09 – (Box 10) ...... 107 5.4.3 Phase 1: Calculation of Design Flows at HEPs ...... 107 5.4.4 Phase 2: Catchment Flow Calibration (Box 13 to 18) ...... 110 5.5 SUMMARY OF HEPS IN HA09 AND ASSOCIATED ANALYSIS ...... 112 5.6 DETAILS ON DIFFERENT HYDROLOGICAL MODELLING METHODS ...... 118 5.6.1 Rainfall Runoff Catchment Modelling – MIKE NAM ...... 118 5.6.2 Institute of Hydrology Report No. 124 ...... 127

5.6.3 Flood Studies Update (FSU) Qmed Estimation ...... 127 5.6.4 FSSR Unit Hydrograph Method ...... 128 6 DODDER CFRAM STUDY AND TOLKA FLOOD STUDY DETAILED METHODOLOGY REVIEW ...... 130 6.1 CONTRACT SPECIFIC METHODOLOGY – DODDER CFRAM STUDY ...... 130

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6.1.1 Phase 1: Hydrological Analysis, Hydraulic Modelling & Flood Mapping ...... 130 6.1.2 Phase 2: Flood Risk Management Options ...... 132 6.1.3 Phase 3: Flood Risk Management Plan ...... 133 6.2 CONTRACT SPECIFIC METHODOLOGY – TOLKA FLOOD STUDY ...... 133 6.2.1 Phase 1: Hydrological Analysis, Hydraulic Modelling & Flood Mapping ...... 133 6.2.2 Phase 2: Flood Risk Management Options ...... 136 6.2.3 Phase 3: Flood Risk Management Plan ...... 137 7 DETAILED METHODOLOGY REVIEW ...... 138 7.1 RISKS AND PROPOSED METHODOLOGY AMENDMENTS ...... 140 7.2 OPPORTUNITIES AND PROPOSED METHODOLOGY AMENDMENTS ...... 141 8 REFERENCES ...... 143

LIST OF FIGURES

Figure 1.1: HA09 Extents and AFA Locations ...... 2 Figure 2.1: GDSDS Rivers that are HPWs in HA09 ...... 35 Figure 3.1: Locations of Flood Defence Assets in HA09 ...... 47 Figure 4.1: Hydrometric Stations in HA09 ...... 53 Figure 4.2: Hydrometric Stations along Modelled Watercourses (HPW / MPW) ...... 55 Figure 4.3: Hydrometric Stations for CFRAM Study rating review in HA09 ...... 57 Figure 4.4: Location of Daily Rainfall Gauges ...... 64 Figure 4.5: Hourly Rainfall Gauges ...... 65 Figure 4.6 Observed flood hydrograph during the November 2009 flood event at the hydrometric station of Ryewater River ...... 92 Figure 4.7 Observed Annual Maximum Flows for Ryewater River at Leixlip (Hydr. Stn. 09001) ... 92 Figure 4.8 Fitted EV1 frequency Curve to the observed AMAX records for Ryewater River at Leixlip (Hydr. Stn. 09001) ...... 93 Figure 4.9 Fitted GEV frequency curve to the observed AMAX records for Ryewater River at Leixlip (Hydr. Stn. 09001) ...... 93 Figure 4.10 Lognormal (2-parameter) frequency curve to the observed AMAX records Ryewater River at Leixlip (Hydr. Stn. 09001) ...... 93 Figure 5.1: HA09 Conceptualised Models ...... 100 Figure 5.2: Two Phased Hydrology Analysis Process Chart ...... 106 Figure 5.3: NAM model structure (SWRBD/RPS, Reference 27) ...... 118 Figure 5.4: Available GIS datasets for deriving the NAM model parameters in HA09 ...... 123 Figure 5.5: Visualization tools for the NAM model calibration component...... 126

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LIST OF TABLES Table 2.1: Summary of reviewed reports ...... 16 Table 2.2: Preliminary List of Environmental Datasets ...... 30 Table 2.3: GDSDS GIS Layers available within HA09 ...... 37 Table 2.4: Summary of Data Quality and Validity Checks ...... 42 Table 3.1: Flood Defence Assets Identified in HA09 Survey Specification...... 45 Table 4.1: OPW Hydrometric Stations with available data within HA09 ...... 48 Table 4.2: Local Authority (EPA) and ESB Hydrometric Stations with Available Data in HA09 ...... 48 Table 4.3: Final Station Rating Quality Classification ...... 50 Table 4.4: Existing Rating Quality Classification for Rating Review Stations in HA09 ...... 56 Table 4.5: Number Summary – HA09 Stations with Data Available ...... 58 Table 4.6: Summary of Hydrometric Data Provision within HA09 ...... 59 Table 4.7: Number of Available Daily Rainfall Stations ...... 62 Table 4.8: Summary of Historical Flood Events for each AFA ...... 69 Table 4.9: Flow Data Availability for Gauges on Watercourses to be Modelled in HA09 ...... 90 Table 4.10: Significant flood events, their generation mechanisms and frequency HA09 ...... 95 Table 5.1: Selected Flood Events for Hydraulic Model Calibration and Verification ...... 101 Table 5.2: Summary of Hydrology Analysis per HEP and Model Number ...... 112 Table 5.3: Example decision table for the determination of the NAM surface storage zone (Umax), (SWRBD, RPS, 2008) ...... 121

APPENDICES

APPENDIX A HYDROMETRIC DATA STATUS TABLE APPENDIX B DAILY AND HOURLY RAINFALL DATA STATUS TABLES APPENDIX C RAINFALL RADAR DATA ANALYSIS TO PROVIDE INPUT TO HYDROLOGICAL MODELS APPENDIX D HYDROLOGY METHOD PROCESS CHART – USED DATASETS TABLE APPENDIX E HEP AND CATCHMENT DIAGRAMS

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1 INTRODUCTION

The Office of Public Works (OPW) commissioned RPS to undertake the Eastern Catchment Flood Risk Assessment and Management Study (Eastern CFRAM Study) in June 2011. The Eastern CFRAM Study was the second catchment flood risk management study to be commissioned in Ireland under the EC Directive on the Assessment and Management of Flood Risks (Reference 1) as implemented in Ireland by SI 122 of 2010 European Communities (Assessment and Management of Flood Risks) Regulations 2010 (Reference 2).

The Eastern CFRAM Study covers an area of approximately 6,250 km2 and includes four Units of Management, HA07 (Boyne), HA08 (Nanny–Delvin), HA09 (Liffey-) and HA10 (Avoca- Vartry). There is a high level of flood risk within the Eastern CFRAM Study area with significant coastal and fluvial flooding events having occurred in the past.

Hydrometric Area 09 covers an area of approximately 1,617 km2 and includes most of Dublin County including Dublin City, and parts of the Dun Laoghaire-Rathdown and Council areas and parts of Counties Meath, and Wicklow. HA09 is the most densely populated hydrometric area in Ireland with recent statistics (Central Statistics Office, Census of Population 2011) indicating circa 1.2 million people to reside within its boundary.

The principal river within HA09, is the which rises in the and flows initially westward towards Newbridge, then turns north east towards Lucan and finally flows eastward through Dublin City, discharging to Dublin Bay. There are a number of other lesser rivers within HA09 that discharge directly to Dublin Bay, these include the River and other smaller coastal watercourses.

HA09 is a relatively urbanised catchment in an Irish context, containing Greater Dublin and its surrounding commuter belt. There are significant towns and developments along the N4 and N7 national road corridors, including , and . However the upland portions of the catchment are rural in nature hosting agricultural, forestry and power generation land uses and the Wicklow Mountains National Park.

Within HA09 there are 16 discrete Areas for Further Assessment (AFA) in addition to Dublin City under the Eastern CFRAM study as shown in Figure 1.1. Dublin City AFA is defined by four High Priority Watercourses (HPW), the Liffey, Camac, Poddle and Santry Rivers, that were specified by OPW. (Note and Santry AFAs are located on the Santry HPW).

The principal source of flood risk within HA09 is fluvial flooding at 12 of the 16 discrete AFAs (Lucan to , Leixlip, Maynooth, , Balldonnel, Celbridge, Hazelhatch, Turnings, , Naas, Newbridge and ). Tidal flood risk influences one discrete AFA (Sutton and North), with the other three discrete AFAs within HA09 (Sutton & , Clontarf and ) considered to have some element of combined fluvial/coastal flood risk. Dublin City with its specified

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HPWs is also subject to combined fluvial/tidal flood risk however the finalisation of watercourses within the Dublin area to be included in the Eastern CFRAM Study is ongoing at the time of writing.

Figure 1.1: HA09 Extents and AFA Locations

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For HA09, the CFRAM brief requirements include the need to review and ultimately incorporate the outputs from three previous smaller scale CFRAM studies for the Dodder and Tolka River catchments and the Fingal East-Meath area (FEM FRAMS). Each section of this report initially relates to the HA09 Study Area excluding the Dodder CFRAM Study, Tolka Flood Study and FEM FRAMS areas. The Dodder CFRAM Study and Tolka Flood Study areas are addressed, where relevant, in separate sub-sections. The FEM FRAMS only covered a very small area in the north east corner of HA09 and as such is not discussed directly in this document, however the relevant findings of the FEM FRAMS will be incorporated at the appropriate stages of the Eastern CFRAM study.

1.1 OBJECTIVE OF THIS INCEPTION REPORT

1.1.1 Hydrometric Area 09

The principal objective of this Inception Report is to provide detail on the relevant datasets identified for use in HA09 as part of the Eastern CFRAM Study, and provide an update on the collection and interpretation process to date (January 2012) for that data.

This document will also identify any issues that have been encountered in sourcing data and flag any that may affect the proposed methodologies or programme going forward.

The data requested, received or outstanding is detailed in the following section of this document, and progress with analysis of this data in current work packages is presented in Section 4.

1.1.2 Dodder CFRAM Study and Tolka Flood Study

The Dodder Catchment Flood Risk Assessment and Management Study (Dodder CFRAM) is presently out to public consultation and lies entirely within Unit of Management HA09.

The Tolka Flood Study was completed by RPS in 2003. In 2010, RPS was re-appointed by to upgrade the Tolka Flood Study mapping to CFRAM Study standards. This involved the production of the 200-year tidal and 1000-year fluvial flooding mapping for the Tolka catchment area principally to assist Fingal, Meath and Dublin City Councils in the preparation of their draft development plans.

A specific objective of this Inception Report is to provide a detailed method statement for undertaking a review of the Dodder CFRAM Study and Tolka Flood Study to thus fulfil the requirements of Section 2.6 of the Eastern CFRAM Study Contract-Specific Project Brief. This objective will be met through the following phases:

• Phase 1: Review of the hydrological analysis, hydraulic modelling and flood mapping for each study.

• Phase 2: Review of the recommended flood risk management options for each study.

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• Phase 3: Incorporating the findings, recommendations and proposed measures into the overall Eastern CFRAM Study Flood Risk Management Plan.

This document will also identify any issues that have been encountered in sourcing data and flag any that may affect the proposed methodologies or programme going forward.

1.2 APPROACH TO PROJECT DELIVERY

RPS has established a project specific team for the Eastern CFRAM Study which includes a Project Management Board consisting of our nominated Project Director, Dr Alan Barr, assisted by the Project Manager, Grace Glasgow, and two Assistant Project Managers, Dr Malcolm Brian and Andrew Jackson. This senior management team are closely involved in all aspects of the study and will have responsibility for specific technical and geographic areas. All members of the RPS Project Board are based in the Belfast office of RPS as are many of the supporting technical staff, although the overall team includes staff from RPS offices in Dublin, Limerick, Cork and Galway as well as support from sub-consultants Compass Informatics and Hydrologic BV.

Within the overall RPS project team are a core group of staff who will remain involved in the project throughout its duration from initial data collection to reporting to ensure coherence and consistency in approach. Within this group we have identified a dedicated data manager, Stephen Neill, who is responsible for ensuring that all received data is logged and for maintaining a project specific inventory of datasets available to the project.

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2 DATA COLLECTION

2.1 DATA COLLECTION PROCESS

2.1.1 Hydrometric Area 09

RPS places a high importance on data collection throughout the lifetime of a project and considers sourcing, acquisition, quality checking and updating of information to be critical to the successful implementation of the CFRAM Studies.

The data collection process for the Eastern CFRAM Study and HA09 in particular started with a review of the lists of data sources and relevant reports identified in the “National Flood Risk Assessment and Management Programme, Eastern River Basin District Catchment-based Flood Risk Assessment and Management (CFRAM) Study, Stage II Tender Documents: Project Brief” (Reference 3), hereinafter referred to as the Eastern CFRAM Study Brief and the “National Flood Risk Assessment and Management Programme, Catchment-based Flood Risk Assessment and Management (CFRAM) Studies, Stage I Tender Documents: Project Brief” (Reference 4), hereinafter referred to as the Generic CFRAM Study Brief followed by tailored requests to probable data holders including all steering and progress group members.

The formal data collection process for the Eastern CFRAM Study was initiated by OPW providing RPS with a range of datasets in various formats, including data from various Local Authorities and other organisations at the start of June 2011. The datasets provided by OPW included:-

Social o Primary Schools, Post Primary Schools, Third Level o Fire Stations o Garda Stations o Civil Defence o OPW Buildings o Nursing Homes, Hospitals, Health Centres

Economic o Geo-Directory (GeoDirectory Oct 2010) o Infrastructure: ESB Power Stations, ESB HV Substations, Bord Gais Assets, Eircom Assets o Road o Rail o Ports o Airports

Environmental o Architectural Heritage o National Monuments o National Heritage Area o Proposed National Heritage Area o Special Area of Conservation o Special Protected Area

IBE0600Rp0008 5 Rev F02 Eastern CFRAM Study HA09 Inception Report – FINAL o Groundwater Drinking Water (EPA data) o Pollution Sources (EPA data)

Hydrology o Irish Coastal Protection Strategy Study: North East coast o Irish Coastal Protection Strategy Study: South East coast o FSU data o OPW Hydrometrics: Annual Maxima, Gaugings, Q 15min Data, Rating Equations, Staff Gauges Zero, WL 15min Data, Photographs o EPA Water levels

Meteorology o Rainfall logger (24hr storage). Daily gauges. (Met Éireann/Data files/Rainfall/Daily Rainfall) o Rainfall logger (hourly). Synoptic Stations. (Met Éireann/Data files/Rainfall/Hourly Rainfall) o Evaporation Data. Synoptic Stations (Met Éireann/Data files/Evaporation) o Pot Evapotranspiration. Synoptic Stations (Met Éireann/Data files/Pot Evapotransipiration) o Soil Moisture Defective. Synoptic Stations (Met Éireann/Data files/SMD) o Air Pressure o Temperature o Wind Speed and Direction o Soil temperature o Rainfall Radar o Met Éireann Spatial files

Geo-referenced Data o Development and Local Area Plans o Historical Flood data o NDHM (5m resolution IfSAR) o hDTM (20m resolution hydrologically corrected DTM) (EPA-20m hDTM/Disc 2-Eastern RBD) o OSi Maps o LiDAR o Aerial photography o OPW Channels o OPW Embankments o OPW Benefiting Lands o Lakes (Lakes/HA_09) o River Centrelines

Other o PFRA Access Database (110310_Final Database) o floodmaps.ie Registered User log in details o Contact list of Data Owners o National Pluvial Screening Project for Ireland report o PFRA Groundwater Flooding report o PFRA Tables o Defence Asset Database o Operation Instructions for Flood Defences, Hydraulic Structures o Existing Survey Data from existing studies o Existing Studies Models and Reports o Existing Low Flow/ Water Quality Studies Models and Reports o Greater Dublin Strategic Drainage Study o Tolka information o Dodder information o FEMFRAM information

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Following an initial review of the received data, further requests were made to the appropriate Local Authorities and other organisations via email and also at meetings, either at their offices or at the various project meetings. A summary of the range of data requests made by RPS between June and February 2012 is provided below. In addition to requesting data from Local and Central Government agencies RPS also undertook internet searches to source further data in specific areas.

Immediately upon confirmation of appointment in June 2011, RPS requested hydrometric data, levels and flows for all Environmental Protection Agency (EPA) gauging stations and all Electricity Supply Board (ESB) gauging stations within the study area. Details of rating equations and calibration measurements for these stations were also sought from EPA and ESB. Also at the project outset, a data request was issued to ESB following an introductory meeting held on 24th June 2011. A range of reports were provided pertaining to Liffey Hydrology as follows: o 1986 Flood o Leixlip Inundation Study o Liffey Flood Warning o Water Extraction River Liffey o Root Selection Methods in Flood Analysis o Flood Control and Dam Safety o Leixlip Treatment Plant o National Hydrology Seminar – Flood Risk Management o Regulations and Guidelines for the Control of the River Liffey

At the beginning of July, RPS issued a request to all relevant Local Authorities seeking details of culverted watercourses, storm sewer systems and discharges and any flood defence schemes in GIS or AutoCAD format. A request was also submitted to OPW seeking:

• Re-supply of the National Digital Height Model data as the original information was for the wrong area;

• Details of the number of affected properties per AFA for each Annual Exceedance Probability (AEP) as identified through the Preliminary Flood Risk Assessment (PFRA) process;

In mid August, requests were made to GSI for soil and groundwater datasets to inform the MIKE-NAM model parameters decision trees and derive model input parameters. The actual datasets requested were:

• Groundwater Vulnerability;

• Soil Permeability;

• Well Drained / Poorly Drained Soils;

• Aquifer Type.

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Towards the end of August, RPS requested supply of copies of any feasibility study reports or design reports / drawings that OPW held for all of the schemes listed in the tender documents.

At the end of September a request was issued to Dublin City Council to obtain any information including Reports / studies undertaken as a pre-cursor to flood relief schemes for Minor works in 2008 in Chapelizod, DCC Works in South Docklands, Dublin Coastal Flooding Protection Project: Resulting Schemes.

At the start of October, RPS issued a request to all of the Local Authorities asking them to review the list of rainfall gauging stations within their administrative areas and advise RPS regarding:

1. Whether they were aware of additional stations to those listed; and

2. If so, to provide:

a. Station name;

b. Location (coordinates);

c. Type – daily / hourly;

d. All available data.

Any aerial photography of flooding held by the Local Authorities was also requested at this time.

A request was also issued to Met Éireann for some missing rainfall data from the meteorological stations in the study area that had been identified through a review of the previously supplied data. South Dublin County Council was also contacted for any Flood Relief Schemes reports that they had available.

In the middle of October, RPS issued a request to Teagasc for any rainfall data they hold while at the end of October, RPS requested missing OSi vector mapping data from OPW. RPS also requested further information from South Dublin County Council for additional rain gauge data via EPS Ireland (sub contractors managing rain gauges for South Dublin County Council).

Details of the locations of all ground based Electrical infrastructure was requested from ESB Ireland at the beginning of November 2011.

Finally, at the beginning of December, RPS sent a request to Dublin City Council to obtain any LiDAR data which they had and also spatial data for a number of Hydrometric Stations and a final request to each Local Authority for the following information:

Flood Relief/Risk Management Measures

• Previous reports or studies concerning flood hazard or risk or possible flood relief measures;

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• Information on current flood risk and water management measures or practices;

• Information on other flood-related matters undertaken under other national programmes or other EU directives.

Historic Flood Data

• Information on historic flooding;

• Maps of flood extents;

• Flood levels;

• Flood depths;

• Causes or mechanisms of flooding;

• Resulting damage.

Hydrometric Data

• Information on recorded water levels and tidal data, flows, flow gaugings and ratings (stage- discharge relationships).

Meteorological Data

• Information on rainfall, air pressure, wind speed and direction, temperature and evapotranspiration.

Land-use Data

• Information on current and past land use.

Soil and Geological Data

• Data on soil classifications, sub-soils, geology and aquifers.

Planning and Development Information

• Information concerning existing development and possible future development;

• Local area plans, town plans, master plans.

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Defence and Coastal Protection Asset Data

• Information in relation to the location, type, ownership, design and/or actual performance standard, and condition of these assets.

Existing Survey / Geotechnical Data

• Topographical, channel, structural or geotechnical survey data collected for previous flood relief studies or other construction projects e.g. main drainage or sewer projects.

Environmental Data

• Information, reports, studies, zoning or assessments of environmental and archaeological status, issues, constraints and impacts.

Other Receptor Data

• Data on flood risk receptors, including types and locations such as property types, utility and transport infrastructure, national monuments and protected structures, hospitals, schools etc.

Urban Drainage

• Culverted Watercourse - extents / locations / inlets and outlets;

• Diverted Watercourses;

• Outfalls;

• Storm Water Infrastructure Records.

Other

• Aerial photography of flooding.

This request was implemented by forwarding to each Local Authority a tailored document which stated the Eastern CFRAM study data requirements and also the data currently held for their area. In this request, Local Authorities were asked to either forward any other relevant data they held in relation to each of the data requirement headings or confirm that they had no further information. This was classified as being the final data collection cut-off date for Local Authority data, however further to a request by the Eastern CFRAM Study progress group, this request was re-issued on 3rd February 2012.

Dunlaoghaire-Rathdown County Council provided a copy of their Coast Defence Strategy with photographs in response to this request. Dublin City Council also provided CCTV reports for Dublin City drainage networks, survey location maps and network layouts. Information on the Dodder Flood

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Alleviation Scheme, and development data was also provided as listed in Section 2.3. Development data was downloaded from www.dublinked.ie with access provided by Dublin City Council. This also enabled development data to be downloaded for South Dublin County Council and as listed in Section 2.3.7.

As RPS go through the various stages of the Eastern CFRAM study, further data needs may be identified and therefore the information will be requested and obtained.

In all cases every request for information was logged into the Data Request Register and followed up with further emails and phone calls as appropriate.

2.1.2 Dodder CFRAM Study and Tolka Flood Study

The Dodder CFRAM Study and Tolka Flood Study were carried out by RPS and therefore RPS has access to all associated data. RPS has completed an initial review of this data, and has made further requests to the appropriate Local Authorities where additional work has been completed or carried out.

On 07/02/12, RPS sent requests to Dublin City Council, South Dublin County Council and Dun Laoghaire Rathdown County Council for an update on any flood relief or risk management measures which have been implemented since the commencement of the Dodder CFRAM Study. At the time of drafting of this report DCC confirmed that works downstream of Lansdowne Road (Newbridge) were completed in 2010, works between Newbridge and the Irish Rail Bridge at Lansdowne are at the planning stages and works to raise Newbridge and London Bridge are at the planning stages also. Works from Irish Rail Bridge to the Hotel Bridge are at tender stage for a consultant to carry out the detailed design. SDCC confirmed that there are no flood relief or risk management measures being implemented within their area.

On 02/03/12, RPS sent requests to Dublin City Council, Meath County Council and Fingal County Council for an update on any flood relief or risk management measures which have been implemented since the commencement of the Tolka Flood Study. Meath County Council and Dublin City Council stated that all of the recommendations of the Tolka Flood Study have been carried out. Fingal County Council stated all of the measures recommended by the study have been implemented with the exception of:

• The removal of Bridge (a has been constructed with the existing bridge remaining in place);

• Increasing the capacity of culverts on the Pinkeen.

Every request for information is logged in the Data Request Register and is followed up with further emails and phone calls as appropriate.

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2.2 DATA MANAGEMENT AND REGISTRATION

When data is received by RPS, it is transferred from the medium supplied into a temporary Incoming Data Folder. Any spatial data that is not provided in ESRI ArcMap format is converted using a piece of Safe Software called FME (Feature Manipulation Engine). A File Geodatabase is then created and the translated feature classes are imported into it, where they are named appropriately using the convention of (Owner, Dataset Name, Spatial Type, Date received) e.g. OPW_HA09_Rivers_pl_110602, and the correct spatial reference is attached. These datasets are then imported to ArcMap to verify the positional accuracy against OSi background mapping.

All spatial and non-spatial information details are recorded into the Incoming Data Register. This register records the date of receipt, issuing organisation, supplier contact, data owner, filename as received, renamed filename, category, work package, description, original data format, new data format, type, medium, metadata, hyperlink, hydrological area, data requirement. Once receipt has been recorded and the data has been re-processed as necessary, the spatial and non-spatial datasets are moved to the appropriate folder location on our dedicated data server i.e. spatial data is moved to the folder ‘6.0 Spatial data’, non-spatial is moved to the folder ‘8.2 Data Collection’. Data which is specific to a particular work package is moved into the relevant work package folder, for example, hydrometric data is moved to the ‘8.5 Hydrology WP’ folder.

2.3 DATA REVIEW – HYDROMETRIC AREA 09

2.3.1 Flood Relief / Risk Management Measures

Following a number of data requests as outlined in Section 2.1 RPS has received details of a number of existing flood relief and management measures within HA09.

South Dublin County Council:

• Camac Flood Report - June 1993 • Camac Flood Works 1 River Improvement Scheme - 1993 • Camac Flooding Photos - June 2000 • Camac Report - Nov 1995 • Camac Photos - April 1998 • Griffeen Flood Review - Section 5 Hec-Ras Hydraulic Model - Nov 2000 • Griffeen Flood Review - Appendix 1 - 2 - Nov 2000 • Griffeen Flood Review - Appendix 3 - 4 - Nov 2000 • Griffeen Flood Review - Appendix 5 Met Office Data - Nov 2000 • Griffeen Flood Review - Appendix 6-9 - Nov 2000 • Griffeen Flood Review - Flood Event November 2000 • Kilnamanagh Stream - Brief Report and Photography Survey - 1996 • Kilnamanagh Stream - Photographs - 1996 • - Delph Centre Ltd Robinhood - Flooding - July 2003

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• National Hydrology Seminar - Camac Case Study - Sean Murray 2000.pdf • Flooding Dodder Valley Sewer White Church Stream Ballycullen Stream - 05-09-08 • South Dublin Rain Gauge Locations Existing and Proposed • Camac Logger Location • Griffeen Logger Location • Owendoher Logger Location • Poddle Logger Location • Poddle Flooding Report From Residents_111128

Dublin City Council:

• North City Water Supply Scheme and Clontarf Flood Defence • South Campshires Flood Defence Project • Tide Gate • North_Fringe_Water_Supply_Scheme[2] • Minor works in 2008 in Chapelizod • Maps_ InfrastructureLocationMaps - Infrastructure Location Maps • Re-lining_McCallisterBros_H&S Information I - Relining of Existing combined sewer in Chapelizod at Martins Row Phase 1 - McCallister Bros - Information for Health and Safety File • 3.Report_Nicholas O'Dwyer H&S Information - Chapelizod Village Improvement Scheme and upgrading of Sewerage Systems - Nicholas O'Dwyer - Information for Health and Safety File • Dublin SAFER Flood Atlas Volume 1 Coastal and Estuarine Flood Hazard Maps - Flood hazard Maps - Hard Copy • SAFER - Strategies and Actions for Flood Emergency Risk Management - Leaflet of information - Hard Copy • Flood Emergency Management in Dublin City Behind the Paradigm - DVD - DVD - DVD • AssetData_2 - Various Photographs - linked to a Database - jpeg • Dodder Outfalls - Various Photographs - linked to a Database - jpeg • ESB Survey 2004 - Various Photographs - linked to a Database - jpeg • Liffey Boardwalks - Various Photographs - linked to a Database - jpeg • Liffey Outfalls - Various Photographs - linked to a Database - jpeg • O5 Appendices a4_B&W.doc - Standard Protection Maps - List of Drawings - Word • O5 SoP 01.pdf - Standard Protection Maps - MERRION STRAND TO - Pdf • O5 SoP 01 Sandymount Figure- Standard Protection Maps Sandymount Ringsend • O5 SoP 02 South Figure - Standard Protection Maps South Dublin Port - Pdf • O5 SoP 03 North Dublin Port Figure - Standard Protection Maps North Dublin Port - Pdf • O5 SoP 04 Clontarf Figure - Standard Protection Maps Clontarf - Pdf • O5 SoP 05 North Howth Figure - Standard Protection Maps North Howth - Pdf • O5 SoP 06 Sutton South Howth Figure - Standard Protection Maps Sutton South Howth - Pdf • O5 SoP 07 Baldoyle Figure - Standard Protection Maps Baldoyle - Pdf • O5 SoP 08 Figure - Standard Protection Maps Portmarnock - Pdf • O5 SoP 09_1 Lower Liffey Figure - Standard Protection Maps River Liffey Lower & Upper - Pdf • O5 SoP 10 Figure - Standard Protection Maps River Dodder - Pdf • O5 SoP 11 Figure - Standard Protection Maps River Tolka - Pdf • O5 SoP 12 Figure - Standard Protection Maps Royal Canal - Pdf • setup - Setup for Database - exe • SeaDefence.mdb - Database File - Access • SeaDefence_Data.mdb - Database File - Access • DCC Database User Manual.doc - User Guide for Database - Word • South Campshire Flood Protection Project, George's Quay, City Quay and Sir John Rogerson's Quay, Dublin 2 Environmental Impact Statement V1 of 4 Non-Technical Report

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• Sutton to Phase One and Two • DCC_Clontarf Flood Defence - Webpage Content • DCC_DollymountPromenadeAndFloodProtectionProject-Webpage Content.doc • DCC_SandymountPromenadeAndFloodProtectionProject - Webpage Content.doc • GDSDS, F001,GDSDS F003,GDSDS F004,GDSDS F005,GDSDS S1001,GDSDS S1002,GDSDS S1003,GDSDS S1004,GDSDS S1005,GDSDS S2001,GDSDS S2008a,GDSDS S2008b,GDSDS S2012,GDSDS S20015 • River Dodder FAS – Bridges • River Dodder FAS - Fitzwilliam Quay • River Dodder FAS - Phase 2etc • Poddle Overflow 4"x4" Culvert - Whitehall - Rathdown Park • Taking In Charge Scheme - Manor, Whitehall Road

Fingal County Council

• Bloody Stream Investigation "Part 1 Investigations and recommendations for flooding within Techrete Yard.Part 2 - Investigations into Flooding of the Howth Road at Bloody Stream Pub" • Complete Howth Flood Study - Howth Flood Study Preliminary Review Report • SK0001_DublinBay Flood Relief Scheme Map Illustrating Foul & Surface Water Network

Wicklow County Council:

• OPW minor works allocation list 2011; • OPW coastal and non-coastal approved projects list 2010; • OPW list of funding allocations coastal and non-coastal 2009; • OPW drainage channels and drainage channel schemes; • OPW drainage districts. • Blessington Flood Data.pdf; (Data - 100 YR & 1000 yr Flooding Outlines Blessington) • Glending Flooding 2008 Maps.pdf. (Remedial Work at Glending Housing NAAS Road Blessington) • Photos of Flooding Aug 2008 - Flooding Photographs

Kildare County Council

• Kildare Co Co Flood Relief Schemes (pdf’s and hard copy): o Flood Relief Scheme o Kildare Housing at Newbridge, Catchment Study of Mooneys and Sexes Streams (DBFL Consulting Civil & Structural Engineers) (hard copy) o Flood Alleviation Scheme - 10-011-200 to 222 rev T1A (series of pdf’s) o Ardclough Flood Alleviation Scheme - 10-011-201_rev T1A o Ardclough Flood Alleviation Scheme - 10-011-202 T2 Site Layout 1 - 3 o Butterstream Flood Alleviation Scheme - 082201 Butterstream Phase 3 o Butterstream Flood Alleviation Scheme - 082201 Clane Tender Drawings o Johnstown Flood Alleviation Scheme - Johnstown Flood Relief Study – Preliminary o Johnstown Flood Alleviation Scheme - JB Barry Report_Kill & Johnstown o Johnstown Flood Alleviation Scheme - 208-027-801 to 811 o Morrell River - N7 Hydraulic Model & Flood Alleviation Measures Report o Morrell River - Scanned B&W Drawings 2010 o Newtown - Bar Schedule Headwall 1 - 3 o Newtown - Bar schedule Manhole S11 o Newtown - Bar schedule Manhole S12

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o Newtown - OBA1007-C-002 Existing Services (Sheet 1 - 2) o Newtown - OBA1007-C-004 Proposed Surface Water Drainage Layout (Sheet 1 - 2) o Newtown - OBA1007-C-006 Proposed Surface Water Drainage Longsections o Newtown - OBA1007-C-007 Works to Maher Lands o Newtown -OBA1007-C-008 Underpinning Details to Maher House o Newtown -OBA1007-C-009-C1 o Newtown -OBA1007-C-010 General & RC Headwall Details o Newtown -OBA1007-C-011 Manhole General Arrangement Details o Newtown -OBA1007-C-012 Manhole RC Details o Newtown -OBA1007-C-013 Works to Dillon Lands o Newtown -OBA1007-C-014 Topographical Survey (Sheet 1 - 2) o Newtown -OBA1007-C-016 - Trial Pit Record o Newtown -OBA1007-C-017-AC1 Wayleave o 092-375-110_CN1_SallinsReliefPhase1_CulvertPlan o 092-375-111 CN1_SallinsReliefPhase1_StreamCulvertElevationDetails o 092-375-201_SallinsReliefPhase1_Proposed FloodAlleviationWorks_Sheet1 o 092-375-205_SallinReliefPhase1_Access ChamberDetails o 102125 Sallins_BookNo2 TenderDrawingsAndSchedules208-042-S50-00_A1 o 208-042-S50-01_A2 o 208-042-S50-02_A2 o 208-042-S50-03_A2 o 208-042-S50-04_A2 o 208-042-S50-05_A2 o 208-042-S50-06_A2 o Trash Screen Details o 208-042-S50-00_A1CellbridgeFloodReliefPhase1_ProjectOverviewMap o 208-042-S50-01_A2CellbridgeFloodReliefPhase1_OldtownChannelUpgradeWorks o 208-042-S50-02_A2ToniRiverFloodReliefPhase1_VanessaLawnsChannelUpgrade o 208-042-S50-03_A2ToniRiverReliefPhase1_CellbridgeTownAFCChannelUpgrade o 208-042-S50-04_A2ToneRiverReliefPhase1_DaraCourtChannelUpgrade o 208-042-S50-05_A2ToniRiverReliefPhase1_DaraCresentMainStChannelUpgrade o 208-042-S50-06_A2ToniRiverReliefPhase1_MainStreetRiverLiffeyChannelUpgrade

All scheme and feasibility reports received by RPS were reviewed to identify relevant information for the purposes of this project. A summary of the various reports reviewed is provided in Table 2.1. The headings provide further information on; the area the report covers, the river associated with the report, the name of the report, who compiled the report, when it was produced as well as providing a brief summary of any recommendations contained within each report.

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Table 2.1: Summary of reviewed reports

Flood Relief River Name Report Name Author Date Recommendations Study Ardclough Ardclough Flood Alleviation Flood Stream each side Scheme. Volume A - Works Kilgallen & September Re-grading ditch levels, inserting culverts, cleaning ditches Alleviation of Requirements Book 1 – Partners 2011 Scheme Drawings Drawings. Flood Alleviation Works Butterstream (Phase DBFL Butterstream, August Construction of new culverts and upgrading of existing culverts Butterstream 2), Clane. For Tender, Consulting Clane 2010 as well as minor works. Volume A - Works Engineers Requirements (Book 1 of 2)

Drawings. Flood Alleviation DBFL Butterstream, Butterstream Works Butterstream (Phase Consulting July 2011 Construct a retaining wall and berm near Millicent Road Clane 3), Clane. For Tender Engineers

Chapelizod Village Improvement Scheme and Nicholas January Chapelizod Safety file information upgrading of existing O'Dwyer 2011 sewerage systems Relining of Existing Combined Sewer in McAllister Bros 10 March Chapelizod Safety file information. Outlines what the project was. Chapelizod at Martin's Row Ltd. 2010 (Phase 1) Report on Camac Flooding Provides further information on the flooding event of 1993 and Clondalkin Camac June 1993 11th - 12th June 1993 the levels the water reached over the course of the flood. Flood relief culvert and earth embankment. Improvement in Report on Camac River channel geometry downstream of the Newlands-Fonthill Road Improvement Scheme Phase September bridge to the Moyle Park Weir and the third measure is an Clondalkin Camac 1 Newlands - Fonthill Road 1993 upgrading and augmentation of the surface a water disposal to Nangor Road Clondalkin system at Leinster Terrace to eliminate the danger of the houses being flooded at that location.

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Flood Relief River Name Report Name Author Date Recommendations Study A long term programme for river control be initiated and that design of this programme be considered as a priority for South 28 Dublin County Council. The specification and implementation of Camac River Clondalkin Mark O'Reilly Clondalkin Camac November a routine maintenance programme is considered essential to South + Associates 1995 minimise the risk of flooding of the river. The provisions of storm overflow capacity though the Mill Shopping Centre is considered as an essential element in flood protection to Beech Row. June 2000 Clondalkin Camac Photos & April Photographs of flooding of the Camac River 1998 Recommended 2 phases from previous assessments. Phase 1 provided flood protection and flood alleviation for specific areas affected by the 1993 flood event. These works involved the construction of flood relief culverts and embankments, weir improvements, upgrading of surface water disposal systems and Sean Murray, the removal of an old factory weir. The Phase 1 works were South Dublin Clondalkin Camac National Hydrology Seminar 2000 completed in 1995 at a cost of £215,000. Phase 2 provided a County mechanism for the control of surface water volumes by means of Council attenuation ponds within . The volume required was determined to be 55,000m3 from computer simulation models using ‘RBM-DOGGS’ output to provide input for a ‘Hydroworks’ analysis. The works will go for tender in 2001 at an estimated cost of £560,000. Indicates a number of flooding events that have occurred at Dodder Valley Drainage houses due to various factors at each location. Trees contribute Sewer, White Drainage Maintenance Department 08 Areas within towards large amount of debris getting caught in various Church Stream & Section, Internal South Dublin September SDCC culverts. Additional information provided on flooding occurrences Ballycullen Memorandum County 2008 at a number of locations. This report mainly deals with drainage Stream Council of areas and the causes of flooding in these areas. Short-term measures: River monitoring, maintenance, move flow to new culvert beside Fossetts culvert, protect Fossetts Storage Report on flood event 5/6th compound, clean out and restore watercourse south of J B Barry and Griffeen River November 2000 in the River March 2001 Finnstown, clean + re-grade old forge/virtues ditch, developers Partners Griffeen Catchment proposals clarified for Kilmahuddrick Stream, increase link road culvert size, remove flow control structure on the Griffeen by the storage pond and clean and grade channel downstream of

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Flood Relief River Name Report Name Author Date Recommendations Study storage pond outlet, modify stormwater drainage, modify the river channel at the fish pass, consider removal/re-location of Esker Bridge, construct an earth embankment in Vesey Park, construct stormwater sewer in Lucan village, ensure no developments alter river channel. MEDIUM/LONG TERM MEASURES: increase storage pond capacity, consider additional storage upstream of the Railway Bridge, improve channel, increase capacity of two arch bridge, raise lake bank, install additional culvert under Adamstown Road and culvert/tunnel may be required to convey a revised 100 year flood flow through Lucan village. Problems exist due to (i) Unimproved sections, (ii) Improved sections but substandard, (iii) Potential additional problems due to piecemeal improvements. Twin arches at Road due to be upgraded as part of the improvements for Robinhood Design Kilnamanagh Stream brief Road. Proposed to culvert stream over 150m through council Section Ballymount Kilnamanagh report and photographic owned lands in the Greenhill's Industrial Estate. Section of Environmental June 1996 Road area Stream survey (Western Parkway to stream between Robinhood Road & Long Mile Road will also Services Naas Road) require substantial improvement. An alternative to upgrading the Department channel through Robinhood Industrial Estate would be to construct an entirely new channel/culvert from point G on Dwg. no. KILNA1 in a northerly direction to the Ballymount Stream adjacent to the 450mm foul sewer. Sabastien Visited the site on the day to check the recent improvements Dupuch during June & July 2003 (cleaning of important obstruction, Environmental removal of crossing pipe, realignment of bank). Improvement at Kilnamanagh The Delph Centre Ltd. Delph centre Services, July 2003 the Granyte Company pipe inlet and outlet indicated as a Stream flooding on the 17 July 2003 South Dublin priority. Flow at this area was reduced due to pallet blocking by County approx 2/3. Further discharge calculations in relation to the Council rainfall event were to be produced by SD (author). Recommends 4 phases: 1. Liffey Confluence to Old Morell N7 Naas Road Interchange Bridge. 2. Old Morell Bridge to Railway. 3. Railway and Canal. 4. Morell, Hartwell, J B Barry & Scheme. Hydraulic Model & January Canal to N7. : river channel needs enlarged, Kill, Painestown Partners Flood Alleviation Measures 2002 Culvert & sluice gate be provided. 5 No. 1.6m diameter pipe and Slane Rivers. Limited Report culverts to be pipe-jacked under the canal. Box culvert to be inserted at Morell Bridge. Construct an embankment. Insert box

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Flood Relief River Name Report Name Author Date Recommendations Study culvert under the railway track. Replace the road bridge at Killeenmore by one of greater capacity and higher soffit level. Raise bank levels. MORELL TRIBUTARY: Construct embankment and culvert. HARTWELL RIVER: Construct embankments and replace single arched bridge. KILL RIVER: replace local access bridge and construct an additional culvert at the double arched bridge. PAINESTOWN RIVER: Construct embankments. Repair partially collapsed bridge arch at Painestown Bridge. Raise bank levels. Allow farmland to flood. Pipe culverts to be implemented at Three Aqueducts Bridge, as well as ensuring up and downstream are large enough to ensure a smooth transition. Demolish existing embankments and construct engineering embankments at the railway to the road bridge. Replace Road Bridge with greater capacity. PAINESTOWN TRIBUTARY FROM GOFF'S/ /N7: construct embankments. Construct 2 300m long embankments. Pipe culvert under the proposed embankment. SLANE RIVER: Raise banks. Construct embankment. Increase pipe size at Confluence of local tributary (piped) and Slane. Additional culvert required at bridge at Deane's. Additional culvert required at Finger Post Bridge and Old Mill Bridge. PAINESTOWN TRIBUTARY FROM KILL: additional culvert to be laid under Kill-Bodenstown Road. FLOOD STORAGE BETWEEN CANAL AND RAILWAY: construct flood embankments and new drainage channel. Further information on these measures provided in section 7 of the report. These recommendations included in section 8 of the report. Attenuate all surface outfalls from the N7 and allow release at greenfield run-off. All culverts under N7 should accommodate the 1in100 yr flood. Attenuate surface water from new urban developments. Public consultation should occur with the local people to discuss the proposals. Following completion of the works KCC should: Ensure routine maintenance is carried out at least once a year, ensure no damage has occurred following significant flooding, no modifications have occurred by landowners and review and monitor the flood alleviation. Water levels and rain gauges should be recorded to ensure accurate

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Flood Relief River Name Report Name Author Date Recommendations Study models are produced. The MIKE 11 model should be updated after each significant flood event.

These recommendations should not be implemented until the recommendation within the January 2002 report are FULLY implemented. MORELL RIVER: Regrade and enlarge river channel. Additional box culvert required for Old Johnstown Bridge so that it is only used during high flows. Demolish Johnstown Manor Bridge and replace with 2 box culverts. Remove if possible the small bridge upstream of the Johnstown Manor Bridge. Replace 4 culverts under Fishery Lane. RACECOURSE DRAIN: Regrade river channel. FORENAUGHTS STREAM: Regrade stream channel. Replace footbridge near the village centre with new box culvert and pipe culvert. Replace culvert under Johnstown Gardens. Gabions will be required along specific areas of the route. Replace the culvert under the house access with a new box culvert. Replace pipe culvert under the entrance to ADM. Remove culvert at the bend. N7 Naas Road Widening & J B Barry & Replace culvert under the entrance to Boran Ltd. KILL RIVER: Kill & Kill & Morell Interchanges Scheme. Kill & Partners June 2002 Install additional culvert at double arched bridge under Johnstown Rivers Johnstown Flood Alleviation Limited O'Loughlin's Lane. Regrade channel. Replace bridge to Measures Report Whyndon Court with composite box and pipe culverts. New culvert to be constructed under Improvement. Install 2 additional culverts at Rathgorragh. Further information provided in section 6 of the report. Section 7 includes additional recommendations including: attenuate surface water outfalls from the N7, culverts under N7 should be sized to accommodate the 1in100yr flood and attenuate surface water from new developments. Public consultation day should be held. KCC should: ensure routine maintenance is carried out at least once a year, ensure no damage has occurred after significant flooding, no modifications have been made by landowners and the effectiveness of the flood alleviation scheme should be reviewed and monitored following a significant flood event. Water levels and rain gauge recorders are downloaded and accurate records maintained and stored.

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Flood Relief River Name Report Name Author Date Recommendations Study Morell, Hartwell, J B Barry & Drawings for the N7 Naas Kill, Painestown Partners July 2002 Drawings showing Flood Alleviation Proposals Road Interchange Scheme. and Slane Rivers. Limited Stone Arch Bridge: New culvert constructed as part of N7 however not used due to land acquisition difficulties, this should be used. Johnstown-Kill Road: Toberavoher Stream - Increase pipe size. Hartwell River - This channel is widened and the removed material used to raise the bank level nearest Johnstown. Johnstown Gardens: Widen the channel of Annagall Stream as well as upgrading the two culverts. St. John's Grove: Blockage removed and CCTV survey undertaken. Toberavoher Stream should also be regraded and maintained in this area. Furness Road and ESB Sub-station: channel along Furness Road is cleaned out and regraded from Equine Centre to ESB sub-station. Culvert under ESB sub-station entrance also Morell River, Kilgallen & ungraded. Culverts where the stream passes under the Furness Johnstown Annagall Stream, Partners Johnstown Flood Relief 25 June Road should also be upgraded. Johnstown Manor: Flood Flood Relief Toberavoher Consulting Study, Preliminary Report 2008 protection bund approx. 100m is constructed adjacent to this Study Stream and Engineers area and the channel of the river widened. Boran Plastics & Hartwell River LTD. ADM Distribution Ltd.: Channels & culverts in the vicinity of the site between the ESB sub-station and the ADM Distribution Ltd. site are upgraded, includes 2no. culverts on the channel & culvert at the entrance to the Boran Plastics site. Johnstown Conservatory Centre: Culvert increased in size and earthen bund constructed & that access track is raised to the top of this bund. Recommends outstanding measures recommended by JB Barry report in 2002 are implemented. Downstream works should be completed first. Fishery Lane: Morell River channel is regraded to ensure it can adequately pass under Fishery Lane through a new culvert. Culvert should cater for 1 in 100 year flood event. Morell River, Kilgallen & Johnstown Annagall Stream, Partners Johnstown Flood Relief 29 April Flood Relief Toberavoher Consulting Drawings of area and identify location of proposed works. Scheme 2009. Study Stream and Engineers Hartwell River LTD.

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Flood Relief River Name Report Name Author Date Recommendations Study Phase 1 of the project involved the restoration of Kerdiffstown Road. A new culvert was provided under Kerdiffstown Road together with a new outfall in the canal. Phase 2 was designed to upgrade the railway culvert and carry out any upstream works needed to cater for the future 100 year future flood with Flood PUNCH Sallins Flood Alleviation late 2009 allowance for climate change. The overall scheme required: 1. A Alleviation Consulting works early 2010 new culvert and outfall structure at the Grand Canal, 2. A new Works Engineers railway culvert and retention of the existing one, 3. Channel deepening/widening at certain locations, 4. Raising of bank levels generally to contain the design flood, and 5. Scour protection works to prevent erosion. Phase 2 works were being tendered. Sallins Flood PUNCH Sallins Flood Alleviation September Alleviation Consulting Contract Drawings for Phase 2 works. works Phase 2 2010 Works Engineers Aerial Photographs from to and from Ballymore Barrow_Liffey Flooding 03/11/2009 Eustace to and Kilcullen to Newbridge and Newbridge Event Photography to Sallins and Sallins and Cellbridge to Leixlip New flood protection system approx. 1km in length located on South Campshire Flood the southern campshires of the River Liffey. Prevent high tides South Protection Project, George's Moylan up to 3.7m above Malin Head datum. Appendix 10 contains Campshire Quay, City Quay & Sir John Liffey Consulting June 2011 report by Royal Haskoning relating to the Dublin Coastal Flood Rogerson's Quay, Dublin 2. Engineers Flooding Protection Project dated 29 April 2005. Appendix 14 Protection Environmental Impact contains the Grand Canal Harbour Area Flood Risk Assessment Statement prepared by DCC dated 22/03/11. Recommendations include: 2.5m.sq. Culvert to be placed beside existing culvert, improve river channel through the college, remove old flow control structure and an old footbridge, clean arch on Mill Street Bridge so that all 3 arches are operational, Maynooth widen channel downstream of Mill Street Bridge and raise bank College & Lyreen Flood Relief Scheme Nicholas March / Lyreen River levels as well as upsizing bridge. Also included is: replace part of surrounding Preliminary Report Review O'Dwyer Ltd. May 2001 retaining wall to provide a minimum rectangular channel of 8m, area increase channel width to 7m and slope banks from chainage 2339m to 3121m, remove old bridge, upsize culvert from chainage 3159-3169m, increase channel width to 5m and slope banks as well as regrade slope from 3159-3639m, increase

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Flood Relief River Name Report Name Author Date Recommendations Study channel width to 5m and slope to 45 from 3683-3999m and isolate manhole/French drain so as not to contribute to the Meadowbrook catchment. Recommended upgrade to Mooney's stream as: cleaning, DBFL regrading and increasing the dimensions of open channel Catchment Study of Consulting sections and cleaning, upgrading, lining replacement and Mooney's & November Newbridge Mooney's and Sexes Civil & regrading of piped sections. Upgrade to Sexes Stream include: Sexes streams 2002 Streams, Newbridge Structural cleaning, regrading, sewer lining and increasing the dimensions Engineers of open channel sections along with replacement of two short piped sections. Glending @ No report just additional information. Photographs from August No report Blessington 2008, Extent of flooding drawing, Flooding data for Blessington Drawings outlining upgrade works. Drawings include: Oldtown Kilgallen & channel upgrade works, Vanessa Lawns channel upgrade Cellbridge Cellbridge Flood Relief Partners works, Cellbridge Town A.F.C. channel upgrade works, Dard Toni River July 2009 Flood Relief Works Phase 1 Consulting Court channel upgrade works, Dara Crescent / Main Street Engineers channel upgrade works, Main Street / River Liffey channel upgrade works & Std. detail of trash screen. Watermain also being installed. For the flood defences, these will comprise of an earth bund ranging from 0.85 to 2.75m in North City Arterial Watermain McCarthy height. Some areas will require a combination of walls, gates & Clontarf Flood Defences - December Clontarf Sea Hyder and dams. The report completed by Royal Haskoning in 2005 Environmental Impact 2007 Consultants identified that flood defence would be needed in Clontarf. Statement (Final) Further information provided in point 3.2 of this report on details of the proposal. The proposal is to provide a promenade and cycleway from Wooden Bridge to Causeway Road that will also provide flood defence along this section of Clontarf Road and James Larkin Promenade & Roughan & Road. Three distinct designs will be used to provide an efficient Dollymount Sea June 2009 Flood Protection Project EIS O'Donovan and environmentally sensitive solution. These include a steel deck supported on piles, a retaining wall option which makes use of the existing grassy areas along the scheme and also cable stayed bridge structure supporting the promenade. 02 Proposing flood alleviation measures at Killal Road and Proposed Flood Alleviation Dublin County Pluvial Flooding November Drumcliffe Road. Flood alleviation takes the form of a 1m deep Swales Council 2010 swale.

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Flood Relief River Name Report Name Author Date Recommendations Study Information relating to drainage plans for the city, DCC is currently in the preliminary planning stage of this project. DCC is Sewerage & Dublin City DCC website also in the preliminary planning stage of a scheme that can Surface water remove stormwater from the combined City Centre Interceptor Sewers. The Defence Asset Survey Database for Dublin City Council is a Microsoft Access-based system designed for Asset Management. The database provides the user with a tool to assist in the management of the defence structures in the Dublin area, allowing easy monitoring of the condition and performance Defence Asset Survey 11 of any individual stretch of defence. The database provides a Royal Database - Dublin City December straightforward means of identifying areas and defences along Haskoning Council User Manual 2003 the Dublin tidal coastline, and allows easy access to all known information about each defence structure, including digital photographic records. The need for maintenance and repairs to any structure can be quickly identified, and a record of the cumulative expenditure on each stretch of defence is kept, providing a valuable tool for management decisions. Draft Strategic Flood Risk Kilgallen & Recommends that an individual site specific FRA is undertaken County Assessment. Kildare County Partners January at a number of locations. Some other locations do not require a

Kildare Development Plan 2011- Consulting 2011 FRA to be undertaken. Each area is listed in tables 1, 2 and 3 of 2017 Engineers the report. The aim is to develop, protect, improve and extend water, waste water and flood alleviation services throughout the county and to prioritise the provision of water services infrastructure to County Draft Kildare Development CAAS complement the overall strategy for economic and population Kildare Plan 2011-2017 growth and to achieve improved environmental protection. Outlines a number of issues relating to flooding and how the county council will assess. Various reports include providing information on the plan as well County Reports on Kildare CAAS as high level flood information and reports on altering wording of Kildare Development Plan various sections of the development plan.

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2.3.2 Historical Flood Data

Information on historical flood events was sought from a variety of sources including OPW and Local Authority records, internet searches and other general enquiries. In total, 43 historical events were identified that lead to flooding within AFAs situated in HA09 during the period 1880 to 2011 as detailed in Table 4.8. A summary of the information available for each of these events is presented in Section 4.4.

2.3.3 Baseline Mapping

RPS has obtained complete baseline mapping coverage of the entire Eastern CFRAM study area. The mapping which has been supplied by OPW includes the following datasets:

• ERBD Digicity10000 Raster;

• ERBD Digitowns 10000 Raster;

• ERBD OS MAP 5000 Raster;

• ERBD OS MAP 5000 Vector;

• ERBD OS MAPS 1000 Vector;

• ERBD OS MAPS 1000Raster;

• ERBD OS MAPS 50000 Raster;

• ERBD Six Inch Tiles;

• Orthophotography (Raster);

• ERBD OS Map 2500 Vector.

Due to the limited quality of the 5000 and 1000 raster mapping when printed at the scales required for this study, the equivalent vector mapping had to be processed using Feature Manipulation Engine Software to convert it from AutoCAD to ArcMap format. During the conversion process it was discovered that complete spatial coverage had not been included in the original OPW data supply. Consequently, additional 2500 vector mapping was requested. Again this information was also provided in AutoCAD format which had to be converted into ArcMap shapefile format for use within this study.

2.3.4 Hydrometric Data

Details of the hydrometric data available for HA09, and the analysis of this data are presented in Sections 4.1 and 4.4. In summary, 56 hydrometric stations (2 OPW and 54 other) were identified as

IBE0600Rp0008 25 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL being, or having been, operational within HA09. However, of these only 32 had data available for use and only 19 are located along watercourses to be modelled as part of the Eastern CFRAM Study although all 32 will be used to inform the hydrological analysis and derivation of return period flows.

2.3.5 Meteorological Data

Meteorological data provided by Met Éireann through OPW at the project outset was subject to a gap analysis and additional data was acquired directly by RPS as required. Requests were also issued to Local Authorities for any additional rainfall data they might possess over and above that available from the Met Éireann gauges. Further discussion of the actual rainfall data obtained is presented in Section 4.2.

2.3.6 Land Use Data

Following various data requests, land use data obtained includes CORINE land cover data, GSI data and development data. The development plan and GSI datasets received are outlined in Sections 2.3.7 and 2.3.9.

The CORINE datasets obtained are as follows:

• EPA_Corine_2000rev;

• EPA_CorineChangesOnly_2006;

• EPA_Corine_2006_complete.

Having viewed the European Environment Agency (EEA) website (http://www.eea.europa.eu/data- and-maps/data/corine-land-cover-2000-clc2000-seamless-vector-database-3) it was identified that the current European version is ‘CORINE 15’ which was updated in August 2011. A query was issued to EPA Ireland to ascertain if the updated European CORINE 15 dataset had any impact on the Irish CORINE dataset, to which they responded that they were not aware of any updates made to the Irish CORINE data and that the CORINE 2006 dataset supplied is the latest version of the dataset available for Ireland.

2.3.7 Planning and Development Information

Accurate and current development zoning information is essential to the correct delineation of AFA extents and will also be important when considering options and developing future scenarios. At present RPS have the following development zoning datasets;

Dunlaoghaire Rathdown County Council:

• 6_Year_Motorway_Proposal(in_tunnel).MAP - Motorway6YrProposal_InTunnel_pl_100702 • 6_Year_Motorway_Proposal.MAP - Motorway6YrProposal_pl_100702

IBE0600Rp0008 26 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL

• 6_Year_Road_Proposal.MAP - Road6YrProposal_pl_100702 • Architectural_Conservation_Area.MAP - ArchitecturalConservationArea_pg_100702 • BOUNDA~1.MAP -Boundary_StrategicDev_pg_100702 • BURIAL_GROUND.MAP - BurialGround_pg_100702 • CANDID~1.MAP - CandidateArchitecturalConservationArea_pg_100702 • COUNCIL_HOUSING.MAP - CountyCouncilHousing_pt_100702 • INSTITUTIONAL_LANDS.MAP - InstitutationLands_pt_100702 • Local_Area_Plan.MAP - LA_Plan_pg_100702 • Long_Term_Motorway_Proposals.MAP - LongTerm_MotorwayProposals_pl_100702 • Long_Term_Road_Proposals.MAP - LongTerm_RoadProposals_pl_100702 • MEWS_DEVELOPMENT.MAP - MewsDevelopment_pl_100702 • NO_INC~1.MAP - NoIncreaseNumBuildingsPermissable_pg_100702 • Objective_A.MAP - ObjA1_ProvideNewResidentialCommunities_pg_100702 • Objective_A1.MAP - ObjA_ProtectOrImproveResidentialAmenity_pg_100702 • Objective_B.MAP - ObjB_ProtectImproveRuralAmenity_pg_100702 • Objective_DC.MAP - ObjDC_ProtectProvideImproveMixedUseDistricts_pg_100702 • Objective_E.MAP - ObjE_ProvideEconomicDevAndEmployment_pg_100702 • Objective_F.MAP -ObjF_ProvideOpenSpace_pg_100702 • Objective_G.MAP -ObjG_ProtectImproveHighAmenityAreas_pg_100702 • Objective_GB.MAP -ObjGB_ProtectEnhanceOpenNatureofLands_pg_100702 • Objective_MTC.MAP -ObjMTC_ProtectImproveMajorTownCentreFacitlities_pg_100702 • Objective_NC.MAP -ObjNC_ProtectProvideMixedUseNeighbourhoodCentreFacilities_pg_100702 • Objective_TLI.MAP -ObjTLI_SupportEnhance3rdLevelEducationInstitues_pg_100702 • Objective_W.MAP -ObjW_ProvideWaterfrontDevAndHarbourUses_pg_100702 • Proposed_Luas_Line_Extension.MAP -Proposed_LuasLine_Ext_pl_100702 • PROPOSED_NATURAL_HERITAGE_AREAS.MAP - Proposed_NaturalHeritageAreas_pg_100702 • PROPOSED_SPECIAL_PROTECTION_AREA.MAP - Proposed_SPA_pg_100702 • Proposed_Walkway_Cycleway.MAP - Proposed_WalkwayCycleway_pl_100702 • PROPOS~1.MAP - ProposedLuasLineUnderConstruction_pl_100702 • PROPOS~4.MAP - ProposedBusPriorityRoutes_pl_100702 • Public_Rights_of_Way.MAP - PublicRightsOfWay_pl_100702 • RECORD_OF_MONUMENTS_AND_PLACE.MAP - Record_MonumentsAndPlace_pg_100702 • RECORD_OF_PROTECTED_STRUCTURES_LINE.MAP - Record_ProtectedStructures_pl_100702 • RECORD_OF_PROTECTED_STRUCTURES_POLY.MAP - Record_ProtectedStructures_pg_100702 • Recreation_Access_Route.MAP - RecreationAccessRoute_pl_100702 • SPECIFIC_OBJECTIVES_POINT.MAP - Specific_Objectives_pt_100702 • SPECIFIC_OBJECTIVES_POLY.MAP - Specific_Objectives_pl_100702 • To_Preserve_Prospects.MAP - PreserveProspects_pt_100702 • To_Preserve_Views.MAP - PreserveViews_pt_100702 • To_provide_for_a_Primary_School.MAP - ProvideFoPrimarySchool_pt_100702 • TO_PRO~1.MAP - ProvideForPostPrimary_pt_100702 • TO__PR~1.MAP - ProtectPreserveTreesWoodland_pt_100702 • TRAVELLER_ACCOMODATION.MAP - TravellerAccommodation_pt_100702 • Urban_Framework_Plan.MAP - UrbanFrameworkPlan_pg_100702 • Wicklow_Way.MAP - WicklowWay_pl_100702

Dunlaoghaire Rathdown also have their County Development Plan 2010-2016, all up to date Variations to the CDP and all current Local Area Plans (including any environmental reports) available on their council website: www.dlrcoco.ie under planning department.

South Dublin County Council

• SDCC_DevPlan2010_2016_USE_ZONING_OBJECTIVES.map

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• Cemeteries_P20111017-1627.csv • Churches_Convents_P20111017-1608.csv • DBO_devplan2010_AMENITY_LINE_P20111014-1259.dbf • DBO_devplan2010_AMENITY_P20111014-1259.dbf • DBO_devplan2010_Areas_Sensitive_to_Forestry.shp_P20111014-1605.xml • DBO_devplan2010_RPS_Excluding_Multiples.shp_P20111014- • DBO_devplan2010_Transport_2010.shp_P20111014-1617.xml • DBO_devplan2010_USE_ZONING_OBJECTIVES.shp_P20111014-1644.xml • sdcc_planningapps_geography_points_P20120131-1833.csv • sdcc_planningapps_geography_polygons_P20120131-1833.csv • sdcc_Planning_applications_Register_P20120201-0937.dbf • sdcc_planning_apps_appeals_P20120131-1833.csv • SDCC_Primary_Schools_P20111017-1257.xls • SDCC_Secondary_Schools_P20111017-1323.csv

Wicklow County Council:

• CDP2010-2016 - Employment-Tourism-Health; • Wicklow CoCo Land Zoning; • Wicklow CoCo LAP-TP Boundaries.

Kildare County Council:

• Draft Kildare County Development Plan 2011-2017 (series of hard copy and pdf documents) • CHAPTERS 1 to 19, TOC, addendums, appendices, non-technical summary etc. • Rural Housing Policy Zones.dwg • Draft Strategic Flood Risk Assessment.Pdf • +200-09-410 CARAGH_MISC.2010 (not used).bak • 200-09-409 Johnstown 2010.bak • 200-09-409 Kilcock.dwg 2010.dwg • 200-09-410 CARAGH_MISC.2010.bak • 200-09-413 KILL_ENVIRONS.dwg 2010.dwg • 200-09-415 BLESSINGTON 2010.dwg • 200-09-416 PUNCHESTOWN.dwg 2010.bak • 200-09-418 23.1_Naas_Environs_west.dwg 2010 • 200-09-424 NAAS_ENVIRONS (south).dwg • 200-10-514 Amendment 18.4.dwg • 200-10-515 Amendment 18.5.dwg • Not for printing zoning layer only to kilgallon.dwg • Not for printing zoning layer only to kilgallon.dwg • 200-07-202 _adopted.dwg • 2002 Newbridge LAP_ with new mapping.dwg • adopted Collinstown Local Area Plan 20011-2017.dwg • Adopted Leixlip L.A.P.(200-09-299).dwg • Adopted Leixlip L.A.P.(200-09-299)_Limit.dwg • Atgarvan Adopted Plan.dwg • Kill_LAP.dwg • Map 4 (200-08-203) adopted.dwg • Map 5 (200-08-214) Land use 25-05-09.dwg • Map 5B (200-09-398) Zoning Map Town Centre.dwg • Map_3(a)_200_08_241 Kilcock_Land_Use_Zoning.dwg

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• Maynooth_Map 5 (200-08-235) Land use draft november.dwg • PROSPEROUS_acad redraw.dwg • Allen.dwg • Ardclogh.dwg • Brannockstown.dwg • .dwg • Rathmore_Eadestown.dwg • .dwg • Twomilehouse.dwg • Heritage plan.dwg • Ballymore Eustace Village Plan.dwg • Johnstown Village Plan.dwg • Village Plan.dwg • Kill_LAP.dwg • .dwg.

Dublin City Council

• DCC_5AministrativeAreas2009_P20110929-0731.dgn • DCC_CityBoundary_P20110805-1206.dgn • DCC_DevPlan2001EnvironmentalDesignationsMapsetJ_P20110905-1359.pdf • DCC_DUBLINK_APPEAL_P20111010-0844.csv • DCC_DUBLINK_BASE_P20111010-0839.csv • DCC_DUBLINK_FURINFO_P20111010-0844.csv • DCC_PlanApps_P20111003-1322.csv • DCC_StrategicCyclenetwork_P20070124-0948.dwg • DCC_SUDsRegister_P20110917-1343.csv • CONSERVATION_AREA_P20110208-0959_none.dbf • DCC_PlanApps_P20111003-1322.dbf • Inner_City_KDA_shapes_P20110419-1058_none.dbf • KDA_Map_shapes_P20110419-1057_none.dbf • KDC_Map_shapes_P20110419-1101_none.prj • LAP_P20110316-1151_none.dbf • suds_database_P20100927-1510.TAB • Airport_Zone_P20100913-1010.ID • Airport_Zone_P20100913-1010.MAP • ARCH_SITES_P20110208-1017.ID • ARCH_ZONES_P20101011-1044.ID • CONSERVATION_AREA_P20101011-1026.ID • Contributions_shapes_P20110905-0850.ID • Dublin_Boundary_2010_P20110330-1301.DAT • ENVIRON_DES_shapes_P20110905-1132.DAT • LAP_P20101008-1144.ID • ROADS_ellipses_P20110905-0859.DAT • ROADS_lines_P20110905-0859.DAT • ROADS_text_P20110905-0855.tab • SEVESO_P20110328-1150.DAT • ZONING_P20110331-1345.ID

Fingal County Council

• FCC_Airport_P20110829-2221.csv • FCC_Beaches_P20110804-1444.kml

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• FCC_Beaches_P20110829-2200.csv • FCC_BurialGrounds_P20110829-2200.csv • FCC_CountyGeologicalHeritageSites_P20111014-0938.zip • FCC_dublinkappeal_P20111013-1605.csv • FCC_dublinkbase_P20111206-1509.csv • FCC_dublinkfurinfo_P20111013-1606.csv • FCC_FingalNIAHSurvey_P20111128-1157.csv • FCC_FingalNIAHSurvey_P20111128-1157.xml • FCC_FireStations_P20111201-2134.csv • FCC_GardaStations_P20111201-2134.csv • FCC_HealthCentres_P20111201-2134.csv • FCC_Libraries_P20110901-1706.csv • FCC_LocalAreaPlans_P20111014-0945 • FCC_LocalObjectives_P20111014-0949.zip • FCC_NatureDevelopmentAreas_P20111014-0951.zip • FCC_PlanningApps_P20111017-1141.zip • FCC_Population_P20110701-2330.csv • FCC_RecordofProtectedStructures_P20111014-1044.zip • FCC_Schools_P20110901-1240.csv • FCC_TrainStations_P20110829-2221.csv • FCC_WeatherStations_P20110829-2221.csv • FCC_ZoningObjective_P20111014-1048.zip • Fingal_NIAHSurvey_P20111128-1157.kml

2.3.8 Environmental Data

RPS has identified a preliminary list of datasets and sources as indicated in Table 2.2 which are relevant to the Strategic Environmental Assessment and Appropriate Assessment. However this list is subject to revision pending the outcome of the scoping exercise which is ongoing,

Table 2.2: Preliminary List of Environmental Datasets

SEA Issue Area Data Availability

Biodiversity, Flora and National Parks and Wildlife database (e.g. www.npws.ie Fauna protected habitats and species including RPS has access SAC/SPA/NHA). Biodiversity, Flora and Relevant Freshwater Pearl Mussel Sub- www.npws.ie Fauna basin management plans (if relevant). RPS has access Biodiversity / Flora and Invasive species, threatened species, www.biodiverity.ie Fauna protected species. Free to download Water/Biodiversity/Flora Inland Fisheries Ireland - Eastern Area www.fisheriesireland.ie and Fauna Species present, counts etc., Fisheries On request assessments if available. Water / Material Assets databases; www.waterwaysireland.ie Free to download but not as GIS

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SEA Issue Area Data Availability

Cultural Heritage/ Cultural Heritage e.g. Brú na Bóinne www.heritagecouncil.ie Biodiversity / Flora and UNESCO World Heritage Site Free to download Fauna Natural Heritage e.g. local biodiversity action plans Cultural Heritage Record of Monuments and Places; www.archaeology.ie RPS has access Cultural Heritage National Inventory of Architectural Heritage www.buildingsofireland.ie (NIAH) Free to download Material Assets Coillte forestry database (FIPS) www.coillte.ie Will request Soils / Geology Geological Survey of Ireland (GSI) mapping, www.gsi.ie including groundwater maps; groundwater RPS has access vulnerability, protection schemes; soils classification. Soils Teagasc soil information; www.teagasc.ie RPS has access Material Assets / Land Corine and Landcover Land Use RPS has access Use Databases; Water Information gathered during the RPS has access implementation of the Water Framework Directive; Population Central Statistics Office database, including www.cso.ie census data. Prelim 2011 data available but RPS has access to 2006. full dataset expected in March 2012 Will request 2011 when it becomes available. Material Assets / Department of Agriculture, Food and the Will request. Landuse Marine databases e.g. fertilizer usage. All aspects Relevant County Development Plans Will be requested from environmental, heritage Detailed flora and fauna field surveys, officers during scoping habitat mapping, water quality consultation measurements, tree protection orders, landscape character areas, seascapes, protected views, areas of high amenity, development plan boundaries and zonings digitally; All aspects Other Local Authority datasets; Will be requested from environmental, heritage officers during scoping consultation All aspects Regional Authority datasets; Will be requested during scoping consultation

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SEA Issue Area Data Availability

All environmental EPA databases (e.g. groundwater and www.epa.ie aspects surface water quality, air quality, etc.); Free to download EPA 2008 State of Environment Report and updated report, if available; and EPA ENVision (Environmental Mapping / Geographical Information System). All environmental EPA Additional datasets e.g. contaminated www.epa.ie aspects land, brownfield sites etc Not available for download but will request. General / mapping 3 Rivers Data: DTM, historical mapping etc. RPS has access

General / mapping Aerial photography RPS has access OSI vector mapping

It is also important to note that many of the environmental dataset are not static over time and thus early acquisition of all data is not necessarily desirable, rather such data is much better requested only when it is required. Consequently, RPS will maintain contact with the relevant data owners as the project develops to ensure that data requests are appropriately timed to ensure that the most up to date information is used to inform the study.

2.3.9 Soil and Geological Data

Following requests to Geological Survey Ireland (GSI) for soil and sub-soil information to inform the selection of appropriate parameters for the MIKE-NAM modelling activities, RPS have obtained the following datasets:

• Bedrock and SG Aquifers Union;

• Soils – Wet and Dry;

• Sub soil Permeability;

• Vulnerability.

Initial review of this data indicates that it will be sufficient for the intended purpose.

2.3.10 Defence and Coastal Protection Asset Data

Requests to Local Authorities and OPW for details of any information held on existing flood defence and coastal protection assets has provided information for assets within HA09. Principally RPS has received Dunlaoghaire and Rathdown Coastal Defence Strategy which includes their final report and

IBE0600Rp0008 32 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL also numerous photographs. RPS has also obtained details of the Dublin Bay study undertaken by Haskoning on behalf of Dublin City Council.

Dunlaoghaire Rathdown

• Coastal Defence Strategy - 12495_DLRCC CDSS Final_20100930 Rev C Main Body and Appendices A to J for CD

• 12495 Final Report Appendix I Photographs

Dublin City Council

• Dublin Coastal Protection Project Final Report 29 April 2005 - varied files and appendices - Files received by OPW from Dublin City Council • SAFER - C048 Interreg IIIB Project - Dublin Coastal Flooding Projection Project o Volume 1 - Main Report - Dublin Coastal Flooding Protection Project - SAFER - Hard Copy o Final Report - Volume 2A - Appendices for chapters 1 - 14 - Appendices of report - Hard Copy o Final Report - Volume 2B - Appendices for chapters 15 - 19 - Appendices of report - Hard Copy • Dublin SAFER Flood Atlas Volume 1 Coastal and Estuarine Flood Hazard Maps - Flood hazard Maps - Hard Copy • SAFER - Strategies and Actions for Flood Emergency Risk Management - Leaflet of information - Hard Copy • Flood Emergency Management in Dublin City Behind the Paradigm - DVD - DVD - DVD • AssetData_2 - Various Photographs - linked to a Database - jpeg • Dodder Outfalls - Various Photographs - linked to a Database - jpeg • ESB Survey 2004 - Various Photographs - linked to a Database - jpeg • Liffey Boardwalks - Various Photographs - linked to a Database - jpeg • Liffey Outfalls - Various Photographs - linked to a Database - jpeg • O5 Appendices a4_B&W.doc - Standard Protection Maps - List of Drawings - Word • O5 SoP 01 .pdf - Standard Protection Maps MERRION STRAND TO GREAT SOUTH WALL - Pdf • O5 SoP 01 Sandymount Ringsend Figure.pdf - Standard Protection Maps Sandymount Ringsend - Pdf • O5 SoP 02 South Dublin Port Figure.pdf - Standard Protection Maps South Dublin Port - Pdf • O5 SoP 03 North Dublin Port Figure.pdf - Standard Protection Maps North Dublin Port - Pdf • O5 SoP 04 Clontarf Figure.pdf - Standard Protection Maps Clontarf - Pdf • O5 SoP 05 North Howth Figure.pdf - Standard Protection Maps North Howth - Pdf • O5 SoP 06 Sutton South Howth Figure.pdf - Standard Protection Maps Sutton South Howth - Pdf • O5 SoP 07 Baldoyle Figure.pdf - Standard Protection Maps Baldoyle - Pdf • O5 SoP 08 Portmarnock Figure.pdf - Standard Protection Maps Portmarnock - Pdf • O5 SoP 09_1 Lower Liffey Figure.pdf - Standard Protection Maps River Liffey Lower & Upper - Pdf • O5 SoP 10 River Dodder Figure.pdf - Standard Protection Maps River Dodder - Pdf • O5 SoP 11 River Tolka Figure.pdf - Standard Protection Maps River Tolka - Pdf • O5 SoP 12 Royal Canal Figure.pdf - Standard Protection Maps Royal Canal - Pdf • setup - Setup for Database - exe • SeaDefence.mdb - Database File - Access • DCC Database User Manual.doc - User Guide for Database - Word • South Campshire Flood Protection Project, George's Quay, City Quay and Sir John Rogerson's Quay, Dublin 2 Environmental Impact Statement V1 of 4 Non-Technical Report • Sutton to Sandycove Phase One and Two • DCC_Clontarf Flood Defence - Webpage Content

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• DCC_DollymountPromenadeAndFloodProtectionProject-Webpage Content.doc • DCC_SandymountPromenadeAndFloodProtectionProject - Webpage Content.doc

The information obtained to date will be supplemented as further assets are identified and relevant geometric data collected through the HA09 survey contract. Information on the current condition of all assets will be obtained during the follow up asset condition survey.

2.3.11 Greater Dublin Strategic Drainage Study (GDSDS) Data

Many of the watercourses within the Greater Dublin area were previously studied as part of the Greater Dublin Strategic Drainage Study (GDSDS) and as such a range of GIS datasets are available in respect to these watercourses. In the context of HA09, four defined HPWs (including all tributaries) were previously included in the Greater Dublin Strategic Drainage Study (GDSDS), namely:

• • Camac River and Tributaries • Poddle River • Griffeen River (Lower reach) and tributaries

Whilst the GDSDS datasets also contain information for many other watercourses, for example the Dodder and Tolka, these have not been interrogated as consideration of these catchments under the scope of the Eastern CFRAM Study is limited to a review of the previous FRAM study methods and outputs and does not extend to modelling of these catchments. The GDSDS codes assigned to the relevant Eastern CFRAM Study High Priority Watercourses and associated catchments are as follows:

• Santry River – S1002

• Camac River and Tributaries – S1004

• Poddle River – S1005

• Griffeen River (Lower Reach) and Tributaries– S2001

These codes were used to extract relevant GIS information from the GDSDS database as provided by OPW at the project outset. Figure 2.1 shows the river polylines, river labels and catchment boundary lines extracted for the above named rivers using the relevant GDSDS codes.

IBE0600Rp0008 34 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL

Figure 2.1: GDSDS Rivers that are HPWs in HA09

IBE0600Rp0008 35 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL

2.3.11.1 Santry River Datasets (S1002)

As depicted by Figure 2.1, area S1002 constitutes the Santry River which discharges to the sea north of Dublin Harbour. The Santry River is culverted along various portions of its length and receives storm water discharges from the surrounding storm sewer network serving the S1002 storm discharge area. DCC also advised that a branch of the Naniken connects to the Santry River and increases the contributing catchment during storm conditions due to the inclusion of a number of CSO discharges. This contributing catchment is included within the catchment outline shown in Figure 2.1.

2.3.11.2 Camac River GIS GDSDS Datasets (S1004)

As depicted by Figure 2.1, several named tributaries make up the Camac River catchment, S1004, all of which are included as High Priority Watercourses for the Eastern CFRAM Study. The majority of these are named tributaries, although some smaller watercourses are un-named. Named tributaries include:

• Alverna • Brookview • Boherboy Stream • Cheeverstown • CityWest • • Corbally • Corkagh Demesne • Crumlin • Fitzmaurice • Fortunestown • Kingswood • NewSaggart • Rathcoole • Robinhood Stream • • Tallaght • Verschoyles •

These watercourses are tributaries of the Camac River which is a tributary of the River Liffey.

2.3.11.3 Poddle River GIS GDSDS Datasets (S1005)

As depicted by Figure 2.1 the Poddle River is a tributary of the River Liffey. The Poddle River is culverted along various portions of its length and receives storm water discharges from the surrounding storm sewer network serving the S1005 storm discharge area.

IBE0600Rp0008 36 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL

2.3.11.4 Griffeen River (Lower Reach) GIS GDSDS Datasets (S2001)

As depicted by Figure 2.1, the lower reach of the Griffeen River is part of the S2001 GDSDS boundary. There are also several named tributaries of the Griffeen River within this boundary which are also HPWs including:

• Finnstown • Lucan • Ryvale • Milltown • Backstown • Millstream

These watercourses are tributaries of the lower Griffeen River which is a tributary of the River Liffey.

Table 2.3 lists the GDSDS datasets collated for areas S1002, S1004, S1005 and S2001.

Table 2.3: GDSDS GIS Layers available within HA09

Description GDSDS Layer Filename Layer S1002 S1002 S1004 S1005 S2001 GDSDS Number Number Development Data 1 Proposed Development Develop_1 1A Population Seed Data Popseed_1A 1B Trade Effluent Discharges Trade_1B Proposed Dublin Motorways ProposedDublinMotorways_074512001 Ordnance Survey Map and Environmental Data Layers 3 Low detail faded background map Fadedmap_3 3A Faded OS Maps (1 per tile) Fadedos_3A_(mapname) 4 Wastewater Treatment works WwTW_4 15 Rivers Rivers_15 16 Basements Basements_16 Location Names LocationNames_pt 76 General Labels 75 District Labels Existing Dublin Motorways ExistingDublinMotorways_074512001 National Primary Roads NationalPrimaryGDSDS_Area_074512001 Asset Data Layers 31A Foul System Schematic Layer Foulscheme_31A 31B Combined Schematic Layer Combinedscheme_31B 31C Storm System Schematic Layer Stormscheme_31C 33 Catchment notes Notes_33 34 SUS Manhole database (links) Suslink_34 35 Culverted Watercourses Culverted_35 36 SUS Manhole database (nodes) Susnode_36 37A Model Database (Foul / Combined Modelpipe_37A conduits) 37B Model Database (Storm conduits) Modelpipe_37B 38 Model Database (Rising mains) Modelpump_38 39 Model Database (nodes) Modelnode_39 40 Ancillary Structures Ancillary_40

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Description GDSDS Layer Filename Layer S1002 S1002 S1004 S1005 S2001 GDSDS Number Number 41 Model Catchment Areas Modelcatch_41 42 Foul Catchment Boundary Fboundary_42 43 Storm Catchment Boundary Sboundary_43 Council Boundary Layers 44 Map of Ireland and Counties Ireland_44 45 Local Council Boundaries Council_45 Historical Records Layers 50 Historical/Reported Flooding Data Repflooding_50 51 Previously Reported Grade 4/5 Repstruct_51 sewers Site Investigation Data Layers 60 CCTV Survey Cctvsurvey_60 61 Flow Survey Flowsurvey_61 62 Asset Survey Assetsurvey_62 63 River Cross Section Survey Riverxsurvey_63 2 Flow Monitor Catchment Areas Flowareas_2 17 Flooding Risk Floodrisk_17 65 Permanent Flow Monitor Sites Permanentflow_65 66 Rain Gauge Sites Raingauge_66 73 Structural Deficiencies Deficiency 73

2.4 DATA REVIEW – DODDER CFRAM STUDY AND TOLKA FLOOD STUDY

2.4.1 Dodder CFRAM Study

As RPS was the consultant commissioned to carry out the Dodder CFRAM Study they are in possession of all the study’s data. However for the purposes of this report the following significant data has been identified for review:

• River Dodder Catchment Flood Risk Management Plan, Project Inception Report

• River Dodder Catchment Flood Risk Management Plan, Hydrological Analysis Report.

• River Dodder Catchment Flood Risk Management Plan, Hydraulic Analysis Report.

• River Dodder Catchment Flood Risk Management Plan, Strategic Environmental Assessment, Scoping Report.

• River Dodder Catchment Flood Risk Management Plan, Strategic Environmental Assessment, Environmental Report.

• Dodder CFRAM Study, Option Development Process, Preliminary Screening of Measures.

• Dodder CFRAM Study, Option Development Process, Multi Criteria Analysis.

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• River Dodder catchment Flood Risk Assessment and Management Study, Maintenance Plan.

• Dodder Catchment Flood Risk Management Study, Present Day Flood Extent Scenario Maps.

• Dodder Catchment Flood Risk Management Study, Present Day Scenario – Dodder Water Depth Maps.

• Dodder Catchment Flood Risk Management Study, Present Day Scenario – Dodder Flood Velocity Maps.

• Dodder Catchment Flood Risk Management Study, Present Day Scenario – Dodder Hazard Maps.

As part of the Flood Event response requirement within the overall Eastern CFRAM Study, RPS visited and reported on flooding in the following places:

The River Dodder:

•

• to Lansdowne

• House

• Cottages

• Lansdowne to Newbridge

• Milltown to Dropping Well

• Milltown to Strand Terrace

• O’ Gardens

• The RDS

The Little Dargle Stream

• Nutgrove Avenue

The Owendoher Stream

• Woodview Cottages

IBE0600Rp0008 39 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL

The Dundrum Slang Stream

• Dundrum Shopping Centre

• Highfield Park

• Riverside

• Willow Bank Apartments

RPS representatives are due to attend Public Consultations to be held in March 2012. This will inform people of the findings and recommendations of the study and to seek their views and feedback on the draft Plan.

The OPW have since finalised the list of AFAs and no additional areas have been identified within Dodder CFRAM Study for inclusion in the Eastern CFRAM Study scope.

2.4.2 Tolka Flood Study

As RPS was the consultant commissioned to carry out the Tolka Flood Study they are in possession of all the study’s data. However for the purposes of this report the following significant data has been identified for possible review:

• Project Inception Document – Methodology for Study Deliverables (074515001Rp0007d)

• Hydrological Analysis (074515001Rp0024)

• Draft Technical Report (074515001Rp0026)

• Draft Final Report (074515001Rp0030)

• River Modelling Report (074515001Rp0032)

• Implementation Report (074515001Rp0035)

• Catchment Based Flood Risk Management – Inception to Construction. Gillespie, G. and McEntee, D. May 2007.

2.5 DATA OUTSTANDING

2.5.1 Hydrometric Area 09

RPS has made one final request for missing information / data from each of the Local Authorities. The request was made at the beginning of December 2011 via email (re-issued in February 2012); each Local Authority was forwarded a tailored document outlining study data requirements and also the

IBE0600Rp0008 40 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL information / data that has been received to date from them or from OPW which covers their administrative areas. Within the document under each of the headings, Local Authorities have been requested to either provide any additional information they feel appropriate for the Eastern CFRAM Study or confirm that they have no further information. Also detailed in this document is information that has been requested that has not been provided. In response to this request Kildare County Council confirmed they have no further information to supply and Dunlaoghaire Rathdown County Council provided additional information regarding their Coastal Defence Strategy and confirmed that they have no more information to supply for this project. Dublin City Council provided additional scheme, drainage and development data and confirmed they have nothing further to supply. A breakdown of areas where no information has been received from the Local Authorities is detailed below:

South Dublin Council

• Flood Defence Asset Data;

Dublin City Council

• LiDAR Coverage (licensing issues are being resolved between DCC and OPW);

Fingal County Council

• Historic Flood Data

• Planning and Development Information (but has been downloaded via www.dublinked.ie Downloads).

• Defence and Coastal Protection Asset Data

• Existing Survey / Geotechnical Data;

• Aerial Photography of flooding

Wicklow County Council

• Existing Survey / Geotechnical Data;

• Other Receptor Data;

• Aerial Photography of flooding

2.5.2 Dodder CFRAM Study and Tolka Flood Study

No response has yet been received to the request made to Dun Laoghaire Rathdown (via email on 07/02/12). This request related to the provision of an update on any flood relief or risk management

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RPS will continue to monitor the situation throughout the three phase review process in case further data requests are required.

2.6 DATA GAPS

2.6.1 Hydrometric Area 09

At present RPS has not identified any significant data gaps that will impact on the completion of the Eastern CFRAM Study however this statement is made without having received any survey information or having fully established how much of the remaining data requested from the Local Authorities, outlined in the preceding section, is not available. RPS expect that as the final scope of the study is refined as the study progresses through the next phases additional data needs will be identified, which will be addressed in so far as is possible through on-going data collection exercises in a similar manner to the initial data collection phase reported here. Thus it is not possible at this point in time to categorically state that there are no data gaps which will impact in some way on the completion of the Eastern CFRAM Study.

RPS has been implementing data quality and validity checks on information that has been obtained throughout the data collection process. The findings of these checks have been briefly detailed in Table 2.4 below.

Table 2.4: Summary of Data Quality and Validity Checks

Section Section Comment Reference Heading

2.3.1 Flood Relief / Historical Flood data has been reviewed by a member of RPS staff to Risk ascertain its fitness for purpose. The outcome of the review has been Management detailed in Section 2.3.1 of this report. Measures

2.3.2 Historical Flood Historical Flood data has been reviewed by a member of RPS staff to Data ascertain its fitness for purpose. The outcome of the review has been detailed in Section 2.3.2 of this report.

2.3.3 Baseline Originally only Raster mapping was provided which was not fit for Mapping purpose as it was not of sufficient clarity for the production of detailed maps, therefore Vector mapping was requested and received which is adequate for printing detailed maps. Also complete coverage of HA09 was not supplied initially however full coverage has now been

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obtained following further data requests as described in Section 2.3.3.

2.3.4 Hydrometric Hydrometric Data has been reviewed by a member of RPS staff to Data ascertain its fitness for purpose. The outcome of the review has been detailed in Section 4. Preliminary Hydrological Assessment and Method Statement of this report.

2.3.5 Meteorological Meteorological Data has been reviewed by a member of RPS staff to Data ascertain its fitness for purpose. The outcome of the review has been detailed in Section 5. Detailed Methodology Review of this report.

2.3.6 Land Use Data RPS originally received old versions of Land Use datasets which were not fit for purpose. RPS therefore requested and obtained the most recent version of the Land Use datasets as outlined in section 2.3.6 of this report.

2.3.7 Planning and Some of the Planning and Development datasets received where not Development the latest revision of the County’s Development Plans and therefore a Information request was made to obtain their most recent datasets, which depict the zoning areas required by RPS. This is further detailed in 2.3.7

2.3.8 Environmental This information has not been fully assessed for fitness for purpose, Data as the information is not required at this early stage of the project.

2.3.9 Soil and Initial review of this data indicates that it will be sufficient for the Geological Data intended purpose.

2.3.10 Defence and RPS have obtained a very limited amount of information on Defence Coastal data, however further analysis of defence information shall be Protection undertaken during the asset condition surveys. Further information on Asset Data Defence Surveys is outlined in Section 3.2 Flood Defence Assets.

2.6.2 Dodder CFRAM Study and Tolka Flood Study

At present RPS has not identified any significant data gaps that will impact on the completion of the Dodder CFRAM Study and Tolka Flood Study review and hence overall Eastern CFRAM Study. However, this statement is made prior to commencing the detailed review of the Dodder CFRAM Study and Tolka Flood Study reports.

It may be that as the study progresses through the next phases additional data needs will be identified, which will be addressed in so far as is possible through on-going data collection exercises. For the

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Dodder CFRAM Study, this may include feedback from the public consultations which are due to take place in March 2012.

Another potential data source which may be required is spot gauge data at each hydrometric station, especially those that have recorded significant flood events since the completion of the Dodder and Tolka projects.

Thus it is not possible at this point in time to categorically state that there are no data gaps which will impact in some way on the completion of this element of the Eastern CFRAM Study.

2.7 CONCLUSION

In conclusion RPS has made every attempt to identify and obtain data that is valid and of good quality for use within the Eastern CFRAM Study. Requests have been issued and tracked in order to try and obtain as much relevant information as possible. The complete process of requesting and obtaining information has been recorded and logged within the various Request and Incoming Data registers. Reports and Spatial data have been reviewed to ensure they relate to the Eastern CFRAM study area and that they provide beneficial information for the project. During this process RPS identified a few datasets which were not fit for purpose for the project as they were out of date consequently RPS sourced and acquired the most up-to-date versions of such datasets.

RPS will supplement the information in relation to defence assets supplied by Local Authorities, where necessary with additional information collected and recorded during subsequent planned onsite surveys.

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3 SURVEYS

3.1 CHANNEL & CROSS-SECTION SURVEYS

The procurement of a survey for HA09 is being undertaken by JBA Consulting under a separate contract from the OPW. This survey contract encompasses the full channel cross-sections, details of hydraulic structures and geometric survey of defences and hydrometric stations and was advertised through e-tenders and OJEU on 12/08/2011. The returned tenders were evaluated and a contract was awarded to Murphy Surveys on 07/11/2011. Weekly on-site progress updates are being provided to RPS and the Eastern CFRAM Study progress group.

RPS involvement in this survey contract has been limited to a review of the original survey specification and the provision of information relating to new AFAs added after the survey contract was tendered which was intended to ensure all required areas were included in the survey scope. Consequently as no survey data has been received at the time of drafting of this report it is not possible to comment on the adequacy of the data from the HA09 survey contract.

3.2 FLOOD DEFENCE ASSETS

The identification of flood defence assets is a requirement of the HA09 channel and cross section survey contract and thus at present RPS have not established a definitive list of flood defence assets for HA09. However the locations of the flood defence assets identified to date are indicated in Figure 3.1 and listed in Table 3.1 below.

Table 3.1: Flood Defence Assets Identified in HA09 Survey Specification.

Location Notes Lucan to Chapelizod Walls Leixlip Walls Naas Walls

3.3 FLOODPLAIN SURVEY

The tender documents indicated that OPW would supply the results of a flood plain survey based on LiDAR techniques by November 2011. RPS has provided input in to the required coverage of this survey based on our initial assessment of AFA locations and extents however delivery of this information has been delayed and therefore it is not possible to make any comment on the adequacy of the received information for use in later stages of the Eastern CFRAM Study.

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3.4 PROPERTY SURVEY

The Generic CFRAM Study Brief requires property surveys to be undertaken to confirm, locations, type, use, floor area etc of properties identified as potentially being at risk consequently we will not be undertaking this work until draft flood hazard maps are available.

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Figure 3.1: Locations of Flood Defence Assets in HA09

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4 PRELIMINARY HYDROLOGICAL ASSESSMENT AND METHOD STATEMENT

4.1 HYDROMETRIC DATA

4.1.1 Hydrometric data – HA09

The OPW provided RPS with hydrometric station data from the OPW Hydrometric Section database. This consisted of all available data for all OPW stations within the Eastern RBD including Annual Maximum (AMAX) Series data for those stations included in the OPW Flood Studies Update (FSU) Programme. The OPW operate two river hydrometric stations within HA09, details of these stations are shown in Table 4.1.

Table 4.1: OPW Hydrometric Stations with available data within HA09

Station Number Station Name River/Lake Data Available Records Length

09001 Leixlip Ryewater Water Level & Flow Oct 1956 - Feb 2010 Water Level Only AMAX 1994 – 2009 09036 Kerdiffstown Morell Chart Data 1950-2010

An additional 54 hydrometric stations are located within HA09. 44 of these are owned by Local Authorities (operated by EPA) and 10 are owned by ESB. Hydrometric data is available for 30 stations of these (Five ESB stations and 25 EPA stations) and has been acquired by RPS. These are listed in Table 4.2. The data provided consisted of flow and level data and rating curves where available.

Table 4.2: Local Authority (EPA) and ESB Hydrometric Stations with Available Data in HA09

Station Station Name River/Lake Data Available Records Length Number 09002 Lucan Griffeen Water Level & Flow Mar 1977 - Feb 2002

09005 Clondalkin Camac Water Level & Flow Nov 1976 - Mar 1984

09006 Celbridge Liffey Water Level & Flow Jan 1967 - Jan 2007

09007 Golden Falls Liffey Water Level & Flow Jan 1950 - Jun 2011

09009 Willbrook Road Owendoher Water Level & Flow Nov 1980 - Jun 2011

09010 Waldron’s Bridge Dodder Water Level & Flow Jan 1986 - Jun 2011

09011 Frankfort Slang Water Level & Flow May 1982 - Aug 2011

09014 Ballyward Upper Liffey Water Level & Flow Jan 1989 - Dec 1991 09015 Liffey Water Level Only Sept 1982 - Nov 1990 Weir

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Station Station Name River/Lake Data Available Records Length Number 09016 Arthurstown Unnamed Stream Water Level & Flow Aug 1981 - Oct 1984

09019 Drumcondra Tolka Water Level & Flow Jan 1986 - Oct 1992

09021 Glassamucky Piperstown Water Level & Flow Feb 1988 - Oct 1988 Leixlip Power 09022 Liffey Water Level & Flow Jan 1950 - Jun 2011 Station 09024 Morell Bridge Morell Water Level & Flow 2001 - 2011 Ballinagee 09025 Ballinagee Flow Measurements Mar 1993 - May 2006 Bridge Annalecka 09026 Annalecka Brook Water Level & Flow May 2001 - May 2011 Bridge 09027 Broguestown Hartwell River Water Level & Flow Jan 2001 - May 2011

09032 Pollaphouca Liffey Headrace Ch. Water Level Only Jan 1950 - Jun 2011

09035 Killeen Road Camac Water Level & Flow Mar 1996 - May 2011

09037 Botanic Gardens Tolka Water Level & Flow Sept 1999 - Jun 2011

09040 Nicholastown Kilcullen Stream Water Level & Flow Feb 2009 - May 2011 Osberstown 09042 Naas Stream Water Level & Flow May 2009 - May 2011 House Kerdiffstown 09044 Morell Water Level & Flow Feb 2009 - Jun 2011 House Grand Canal 09045 Morell Water Level Only Mar 1977 - Mar 1987 Bridge 09047 Baronrath Painestown Water Level & Flow May 2009 - May 2011

09048 Anne’s Bridge Ryewater Water Level & Flow May 2001 - May 2011

09049 Maynooth Lyreen Water Level & Flow July 2001 - Jun 2011

09102 Cadbury’s Santry Water Level & Flow Aug 2001 - May 2011

09103 Glenasmole Dodder Water Level & Flow Dec 2007 - Jun 2011

09104 Weir Tolka Water Level & Flow 2007 - 2010

The remaining 24 Local Authority (EPA) / ESB hydrometric stations have no continuous monitoring data available. 18 of these stations are staff gauge only sites, and therefore only spot measurements were taken at these sites in the past and usually for one-off projects related to control of water pollution. The historical ESB hydrometric sites have continuous water levels recorded on charts. However, the old chart recordings are currently stored in the ESB archive and are not yet digitized; therefore no data is currently available for these stations.

Therefore in total, 32 hydrometric stations (Two OPW / 25 Local Authority (EPA) and five ESB) located in HA09 have data available for use within this Study.

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Each of the 32 stations with data available has a monitoring station fitted with a staff gauge and an automatic water level recorder. The automatic water level recorder can either be an autographic recorder or a digital datalogger. An autographic recorder is a simple float operated device that records water level on to a paper chart. These charts are then digitised to convert the data to a digital format. In recent years data loggers have replaced the recorder technology and are now installed at almost all stations where continuous water levels are recorded. The digital data from these loggers can be entered directly into a computer, overcoming the need to digitise water level records. The production of continuous flow data for a gauging station is derived from the water level data and it requires: continuous recording of water levels and; development of a station calibration. The station calibration is developed by plotting the results of flow measurements (spot gaugings) which have been carried out at various water levels and developing a stage-discharge relationship (also known as a rating curve) between water level and river flow. 28 of the 32 hydrometric gauges have flow data available that has been derived from continuous water level data using this methodology. The other four hydrometric sites have only water level data available.

As part of the FSU, selected hydrometric stations throughout the country were reviewed and analysed to generate a database of hydrometric data (using data up to 2004). Where applicable, OPW have provided a summary of this FSU generated station data, which includes any changes in rating classification, Highest Gauged Flow (HGF), Qmed and MAF estimates and the period of AMAX record analysed under FSU (including AMAX 2009). An FSU generated rating classification was also assigned to these stations. Of the 32 stations listed in Table 4.1 and 4.2, six were included in the FSU review and had a classification assigned as shown in Table 4.3. A definition of the rating quality classification is provided below the table.

Table 4.3: Final Station Rating Quality Classification

Final Station Rating Station Station Name Number Quality Classification 09001 Leixlip A1

09002 Lucan A1

09010 Waldron’s Bridge A1

09011 Frankfort B

09035 Killeen Road B

09036 Kerdiffstown U

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• A1 sites – Confirmed ratings good for flood flows well above Qmed with the highest gauged flow

greater than 1.3 x Qmed and/or with a good confidence of extrapolation up to 2 times Qmed, bankfull or, using suitable survey data, including flows across the flood plain.

• A2 sites – ratings confirmed to measure Qmed and up to around 1.3 times the flow above Qmed. Would have at least one gauging to confirm and have a good confidence in the extrapolation.

• B sites – Flows can be determined up to Qmed with confidence. Some high flow gaugings must be

around the Qmed value. Suitable for flows up to Qmed. These were sites where the flows and the

rating was well defined up to Qmed i.e. the highest gauged flow was at least equal to or very close

to Qmed, say at least 0.95 Qmed and no significant change in channel geometry was known to occur at or about the corresponding stage.

• C sites – possible for extrapolation up to Qmed. These are sites where there was a well defined

rating up to say at least 0.8 x Qmed. Not useable for the FSU

• U sites – sites where the data is totally unusable for determining high flows. These may be sites with recorded water level only and where it is not possible to record flows and develop stage discharge relationships. Not useable for FSU

Figure 4.1 shows the locations of all 56 hydrometric stations within HA09. The 32 for which data is available are coloured green (water level and flow data), yellow (water level data only) or purple (flow measurements). Those which have additional data from the FSU work, including AMAX series are also highlighted. All 32 stations with data available will be used in the hydrological analysis as appropriate:

• Stations along modelled watercourses with water level and flow data, gaugings and ratings will be used for hydrological and hydraulic model calibration, historical flood analysis and growth curve derivation. • Stations along modelled watercourses with water level data only are also useful in calibration exercises. Recorded water levels are useful in comparing hydraulic model outputs with observed flood events. AMAX series of water levels and derived annual exceedance probabilities can also be useful in hydraulic model calibration of water levels for various design return periods. • Stations with water level and flow data within the wider HA09 area are used in historical flood analysis and growth curve derivation. • Stations which have already been included in the FSU are of benefit to the Study since AMAX series of flows have previously been derived, and quality ratings have been assigned. A range of hydrometric data analyses would have been undertaken at these stations (up until 2004). These stations will also be used in the Study with care taken to ensure all available data, including post 2004 is used.

In addition to the 32 stations within HA09 additional stations outside of the catchment will be used where appropriate to supplement the data from within the catchment. Stations from outside the catchment will be used for the following purposes:

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• Stations elsewhere within the Eastern and South eastern CFRAM Study areas with a sufficient quality of data will be used to form a study specific pooling group from which additional gauge years will be used to provide a sufficient amount of gauge years for pooled flood frequency analysis and growth curve development. • Where small to medium sized catchments (<100km²) are ungauged Pivotal Sites from outside HA09 may be used to transfer data in order to modify regression estimates of the index flood

(Qmed) where the Pivotal Site is found to be sufficiently hydrologically similar as per FSU Work Package 2.3.

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Figure 4.1: Hydrometric Stations in HA09

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4.1.1.1 Hydrometric Stations along modelled watercourses

There are 19 hydrometric stations along the rivers to be modelled as Medium or High Priority Watercourses (MPW or HPW). These are shown on Figure 4.2. 15 of these stations have water level and flow data, whilst four have level data only. Four of these stations were included in the FSU programme which is also indicated on Figure 4.2.

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Figure 4.2: Hydrometric Stations along Modelled Watercourses (HPW / MPW)

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4.1.1.2 Rating Reviews – Eastern CFRAM Study

As a follow on from the recommendations of Work Package 2.1 of the FSU (Reference 5), a task was included in the Eastern CFRAM Study brief to undertake further rating review of a subset of hydrometric stations. This entails using hydraulic modelling techniques to extrapolate rating curves where high flow gaugings are lacking to construct a theoretical rating curve that provides a relationship between stage and discharge for flood flows. Four hydrometric stations have been specified for this analysis within HA09 and are shown in Figure 4.3. The current rating quality classification assigned under the FSU for each station (if available) is stated in Table 4.4.

Table 4.4: Existing Rating Quality Classification for Rating Review Stations in HA09

Station Station Name Final Station Rating Quality Classification Number

09001 Leixlip A1

09002 Lucan A1

09035 Killeen Road B

09102 Cadbury’s NOT REVIEWED UNDER FSU

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Figure 4.3: Hydrometric Stations for CFRAM Study rating review in HA09

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4.1.1.3 Summary of Hydrometric Data

Table 4.5 summaries the number of hydrometric stations with data available within HA09 overall, and those located on modelled watercourses only. Four of these stations require rating review as part of the Eastern CFRAM Study, all of which have water level and flow data available.

Table 4.5: Number Summary – HA09 Stations with Data Available

Data Available HA09 HPW/MPWs CFRAM Rating Review Water Level and Flow 27 15 4 Water Level Only 4 4 0 Flow Measurements 1 0 0 Total 32 19 4

Table 4.6 provides a more detailed summary of the type of data for each of the 32 usable Hydrometric Stations within HA09 that has been collected for the Eastern CFRAM Study. The 19 stations that are located on the watercourses to be modelled are highlighted in blue.

Hydrometric Station Data Status Tables for HA09 are provided in Appendix A.

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Table 4.6: Summary of Hydrometric Data Provision within HA09

FSU Record Rating AMAX Located CFRAM BODY DATA Gaugings Generated NUMBER NAME STATUS Length Info Series on RATING RESPONSIBLE AVAILABLE Provided Data (dates) Provided Provided HPW/MPW REVIEW Provided Office of Public Water Level and Oct 1956 - 09001 LEIXLIP Active Y Y Y Y Y Y Works Flow Feb 2010 South Dublin Water Level and Mar 1977 - 09002 LUCAN Active Y N N Y Y Y County Council Flow Feb 2002 South Dublin Water Level and Nov 1976 - 09005 CLONDALKIN Inactive Y N N N Y N County Council Flow Mar 1984 Water Level and Jan 1967 - 09006 CELBRIDGE ESB Active Y N N N Y N Flow Jan 2007 Water Level and Jan 1950 - 09007 GOLDEN FALLS ESB Active Y N N N Y N Flow Jun 2011 South Dublin Water Level and Nov 1980 - 09009 WILLBROOK ROAD Active Y N N N N N County Council Flow Jun 2011 WALDRON'S Dublin City Water Level and Jan 1986 - 09010 Active Y N Y Y N N BRIDGE Council Flow Jun 2011 Dún Laoghaire - Water Level and May 1982 - 09011 FRANKFORT Active Y N Y Y N N Rathdown Co. Flow Aug 2011 Water Level and Jan 1989 - 09014 BALLYWARD ESB Inactive Y N N N N N Flow Dec 1991 Dept. of ISLANDBRIDGE Water Level Sept 1982 - Agriculture, Food Y N 09015 WEIR Inactive Only Nov 1990 N N N N and the Marine

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FSU Record Rating AMAX Located CFRAM BODY DATA Gaugings Generated NUMBER NAME STATUS Length Info Series on RATING RESPONSIBLE AVAILABLE Provided Data (dates) Provided Provided HPW/MPW REVIEW Provided Kildare County Water Level and Aug 1981 - 09016 ARTHURSTOWN Inactive Y Y N N N N Council Flow Oct 1984 Dublin City Water Level and Jan 1986 - 09019 DRUMCONDRA Inactive Y N N N N N Council Flow Oct 1992 South Dublin Water Level and Feb 1988 - 09021 GLASSAMUCKY Inactive Y N N N N N County Council Flow Oct 1988 LEIXLIP POWER Water Level and Jan 1950 - 09022 ESB Active N N N N Y N STATION Flow June 2011 Kildare County Water Level and Gaps 2002 09024 MORELL BRIDGE Active 2001 - 2011 Y N N Y N Council Flow - 2004 Wicklow County Flow March 1993 09025 BALLINAGEE BR. Inactive Y N N N N N Council Measurements - May 2006 Wicklow County Water Level and April 1992 - 09026 ANNALECKA BR. Active Y Y N N N N Council Flow May 2011 South Dublin Water Level and Jan 2001 - 09027 BROGUESTOWN Active Y N N N Y N County Council Flow May 2011 Water Level Jan 1950 - Gaps 1982- 09032 POLLAPHOUCA ESB Active N N N Y N Only June 2011 1991, 1996 South Dublin Water Level and Mar 1996 - 09035 KILLEEN ROAD Active Y N Y Y Y Y County Council Flow May 2011 Office of Public Water Level AMAX 1994 - Y N 09036 KERDIFFSTOWN Active 2009 Data N Y Y (LEVEL) N Works Only 1950-2010

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FSU Record Rating AMAX Located CFRAM BODY DATA Gaugings Generated NUMBER NAME STATUS Length Info Series on RATING RESPONSIBLE AVAILABLE Provided Data (dates) Provided Provided HPW/MPW REVIEW Provided BOTANIC Dublin City Water Level and Sept 1999 to 09037 Active Y N N N N N GARDENS Council Flow June 2011 Kildare County Water Level and Feb 2009 - 09040 NICHOLASTOWN Active Y N N N N N Council Flow May 2011 OSBERSTOWN Kildare County Water Level and May 2009 - 09042 Active Y N N N Y N HOUSE Council Flow May 2011 KERDIFFSTOWN Kildare County Water Level and Feb 2009 - 09044 Active Y N N N Y N HOUSE Council Flow June 2011 GRAND CANAL Kildare County Water Level Mar 1977 - 09045 Inactive N N N N Y N BRIDGE Council Only Mar 1987 Kildare County Water Level and May 2009 - 09047 BARONRATH Active Y N N N Y N Council Flow June 2011 Kildare County Water Level and May 2001 - 09048 ANNE'S BRIDGE Active Y Y N N Y N Council Flow May 2011 Kildare County Water Level and July 2001 - 09049 MAYNOOTH Active Y N N N Y N Council Flow June 2011 Dublin City Water Level and Aug 2001 - 09102 CADBURY'S Active Y N N N Y Y Council Flow May 2011 Dublin City Water Level and Dec 2007 - 09103 GLENASMOLE Active Y N N N N N Council Flow June 2011 Dublin City Water Level and 09104 FINGLAS WEIR Active 2007 - 2010 Y insufficient N N N N Council Flow

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4.2 METEOROLOGICAL DATA

Meteorological data was provided by Met Éireann through the OPW at the project outset. A gap analysis was undertaken and additional data acquired from Met Éireann directly by RPS. Additional rainfall data was also requested from Local Authorities if available. Further development of the hydrological analysis method required rainfall radar data at Dublin Airport (refer to Section 5.1.3 for detail). Radar data was requested and received from Met Éireann.

4.2.1 Daily rainfall data

Daily rainfall data was received from Met Éireann for a total 565 rainfall gauges both within and beyond the Eastern CFRAM Study Area. Additional information was also provided by Local Authorities for a further 43 stations giving a total of 608 daily rainfall gauges that are available for the Study. At least ten of the gauges operated by Dublin City Council are telemetry gauges with 5 minute interval rainfall readings. As such, subject to further review, they could be of use as sub-daily stations for hydrological input and model calibration. At the time of writing this report, long term time series data has only been supplied for one of these stations (Boherabreena) although continuous rainfall data has been provided for 10 gauges for short (week long) time periods during September and October 2011 when heavy rainfall was recorded. The lack of access to long term records from the majority of the Dublin City Council operated gauges however means it is not possible to determine if all the gauges are suitable for this purpose. Initial information received from South Dublin County Council indicated that SDCC operate 18 rainfall gauges. Following a request for further information continuous time series information was received for nine of these stations. Table 4.7 summarises the number of available daily rainfall stations for the Study.

Table 4.7: Number of Available Daily Rainfall Stations

Provided By: Total

Station Location Met Éireann Local Authorities Within Eastern CFRAM 215 43 258 Study Area Only Within Eastern CFRAM 350 0 350 Buffer Area Only Within Eastern CFRAM 565 43 608 Study Area plus Buffer

258 of the daily rainfall stations are located within the Eastern CFRAM Study Area. An additional 350 are located beyond the Study area boundary as shown in Table 4.7 and Figure 4.4. These additional stations have been included to provide a wide enough rainfall station network for determining the rainfall event input at Hydrological Estimation Points (refer to Section 5.3).

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Figure 4.4: Location of Daily Rainfall Gauges

Within HA09 there are 99 Met Éireann daily rainfall gauges with 36 additional daily rainfall gauges operated by Local Authorities, giving a total of 135 rainfall gauges (eight of these may be used as sub- daily gauges, subject to data review). A 20 – 30km buffer will also be applied to this area and the surrounding rainfall gauges within the buffer zone will also be included in rainfall spatial analysis. This will be decided on a case by case basis depending on the spatial analysis requirements towards the boundary of the Study area.

A data status table has been compiled for all daily rainfall stations as shown in Appendix B. This table shows the time line over which daily rainfall data is provided for each station.

4.2.2 Hourly rainfall data

Data for a total of 13 hourly rainfall stations as shown in Figure 4.5 was also provided by Met Éireann. Three of these stations are within HA09. Information on the length of the records for each hourly rainfall gauge is provided in Appendix B. As discussed above, eight Dublin City Council gauges may also be used as sub-daily gauges (with five minute readings) if it is confirmed that long time series data is available.

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Figure 4.5: Hourly Rainfall Gauges

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4.2.3 Rainfall Radar Data

A data collection meeting held at the beginning of the ECFRAM Study (between RPS, HydroLogic, OPW and Met Éireann) identified an opportunity for exploring the use and benefits of rainfall radar data in hydrological analysis. The data collected is as follows:

• Hourly precipitation accumulation (PAC) data of the Dublin radar on a 1 x 1 km grid (from 1997)

• 15 minute Pseudo-CAPPI (PCR) data of the Dublin radar (from 1997)

• Plan Position Indicator (PPI) data of the Dublin radar (from 1997)

If following the trials on the use of the rainfall radar data it is decided not to use it then hydrological input data for rainfall run-off modelling will be taken from the rainfall gauge stations only.

4.3 HISTORICAL FLOOD EVENTS – SOURCES OF INFORMATION

The following sources of information were consulted as part of the historical flood data assessment: -

Office of Public Works (OPW) National Flood Hazard Mapping

The OPW National Flood Hazard Mapping website http://www.floodmaps.ie contains information on flood events that occurred within HA09. The information available includes Local Authority flood records, OPW Flood Event Reports, press articles and consultants flood study reports.

The information can be searched for and downloaded in a number of ways (e.g. by location, by date, by catchment name and river name). To ensure all available information was downloaded for review, the website was searched firstly by catchment name, and each catchment was in turn searched according to river name. In the case of HA09, there are eight separate catchments in the hydrometric area. Searches were carried out for each of the rivers in the catchment as follows:

Catchment River

• Coastal (Clontarf) - • Coastal (Dun Laoghaire) - • Coastal (Howth) - • Coastal (Portmarnock) - • Liffey catchment Annalecka (Brook) Ballydonnell (Brook)

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Ballylow (Brook) Brittas Camac Clonshanbo Cock (Brook) Dodder (includes Little Dargle, Owendoher, Slang and Whitechurch) Douglas [Liffey] Glashnaboy (Brook) Kilcullen (Stream) King's [Liffey] Lemonstown (Stream) Liffey Lyreen Rye Water • Mayne catchment Mayne • Santry catchment Santry • Tolka catchment Pinkeen Tolka

Internet Search Engines

The search carried out on the OPW National Flood Hazard Mapping website yielded details of flood events up to, and including, November 2009. No details of more recent flood events were returned.

A wider search for information on more recent flood events, in particular the October 2011 event, was carried out for each AFA in HA09 using internet search engines. While a number of results were yielded, these were generally news reports, photos or press articles which contained details of affected areas and damage done, but contained few details on flows, flood extents, flood return periods, etc. Some Development Plans were found also but again, these generally contained only general information on flooding.

4.3.1 Hydrometric Data

In conjunction with historical data researched as described above, hydrometric data from the Environmental Protection Agency (EPA) Hydronet website (http://hydronet.epa.ie) and the OPW Hydro- Data website (http://www.opw.ie/hydro) were consulted, where available. These websites include data

IBE0600Rp0008 67 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL such as recorded water levels and corresponding flow rates, quoted as mean daily flows in some instances and peak flows in other instances. This data was used to verify and supplement the historical data, such as dates of floods, river levels and flows.

In the case of HA09, hydrometric stations are located at Leixlip, Celbridge, Maynooth, Turnings, Lucan and Santry, with a number of others located in the Greater Dublin area as depicted on Figure 4.1.

4.3.2 Historical Flood Events

4.3.2.1 Summary of Historical Flood Events

Based on a review of the information outlined above, the historical flood events which occurred in the various AFAs in HA09 are summarised in Table 4.8 below and discussed in the following sections:

.

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Table 4.8: Summary of Historical Flood Events for each AFA

Event Naas North Clane Clane Leixlip Leixlip Santry Dublin Kilcock Raheny Raheny Lucan to Sutton & Baldoyle Turnings Turnings Celbridge Celbridge Maynooth Baldonnel Park HPW Newbridge Newbridge Hazelhatch Chapelizod Robinhood/ Robinhood/ Blessington Sandymount Poddle/ Tymon SuttonHowth & Ballymount HPW

Oct-2011 Nov-2009 Jul-2009 Aug-2008 Jul-2007 Jan-2005 Oct-2004 Aug-2004 Dec-2003 Nov-2002 Oct-2002 Feb-2002 Nov-2000 Sep-1999 Apr-1998 Feb-1994 Jun-1993 May-1993 Aug-1986 Aug-1984 Nov-1982 Nov-1968 Nov-1965

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Event Naas North Clane Leixlip Leixlip Santry Dublin Dublin Kilcock Kilcock Raheny Raheny Lucan to to Lucan Sutton & Baldoyle Turnings Turnings Celbridge Celbridge Maynooth Maynooth Baldonnel Park HPW Newbridge Hazelhatch Chapelizod Robinhood/ Blessington Sandymount Poddle/ Tymon SuttonHowth & Ballymount HPW Ballymount HPW

Jan-1965 Jun-1963 Dec-1958 Feb-1958 Sep-1957 Dec-1956 Dec-1954 Sep-1946 Aug-1946 Jan-1941 Sep-1931 Nov-1915 Aug-1912 Apr-1909 Aug-1905 Nov-1901 Nov-1898 Nov-1891 Nov-1886 Nov-1880

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4.3.2.2 Flood Event of October 2011

The floods that hit Dublin, Wicklow and parts of Kildare in October 2011 resulted from extremely heavy rainfall. The floods, which resulted in the deaths of two people, affected mainly the city, south Dublin and Wicklow.

In the city area, 1,190 properties were flooded and a further 318 significant road flooding incidents occurred with several thousand reports of minor road flooding. Anecdotal information from the internet described that the main flooding was caused by culvert capacity being exceeded, and drains and small rivers overflowing. The River Liffey did not flood to a significant degree due to the Pollaphuca and Golden Falls reservoirs controlling the flow rates. The Camac River caused flooding in and the Poddle River affected Crumlin. Also, the Swan River caused flooding in Ballsbridge, the River Bradogue in Cabra and the River Naniken in Raheny. Data available on the EPA Hydronet website, http://hydronet.epa.ie, indicated that the daily mean flow rate of the River Dodder was measured to be 51.472m3/s at Waldron's Bridge Hydrometric Station with the River Tolka measured to be 31.705m3/s at Botanic Gardens Hydrometric Station. The maximum daily mean flow rates on record on the EPA Hydronet website for the Dodder and Tolka Rivers at said locations are 109.258m3/s (August 1986) and 75.679m3/s (November 2002) respectively.

It was reported that up to 90mm of rain fell during six hours on the evening of 24 October, which is more than four times the level associated with the country's heaviest rainfall. In the city centre, there was flooding in , Kimmage, , Kilmainham, Harold's Cross, Dolphin's Barn, , Harrington Street, Harcourt Road and South Richmond Street. Carysfort Avenue in Blackrock was described as almost impassable due to severe flooding while heavy rain is also reported in nearby Monkstown and in Tallaght. Dundrum Town Centre was evacuated at around 8pm after the Level 1 Mall flooded with up to 10cm of water. Mobile network O2 confirmed that heavy rain in the Dublin region caused disruption to mobile services with many customers experiencing "patchy service" and in some cases no service at all. DART services were disrupted for a time and Commuters were also affected by disruptions with services cancelled for a while. The ESB reported that around 1,200 customers in Dublin city centre and south Dublin had no power supply. In most of these cases, the supply had been cut as a safety precaution due to flooding, and was restored when floodwaters receded. ESB crews worked through the night to address supply issues. Eircom reported around 6,000 faults in the Dublin area due to the inclement weather conditions and had to work around the clock to restore services as quickly as possible to affected customers.

Flooding occurred in several areas of Lucan, particularly around Esker Lane and Ballyowen Lane. Strawberry Beds was impassable and the Lower Lucan Road was closed between Lucan Bridge and Tinkers Hill. The N4 was closed to all inbound traffic from the M50 at Junction 7 (Lucan/Palmerstown). Surface water/flooding caused traffic delays on the Chapelizod by-pass and it was reported on an internet site that Parkgate Street along the Cunningham Road to Chapelizod was heavily flooded and sections of St. Laurence’s Road in Chapelizod were also flooded.

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The rainwater caused damage at a cemetery at St. Mary's Church in Howth. All Northern Commuter Services were cancelled due to a major signal fault at Howth Junction. Howth Post Office was also affected by flooding.

Along the Poddle HPW (High Priority Watercourse), the flooded the entrance and basement of Our Lady's Hospice at Harolds Cross. Numerous premises in Harold's Cross were severely damaged by the flooding especially Greenmount Avenue and Boyne Court Apartments. A woman was drowned when her basement flat on Parnell Road, Harold’s Cross, in which she was trapped in, filled with flood water. Crumlin was also badly hit as the river burst its banks at Ravenscourt Park.

Santry Village and Santry Avenue were impassable due to large amounts of rainfall and there was also flooding on the N11 at Santry. No details were found on any damage caused.

In Naas, flooding affected the M7 at Citywest to Naas and the N7/Naas Road was also impassable in both directions at Junction 6 Castlewarden.

The RTÉ website (http://www.rte.ie/news) reported how Robinhood Road was closed due to flooding in October 2011 but no other details were provided.

In Blessington, the Wicklow Gap was closed and Gardaí advised motorists not to use the Sally Gap and roads to and Lacken. Roads were also impassable throughout Blessington Village. An off-duty Garda died after he was swept away in floods when attempting to direct traffic away from Ballysmuttan Bridge, near Blessington.

Full details of the October 2011 flood event will be presented in the Flood Event Reports, which are still being finalised at the time of drafting of this Inception Report.

4.3.2.3 Flood Event of November 2009

The review indicated that flooding occurred in parts of Kildare and Dublin in November 2009 following heavy rainfall.

In Clane, the flooding was caused by the River Liffey and Butterstream overflowing, coupled with the inability of the local drains to convey the floods. The Hazelhall Nursing Home on Prosperous Road required evacuation. Sandbags were needed at Butterstream housing estate; however Loughbollard and Cois Aoibhinn estates were flooded with sewage in the floodwaters. Millicent and Prosperous roads were also flooded and the rural area of Loughanure was entirely blocked off.

In Newbridge, some parts of the town were impassable but no details were given relating to any damage caused.

In Dublin, a press article describes how the River Liffey burst its banks at several locations, including at Strawberry Beds. Roads were closed at Strawberry Beds, Lower Road and Tinkers Hill in Lucan.

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However, no additional information on flood flows, extents or levels were provided. Two houses were flooded in Chapelizod and 30 vehicles written off. Flooding was also reported at Crescent, Finglas, Glendhu Park and a number of locations in Cabra. The daily mean flow rate of the River Dodder was measured to be 20.248m3/s at Waldron's Bridge Hydrometric Station with the River Tolka measured to be 19.183m3/s at Botanic Gardens Hydrometric Station according to data from http://hydronet.epa.ie. DCC also reported that the peak flow in the Liffey at Chapelizod was around 200m3/s.

4.3.2.4 Flood Event of July 2009

Flooding occurred on July 2nd after several hours of heavy rainfall in the Dublin area from midnight to 9.00am. 38.2mm of rain fell at Dublin Airport over 9 hours, with 26.5mm falling in one of those hours.

Many parts of Dublin were adversely affected by the flooding. The Clanmoyle Road in Donnycarney was flooded as was the Kill Lane and Rock Road in . Road in also experienced flooding as did Collins Avenue East in and Road. The area of Drumcondra was one of the worst affected areas with Sherrard Street, Collins Avenue, Richmond Road and Botanic Avenue flooded. Sections of the Coast Road from Howth to Dun Laoghaire along with sections of the Howth Road, the M50 Southbound at Junction 12 and the N11 Southbound before were also flooded. The EPA Hydronet website, http://hydronet.epa.ie, outlines that the daily mean flow rate of the River Dodder was measured to be 4.827m3/s at Waldron's Bridge Hydrometric Station with the River Tolka measured to be 4.783m3/s at Botanic Gardens Hydrometric Station.

The flooding was not so severe in the Santry area with the main flooding problem being surface water on roads in the vicinity. According to EPA Hydronet website, http://hydronet.epa.ie, the daily mean flow rate of the River Santry was measured to be 1.52m3/s at Cadburys Hydrometric Station. The maximum daily mean flow rate for the River Santry at this location is 3.31m3/s and was measured in November 2002. However, there was no further information on the extent of the flooding or details of any damage caused by the July 2009 flood event.

4.3.2.5 Flood Event of August 2008

The historical data indicated that flooding occurred in Co. Kildare in August 2008 as a result of heavy and prolonged rainfall.

Met Éireann recorded 81.6mm of rainfall at the Celbridge station in the 24-hour period from midnight Friday 8th August until midnight on Saturday 9th August, which was a record for the station. Flooding in the Celbridge area was caused by the Toni River, a tributary of the Liffey, backing up. Eight houses in the Vanessa Close Estate were damaged by this flooding with water reaching about 0.60m. Some roads were also impassable, namely the Clane to Celbridge Road and Ardrass Road from Straffan to Celbridge. Sewage flooded onto the streets, as a result of pumps being flooded.

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The extent of the flooding in Leixlip is somewhat unclear with the only available information being photographs, which indicate flooding of land and some properties in the area. The peak flow of the River Ryewater for the flood event in August 2008 was measured to be 65.5m3/s at Leixlip Hydrometric Station as per the OPW hydrometric website “http://www.opw.ie/hydro”. This flow was the annual maximum for 2008 and also significantly greater than the annual maxima for most years on record. As a means of comparison, the greatest peak flow on record on http://www.opw.ie/hydro was 91.5m3/s, which was measured in November 2002.

No details were available relating to any damage caused in Maynooth as a result of the August 2008 flood event. The daily mean flow rate of the River Lyreen (as per http://hydronet.epa.ie) was measured to be 49m3/s at Maynooth Hydrometric Station, and is also the maximum daily mean flow rate on record for the River Lyreen at this location.

Flooding occurred in Newbridge and reports indicate that it was caused by the inability of culverts and drains to handle the floodwaters. There was damage caused to at least nine houses in the Kilbelin area as a result of the flooding.

In Kilcock, adjacent lands and roads were flooded and sandbags were needed to protect buildings. The extent of the flooding is visible in photographic format. The daily mean flow rate of the River Ryewater was measured to be 25.1m3/s at Annes Bridge according to http://hydronet.epa.ie, and is also the maximum daily mean flow rate on record for the River Ryewater at this location. No further information was available in relation to the damage caused.

Flooding was also reported at Ballygall Crescent, Finglas, Glendhu Park, Blackhorse Avenue and a number of locations in Cabra.

4.3.2.6 Flood Event of January 2005

Kilcock and Dublin endured floods in January 2005 following heavy rainfall.

In Kilcock, the Newtown Prospect area was particularly affected with land and roads being flooded. The extent of the flooding is visible in photographic format. The EPA Hydronet website, http://hydronet.epa.ie, outlines how the daily mean flow rate of the River Ryewater was measured to be 24.8m3/s at Annes Bridge, and is close to the maximum daily mean flow rate on record of 25.1m3/s at this location. No further information was given in relation to the damage caused.

In Dublin, there was no report of any damage caused as a result of the flooding. However, details of the River Tolka flow at the Botanic Gardens Hydrometric Station are available with a peak flow of 38.85m3/s for this flood event as per the EPA Report entitled "Flooding in the Tolka Catchment 8 January 2005" (Reference 6)

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4.3.2.7 Flood Event of October 2004

Flooding occurred in Dublin in October 2004 as a result of high tides and strong easterly winds.

In the Clontarf area of Dublin, floods were caused by the 3rd highest tidal level (2.62mOD Malin Head) recorded since records began at Dublin Port Station, Alexandra Basin. Strong easterly winds resulted in waves with amplitude of 1.5-1.8m. These waves overtopped the sea wall and flooded a number of properties in Clontarf, as shown on a Dublin City Council Map. As per http://hydronet.epa.ie, the daily mean flow rate of the River Santry was measured to be 1.3m3/s at Cadburys Hydrometric Station, with the maximum on record being 3.31m3/s for a November 2002 flood event.

Lower Lucan Road/Strawberry Beds were impassable in the Lucan to Chapelizod region. This was due to surface water from Powerstown/Luttrelstown Golf Club unable to exit as a result of a blocked drainage pipe.

4.3.2.8 Flood Event of August 2004

The Clontarf area of Dublin experienced flooding in August 2004 as a result of heavy rainfall which exceeded a 3.33%AEP rainfall event. (28mm of rainfall was recorded at Kindle Banking during a 78 minute period, with 26mm of this falling in 50 minutes.) Approximately 113 no. properties were flooded, the exact locations of which can be seen on a Dublin City Council Map. No further details were available on the damage caused.

4.3.2.9 Flood Event of December 2003

The historical data indicated that flooding occurred in the Dublin region in December 2003. The River Dodder was the source of flooding. At the time, Dublin City Council was commissioning a new spillway on the lower reservoir. The temporary works were constructed near the old spillway of the lower reservoir.

All water from the Upper Dodder Catchment enters the upper reservoir from where it is discharged to the lower reservoir upon filling. The temporary spillway on the lower reservoir could not hold the floodwaters that occurred on this date, therefore causing flooding of the surrounding areas. No further information was given in relation to any damage caused. However details of the River Dodder flow at Waldron’s Bridge Hydrometric Station were available in the EPA Report entitled "Flooding in the Dodder Catchment 2 December 2003" (Reference 7) indicating a peak flow of 112m3/s for this flood event.

4.3.2.10 Flood Event of November 2002

Widespread flooding occurred in mid November 2002 as a result of heavy and prolonged rainfall. The rainfall event had a return period of approximately 50 years. Flooding was severe in some parts as the catchments were already somewhat saturated, following high levels of rainfall in October and early

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November. The total rainfall depth measured at Dublin Airport during this event was 87mm, while 72mm of rainfall was recorded at Casement.

In Dublin, the Tolka, Broadmeadow, Liffey and Mayne Rivers all burst their banks with the Santry River backing up and overflowing due to an overwhelming of a culvert on the river at the Old Swords Road. Drumcondra, Ballymun, Santry and were reported to be the worst hit as a result of the flooding. Roads were also flooded in the Swords, Chapelizod Village, Knockmaroon Hill, Donabate, Lusk, Strawberry Beds, Lucan and Glasnevin areas. The ESB substation on Duke Street was flooded causing power cuts to over 100 shops and businesses around . The North Quays were also closed, as was the M50 at the N3 junction. The N3 itself was partially flooded along with the N2, Malahide Road, Forest Road and N1 junction at Turvey Avenue. The areas adjacent to the Tolka River between Finglas Road and Fairview also experienced flooding. Houses in Lucan, Chapelizod and were affected by the flooding with surface water in many other areas. The peak flow for this flood event at the Botanic Gardens Hydrometric Station was 97m3/s for the River Tolka in accordance with the EPA Report entitled "Flooding in the Tolka Catchment 8 January 2005" (Reference 6) and 5.8m3/s for the River Santry at Cadbury’s Hydrometric Station as discussed in the EPA Report entitled "Flooding in the Santry Catchment 14 November 2002, 20-21 October 2002 & 28 October 2004" (Reference 8).

The Strawberry Beds road to Lucan was closed due to flooding. Houses were flooded in Lucan and Chapelizod with Chapelizod Village itself impassable. The EPA Report entitled "Selected Floods in the Griffeen Catchment" (Reference 9) indicated that the River Griffeen at Lucan Hydrometric Station yielded a peak flow of 12m3/s but no additional information is provided.

The surface water culvert at the Bloody Stream Pub in Howth was surcharged and in danger of flooding the pub. A pump was provided to keep the level in the culvert down. In Santry, high water levels in the River Santry contributed to the flooding which occurred at Santry Close, on the Old Airport Road.

In Celbridge, the Clane and Ardclough Road were both flooded as was the junction between Oldtown Road and Main Street at the mill. Three properties were also affected by the floods. It is reported that flooding was a result of the River Liffey overflowing. No further details were available on any damage caused.

Heavy rainfall on the 13th and 14th of November caused flooding in the Leixlip area with rainfall levels of 22.5mm and 51.5mm respectively measured at Leixlip Station. This led to the Ryewater River overflowing its banks due to an estimated 2%AEP flow. The OPW Hydrometric website, http://www.opw.ie/hydro, indicated a peak flow of 91.5m3/s for the Ryewater River at Leixlip Hydrometric Station. The River Liffey also overflowed due to insufficient capacity for flood flow at Barnhall Road Bridge. Roads were flooded at Mill Lane, Buckley's Lane, Allenswood Road, Kellystown Lane, Barnhall Road Bridge, Confey Junction with Allenswood Road, Shaughlins Glenn and Confey

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Road. The ground floor of the Rye River Apartments was affected by the floods as were approximately ten houses at Duncarrig & Mill Lane.

Maynooth experienced flooding in many parts as a result of the heavy rainfall in November 2002. A ditch on Moyglare Road was blocked and flooded, as was a pipe on Laurence's Avenue. Some roads flooded including the N4/M4, Moyglare Road, Road, Kilcock Road and Laurence's Avenue. Sandbags were distributed throughout the area thereby reducing the damage caused to houses.

A number of roads were flooded in the vicinity of Kilcock including the M4 and N4. The Clane Road out of Kilcock was also flooded where a number of cars were stranded and passengers required rescuing. Aerial photos are available which display the extent of the flooding but no additional information is provided in relation to any damage caused.

The Clane area was also affected by the excessive rainfall where the sewage pumping station was flooded. The Clane-Celbridge road and Clane-Maynooth road were also impassable as was Clane village. Sandbags were needed to protect properties in the vicinity.

Flooding of land and a number of properties occurred at Turnings due to the extensive rainfall. There are photos available displaying the extent of the flooding and flood levels near weirs on the Morell River and Painestown River. No further information was given in relation to any damage caused. However, details of the River Morell flow at Morell Bridge Hydrometric Station were available on http://hydronet.epa.ie, with a daily mean flow rate of 33.7m3/s.

4.3.2.11 Flood Event of October 2002

Flooding occurred in Dublin in October 2002 as a result of heavy rainfall. Reports indicate that the flooding was primarily of a surface water nature due to an overwhelming of sewers at Swords, Malahide, Portmarnock, Kinsaley, Howth, Baldoyle, Skerries and Sutton areas. No further information was provided relating to any damage caused.

In Howth, The Bloody Stream Pub was flooded with surface water from an adjacent manhole entering the pub on the night of 21st October. The Techrete Yard, which is located close to The Bloody Stream Pub, was flooded as a result of a surcharged surface water line. The Gem Shop on Harbour Road was also flooded as a result of a combined sewer becoming surcharged.

4.3.2.12 Flood Event of February 2002

The historical data indicated that flooding occurred in Dublin in February 2002 as a result of heavy rainfall and an exceptionally high tide.

Around Dublin, the tidal flooding caused an increased water level in rivers and resulted in the Rivers Liffey, Dodder, Tolka and the Royal Canal all bursting their banks. Power cuts occurred due to flooding of ESB substations at Clontarf, Ringsend and East Wall. A large number of houses in the Ringsend

IBE0600Rp0008 77 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL and Irishtown areas were affected by the floods with three people hospitalised and over 100 residents evacuated from their homes. The Clontarf Road, Merrion Gates, Strand Road, North & South Quays and East Link Bridge were also flooded. Public transport networks were disrupted with the DART closed between Lansdowne Road and Dun Laoghaire. A report entitled “Dublin Coastal Flooding Protection Project (DCFPP) Final Report” (Reference 10) by Royal Haskoning outlined peak flows of 10.5m3/s for the River Dodder at Waldron's Bridge Hydrometric Station and 8.26m3/s for the River Tolka at Botanic Gardens Hydrometric Station. A Dublin City Council Report entitled "Flood 2002, Interim Assessment Report" (Reference 11) indicated that the tide level of 2.95mOD (Malin) was the highest reading on record and was higher than the flood of 1924, when the previous highest tide at Dublin Port was recorded.

In Sandymount, high water levels combined with wave activity to cause tidal flooding of Marine Drive and Drummond Avenue. Roads were flooded to depths of about 600mm and approximately 20 properties were flooded. The majority of Beach Road and Strand Road was also flooded, as was the North Eastern corner of Sandymount Green, affecting 3 shops.

Flooding also occurred in the Sutton and Baldoyle Area on 1st February 2002. In Sutton, flooding was noted on Burrow Road in the region of the Avalon Apartments where a number of gardens were flooded. Sutton Dinghy Club also suffered extreme flooding following the collapse of a wall. On Strand Road, Properties No. 1 - 18 had their gardens flooded with Property No. 1 internally flooded also. The property opposite the Church on Greenfield Road was flooded after a sea wall at the rear of the house was destroyed. In Baldoyle, No. 1 & No. 2 on Coast Road were completely flooded in the space of ten minutes as the tide came in and partially flooded the houses.

4.3.2.13 Flood Event of November 2000

Extensive flooding occurred throughout large parts of Dublin and Kildare in November 2000 as a result of heavy rainfall, high tides and strong winds.

In Dublin, 78.3mm of rainfall was recorded at Dublin Airport over a period of 40 hours beginning at 8.00am on 5th November, with 95.3mm of rainfall measured at Casemont Aerodrome, Baldonnel for the same period. The Griffeen, Poddle, Dodder, Tolka and Liffey Rivers all overflowed their banks with coastal flooding also occurring at Portmarnock, Clontarf, and Dun Laoghaire. Businesses and commercial properties in Lucan town centre were flooded with roads impassable to most vehicles. Other road closures occurred in Milltown, Merrion Gates, Chapelizod, Drumcondra, Finglas, Cabra and Edmonstown. The Tallaght Bypass, Clontarf Road, Howth Road, Malahide Road, Tallaght to Road, N1 at Blakes Cross and Turvey Avenue, N2 at Cool Quay/Ward Road, R109 at Lucan, N3 near and the R128 at Lusk were also affected by the flooding. Properties were hit by the floods in areas such as Drumcondra, the Dodder area, Chapelizod, Kimmage, , Swords, and Lucan. Other properties affected by flooding were located in Sherriff Street, Abbey Street, Pinebrook/Hartstown and Bremore Court. Such was the extent of the flooding in Drumcondra that homes needed to be evacuated. The peak flow of the River Tolka for this flood event

IBE0600Rp0008 78 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL at the Botanic Gardens Hydrometric Station was 76m3/s as reported in the RPS MCOS Report entitled “River Tolka Flood Study Technical Report Volume 2 River Modelling Report” (Reference 12). With regard to the River Dodder, a peak flow of 155m3/s was measured at Waldron’s Bridge Hydrometric Station as discussed in the ESBI report "River Liffey Flood of November 2000" (Reference 13).

In the Lucan/Chapelizod area, the River Griffeen broke its banks in Vesey Park, both upstream and downstream of the pedestrian bridge and the River Liffey also burst its banks. The Ballyowen Road and Peamount Road in Lucan were closed as a result, as was the Strawberry Beds Road to Lucan. Approximately twelve commercial properties were flooded in Lucan village and houses were flooded in Grange Manor and Old Forge Estate. Chapelizod Village was also impassable with Knockmaroon Hill closed completely. One house and garage were flooded on St. Martin's Row and sandbags were also deployed to St. Martins Row.

Flood waters from the River Poddle overflowed into homes around Mount Carmel in Kimmage. Flooding occurred of 'Motorworld' at Robinhood Industrial Estate and adjoining premises, near the Robinhood stream.

In Celbridge, approximately 56mm of rainfall fell on Sunday 5th November and 19.1mm fell on Monday 6th November causing the level of the River Liffey to reach that of the pedestrian bridge. The Clane Road, Ardclough Road and some minor roads in the vicinity were impassable due to the floods while sandbags were distributed to minimise flooding of properties. Flooding of a pumping station also occurred and one house was affected by minor sewage flooding. Photographs are available displaying the extent of the damage in the Celbridge area.

In Leixlip, the Ryewater and River Liffey overflowed their banks causing the adjoining areas to flood. Records indicate that 103mm of rain fell in the area over the 48 hour period encompassing the 5th and 6th of November. A 3.33%AEP flow was estimated for the Ryewater and a 4%AEP flow was estimated for the River Liffey. The flood levels measured on the Ryewater were 29.47mOD Malin and the highest recorded in 45 years of record (prior to 2002). The damage was not too severe however, with only Confey College flooding and minor roads impassable. No data was provided documenting any further effects, however details of the river flow rates were available with the Ryewater River yielding a peak flow of 81.8m3/s as per “http://www.opw.ie/hydro”. The rate of inflow of the River Liffey to Leixlip Reservoir was measured at 98m3/s in the ESBI Report entitled "River Liffey Flood of November 2000" (Reference 13) and consisted of approximately 83m3/s natural inflow and 15m3/s from Golden Falls.

The high levels of rainfall adversely affected Maynooth in November 2000 causing the Royal Canal, Meadowbank Stream and Lyreen River to burst their banks. The lack of capacity of the Railway Culvert on the Lyreen River caused the Treadstown Road, Railway Line (at Jackson's Bridge) and surrounding lands to flood. Lands adjacent to the Ryewater River were also flooded. Damage to houses was limited through the distribution of sandbags which were used to divert floodwaters. However, flooding did occur in Meadowbrook estate with approximately 40 houses affected and also

IBE0600Rp0008 79 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL on Parson Street where eight houses were flooded. The N4 and Clane-Maynooth road were closed due to the floods, as were many streets in the Maynooth area and a local pumping station was also inundated by floodwaters. No details were available on return period or flows for this flood event.

The historical data indicated that Newbridge needed sandbags distributed in order to minimise the damage to local houses. A nearby sewage pumping station overflowed into the Liffey. However, no further information was provided in relation to any damage caused.

In Kilcock, many roads surrounding the town were affected by flooding as a result of the inclement weather conditions. The M4 flooded between Kilcock and Leixlip as did the Summerhill to Kilcock Road. The N4 was also impassable between Maynooth and Kilcock. Photographs are available outlining the extent of the flooding of the area. Similar to Newbridge, no additional details on the flood event were provided.

The Turnings area experienced difficulties as a result of the November 2000 flood event with land, dwellings, outhouses and workplaces all affected by flooding. Aerial photographs were found showing the extremity of the flooding surrounding Turnings and beyond.

Sandbags were distributed to the Hazelhatch area by the Civil Defence due to the high level of the River Liffey. Up to 3,000 rail passengers were hit by travel chaos as the flooding at Hazelhatch caused cancellation of rail services between Cork and Dublin.

4.3.2.14 Flood Event of September 1999

The review indicated that parts of Hazelhatch were affected by flooding in September 1999. The River Road flooded to depths in excess of 500mm and was impassable for some time. Hazelhatch Road also flooded to depths varying from 100mm to 300mm, although it was not closed to traffic. Up to six houses on Hazelhatch Road were surrounded by water but were not affected by internal flooding.

Celbridge Tennis Courts were inundated with silt deposits causing damage. The Celbridge G.A.A. clubhouse car park and football pitch were inundated with floodwaters. No further details of the flood event were provided.

4.3.2.15 Flood Event of April 1998

Flooding of properties and agricultural land occurred in Celbridge and Hazelhatch in April 1998.

An Agricultural Report on Flooding on the land of Stud farm at Commons Upper, Ardclough, Co. Kildare states that poor drainage capacity in a tributary of the River Liffey causes flooding of lands in the area. Homes were also flooded on Hazelhatch Road, as was the Celbridge Tennis Club and Celbridge G.A.A. club. The flooding was caused by an overflow on the Grand Canal, some 1,200 yards north of the Hazelhatch Bridge. No additional information relating to any damage caused is provided.

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4.3.2.16 Flood Event of February 1994

The Dublin area experienced flooding in February 1994 as a result of heavy rainfall.

The River Liffey overflowed causing flooding in the Clondalkin area. The worst affected areas were the Cherrywood Grove Playing Fields as well as the field above Kavanagh's Bridge.

There was also flooding in the Dun Laoghaire Rathdown area. However, this was caused by surface water and foul sewer problems as opposed to those associated with a river. Many premises in this region were flooded including back gardens and adjacent roads.

4.3.2.17 Flood Event of June 1993.

Widespread flooding occurred across Dublin, Kildare and Wicklow as a result of prolonged rainfall beginning on Friday 11th June and lasting for over two days.

The flooding was severe in the Dublin area following extremely heavy rainfall. The 12-hour rainfall had an AEP of 1% at Baldonnel Station while the 24 hour rainfall total had an AEP of 0.4% (further details on recorded rainfall amounts at various locations are available in an ESBI report – Reference 14). The total rainfall at some of the Dublin and Kildare rain stations were the highest recorded and even exceeded Hurricane Charlie in August 1986.

Trains were prevented from leaving Heuston Station and a number of properties in the Dun Laoghaire Rathdown area were affected by flooding. The burst its banks at a number of locations causing flooding of private property in the Clondalkin area at Leinster Terrace, Old Nangor Road and Cherrywood Estate. Traffic had to be diverted in Raheny as a result of the Main Coast Road closing at St. Anne’s Park, whilst Howth was without electricity for a time as a result of a power-cut. At Lucan, the River Liffey overflowed its banks and a 6 acre field of potatoes, which had cost £1,000 per acre to plant, was swept away. The flood event resulted in a fatality in Baldoyle where a 14-year-old boy died after falling into a trench at Admiral Park, Willie Nolan Road. The River Dodder yielded a peak flow of 66m3/s for the flood event at Waldron’s Bridge Hydrometric Station as per the ESBI Report entitled "River Liffey Flood of June 1993" (Reference 14).

The Baldonnel area was also affected by the River Camac overflowing. Roads and houses were flooded in Rathcoole and Saggart.

In Raheny, No. 5 Park, Raheny, Dublin 5 was badly damaged and owners were obliged to vacate it for a period of two months. The flooding was a result of a water drainage problem which surrounds Balgriffin Park.

The River Poddle also burst its banks in June 1993; however no additional details on any damage caused was available.

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The heavy rainfall caused flooding in Celbridge with 58.9mm of rain falling in 24 hours from 09.00 on 11th June to 09.00 on 12th June. The River Liffey overflowed its banks as a result causing areas between Sallins and Celbridge to be underwater for most of the weekend. The peak flow of the River Liffey at the Celbridge Gauge was estimated to be 143m3/s as per the ESBI Report entitled "River Liffey Flood of June 1993" (Reference 14).

Both the River Liffey and Ryewater River overflowed their banks in the Leixlip area causing lands in the adjacent area to flood. No information is provided in relation to any damage which may have been caused though. The OPW website, http://www.opw.ie/hydro, states that the maximum flow of the Ryewater at Leixlip Hydrometric Station was 60.7m3/s.

In the Maynooth area, a culvert on the Lyreen River near Jackson's Bridge (crossing under railway line and Royal Canal) lacked capacity and caused flooding of farmland both upstream and downstream of the culvert. No additional information was provided, however photographs are available displaying the extent of the flooding.

Naas was also affected, with homes flooded in Roselawn estate, in Millbrook and Mountain View estate.

Farmland in the Newbridge vicinity was flooded to a height of over 1.2m and there was 200-250mm of water on roads at Athgarvan near Newbridge.

Mainline trains stalled at Hazelhatch and Irish Rail organised a bus substitution from Heuston to Kildare as a result of the flood event.

Blessington was also affected with the Bishopshill Road, which is the back route from Ballymore Eustace to Blessington, closed for a while after severe flooding resulted in a total road blockage. 70.2mm of rainfall was observed on 11/12th of June in Blessington, which is 105% of the monthly average, but no further details are provided.

4.3.2.18 Flood Event of August 1986

Hurricane Charlie occurred on 25/26th August 1986 and was deemed exceptional with large rainfall totals accompanied by strong to gale force winds.

In Dublin, approximately 100.8mm of rain fell in Saggart over 24 hours, which corresponds to a 1% AEP event. The heavy rainfall resulted in high river flows, with an estimated AEP of 0.6% for the River Dodder at Bohernabreena Gauge. Houses were flooded in , on Lansdowne Road and also in Churchtown while residents in Killinarden Estate in Tallaght had their homes flooded to the first floor level. In total, approximately 465 properties were flooded (340 by the Dodder, 85 by the Poddle, 30 by the Camac, 10 by the Tolka) and 100 properties in Ballsbridge required evacuation. Roads were flooded in the Ballsbridge area, namely Ballsbridge Avenue, Beatty's Avenue and Anglesea Road. The Lower Dodder Road, Road and Nutgrove Road were flooded in the Rathfarnham area

IBE0600Rp0008 82 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL with the Tallaght bypass and Jobstown Road flooded in the Tallaght area. Parnell Road and were also flooded. A number of maps and photographs were found which outline the extent of the flooding. The River Dodder yielded a peak flow of 200m3/s for this event at Waldron’s Bridge Hydrometric Station as outlined in a report presented by An Foras Forbatha entitled “Hurricane Charlie An Overview Activites of An Foras Forbatha” (Reference 15), however this estimate has been revised upwards by EPA subsequent to the production of the An Foras Forbatha report.

Along the River Poddle, a total of 80 households and 5 commercial properties were seriously affected by the flooding. The affected area stretched from Kimmage Cross Roads to the Grand Canal. Some of the three storey houses on Harold’s Cross Road had their bottom storey completely filled with floodwater and water depths of two feet were typical in many houses.

With regard to Sandymount, extensive flooding of the Gilford, Wilfield area occurred with the floodwaters inundating many gardens in the vicinity. The floodwaters also advanced as far as Monkstown Rugby Club Grounds, where the main pitch was completely flooded.

The only available data for Leixlip in relation to the Hurricane Charlie flood event was in relation to the River Ryewater flow rate. The River Ryewater yielded a peak flow of 48.1 m3/s at the Leixlip Hydrometric Station according to the OPW Hydrometric website, http://www.opw.ie/hydro. In Blessington, 85mm of rainfall was observed on 25/26th of August, which is 104% of the monthly average. The Ballyward Bridge, which was a 4 span masonry arch bridge spanning the River Liffey about a mile and a half from Blessington, collapsed 11 days after the flood.

4.3.2.19 Flood Event of August 1984

Flooding ensued in the Finglas part of Dublin following heavy rainfall in late August 1984. The area around Finglas Bridge was flooded as this is the meeting point for the River Tolka and Finglas Stream. Both commercial and residential properties were damaged in the floods and a map was found outlining the exact extent of the flooding and the affected areas.

4.3.2.20 Flood Event of November 1982

Widespread flooding occurred across Dublin as a result of extremely heavy rainfall on the 5th, 6th and 7th of November. 55.1mm of rainfall was recorded at Dublin Airport between midnight on the 5th November and midnight on the 6th November. The situation was compounded by the large amounts of rainfall that fell in the previous weeks with surfaces already waterlogged. The most severe flooding in the entire County occurred in Clondalkin where eighteen houses were flooded at Cherrywood Estate. Other areas which were affected by the floods were Malahide, Swords, Skerries, , Stillorglan, , , Clondalkin, Mulhuddart and Lucan.

Along the River Poddle HPW, minor surface flooding occurred in the Glendown Estate due to the high level of the Poddle River. No further details were provided.

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4.3.2.21 Flood Event of November 1968

Flooding occurred in the Dublin and Celbridge areas in November 1968 as a result of heavy rainfall; however no details are provided in relation to any damage which may have been caused. The River Tolka recorded a peak flow of 45-48m3/s at Drumcondra Hydrometric Station as per the EPA report entitled "Flooding in the Tolka Catchment 8 January 2005" (Reference 6). with the River Liffey yielding a peak flow of 64m3/s at Celbridge Hydrometric Station according to the ESB Report "River Liffey Flood Control and Dam Safety" (Reference 17).

4.3.2.22 Flood Event of November 1965

The historical data indicated that severe flooding occurred in November 1965 following three days of torrential rain.

In Dublin, the Tolka, Dodder and Camac Rivers all overflowed. The worst hit area in Rathfarnham was the Grange Park housing estate where over 40 houses were affected by the flooding. Also in Rathfarnham, the occupants of 50 houses in Orwell Gardens had to sandbag their back doors after the River Dodder burst its banks. Schools were flooded in Donabate while the Malahide Golf Club was also inundated by floodwaters. The Irish Sweepstakes Offices at Ballsbridge was flooded as a result of the Dodder overflowing, families were evacuated from their homes after the River Dodder and Camac overflowed. The River Tolka recorded a peak flow of 59.5m3/s at Drumcondra Hydrometric Station as per the EPA Report entitled "Flooding in the Tolka Catchment, 8 January 2005" (Reference 6) and the River Dodder yielded a peak flow of 138.75m3/s at Orwell Bridge Hydrometric Station according to the Dublin City Council Report entitled "River Dodder Improvement Scheme - Angelsea Road Section Donnybrook to Ballsbridge" (Reference 16).

The historical review indicated that a number of houses were flooded in Maynooth as a result of the rainfall; however there is no indication of the exact quantity or location of such houses.

There is little information given in relation to the effects of the November 1965 flood event in Celbridge outside of 89m3/s being the annual maximum flow of the River Liffey for the hydrometric year as obtained from the ESB Report entitled "River Liffey Flood Control and Dam Safety” (Reference 17). It is assumed this occurred in late November 1965.

Similarly, no data is provided in relation to any damage caused to Leixlip as a result of the flooding with the only relevant information relating to the River Ryewater flow rates. The River Ryewater yielded a peak flow of 64.8m3/s at Leixlip Hydrometric Station as shown on http://www.opw.ie/hydro.

4.3.2.23 Flood Event of January 1965

The review indicated that a flood event occurred in Santry in January 1965 as a result of heavy rainfall. This caused the Wad River to back up due to a blocked trash screen. However, no further details or additional information could be gathered from http://www.floodmaps.ie.

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4.3.2.24 Flood Event of June 1963

Flooding was caused and a trail of damage ensued in Dublin as a result of an onslaught of thunder, lightning and torrential rain in June 1963.

Thousands of cars became stranded in flood waters as main roads were covered to a depth of over four feet. Whole blocks of houses had to be evacuated leaving hundreds of people requiring emergency accommodation. Over 5 km of the main Dublin-Dun Laoghaire Road from Merrion Gates to Booterstown Avenue were completely water logged. Maps and photos were found which show the extent of the area affected by the storm but no additional information on flow rates was available.

4.3.2.25 Flood Event of December 1958

Some parts of Dublin were inundated due to severe flooding of the River Dodder in the early hours of Friday, 19th December 1958. The River Dodder overflowed causing flooding at the Lower Dodder Road, Orwell Gardens and Angelsea Road. The River Dodder yielded a peak flow of 116.1m3/s at Orwell Bridge and 133.09m3/s at Donnybrook Bridge as discussed in the Report entitled "Hurricane Charlie An Overview - Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18). No further data is provided relating to any damage caused by the flooding.

4.3.2.26 Flood Event of February 1958

During the early part of February 1958, there were a number of light snowfalls across Dublin. These snow showers were followed by constant rain on the 9th/10th of the month. The combined snow and rainfall resulted in a flood on the Little Dargle River but no details on flows, return periods or damage caused are available.

4.3.2.27 Flood Event of September 1957

Dublin experienced flooding after heavy rainfall in late September 1957. The flood backed up at the Nutgrove Culvert and overflowed causing a considerable flow to run west along Nutgrove Avenue. The wall along the north side of Nutgrove Avenue also collapsed due to the impounded waters. For this flood event, the River Dodder yielded a peak flow of 73.91m3/s at Orwell Bridge and 41.77m3/s at Bohernabreena Hydrometric Station as per the Dublin Corporation Report entitled "Hurricane Charlie An Overview - Flooding in Dublin city Rivers 25/26 August 1986" (Reference 18).

4.3.2.28 Flood Event of December 1956

Flooding was caused in Dublin by heavy rainfall and snow during the week beginning Christmas Day 1956. This resulted in the Little Dargle and Dundrum Rivers overflowing but no reports were present documenting any damage that may have occurred. However, information is provided in the Dublin Corporation Report entitled "River Dodder 1986 Flooding Report" (Reference 19) relating to the River

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Dodder flow rates with a peak flow of 73.06m3/s recorded at Orwell Bridge and 30.16m3/s at Bohernabreena Hydrometric Station.

4.3.2.29 Flood Event of December 1954

Gale force winds, reaching speeds of up to 65mph, and torrential rain caused widespread flooding throughout Dublin and parts of Kildare in early December 1954. The flooding was reported to be the worst for many years with an estimated AEP of 1.1%.

In Dublin, the Tolka, Wad and Camac Rivers all burst their banks and the also overflowed due to an overwhelming of the culvert capacity by the excessive rainfall. Available records indicate that 69mm of rainfall fell in 17 hours on the upper Tolka catchment (Dunshaughlin) with 58mm of rain falling on the lower part of the catchment (Dublin Airport). This resulted in approximately 2000 family homes flooding and several hundred people being forced to evacuate their homes. In relation to the overflowing of the River Tolka, it washed away many portions of the stone pillars supporting the main Dublin-Belfast Great Northern Railway line at East Wall Road causing the bridge to collapse and the railway lines to be left hanging. Water was almost a foot deep at Nutley Park Corner on Stillorglan Road and cars were stranded in floodwaters in the Ballymun area resulting in traffic blocks. The golf course in Rathfarnham was under water and tidal flooding occurred in Blackrock with huge waves crashing over the sea wall causing the railway line to flood. All train services were suspended between Dun Laoghaire and the city. The strong gales blew down telephone poles and wires and also caused widespread breaking of windows and slates. At Howth, boats full of water were bashed against the wall resulting in attempts being made to take them out of the harbour. The River Tolka had a peak flow of 85m3/s at Drumcondra Hydrometric Station as per the Dublin Corporation Report entitled "Hurricane Charlie An Overview - Flooding in Dublin city Rivers 25/26 August 1986" (Reference 18).

A wall in Saggart collapsed and part of the road at Saggart Cross, just outside Rathcoole, was undermined.

In Celbridge, the ESB Report entitled "River Liffey Flood Control and Dam Safety" (Reference 17) describes how the River Liffey yielded an annual maximum flow of 155m3/s for the hydrometric year at the Celbridge Hydrometric Station. However, the exact date of this flow is not presented in the report but it is assumed to have occurred in December 1954.

In Clane Village, a tributary of the River Liffey overflowed making roads in the area impassable. No additional details were provided.

The heavy rainfall in December 1954 caused the Liffey and Ryewater Rivers to overflow in Leixlip leading to traffic disruptions in the area with roads flooding. Mill Lane, in particular, was completely cut off and houses in Buckley's Lane were evacuated. The peak flow rate of the Liffey entering the Leixlip Reservoir was measured to be 175m3/s as per the ESB report "River Liffey Flood of 25-26 August 1986" (Reference 20). This consisted of 155m3/s natural inflow plus 20m3/s released from Golden Falls Reservoir.

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In Naas, a stream overflowed at Poplar Square causing houses and businesses in the vicinity to be evacuated following flooding by up 0.6m to 0.9m of water. The street level around the Poplar Square area is 91.5mOD Malin which means the floods reached a level of approximately 92.23mOD Malin in this region. A second stream known as "Callan's River" near New Row and The Harbour also overflowed causing adjacent houses to flood. Houses too were cut off by floodwaters at Millbrook and a footbridge over the stream washed away as well. Local roads experienced flooding also, namely the Ballymore Eustace Road.

The snow and rain in Kilcock caused houses to flood on Connaught Street. The Kilcock to Maynooth road was also impassable due to the floods but very little data on damage caused is provided.

4.3.2.30 Flood Event of September 1946

A flood event occurred in Dublin in September 1946 where the River Poddle overflowed its south bank causing damage at AE Derrington Ltd Pain Factory, Larkfield Mills, Sundrive Road, Kimmage Co. Dublin. The River Tolka recorded a peak flow of 48m3/s at Drumcondra Hydrometric Station in accordance with the Dublin Corporation Report entitled "Hurricane Charlie An Overview Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18). However, no other information was available relating to this event.

4.3.2.31 Flood Event of August 1946

In Dublin, downpours of rain and gale force winds caused many areas to flood in August 1946. Such was the extent of rainfall that the River Dodder burst its banks between Rathfarnham Bridge and Orwell Road causing 50 families in adjoining premises to evacuate their homes. Tidal flooding also occurred at Dun Laoghaire where heavy seas broke over harbour walls. Other parts affected by the flood event included Donnybrook, Clonskeagh, Ringsend and Drumcondra. In relation to flow rates, the River Dodder yielded a peak flow of 87.8m3/s at Orwell Bridge and 79.3m3/s at Bohernabreena Hydrometric Station as outlined in the Dublin Corporation Report entitled "Hurricane Charlie An Overview Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18).

4.3.2.32 Flood Event of January 1941

Areas adjacent to the Poddle HPW in Dublin were affected by flooding in January 1941 after the River Poddle overflowed at Marroebone Lane; however no other details were provided.

4.3.2.33 Flood Event of September 1931

Early September 1931 saw flooding occur in various parts of Dublin as a result of heavy rainfall and strong winds. The flooding was general and widespread, extending to both north and south of the city and also to parts of the suburbs. Much of the flooding resulted from the River Dodder overflowing, leaving 150 families homeless with many houses flooded to a depth of several feet. Two houses were demolished close to Milltown and a small footbridge close to Milltown was torn down. Trees on the

IBE0600Rp0008 87 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL banks of the River Dodder had been torn down; roadways alongside the river caved in and adjoining fields were covered in branches. The River Dodder caused even more damage with a portion of the Dodder Bridge near Lansdowne Road collapsing. Another bridge was washed away at Glenasmole, where the Slade Brook meets the River Dodder. The floods also damaged St. Mary’s church at Donnybrook. For this flood event of September 1931, the peak flow of the River Dodder at Orwell Hydrometric Station was 152.91m3/s while at Drumcondra Hydrometric Station the flow in the River Tolka was reported as 53.8m3/s according to the Dublin City Council report entitled “Flooding of Nov.1965 Dublin Area-handwritten notes” (Reference 21).

Floods caused by heavy rain, accompanied by thunder and lightning, also occurred in the Chapelizod area; however no additional information is available.

4.3.2.34 Flood Event of November 1915

The Dublin Corporation Report entitled "Hurricane Charlie An Overview Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18) indicated that a flood event occurred in November 1915 where the River Tolka recorded a peak flow of 42.5m3/s at Drumcondra Hydrometric Station. However, no other information was provided relating to this event.

4.3.2.35 Flood Event of August 1912

A flood event occurred in Dublin in August 1912 resulting in a peak flow in the River Dodder of 63m3/s at Bohernabreena Hydrometric Station as per The Dublin Corporation Report entitled "Hurricane Charlie An Overview Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18). No further details on the flood event were available on http://www.floodmaps.ie.

4.3.2.36 Flood Event of April 1909

Dublin experienced flooding in April 1909 and according to the RPS MCOS Report entitled “River Tolka Flood Study Technical Report Volume 2 River Modelling Report” (Reference 12), this led to a peak flow in the River Tolka of 37m3/s at the river outlet. However, no other information was provided relating to this event.

4.3.2.37 Flood Event of August 1905

Heavy and prolonged rainfall caused flooding in some parts of Dublin towards the end of August 1905, causing the Dodder and Tolka Rivers to burst their banks. The River Dodder carried several trees downstream and jammed a sewer pipe traversing a stream, causing it to overflow in the vicinity of Ballsbridge. The same river also caused considerable damage to a newly established blacking boot cream and floor polish factory at , Rathfarnham. A laneway adjacent to the Dodder River at Milltown containing 10 small cottages flooded as well. For this flood event of August 1905, the peak flow of the River Dodder at Orwell Hydrometric Station was 141.59m3/s and 99.11m3/s at

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Bohernabreena Hydrometric Station, as described in the RPS MCOS Report entitled “River Tolka Flood Study Technical Report Volume 2 River Modelling Report” (Reference 12).

4.3.2.38 Flood Event of November 1901

The Dublin Corporation Report entitled "Hurricane Charlie An Overview Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18) indicated that a flood event occurred in November 1901 where the River Tolka recorded a peak flow of 56.63m3/s at the outlet of the river. However, no other information was provided relating to this event.

4.3.2.39 Flood Event of November 1898

A flood event occurred in Dublin in November 1898 resulting in a peak flow in the River Tolka of 45m3/s at the river outlet according to the RPS MCOS Report entitled “River Tolka Flood Study Technical Report Volume 2 River Modelling Report” (Reference 12) No further details on the flood event were available on http://www.floodmaps.ie.

4.3.2.40 Flood Event of October 1891

Dublin experienced flooding in October 1891 and The Dublin Corporation Report entitled "Hurricane Charlie An Overview Flooding in Dublin City Rivers 25/26 August 1986" (Reference 18) outlines how this led to a peak flow in the River Dodder of 96.28m3/s at the Bohernabreena Hydrometric Station. However, no other information was provided relating to this event.

4.3.2.41 Flood Event of October 1886

The Dublin Corporation Report entitled "River Dodder 1986 Flooding Report" (Reference 19) indicated that a flood event occurred in October 1886 where the River Dodder recorded a peak flow of 48.14m3/s at Bohernabreena Hydrometric Station. However, no other information was provided relating to this event.

4.3.2.42 Flood Event of November 1880

A flood event occurred in Dublin in November 1880 resulting in a peak flow in the River Tolka of 71m3/s at the river outlet as per the RPS MCOS Report entitled “River Tolka Flood Study Technical Report Volume 2 River Modelling Report” (Reference 12). No further details on the flood event were available on http://www.floodmaps.ie.

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4.4 PRELIMINARY ASSESSMENT OF PAST FLOODS AND FLOODING MECHANISMS

A preliminary assessment of a number of major historical flood events which occurred in HA09 has been carried out. The assessment mainly focused on the examination of flood generation mechanism for each event and estimation of its frequency of occurrence.

4.4.1 Past flooding history and selection of flood events

HA09 has experienced a number of major flood events in the past, most notably in November 1965, August 1986, June 1993, November 2000, November 2002, August 2008, November 2009 and October 2011. The August 1986, June 1993, November 2000, November 2002, and August 2008 flood events were the worst among these in terms of the magnitude of the observed flow records (mainly flood events with smaller exceedance probability) and also the severity of damage caused to properties and people.

The historic flood data collected from various sources were reviewed and reported in Section 4.3. Based on the historical review of the severity of all flood events and subject to the availability of continuous and AMAX records, a number of major flood events were selected to examine further their causes/mechanisms, behaviour and their frequency of occurrences. AMAX time series and/or continuous flow records were analysed for six gauging stations located on or upstream of watercourses to be modelled within HA09 as shown in Table 4.9 below.

Table 4.9: Flow Data Availability for Gauges on Watercourses to be Modelled in HA09

Station Station AMAX Series Continuous Flow Watercourse Catchment Number Name Provided Record Available Anne’s 09048 Ryewater Liffey Y Y Bridge

09049 Maynooth Ryewater Liffey N Y

09001 Leixlip Ryewater Liffey Y Y

09024 Morell Morell Liffey Y (with gaps) Y

Waldron’s 09010 Dodder Liffey Y Y Bridge

09102 Cadbury’s Santry Santry/Coastal N Y

These have been used to conduct flood event analysis within HA09. Table 4.10 presents the selected events on the affected AFA basis.

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4.4.2 Flood Mechanisms in HA09

Flooding is a natural process and can happen at any time in a wide variety of locations. Flooding can come from rivers and the sea, directly from rainfall on the ground surface and from rising groundwater, surcharging sewers and drainage systems.

The various types of flooding in HA09 can be categorised as follows:

Fluvial flooding: This type of flooding occurs when the capacity of the river channel is exceeded or the channel is blocked or restricted, and excess water spills out from the channel onto adjacent low- lying areas. Fluvial flooding is generally caused by short duration high-intensity or prolonged rainfall in the catchment.

Pluvial flooding: This type of flooding is defined as flooding from rainfall-generated overland flow, before the runoff enters any watercourse or sewer. This mainly occurs when intense rainfall, often of short duration, that is unable to soak into the ground or enter drainage systems, can run quickly off land and result in local flooding. It can also result when the drainage system is overwhelmed by heavy rainfall, becomes blocked or is of inadequate capacity.

Groundwater flooding: Groundwater flooding occurs when water levels in the ground rise above surface elevation following prolonged and heavy rainfall. It is most likely to occur in low-lying areas underlain by permeable rocks. Groundwater flooding may take weeks or months to dissipate because groundwater flow is much slower than surface flow and water levels thus take much longer to fall.

Tidal and coastal flooding: This type of flooding occurs during exceptionally high tides or during storm events when low pressure systems result in storm surges on the coast lines and estuaries. Wind action causes increased wave heights which also contribute to coastal flooding.

Combined fluvial and tidal flooding: This type of flooding occurs from the joint effect of both fluvial and tidal flood events.

In HA09, no records of groundwater flooding events have been found, most flooding events are of the ‘fluvial’ category with combined tidal and fluvial flooding in coastal areas such as Clontarf, Ringsend, Sandymount and Raheny.

4.4.3 Flood event behaviour and their frequency

The behaviour of the selected flood events were examined by plotting their associated flow hydrographs. The shape of the hydrograph, its response time and flood duration have been examined for each of the selected events. The shape of the hydrograph is obviously dependent on the catchment physical and meteorological characteristics and in particular, the catchment area, slope, catchment soil type and the antecedent wet condition, drainage density and the catchment storage behaviour and the rainfall type. In small, steep catchments, local intense rainfall can result in the rapid onset of deep and fast-flowing flooding with little warning. Such ‘flash’ flooding, which may last a few

IBE0600Rp0008 91 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL hours can give a very peaky shape hydrograph. In a larger catchment like the River Liffey, flash flood in the upper steeper tributary catchments can have has lesser effects on the downstream part of the catchment, due to the attenuation effect. Flooding at the coastal downstream reach of the river can be caused from the joint occurrences of fluvial and tidal flood events. The frequency of the selected flood events have been analysed by fitting the AMAX time series for the associated gauging sites. Available AMAX time series were fitted to three flood-like distributions, namely, the GEV, EV1 and 2-parameter Lognormal (LN2) distributions. In most cases EV1 distribution was found to be the best suitable to describe the AMAX flood series of the River Liffey catchment.

As an example of flood event analysis within HA09, a hydrograph plot of the November 2002 event on the Ryewater River as recorded at Hydrometric Station 09001 (Leixlip) is shown on Figure 4.6, with Figures 4.7 to 4.10 depicting frequency analysis.

Figure 4.6 Observed flood hydrograph during the November 2009 flood event at the Leixlip hydrometric station of Ryewater River

Figure 4.7 Observed Annual Maximum Flows for Ryewater River at Leixlip (Hydr. Stn. 09001)

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Figure 4.8 Fitted EV1 frequency Curve to the observed AMAX records for Ryewater River at Leixlip (Hydr. Stn. 09001)

Figure 4.9 Fitted GEV frequency curve to the observed AMAX records for Ryewater River at Leixlip (Hydr. Stn. 09001)

Figure 4.10 Lognormal (2-parameter) frequency curve to the observed AMAX records Ryewater River at Leixlip (Hydr. Stn. 09001)

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Figure 4.7 shows the observed annual maximum flow records for Ryewater River at Leixlip for the period of 1956 to 2010. Figures 4.8, 4.9 and 4.10 show the fitted EV1, GEV and 2-parameter Lognormal distributions to these records respectively. It can be seen from these figures that all three distributions (EV1, GEV & LN2 distributions) describe the annual maximum records for this station quite well. Based on the EV1 distribution, the estimated AEP of the observed flood flow of 91.50 m3/s during the November 2002 flood event (15/11/2002) is approximately 1.11% (1 in 90 years return period) and of the November 2000 flood event is approximately 2.5% (1 in 40 years return period).

For some of the hydrometric stations sufficiently long records were not available to estimate the frequency of the observed events using the associated at-site data (as mentioned in Table 4.10). The frequency of the observed flood events for these stations can be approximated from the corresponding estimated frequency of the nearest gauging site on the same river which has longer records. For example, the estimated AEP of the observed flood event in November 2002 at Turnings would be approximately 10% based on the corresponding estimate for Morell River at Morell Bridge.

Table 4.10 summarises the flood mechanism, hydrograph shape and estimated frequency of a number of selected flood events. The selection of these flood events were based on the magnitude of the observed flow records (mainly flood events with smaller exceedance probability), the severity of damage caused to properties and people and ensuring that enough events were available for each station. It can be seen from this table that the majority of the flood events are of ‘fluvial’ type. The most severe flood events (in terms of frequency and damage caused) in HA09 were identified as the August 1986, November 2000, November 2002 and August 2008. Most parts of HA09 were affected during these events and the causes of flooding were the prolonged intense rainfall.

.

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Table 4.10: Significant flood events, their generation mechanisms and frequency HA09

AFA Nearest Gauging Stations Major flood events

Record Peak flow 1 Approx. AEP Stn. No. Length Location Date Rank Flood mechanisms (m3/s) (%) (years)

2 Fluvial; Flooding caused by prolonged and heavy rainfall. Fast response 14/11/2002 21.51 6 50% catchment, time to peak is approximately 1 day. Ryewater Fluvial; Flooding caused by prolonged and intense rainfall. Flood 09048 10 River at 16/08/2008 50.23 10 (highest) 6.67 – 5% duration was 9-days; Fast response catchment, time to peak is Anne's approximately 1 day. Bridge Fluvial: Flooding caused by intense rainfall followed by prolonged 31/12/2009 34.75 8 20% antecedent wet condition. Flood duration was 7-days; time to peak is approximately 1-day. Maynooth Fluvial; Flooding caused by prolonged and heavy rainfall. Fast response 14/11/2002 28.11 6 50% catchment, time to peak is approximately 1 day.

Ryewater Fluvial; Flooding caused by intense rainfall. Flood duration was 12 days; 09049 10 River at 17/08/2008 60.37 10 (highest) 10-6.67% Fast response catchment, time to peak is approximately 1 day. Maynooth Fluvial: Flooding caused by intense rainfall followed by prolonged 31/12/2009 50.64 8 10-6.67% antecedent wet condition. Flood duration was 5-days, time to peak is approximately 1-day. Dec 1954 Missing - - Fluvial: Flooding caused by intense rainfall Fluvial; Flooding caused by prolonged and heavy rainfall. Flood duration 25/11/1965 64.80 50 10-6.67% was 12-days. Fast response catchment, time to peak approximately 1-2 days. Fluvial; Flooding caused by intense rainfall followed by antecedent wet 27/12/1978 62.40 49 10-6.67% condition. Flood duration was 6-days, time to peak is approximately 1-2 days. Ryewater Leixlip 09001 54 river at 26/08/1986 48.10 41 20% Fluvial; Flooding caused by intense rainfall. Flood duration was 5-days. Leixlip Fluvial; Flooding caused by intense rainfall followed by antecedent wet 12/06/1993 60.70 48 20 -10% condition.

Fluvial; Flooding caused by intense rainfall. Flood duration was 5-days, 06/11/2000 81.80 53 2.5% time to peak 1-day.

Fluvial; Flooding caused by intense rainfall followed by antecedent wet 15/11/2002 91.50 54 (highest) 1.11% condition. Flood duration was 3-days, time to peak 1-day.

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AFA Nearest Gauging Stations Major flood events

Record Peak flow 1 Approx. AEP Stn. No. Length Location Date Rank Flood mechanisms (m3/s) (%) (years)

Fluvial; Prolonged and heavy rainfall. Flood duration was 12-days, time 17/08/2008 65.50 51 10-6.67% to peak 1-2 days.

29/11/2009 51.10 45 20% Fluvial; Prolonged and heavy rainfall. Flood duration was 30-days,

Dec 1954 Missing - - Fluvial: Flooding caused by intense rainfall 25/11/1965 Missing - - Fluvial: Flooding caused by prolonged and heavy rainfall No long Fluvial; Flooding caused by intense rainfall followed by prolonged annual max. 02/11/1968 75.25 - antecedent wet condition. Flood duration was 5-days. Fast response data is catchment, time to peak is approximately 1-2 days. available 47 River Liffey 26/08/1986 Missing - - Fluvial: Flooding caused by intense rainfall followed by strong winds Celbridge 09006 (5 years at Celbridge available) 12/06/1993 Missing - - Fluvial: Prolonged and heavy rainfall 06/11/2000 Missing - - Fluvial: Prolonged and heavy rainfall Fluvial; Flooding caused by intense rainfall followed by antecedent wet 15/11/2002 Missing - - condition. 17/08/2008 Missing - - Fluvial: Prolonged and heavy rainfall 25/11/2009 Missing - - Fluvial: Prolonged and heavy rainfall

26/08/1986 Missing - - Fluvial: Flooding caused by intense rainfall followed by strong winds

12/06/1993 Missing - - Fluvial: Prolonged and heavy rainfall

06/11/2000 Missing - - Fluvial: Prolonged and heavy rainfall Morell River Turnings 09024 9 at Morell Bridge Fluvial; Flooding caused by intense rainfall followed by antecedent wet 15/11/2002 37.34 8 10% condition. Flood duration was 5-days, time to peak 1-day.

Fluvial; Flooding caused by intense rainfall. Flood duration was 15-days. 10/01/2008 26.73 7 33.33% Fast response catchment, time to peak approximately 1-day, slightly slower recession Fluvial; Flooding caused by prolonged and heavy rainfall. Flood duration was 15-days, time to peak is approximately 1-day. 30/11/2009 38.14 9 ( highest) 10-6.67%

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AFA Nearest Gauging Stations Major flood events

Record Peak flow 1 Approx. AEP Stn. No. Length Location Date Rank Flood mechanisms (m3/s) (%) (years)

Dec 1954 No records No records No records Fluvial: Flooding caused by intense rainfall Aug 1968 No records No records No records Fluvial: Flooding caused by intense rainfall followed by strong winds 12/06/1993 No records No records No records Fluvial: Prolonged and heavy rainfall River Liffey 06/11/2000 No records No records No records Fluvial: Prolonged and heavy rainfall Clane 09034 n.a. at Straffan Fluvial; Flooding caused by intense rainfall followed by antecedent wet U/S 15/11/2002 No records No records No records condition. 17/08/2008 No records No records No records Fluvial: Prolonged and heavy rainfall 25/11/2009 No records No records No records Fluvial: Prolonged and heavy rainfall 26/08/1986 No records No records No records Fluvial: Flooding caused by intense rainfall followed by strong winds 12/06/1993 No records No records No records Fluvial: Prolonged and heavy rainfall Naas 06/11/2000 No records No records No records Fluvial: Prolonged and heavy rainfall Stream at Newbridge 09042 2 Fluvial; Flooding caused by intense rainfall followed by antecedent wet Osberstown 15/11/2002 No records No records No records condition. House 17/08/2008 No records No records No records Fluvial: Prolonged and heavy rainfall 25/11/2009 No records No records No records Fluvial: Prolonged and heavy rainfall Fluvial; Flooding caused by intense rainfall accompanied by strong 26/08/1986 269.0 57 (highest) 0.25% winds; Flood duration was 3-days, Fast response catchment, time to River peak is approximately 12-15 hours Dodder at 09010 57 Waldron's 05/11/2000 179.4 36 2.85% Fluvial; Flooding caused by intense rainfall; Flood duration was 3-days. Bridge 06/06/2009 60.8 39 33.33% Fluvial; Flooding caused by intense rainfall; Flood duration was 3-days. Dublin 16/01/2010 88.8 50 20% Fluvial; Flooding caused by intense rainfall; Flood duration was 7-days. 14/11/2002 5.78 9 20 – 10% Fluvial; Prolonged and heavy rainfall Santry River 09102 10 02/07/2009 7.97 10 (highest) 5% at Cadbury’s Fluvial; Prolonged and heavy rainfall 11/11/2009 3.33 5 50% Fluvial; Prolonged and heavy rainfall

Note: 1 For each hydrometric station, the observed AMAX time series was ranked in ascending order i.e. the smallest record has rank 1 and the highest peak flow has the highest rank. For example, at the hydrometric station 09001 (Ryewater River at Leixlip), the peak flow recorded on 15/11/2002 (91.50m3/s) is the highest record in the 54 years of data and was therefore given a rank of 54.

2 Based on an analysis of 10 years of available Annual Maximum flow records using EV1 distribution. The 5T rule (FEH, 1999) indicates that this duration of AM records can be considered adequate to estimate the frequency of this flood event with sufficient accuracy.

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5 HYDROLOGICAL ANALYSIS METHOD STATEMENT

5.1 ANALYSIS OF HYDROMETRIC AND METEOROLOGICAL DATA

5.1.1 Gauging Station Rating Review

A rating review of four hydrometric stations in HA09 is being undertaken. This involves:

• visiting the site (at high flows where practical); • liaising with OPW or EPA (as appropriate) to request available information on each station. This included the staff gauge zero datum history, the history of the station, annual maximum series data, spot gaugings and a rating report; • procuring a channel and floodplain survey for an adequate reach of the river upstream and downstream of the gauging station location; • constructing a hydraulic model based on the surveyed sections, using MIKE FLOOD software; • calibrating the model (by adjusting weir / bridge coefficients and Manning’s roughness values) using the existing station rating up to the reliable limit (usually the highest gauged flow or

Qmed); • using the calibrated model to simulate fluvial discharges up to and exceeding the estimated 1 in 1000 year flow for the site.

The above process results in a modelled stage-discharge relationship for upper range of the hydrometric gauging station ratings. It reduces the uncertainty associated with previous rating equations which were based on simple extrapolation beyond the maximum gauged flow over the period of record for the station.

Past experience has shown that this is a critical exercise in terms of improving confidence and providing a site specific understanding of limitations at certain stations due to, for example, changes in the rating curve with time at “soft” engineered stations, bypass flow, blockages or over levée flood situations.

5.1.2 Hydrometric Data

Refer to discussion of preliminary data analysis in Section 4.4.

5.1.3 Rainfall Data Analysis

Rainfall data analysis is required to provide the necessary rainfall input to hydrological models (refer to Sections 5.4 and 5.6.1) where required. An ongoing trial looking at the potential benefits of using rainfall radar data (calibrated to daily and hourly rainfall gauges described in Section 4.2) to provide rainfall input to hydrological models is currently ongoing as part of the overall Eastern CFRAM Study.

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If the trial outcomes conclude that there is a benefit to using rainfall radar data, then its use may be rolled out to the entire Eastern Study Area. If this is the case, rainfall radar data analysis will be undertaken to provide rainfall input to rainfall runoff hydrological models as part of the overall hydrology methodology. A detailed description of rainfall radar data analysis is provided in Appendix C.

However if the radar data analysis trial of the Dublin radar data for the complete Eastern CFRAM Study project area shows significant problems and inconsistencies that are difficult to correct and calibrate in order to generate the hourly data rainfall series; rainfall data analysis will be undertaken using data from daily and hourly rainfall gauges to provide the necessary rainfall input to hydrological models. GIS elevation-based spatial-temporal interpolation techniques will be used to enhance the standard Thiessen polygons methodology to generate spatially-weighted rainfall time series as inputs to the hydrological models, refer to Sections 5.4 and 5.6.1.

5.2 MODEL CONCEPTUALISATION

5.2.1 HA09 Hydraulic Models

To facilitate hydrological assessment and hydraulic modelling, nine hydraulic models have been conceptualised for HA09 as shown in Figure 5.1. Hydrological estimation will be undertaken to provide inputs for each hydraulic model. The number and boundaries of the models have been largely chosen due to modelling practicalities such as having one 2D mesh per model and therefore one AFA per model and such that gauge stations separate models and therefore can be used to directly calibrate flow estimations on both models. The large number of HEP’s will allow good variation in the rarity / frequency conditions up and down the catchments and at each HEP comparison of different hydrology estimations will be undertaken for robustness (from rainfall run-off methods to statistical analysis methods such as outlined in FSU WP 2.2 & 2.3). Where appropriate the guidance within FSU WP 3.4, paragraph 4.3.3 will be followed:

‘One way to meet the aspiration for treating large river models in small units is to carry out multiple runs with different inflow conditions, each run being intended to simulate the required design conditions in a different part of the model’

In selecting the 12 models the degree of interdependence has been a secondary consideration. This is acknowledged within WP 3.4 as being less important where an FSU approach is being used ‘because there is no direct link between design peak flow and event duration’ (FSU WP 3.4, paragraph 4.3.1).

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Figure 5.1: HA09 Conceptualised Models

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5.2.2 Hydraulic Model Calibration

Based on the review of historical flood events (Section 4.3) and preliminary assessment of flood mechanisms using available hydrometric data to determine AEPs (Section 4.4), the following flood events have been selected for model calibration and verification purposes (refer to Table 5.1). Where no flow records are available level information and photographs / mapped flood outlines may be used to validate the models. Where NAM models are available and a synthetic flow trace is produced based on the rainfall record, the synthetic flow trace will be combined with the observed level information for calibration.

Table 5.1: Selected Flood Events for Hydraulic Model Calibration and Verification

Hydraulic Model Selected Flood events for hydraulic model calibration Number and verifications Hydrometric Stations Date Peak flow (m3/s) 9004 1 - No flow records available 9102 1 14/11/2002 5.78 9102 1 02/07/2009 7.97

9102 1 11/11/2009 3.33

9002 2 - No flow records available 9005 2 - No flow records available 9035 2 21/10/2002 47.27 9035 2 08/01/2005 18.15 9035 2 05/09/2008 20.08 9035 2 30/12/2009 15.98 9064 2 - No flow records available 9066 2 - No flow records available 9101 2 - No flow records available 9001 3 25/12/1968 69.1 9001 3 27/12/1978 62.4 9001 3 06/11/2000 81.8 9001 3 15/11/2002 91.5 9001 3 29/11/2009 51.1 9006 3 - No flow records available 9012 3 - No flow records available 9015 3 - No flow records available 9022 3 - No flow records available 9034 3 - No flow records available 9050 3 - No flow records available 9048 4 14/11/2002 21.51 9048 4 08/01/2005 41.45

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Hydraulic Model Selected Flood events for hydraulic model calibration Number and verifications Hydrometric Stations Date Peak flow (m3/s) 9048 4 16/08/2008 50.23 9048 4 31/12/2009 34.75 9049 4 15/11/2002 28.11 9049 4 08/01/2005 50.87 9049 4 17/08/2008 60.32 9049 4 31/12/2009 50.64 9008 6 - No flow records available 9033 6 - No flow records available 9043 6 - No flow records available 9024 7 15/11/2002 37.34 9024 7 08/01/2005 25.42 9024 7 10/01/2008 26.73 9024 7 30/11/2009 38.14 9027 7 - No flow records available 9028 7 - No flow records available 9029 7 - No flow records available 9030 7 - No flow records available 9036 7 - No flow records available 9044 7 20/08/2009 6.49 9044 7 29/11/2009 15.86 9044 7 27/12/2010 7.24 9045 7 - No flow records available 9046 7 - No flow records available 9007 8 - No flow records available 9032 8 - No flow records available 9039 8 - No flow records available 9056 8 - No flow records available

The fluvial hydraulic models will be calibrated and verified against these past flood events. The models will be verified to vertical accuracies of not less than 0.2m and 0.4m for HPWs and MPWs respectively. Calibration and verification of the models will involve adjusting a number of parameters in various combinations during a series of additional simulations, in an attempt to achieve modelled levels closer to the recorded levels. The parameters investigated included channel and structure roughness coefficients, link weir roughness coefficients, tidal boundaries and floodplain resistance.

Rating curve analysis, including hydraulic modelling of the hydrometric stations to reduce uncertainty in extrapolated values will also be used where appropriate to verify the magnitude of observed events.

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The results of this historical flood analysis will also be compared with design flood levels and extents to ensure that there is consistency between observed and design events, particularly with reference to the events’ estimated annual exceedance probabilities. This desk based historical data analysis along with the information gathered during our site visits will help the modellers to understand the hydrologic and hydraulic behaviour of the river catchment including flood generation mechanism, causes of flooding and constraints (i.e. to establish the source pathway-receptor model).

A review of all previous studies and reports relating to the study area will also be undertaken with relevant data again being used to support the calibration and verification process.

5.3 HYDROLOGICAL ESTIMATION POINTS

Hydrological Estimation Points (HEPs) are located along each modelled watercourse to denote points where hydrological analysis is required for the estimation of design flows that will be used as hydraulic model input or for model calibration. They also serve as check points at gauging station locations, so that the design AEP event is properly derived, particularly in AFAs.

Based on model conceptualisation, and following finalisation of the AFA designations (post PFRA consultation and Flood Risk Review), a GIS exercise was undertaken to identify HEPs in HA09. These were identified according to the following categories.

5.3.1 HEP Categories

5.3.1.1 HEP at Upstream Limit of Model

The upstream extent of each model requires an HEP at which design flows and hydrographs will be derived primarily from a rainfall runoff model; or flow estimation methods as appropriate (for example in small catchments). Upstream model limits will always be at 1km2 contributing catchment areas or more.

5.3.1.2 HEP where Tributaries enter Modelled Channel

Moving downstream along the modelled reach, an HEP is located where tributaries with catchment areas greater than 5km2 enter the channel. The Generic CFRAM Study Brief required these HEPs at tributaries where it was considered that more than 10% of the main channel flow was contributed. However, this application led to an abundance of HEPs at tributary confluences in the upper reaches of catchments, and under representation in the lower reaches. This was discussed with the OPW Suir CFRAM Study team (who were identifying HEPs in the Suir Catchment at the same time) and it was considered that including all tributaries with catchments greater than 5km2 would ensure a more appropriate distribution of HEPs at tributary confluences throughout the catchment. On High Priority Watercourses (HPWs) it will often be appropriate to include flows from catchments which are much smaller than 5km² and where this is the case the inclusion of tributaries will be considered on an individual basis.

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5.3.1.3 HEP at gauging stations on Modelled Channel

At gauging stations along the modelled reaches (for which data is available), a HEP is located. These HEPs serve as check points throughout the modelled catchment, so that flow estimates can be calibrated on a catchment basis ensuring appropriate discharges are modelled for each design event.

5.3.1.4 Intermediate/Reporting HEPs

Intermediate/Reporting HEPs have both hydraulic input (top-up) and reporting functions as described below:

• Hydrology estimations at HEPs will be undertaken to ensure that the total contributing catchment at that point in the model can be checked to ensure that the sum of the model inputs are consistent with the total catchment up to that point in the model. Where necessary the models may need to be ‘topped up’ at these HEPs to ensure all of the contributing catchment is considered.

• HEPs along main channel ensuring there are no reaches greater than 5km without a HEP – this is a requirement of the Generic CFRAM Study Brief. HEPs, will serve as reporting points where calibrated peak flows for each design event at the end of the hydraulic analysis task and will be reported as a CFRAM Study deliverable.

• HEPs immediately upstream and downstream of AFAs and in the centre of each AFA. This is a requirement of the Generic CFRAM Study Brief. At these HEPs, calibrated peak flows for each design event will be reported at the end of the hydraulic analysis task as a CFRAM Study deliverable.

5.3.1.5 HEP at Downstream Limit of the Model

The downstream extent of each model requires an HEP such that the total contributing catchment can be estimated in order to check that the sum of the model inputs are consistent with hydrology estimations for the whole catchment. These will act as upstream limit HEPs where a further model is connected downstream. Where a gauging station HEP forms the boundary between two models this will act as the upstream and downstream HEP for the respective models.

5.3.2 Catchment Boundaries

As part of the OPW FSU programme, physical catchment descriptors and catchment boundaries were delineated at 500m node points along all watercourses in Ireland (based on 50k mapping), with associated GIS point and polygon shapefiles produced. Each node point has a corresponding NODE ID. This dataset has been used as the basis for HEP and catchment boundary identification, with adjustments made as necessary.

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Where HEPs have corresponding FSU NODE_IDs, the catchment is extracted from the FSU Ungauged Catchment Boundary GIS polygon dataset. This is reviewed by checking mapping, DTM; and LiDAR data where available. Where local knowledge or site walkover information indicates a deviation from the boundary shown, it will be revised accordingly.

Several HEPs do not have a FSU NODE_ID (particularly those at the upstream limit of models) and as such will require catchment delineation. This will be done on GIS using mapping, DTM and LiDAR when available. Again, local knowledge and information gained from site walkover will feed into the process. Urban catchments are particularly relevant in this respect, as catchment boundaries can be affected by drainage infrastructure and engineering interventions such as pumping from one catchment to another in high flows.

5.4 ESTIMATION OF DESIGN FLOW PARAMETERS

5.4.1 Design Flow Estimation

Design flow estimation will be undertaken using the process illustrated by the schematic Figure 5.2. It indicates a two-phased hydrology process. Phase 1 involves initial design flow estimation by two main routes depending on the type of HEP being analysed. These routes are:

• Rainfall run off modelling using NAM to provide peak flow and design hydrograph input to the hydraulic model or;

• Peak flow estimation providing point / lateral flow inputs to the hydraulic model.

When these hydrographs and flows are derived, they will be simulated in the hydraulic model and the outputs compared with observed flows at HEP gauging station check points for the AEP being considered. This brings the process into Phase 2 which is an integrated process between hydrology and hydraulics, iteratively adjusting hydrological inputs until calibration with the HEP gauging station check points is achieved.

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Figure 5.2: Two Phased Hydrology Analysis Process Chart

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Boxes 1 and 2 shown in Figure 5.2 relate to Hydraulic Model Conceptualisation/Calibration and defining HEP/Catchment Boundaries as previously described in Sections 5.2 and 5.3. Boxes 3, 4, 5 and 6 relate to the HEP categories as described in Section 5.3.1. The remaining boxes outline the hydrology estimation tasks according to HEP type as undertaken for each hydraulic model, and for each design AEP. The subsequent sections of this chapter describe these tasks and refer back to the box numbers in Figure 5.2 for clarity. Appendix D contains a table indicating the datasets that will be used in completing each task on the process chart according to Box Number.

5.4.2 Phase 1: Derivation of Growth Curves for HA09 – (Box 10)

In accordance with the FSU method, each of the HEPs should have a separate growth curve. Or as a minimum, a growth curve should be developed at each of the hydrometric stations (gauged or ungauged) on a river network. However this is likely to result in an abundance of growth curves with unrealistic changes to growth factors along modelled reaches. In these circumstances, by examining the catchment characteristics associated with each of the HEP nodes/gauging stations a number of strategic locations or nodes will be identified/selected for which growth curves would be developed on a more regional basis. Alternatively the estimated growth curves at each of the nodes will be grouped into reduced number of representative growth curves on a zoned basis. Growth curves will be developed using the FSU proposed ‘Region-of-Influence’ approach. Suitability of a suite of flood like distributions will be examined such as GEV, EV1, GLO and LN2. All relevant calculations will be carried out using a FORTRAN language based Program which was developed by NUI Galway as part of the FSU Work Package 2.2 “Frequency Analysis” (Reference 22).

A review of the available records within the Eastern and South Eastern CFRAM areas showed that there are sufficient records (annual maximum) to form a recommended pooling group size of 450 station-years from these records. However, a region can be formed by pooling records from all across Ireland. For HA09 there are only 200 station-year records therefore records from other gauged catchments with similar physiographic and climatological characteristics need to be pooled to develop a growth curve.

5.4.3 Phase 1: Calculation of Design Flows at HEPs

In general Figure 5.2 outlines the hydrology estimation methods depending on the type of HEP. Derived peak flows and hydrographs at these HEPs will then be input to the hydraulic model for the design event AEP being considered. Upstream Limit inflows will generally be input to the model as hydrographs or as point flows for small catchments. Flows from tributary confluences will generally be input as point flows, unless the tributary is of a significant catchment area, in which case a hydrograph will be derived for model input. Lateral inflows will also be used to facilitate inclusion of flow inputs between tributaries where necessary. In addition, incoming flow between tributaries will be accounted for in the catchment flow calibration process whereby tributary flow inputs are iteratively adjusted to achieve a match with observed flow at hydrometric stations. The subsequent sections describe the hydrology estimation methods per HEP type.

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5.4.3.1 Upstream Limit HEPs (Box 4, 7, 8, 9,11)

The choice of hydrology estimation method for Upstream Limit HEPs largely depends on the contributing catchment area. Rainfall runoff modelling using all available rainfall data and GIS catchment parameters is the preferred method for providing design peak flow and hydrograph input to the upstream limit of each model. This is as outlined in Boxes, 7, 8 and 9. Rainfall runoff modelling will be undertaken using MIKE NAM software and is described in detail in Section 5.6.1.

NAM model outputs will provide a flow trace time series equal to that of the rainfall record available. From this an extreme value analysis can be undertaken to derive peak flows for design return periods. For lower AEPs (higher return periods) relevant growth factors as described in Section 5.4.2 will be applied.

Typical hydrograph shape (storm profiles) will be extracted from the NAM flow trace output regarding the shape of the hydrographs (and hence the response of the HEPs catchments) and the hydrograph shape parameters such as: time of the rising part of hydrographs, time of the recession of the hydrograph, their ratios, the volume of water, the concentration and the response time of the catchment; as well as the antecedent conditions of the catchment that can be inferred from the NAM model parameters. In addition, the up-scaling of hydrographs to represent the lower AEP design flow events that have not been historically recorded will be undertaken. The corresponding rainfall events that generate the design peak flow per return period will be further analysed in terms of its characteristics: intensity, duration, volume and spatiotemporal distribution (if radar data is used). These rainfall events that cause the design peak flows per return period will be also further compared to the Depth Duration Frequency (FSU Work Package 1.2 – Reference 23) growth curves to infer correlation characteristics.

Each Upstream Limit HEP is individually reviewed to determine suitability of MIKE NAM modelling. If it is the case that the contributing area to the upstream limit HEP is very small, i.e. less than 25km2; un- gauged and fairly homogenous, for example small urban streams, it is generally considered that rainfall runoff modelling would not be applicable and index flow estimation methods (coupled by the relevant growth factor (Section 5.4.2)) such as Institute of Hydrology Report (IH) No. 124 method (Reference 24) would be more appropriate (Box 11). IH 124 (refer to Section 5.6.2) remains the recommended estimation method over FSU for small catchments, as advised by OPW. The factorial standard error associated with the QBAR estimation will also be used to calculate 68% and 95%ile confidence intervals. Gauging station data within HA09 will be analysed to determine a relationship between QBAR and Qmed so that a conversion can be undertaken before the relevant growth factor is applied.

Where hydrograph shapes are required for upstream limit model input, the Flood Studies Supplementary Report (FSSR) (Reference 25) Unit Hydrograph Technique or FSU Hydrograph Shape Generator will be explored in an effort to derive the most appropriate hydrograph shapes. These methods are outlined in Sections 5.6.2, 5.6.3 and 5.6.4.

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5.4.3.2 HEPs at Tributary Confluences (Box 5, 11, 12)

5.4.3.2.1 Tributary catchments < 25km2

Similar to small Upstream Limit HEPs, these will be associated with the IH 124 method for small un- gauged catchments; coupled with the relevant derived growth curve. However if such catchments are gauged, a single site analysis may be more appropriate.

5.4.3.2.2 Tributary catchments >25km2

These will be analysed using FSU Qmed estimation coupled with the relevant derived growth curve. Care will be taken to ensure appropriate pivotal sites are selected, drawing first on those upstream or downstream or at least within the hydrometric area. The FSU Qmed estimation spreadsheet will be used to calculate Qmed using physical catchment descriptors (Qmedpcd) associated with the HEP being considered. Pivotal site(s) are then used to adjust the Qmed estimation based on catchment descriptors by donating gauging data from a suitable station. This donation is achieved through the use of an adjustment factor which is the ratio of the Pivotal Site’s Qmedgauged and Qmedpcd . The Qmedpcd calculated at the HEP is then multiplied by the adjustment factor to arrive at a final Qmed estimation. This can be further adjusted for urbanisation if required.

Selection of pivotal sites is therefore important to ensure that the optimum adjustment factor is applied. The order of preference for pivotal site selection is:

1. A gauging station downstream of the subject site

2. A gauging station upstream of the subject site

3. A gauging station in geographical proximity to the subject site (see below)

4. A gauging station identified by the hydrological similarity measure (see below):

Geographical closeness is calculated automatically by the FSU Qmed estimation spreadsheet based on distance from the HEP. Seven pivotal site options are listed. Hydrological Similarity (dij) is calculated automatically by the FSU Qmed estimation spreadsheet using AREA, BFIsoil and SAAR physical catchment descriptors. Seven pivotal site options are listed.

If relying on options 3 or 4 due to lack of gauging stations on the watercourse, the wider range of physical catchment descriptors will also be compared for each Pivotal Site option such as FARL,

DRAIND, S1085 and ARTDRAIN2. It is important to check similarity of these characteristics (attenuation from rivers and lakes, drainage density, catchment slope and whether or not the pivotal site has been arterially drained), as these will affect how appropriate the gauged data will be for donation to the HEP. To compare these descriptors, charts will be plotted showing the relevant values with respect to the HEP value for the same descriptor. The pivotal site which compares best will be chosen. If two pivotal sites are prominent, both can be used in the adjustment, by applying a

IBE0600Rp0008 109 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL weighting to each. This weighting will be based on the user’s judgement after having looked closely at the catchment descriptors.

Sensitivity analysis on the choice of pivotal site will also be undertaken by plotting the resulting Qmed values from each to identify trends and outliers. This will also be done in the context of the 68% and

95% confidence limits associated with the Qmedpcd estimation for the HEP, using the FSU factorial standard error of +/- 1.37. This will ensure that the selected pivotal site results in an adjusted Qmed estimation that is within the confidence limits. The latest FSU Qmed estimation spreadsheet provided by OPW facilitates this sensitivity analysis by automatically populating a scatter chart with the resulting adjusted Qmed values per pivotal site option.

For stations where a CFRAM rating review is undertaken, consideration will be given to updating adjustment factors depending on RPS’ recommendation on the robustness of the revised rating. The factorial standard error associated with the Qmed estimation will also be used to calculate 68% and 95%ile confidence intervals to assist in pivotal site selection and to inform any adjustments to derived flows in catchment flow calibration.

However, if a larger tributary catchment is gauged (say >100km2 decided on a case by case basis), it is likely to be more appropriate to construct a rainfall runoff model, calibrated to the gauged data, so that a calibrated inflow hydrograph is derived. This will be undertaken where applicable. Flow contributions from tributaries 5km2 ~ 100km2 will be estimated using index design flood and growth curve derivation methods.

5.4.3.3 HEPs at Gauging Stations – Check Points - (Box 3, 7, 8, 9)

At gauging station locations along the modelled reach (where flow data is available), HEPs are located as check points for catchment flow calibration. At these points, a NAM model will be constructed for the entire upstream catchment, calibrated to available flow data. The generated AMAX series (and growth curve as needed) will be used to derive peak flows for each design AEP at the gauging station HEP. This will be used in Catchment Flow Calibration.

5.4.4 Phase 2: Catchment Flow Calibration (Box 13 to 18)

The estimated design event flows at Upstream Limit and Tributary (and Intermediate where top-up is required) HEPs will be simulated in the hydraulic model (which will have been calibrated in terms of model parameters e.g. channel and floodplain roughness; structure coefficients to selected flood events, (refer to Section 5.2.2).

The peak flow output from the design event hydraulic model will be compared with that of the combined NAM Check model output at the HEP Gauging Station Check Point (Box 14, 15). Where differences in discharge occur, the NAM models will be checked in terms of model parameters (Box 7,8,9) and point and lateral flow inputs will be iteratively adjusted (Box 11,12) within relevant confidence intervals until calibration to the gauged data is achieved for each design event (Box 16).

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This will be undertaken at each HEP gauging station check point moving downstream, to ensure the appropriate peak flow for the design AEP is simulated throughout the catchment (Box 17). Therefore, final design flow estimation will very much be integrated with the hydraulic modelling process.

Of the 19 hydrometric stations located on modelled watercourses in HA09, 15 have water level and flow data available for catchment flow calibration (refer to Table 4.6), and are therefore viable as HEP Check Points. The remaining four stations have water level data only. This level data could be used to compare observed water levels at the check point with the hydraulic model level outputs for higher AEP (lower return period) events i.e. 50% (2 year return period); 20% (5 year return period). However one of these is located at Pollaphouca Reservoir and records lake level data. The flow downstream from Pollaphouca reservoir is a controlled system and will require due consideration as such in hydrology estimation.

Design rainfall input to the NAM models will be estimated using probabilistic analysis based on radar derived rainfall data series (if approved for use) and treated as a “truth” input”. Hydrological NAM models will be calibrated by adjusting physical model parameters to achieve mass balance, not rainfall input. However if the calibration exercise exhibits significant differences between simulated and observed flows at the NAM check points, rainfall input files and the associated analysis to derive them will be checked.

FSU Work Package 3.4 (Reference 26) provides guidance on how to use catchment descriptors to estimate peak flow inputs from tributaries to ensure that the design AEP flow is simulated in the modelled channel (Reference 26, section 13.5.3). Where gauging stations are available, the guidance is followed in that the observed data will be used to adjust flow inputs as required as described above. Where a tributary joins the modelled channel that is un-gauged, Table 13.1 in FSU 3.4 report will be used to estimate the return period (and therefore growth factor) to apply to the index flows calculated for tributary input that will result in the design AEP in the main channel. The provided regression equation in Reference 26, section 13.5.4 will be used to estimate the time difference between peaks so that the peak flow can be input to the model at the correct time. Where two modelled channels meet, dependence analysis will also be undertaken following FSU WP 3.4 if HEP Check Points are not available.

5.4.4.1 Intermediate / Reporting HEPs (Box 6)

As discussed previously the models may need to be topped up at Intermediate HEPs to ensure all of the contributing catchment is considered (e.g. in a long, narrow catchment with many tributaries <5km² entering). Where this is considered necessary the additional contributing catchment will be added via lateral inflows upstream of the Intermediate HEP. Intermediate HEPs will also be continuously identified throughout the hydrological analysis when flow checks are required to verify estimations. For example, flow estimations for a tributary entering a modelled reach will be compared with the difference between flow estimates at intermediate HEPs immediately upstream and downstream of the

IBE0600Rp0008 111 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL confluence point. These points will be derived from the FSU un-gauged catchment descriptors dataset as required.

Since Intermediate HEPs are located along the modelled reaches they will be used as flow check points and to denote further points in the model for which flow data will be reported for each design AEP. This will facilitate the completion of tables of peak flood levels for all design event probabilities at key points – upstream and downstream of AFAs; in the centre of AFAs and along MPWs with no distance between points greater than 5km. In addition, model nodes will be assigned at every cross section location and flows will be reported for these in accordance with the specification. Note that reporting points based on AFA extent will not be identified until the hydraulic modelling tasks have been completed and AFA extents fully defined.

5.5 SUMMARY OF HEPS IN HA09 AND ASSOCIATED ANALYSIS

Appendix E contains a map showing the layout of HEPs in HA09, and their category. A map showing the contributing catchments to each HEP is also contained in Appendix E.

Table 5.2 provides a summary of the hydrology analysis that will be undertaken at each HEP according to model number and the HEP category. NODE_ID_CFRAMS denotes the unique identification number assigned to each HEP. This hydrology analysis is based on the overall methodology and checking each HEP in terms of catchment area, location and its contribution to the hydraulic models.

Table 5.2: Summary of Hydrology Analysis per HEP and Model Number

MODEL NODE ID CFRAMS NUMBER HEP CATEGORY HYDROLOGY 09_1507_6_RPS 1 HEP Intermediate REPORTING 09_1502_1_RPS 1 HEP Upstream Limit PEAK FLOW ESTIMATION 09102_RPS 1 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1156_1 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_475_3_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_613_3_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_452_2_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_36_2 2 HEP Tribs PEAK FLOW ESTIMATION 09_221_3 2 HEP Tribs PEAK FLOW ESTIMATION 09_242_3_RPS 2 HEP Tribs PEAK FLOW ESTIMATION UN_Trib_Camac_10 2 HEP Tribs PEAK FLOW ESTIMATION 09_1165_5 2 HEP Tribs PEAK FLOW ESTIMATION 09_1237_4_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_1870_13_RPS 2 HEP Intermediate REPORTING 09_1872_9_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_1874_17_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_1136_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION

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MODEL NODE ID CFRAMS NUMBER HEP CATEGORY HYDROLOGY 09_1128_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1142_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1029_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1252_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_832_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1243_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_627_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_628_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_396_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_435_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_481_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1131_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_613_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_475_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_UN_T03_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_39_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1308_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_452_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION TBC 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_990_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_606_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_448_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_UN_Trib_Griffeen_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_37_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_UN_T01_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION UN_Inter_Camac_1 2 HEP Intermediate REPORTING TBC 2 HEP Tribs PEAK FLOW ESTIMATION UN_Trib_Camac_20 2 HEP Tribs PEAK FLOW ESTIMATION TBC 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_UN_Trib_Griffeen_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_832_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_1308_1 2 HEP Tribs PEAK FLOW ESTIMATION TBC 2 HEP Tribs PEAK FLOW ESTIMATION 09002_RPS 2 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1874_10_RPS 2 HEP Intermediate REPORTING 09_1874_5_RPS 2 HEP Intermediate REPORTING 09_1242_2_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_1243_1 2 HEP Tribs PEAK FLOW ESTIMATION UN_Trib_Camac_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_448_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_UN_T02_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_UN_T02_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION

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MODEL NODE ID CFRAMS NUMBER HEP CATEGORY HYDROLOGY 09_UN_T03_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_499_1_RPS 2 HEP Intermediate REPORTING 09_360_4_RPS 2 HEP Tribs PEAK FLOW ESTIMATION 09_499_3_RPS 2 HEP Intermediate REPORTING 09_39_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_606_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_UN_T01_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_618_5 2 HEP Tribs PEAK FLOW ESTIMATION 09_586_3 2 HEP Tribs PEAK FLOW ESTIMATION 09_464_1 2 HEP Upstream Limit PEAK FLOW ESTIMATION 09_472_4_RPS 2 HEP Intermediate REPORTING 09_472_8_RPS 2 HEP Intermediate REPORTING 09_37_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_435_1_RPS 2 HEP Intermediate REPORTING 09_1870_14 2 HEP Intermediate REPORTING 09_1870_7_RPS 2 HEP Intermediate REPORTING 09_1870_8_RPS 2 HEP Intermediate REPORTING 09_1142_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_1128_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_1136_1 2 HEP Tribs PEAK FLOW ESTIMATION UN_Trib_Griffeen_U 2 HEP Upstream Limit PEAK FLOW ESTIMATION UN_Trib_Griffeen_1 2 HEP Tribs PEAK FLOW ESTIMATION UN_Trib_Camac_1 2 HEP Tribs PEAK FLOW ESTIMATION 09_396_1 2 HEP Tribs PEAK FLOW ESTIMATION 09005_RPS_Rev01 2 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09035_RPS_Rev01 2 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1655_5 2 HEP Tribs PEAK FLOW ESTIMATION 09_1870_13_RPS 2 HEP DS Limit RAINFALL RUNOFF MODELLING 09_346_3 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1245_6_RPS 3 HEP Tribs PEAK FLOW ESTIMATION 09_727_2_RPS 3 HEP Tribs PEAK FLOW ESTIMATION 09_467_8 3 HEP Tribs PEAK FLOW ESTIMATION 09_426_5_RPS 3 HEP Tribs PEAK FLOW ESTIMATION 09_1069_2_RPS 3 HEP Tribs PEAK FLOW ESTIMATION 09_1137_5 3 HEP Tribs PEAK FLOW ESTIMATION 09_501_7_RPS 3 HEP Tribs PEAK FLOW ESTIMATION 09_292_1_RPS 3 HEP Intermediate REPORTING 09_1246_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1050_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1579_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_994_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1245_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION

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MODEL NODE ID CFRAMS NUMBER HEP CATEGORY HYDROLOGY 09_467_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1126_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_727_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_994_1 3 HEP Tribs PEAK FLOW ESTIMATION 09001_RPS 3 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1137_2 3 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1246_1 3 HEP Tribs PEAK FLOW ESTIMATION 09_1050_1 3 HEP Tribs PEAK FLOW ESTIMATION 09_584_4_RPS 3 HEP Tribs PEAK FLOW ESTIMATION 09_501_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION UN_Trib_Liffey_U 3 HEP Upstream Limit PEAK FLOW ESTIMATION UN_Trib_Liffey_Inter 3 HEP Intermediate REPORTING 09_501_Trib 3 HEP Tribs PEAK FLOW ESTIMATION 09_501_Inter 3 HEP Intermediate REPORTING 09_501_Inter_1 3 HEP Intermediate REPORTING UN_Trib_Liffey_1 3 HEP Tribs PEAK FLOW ESTIMATION 09_1126_1 3 HEP Tribs PEAK FLOW ESTIMATION 09_300_1_RPS 3 HEP Intermediate REPORTING 09_299_3_RPS 3 HEP Intermediate REPORTING 09_294_1_RPS 3 HEP Intermediate REPORTING 09_1668_2_RPS 3 HEP Intermediate REPORTING 09_1668_2_RPS 3 HEP Intermediate REPORTING 09_246_4_RPS 3 HEP Tribs RAINFALL RUNOFF MODELLING 09006_RPS_Rev01 3 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09022_RPS_Rev01 3 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_600_2 4 HEP Tribs PEAK FLOW ESTIMATION 09_1444_4 4 HEP Tribs PEAK FLOW ESTIMATION 09_1839_12_RPS 4 HEP Tribs PEAK FLOW ESTIMATION 09_468_3 4 HEP Tribs PEAK FLOW ESTIMATION 09_611_3 4 HEP Tribs PEAK FLOW ESTIMATION 09_1060_3 4 HEP Tribs PEAK FLOW ESTIMATION 09_1450_U 4 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1464_5_RPS 4 HEP Intermediate REPORTING 09_1464_2_RPS 4 HEP Intermediate REPORTING 09_1464_1_RPS 4 HEP Tribs PEAK FLOW ESTIMATION 09_1444_U 4 HEP Upstream Limit PEAK FLOW ESTIMATION 09048 4 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09049 4 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1839_7 4 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1452_2_RPS 4 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1251_4 5 HEP Tribs PEAK FLOW ESTIMATION 09_1535_7_RPS 5 HEP Tribs PEAK FLOW ESTIMATION

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MODEL NODE ID CFRAMS NUMBER HEP CATEGORY HYDROLOGY 09_566_U 5 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1251_1 5 HEP Upstream Limit PEAK FLOW ESTIMATION 09_566_1 5 HEP Tribs PEAK FLOW ESTIMATION 09_181_1 5 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1535_1 5 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1853_7_RPS 6 HEP Tribs PEAK FLOW ESTIMATION TBC 6 HEP Tribs PEAK FLOW ESTIMATION 09_782_3_RPS 6 HEP Tribs PEAK FLOW ESTIMATION 09_1210_2_RPS 6 HEP Tribs PEAK FLOW ESTIMATION 09_1490_7 6 HEP Tribs PEAK FLOW ESTIMATION 09_200_2_RPS 6 HEP Tribs PEAK FLOW ESTIMATION 09_1533_U 6 HEP Upstream Limit PEAK FLOW ESTIMATION 09_356_U 6 HEP Upstream Limit PEAK FLOW ESTIMATION 09_322_U 6 HEP Upstream Limit PEAK FLOW ESTIMATION 09_454_Trib 6 HEP Tribs PEAK FLOW ESTIMATION 09_429_3 6 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1649_2_RPS 6 HEP Upstream Limit PEAK FLOW ESTIMATION 09_322_1 6 HEP Tribs PEAK FLOW ESTIMATION 09_454_Inter 6 HEP Intermediate REPORTING 09_321_1_RPS 6 HEP Intermediate REPORTING 09_1649_9_RPS 6 HEP Tribs PEAK FLOW ESTIMATION TBC 6 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1534_U 6 HEP Upstream Limit PEAK FLOW ESTIMATION TBC 6 HEP Gauging Stations CATCHMENT FLOW CALIBRATION TBC 6 HEP Tribs PEAK FLOW ESTIMATION 09_1490_DSL 6 HEP DS Limit CATCHMENT FLOW CALIBRATION 09047_RPS 7 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_411_5_RPS 7 HEP Tribs PEAK FLOW ESTIMATION 09_1055_3_RPS 7 HEP Tribs PEAK FLOW ESTIMATION 09_371_U 7 HEP Upstream Limit PEAK FLOW ESTIMATION 09_707_U 7 HEP Upstream Limit PEAK FLOW ESTIMATION 09024_RPS 7 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09036_RPS 7 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1557_3_RPS 7 HEP Tribs PEAK FLOW ESTIMATION 09_1305_2_RPS 7 HEP Upstream Limit PEAK FLOW ESTIMATION 09_Trib_Morrell_U 7 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1597_1 7 HEP Tribs PEAK FLOW ESTIMATION 09_371_1 7 HEP Tribs PEAK FLOW ESTIMATION 09_540_6_RPS 7 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1602_1_RPS 7 HEP Tribs PEAK FLOW ESTIMATION 09_706_1 7 HEP Tribs PEAK FLOW ESTIMATION 09_Trib_Morrell_1 7 HEP Tribs PEAK FLOW ESTIMATION

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MODEL NODE ID CFRAMS NUMBER HEP CATEGORY HYDROLOGY 09027 7 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09045_RPS 7 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09044_RPS 7 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1627_6_RPS 7 HEP Tribs RAINFALL RUNOFF MODELLING 09_1306_1 7 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_542_3_RPS 7 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1118_6 7 HEP Tribs PEAK FLOW ESTIMATION 09_542_Inter 7 HEP Intermediate PEAK FLOW ESTIMATION 09_1650_9 8 HEP Tribs PEAK FLOW ESTIMATION 09_1211_2_RPS 8 HEP Tribs PEAK FLOW ESTIMATION 09_1650_U 8 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_363_U 8 HEP Upstream Limit PEAK FLOW ESTIMATION 09_1154_U 8 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_1517_U 8 HEP Upstream Limit RAINFALL RUNOFF MODELLING 09_588_2_RPS 8 HEP Tribs PEAK FLOW ESTIMATION 09_1517_1 8 HEP Tribs PEAK FLOW ESTIMATION 09_1519_2_RPS 8 HEP Intermediate REPORTING 09_1518_4_RPS 8 HEP Intermediate REPORTING 09_1154_1 8 HEP Tribs PEAK FLOW ESTIMATION 09_1281_2 8 HEP Tribs PEAK FLOW ESTIMATION 09_1011_7 8 HEP Tribs PEAK FLOW ESTIMATION 09_1119_5 8 HEP Tribs PEAK FLOW ESTIMATION 09007_RPS 8 HEP Gauging Stations CATCHMENT FLOW CALIBRATION 09_1296_U 8 HEP Upstream Limit 09_1519_14_RPS 8 HEP Intermediate REPORTING 09_1519_16_RPS 8 HEP Intermediate REPORTING 09_1519_8_RPS 8 HEP Intermediate REPORTING 09_1650_2 8 HEP Intermediate REPORTING 09_DSL_01 8 HEP DS Limit CATCHMENT FLOW CALIBRATION 09_625_U 9 HEP Upstream Limit PEAK FLOW ESTIMATION 09_581_U 9 HEP Upstream Limit PEAK FLOW ESTIMATION 09_591_U 9 HEP Upstream Limit PEAK FLOW ESTIMATION 09_591_1 9 HEP Tribs RAINFALL RUNOFF MODELLING 09_605_2_RPS 9 HEP Tribs PEAK FLOW ESTIMATION 09_1876_5_RPS 9 HEP DS Limit CATCHMENT FLOW CALIBRATION

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5.6 DETAILS ON DIFFERENT HYDROLOGICAL MODELLING METHODS

5.6.1 Rainfall Runoff Catchment Modelling – MIKE NAM

Hydrological modelling for the GIS-delineated catchments of the identified HEPs will be carried out using NAM rainfall-runoff simulator of the MIKE 11 modelling software. MIKE NAM is a deterministic lumped hydrological rainfall-runoff model that operates by continuously accounting for the runoff and soil moisture content in three different and mutually interrelated storages (nonlinear reservoirs), which represent physical elements of a catchment (surface storage, root zone and ground water storages) as illustrated by Figure 5.3 below. Being a lumped model, it treats each sub-catchment as one unit; therefore the parameters and variables considered represent average values for the catchment areas and are very sensitive as calibration parameters.

• (UMAX) - maximum water content in the surface storage– affects overland flow, recharge, amounts of evapotranspiration and intermediate flow;

• (LMAX) - maximum water in the lower zone/root zone storage– affects overland flow, recharge, amounts of evapotranspiration and intermediate flow;

• (CQOF) - overland flow coefficient– affects the volume of overland flow and recharge; • (CKIF) - intermediate flow drainage constant– affects the amount of drainage from the surface storage zone as intermediate flow; • (TOF) - overland flow threshold– affects the soil moisture content that must be satisfied for quick flow to occur; • intermediate flow threshold (TIF) - affects the soil moisture content that must be satisfied for intermediate flow to occur;

• (CK1,2) - time constant for overland flow– affects the routing of overland flow along catchment slopes and channels; • (TG) - deep groundwater recharge threshold - affects the soil moisture content that must be satisfied for groundwater recharge to occur; • (CKBF1- time constant for deep groundwater flow) - affects the routing of groundwater recharge in the regional aquifers.

• QOF - Overland flow • QIF - Intermediate flow Figure 5.3: NAM model structure (SWRBD/RPS, Reference 27)

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MIKE NAM utilises all available rainfall data as hydrological model input, together with parameters to describe catchment response. The post calibration output is a flow trace matching the time series of available rainfall data. This will provide hydrograph shape, and an extended AMAX series from which peak flows can be derived using growth curves as required (refer to Section 5.4.2). The benefit of this approach is that a discharge file will be generated for the entire length of rainfall record available, as opposed to limiting the AMAX series to the length of the hydrometric record. This maximises the length of AMAX series from which to calculate peak flows per AEP (using derived growth curves where required). Furthermore, using the NAM hydrological models, simulation of the typical shape of the hydrograph as a response of the catchment area for the peak flows per return periods will be undertaken. This will provide the key parameters describing the shape of the hydrograph per event, such as the time of concentration – Tc, rising time of the hydrograph – Tp, recession time of the hydrograph – Tr and their ratios.

5.6.1.1 NAM Parameters

The NAM model includes 5 state variables and 9 model parameters. The state variables are: SS - initial snow storage; U - upper zone storage (U/Umax); L - lower zone storage (L/Lmax); QR1 - Initial runoff from routing reservoir #1; QR2 - Initial runoff from routing reservoir #2.

The model parameters are:

• Umax (mm) – the maximum water content in the surface storage;

• Lmax (mm) the maximum water content in the root zone storage;

• CQOF - is the overland flow runoff coefficient;

• CKIF (hrs) – the interflow time constant routing parameter;

• CKBF - is the time constant for deep groundwater flow;

• CK12 - is the time constant for overland flow routing, this is an important parameter and it depends on the size of the catchment and how fast it responds to rainfall;

• TOF - time transfer factor for the overland storage;

• TIF - time transfer factor for the interflow storage;

• TG - time transfer factor for the groundwater storage.

Based on previous NAM hydrological modelling studies (including parameters sensitivity analysis), RPS and HydroLogic will use a physically-based approach to estimate the values of some of the key NAM model parameters using a decision tree and utilising the available GIS data sets for the Eastern CFRAM Study area. The following parameters will be estimated based on a decision tree methodology: • The surface storage Umax [mm] is defined as the volume of water stored on foliage and generally on the surface following rainfall, but also in dips and puddles and subsurface non groundwater storage, which can feed the interflow discharge component. It is usually in the

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order of 5-25 [mm], is available for immediate evaporation and excludes moisture stored in soil and subsoil. Steep ground tends to have less surface storage compared to for example drumlin landscapes, also for large vegetation types i.e. trees or shrub the storage is greater compared to grass or rocky surfaces. Calibration of this parameter is often achieved through assessment of the overall water balance; this requires good evaporation information ideally varying on a weekly or monthly interval. Once the surface storage is depleted interflow ceases to exist in the model and evaporation takes place from the lower or soil moisture storage at a slower rate. Overland flow is only present while the surface storage is fully replenished in the model. • The maximum amount of overland flow is given by the overland flow runoff coefficient CQOF [/], which is often higher compared to other deterministic models, as the actual runoff is also proportioned in relation to the soil moisture at each time step. • The time constant for interflow CKIF [hour] controls how fast water can be discharged from the surface storage into the stream, though as with the overland flow this is proportioned by the ratio of available soil moisture to the total soil moisture storage. • The discharge from the ground water reservoir is simulated through a recession relationship defined by a time constant CKBF [hour]. As the constant already suggests the flow simulated is baseflow, i.e. a very slowly varying stream flow component, often attributed to the groundwater reservoir, though in some instances this might also be due to large peat layers in the catchments. Attempts have been made to simulate this behaviour through splitting the baseflow into two components with varying discharge time constants often found in peat catchments in wet and dry seasons.

As part of the Water Framework Directive further characterisation study ‘An Integrated Approach to Quantifying Groundwater and Surface Water Contributions of Stream Flow (Reference 27)’, a series of decision tables were developed to determine four NAM parameters - the coefficient for overland flow (CQOF), the time constant for overland flow (CK1,2), the surface storage zone (Umax), the time constant for interflow (CKIF) and the time constant for baseflow (CKBF). The decision tables were based on the assessment of GIS datasets, as well as expert judgement (e.g. gravels scenario).

An example decision tree for determination of the NAM model parameters is presented in Table 5.3 below (Umax). Similar decision trees (lookup tables) are available for the rest of the NAM model parameters.

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Table 5.3: Example decision table for the determination of the NAM surface storage zone (Umax), (SWRBD, RPS, 2008)

Range of GIS Poorly NAM NAM estimation Corine Slope Lakes drained Urban Parameter parameter for sub- soils value catchment

>5% High Forestry percentage & Semi- 15 -25 1A, 2B, 3C of poorly natural drained areas Steep slope soils (>5%): (>50%): lower end upper end of limit of limit If >2%

Forestry 0 Lakes urban

Umax – 5% & > 1%: areas: 10 – 20 1B, 2C (mm) Pastures 15 – upper

> 40% 20 end of

Relatively limit Low flat slope percentage (<5%): of poorly upper end Forestry drained of limit 0%, soils Pastures 8 - 15 (<20%): 4A, 4B <40% and lower end Bare rock of limit >20%

The example decision table presented in Table 5.3 is to determine the value of Umax (surface storage zone) for each catchment. Umax is controlled by vegetation - which can intercept moisture - and depressions in a catchment. The amount of water that is stored in the surface storage zone is also controlled by evaporation and drainage to the subsurface. The range of Umax values are controlled by the proportion of forestry, agricultural land and outcropping rock. Forestry has a higher potential to intercept the moisture from rainfall compared to agricultural land and bare rock. The ‘Corine’ column in Table 5.3 gives upper and lower limits of percentage cover of forestry, agricultural land and outcropping rock. The catchment under investigation is assigned to one of the three categories (depending on its land cover), with a broad range of Umax values given in the adjacent column.

The selected value of Umax for a catchment can be further refined dependent upon the average slope, coverage by lakes, coverage by wet soils and the amount of urban area. For example, the Umax value would be expected to be at the lower end of the land cover ranges if the average slope of a catchment is relatively steep (>5%). Also, a high percentage of lakes will act as storage resulting value of Umax at the upper end of the land cover ranges. Similarly, a high proportion of wet soils and urban areas will intercept rainfall and affect Umax.

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River catchments are not necessarily composed of one aquifer type and more often than not contain mixed aquifers. The method for estimating the NAM parameters CQOF, CKIF and CKBF is based on single aquifer types. For the mixed aquifer scenarios an area percentage of each aquifer type in the catchment approach will be used to estimate these NAM parameters.

The initial estimation of the four parameters (Umax, CQOF, CKIF and CKBF) driving the rainfall-runoff process will be done using the available GIS datasets, namely:

GSI_BedrockAndSG_AquifersUnion_pg_110830 - aquifer type GSI_Soils_WetDry_pg_110830 - poorly drained soils GSI_SubsoilPermeability_pg_110830 – permeability GSI_Vulnerability_pg_110830 – ground water vulnerability DTM Corine Land Use GIS layer

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Bedrock Aquifer Type and Groundwater Vulnerability

Sub Soil Permeability & Soil Drainage

Land Use

Figure 5.4: Available GIS datasets for deriving the NAM model parameters in HA09

The parameters for the NAM modelling that have not been estimated based on the aforementioned WFD Study are the maximum soil moisture content in the root zone, storage available for vegetative transpiration (Lmax, measured in mm) and the threshold values for overland flow, intermediate flow and deep groundwater flow (the L/Lmax value at which that component of flow occurs).

The effects on the catchment hydrology of lakes and other water bodies not on modelled watercourses are captured in the NAM modelling process through the Umax (surface storage zone) parameter which is derived from the water and water bodies categories within the GSI Soil Drainage and Corrine land use data sets respectively. The adoption of appropriate values for this ensures the attenuating effects of off-line lakes and surface depressions within the catchment are represented accurately.

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Based on NAM modelling of the Neagh Bann catchment study in (Reference 28) it is suggested to use the following default values for the initial modelling of further catchments:

• Maximum soil moisture content in the root zone storage Lmax: 120mm;

• Threshold value for overland flow: 0.6;

• Threshold value for interflow: 0.5;

• Threshold value for groundwater flow: 0.4.

The value of these parameters should be altered during the modelling to improve the correlation and water balance. There are certain circumstances within catchments that will indicate the threshold values. If a catchment has mainly dry soils or high permeability sub-soils then the threshold value for overland flow will tend towards 1 i.e. the root zone storage must be saturated before overland flow will occur. If a catchment contains mainly exposed Karst aquifers or gravel aquifers then the threshold value for overland flow will tend towards 1 and the threshold value for intermediate flow will tend towards zero i.e. flow will be routed to the intermediate component almost as soon as precipitation occurs.

HydroLogic is currently looking at developing ArcGIS scripts that will automate the estimation of the NAM model parameters: - Based on the defined HEP and delineated catchment area using the national DTM provided by OPW; - Overlay the catchment boundary (polygon) with the available GIS layers. - Use the look-up decision trees (see tables) to initially estimate the 4 parameters: Umax, - Write / update the NAM model input files.

This methodology will provide a more realistic narrowed range of values for the most sensitive NAM model parameters. For example, if using the decision tree one estimates from the GIS data for a given HEP catchment area Umax = 15-25 [mm], initially the mid value will be used to instantiate the NAM model (Umax = 20 [mm], in this case). If measured data is available (water levels / flows) at HEPs Gauging Station check points further autocalibration procedures will be used to fine-tune the model parameters and generate a better fit between the measured and simulated flows, as described below. Note that during the autocalibration process the allowable values for the model parameters (Umax in this example) will be set within the estimated narrowed bands, Umax = 15-25 [mm] in this case. For HEPs without gauged hydrometric data, NAM model autocalibration procedure will not be carried out and the values of the model parameters estimated by the decision tree approach will be used for hydrological modelling. These will then be revisited if hydraulic model simulation at NAM check points indentifies differences between hydraulic model flow and observed flow at the hydrometric station. (Refer to Figure 5.2: Two Phased Hydrology Analysis Process Chart).

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5.6.1.2 MIKE NAM Calibration

Where gauged data is available, i.e. at the 19 locations along modelled watercourses as shown in Figure 4.2, MIKE NAM models will be calibrated to produce a discharge file as similar as possible to the actual gauged data. The calibration process will involve running the entire rainfall record through the NAM model and comparing the output to the gauge data. The NAM model software autocalibration function will initially be used for each of the gauged catchment rainfall-runoff models. When the models are run in autocalibration mode the software allocates appropriate values to the NAM parameters and uses the rainfall and evaporation data (as provided by Met Éireann) to produce a discharge file as similar as possible to the actual gauged data. Generally this autocalibration exercise results in a roughly calibrated model and comparison plots are produced to compare the discharge file with the gauged data. Depending on the outcome of the autocalibration exercise a second phase of calibration can be undertaken by manually adjusting NAM parameter values until satisfactory calibration is achieved. Part of the NAM model calibration process will include a mass balance check to ensure the amount of water entering and exiting the run-off model is balanced and consistent with gauge records. This analysis will be undertaken on the overall gauge records and for specific notable events within the gauge record for example Hurricane Charley.

o Optimisation Stage 1: optimising the water balance using multi-objective genetic algorithm. o Optimisation Stage 2: optimising the hydrograph shape using multi-objective genetic algorithm.

The objective function can be a combination from different error measures (goodness of fit) between the measured flow and the computed flow, such as Root Mean Square Error (RMSE); Coefficient of correlation (CC) and determination (COD); Coefficient of variance (CV); Second momentum (MM); Proportional error estimate (PEE) specialising on both, peak and base flows. Additional tools for analysis of the calibrated NAM models will be also provided, see Figure 5.5.

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Figure 5.5: Visualization tools for the NAM model calibration component.

It may be necessary in urban areas such as the Camac and Poddle Rivers to utilise the Urban function of MIKE NAM to more accurately simulate runoff in highly impervious areas. Where Urban models are created, they will be joined with the NAM models in combined hydrological models. As outlined in Sections 5.4.3.3 and 5.4.4, for catchment flow calibration, where NAM models are used at upstream limits HEPs (upstream boundary conditions), the calibration of the models for a hydrometric station which is further downstream will be done by setting-up an integral NAM model at the hydrometric station which will have the sub-catchments of the upstream models included. For example, Hydraulic Model 4 at Maynooth has two upstream limit NAM models with a HEP Gauging Station Check Point further downstream. In this case, three NAM models will be set up - two NAM models at the HEP upstream limits and one joint NAM model at the HEP gauging station in order to undertake the catchment based NAM model calibration.

For NAM models at HEP tributaries which have significant contributing flows to the main stream as hydrodynamic model (MIKE 11), a joint hydrological and hydrodynamic calibration will be carried out.

Based on the initial HEPs catchments analysis, it is estimated that approximately 30% of the NAM models will have gauging stations that will enable full NAM model calibration. Typically for these models our experience is that 70% of the available data is used for model calibration with the remainder held for validation along with any new flow data that may become available during the modelling period.

The RPS hydrology methodology is not dependent on simulated rainfall profiles being identified as the complete rainfall record will be input to the NAM models and following calibration against hydrometric

IBE0600Rp0008 126 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL gauge records, the NAM modelling will determine the rainfall events which will dictate the size of the index flood, Qmed. If the rainfall radar trials are successful and this method of analysis is rolled out to the entire Eastern CFRAM area the rainfall inputs used in the NAM modelling process will be generated from a combination of rain gauge data and radar data using the methodology outlined in Appendix C. In the event that the rainfall radar approach is not adopted the rainfall profiles will be derived from gauge data alone and distributed using Thessian polygons or similar approaches, with reference to the FSU Depth Duration Frequency (FSU Work Package 1.2 – Reference 13) recommendations where appropriate.

5.6.2 Institute of Hydrology Report No. 124

This statistical method was developed by the Institute of Hydrology (IH) in the UK for small catchments (<25km2) (Reference 24). It was developed in 1994 and does not contain any Irish catchment data. However, it is the preferred method for smaller catchments in Ireland and it is still recommended by OPW.

There are two applications within the IoH 124 report:

1. Replacement of Time to Peak Equation in FSSR Unit Hydrograph method (refer to Section 5.6.4) for small catchments so that a hydrograph can be generated

2. Use of QBAR estimation equation by catchment characteristics and a growth curve to estimate Qt where peak flows only are required. The Factorial Standard Error associated with this method for QBAR estimation is 1.651. The relationship between

QBAR and Qmed must then be derived from relevant gauging data so that Qmed can be calculated.

5.6.3 Flood Studies Update (FSU) Qmed Estimation

As referred to in Section 5.4 the OPW have prepared an extensive update of the Flood Study Report for Ireland. This is referred to as the FSU Programme and is to provide improved methods of extreme rainfall and flood estimation at both gauged and un-gauged locations in Ireland (FSU, Alpha Testing Users Guide – Reference 29). It has been in development since 2004 and is in the final stages of completion.

A software application is under development however pending its completion the OPW provided excel automated spreadsheets for the following calculations:

1. Qmed estimation for un-gauged sites based on catchment descriptors and factored based on gauging information at suitable pivotal sites. The effects of lakes and other water bodies not on modelled watercourses on hydrology in un-gauged catchments are captured in the regression equation estimate through the FARL parameter (an index of flood attenuation by

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rivers and lakes). The FARL parameter has been assessed on a catchment by catchment basis under the FSU and is included within the FSU equation to ensure that the attenuating effect of off-line lakes within the catchment is represented accurately. 2. Pooled Frequency Analysis to estimate the appropriate growth curve and associated factor for obtaining Q values for required return periods. This process also uses pivotal stations to compile pooling groups of data. 3. Generation of Hydrograph Shape using the parametric method based on catchment descriptors and the Q value obtained in Step 2. This process also uses pivotal site data, but the number of stations across the country deemed suitable for this purpose is smaller than

Qmed estimation.

The factorial standard error value associated with this method is 1.37 for Qmed estimation.

The recommended method for flood estimation in small catchments (approx <25km2) is still IoH 124 as there is not enough gauged data from small catchments to serve as pivotal sites in the FSU as of yet.. OPW are working on augmenting the gauged data with smaller catchments at present.

If hydrographs are required as model input at HEP tributary locations consideration will be given to applying the FSU derived flood peak to a hydrograph shape derived from the FSSR Unit Hydrograph method. Whilst FSU hydrograph shape generation is relatively new, FSU derived flows may be better applied using a bridging method between the FSU and the Flood Studies Supplementary Report (FSSR) rainfall runoff Unit Hydrograph Method. The report on Work Package 3.5 of the FSU (Reference 30) discusses such an approach calling it an Interactive Bridge Invoking the Design Event Method (IBIDEM) and aims at providing a bridge between the FSU method of estimating a design flood hydrograph and the FSSR design method that it replaces. If it is found that the FSU Hydrograph Shape generator does not yield usable hydrographs e.g. infinite receding limb; inaccurate representation of water volume, this option will be considered. It may also be the case that nearby NAM model outputs provide an indication of catchment response and a typical hydrograph shape. This will also be considered when deriving appropriate hydrograph shapes to inform the overall process.

5.6.4 FSSR Unit Hydrograph Method

The FSSR Unit Hydrograph method is a deterministic method for estimating design hydrographs (Reference 25). It is a rainfall runoff method based on estimating a unit hydrograph using catchment descriptors and estimating critical rainfall for design storm duration i.e. rainfall and catchment response to develop the storm hydrograph.

The Flood Studies Report undertook a comprehensive analysis of rainfall and discharge data in UK and Ireland up to 1970 and contains a series of maps of various quantities derived for rainfall data. Regional analysis was undertaken in the UK, but Ireland was taken as a single region which is widely accepted as an inaccurate representation of the east-west differences on the Island. In cases where this method is applied to Upstream Limit or Tributary HEPs in this Study, appropriate rainfall profiles will be used based on the rainfall data analysis described in Section 5.1.3.

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A spreadsheet calculation will be used to input relevant catchment descriptors to calculate Time to peak, data intervals, storm duration, rainfall amount for the required return period, standard percentage run off and base flow. ISIS software then facilitates an automated convolution process to draw the hydrograph shape and provide the Q and time data necessary for hydraulic model input.

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6 DODDER CFRAM STUDY AND TOLKA FLOOD STUDY DETAILED METHODOLOGY REVIEW

6.1 CONTRACT SPECIFIC METHODOLOGY – DODDER CFRAM STUDY

6.1.1 Phase 1: Hydrological Analysis, Hydraulic Modelling & Flood Mapping

RPS proposes to review the hydrological analysis undertaken during the Dodder CFRAM Study by conducting an initial high-level analysis of the study area. This will determine the areas where there have been potentially significant changes in the catchment since completion of the Study. This analysis will form the basis for selecting the hydrometric stations and sub-catchments to be assessed in accordance with the specification. Those selected will include areas where significant changes in the catchment have been identified, and a representative sample of the three hydrometric stations listed in the Hydrology Report and numerous sub-catchments located within the Study area. RPS will generate a pro-forma which will list all of the checks to be carried out, including:

• Assessment of the hydrometric gauging station rating review including a determination of the impact should data which has become available since the completion of this element of the Dodder study will be included. Details of the potential impact on the modified annual maximum series and growth curve will be established;

• Assessment of the impact of adopting the use of FSU as an alternative to other hydrological methods to enable comparison of site parameters and growth curves;

• Review of the hydro-meteorological data acquired within the chosen sample area, ensuring that all available data has been considered (including data in relation to any significant events which has become available since the completion of the Dodder CFRAM Study);

• Review the statistical analysis methods and conclusions of the hydro-meteorological data acquired for the sample area. Assessment will include data which has become available since completion of the Dodder CFRAM Study and a determination will be made if this changes the applicability of the methodology used and associated assumptions;

• Review of the catchment boundaries and sub-catchment boundaries for each of the selected HEPs;

• Check to ensure that design parameters including peak flows, hydrographs and flood volumes have been determined for all design event probabilities and for all HEPs. A review of the number and location of HEPs will also be conducted;

• A review of the FSSR 16 and IOH124 input files for all sub-catchments within the sample area;

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• Review of hydrological calibration and validation.

RPS may select additional sub-catchments for further assessment in the event that the above review is deemed inconclusive. Following completion of the review, RPS will report any recommendations deemed necessary, for updating the hydrological analysis in the Dodder CFRAM Study to the OPW.

RPS propose to review the hydraulic modelling undertaken during the Dodder CFRAM Study by assessing a representative sample of the eight individual river models in the Dodder CFRAM Study area, in accordance with the specification. The method for selecting these models will initially focus on those areas identified as having undergone significant changes in the catchment (during the high-level analysis as part of the hydrological analysis). Further models to be assessed, if required, will be selected at random, however, a check will be made to ensure that at least one of the selected models is a 1D-2D model type, contains both HPWs and MPWs and requires a defence failure scenario to be modelled. Should this not be case, one model will be discarded and the random selection procedure will be repeated until the aforementioned criteria are met. RPS will generate a pro-forma which will list all of the checks to be carried out, including:

• survey information meets the requirements as set out in Appendix D of the generic CFRAM specification, and recording of any flood risk management measures which have been implemented since the commencement of the Dodder CFRAM Study and which have not been captured in the Dodder survey information;

• a dynamic hydraulic model has been developed for all HPWs and MPWs, and their associated floodplains, and that 1D-2D models have been implemented where necessary using the required software;

• channel and floodplain roughness coefficients are appropriate, all hydraulically significant structures (as per the surveys) are included, model resolution and boundary conditions are appropriate (as specified by the hydrological analysis);

• calibration of models has been successfully carried out at HEPS and that design flood flows for each AEP are maintained along each watercourse. A check will be made that four previous flood events have been used, where data is available, and all flood events yielding potential calibration data since the completion of the Dodder CFRAM Study hydraulic analysis will be recorded.

• the required model design runs have been completed to meet the requirements of the flood mapping deliverables (see below);

• sensitivity tests have been undertaken for all forms of modelling, with a number of appropriate factors adjusted, with an indication given on the robustness and sensitivity of each model;

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• two failure scenarios have been modelled for each of the existing flood defence assets present within the model area;

• assessment of the adequacy of the coastal modelling approach and the tidal boundary data used.

Following the above review, RPS will report any recommendations deemed necessary for updating the hydraulic modelling in the Dodder CFRAM Study to the OPW.

RPS proposes to review the flood mapping undertaken during the Dodder CFRAM Study by assessing each flood map in accordance with the CFRAM specification. RPS will generate a pro- forma which will list all of the checks to be carried out, including:

• A Flood Map has been produced for each source of flooding for all AFAs, and for each scenario (current, MRFS and HEFS) as defined in the specification;

• All Flood Extent Maps include an indicator of the degree of confidence, tables of peak flows for all modelled design event probabilities at each HEP, tables of peak flood levels for all AEPs at all nodes and appropriate points within modelled coastal domains and indicate areas benefiting from flood defences;

• All Flood Zone Maps show Flood Zones A, B and C (as per ‘Guidelines on the Planning System and Flood Risk Management’);

• All Flood Depth Maps show the depths of flooding, with appropriate classifications;

• All Flood Velocity Maps show velocities of floodplain flow, with appropriate classifications;

• All Flood Hazard Function Maps show an appropriate function of flood hazard;

• Specific flood risk maps showing the indicative number of inhabitants, types of economic activity, economic risk density and general risk maps for all other risk indicators have been produced.

Following the above review, RPS will report any recommendations deemed necessary, for updating the flood mapping in the Dodder CFRAM Study to the OPW. This will include a discussion on the likely influence of the findings of the hydrological and hydraulic review on the flood mapping.

6.1.2 Phase 2: Flood Risk Management Options

Following the completion of Phase 1 (Section 6.1.1), RPS will undertake a review of the recommended flood risk management options identified in the Dodder CFRAM Study report. This will reflect work undertaken since commencement of the Dodder CFRAM Study, and other changes in timings or prioritisations to the recommendations as required by OPW and / or Local Authorities.

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RPS will ensure that the recommendations and proposed measures (reviewed and updated as necessary) are in line with the overall strategy for HA09. RPS will incorporate these findings, recommendations and proposed measures and other material as necessary into the Flood Risk Management Plan that is to be developed for all of the Hydrometric Area 09 as part of the Eastern CFRAM Study.

RPS proposes to further develop the methodology for reviewing the flood risk management options following completion of the review of the hydrological analysis, hydraulic modelling and flood mapping as the detailed methodology will be dependent on the outcome of these tasks. For example, in the event that the flood mapping is concluded as being accurate, it may be the case that the flood risk management options will still alter due to the availability of new social data-sets. At this stage RPS will also review the flooding mechanisms considered to ensure that all relevant issues have been considered, for example flooding of basements and semi-basements may be an issue in some areas.

The updated methodology will be issued as a Technical Note, expanding on the proposed methodology presented above.

6.1.3 Phase 3: Flood Risk Management Plan

Following the completion of Phase 2 (Section 6.1.2), RPS will incorporate the findings, recommendations and proposed measures and any other material as necessary into the overall Flood Risk Management Plan for HA09.

RPS propose to give further details on the methodology for reviewing the flood risk management plan following completion of the review of the flood risk management options as the final methodology will to a degree be dependent on the outcome of this task. For example, should the review of flood risk management options conclude that additional measures are required; the Plan will have to incorporate details on the subsequent SEA measures required.

The updated methodology will be issued as a Technical Note, expanding on the methodology given above.

6.2 CONTRACT SPECIFIC METHODOLOGY – TOLKA FLOOD STUDY

6.2.1 Phase 1: Hydrological Analysis, Hydraulic Modelling & Flood Mapping

RPS proposes to review the hydrological analysis undertaken during the Tolka Flood Study by conducting an initial high-level analysis of the study area. This will determine the areas where there have been potentially significant changes in the catchment since completion of the Study. This analysis will form the basis for selecting the hydrometric sub-catchments to be assessed in accordance with the specification. Those selected will include areas where significant changes in the catchment have been identified, and a representative sample of the thirty-five sub-catchments listed in Appendix C1.2 of the Tolka River Modelling Report. This assessment differs to that proposed in

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Section 6.1.1 for the Dodder CFRAM Study due to the absence of recorded flows in any of the sub- catchments and the resulting use of the FSSR16 rainfall runoff method for the Tolka Study. The selection of the sub-catchments will aim to include at least one of the seven urban sub-catchments and at least one rural sub-catchment. RPS will generate a pro-forma which will list all of the checks to be carried out, including:

• Verification of the catchment characteristics used for input into the rainfall run-off model;

• A determination of the impact should data which has become available since the completion of the study be included;

• Assessment of the impact in adopting the use of FSU as an alternative to other hydrological methods;

• Review of the hydro-meteorological data acquired within the chosen sample area, ensuring that all available data has been considered (including data in relation to any significant events which has become available since the completion of the Tolka Flood Study);

• Review the statistical analysis methods and conclusions of the hydro-meteorological data acquired for the sample area. Assessment will include data which has become available since completion of the Tolka Flood Study and a determination will be made if this changes the applicability of the methodology used and assumptions made;

• Review of the catchment boundaries and sub-catchment boundaries for each of the selected HEPs;

• Check to ensure that design parameters including peak flows, hydrographs and flood volumes have been determined for all design event probabilities and for all HEPs. A review of the number and location of HEPs will also be conducted;

• A review of the FSSR 16 input files for all sub-catchments within the sample area;

• Review of hydrological calibration and validation.

RPS may select additional sub-catchments for further assessment in the event that the above review is deemed inconclusive. Following completion of the review, RPS will report any recommendations deemed necessary, for updating the hydrological analysis in the Tolka Flood Study to the OPW.

RPS propose to review the hydraulic modelling undertaken during the Tolka Flood Study by assessing the Infoworks RS river model constructed for the project, in accordance with the specification. RPS will generate a pro-forma which will list all of the checks to be carried out, including:

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• survey information meets the requirements as set out in Appendix D of the generic CFRAM specification, and recording of any flood risk management measures which have been implemented since the commencement of the Tolka Flood Study which were not included in the survey information;

• a dynamic hydraulic model has been developed for all HPWs and MPWs, and their associated floodplains, and that 1D-2D models have been implemented where necessary using the required software;

• channel and floodplain roughness coefficients are appropriate, all hydraulically significant structures (as per the surveys) are included, model resolution and boundary conditions are appropriate (as specified by the hydrological analysis);

• calibration of the model has been successfully carried out at HEPS and that design flood flows for each AEP are maintained along each watercourse. A check will be made that four previous flood events have been used, where data is available, with all flood events yielding potential calibration data since the completion of the Tolka Flood Study hydraulic analysis being recorded.

• the required model design runs have been completed to meet the requirements of the flood mapping deliverables (see below);

• sensitivity tests have been undertaken for all forms of modelling, with a number of appropriate factors adjusted, with an indication given on the robustness and sensitivity of each model;

• two failure scenarios have been modelled for each of the existing flood defence assets present within the model area;

• assessment of the adequacy of the coastal modelling approach and the tidal boundary data used.

• the model has been updated to include all of the flood risk management and relief measures implemented since the completion of the initial model in 2003.

Following the above review, RPS will report any recommendations deemed necessary for updating the hydraulic modelling in the Tolka Flood Study to the OPW.

RPS proposes to review the flood mapping undertaken during the Tolka Flood Study by assessing each flood map in accordance with the generic CFRAM specification. RPS will generate a pro-forma which will list all of the checks to be carried out, including:

• A Flood Map has been produced for each source of flooding for all AFAs, and for each scenario (current, MRFS and HEFS) as defined in the specification;

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• All Flood Extent Maps include an indicator of the degree of confidence, tables of peak flows for all modelled design event probabilities at each HEP, tables of peak flood levels for all AEPs at all nodes and appropriate points within modelled coastal domains and indicate areas benefiting from flood defences;

• All Flood Zone Maps show Flood Zones A, B and C (as per ‘Guidelines on the Planning System and Flood Risk Management’);

• All Flood Depth Maps show the depths of flooding, with appropriate classifications;

• All Flood Velocity Maps show velocities of floodplain flow, with appropriate classifications;

• All Flood Hazard Function Maps show an appropriate function of flood hazard;

• Specific flood risk maps showing the indicative number of inhabitants, types of economic activity, economic risk density and general risk maps for all other risk indicators have been produced.

Following the above review, RPS will report any recommendations deemed necessary, for updating the flood mapping in the Tolka Flood Study to the OPW. This will include a discussion on the likely influence of the findings of the hydrological and hydraulic review on the flood mapping.

6.2.2 Phase 2: Flood Risk Management Options

Following the completion of Phase 1 (Section 6.2.1), RPS will undertake a review of the recommended flood risk management options. This will reflect work undertaken since commencement of the Tolka Flood Study, and other changes in timings or prioritisations to the recommendations as required by OPW and / or Local Authorities.

RPS will ensure that the recommendations and proposed measures (reviewed and updated as necessary) are in line with the overall strategy for HA09. These findings, recommendations and proposed measures and other material as necessary will be incorporated into the overall Flood Risk Management Plan to be developed for all of Hydrometric Area 09.

RPS proposes to further develop the methodology for reviewing the flood risk management options following completion of the review of the hydrological analysis, hydraulic modelling and flood mapping as the detailed methodology will be dependent on the outcome of these tasks. For example, in the event that the flood mapping is concluded as being accurate, it may be the case that the flood risk management options will still alter due to the availability of new social data-sets.

The updated methodology will be issued as a Technical Note, expanding on the proposed methodology presented above.

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6.2.3 Phase 3: Flood Risk Management Plan

Following the completion of Phase 2 (Section 6.2.2), RPS will incorporate the findings, recommendations and proposed measures and any other material as necessary into the overall HA09 Flood Risk Management Plan.

RPS propose to give further details on the methodology for reviewing the flood risk management plan following completion of the review of the flood risk management options as the final methodology will to a degree be dependent on the outcome of this task. For example, should the flood risk management options conclude that additional measures are required; the Plan will have to incorporate details on the subsequent SEA measures required.

The updated methodology will be issued as a Technical Note, expanding on the methodology given above.

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7 DETAILED METHODOLOGY REVIEW

The discussion regarding data collection, gaps and outstanding information, presented in Section 2 of this Eastern CFRAM Study Inception Report - HA09 (Liffey), informs the methodology risks and opportunities review.

The following general mechanisms are available for methodology amendments:

• Technical notes – used to expand or update methodology at appropriate project planning stages;

• Inception report (this report) – used to expand or update methodology in response to formal data review six months into the contract; and

• Agreed changes to scope of services (under Clause 2.6.2 of the National Flood Risk Assessment and Management Programme, Eastern River Basin District Catchment-based Flood Risk Assessment and Management (CFRAM) Study Stage II Tender Documents: Instructions to Tenderers) – used to add or remove specified contract items.

Given the tightly prescribed work scope and tender specification and the fact that most of the datasets are as expected in terms of quality and availability, there have been a small number of methodology amendments in the Liffey Unit of Management to date.

A brief summary of the status with regard to tendered methodology for each of the individual project tasks is as follows:

• General Requirements – there has been no methodology change with regard to level of detail, management arrangements, project inception, web-based work platform, project website, use of digital media and GIS and health and safety requirements. These activities are all either complete or currently in place and ongoing during the study. Technical training and National Technical Coordination Group participation have not yet commenced awaiting delivery/ procurement of other CFRAM Study partners however these are not currently critical path and no associated methodology changes are proposed at present. This task applies to the full extent of HA09 including the Dodder and Tolka catchments.

• Data Collection – section 2 of this report details the collection of relevant datasets and the initial phase has concluded in accordance with the tendered methodology. Further data or updates will be pursued on an as needed basis or as they emerge. Flood event response activities will remain ongoing in accordance with the Generic CFRAM Study Brief and a project specific flood event response plan is detailed in a Technical Note (Section 7.2). This task applies to the full HA09 catchment including the Dodder and Tolka catchments.

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• Flood Risk Review – this task is complete and the final report with RPS recommendations to OPW has been issued. This task applied to the full HA09 including the Dodder and Tolka catchments. The methodology for this task was updated as detailed in a Technical Note (Section 7.1).

• Surveys – there are a number of issues regarding survey contract award and subsequent delivery timescales which pose potential project time constraints for the follow on tasks of hydraulic modelling and flood mapping and may jeopardise delivery and consultation milestones in 2013. These risks and possible mitigation measures are discussed in more detail in section 7.1.

• Hydrological Analysis – section 4 of this inception report expands on the tendered hydrological methodology as applied to HA09. In addition a proposal to improve the rainfall inputs to the hydrological and hydraulic models by using RADAR rainfall data is being implemented on a staged basis as detailed in a Technical Note (Section 7.2).

• Hydraulic Analysis – there is no tendered methodology change proposed in HA09 to date.

• Flood Risk Assessment – there is no tendered methodology change proposed in HA09 to date.

• Environmental Assessment – there is no tendered methodology change proposed in HA09 to date.

• Consultation And Engagement – there is no tendered methodology change proposed in HA09 to date.

• Development Of Flood Risk Management Options – there is no tendered methodology change proposed in HA09 to date.

• Preparation Of Flood Risk Management Plans – this task applies to the full HA09 including the Dodder and Tolka catchments. There is no tendered methodology change proposed in HA09 to date.

• Reporting And Deliverables – this task applies to the full HA09 including the Dodder and Tolka catchments. There is no tendered methodology change proposed in HA09 to date.

RPS maintains a live project risk and opportunities register to consider implications for programme, quality and budget for the Eastern CFRAM Study, which is reviewed at regular project working group meetings. This process has identified a small number of risks and opportunities that have a direct bearing on task methodology which are discussed in the following report sections.

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7.1 RISKS AND PROPOSED METHODOLOGY AMENDMENTS

Flood Risk Review – Technical Note 1 (IBE0600 TN0001) details an updated methodology for flood risk review (FRR) in the Eastern study area based on the progress with the Preliminary Flood Risk Assessment (PFRA) between time of generic specification and tender and the Eastern CFRAM Study FRR. Updated consultation, scoring and modelling approaches were set out in the document in order to progress the task in the absence of some data sets (such as flood defence databases) which were not available at the time of the FRR due to the delayed start date of the overall project.

Surveys – the Generic CFRAM Study brief requires the following surveys:

• Defence asset condition survey – project specific specification applies to HA09, these surveys are not yet scheduled to commence (programmed for June 2012 – September 2012 these surveys are subject to locations being identified by structure and cross section survey contracts), no methodology change is proposed at this stage.

• Property survey – project specific specification applies to HA09, these surveys are not yet scheduled to commence, no methodology change is proposed at this stage.

• Floodplain survey – project specific specification applies to HA09, the LiDAR survey is progressing at national level, due to programme slippage RPS have not yet been able to undertake any data quality assessment, RPS have undertaken additional work to review the survey extents so that complete coverage of revised Areas of Further Assessment (AFAs) is obtained and RPS are also considering prioritisation of LiDAR survey deliverables to accommodate programming constraints.

• Channel and structure survey – the project specific specification excludes HA09, where pre- contract surveys are progressing on-site, due to concerns regarding survey resourcing across several simultaneous CFRAM Study contracts RPS are proposing methodology amendments.

The procurement of channel and structure survey data is on the Eastern CFRAM Study’s critical path with regard to preparing flood mapping for consultation during 2013. A variety of procurement strategies have been explored and/or adopted including an OPW initiative to obtain pre-contract survey data via a national survey framework.

In relation to the Eastern CFRAM Study the pre-contract survey is limited to HA09 (the Liffey catchment).

- This type of survey carries an inherent high degree of weather risk and delays due to high water levels, poor accessibility or frozen waters may result in programme delays. It should be noted that this constraint goes beyond HA09. Given procurement delays with individual CFRAM studies and the pre-contracted survey contract there are several survey contracts of similar size and nature running concurrently and RPS

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have a genuine concern that survey data delivery and quality will jeopardise flood map delivery.

Whilst strategies at national level have been considered regarding recombining contracts to potentially attract larger survey company interests, the focus of mitigation to address concerns in survey contract for HA09 is as follows:

1. RPS have undertaken review of the pre-contract survey scope to optimise the number of required cross sections by refining the extent of AFA boundaries and modelled watercourses.

2. RPS have proposed survey work packages within the contract which seek phased delivery of priority datasets such as gauging stations or particular model reaches to accommodate modelling work programmes.

3. RPS would propose to further prioritise watercourses within certain AFAs to focus on those presenting the most significant flood risk in relation to the Floods Directive, this would allow development of flood maps and options for these watercourses to progress in accordance with consultation timescales whilst modelling of other lower priority watercourses, for the purpose of providing planning information, takes place during the consultation periods. In particular there is a proposal to fast track the development of the Camac and Poddle CFRAM assessments which would entail prioritising survey works within these high priority watercourse catchments.

4. OPW, RPS and other CFRAM consultants met to discuss survey procurement and programme risk mitigation, a number of measures have been put in place including circulation of weekly survey progress and programmes, permission to authorise small variations in survey contracts, exploring the option of transferring survey management and establishment of an overall survey programme across various contracts. These measures are currently under consideration.

There are no further additional risks and associated methodology amendments identified at present in HA09.

7.2 OPPORTUNITIES AND PROPOSED METHODOLOGY AMENDMENTS

Data Collection – Technical Note 2 (IBE0600 TN0002) details RPS’s proposed Flood Event Response Plan so that the response team members are appraised of requirements before an event occurs. The plan was available before first contract duration flooding to properties which occurred in HA09 during the Eastern CFRAM Study (24/10/11). Extensive flooding was experienced in over 50 locations and the plan was successfully enacted with several RPS team members in attendance.

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In addition RPS has reviewed the data available in the Greater Dublin Strategic Drainage Strategy (GDSDS) study which covers parts of HA10 and HA09 in the Eastern CFRAM Study area. RPS identified existing datasets which were extracted and formatted by the GDSDS team in order to inform the specification of surveys in urbanised areas with highly altered watercourses (Loughlinstown). This provided the opportunity to provide robust survey specification and save field time in identifying underground routes and culvert interconnections.

RPS has provided a quotation to OPW for fast racking the studies in the Camac and Poddle (which are two high priority watercourses within HA09) so that no regrets measures might be considered in the catchments ahead of 2015. The proposal is on the basis that the overall Eastern CFRAM Study will not be impacted and that the measures developed will be fully compliant with the CFRAM specifications. The results from the previous Greater Dublin Strategic Drainage Study for the Poddle and Camac may be exploited to assist in fast tracking the modelling and analysis.

Hydrological Analysis – Technical Note 3 (IBE0600 TN0003) details a potential opportunity to utilise RADAR rainfall data to provide a more accurate representation of the spatial and temporal hydrological inputs to the hydraulic models made possible by the availability of Met Éireann’s RADAR datasets. A demonstration of the method was provided to OPW 26/10/11 and a staged basis of service delivery accepted by OPW in their letter of 14 December 2011. The staged trial initially applies to the Dodder catchment and subject to the success of stage 1 a second stage would apply to the whole eastern study area and therefore HA09. If the RADAR trial is unsuccessful GIS elevation-based spatial-temporal interpolation techniques will be used to enhance the standard Thiessen polygons methodology to generate spatially-weighted rainfall time series as inputs to the hydrological models, refer to Sections 5.4 and 5.6.1.

There are no further additional opportunities and associated methodology amendments identified at present in HA09.

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8 REFERENCES

Reference 1: EC Directive on the Assessment and Management of Flood Risks (2007/60/EC) (2007)

Reference 2: SI 122 of 2010 European Communities (Assessment and Management of Flood Risks) Regulations, 2010

Reference 3: Office of Public Works, 2011: “National Flood Risk Assessment and Management Programme, Eastern River Basin District Catchment-based Flood Risk Assessment and Management (CFRAM) Study, Stage II Tender Documents: Project Brief”

Reference 4: Office of Public Works, 2010: “National Flood Risk Assessment and Management Programme, Catchment-based Flood Risk Assessment and Management (CFRAM) Studies, Stage I Tender Documents: Project Brief”

Reference 5: Office of Public Works, 2006: “Flood Studies Update - Work Package 2.1, Review of Flood Flow Ratings for Flood Studies Update, Final Report J2194”

Reference 6: Environmental Protection Agency, January 2005: “Flooding in the Tolka Catchment 8 January 2005”

Reference 7: Environmental Protection Agency, December 2003: “Flooding in the Dodder Catchment 2 December 2003”

Reference 8: Environmental Protection Agency, January 2005: “Flooding in the Santry Catchment 14 November 2002, 20-21 October 2002 & 28 October 2004”

Reference 9: Environmental Protection Agency, January 2005: “Selected Floods in the Griffeen Catchment”

Reference 10: Royal Haskoning, April 2005: “Dublin Coastal Flooding Protection Project (DCFPP) Final Report”

Reference 11: Dublin City Council, February 2002: “Flood 2002, Interim Assessment Report”

Reference 12: RPS MCOS, October 2003, “River Tolka Flood Study Technical Report Volume 2 River Modelling Report”

Reference 13: ESBI, October 2001, “River Liffey Flood of November 2000”

Reference 14: ESBI, November 1993, “River Liffey Flood of June 1993”

Reference 15: An Foras Forbatha Teoranta, November 1987, “Hurricane Charlie An Overview

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Activites of An Foras Forbatha”

Reference 16: Dublin Corporation, March 1966, “River Dodder Improvement Scheme - Angelsea Road Section Donnybrook to Ballsbridge”

Reference 17: ESB, February 1986, “River Liffey Flood Control and Dam Safety”

Reference 18: Dublin Corporation, November 1987, “Hurricane Charlie An Overview - Flooding in Dublin City Rivers 25/26 August 1986”

Reference 19: Dublin Corporation, December 1986, “River Dodder 1986 Flooding Report”

Reference 20: ESB, November 1987, “River Liffey Flood of 25-26 August 1986”

Reference 21: Dublin City Council, November 1965, “Flooding of Nov.1965 Dublin Area-handwritten notes”

Reference 22: Office of Public Works, 2009: “Flood Studies Update - Work Package 2.2 - Frequency Analysis”

Reference 23: Met Éireann, 2004: “Flood Studies Update - Work Package 1.2 – Estimation of Point Rainfall Frequencies”

Reference 24: Institute of Hydrology, 1994: “Report No. 124, Flood Estimation for Small Catchments”

Reference 25: Natural Environmental Research Council (NERC), 1985 “The FSR rainfall-runoff model parameter estimation equations updated”, Flood Studies Supplementary Report (FSSR) No. 16 December 1985.

Reference 26: Office of Public Works, JBA, 2010: “Flood Studies Update - Work Package 3.4, Guidance for River Basin Modelling”

Reference 27: RPS, SWRBD, 2008, “Further Characterisation Study: An Integrated Approach to Quantifying Groundwater and Surface Water Contributions of Stream Flow”

Reference 28: Bell, A. K., Higginson, N., Dawson, S., Glasgow, G., and Elsaesser, B. 2005. Understanding and managing hydrological extremes in the Lough Neagh Basin, Tullamore National Hydrology Seminar, Proceedings, 1-10.

Reference 29: Office of Public Works, 2011: “Flood Studies Update, Alpha Testing Users Guide”

Reference 30: Office of Public Works, JBA, 2009: “Flood Studies Update - Work Package 3.5 – IBIDEM (Interactive Bridge Invoking the Design Event Method)”

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APPENDIX A

HYDROMETRIC DATA STATUS TABLE

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APPENDIX B

DAILY AND HOURLY RAINFALL

DATA STATUS TABLES

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APPENDIX C

RAINFALL RADAR DATA ANALYSIS TO PROVIDE INPUT TO HYDROLOGICAL MODELS

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If the use of radar data for hydrological input is rolled out to the entire Eastern CFRAM Study area, rainfall radar data for Dublin Airport for the period 1997-2011 will be processed by HydroLogic. Preliminarily calibration of radar data on a monthly basis using ground observation data from rain gauges will be undertaken. Rainfall input for hydrological models will be generated using weighted averaging of the radar pixels above each HEP catchment area.

Daily and hourly rainfall data provided by Met Éireann and Local Authorities will be used to calibrate Dublin rainfall radar data as applied to HA09. The number of rain gauges used for calibration of radar is variable; the results calibration depends on the number of high quality rain gauges. Rain gauge data quality assessment and labelling includes several data checks including:

• detection of gaps,

• detection of physically impossible data,

• detection of constant intensities,

• values above set thresholds,

• detection of too high or too low daily sums compared to neighbouring stations.

Only periods of plausible data are taken for calibration and verification procedures.

The combination of spatial distributed rainfall intensifies from radar and accurate rainfall amounts from rain gauges will result in an improved dataset for use in hydrological modelling, both in terms of spatial resolution (1 x 1 kilometre grid) and temporal resolution (hourly data). The results of the preliminary radar calibration will be verified using independent stations (not used for calibration of radar).

Improved calibration of radar data will consist of several consecutive calibration steps on an hourly or 15 minute basis, similar to the steps described by Holleman (2007)1:

1. Calculate the parameter (RG) describing the relation between the amount of precipitation from rain gauges (G) and the corresponding radar pixels (R) for each pair of G and R:

⎛ R ⎞ RG = 1010 log⎜ ⎟ ⎝ G ⎠

2. Bias correction: the average of all available RG values is used to correct for any bias, for example calibration errors. Moreover, the calculated standard deviation is used to perform a quality control on the RG values, and thus the radar and rain gauge observations.

1 I. Holleman. (2007) Bias adjustment and long-term verification of radar-based precipitation estimates. Meteorological Applications 14:2, pp.195-203.

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3. Distance correction: correction for the height of the radar beam above earth surface and related underestimation of the precipitation intensity at that location. This correction is described as a function of the distance from the radar (r); RG and r are then fitted to a parabola.

4. Spatial correction: an inverse-distance method of the RG values is used to correct for local effects in the radar composite. This analysis yields a smooth field fitted to the data points.

Existing HydroNET tools will be used together with the SCOUT software by hydro&meteo (www.hydrometeo.de). These tools are already widely used in the Netherlands and internationally. The result is a self describing dataset in the NetCDF format; a format which is well-known and widely used in meteorology.

A phased approach to the use of radar rainfall data will be applied within the overall Eastern CFRAM Study hydrology methodology. The phasing is based on determining the accuracy and applicability by trialling it on a pilot area, then rolling it out to the entire Eastern CFRAM Study area if proven beneficial.

The Stage 1 of the Dublin radar data analysis for the Dodder catchment is complete (refer to report of Stage 1 of this analysis). The main findings of this analysis indicated that the usage of the Dublin radar data, although with variable quality, can bring a significant improvement in the estimation of the rainfall inputs when compared to the area weighted rainfall estimation (traditionally used) for the hydrologic and hydrodynamic modelling for each HEP. For hydrological modelling and estimation of the design flows in the Study area, radar-based NAM inputs will be generated (subject to the results of the first phase of trialling, using polygon shape files describing catchment areas for each individual HEP (refer to Section 5.3 and 5.4)

Since radar data is available only for the period 1997- 2011, the spatio-temporal distribution for the periods before 1997 will be estimated using the daily and sub-daily time series of the additionally available rainfall data from the rain gauges (provided by Met Éireann and the Local Authorities). From the processed and calibrated radar data (period 1997-2011) typical rainfall parameters (daily and monthly sums) will be generated for each month for the HEP catchment areas. Those sums will be scaled to relative weights using grid-based weighing techniques (inverse-distance, radial basis functions or others). The daily and the sub-daily precipitation patterns for the HEP catchment areas will then be generated by multiplying the radar patterns (relative weights) with the time recorded series for the periods before 1997 for the length of the available time series. In cases where it is impossible to generate averaged radar-based patterns, we will use standard Thiessen polygons or other interpolation techniques (such as IDW) to generated spatially-weighted time series rainfall inputs for the hydrological models. This will result in the production of rainfall input files for each NAM HEP for the entire length of rainfall time series data provided.

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APPENDIX D

Hydrology Method Process Chart – Used Datasets Table

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IBE0600Rp0008 RevF02 Eastern CFRAM Study HA09 Inception Report – FINAL Box Number (Figure 2.2) ShapefileGIS of River Network DTM, Mapping, Aerial Imagery FSU Ungauged Catchment Descriptors PointGIS File FSU Gauged Catchment Descriptors PointGIS File FSU Ungauged and Gauged Catchment Outlines GIS Polygon Layer Rainfall Radar Data (Ii approved) Daily and Hourly Rainfall Station Data Met Éireann Evaporation Data GSI Soil and Bedrock /Aquifer GIS Layers Corine 2006 Landuse GIS Layer Hydrometric Data 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

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APPENDIX E

HEP and Catchment Diagrams

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