South Western CFRAM Study
Hydrology Report, Unit of Management 19 June 2016
The Office of Public Works
South Western CFRAM Study
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The Office of Public Works
Trim Co. Meath
Mott MacDonald, 5 Eastgate Avenue, Eastgate, Little Island, Cork, Ireland
T +353 (0)21 4809 800 F +353 (0)21 4809 801 W www.mottmac.com
South Western CFRAM Study Hydrology Report,Unit of Management 19
Issue and revision record
Revision Date Originator Checker Approver Description Standard A September 2013 M Piggott R Gamble R Gamble Draft
B February 2014 M Piggott R Gamble R Gamble Draft Final
C June 2016 M Piggott C Hetmank C Hetmank Final
This document is issued for the party which commissioned it and We accept no responsibility for the consequences of this for specific purposes connected with the above-captioned project document being relied upon by any other party, or being used only. It should not be relied upon by any other party or used for for any other purpose, or containing any error or omission any other purpose. which is due to an error or omission in data supplied to us by other parties.
This document contains confidential information and proprietary intellectual property. It should not be shown to other parties without consent from us and from the party which commissioned it..
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Contents
Chapter Title Page
Executive Summary i
1 Introduction 1 1.1 Context of the CFRAM Study ______1 1.2 SW CFRAM Study Process ______1 1.3 Report Structure ______2 1.4 Flood Probabilities ______3
2 Description of the Study Area 5 2.1 Extent ______5 2.2 Rivers ______7 2.3 Coastal Features ______7 2.4 Topography ______8 2.5 Rainfall ______8 2.6 Geology ______12 2.7 Land Use ______12
3 Data Collection and Review 13 3.1 Available Data ______13 3.2 River Gauge Data ______13 3.3 Rainfall Data ______16 3.4 Coastal Data ______19
4 Historical Flood Review 21 4.1 Historical Flood Events ______21 4.2 Historical Flood Mechanisms ______24 4.3 Historical Flood Frequency Estimates ______25
5 Design Flows 28 5.1 Overview ______28 5.2 Definition of Sub-Catchments ______28 5.3 Flood Frequency Analysis ______31 5.4 Hydrograph Generation ______36 5.5 Coastal Conditions ______39
6 Calibration, Sensitivity and Uncertainty 42 6.1 Flow Determination for Model Calibration ______42 6.2 Uncertainty and Sensitivity Testing______48
7 Summary of Design Hydrology 50
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8 Considerations for Hydrological and Hydraulic Model Integration 53 8.1 Inflows ______53 8.2 Downstream Conditions ______54
9 Hydrogeomorphology 55 9.1 Approach ______55 9.2 Assessment ______55 9.3 Impact on Flood Risk ______58
10 Joint Probability 59 10.1 Overview ______59 10.2 Fluvial-Fluvial Dependence ______59 10.3 Fluvial-Coastal Dependence ______61
11 Future Scenarios 62 11.1 Potential Climate Changes ______62 11.2 Potential Catchment Changes ______62 11.3 Design Future Scenario Conditions ______64
12 Conclusions, Key Findings and Recommendations 66 12.1 Conclusions and Key Findings ______66 12.2 Recommendations ______68
Glossary 69
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Executive Summary
The Office of Public Works (OPW) is undertaking six catchment-based flood risk assessment and management (CFRAM) studies to identify and map areas across Ireland which are at existing and potential future risk of flooding. Mott MacDonald Ireland Ltd. has been appointed by the OPW to assess flood risk and develop flood risk management options in the South Western River Basin District. This hydrology report is one of a series of reports being produced as part of the South Western Catchment Flood Risk Assessment and Management Study (SW CFRAM Study). This report details the assessment of the hydrological conditions at the following locations within Unit of Management 19: Ballingeary Castlemartyr Killeagh The downstream reaches of the River Womanagh
This report does not review or update flows for the wider Lee catchment which have been assessed separately under the River Lee Pilot CFRAM Study.
A review and analysis of historical flood events, hydrometric data and hydrogeomorphological processes has highlighted flooding issues to urban areas and nationally important infrastructure from the River Womanagh, Upper Lee, Bunsheelin River and a number of smaller tributaries. The Flood Studies Update methodologies have been used to determine the current design peak flows for eight specified flood probabilities. Rainfall-runoff modelling has been used to derive the critical hydrograph at Ballingeary that results in flooding to the town. The FSU UPO-ERR Gamma curve has been applied to derive the characteristic flood hydrographs across the Womanagh catchments. Corresponding coastal conditions have been developed for the design fluvial events. Calibration events were identified in Castlemartyr, Killeagh, and Ballingeary where there was sufficient historical flood data.
Potential future catchment changes relevant to the Upper Lee and Womanagh catchment have been assessed including changes in urban development, land use and hydrology related to global climate change. Two future scenarios have been developed from this analysis, a Mid Range Future Scenario and High End Future Scenario, which have been used to develop potential future flows and extreme sea levels.
The resultant design flood hydrographs and coastal conditions will be used as input to the hydraulic models. The knowledge of the hydrological processes and the historical flooding issues across Unit of Management 19 established in this report will support the development of sustainable and appropriate flood risk management options in those areas at greatest flood risk.
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1 Introduction
1.1 Context of the CFRAM Study
Flooding is a natural process that occurs throughout Ireland as a result of extreme rainfall, river flows, storm surges, waves, and high groundwater. Flooding can become an issue where the flood waters interact with people, property, farmland and protected habitats.
Flood risk in Ireland has historically been addressed through the use of structural or engineered solutions (arterial drainage schemes and / or flood relief schemes). In line with internationally changing perspectives, the Government adopted a new policy in 2004 that shifted the emphasis in addressing flood risk towards: A catchment-based context for managing risk; More pro-active flood hazard and risk assessment and management, with a view to avoiding or minimising future increases in risk, such as that which might arise from development in floodplains; Increased use of non-structural and flood impact mitigation measures.
A further influence on the management of flood risk in Ireland is the 'Floods' Directive [2007/60/EC]. The aim of this Directive is to reduce the adverse consequences of flooding on human health, the environment, cultural heritage and economic activity.
The Office of Public Works (OPW) is the lead agency in implementing flood management policy in Ireland. The OPW have commissioned a number of Catchment Flood Risk Assessment and Management Studies in order to assess and develop Flood Risk Management Plans (FRMPs) to manage the existing flood risk and also assess the potential for significant increases in this risk due to climate change, ongoing development and other pressures that may arise in the future.
Mott MacDonald Ireland Ltd. has been appointed by the OPW to undertake the Catchment Flood Risk Assessment and Management Study (CFRAM Study) for the South Western River Basin District, henceforth referred to as the SW CFRAM Study. Under the project, Mott MacDonald will produce FRMPs which will set out recommendations for the management of existing flood risk in the Study Area.
1.2 SW CFRAM Study Process
The overarching aims of the SW CFRAM Study are as follows:
Identify and map the existing and potential future flood hazard; Assess and map the existing and potential future flood risk; and, Identify viable structural and non-structural options and measures for the effective and sustainable management of flood risk in the South Western River Basin District.
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In order to achieve the overarching aims, the study is being undertaken in the following stages: Data collection; Hydrological analysis; Hydraulic analysis; Development of flood maps; Strategic Environmental Assessment and a Habitats Directive Appropriate Assessment; Flood risk assessment of people, economy and environment; Development and assessment of flood risk mitigation options; and, Development of the Flood Risk Management Plan (FRMP).
The resultant FRMP will set out recommendations for the management of existing flood risk and the potential for significant increases in this risk due to climate change, ongoing development and other pressures that may arise in the future.
The South Western River Basin District is split into five Units of Management (UoM). These Units follow watershed catchment boundaries and do not relate to political boundaries. The Units are as follows; The Blackwater catchment (UoM18) The Lee / Cork Harbour Catchment (UoM19) The Bandon / Skibbereen Catchment (UoM20) The Dunmanus / Bantry / Kenmare Bay Catchment (UoM21) The Laune / Maine / Dingle Bay Catchment (UoM22)
1.3 Report Structure
This report aims to assess the hydrological conditions at Ballingeary, Castlemartyr, Killeagh and the lower Womanagh. The hydrological analysis will derive design peak flows, levels and hydrographs to be used in subsequent hydraulic modelling and mapping of key areas at risk.
Table 1.1 outlines the report structure and scope of work with a description of the key contents.
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Table 1.1: Report Structure Chapter Key Contents of Chapter 1. Introduction Context of the Study The SW CFRAM process and aims Scope of Work Flood Probabilities 2. Description of Study Area Description of study area Description of hydrological characteristics of study area 3. Data Collection and Review Overview of data used in the hydrological analysis Review and quality assessment of river level and flow data Review and quality assessment of rainfall data Review and quality assessment of coastal data 4. Historical Flood Review Review of historical flood events Review of significant sources, pathways and receptors of flooding Estimation of flood probability for key historical events 5. Design Flows Definition of sub-catchments Derivation of the index flood, design peak flows and flow hydrographs Derivation of extreme sea levels and tidal curves 6. Calibration, Sensitivity and Uncertainty Review of historical data and selection of calibration events Derivation of calibration conditions Hydrological sensitivity and uncertainty in design hydrology 7. Summary of Design Hydrology Principal outputs and findings of design hydrology Preliminary design flows and hydrographs for hydraulic modelling 8. Consideration for Hydrological and Full methodological approach to integrate hydrological Hydraulic Model Integration outputs and hydraulic models 9. Hydrogeomorphology Assessment of existing hydrogeomorphological processes Consideration of flood risk impacts 10. Joint Probability Joint probability of fluvial events Joint probability of coastal events 11. Future Scenarios Potential impacts of climate change to rainfall, river flows, sea level and land movement Potential catchment changes to land use and urbanisation Derivation of hydrology under future scenarios 12. Conclusions, Key Findings and Conclusions and key findings from the hydrological analysis Recommendations and assessment Summary of Design Existing and Future Hydrology Recommendations for hydraulic modelling and the FRMP Recommendations for future improvements in the hydrological analysis
1.4 Flood Probabilities
The SW CFRAM Study refers to flood probabilities in terms of annual exceedance probability in preference to the use of “return periods” as used in previous reports. The probability or chance of a flood event occurring in any given year can be a useful tool to better understand the rarity of specific magnitude events for flood risk management. Due to popular descriptors of floods involving terms like the “1 in 100 year flood” there can be a public misunderstanding that a location will be safe from a repeat event of the same
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magnitude, extent and volume for the duration of the term (100 years in the above example). In reality, flood events of a similar or greater magnitude can occur again at any time.
Annual Exceedance Probability, henceforth referred to as AEP, is a term used throughout this report and the wider CFRAM studies to refer to the rarity of a flood event. The probability of a flood relates to the likelihood of an event of that size or larger occurring within any one year period. For example, a one in hundred year flood has a one chance in a hundred of occurring in any given year; 1:100 odds of occurring in any given year; or a 1% likelihood of occurring. This is described as a 1% annual exceedance probability (AEP) flood event.
Table 1.2 converts the ‘return periods’ to %AEP for key flood events as a reference to previous studies.
Table 1.2: Flood Probabilities % Annual Exceedance Probability Odds of a Flood Event in Any Given Chance of a Flood Event in Any (%AEP) Year Given Year or Previous ‘Return Period’ 50% 1:2 1 in 2 20% 1:5 1 in 5 10% 1:10 1 in 10 5% 1:20 1 in 20 2% 1:50 1 in 50 1% 1:100 1 in 100 0.5% 1:200 1 in 200 0.1% 1:1000 1 in 1000
The hydrological analysis uses a number of other acronyms and technical terminology which are defined in the glossary of this report.
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2 Description of the Study Area
2.1 Extent
The South Western River Basin District covers an area of approximately 11,160 km2. The Study Area includes most of County Cork, large parts of Counties Kerry and Waterford, along with small parts of the counties of Tipperary and Limerick. The Study Area contains over 1,800 km of coastline along the Atlantic Ocean and the Celtic Sea. There are five Units of Management within the South Western River Basin District, which are listed below: The Blackwater catchment (UoM18) The Lee / Cork Harbour Catchment (UoM19) The Bandon / Skibbereen Catchment (UoM20) The Dunmanus / Bantry / Kenmare Bay Catchment (UoM21) The Laune / Maine / Dingle Bay Catchment (UoM22)
There are three Areas for Further Assessment (AFAs) assessed as part of the SW CFRAM Study within UoM 19, as listed in Table 2.1. Killeagh and Castlemartyr lie outside the River Lee catchment and hence were not considered under the River Lee Pilot CFRAM Study1. The third AFA, Ballingeary, is within the Upper Lee catchment and was assessed as part of the River Lee Pilot CFRAM Study but not to the AFA level of detail. Therefore, this report undertakes more detailed hydrological analysis for Ballingeary to assess it as an AFA.
Table 2.1: Areas for Further Assessment Contributing Catchment Fluvial Coastal Area Name Unique ID Flood Risk Flood Risk County Easting Northing (km2) Killeagh 190274 Yes No Cork 200750 75750 30 Castlemartyr 190277 Yes No Cork 196250 73250 29 Ballingeary 195499 Yes No Cork 115090 67135 54
All grid references are to Irish National Grid (ING) and levels are to Ordnance Datum Malin Head (mODM).
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Map 2.1: Unit of Management 19 Study Area
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2.2 Rivers
For reporting purposes, the UoM19 study areas considered as part of this report can be split into two major sub-catchments; the Womanagh and Upper Lee/ Ballingeary as shown in Map 2.1.
Womanagh Catchment
The Womanagh River stretches from its source at Carrigour to its tidal outfall at Pilmore into Youghal Bay. The Womanagh is relatively flat with a typical gradient of 1 in 900 in the upper reaches, reducing to over 1 in 20,000 in the tidal reaches. The Kiltha River flows from Springfields/Mogeely southwards through Castlemartyr to join the Womanagh near Ladysbridge. Within Castlemartyr, a spring at Little Island diverts water from the Kiltha via the Castle, through the lake to re-join downstream of the town. The Dower River and Ladysbridge Stream join the Womanagh before the Dissour River. The Dower River in particular is heavily dominated by karst and flows through swallow holes, creating a dry valley in its upper reaches. The Dissour River flows from Kilcronatmountain southwards through Glenane Beg Ravine before flowing through Killeagh town and joining the River Womanagh at Finisk Old Bridge.
Ballingeary
The Upper Lee flows from its source near Rosslougha in an easterly direction to the south of Ballingeary at Inchinossig Bridge and continues towards Cork. The Bunsheelin River flows through Ballingeary from the North to join the upper River Lee downstream of Inchinossig Bridge. The River Lee then flows in an easterly direction into Lough Allua and downstream to Inchgeelagh. The Bunsheelin River has a steep gradient of 1 in 35, reducing to 1 in 130 before entering the flat water body of Lough Allua.
2.3 Coastal Features
The Womanagh River can be considered tidal downstream of Finisk Old Bridge, some 10km inland. The tidal channel is embanked above the low-lying tidal floodplain downstream of Finisk Old Bridge limiting the width of the channel to 30m. Once these embankments are overtopped, it would be difficult for flood waters to return to the channel as the floodplain is typically lower than the river. Downstream of Crompaun Bridge, the tidal channel widens to a more estuarine feature over 300m wide with several low-flow loop channels until its tidal outfall at Pilmore. There are large intertidal flats in the estuarine area which are inundated on most tides. The spit features at the tidal outfall protect inland areas from extreme wave action. The Ireland Coastal Water level and Wave Study 2013 (ICWWS) did not identify any areas vulnerable to wave overtopping. Therefore, flooding arising from wave overtopping has not been considered further.
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2.4 Topography
Map 2.2 displays the variation in elevation and topography in the Areas for Further Assessment in UoM19.
The River Womanagh catchment ranges from less than 1mODM near Gortnagark Castle, up to 238mODM in the upper reaches of the Kiltha and Dissour River. The areas of highest relief are associated with the more resistant underlying geology to the north and south of the Womanagh Valley as described in Section 2.6 below. The low-lying tidal floodplain downstream of Finisk is typically 600m wide, constrained by the resistant geology either side. The floodplain narrows to 350m at Crompaun Bridge as the valley side spurs limit the volume available on the floodplain. Downstream, the floodplain widens as the Gortavadden Channel joins from the west and Ballymadog Channel from the north. There is a low pass at Ballykinealy which may be vulnerable to extreme storm surges with predicted climatic change.
The relief in Ballingeary is much higher. The Bunsheelin catchment ranges from 85mODM at Lough Allua to over 530mODM in its headwaters. The upper reaches are steep (1 in 35) and the valley is constrained by the relatively mountainous topography. The steep-sided valley results in a fast-responding catchment, leaving some properties at the bottom of these slopes vulnerable to surface water run-off as well as flash flooding from the river. The floodplain widens to 400m as the Bunsheelin flattens out to join the Upper Lee and Lough Allua. The flatter topography and presence of Lough Allua downstream can prolong flooding in the lower reaches depending on the Lough level prior to the event.
2.5 Rainfall
Map 2.3 shows the variation in Standard Average Annual Rainfall across UoM19. Rainfall tends to be greater in the west and decreases towards the east. This corresponds with the dominant wind direction in the South West where storms tend to track west to east.
Ballingeary has high annual rainfall, over 2000mm, because the regular westerly storms deposit much of their rainfall over the higher relief of the Shehy Mountains which drains to Ballingeary and Lough Allua. Conversely, the Womanagh catchment has relatively low rainfall, less than 1200mm, as it has much lower topography and is located within a rain shadow of the western mountains. Furthermore, the permeable karstic geology reduces the amount of rainfall reaching the rivers in this catchment.
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Map 2.2: Topography
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Map 2.3: Standard Average Annual Rainfall
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Map 2.4: Geology
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2.6 Geology
Map 2.4 provides the underlying geology of UoM19. The Lee catchment is predominantly underlain by Old Devonian Sandstones which are relatively impermeable and create steep relief in the mountainous areas around Ballingeary. This leads to flashy response to rainfall in the upper catchments of Bunsheelin and the Upper Lee. The Womanagh valley and lower reaches of its tributaries are underlain by permeable Dinatian Limestone forming part of a regionally important aquifer. The high permeability of underlying soils in this area may reduce flows when the ground is unsaturated. However, flooding could be exacerbated when the underlying aquifer is saturated prior to a flood event.
2.7 Land Use
The Bunsheelin and wider Lee catchment is predominately rural in its upper reaches, with land assigned to peat bog, pastoral practices or forestry. The forest tends to be coniferous but this makes up less than 6% of the area around Ballingeary. The lack of dense vegetation across the majority of the catchment tends to exacerbate runoff over the steep sided slopes, creating a flashy response to rainfall downstream.
The Womanagh catchment is dominated by pastoral farming, although the lower reaches of the Kiltha River are heavily wooded, accounting for 15% of land cover in this catchment. The urban areas of Castlemartyr and Killeagh have a combined population of less than 2000 and account for less than 1% of land cover.
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3 Data Collection and Review
3.1 Available Data
A range of different data sources have been used to undertake the hydrological data analysis for Unit of Management 19. The use of local hydrometric data can greatly improve and validate flood flows for historic events and design flood events. The following sources of data have been reviewed in Unit of Management 19 (Table 3.1).
Table 3.1: Summary of Available Data Type Details Owner Date River Flows 15 minute interval data series at 3 gauges with flow The OPW Various up to 2012 converted from water level EPA River Levels 15 minute interval data series at 3 gauges The OPW Various up to 2012 EPA Rainfall Gauges Daily rainfall values at 7 gauges Met Eireann Various up to 2012 Hourly rainfall series at Cork Airport and Roches Point Met Eireann 1962-2012 15 minute rainfall series Dunmanway The OPW 2011-2012 Extreme sea Irish Coastal Protection Strategy Study Total tide +surge The OPW Calculated in 2012 level design levels Sea Level Sea level at 10 minute intervals at Ballycotton Gauge The OPW 2007 - 2012
A full data register can be found in Appendix A.
3.2 River Gauge Data
The locations of river gauges in the catchment with available water level and flow data are shown in Map 3.1.
The existing hydrometric data has been assessed for the following common issues: Anomalous spike or dips in water level and/or flow from the continuous data records; Capping of water level and/or flow, particularly for extreme events at fluvial gauges where extreme flows may be out-of-range; Trends in water level or flow over time that might be caused by systematic error of gauging equipment or erosion/sedimentation; Sudden shifts in level of the gauging datum; Comparison of AMAX flows and levels from digital gauged data with manually extracted AMAX series; Anomalously high or low AMAX flood event within the AMAX series at each gauge; Consistency of concurrent high flows downstream for AMAX events; Length of data record to enable hydrological analysis; and, Any significant data gaps.
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Station 19003: The Castlemartyr gauge on the Kiltha River was found to be unsuitable for further analysis because there was found to be large scatter in the spot gaugings provided and no concurrent cross-section to develop a rating curve from the model. Therefore, the Castlematryr gauge was not deemed suitable for flow estimation. Furthermore, the water level record does not cover most recent events which caused flooding in Castlemartyr.
Station 19019: The Dower gauge has less than 2 years' record and displays significant periods of missing data, trending and capping of peak flows. The Dower gauge is also located at the spring outfall of a karstic system, so the gauge records are heavily influenced by groundwater and subterranean flows, making surface water flood estimation difficult. The poor data quality at Dower gauge has resulted in the site being rejected for statistical analysis.
Station 19039, 19043, 19002, 19025 and 19029: These gauges are located in Ballingeary, Inchgeelagh, upstream of Castlemartyr and upstream of Killeagh. However, they are only staff gauges with limited low flow spot gaugings available. It was not possible to undertake statistical analysis because there was no continuous record of flood peaks. Therefore, these gauges have been rejected from further hydrological analysis.
Station 19020: The Ballyedmond gauge on the Owencurra provides over 30 years of flow and level data which is generally classed to be consistent without anomalies since 1996, and captures the maximum peak flows before 1996. The existing OPW rating curve is consistent and convergent for high flows, indicating that the rating curve extension for extreme flows is applicable and the resultant AMAX series is reliable. Therefore, the existing OPW rating curve has been adopted and the Ballyedmond gauge is applicable to inform flows in nearby catchments for the same storm event.
Appendix A contains a list of the selected gauges for the hydrological analysis.
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Map 3.1: Selected Hydrometric Data
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3.3 Rainfall Data
Available meteorological data from rain gauges and synoptic stations in and near to the catchment are shown in Map 3.2.
The existing meteorological data has been assessed for the following common issues:
Spatial distribution of intensity loggers and respective storage gauges (event based); Identification of gaps or erroneous data which have been cross-referenced with the Met Eireann climate stations to assess if significant events have been omitted; Identification of shifts in rainfall records using temporal and cumulative plots; and, Analysis of cumulative rainfall for key historic events.
The rain gauges have been used for rainfall-runoff modelling at Ballingeary and to inform the calibration hydrographs in the Womanagh catchment. River gauge data from hydrologically similar catchments rather than rainfall data has been used to derive the design peak flows in accordance with the latest FSU approach.
The rain gauge at Ballingeary (3004) has been selected for the analysis of typical rainfall patterns and phasing for the Ballingeary AFA. The Met Eireann record matched the records provided at the local Flood Committee’s workshop for the 2009 event. Therefore the full Met Eireann record has been applied in the CFRAM study. The Ballingeary rain gauge has over 50 years of continuous daily rainfall data. The highest recorded rainfall within a 24 hour period was 139mm on 11th October 1996 but the highest monthly rainfall was in November 2009. There were two short periods of missing data in 1950 and 1983, but otherwise the rainfall record was deemed to be consistent without shifts over time. There was no trend in the average annual rainfall over time, although the maximum rainfall recorded has increased over the past two decades indicating a trend to more intense storms.
Detailed hourly rainfall is limited to Cork Airport (955) and Roches Point (952) only. However, there is good spatial coverage of daily rainfall gauges. Additionally, the Dunmanway gauge (4902) provides more detailed rainfall data at 15 minute intervals since July 2011 as provided by the OPW in November 2012. This rainfall data can be used in combination with the daily gauge at Ballingeary to supplement the analysis of historical flood events.
There are no active rainfall gauges in Castlemartyr and Killeagh for the recent flooding events. However, gauges 4904, 5004 and 4404 were active for the 2009 event. These gauges were deemed to have reliable total rainfall for this event and were used to transfer the rainfall profile from the hourly gauges in Cork. Similarly, gauge 6204 was used to transfer the November 2009 rainfall to the Owencurra catchment to inform the calibration of the rainfall-runoff modelling at Ballyedmond river gauge (19020).
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Map 3.2: Rainfall Data
Soucre: Analysis as part of this study combined with the M5_2day rainfall contonours from the River Lee Pilto CFRAMs Hydrology Report ( Halcrow, 2009)
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3.4 Coastal Data
Map 3.3 shows the extreme coastal water level points and locations of other available coastal data.
The Irish Coastal Protection Strategy Study (ICPSS) data has been approved by OPW for use directly as the coastal boundaries for the South Western CFRAM models. The ICPSS levels will be used to define the magnitude of the tidal events in Youghal Bay, including the tidal outfall of the River Womanagh. The Irish Coastal Water Level and Wave Study (ICWWS) identified locations in Cork Harbour as vulnerable to wave overtopping. The assessment of coastal flood risk in Cork Harbour is part of the Lee CFRAM Study.
Sea level data is available at Ballycotton gauge since 2007. The short record (less than 4 years) means Ballycotton gauge was unsuitable for statistical analysis. The data record was checked for erroneous or poor quality data such as shifts in the datum, anomalous spikes and capping. There was minor variation in the peak tide level and low tide levels, probably as a result of the gauging equipment and variable atmospheric influences. The oscillation was within a 0.1 m tolerance and the data series was deemed fit for the purpose of informing coastal conditions for historical flood events since 2007.
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Map 3.3: Coastal Data
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4 Historical Flood Review
4.1 Historical Flood Events
Table 4.1 summarises the source, extent and impact of flooding for the historic events identified where sufficient evidence was available. Historic flood events in the Womanagh catchment and Ballingeary were identified from the floods database (www.floods.ie), previous reports, and interviews with Local Authority personnel and residents during the Flood Risk Review. There were limited details available for historic flood events as detailed records of impacts for events more than 20 years ago were scarce. Events in the wider Lee catchment have been assessed as part of the separate Pilot CFRAM Study and therefore have not been included here.
Flood Event of 2nd November 2011
Flooding downstream of Inchingossig Bridge due to a period of prolonged rainfall, particularly over an 18 hour period in the Upper Lee Catchment. Substantial areas of land were flooded, almost flooding local roads. No property was damaged, but grazing land was inundated.
Flood Event of 15th January 2011
Flooding affected the areas of Inchigeelagh and Ballingeary on this date and was due to overtopping on the River Lee. OPW flood reports and local engineers anecdotal reports indicate that Ballingeary suffered damage to two commercial and one residential building. Within one of the commercial buildings (Butchers), flood waters rose to a depth of 0.125m and the main road was temporarily closed.
Inchigeelagh was flooded to the north of the River Lee by up to 0.15m in both the residential and commercial buildings that were flooded. The road from the bridge to the town centre was closed for several hours.
Flood Event of 19th November 2009
The flooding of November 2009 was attributed to the heavy rainfall that fell in the preceding days and particularly due to torrential rainfall that fell overnight in the Upper Lee Catchment. Therefore, the catchment was saturated and levels in Lough Allua were already elevated before the 19th November 2009.
Ballingeary experienced flash flooding with depths of up to 1.2 metres. Flooding occurred at 17:30 due to overtopping on the Bunsheelin River at the eastern end of the village. Overall, 19 residential properties were affected, plus the local school and six commercial properties. A 340m length of the R584 was also known to be flooded. Residential and commercial losses were estimated at €300,000 and €750,000 respectively (Meitheal Forbartha na Gaeltachta, 2009)2.
At Castlemartyr, flood levels rose to a depth of 0.25m as flood waters rose out-of-bank on the River Kiltha, the R632 road was flooded and 3 residential properties were affected. Killeagh also saw flooding with a maximum depth of 0.5m observed.
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Table 4.1: Key Historical Flood Events Reported Duration of Flooding Date Flooding Mechanisms Areas Affected AFA Properties Flooded (Hours) 06/08/1986 River flooding along the Lee, Sullane Ballymakerry; Macroom;Cork City; Ballincollig None within in AFAs 24 hours and Laney 04/02/2004 Fluvial flooding due to overtopping on Ballingeary: R584, Casadh Na Spride Park , An At least 1residential property ~ 20 hours the Bunsheelin River as it meets the Grianán 27/10/2004 At least 1residential property ~ 20 hours River Lee, exacerbated by high Lough 07/01/2005 levels 8 residential properties flooded ~ 20 hours 19/11/2009 Fluvial flooding due to overtopping on Ballingeary: Ardán Seamus O’Shea 19 residential,6 commercial and 1 school Estimated to be over 20 hours ( 58 the Bunsheelin River as it meets the Castlemartyr: Mogeeley Road 3 residential and roads hour storm) River Lee, exacerbated by high Lough Estimated to be less than12 hours levels Killeagh:Main Street Roads only Wider Lee Catchment Estimated to be less than 12 Fluvial flooding due to overtopping on hours the River Kiltha 15/01/2011 Flash flooding along Bunsheelin River Ballingeary: 1 residential , 2 commercial 18 hours exacerbated by raised Lough levels from preceding events. 02/11/2011 Flooding due to raised Lough levels Ballingeary: Fields flooded and local road nearly flooded 18 Hours from preceding events.
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Flood Events on 7th January 2005, 27th October 2004 and 4th February 2004
Minutes from Parliamentary debates and council meeting minutes indicated flooding issues from Lough Allua had been previously discussed in 19643 and 20054. Subsequently Cork County Council identified recurring flooding in Ballingeary along the R584 on the dates above. Rainfall of 65mm and 69mm within 20 hours combined with raised Lough levels downstream is reported to have caused flooding to properties along the R584 on each occasion. Figure 4.1 presents the rainfall profiles for these events transferred from Cork Airport to meet the total rainfall recorded at Ballingeary VOC SCH gauge.
Figure 4.1: Historic Rainfall Profiles for Ballingeary 9
8
7
6
5 04/02/2004 27/10/2004 4 07/01/2005 Rainfall Rainfall (mm/hour) 19/11/2009
3
2
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 Hours
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Flood Event of 6th August 1986 The flood event of August 1986 affected the South West of Ireland most severely and was attributed to a prolonged rainfall event lasting 22 hours. The flooding was widespread throughout the Lee Catchment, affecting the Upper Lee and areas further downstream, such as Macroom, Sullane, Laney Ballincollig and areas of Carrigrohane. Major lakes and rivers reached their maximum level recorded and flooding upstream of the Carrigadrohid Reservoir at Ballvourney caused extensive structural damage to three bridges, almost demolishing one at Pol na Bro. At Macroom it was believed to be the most severe flooding that has ever been encountered at the time and a previously unused secondary channel was filled and its course permanently changed by the flood torrents. The flood flow is estimated at 300m3/s and at Carrigadrohid Dam the highest ever inflow was recorded.5 However, there are no reliable records of flooding at the Ballingeary, Castlemartyr or Killeagh for this event.
Other Events
A flood event on 7th January 2005 was identified by OPW’s online historic floods database (www.floodmaps.ie). However, there was insufficient reliable historical evidence regarding this flood event, after review of the available reports and online sources, to identify the further details of the causes or impacts. Comments by Cork County Council in the November 2011 flood report indicates that there are known flooding issues near Inchigossig Bridge “every year”. Extreme flood events also occurred across the rest of River Lee catchment in August 1986, November 2000, November 2002, December 2006, January 2010, June 2012 as well as March and July 2013. Details of the flood mechanisms and extents for these events can be found in the separate River Lee Pilot CFRAM Study. However, there are no records of flooding available at Ballingeary, Castlemartyr or Killeagh for the aforementioned events.
4.2 Historical Flood Mechanisms
Following the review of the historic reports and other data, the key flood mechanisms identified in UoM 19 include: Fluvial or river flooding: Fluvial flooding can occur when the capacity of the river channel is exceeded due to excess flow from heavy rainfall or releases from reservoirs upstream. Flood waters typically overtop river banks at low sections or where water is constricted by bridges or culverts forcing water levels to rise upstream and flood surrounding areas. Most of the flooding reported in UoM 19 is attributed to fluvial flooding mechanisms. Pluvial or surface water flooding: Pluvial flooding can occur when overland flow from intense rainfall or prolonged heavy rainfall is unable to enter the urban drainage network or river channel either because they are already full or there is a blockage. Pluvial flooding is exacerbated by the increase of impermeable areas (such as concrete or tarmac) associated with urbanisation which increases the amount of overland flow. The most recent flooding in Ballingeary was partly attributed to pluvial
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flooding. It should be noted that the study of pluvial flooding is not included in the scope of the CFRAM Study.
In addition to the mechanisms listed above, flooding in Ireland can also occur from the following: Groundwater flooding: Groundwater flooding can occur when waters levels rise above the ground to flood low-lying fields and property basements, typically when the catchment is saturated. The onset of flooding is very slow and therefore hazard to people is limited. The River Womanagh catchment is likely to be susceptible to this form of flooding as it is underlain by highly permeable karstic systems. However, there are no records of groundwater flooding at Ballingeary or in the River Womanagh catchment, and groundwater flooding has been discounted from further analysis. It should be noted that the study of groundwater flooding is not included in the scope of the CFRAM Study. Coastal or tidal flooding: Extreme sea levels, waves and storm surges overtop coastal defences and river banks in tidally influenced reaches, particularly when combined with high river flows for tidal rivers. The risk to people can be very high from this form of flooding as the flood waters can be fast-flowing water. However, there are no records of this flooding mechanism in the River Womanagh catchment and as Ballingeary is remote from the sea, coastal flooding has been discounted from further analysis.
Based on the historical flood evidence, the key mechanisms for each of the AFAs are as follows: Ballingeary and Inchigeelagh: Flooding typically occurs due to the overtopping of river banks along the River Lee and Bunsheelin River because the excess flows are unable to discharge into Lough Allua when water levels are raised by water from previous events. Ballingeary is also identified as at risk from pluvial flooding during intense rainfall events due to the limited capacity of the urban drainage network. Castlemartyr: Flooding typically occurs due to the overtopping of river banks along the Kiltha River at Mogeely Road as flow through Castlemartyr Bridge is constricted, causing water levels to rise upstream and flood the surrounding area. Killeagh: Flooding typically occurs due to the overtopping of the banks along River Dissour at Church View as flow through the bridges downstream is constricted, causing water levels to rise upstream and flood Church View.
4.3 Historical Flood Frequency Estimates
An estimate has been made of the frequency for the historical flood events where there were recorded river flows for the AFAs in UoM19. The recorded peak flow at the various gauges was compared to their annual maximum series, and the relative frequency of each event was derived using the Gringorten formula: i 0.44 Fi n 0.12
Where i is the relative rank in the annual maximum flow series (AMAX) and n is the number of values in the AMAX series. The Gringorten plotting position is the most appropriate plotting formula when considering the EV1 and GLO distributions. The Gringorten estimate was then reviewed against the design flows detailed in Chapter 5 of this report to establish the final %AEP estimate (Table 4.2).
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The peak flood flows in Ballingeary were derived from the calibrated FSSR rainfall-runoff model as discussed in Chapter 6 and 7. The %AEP estimates for the Ballingeary were derived from the recorded rainfall and Met Eireann’s depth duration frequency model as the best fit to the relatively frequency of historic flooding in Table 4.1. For instance, the events in 2004 and 2005 have an estimated AEP of 20% which is consistent with the observed flooding in the past 5 years.
The relative flood frequency was not transferred from the nearest gauge (19014 Dromcarra) because it is located downstream of the Lough which attenuates flows significantly hence is not necessarily representative of the more extreme peak flows upstream of the Lough.
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Table 4.2: Estimation of Flood Frequency for Historical Flood Events with Records of Flooding Nearest Gauging Station Historical Flood Event Estimated Peak Flow AFA/MPW Station No. Location Date (m3/s) Rank AEP (%) Comments Ballingeary/River Lee-Lough 3004 Ballingeary VOC 04/02/2004 76 2 20% DDF used to estimate event rarity and Allua SCH calibrated FSSR approach used to derive 27/10/2004 61 5 20% peakflows 07/01/2005 66 3 20% 19/11/2009 138 1 1% 15/01/2011 65 4 20% Castlemartyr 19020 Ballyedmond 19/11/2009 12** 1 15% Large catchment wide event with 29 hours of Killeagh Owencurra 11** rainfall recorded at Cork Airport. Womanagh River 44** ** Ballyedmond gauge has been used to determine the %AEP. The flow estimate was subsequently derived from the design flood growth curve at Castlemartyr, Killeagh and Womanagh reaches respectively.
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5 Design Flows
5.1 Overview
The hydrological approach draws on the data review described in Chapters 3 and 4 of this report and the latest Flood Studies Update (FSU) guidance. The hydrological analysis to derive design fluvial hydrographs for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1% AEP has been undertaken as follows: Define the sub-catchments and locations at which to calculate design flows (Section 5.2); Estimate the index flood flow for the 50% AEP flood (Section 5.3); Estimate the flood growth curve to derive more extreme flood events (Section 5.3); and Estimate the typical flood hydrograph shape (Section 5.4).
The Womanagh hydraulic model extends to Youghal Bay (the open coast). The hydrological analysis to derive the appropriate design coastal conditions for the corresponding fluvial events has been undertaken as follows: Extraction of the total tide plus surge levels along the coast to be applied at the model downstream extent (Section 5.5.1); Estimate the typical tide plus surge curve (Section 5.5.2).
5.2 Definition of Sub-Catchments
5.2.1 Hydrological Estimation Points
Hydrological estimation points (HEPs) have been chosen at key locations in the River Womanagh and the Ballingeary catchment to form the hydraulic model inflows, intermediate target flows for the model to achieve, and downstream conditions for the model.
The HEPs for the Womanagh catchment were identified through a GIS analysis based on the following principles: A central location within the AFA; Flow gauging stations used in the hydrological analysis; Upstream and downstream limits of each hydraulic model reach; Major confluences which contribute significant flow to the modelled reach; and, Locations where the physical catchment descriptors (PCD) significantly change from the upstream catchment, i.e. catchment centroid more than 25km away, ±0.15 change in BFI and ±0.07 change in FARL.
The GIS analysis was also undertaken for Ballingeary. The HEPs were found to match well the selected HEPs from the Upper Lee model. Therefore, the Upper Lee HEPs were selected for the Ballingeary AFA.
Table 5.1 summarises the selected HEPs prior to hydraulic modelling. Individual maps and catchment descriptors for each AFA and MPW reach are given in Appendix C.
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Table 5.1: Selected HEPs HEP Type Number in UoM19 Gauged 0 Model Inflow 8 Downstream target/inflow 2 Target 15 Downstream tidal 1 TOTAL 26
5.2.2 Sub-Catchment Delineation
UoM19 has been conceptualised into four major hydrological catchments; the River Womanagh, Kiltha River (Castlemartyr), Dissour River (Killeagh) and Upper Lee (Ballingeary), based on the following principles: The characteristics of the sub-catchments and their dominant features; The location of the gauging stations providing information on the catchment response to rainfall; Information on inter-catchment flow; Information on particular flood mechanisms; and The level of detail required for the hydraulic modelling inflows as it focuses on AFAs.
GIS spatial analysis was undertaken on the national digital elevation model to determine slope aspect and subsequently used to identify the watersheds for each catchment. The outputs from this GIS analysis was compared with the automated FSU catchment boundaries and verified against manual interpretation from Ordnance Survey mapping at 1:50,000 scale; previous hydrological reports; and, observations from site visits. Overall, the automated FSU catchment boundaries were found to match the ordnance survey mapping well in areas of steep relief. The largest modification was at Lough Nambrackderg with flows into Lough Allua as shown in Map 5.1. The modifications to the physical catchment descriptors did not significantly change the inflow to Lough Allua downstream.
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Map 5.1: Example Catchment Boundary Modification, Lough Nambrackderg
The other physical catchment descriptors were also reviewed including; average slope (S1085); average rainfall (SAAR); runoff indicators (SPR); permeability indicators (BFI); and attenuation (FARL). Information from the Geological Survey of Ireland (GSI) was also used to assess the impact of underlying geology and aquifers on permeability and groundwater dominance, as well as inform those catchments influenced by karstic systems.
Analysis of the catchment parameters for UoM 19 indicates that: The Womanagh catchment is underlain by karst. The River Dower tributary typically flows through this karstic system via swallow holes which resurface just upstream of the Dower. The highest standard average rainfall is in the west and north east of the River Lee. Ballingeary and areas around Lough Allua tend to have a flashy/rapid response hydrograph when pre- event conditions are already wet. This combined with higher Lough levels from previous rainfall can cause flooding.
All the modifications made to the original FSU database are highlighted in Appendix B.
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5.3 Flood Frequency Analysis
5.3.1 Methodology
The following sections discuss the analysis undertaken to derive the design fluvial hydrographs for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1% AEP events as boundary conditions for the hydraulic modelling.
At ungauged locations, the QMEDrural values were estimated using the 7 variable equation (FSU WP 2.3) based on gauged data from 190 sites across Ireland: QMED 1.237105 AREA 0.937BFISOILS 0.922SAAR1.306FARL2.217DRAIND0.341S10850.185 rural (1 ARTDRAIN 2)0.408
Where: AREA is the total contributing area of the catchment BFISOILS is an index of permeability SAAR is the Standard Annual Average Rainfall between 1961 and 1990 FARL is an index of floodplain attenuation S1085 is the typical slope between 10% and 85% along the river reach ARTDRAIN2 is a proportion of the catchment which is artificially drained.
Pivotal gauged sites were then used to adjust the QMEDrural as recommended by FSU WP 2.3. The pivotal gauged sites were selected from hydrologically similar gauges across Ireland with a preference for geographically close locations to better represent rainfall characteristics in the South West area. Hydrological similarity was guided by the similarity of physical catchment descriptors based on FSU hydrological guidelines: Area of pivotal site within a factor of 5 of the target ungauged HEP; BFI soils index within 0.18 of the target ungauged HEP; SAAR within a factor of 1.25 of the target ungauged HEP; FARL within 0.05 of the target ungauged HEP.
The selected gauges were further assessed for the presence of lakes/reservoirs, significant karstified features and FSU quality of the gauge, to ensure the gauge was suitable to inform the adjustment of QMED at the ungauged target HEP. It should be noted that the FSU 7 variable equation was not developed for catchments less than 5km2 in size due to the lack of reliable gauge records for such small catchments in Ireland. Alternative methods, including the rational method, were found to better represent small catchments on average but tended to over predict peak flows for small lowland catchments (Institute of Hydrology 1978).The modified rational method (1981) is also not suitable to estimate greenfield runoff as it was developed specifically for sewer design. The consensus from an exhaustive literature review was that it was not possible to verify the most appropriate methodology without gauged records.
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The pooled analysis was used to derive appropriate flood growth curves for all ungauged sites. The pooling group AMAX data was collated to create a combined record length of 500 years, which is in accordance with the 5T rule of five times the record length of the target design event, i.e. the 1 in 100 year or 1%AEP event. The criteria were lowered for selection of pooling group sites in the smaller tributary catchments along the Womanagh in order to achieve a balance between finding hydrologically similar sites and achieving the 500 years pooled record length from the target 1%AEP.
The pooling group was reviewed for gauges influenced by karstic geology based on the Geological Survey of Ireland data and compared with the BFIsoils parameter. Sites influenced by karst were not necessarily rejected for the Dower and Ballying Rivers as these catchments are partially underlain by karst and feature several swallow holes. However, gauges 19001, 19031, 21004 and 22009 were also rejected from pooling analysis due to the OPW’s hydrometric team’s concerns with the estimation of high flows at these sites. The pooled L-Moment average for each pooling group was used to identify discordant sites and select the most appropriate statistical distribution.
5.3.2 Estimation of the Index Flood
The selected pivotal sites and adjusted QMED estimates for ungauged HEPS are presented in Appendix C. Table 5.2 summarises the QMED at the downstream of each AFA assessed.
Table 5.2: Summary of Selected QMED AFA Watercourse Pivotal Site Selected FSU QMED (m3/s) Ballingeary Upper Lee 22009 71.1* Castlemartyr Kiltha 19020 11.6 Killeagh Dissour 19020 13.3
* FSSR QMED estimate using DDF 50%AEP rainfall for the critical duration = 76.6 m3/s
The Ballyedmond Gauge on the River Owennacurra (19020) was selected for much of the Womanagh catchment because it is geographically close and hydrology similar thus has similar geology and rainfall characteristics.
The White Bridge Gauge on the River Deenagh(22009) was selected as the pivotal site for Ballingeary because the catchment descriptor’s were hydrologically similar to the Bunsheelin and Upper Lee catchments and it is also located upstream of a Lough with relatively higher rainfall. The FSU QMED estimate using White Bridge is similar to the FSSR rainfall runoff estimate using the Met Eireann’s DDF rainfall values further supporting the use of this pivotal site. However, it is should be noted that the White Bridge gauge is suspected to underestimate flows out of bank and therefore has not been for pooling analysis.
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Appendix C also includes the upper 95th percentile confidence limits based on the factorial standard error of 1.37 (see WP 2.3). The confidence limits will guide sensitivity tests during the hydraulic modelling phase and the screening of preliminary flood mitigation options in areas at significant flood risk. Previous research by the FSR indicated that the index flood is proportional to AREA0.77. This relationship can be used as a check when compared with typical values at gauged sites. The recorded QMED values at gauges were indexed to A0.77/10 and factors were typically found to be higher (20-30) in Ballingeary as the catchment is relatively impermeable. However, factors reduced to less than 7 in the permeable Womanagh catchment due to the underlying Karst as shown in Appendix C.
QMED was also checked to ensure the index flow value increased downstream with contributing area. An example schematic of Ballingeary is provided in Figure 5.1. The Bunsheelin time to peak is faster than the Upper Lee as the Bunsheelin is much steeper. Therefore the peak on the Bunsheelin does not necessarily meet the peak from the Upper Lee at their confluence. The phasing of the two inflows will be refined during the hydraulic modelling to achieve the target peak flow downstream of the confluence.
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Figure 5.1: Schematic of QMED in Ballingeary Bunsheelin 19_1755_1 19.1 m3/s
19_1971_2 20.2 m3/s Ballingeary
19_927_2 Inchgeelagh 24.1 m3/s
19_928_2 19_925_1 19_1714_2 19_869_1 Lee 3 3 3 Lough Allua 39.0 m /s 63.1 m /s 71.1 m /s 74.2 m3/s
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5.3.3 Derivation of Flood Growth Curves
Flood growth curves have been derived for each HEP to estimate design peak flows for rarer, larger magnitude events up to the 0.1%AEP. The pooled L-Moment average for each pooling group was compared with the various distributions to guide the selection of the most appropriate flood growth curve. (Figure 5.2).
Figure 5.2: Flood Growth Curves in UoM19 3.5
3
2.5
2 Flood Growth Factor Growth Flood
1.5
1 50% 20% 10% 5% 2% 1% 0.5% 0.1% AEP Upper Lee at Lough Allua (GLO) Upper Lee at Lough Allua (EV1) Womanagh (GLO) Lee CFRAM Catchment Average
The extreme value (EV1) growth curve was the best fit with the pooled averages for larger, flatter catchments such as the Upper Lee. The flood growth factors are slightly lower than the previous Lee CFRAM pilot catchment average flood growth factors (Table 5.2). However, the generalised logistic (GLO) growth curve better matched the pooled average for the smaller steeper catchments of Bunsheelin, Kiltha and Dissour. The GLO flood growth curves produced similar target 1%AEP flood growth factors compared with the previous Lee CFRAM Study, but provided a more conservative estimate of the rarer events up to the 0.1%AEP.
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Table 5.3: Comparison of Typical Flood Growth Factors in UoM19
Kiltha, Dissour and Upper Lee and Lee CFRAM Pilot Study Womanagh Catchment Bunsheelin Design Flood Growth %AEP FSU Pooled GLO FSU Pooled GLO Curve (GEV) 50 1.00 1.00 1.00 20 1.25 1.25 1.30 10 1.44 1.44 1.50 5 1.63 1.63 1.70 2 1.92 1.92 1.80 1 2.16 2.17 2.10 0.5 2.45 2.45 2.30 0.1 3.25 3.26 2.70
Appendix C summarises the detailed flood frequency analysis and resultant flood flows for UoM19.
5.4 Hydrograph Generation
5.4.1 Ungauged HEPs
Flood extent, depth, velocity and hazard are governed by the shape and duration of a flood flow hydrograph as well as the magnitude of the peak flow. Therefore, design inflow hydrographs were derived at each HEP as follows.
For the ungauged HEPs, the regression-based UPO-ERR-gamma curve was calculated from the physical catchment descriptors in accordance with FSU WP 3.1. The three components of the hydrograph are: Gamma Curve (Rising Limb) - n
x + T n−1 x(n − 1) 푦 = ( r) [퐸푥푝 (− )] Tr Tr
Inflection Point (Starting point of Recession Limb) - Tr
푛−1 Tr 푥표 + Tr 푥표(푛−1) 푥표 = 푦표 = ( ) 퐸푥푝 ( ) √푛 − 1 Tr 푇푟
Exponential Decay Curve (Recession Limb) - C
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푥 − 푥 푦 = 푦 퐸푥푝 (– 표) 표 퐶
The n, Tr and C parameters were estimated from the physical catchment descriptors for the study area and were used to derive an initial estimate of the flow hydrograph. The Tr and C values were subsequently adjusted based on hydrograph pivotal sites from the FSU database.
Pivotal sites 14007 and 16005 were typically applicable for the karstic catchments of Kiltha, Dissour and Womanagh Rivers. These typical hydrograph shapes matched well with the critical duration of 17 hours calculated from the rainfall-runoff parameters. The details of the selected pivotal sites and typical design flood hydrographs for each reach are provided in Appendix D.
5.4.2 Ballingeary HEPs
Chapter 4 noted that flood risk in Ballingeary was a combination of saturated antecedent conditions and elevated levels in Lough Allua. Previous analysis as part of the Lee Pilot CFRAM Study was found to underestimate backwater and associated flood risk compared with flood reports, particularly for the 19th November 2009 event. The rainfall-runoff parameters were calibrated from the beginning to the end of November 2009 event to achieve the recorded flood level in Ballingeary. Full calibration details are provided in Chapter 6. The successive rainfall events over several days caused the level in Lough Allua to become elevated and resulted in significant backwater along the Lee and Bunsheelin to achieve the recorded level in Ballingeary. Figure 5.1 demonstrates the impact of backwater on the stage-discharge relationship in Ballingeary.
Figure 5.3: Modelled Stage-Discharge Relationship over November 2009 86.4
86.2
86
85.8
85.6 Level (mOD) Level 85.4
85.2
85
84.8 0 20 40 60 80 100 120 140 Flow (m3/s)
Model Results from Nov 2009
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It is recognised that an assessment of flood risk in Ballingeary would benefit from an assessment of combined probability between the Lough level and extreme flows along the Upper Lee and Bunsheelin. However, there was insufficient data available of flood events at the Ballingeary and Inchgeelagh staff gauges (19039 and 19043) to undertake analysis.
Therefore the SW CFRAM Study considered a long duration typical storm event profile that replicates the equivalent volume to cause the water levels to rise in Lough Allua based on historic flood events (Figure 5.2). This approach enables the duration of elevated levels in Lough Allua to be considered and therefore the likely duration of flooding.
The selected design event hydrograph/storm profile provides a significant increase in volume compared to the generic FSR rainfall-runoff approach critical duration hydrograph as used in the previous Lee CFRAM Study Pilot (Figure 5.2).
The resultant design rainfall-runoff parameters and storm profile are provided in Table 5.4.
Figure 5.4: Bunsheelin Design Hydrograph 100%
90%
80%
70%
60%
50%
40% % of Peak Flow Peak of %
30%
20%
10%
0% -20 -15 -10 -5 0 5 10 15 20 Time to Peak Flow (Hours)
04/02/2004 27/10/2004 07/01/2005 19/11/2009 Design Hydrograph Appoximating Volume of Historic Events Previous Lee CFRAM Hydrograph
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Table 5.4: FSSR16 Rainfall Runoff Parameters for Ballingeary 2009 Parameters Previous Lee CFRAM Selected Design FSSR16 Parameter Study Parameters Parameters Duration 43 11 43 M5_2Day (mm) 129.4 125 129.4 Jenkinson’s r 0.169 0.20 0.169 (M5 1h/M5_2day) Catchment Wetness Index 130 126 130 (CWI) Time to peak factor (Tp) 1.33 1.00 1.33 Percentage Runoff 93.2 53.9 93.2
5.5 Coastal Conditions
5.5.1 Total Tide plus Surge Levels
Extreme sea levels around the Irish coastline incorporate both the astronomic tide (caused by planetary forcing) and storm surge elements (caused by atmospheric pressure), henceforth referred to as “total tide plus surge levels”. The flood frequency analysis for extreme sea levels has already been undertaken as part of ICPSS (2012) for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1% AEP events.
Total tide plus surge levels have been derived at the tidal outfall of the River Womanagh in Youghal Bay. There is no other AFA or MPW affected by coastal conditions in UoM19. In the absence of gauged data, the CFRAM Study has assumed the same total tide plus surge levels at the tidal outfall (208030,072430) as provided at ICPSS point S31.The hydraulic model of the River Womanagh will be used to transform the total tide plus surge inland.
5.5.2 Design Tidal Curve
The shape of the astronomic curve defines the duration of the rising (flood) and falling (ebb) tide. In deep water the astronomic curve can be assumed to be largely symmetrical depending on the relative phasing of the various harmonic components. However, the shoaling of the tide in shallow estuarine areas can modify the shape.
The admiralty tide tables6 were used to inform time differences in mean high water and low water between the primary port (Cobh) and the local prediction points at Ballycotton to modify the astronomic tidal curve. Storm surges caused by Atlantic storms can often cause elevated sea levels over several diurnal tidal cycles. Surge residuals were calculated from the tidal gauge data along the south west coast for the most extreme events (Figure 5.1). It is apparent that larger events tend to have a shorter duration than the smaller event. The 48 hour duration has been assumed as a credible duration for an extreme surge event and a symmetrical surge profile based on the data at Ballycotton.
6 United Kingdom Hydrographic Office (2013) Admiralty Tidal Tables Volume 1, 2013. 39 296235/IWE/CCW/R015/C 24 June 2016 C:\Users\pig44561\Desktop\296235-IWE-CCW-R015-C-Hydrology Report UoM19.docx
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Figure 5.5: Typical Surge Duration in South West Ireland 1
0.9
0.8
0.7
0.6
0.5
0.4 Surge Residual (m) Residual Surge 0.3
0.2
0.1
0 0 20 40 60 80 100 120 140 160 Duration above Predicted Tide (Hours)
Clonakilty Temporary Gauge Ballycotton Tidal Gauge
The design surge profile was then standardised by the peak surge residual and scaled on top of the astronomic curve to achieve the design extreme sea levels (Figure 5.3). It was assumed that the peak of the surge and the peak of the spring astronomical high tide coincide. This provided a conservative estimate of the combined tidal curve. It is recognised that the peak of the astronomic tide does not necessarily correspond with the peak surge as they are governed by different mechanisms. However, without long term tidal and surge residual data along the South West coast it is not possible to assess the joint probability between these two elements.
Figure 5.4 displays the combined tidal curves for the design 50%AEP event at tidal outfall.
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Figure 5.6: Example Tide Plus Surge Curve Generation at the Womanagh Outfall
2.5
2.0
1.5
1.0
0.5
0.0
-0.5 0 6 12 18 24 30 36 42 48 Water Level (mODM) Level Water -1.0
-1.5
-2.0
-2.5 Time (Hours)
Surge Profile scaled Astronomic curve Design Combined Tidal Curve 50% AEP
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6 Calibration, Sensitivity and Uncertainty
6.1 Flow Determination for Model Calibration
6.1.1 Selection of Events
During the Flood Risk Review, historical flood evidence was collated for those events listed in Chapter 4. Information was gathered from post-flood surveys and anecdotal evidence from local residents. Table 6.1 scores each of these events based on a number of criteria related to the location, hydrology and data availability on a scale of 0 to 3 where: 0 is not available 1 is poor or unlikely 2 is fair or possible 3 is good or likely
These scores are then combined to create an indicative calibration confidence score for the available historical flood evidence in accordance with Guidance Note 237. The following events have been considered for the calibration of AFAs in UoM19 based on the indicative calibration score: 19th November 2009 – extreme fluvial event along the Upper Lee at Ballingeary and Womanagh catchment.
Calibration for the wider Lee catchment has been undertaken in the separate Lee CFRAM Study (2013) and has not been considered further here. Extreme flood events also occurred across the rest of River Lee catchment in August 1986, November 2000, November 2002, December 2006, January 2010, June 2012 as well as March and July 2013. However, there are no reliable records of flooding at the Ballingeary, Castlemartyr or Killeagh for these events. Hence they have not been considered for calibration purposes.
7Jacobs, (January 2013) Guidance Note 23 Model Calibration. Version 1. 42 296235/IWE/CCW/R015/C 24 June 2016 C:\Users\pig44561\Desktop\296235-IWE-CCW-R015-C-Hydrology Report UoM19.docx
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Table 6.1: Selection of Calibration Events in SW CFRAM Study AFAs
2
1
4 3 Indicative
Calibration
Accuracy Accuracy of Flow Estimate Likely Accuracy of Gauged Level Estimate Known Hydraulic Conditions Likely Accuracy of Spot Levels Reliable Flood History Event AFA/ Watercourse Likely Score Calibration Approach 04/02/2004 Ballingeary/ Upper Lee Limited level data to calibrate hydrological rainfall-runoff + Bunsheelin model and hydraulic model to. Photos provide extent of 1 0 2 0 3 5 flooding. Modelled outline and levels to be verified against reported areas affected relative to flood frequency. 27/10/2004 Ballingeary/ Upper Lee Limited level data to calibrate hydrological rainfall-runoff + Bunsheelin model and hydraulic model to. Modelled outline and levels 1 0 1 0 3 4 to be verified against reported areas affected relative to flood frequency. 07/01/2005 Ballingeary/ Upper Lee Limited level data to calibrate hydrological rainfall-runoff + Bunsheelin model and hydraulic model to. Locations of properties 1 0 2 0 3 5 flooded known. Modelled outline and levels to be verified against reported areas affected relative to flood frequency. 19/11/2009 Ballingeary/ Upper Flow estimate subject to uncertainty without flow or level Lee + Bunsheelin gauge data to verify rainfall-runoff parameters. Calibrate 1 0 2 2 3 8 river channels and flood extent taking note of reported blockages at bridge structures. 19/11/2009 Castlematyr, Flow estimate subject to uncertainty without flow or level Killeagh, gauge data to verify transfer from neighbouring catchment. Womanagh/Kiltha, 1 0 2 2 2 7 Calibrate river channels and flood extent taking note of Dissour and reported blockages at bridge structures. Womanagh 15/01/2011 Ballingeary/ Upper Lee Limited flow data, rainfall data limit accuracy of flow + Bunsheelin estimate and model calibration. Modelled outline and levels 0 0 1 2 1 4 to be verified against reported areas affected relative to flood frequency.
Note 1: 3 = gauged flows are available in the catchment, 2 = gauged flows used from pivotal gauges nearby, 1 = rainfall data used to estimate flows and 0= no flow estimate available Note 2: Hydraulic conditions relate to controls on water levels during a flood e.g. level of blockage, wall collapse etc. Note 3 Levels during a known flood event NOT at a gauged location that represents a true flood level rather than a localised issue. Note 4 Any information that includes date/time, precise location and mechanism of flooding.
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6.1.2 Calibration Hydrology
19th November 2009
The November 2009 event affected the entire Lee catchment including Ballingeary, Castlemartyr and Killeagh. A number of post flood surveys undertaken after the flooding subsided provided detailed spot levels and flood extents which can be used in the model calibration. However, the estimation of flood event rarity varied widely across UoM198.
The following steps were undertaken to derive the hydrographs for the ungauged HEPs in the Womanagh catchment: Transfer the representative rainfall profile from the hourly data at Cork Airport to the gauged locations based on the ratio of the event total at each AFA. Derive the FSSR16 catchment average rainfall parameters for the gauged catchment from Met Eireann DDF results and physical catchment descriptors. Apply the transferred rainfall profile and derived parameters to estimate the flow hydrograph at the Ballyedmond gauge. Adjust percentage runoff, catchment wetness index and time to peak to calibrate the rainfall-runoff flow hydrograph to the recorded flow hydrograph at the gauge. Apply the calibrated percentage runoff, transferred rainfall profile and derived parameters to derive the rainfall-runoff flow hydrograph at the ungauged HEPs scaled to meet the gauged %AEP estimate (Figure 6.1). Extract the corresponding tidal conditions from the nearby Ballycotton gauge (Figure 6.2).
There was no flow or level gauge data available at Ballingeary or Lough Allua for the November 2009 event. Recorded gauge information downstream did not adequately represent the severity, duration or hydrograph shape that resulted in flooding in the town8. Therefore, calibrated flows were derived as follows: Initial flows were derived using the FSSR16 approach based on the scaled rainfall profile from Cork Airport record to Ballingeary rainfall gauge (3004). These initial flows were applied to the truncated Upper Lee hydraulic model 9(Halcrow 2013) and run from the 5th October 2009 to the 23rd November 2009 to consider the preceding saturated period. The rainfall runoff parameters were iteratively calibrated until the modelled flow (Figure 6.3) produced a water level in the hydraulic model that matched the recorded peak water level of 86.8 mODM at Ballingeary (Figure 6.4). Please note only the peak water level was available from 2009 flood report and no continuous water level data was available in Ballingeary.
The resultant hydrographs for each AFA are presented in Figures 6.1, 6.2 and 6.3. The corresponding rainfall-runoff parameters are provided in Table 6.2.
8 Halcrow (September 2011) November 2009 Post Event Analysis and Review (PEAR) 9 The Upper Lee model review and truncation details are provided in the SW CFRAM Study Hydraulics and Mapping Report Unit of Management 19. 44 296235/IWE/CCW/R015/C 24 June 2016 C:\Users\pig44561\Desktop\296235-IWE-CCW-R015-C-Hydrology Report UoM19.docx
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Figure 6.1: 2009 Calibration Inflows to Castlemartyr and Killeagh 35
30
25
20
15 Flow (m3/s) Flow
10
5
0
17/11/2009 00:00 18/11/2009 00:00 19/11/2009 00:00 20/11/2009 00:00 21/11/2009 00:00 22/11/2009 00:00 23/11/2009 00:00
19020 recorded flow 19020 Calibrated FSSR16 Castlemartyr inflow Killeagh inflow
Figure 6.2: 2009 Tidal Conditions at the Womanagh Outfall 2.5
2
1.5
1
0.5
0
-0.5
Water Level (mODM) Level Water -1
-1.5
-2
-2.5
17/11/2009 00:00 18/11/2009 00:00 19/11/2009 00:00 20/11/2009 00:00 21/11/2009 00:00 22/11/2009 00:00 23/11/2009 00:00
Ballycotton Recorded Tide+Surge Level
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Figure 6.3: 2009 Calibration Inflows to Ballingeary at Lough Allua 160
140
120
100
80
Flow (m3/s) Flow 60
40
20
0
22/11/2009 00:00 17/11/2009 00:00 17/11/2009 12:00 18/11/2009 00:00 18/11/2009 12:00 19/11/2009 00:00 19/11/2009 12:00 20/11/2009 00:00 20/11/2009 12:00 21/11/2009 00:00 21/11/2009 12:00 22/11/2009 12:00 23/11/2009 00:00 23/11/2009 12:00
FSSR16 Initial Iteration1 - modified CWI and Tp Iteration 2 - modified PR, CWI and Tp
Figure 6.4: 2009 Calibrated Water Levels at Inchigossig Bridge Ballingeary 87
86.8
86.6
86.4
86.2
86 Water Level (mODM) Level Water 85.8
85.6
85.4
17/11/2009 00:00 17/11/2009 12:00 18/11/2009 00:00 18/11/2009 12:00 19/11/2009 00:00 19/11/2009 12:00 20/11/2009 00:00 20/11/2009 12:00 21/11/2009 00:00 21/11/2009 12:00 22/11/2009 00:00 22/11/2009 12:00 23/11/2009 00:00 23/11/2009 12:00
FSSR16 Initial Iteration 1 - modified CWI and Tp Iteration 2 - modified PR, CWI and Tp Reported Peak Level
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Table 6.2: November 2009 FSSR16 Rainfall Runoff Parameters
Ballingeary Ballingeary Ballingeary 19020 Castlemartyr Killeagh Initial Iteration 1 Iteration 2 Ballyedmond Transferred Transferred Parameters Parameters Calibrated Calibrated Parameters Parameters FSSR16 Parameters Parameters Based on Based on Parameter -Selected -Selected 19020 19020 Cork Airport 63.8 63.8 63.8 63.8 63.8 63.8 Rainfall 18th – 20th November 2009 (mm) AFA/Gauge 111 111 111 69.5 52.0 52.0 th Rainfall 18 – 20th November 2009 (mm) Rainfall 1.74 1.74 1.74 1.09 0.82 0.82 adjustment factor M5_2Day (mm) 129.4 129.4 129.4 72 73 68 Jenkinson’s r 0.17 0.17 0.17 0.26 0.27 0.27 (M5 1h/M5_2day) Catchment 126.6 130 130 130 130 130 Wetness Index (CWI) Time to peak 1 1 1.33 0.60 0.60 0.60 factor (Tp) Percentage 53.9 53.9 93.2 39.33 39.33 39.33 Runoff
The Ballingeary flows (and water levels) were not sensitive to the CWI and Tp rainfall-runoff parameters (Iteration 1), but were highly dependent on the percentage runoff selected (Iteration 2). The high percentage runoff reflects the saturated nature of the catchment and intense rainfall causing the overland surface water runoff which was observed by local residents (see Chapter 4). It is unlikely that a percentage runoff of over 90% is representative of most catchment conditions. However, it is more representative of the specific catchment conditions that result in flooding at Ballingeary.
The time to peak used in Castlemartyr and Killeagh has been used to inform the selection of the hydrograph pivotal site and adjustment of the Tr, C and n parameters (Section 5.4.1).
The longer duration associated with successive rainfall events has been used to inform the design hydrograph in Ballingeary in order to consider event which results in the backwater effects from Lough Allua (Section 5.4.2).
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6.2 Uncertainty and Sensitivity Testing
The SW CFRAM study requires an understanding of sensitivity in hydrological and hydraulic parameters in order to inform the uncertainty analysis in the flood mapping process. The key areas of uncertainty in the hydrological analysis of UoM19 are: Uncertainty in the design peak flows from uncertainty in QMED and the flood growth curve. Uncertainty in the volume of the flood event based on the duration to generate the design hydrograph in Ballingeary. Uncertainty in the transformation of tide plus surge levels for the Womanagh outfall.
All sensitivity analysis has been assessed at the 1%AEP as this is the target fluvial AEP for the CFRAM study and the AEP event used in planning decisions and in agreement with Guidance Note 26. Uncertainty in flow and level for more frequent events are considered within the error bounds for the 1%AEP.
Sensitivity in Design Peak Flows
The FSU WP 2.3 states a factorial standard error (FSE) of 1.37 in the QMED rural regression equation based on the 190 gauges across Ireland used to derive the equation coefficients. Approximate 95% upper confidence limits for QMED were then calculated as follows:
95% 푐표푛푓푖푑푒푛푐푒 푙푖푚푖푡 = 푄푀퐸퐷 ∗ 퐹푆퐸2
The uncertainty in the flood growth curves and pooling groups selected for a sample of 85 gauging stations across Ireland was investigated as part of the FSU WP 2.2. The percentage standard error in design peak flow varied from 4.0 to 9.0 at the target fluvial 1%AEP.
The upper confidence limits from each source of peak flow uncertainty were combined to estimate overall uncertainty in design peak flow at the target 1%AEP for ungauged HEPs. This resultant upper limit of the 1%AEP flow was typically within 10% to 30% of the design 1%AEP peak flow (see Appendix C). Therefore, it was deemed that a sensitivity test of a 30% increase in peak flow at the target 1%AEP should be considered in the subsequent hydraulic modelling of all HEPs in UoM19.
Sensitivity to the Volume of the Flood Event at Ballingeary
Flood risk in Ballingeary can be deemed to be volume dependent, as Lough Allua has a limited capacity before backwater effects raise water levels in the town and cause flooding. Section 5.4.2 identified that the duration of the design storm event in Ballingeary was critical to the volume of the flow hydrograph. For the same peak flow, the volume of the flood event could vary as much as 180% between the FSR critical storm duration and the volume-critical calibrated 58 hour storm event (Table 6.3). The design event is assuming a conservative duration and associated volume based on the recent flooding in 2009. Assessment of longer durations would not be feasible for the Ballingeary and Lough Allua catchments. Therefore the sensitivity test focuses on a lesser event with lower lough levels to assess the sensitivity to backwater.
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Table 6.3: Sensitivity to Volume on the Bunsheelin River Volume-Critical Calibrated Scenario FSR Critical Duration Duration Storm Duration 11 58 Catchment Conditions Assumed Unsaturated Saturated Lough Allua Conditions Assumed Storage capacity available No storage capacity available from preceding events Volume of Standardised Hydrograph 30950 86767 (Q/Qp) (m3) Difference to FSR critical duration (m3) N/A 55817 (+180%)
The subsequent hydraulic modelling will assess the impact of the 11 hour storm duration on water levels and flood extent for the target 1%AEP event as a sensitivity test.
Sensitivity to Downstream Conditions
The total tide plus surge levels have been extracted from the RPS coastal model at offshore points along the coast based on Extreme Value Analysis. There is some uncertainty in the transformation of the total tide plus surge level to the nearshore at the Womanagh outfall as the frictional effects of the nearshore bathymetry has not necessarily been modelled. There is also inherent uncertainty in the derivation of the extreme values for the rare %AEP events.
It was not possible to quantify the uncertainty at the Womanagh outfall without long term tidal gauge records. The nearby Ballycotton tidal gauge records are less than 5 years in length, making an assessment of extreme total tide plus surge levels unsuitable. Therefore, the GN 22 guidance was applied to consider a 0.5 m increase in water levels for the design events which is broadly equivalent to the mid-range future scenario.
Downstream conditions for Lough Allua are subject to the stage-discharge boundary and hydraulic parameters applied. Sensitivity tests on these hydraulic conditions will be undertaken during the subsequent modelling and mapping stage.
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7 Summary of Design Hydrology
The design flows from this hydrology report inform the inflows to the hydraulic model to assess flood risk from the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1%AEP fluvial and tidal flood events. The key hydrological findings for design flows in UoM19 are as follows: Historic flood events Major fluvial flood events were identified in 2009 and 2011 at Ballingeary, Castlemartyr and Killeagh. Extreme flood events also occurred across the rest of River Lee catchment in August 1986, November 2000, November 2002, December 2006, January 2010, June 2012; as well as March and July 2013. However, there are no records of flooding available at the Ballingeary, Castlemartyr or Killeagh for the aforementioned events. The largest reported event was on 19th November 2009 – 20th November 2009. The 0.63%AEP estimate of the November 2009 event from nearby gauges was not necessarily representative of the event that occurred in Ballingeary due to the variation in rainfall. The model extracted results suggest a 0.1%AEP for this event at Ballingeary. A 15%AEP was estimated for the November 2009 flood event in Womanagh catchment (including Castlemartyr and Killeagh) based on the Ballyedmond gauge in a neighbouring catchment. The calibration of the Ballingeary and Womanagh catchment models will be based on the 19th November 2009 event. Design flood flows Peak flood flows were derived along the Upper Lee, Bunsheelin River, Kiltha River, Dissour River and Womanagh River within the AFAs for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1%AEP events using the recommended FSU methodology outlined in Work Package 2.2 and 2.3. The design flood hydrograph for ungauged HEPs in the Womanagh catchment were based on the hydrograph pivotal site fitted to the observed median hydrograph at the gauges within the catchment. The design flood hydrograph for Ballingeary was derived using FSSR16 rainfall-runoff approach using rainfall runoff parameters calibrated to the November 2009 event. A 43 hour duration was used to approximate the volume of historic events that elevate levels in the Lough and cause flooding from the backwater as reported by the Local Engineers and residents. Design coastal conditions The design extreme sea levels were extracted from the ICPSS for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1%AEP tidal events. ICPSS point S_31 was used to derive the total tide plus surge levels at the Womanagh outfall. The astronomic curve and surge profile were derived from the admiralty predicted astronomic tide and typical duration of surge events in the South West. The final design tidal curve was derived from the combined astronomic tide and design surge profile scaled to meet the design extreme sea levels. Uncertainty and Sensitivity There is significant uncertainty in the duration of flooding and catchment conditions that result in flooding at Ballingeary. The effective duration could vary between 11 and 43 hours at Ballingeary resulting in a 180% variation in volume. A sensitivity test on a shorter 11 hour duration storm event has been proposed to assess flood risk during unsaturated catchment conditions.
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The uncertainty of the 1%AEP target peak flow was estimated to range up to +30% in UoM19 ungauged HEPs which will inform the sensitivity tests in the hydraulic modelling. A sensitivity test which raises the total tide plus surge level by 0.5m has been proposed in accordance with GN22.
Tables 7.1 and 7.2 provide the design peak flows and total tide plus surge levels at key locations respectively. These flows and levels are subject to change following the subsequent integration into the hydraulic model and hydraulic calibration processes.
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Table 7.1: UoM19 Design Peak Flood Flows at Key Locations HEP ID Gauge/ Ungauged Location Design Peak Flows (m3/s) 50%AEP 20%AEP 10%AEP 5%AEP 2%AEP 1%AEP 0.5%AEP 0.1%AEP Castlemartyr AFA 19_1909_9 Kiltha upstream 7 9 10 11 13 15 17 23 19_1909_15 Kiltha at Castlemartyr 9 11 12 14 17 19 21 28 19_1909_17 Kiltha at Womanagh Confluence 9 11 12 14 17 19 21 29 Killeagh AFA 19_686_15 Dissour at Killeagh 10 12 14 16 18 21 23 31 19_1798_3 Dissour at Womanagh Confluence 12 15 17 19 22 25 29 38 Womanagh MPW 19_1266_7 Womanagh upstream of the Kiltha 2 3 3 4 5 5 6 8 19_705_1 Womanagh downstream of the Kiltha 12 14 16 18 22 24 27 36 19_1823_1 Womanagh downstream of Ladysbridge 13 16 18 20 24 27 31 41 19_1833_1 Womanagh downstream of the Dower 16 20 23 26 30 34 39 51 19_1794_1 Womanagh downstream of the Dissour 31 38 44 49 58 65 74 98 19_1941_2+ Womanagh tidal outfall 33 41 46 53 62 70 79 104 Ballingeary AFA 19_927_2 Bunsheelin at Lee Confluence 19 24 27 31 36 41 46 61 19_928_2 Upper Lee upstream 27 34 39 43 49 54 58 69 19_1714_2 Upper Lee at Lough Allua 49 61 70 79 93 105 119 158
Table 7.2: UoM19 Design Total Tide Plus Surge Levels Location Location Design Total Tide Plus Surge Levels (mODM) 50%AEP 20%AEP 10%AEP 5%AEP 2%AEP 1%AEP 0.5%AEP 0.1%AEP Womanagh outfall ICPSS Point S31 2.19 2.28 2.36 2.42 2.52 2.58 2.65 2.81
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8 Considerations for Hydrological and Hydraulic Model Integration
8.1 Inflows
Design hydrographs have been derived at HEPs to represent the hydrological processes at Ballingeary, Castlemartyr, Killeagh and the lower reaches of the Womanagh as discussed in Chapter 5. The HEPs will be integrated with the subsequent hydraulic models as follows: Point inflows at the upstream model extents; Point inflows at key tributary inflows; Lateral inflows representing the inflow from the intervening areas between target HEPs.
The point inflows representing the upstream model extents and tributary inflow will be integrated with the relevant cross-section in the hydraulic model accounting for a significant displacement from the HEP calculated location. The lateral inflows will be integrated with the relevant cross-sections at locations which fit the following criteria: Natural inflows from minor watercourses which are not considered explicitly within the hydrology; Overland flow paths identified from surveyed low points in the river bank and site walkover.
The lateral inflows will be calculated from the difference between the design flow hydrographs from the upstream and downstream HEPs for a reach. The resultant hydrograph will be distributed evenly across those locations where the contributing area increases linearly downstream, or area weighted where the contributing area increases disproportionally downstream. Table 8.1 outlines the total number of inflows based on the criteria above for each model. These will be further refined and discussed in the hydraulics report.
Table 8.1: Model Inflows Model Number of Inflows Ballingeary 3 Castlemartyr 3 Killeagh 2 Womanagh 10
In order to enhance the modelling outputs and ensure hydrological continuity along the larger catchments, the hydraulic parameters will be adjusted and hydrological inflows scaled such that the hydraulic model maintains the design peak flows along the reach. However, it should be noted that the design fluvial flows do not consider the following hydraulic processes: Backwater effect at confluences; Exchange of flows between tributaries at confluences; and, Significant modification to the hydrograph shape due to floodplain attenuation and/or hydraulic structures.
Therefore, it is not appropriate to calibrate the hydraulic model to HEPs upstream of confluences where there are significant out-of-bank flows.
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In UoM19, the hydrograph shape and flood duration have been derived using the FSU approach outlined in Chapter 5. The duration of the ungauged inflows are based on the FSR time peak equation (function of SAAR, S1085 and MSL) but will be iteratively refined to achieve the flow at the HEPs as part of the hydraulic modelling. The intermediate inflows account for the difference in duration between the target HEPs within the same hydrological catchment. Table 8.2 outlines preliminary design storm durations for UoM19.
Table 8.2: Preliminary Design Storm Duration AFA/MPW Method Design Duration (Hours) Ballingeary FSR estimate 43 (approximating volume of historic events) Castlemartyr FSR estimate 13 Killeagh FSR estimate 13 Womanagh FSR estimate 13
8.2 Downstream Conditions
The downstream conditions will be defined for each model as outlined in Table 8.2 to fully account for the relevant fluvial and tidal backwater effects as appropriate. An iterative approach will be used to phase the design tidal curves so that the peak tide coincides with the peak flow as a conservative estimate of flood risk.
Table 8.3: Downstream Boundary Conditions Model Downstream Condition Castlemartyr Stage-discharge relationship based on the downstream water slope in the Womanagh model. Killeagh Stage-discharge relationship based on the downstream water slope in the Womanagh model. Womanagh Full tidal boundary using the results from the design tidal curves set out in Chapter 6. Ballingeary Stage-discharge relationship based on the water slope downstream of Inchigeelagh from the Lee CFRAM Study.
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9 Hydrogeomorphology
9.1 Approach
The hydrogeomorphological processes ongoing in the river channels can have a significant impact on flood flows and the resultant flood risk. The assessment of hydrogeomorphological features focuses on whether the processes appear to be in equilibrium and whether there are any processes taking place at present which are likely to affect the flood risk. This may include: Recent interventions to the channel/hydrology to control flood risk which have accelerated erosion or deposition; The use of inappropriate bank protection which may transfer erosion downstream; or Straightening or reprofiling the channel which may cause the watercourse to attempt to revert back to a more natural state.
This has included an assessment of: Typical land use, soils and geology as provided in Chapter 2; Channel gradient based on the river channel survey; Bank and bed material and condition based on site visits, aerial photographs and survey photographs; Channel planform based on Ordnance Survey maps and aerial photography; and The presence of structures (bridges, weirs, culverts) /channel modifications (e.g. straightening, bank protection, bank reprofiling).
The survey data and photographs are provided in a separate survey report. Key photographs have been included in this report to inform the analysis.
9.2 Assessment
The HPW and MPW were spilt into broad reaches of similar hydrogeomorphological characteristics based on the approach above, and an assessment made on the current erosion and deposition features (Map 9.1).
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Map 9.1: Hydrogeomorphological Reaches
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Bunsheelin and Upper Lee Catchment (Ballingeary)
Photo 9.1: Siltation at The Bunsheelin River and the Upper Lee were observed to be actively Inchinossig Bridge after the 2009 depositing in-channel based on site observation, aerial photography and Event photos provided by the local action group (An Coiste Forbartha, Béal Átha an Ghaorthaidh) after the 2009 flooding. The deposition of silts and gravels downstream of Inchinossig Bridge on the Lee and the R584 Bridge on the Bunsheelin is a natural process in response to reduced velocities as the steep rivers enter the flat water body of Lough Allua. The river channel was ‘cleaned’ and excessive sediment and wooded debris removed in late 2011 thus increasing the river capacity for smaller events. However, the underlying soils are classified as alluvial in this reach indicating a long term accretion of lacustrine deposits from the Lough flooding. Therefore, the deposition observed is an ongoing natural process exacerbated by the upland catchment management.
There is a risk that surface water runoff increases in the first 10 years after afforestation associated with the land drainage, thus increasing the sediment load downstream. This may have contributed to an increased sediment load in the Upper Lee in the past. However, any new forests will Source: An Coiste Forbartha, Dec 2009 be managed in accordance with SFM principles, including a requirement that broadleaf buffer strips be planted in commercial forests adjacent to streams and rivers to slow runoff (Forest Service, 2000). Deposition is further encouraged by the wooded nature of Upper Lee catchment which results in large woody debris in-channel and the trapping of sediment downstream.
Womanagh Catchment (including Castlemartyr and Killeagh)
Photo 9.2: Castlemartyr Bridge The Womanagh catchment is classed as “at risk of not achieving good status” which includes the River Kiltha and Dissour. The upper reaches of the Kiltha and Dissour Rivers are largely natural but relatively shallow with gravel beds. The heavily vegetated banks introduce large woody debris into the channel which can encourage deposition locally. The river channel becomes heavily modified and straightened as the Kiltha and Dissour enter the towns of Castlemartyr and Killeagh with a series of walls and bank protection to limit bank erosion at bridge structures (e.g. Castlemartyr Bridge) and at the outside of river bends (e.g. Cois Abhainn, Killeagh).There are a number of low weir structures and bridge structures which modify in-channel flows, encouraging deposition upstream and scour of the bed downstream as velocities are constricted over and through these structures. The greatest deposition was observed at
Killeagh Bridge, where the pier structures encourage deposition in the Source: Murphy Surveys, Nov 2012 areas of low velocity upstream.
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Photo 9.3: Tidal Embankments The Womanagh is relatively flat in comparison with the Kiltha and Dissour on the Womanagh Rivers. There is significant in-channel and river bank vegetation in its upper reaches until Old Finisk Bridge. Large woody debris was observed during site visits and in survey photographs. This debris can collect together modifying flows paths and encourages local deposition upstream of the debris. Debris is likely to be washed away during high flows, but could pose a blockage risk at the relatively small bridge openings downstream at Ladysbridge. Downstream of Old Finisk Bridge, the Womanagh becomes increasingly tidal and embanked, disconnecting the river from its natural floodplain. This has encouraged deposition in the intertidal zone in-channel, and reduced sediment and nutrient supply to Source: Murphy Surveys , Nov 2012 the floodplain.
Significant intertidal mud flats are present near Pilmore as the channel widens, and the spit features at the outfall protect the estuary from extreme coastal conditions. The Ballymacoda Bay Special Protected Area (SPA) comprises the estuary of the Womanagh River downstream of Crompaun Bridges and includes an area of set-back from the original tidal embankments at Clonpriest West. According to aerial photographs the embankments were breached at 204990,072536 between 2000 and 2005 which reconnected the tidal channel with its floodplain. This reconnection has encouraged deposition on the floodplain rather than in the channel, and was undertaken for habitat creation rather than flood risk management explicitly.
9.3 Impact on Flood Risk In summary, the River Kiltha and Dissour are deemed to be largely in equilibrium along their length, but the presence of large woody debris may present a blockage risk to structures downstream. Localised deposition was observed upstream and downstream of Killeagh Bridge, which could reduce structure capacity over time, although the rate of deposition was not deemed to be significant at present. The River Womanagh was observed to be depositing in its tidal lower reaches which may require regular dredging to maintain channel capacity overtime. A set-back scheme downstream of Crompaun Bridge has provided additional offline flood storage during period of tide-locking, which may alleviate flooding. The narrow entrance to this set-back area is liable to blockage because it is at right angles to the main direction of flow, resulting in deposition in the areas of flow inefficiencies. In Ballingeary, the Bunsheelin and Upper Lee are in a state of deposition in response to reduced velocities as the steep rivers enter the flat water body of Lough Allua. Excessive build-up of the gravel bars and in- channel vegetation downstream of the Bridge may reduce channel capacity for smaller events. Dredging works have been carried out since 2009 to address some of these issues. However, backwater from Lough Allua is likely to be the dominating factor on downstream capacity and flood risk for larger events. The rate of deposition and blockage due to wooded debris at the bridges in Ballingeary should be considered in the maintenance of flood risk management options.
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10 Joint Probability
10.1 Overview
The design flows on each river reach and the total tide plus surge levels provided in Chapter 8 have been derived independently of each other. In reality, there can be dependency between sources of flooding which can be described by the joint probability to achieve a target %AEP event. The CFRAM study considers the following joint probabilities: Fluvial-fluvial – Where a range of combinations of flow on a main river combines with flow on a tributary to generate a specific %AEP flood downstream. Fluvial-coastal – Where an approaching depression generates a storm surge which combines with a river flood to generate a specific %AEP at the coast.
10.2 Fluvial-Fluvial Dependence
The joint probability between fluvial flows on the main watercourse and its tributaries was guided by the methodology set out in Flood Studies Update Work Package 3.4. The FSU methodology assessed the dependence between fluvial inflows based on the distance between catchment centroids; the ratio in catchment area; and, the difference in FARL, a measure of floodplain attenuation. Table 10.1 sets out the different combinations in UoM19 for tributary inflows to achieve the target %AEP on the main watercourse.
In UoM19, the joint probability between the main river and the tributaries was found to be largely dictated by the size of the incoming catchments relative to the main watercourse. The joint probability of flows along the Upper Lee and Bunsheelin River were found be similar %AEP to each other as the two catchments contributed approximately half of the downstream flow in each case. The Kiltha and Upper Womanagh Rivers have a similar relationship as they are of a similar size.
The joint probability %AEP on the smaller tributary inflows, such as the Dower and Dissour, tended to be the more frequent smaller events in order to achieve the target flow on the main watercourse. The different joint probability combinations provided in Table 10.1 will be assessed at the modelling and mapping phase to establish the largest flood outline.
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Table 10.1: Joint Probability Combinations Target %AEP at downstream HEP on main watercourse 50% 20% 10% 5 % 2 % 1% 0.5% 0.1% Reach inflow WP 3.4 Table 13.1 Scenario Associated %AEP of Tributary Inflow Ladysbridge Catchment centroid within 25km 71.0% 46.0% 35.0% 23.0% 10.0% 6.1% 3.8% 1.2% Dower Significantly smaller catchment (Ratio of area greater than 2.7) Ballying Difference in FARL less than 0.07 Dissour Upper Lee-Bunsheelin Catchment centroid within 25km 57.0% 30.0% 17.0% 9.4% 4.3% 2.3% 1.2% 0.3% Womanagh-Kiltha Similar sized catchment (Ratio of area within 2.7) Difference in FARL less than 0.07
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10.3 Fluvial-Coastal Dependence
Fluvial-coastal dependence between river gauges on the Lower Lee and tidal gauges in Cork Harbour were assessed as part of the Lee CFRAM pilot study. This analysis concluded there was some correlation between high flows and higher storm surges as the storm events that caused the surge also caused high rainfall in the Lower Lee catchment. Extensive sensitivity analysis was undertaken on the 0.5% AEP event as part of the pilot study and found the two main critical scenarios to be as follows: Target flow and the MHWS tide; and 50%AEP Flow and the target Total tide plus surge level.
The same approach has been applied to the outfall of the Womanagh in the absence of gauged tidal levels and river flow data at this location.
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11 Future Scenarios
11.1 Potential Climate Changes
The range of potential impacts of climate change varies as there are significant uncertainties associated with global climate predictions and local hydrological variation for periods more than 20 years in the future. Therefore, two scenarios have been assessed to quantify the sensitivity of flood risk to potential climate change namely, the Mid-Range Future Scenario (MRFS) and the High End Future Scenario (HEFS) as detailed in Table 12.1.
Table 11.1: Allowance for Climate Change in Catchment Parameters Catchment Parameter MRFS HEFS Extreme Rainfall Depth +20% +30% Flood Flows +20% +30% Mean Sea Level Rise +0.5m +1.0m Land Movement -0.5mm/year -0.5mm/year i.e. +0.05m relative sea level i.e. +0.05m relative sea level rise over 100 years rise over 100 years
Source: Reproduced from Appendix F of National Flood Risk Assessment and Management Programme, Catchment-Based Flood Risk Assessment and Management (CFRAM) Studies, Stage I Tender Documents: Project Brief.
The land movements quoted in Table 6.1 refer to postglacial readjustment of the underlying tectonic plate since the last glacial period in Southern Ireland. This readjustment is not a climatic change but it does alter the effective rate of sea level rise predicted with climate change.
It is important to note that the increase in sea level and flood flows applies to the entire tidal curve and flood hydrograph, not just the peak.
11.2 Potential Catchment Changes
11.2.1 Urban Development
The way in which the land is used can significantly impact the flow routes across the catchment, how much rainfall is stored, how much infiltrates into the ground, and how much evaporates. Future urban development is likely to influence hydrology and flood risk in the following ways: Increase the surface runoff from the catchment by increasing the area covered by impermeable surfaces on previously undeveloped (“Greenfield”) sites; Increase the proportion of surface runoff draining to urban drainage networks; and, Increase the proportion of the population, properties and infrastructure within areas of flood risk.
All of these changes cause more water to reach the river channels quicker and affect more people, property and environments.
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The SW CFRAM study considers the urban areas of Ballingeary, Castlemartyr and Killeagh in UoM19. These are located in the rural Western Area and more urban Greater Cork Area of the Regional Plan. The larger urban centres in the wider Lee catchment have been assessed under the wider Lee CFRAM pilot study.
Table 12.2 outlines the urban growth in housing units according to the South West Regional Authority (SWRA) Planning Guidelines and linear extrapolation to estimate urban growth for the MRFS and HEFS. The SWRA data is based on a 2010 baseline and accounts for the economic downturn in forecasts beyond 2010. The MRFS growth rate has been estimated on the projected increase in housing units between 2016 and 2022 accounting for the economic downturn. The HEFS growth rate has been estimated on the average projected increase from the entire regional plan, with a lesser impact from the economic downturn.
Table 11.2: Future Urban Growth SWRA Plan MRFS% HEFS % Housing Units Required Area Growth Growth 2006 2010 2016 2022 Cork Gateway 111,581 127,749 153,000 182,044 3.16% 3.54% Mallow Hub 4,191 5,341 7,500 10,498 6.66% 8.05% Ring towns 42,951 46,472 50,317 54,160 1.27% 1.38% and Rural areas Greater Cork 154,532 174,221 203,317 236,203 2.70% 2.96% area Tralee 15,284 17,099 20,318 23,573 2.67% 3.16% Killarney Hub area Kerry linked 29,565 33,541 39,855 46,239 2.67% 3.15% hub Northern Area 33,497 37,993 43,885 46,186 0.87% 1.80% Western area 36,606 41,745 47,989 50,729 0.95% 1.79%
Source: South West Regional Plan. BOLD text signifies relevant areas to the UoM.
In agreement with OPW, the forecast growth in housing units was assumed to be on previously undeveloped land as a conservative estimate of urbanisation. The MRFS and HEFS do not account for any beneficial impacts of Sustainable Drainage Systems in the future.
11.2.2 Land Use Change
The majority of the Ballingeary and Womanagh catchments are currently rural and dedicated to agricultural or pastoral use. The type of crops that are grown, the way the land is prepared and changes in land drainage practice all affect how quickly rainfall reaches the watercourses. Land management practices also affect the amount of silt that gets washed from the fields into the rivers during rainfall events. Given that these processes can influence flood risk, both in a positive and negative way, we need to consider how land use and land management may change in the future.
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There are many uncertainties surrounding the future of agriculture within the catchment. Land use will depend upon society’s aspirations and needs, and will be driven by policies being implemented by both the Irish government and the EU. The pressures and drivers that will affect how land is used in UoM22 include: change to agricultural policy and land management subsidies in the EU; opening of world markets making agriculture and pastoral activity less economically viable; growth in world population increasing demand for food production; change in typical annual temperatures with climate change resulting in changes in crop types grown; diversification to other land uses, particularly for tourist related attractions; drive to enhance and restore environmental habitats and landscapes; drive to reduce carbon dioxide emissions through the use of carbon sinks and biofuels; and, increasing energy prices could lead to increased biofuel use or make importing of produce uneconomic.
All of these changes can either lead to intensification of activities and associated increased land drainage and runoff or reduction in activities with associated increased infiltration and reduced runoff. There is very limited information on most of these land cover changes as they are often driven by economic factors which are rarely predicted more than 5 years into the future.
Deforestation to increase productivity of agricultural land can be a significant impact on rural land use in Europe under the EU Common Agricultural Policies. Forested areas intercept rainfall, increase storage and infiltration and slow surface water runoff into the river channels. The removal of natural forests can encourage greater runoff. There is only limited evidence to suggest the extent of forest cover is a significant controlling parameter on the regression equations used to estimate peak flood flows10. However, the OPW guidelines identify commercial afforestation to increase productivity as the significant pressure on rural land use in Ireland. Increased irrigation and drainage for the commercial forests can route more water to the rivers thus reducing the time to peak. The OPW future scenarios guidelines recommend that changes in forest cover can be reflected in a reduced time to peak due to these associated drainage works.
Up to 20% of the Upper Lee catchment is covered by forest as defined by the Flood Studies Update. Forest cover in this area is predicted to increase by 17% by 2035 in line with the Forest Service Strategy (2006). The projected change in forest cover could reduce the time to peak by 17% and 33% for the MRFS and HEFS respectively. However, less than 10% of the Womanagh catchment is covered by woodland or commercial forestry. Therefore, any change in forest cover would have negligible impacts on flows in the lower catchments and has not been considered further.
11.3 Design Future Scenario Conditions
The present day design hydrology (derived in Chapter 5 of this report) was modified to consider the relevant catchment and climate changes discussed in the previous sections. Table 11.3 summarises the final Mid-Range and High-End Future Scenarios.
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Table 11.3: Allowance for Future Condition in Catchment Parameters Ballingeary (Upper Lee Catchment) Womanagh Catchment Catchment Parameter MRFS HEFS MRFS HEFS Flood Flows +20% +30% +20% +30% Mean Sea Level Rise +0.5m +1.0m +0.5m +1.0m Land Movement -0.5mm/year -0.5mm/year -0.5mm/year -0.5mm/year i.e. -0.05m over 100 i.e. -0.05m over 100 i.e. -0.05m over 100 i.e. -0.05m over years years years 100 years Urbanisation 0.95% 1.79% 2.70% 2.96% Forestation Not considered Not considered Not considered Not considered
The design hydrology under future conditions has been adjusted for the predicted change in forest cover in the relevant Upper Lee catchments only where the forest cover is deemed to change significantly over the future decades. The resultant future peak flood flows and future extreme sea levels based on the Mid- Range and High End Future Scenarios are provided in Appendix D.
The predicted increase in river flows and sea level rise attributed to predicted climate change is the most significant factor that influences design peak flows and levels in UoM19. This will increase the frequency of extreme flows and may reduce the standard of protection afforded by any flood risk management scheme going into the future.
Urbanisation has a relatively small impact on design peak flows as Ballingeary, Castlemartyr and Killeagh all remain predominately rural in both the MRFS and HEFS. However, future land management may have a greater impact on sediment load and therefore river channel capacity.
The impact of the future flows on flood extent and hazard will be assessed in the subsequent hydraulic modelling and flood mapping.
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12 Conclusions, Key Findings and Recommendations
12.1 Conclusions and Key Findings
The design flows from this hydrology report inform the inflows to the hydraulic model to assess flood risk from the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1%AEP fluvial and tidal flood events. The key hydrological findings in UoM19 are as follows:
Historic flood events Major fluvial flood events since 1980 were identified in UoM19 at Ballingeary, Castlemartyr and Killeagh. The largest reported event was on 19th November 2009 – 20th November 2009. The 0.63%AEP estimate of the November 2009 event from nearby gauges was not necessarily representative of the event that occurred in Ballingeary due to the variation in rainfall. The model extracted results suggest a 0.1%AEP for this event at Ballingeary. The calibration of the Ballingeary and Womanagh catchment models will be based on the 19th November 2009. Extreme flood events also occurred across the rest of River Lee catchment in August 1986, November 2000, November 2002, December 2006, January 2010, June 2012 as well as March and July 2013. However, there are no reliable records of flooding at the Ballingeary, Castlemartyr or Killeagh for these events. Hence they have not been considered for calibration purposes.
Design flood flows Peak flood flows were derived along the Upper Lee, Bunsheelin River, Kiltha River, Dissour River and Womanagh River within the AFAs for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1%AEP events using the recommended FSU methodology outlined in Work Package 2.2 and 2.3. The design flood hydrograph for ungauged HEPs in the Womanagh catchment were based on the hydrograph pivotal site fitted to the observed median hydrograph at the gauges within the catchment. The design flood hydrograph for Ballingeary was derived using the FSSR16 rainfall-runoff approach calibrated to the November 2009 event for a 43 hour design event to consider the prolonged series of events that results in flooding at this AFA. The joint probability between tributary inflows and the main watercourse was informed by FSU WP3.4. The joint probability was found to be largely dictated by the size of the incoming catchment in UoM19. The % AEP on the Upper Lee was found to be similar to that of the flood event on the Bunsheelin as the catchment areas are of a similar size and contribute similar flows to the downstream reach. The same relationship was found between the Womanagh and Kiltha. Smaller tributaries in the Womanagh catchment were found to be moderately dependent on the flows on the main river and will be investigated further during the modelling phase. The design flood hydrographs will be applied to the hydraulic models as inflows to the upstream of each river reach, tributary inflows and intermediate inflows for the catchment in-between. The outflow for the upstream models in Castlemartyr and Killeagh will form the inflow to the downstream Womanagh model iteratively.
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Design coastal conditions The design extreme sea levels were extracted from the ICPSS for the 50%, 20%, 10%, 5%, 2%, 1%, 0.5% and 0.1%AEP tidal events. ICPSS point S_31 was used to derive the total tide plus surge levels at the Womanagh outfall. The astronomic curve and surge profile were derived from the admiralty predicted astronomic tide and typical duration of surge events in the South West. The final design tidal curve was derived from the combined astronomic tide and design surge profile scaled to meet the design extreme sea levels. Joint probability between the storm surge and river flood was calculated using the DEFRA FD2308 desk-based approach as per GN 20.
Uncertainty and Sensitivity There is significant uncertainty in the duration of flooding and catchment conditions that result in flooding at Ballingeary. The effective duration could vary between 11 and 43 hours at Ballingeary resulting in a 180% variation in volume. A sensitivity test on a shorter 11 hour duration storm event has been proposed to assess flood risk based on a flash flood scenario. The uncertainty of the 1%AEP target peak flow was estimated to range up to +30% in UoM19 ungauged HEPs which will inform the sensitivity tests in the hydraulic modelling. A sensitivity test which raises the total tide plus surge level by 0.5m has been proposed in accordance with GN22.
Hydrogeomorphology The current erosion and deposition processes were assessed for all AFAs and intervening MPWs. The Upper Lee, Bunsheelin and lower Womanagh were all deemed to be depositing sediment over time, raising bed levels. Maintenance of the channel may be required for these reaches. The Kiltha River and Dissour River were deemed to be largely in equilibrium, with only local deposition at the town bridges. Given the supply of vegetation from the wooded headwaters, structures on the Upper Lee, Kiltha and Dissour were judged to be at risk from large woody debris blocking openings during flood events.
Future conditions Two future scenarios were developed to assess potential future changes namely, the Mid-Range Future Scenario (MRFS) and the High End Future Scenario (HEFS). River flows were predicted to increase by 20% and 30% due to climatic changes under MRFS and HEFS respectively. Sea levels were predicted to rise by 0.55m and 1.05m for the MRFS and HEFS respectively, including allowance for 0.5mm/year post-glacial rebound land movements. Urban extent was predicted to increase between 1% and 3% per year for the MRFS and HEFS scenarios, based on the forecasted rates in the South West Regional Authority planning guidelines. Time to peak was predicted to reduce by 17% and 33% for the MRFS and HEFS respectively in the Upper Lee catchment due to change in the forest cover.
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The design peak flood flows and total tide plus surge levels were adjusted to represent the climatic and catchment changes above for the MRFS and HEFS future scenarios accordingly.
12.2 Recommendations
The following recommendations can be drawn from the key findings above for the subsequent hydraulic modelling, flood risk assessment, preliminary option development and FRMP:
The design peak flows and design total tide plus surge levels presented in Table 7.1 and 7.2 should be used to inform the subsequent hydraulic modelling in UoM19. Inflows for intervening catchments should be distributed across minor watercourses and overland flow paths identified from the survey based on the proportional increase in contributing area. The joint probability approach and analysis in Chapter 11 should be used to inform the combinations of inflows and coastal conditions for the model boundaries. The relevant hydraulic models should be calibrated as far as possible to the following historic flood event: 19th November 2009 – extreme fluvial event at Ballingeary and the Womanagh catchment (including Castlemartyr and Killeagh). The following sensitivity tests should be considered to assess the impact of hydrological assumptions on flood extent and levels in the subsequent hydraulic modelling: Peak flow for all models. Duration of flood event at Ballingeary. Downstream tide plus surge levels for the Womanagh. The flows and resultant flood risk at Ballingeary should be interpreted carefully considering the preceding conditions in Lough Allua for any proposed mitigation measures. The sediment load and rate of deposition at Ballingeary should be considered in the maintenance of any flood mitigation measures in this AFA. The presence of woody debris should be considered in the design and assessment of any flood mitigation measures on the Upper Lee, Kiltha and Dissour rivers.
The following recommendations can be drawn from the hydrological analysis for future analysis in the catchment: The installation of long-term water level and flow gauges along the watercourses in Ballingeary, combined with water level gauges in Lough Allua. This observed data would enable verification of the rainfall-runoff modelling and the exact conditions that lead to flooding at Ballingeary. In the immediate future, concurrent level monitoring in Ballingeary and along Lough Allua during a prolonged flood event would provide useful verification and calibration information. Flow gaugings and the reinstatement of the Castlemartyr river level gauge may be beneficial to develop improved flow estimates on the Kiltha (subject to the findings of the flood mapping and flood risk assessment exercise). The %AEP estimates for total tide plus surge levels should be reviewed periodically at Ballycotton as a longer period of data becomes available.
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Glossary
AEP Annual Exceedance Probability; this represents the probability of an event being exceeded in any one year and is an alternative method of defining flood probability to ‘return periods’. The 10%, 1% and 0.1% AEP events are equivalent to 10-year, 100-year and 1000-year return period events respectively. AFA Area for Further Assessment – Areas where, based on the Preliminary Flood Risk Assessment and the CFRAM Study Flood Risk Review, the risks associated with flooding are potentially significant, and where further, more detailed assessment is required to determine the degree of flood risk, and develop measures to manage and reduce the flood risk. AMAX Annual Maximum Flood BFISOILS Baseflow index from Irish Geological Soils dataset. Often used as a permeability indicator. CFRAM Catchment Flood Risk Assessment and Management – The ‘CFRAM’ Studies will develop more detailed flood mapping and measures to manage and reduce the flood risk for the AFAs. DAD Defence Asset Database DAS Defence Asset Survey EU European Union EPA Environmental Protection Agency FARL Index of flood attenuation due to reservoirs and lakes FRMP Flood Risk Management Plan. This is the final output of the CFRAM study. It will contain measures to mitigate flood risk in the AFAs. FRR Flood Risk Review – an appraisal of the output from the PFRA involving onsite verification of the predictive flood extent mapping, the receptors and historic information. FSU (WP) Flood Studies Update (Work Package) (2008 to 2011) FSR Flood Studies Report (HR Wallingford, 1975) GIS Geographical Information Systems HA Hydrometric Area. Ireland is divided up into 40 Hydrometric Areas. HEFS High-End Future Scenario to assess climate and catchment changes over the next 100 years assuming high emission predictions from the International Panel on Climate Change. HEP Hydrological Estimation Point HPW High Priority Watercourse. A watercourse within an AFA. ICPSS Irish Coastal Protection Strategy Study (2012) ICWWS Irish Coastal Water Level and Wave Study (2013) ING Irish National Grid system, Ordnance Survey of Ireland
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MPW Medium Priority Watercourse. A watercourse between AFAs, and between an AFA and the sea. MRFS Mid-Range Future Scenario to assess climate and catchment changes over the next 100 years assuming medium emission predictions from the International Panel on Climate Change. ODM Ordnance Datum Malin. The current geodetic datum of Irish National Grid which references the mean sea level at Malin Head between 1960 and 1969. OPW Office of Public Works, Ireland OSi Ordnance Survey Ireland PFRA Preliminary Flood Risk Assessment – A national screening exercise, based on available and readily-derivable information, to identify areas where there may be a significant risk associated with flooding. QMED Median annual flood used as the index flood in the Flood Studies Update. The QMED flood has an approximate 50%AEP.
QMEDamax QMED derived from the annual maximum series at a gauged location
QMEDrural QMED derived from physical catchment descriptors according to the Flood Studies Update methodology.
QMEDadj QMED adjusted by the ratio of QMEDamax:QMEDrural at a hydrologically similar Pivotal site.
QMEDurban QMED adjusted to account for the impacts of urban areas according to the Flood Studies Update methodology. S1085 Typical slope of the river reach between 10%ile and 85%ile along its length. SAAR Standard average annual rainfall 1961 to 1990 SEA Strategic Environmental Assessment. A high level assessment of the potential of the FRMPs to have an impact on the Environment within a UoM. SW CFRAM South Western Catchment Flood Risk Assessment and Management study Total tide plus surge level Total tidal level formed of the astronomic tide and storm surge elements. UoM Unit of Management. The divisions into which the RBD is split in order to study flood risk. In this case a HA. WFD Water Framework Directive. A European Directive for the protection of water bodies that aims to, prevent further deterioration of our waters, to enhance the quality of our waters, to promote sustainable water use, and to reduce chemical pollution of our waters.
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South Western CFRAM Study
Final Hydrology Appendices, Unit of Management 19 June 2016
The Office of Public Works
South Western CFRAM Study
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The Office of Public Works
Trim Co. Meath
Mott MacDonald, 5 Eastgate Avenue, Eastgate, Little Island, Cork, Ireland
T +353 (0)21 4809 800 F +353 (0)21 4809 801 W www.mottmac.com South Western CFRAM Study Final Hydrology Appendices, Unit of Management 19
Issue and revision record
Revision Date Originator Checker Approver Description Standard A September 2013 M Piggott R Gamble R Gamble Draft C Jones S Pipe
B January 2014 M Piggott R Gamble R Gamble Draft Final
This document is issued for the party which commissioned it and We accept no responsibility for the consequences of this for specific purposes connected with the above-captioned project document being relied upon by any other party, or being used only. It should not be relied upon by any other party or used for for any other purpose, or containing any error or omission any other purpose. which is due to an error or omission in data supplied to us by other parties.
This document contains confidential information and proprietary intellectual property. It should not be shown to other parties without consent from us and from the party which commissioned it..
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Appendices
Appendix A. Available Data ______2 Appendix B. Hydrological Estimation Points ______7 Appendix C. Design Hydrology ______15 Appendix D. Future Peak Flows and Levels ______36
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Appendix A. Available Data
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Table A.1: Selected Hydrometric Data
Years Fit for Calibration Fit for Statistical Station Name River Name Type Easting Northing Record Start Data Owner Comments Purposes? Analysis? 19003 Castlemartyr Kiltha River Level 196196 72804 23/12/1976 17 EPA No flow available, few missing periods otherwise good quality data. No No Data only available up to 1993 and does not cover recent calibration events. Potential site for future monitoring if AFA is shown to be at risk from regular flooding. 19019 Dower Dower River Level 198183 72846 14/04/2010 2 EPA Short record with no flow available, significant missing periods and No No capping 19020 Ballyedmond Owennacurra River Flow 185923 76618 15/06/1977 36 EPA Water level and flow gauge with long data series. Detailed 15 minute Yes Yes and Level interval data available after 1996.Gauge located within steep narrow valley and rating curve convergent indicates that high flows are reliable. 19031 Macroom Sullane River Flow 134743 73133 23/06/1983 26 ESB There are several AMAX years missing and ratings curve is suspect for No Not Required and Level the current site. A rating review using the latest flood evidence should be undertaken before this gauge can be used. 19014 Dromcarra Lee River Flow 129670 67519 31/12/1946 63 ESB Reasonable record of extreme events since 1946. Higher FARL value Yes to inform Not Required and Level as it is located downstream of the Loughs but suitable for QMED relative magnitude transfer. only 19039 Ballingeary/Kilmore Bunsheelin Spot 115137 67415 13/05/1991 18 EPA Low flow measurements/spot gaugings only (3 to 5 per year) No No gaugings No multiple flow measurements for any event 19043 Inchigeelagh Lee Spot 122352 65782 22/08/1991 9 EPA Low flow measurements/spot gaugings only (3 to 5 per year) No No gaugings No multiple flow measurements for any event 19068 Ballycotton Sea Sea Level 199948 63930 22/02/2007 2-5 OPW Short sea level record at 10 minute intervals of reasonable quality. Yes No Covers calibration events 952 Roches Point N/A Hourly 183100 60100 01/12/1955 57 Met Hourly rainfall record of good quality and concurrent daily SMD Yes Not Required Rainfall Eireann observations since 1979 covers calibration events and Soil Moisture Deficit 955 Cork Airport N/A Hourly 166500 66200 01/01/1962 51 Met Hourly rainfall record of good quality and concurrent daily SMD Yes Not Required Rainfall Eireann observations since 1979 covers calibration events and Soil Moisture Deficit 4902 Dunmanway (Demesne) Dunmanway 15 Minute 123700 53600 2011 1 OPW Short good quality consistent record which provides detailed rainfall Yes for calibration Not Required Rainfall data and profiles for recent events since July 2011. events since 2011 2104 Castlemartyr G.S. Kiltha Daily 196100 73200 1998 14 Met Data quality reasonable and covers periods of calibration events. Yes Not Required Rainfall Eireann 1804 Tarleton Lee Daily 132300 65800 1942 49 Met Short gaps in data present. 1986 missing. Slight trending in annual No, doesn’t cover Not Required Rainfall Eireann rainfall total since 1975. specified events Does not cover most recent flood events 3004 Ballingeary Voc. Sch. Lee Daily 163200 62800 28/10/1948 61 Met Short data gaps in 1950 and 1983 no indication of trending in annual Yes Not Required rainfall Eireann rainfall but annual maximum rainfall in a 24 hour period has increased since 1996 indicating a climatic trend towards more intense storms 4404 Ballymacoda (Mount Cotton) Womanagh Daily 205500 69900 01/01/1976 33 Met Consistent data record with a short data gap in October 1999. Covers Yes Not Required rainfall Eireann calibration events 4904 Killeagh ( Monabraher) Dissour Daily 215840 75910 01/01/1976 33 Met Data gaps prior to 1996 limit data quality. However, there is a Yes Not Required rainfall Eireann consistent data record after 1996. Covers calibration events 5004 Shanagarry (North) Ballycotton Bay Daily 215135 80205 01/01/1976 33 Met Data gaps prior to 1999 limit data quality. However, there is a Yes Not Required rainfall Eireann consistent data record after 1999. Covers calibration events 6204 BallincurrigG.S. Owencurra Daily 220036 81159 01/08/1995 14 Met Consistent data set for entire period with no indications of trending. Yes Not Required rainfall Eireann Covers calibration events 6704 Castlemartyr (Killamucky) Kiltha Daily 195300 73900 01/12/2000 4 Met Continuous rainfall record with obvious anomalies. Data record too No Not Required rainfall Eireann short to assess trending. Does not cover calibration events
The following figures have classified river flow and level gauge data into these categories: Missing Data is missing, erroneous or of unacceptable quality for use (e.g. equipment error or readings during drainage works).
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Suspect Data may contain a significant degree of error due to extrapolation using a poor rating curve or extrapolated beyond reliable data range as identified by OPW or EPA. Alternatively data that has been derived from incomplete records. Fair Data derived from a corrected water level series or a fair rating curve as identified by OPW or EPA.
Good Data has been inspected and is deemed consistent and without significant error as identified be OPW and EPA.
Unchecked Unchecked data – Data is provisional only and must be used with caution. Frequently applies to most recent data.
Figure A.1: Water Level Data Quality Plot for Kiltha @ Castlemartyr Gauge (EPA - 19003)
Where: Red is missing, Orange is suspect, Yellow is Edited, Green is good and Grey is unchecked based on OPW and EPA data quality flags.
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Figure A.2: Water Level Quality Plot for Dower @ Dower Gauge ( EPA – 19019)
Where: Red is missing, Orange is suspect, Yellow is Edited, Green is good and Grey is unchecked based on OPW and EPA data quality flags.
Figure A.3: Flow Quality Plot for Owencurra @ Ballyedmond Gauge (EPA – 19020)
Where: Red is missing, Orange is suspect, Yellow is Edited, Green is good and Grey is unchecked based on OPW and EPA data quality flags.
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Appendix B. Hydrological Estimation Points
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Table B.1: Ballingeary AFA Physical Catchment Descriptors
LOCATION HEP
DTM_AREA MSL NETLEN STMFQ DRAIND S1085 ARTDRAIN2 FARL SAAR FORMWET URBEXT PEAT ALLUV FOREST PASTURE BFISOILS Bunsheelin at 19_1755_1 16.5 5.105 28.2100 57 1.712 27.638 0 1.000 2142 0.67 0.00 36.9 2.02 6.29 45.05 0.55 Ballingeary upstream Bunsheelin at 19_1971_2 17.5 6.366 30.202 59 1.729 26.350 0 1.000 2155 0.67 0.00 38.4 2.23 6 44.37 0.55 Ballingeary Town Bunsheelin at Lee 19_927_2 19.8 7.132 31.141 63 1.570 25.280 0 0.995 2181 0.67 0.00 38.02 2.38 7.78 45.34 0.49 Confluence Upper Lee upstream 19_928_2 33.7 11.057 69.488 137 2.062 10.809 0 0.950 2312 0.67 0.00 63.07 3.51 21.86 18.32 0.45 Lee at downstream of 19_925_1 53.8 11.057 100.629 201 1.870 10.809 0 0.967 2264 0.67 0.00 53.72 3.15 16.56 28.49 0.42 Bunsheelin/Lee Conf. Upper Lee at upstream 19_1714_2 54.2 11.875 104.334 203 3.089 10.111 0 0.947 2265 0.67 0.00 53.39 3.39 16.43 28.91 0.42 of Lough Allua Inchgeelagh 19_1423_3 115.4 19.966 194.434 363 363 5.583 0 0.845 2202 0.67 0.00 44.27 3.17 22.16 30.78 0.45 downstream of Lough Allua
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Map B.1: Ballingeary HEPs
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Table B.2: Castlemartyr AFA Physical Catchment Descriptors
LOCATION HEP
DTM_AREA MSL NETLEN STMFQ DRAIND S1085 ARTDRAIN2 FARL SAAR FORMWET URBEXT PEAT ALLUV FOREST PASTURE BFISOILS Kiltha upstream 19_1909_9 20.8 12.8 20.7 13 1 9 0 1.000 1210 0.620 0.00 0.00 1.39 17.18 87.68 0.67 Kiltha at Castlemartyr 19_1909_15 28.7 15.8 23.7 13 1 8 0 1.000 1175 0.620 0.96 0.00 4.30 15.14 88.44 0.67 Kiltha at Womanagh Confluence 19_1909_17 29.3 16.8 24.8 13 1 8 0 1.000 1172 0.620 0.94 0.00 4.21 15.96 87.66 0.67 Womanagh upstream of the Kiltha 19_1266_7 14.4 6.6 10.5 5 1 1 0 1.000 1024 0.620 0.00 0.00 7.14 5.37 98.41 0.67 Womanagh downstream of the Kiltha 19_705_1 43.8 16.8 35.3 19 1 8 0 1.000 1123 0.620 0.63 0.00 5.18 12.48 91.19 0.67
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Map B.2: Castlemartyr HEPs
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Table B.3: Killeagh AFA Physical Catchment Descriptors
LOCATION HEP
DTM_AREA MSL NETLEN STMFQ DRAIND S1085 ARTDRAIN2 FARL SAAR FORMWET URBEXT PEAT ALLUV FOREST PASTURE BFISOILS Dissour Upstream 19_686_12 29.1 10.9 24.4 17.0 0.8 12.3 0.00 1.00 1229 0.61 0.00 0.00 0.17 19.82 81.30 0.68 Dissour at Killeagh 19_686_15 30.0 12.4 25.9 17.0 0.9 11.0 0.00 1.00 1226 0.61 0.00 0.00 0.16 19.61 81.53 0.68 Dissour at Womanagh Confluence 19_1798_3 41.9 14.6 39.9 25.0 1.0 10.1 0.00 1.000 1206 0.61 0.000 0.00 0.64 14.66 86.79 0.68
Map B.3: Killeagh HEPs
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Table B.4: Womanagh MPW Physical Catchment Descriptors
LOCATION HEP
DTM_AREA MSL NETLEN STMFQ DRAIND S1085 ARTDRAIN2 FARL SAAR FORMWET URBEXT PEAT ALLUV FOREST PASTURE BFISOILS Womanagh upstream of the Kiltha 19_1266_7 14.4 6.6 10.5 5 1 1 0 1.000 1024 0.620 0.000 0 7.140 5.37 98.41 0.67 Kiltha at Womanagh Confluence 19_1909_17 29.3 16.8 24.8 13 1 8 0 1.000 1172 0.620 0.940 0 4.210 15.96 87.66 0.67 Womanagh downstream of the Kiltha 19_705_1 43.8 16.8 35.3 19 1 8 0 1.000 1123 0.620 0.630 0 5.180 12.48 91.19 0.67
Womanagh upstream Ladysbridge 19_705_2 45.6 17.4 35.8 19.0 0.8 7.3 0.00 1.000 1120 0.62 0.610 0.00 5.05 12.20 91.41 0.67 Ladysbridge 19_1823_1+ 2.6 17.4 2.1 2.0 0.8 7.3 0.00 1.000 1119 0.620 0.604 0.00 5.00 12.08 91.50 0.67 Womanagh downstream of Ladysbridge 19_1823_1 50.7 17.4 37.9 21.0 0.7 7.3 0.00 1.000 1110 0.62 0.550 0.00 4.53 10.98 92.29 0.67 Womanagh upstream Dower 19_1823_5 53.0 19.0 39.6 21.0 0.7 7.0 0.00 1.000 1106 0.62 0.520 0.00 4.52 10.52 92.18 0.67 Dower upstream Womanagh 19_1824_19 13.3 8.7 8.7 1.0 0.7 14.1 0.00 1.000 1139 0.61 0.000 0.00 0.26 7.37 96.81 0.71 Womanagh downstream of the Dower 19_1833_1 66.3 19.0 48.3 23.0 0.7 7.0 0.00 1.000 1113 0.62 0.420 0.00 3.67 9.88 93.11 0.67 Womanagh upstream Ballying 19_1628_2 78.2 23.7 60.6 31.0 0.8 5.3 0.00 1.000 1102 0.62 0.350 0.00 4.29 8.54 94.13 0.67 Ballying upstream Womanagh 19_1247_10 10.2 5.8 6.6 3.0 0.6 2.2 0.00 1.000 1116 0.61 0.000 0.00 0.09 1.11 99.94 0.45 Womanagh downstream Ballying 19_1793_1 88.4 23.7 67.2 35.0 0.8 5.3 0.00 1.000 1103 0.62 0.310 0.00 3.80 7.68 94.80 0.68 Womanagh upstream Dissour 19_1793_2 88.7 24.2 67.7 35.0 0.8 5.3 0.00 1.000 1103 0.62 0.310 0.00 3.86 7.66 94.81 0.68 Womanagh tidal outfall 19_1941_2+ 138.0 30.1 117.7 64.0 0.9 5.2 0.00 1.000 1135 0.61 0.204 0.00 2.89 9.39 92.66 0.67
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Map B.4: Womanagh HEPs
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Appendix C. Design Hydrology
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C.1 Ballingeary AFA
Figure C.1: Ballingeary AFA Schematic of QMED Bunsheelin 19_1755_1 15.2 m3/s
19_1971_2 16.2 m3/s Ballingeary
19_927_2 Inchgeelagh 19.3 m3/s
19_928_2 19_925_1 19_1714_2 19_869_1 Lee 3 3 3 Lough Allua 26.6 m /s 43.1 m /s 48.5 m /s 50.7 m3/s
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Table C.1: Bunsheelin Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordancy record FSU HGF/ No. Length Count (Di) length FARL URBEXT FLATWET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 10004 14 14 1.713 14 0.986 0.000 0.54 25.037 30.57 0.517 1700 B Locally Important Aquifer 0.705 N/A 30001 18 32 0.822 36 0.935 0.000 0.70 5.168 121.02 0.436 1787 A2 Locally Important Aquifer 1.022 N/A 20006 35 67 0.194 105 1.000 0.000 0.67 6.390 77.55 0.600 1463 B Locally Important Aquifer 0.574 N/A 16013 33 100 0.125 132 0.993 0.000 0.58 24.556 93.58 0.531 1471 B Poor Aquifer 0.488 N/A 35002 34 134 0.155 170 0.986 0.000 0.72 13.263 88.82 0.523 1381 A2 Poor Aquifer 0.792 N/A 25158 18 152 0.524 108 1.000 0.000 0.59 6.973 109.55 0.514 1377 A1 Locally Important Aquifer 1.364 N/A 10002 46 198 0.375 322 0.932 0.170 0.54 6.899 230.89 0.516 1530 B Locally Important Aquifer 0.721 Including large areas of Poor Aquifer strata. 6030 27 225 0.542 216 0.972 0.000 0.61 20.091 10.40 0.625 1157 B Poor Aquifer 0.701 N/A 20002 37 262 0.614 333 0.987 0.810 0.67 2.087 423.74 0.592 1669 B Locally Important Aquifer 0.484 N/A 22006 57 319 0.038 570 0.961 0.540 0.66 9.421 328.81 0.414 1819 B Locally Important Aquifer 0.625 Only minor Karstic coverage, vast majority is of locally important aquifer. 36021 27 346 0.089 297 0.995 0.000 0.69 19.110 23.41 0.330 1570 A2 Poor Aquifer 0.749 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. 25038 17 363 0.046 204 1.000 0.210 0.59 7.336 136.10 0.591 1249 B Locally Important Aquifer 0.725 N/A 25044 40 403 0.043 520 0.997 0.000 0.59 2.666 92.55 0.575 1187 A2 Locally Important Aquifer 1.256 N/A 39001 31 434 0.163 434 0.987 0.000 0.70 12.506 50.71 0.320 1764 B Poor Aquifer 0.818 N/A 32011 25 459 0.094 375 0.986 0.150 0.69 13.428 70.10 0.337 1613 B Poor Aquifer 0.689 N/A 16005 30 489 0.087 480 1.000 0.330 0.59 6.524 84.00 0.542 1154 A2 Locally Important Aquifer 1.071 N/A 34009 33 522 0.039 561 1.000 1.070 0.73 3.325 117.11 0.443 1257 A2 Locally Important Aquifer 1.309 N/A
Figure C.2: Pooled Flood Growth Curve Figure C.3: L Moment Plot 3.5 0.7
0.6 3 0.5 2.5 0.4 EV1 0.3 2 LO
LN2 0.2
CV - 1.5 GEV L 0.1
GLO Flood Growth Factor Growth Flood LN3 0.0 1 %AEP -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 50% 20% 10% 5% 2% 1% 0.5% 0.1% -0.1 0.5 -0.2
-0.3 0 L-Skewness 0 1 2 3 4 5 6 7 8 Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 Fitted Trendline
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Table C.2 Upper Lee Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordancy record FSU HGF/ No. Length Count (Di) length FARL URBEXT FLATWET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 19014 47 47 0.313 47 0.892 0.000 0.67 3.462 170.76 0.426 2071 ESB stn Poor Aquifer 0.801 N/A 10004 14 61 1.787 28 0.986 0.000 0.54 25.037 30.57 0.517 1700 B Locally Important Aquifer 0.705 N/A 30001 18 79 0.858 54 0.935 0.000 0.70 5.168 121.02 0.436 1787 A2 Locally Important Aquifer 1.022 N/A 39001 31 110 0.170 124 0.987 0.000 0.70 12.506 50.71 0.320 1764 B Poor Aquifer 0.818 N/A 22006 57 167 0.040 285 0.961 0.540 0.66 9.421 328.81 0.414 1819 B Locally Important Aquifer 0.625 Only minor Karstic coverage, vast majority is of locally important aquifer. 32011 25 192 0.098 150 0.986 0.150 0.69 13.428 70.10 0.337 1613 B Poor Aquifer 0.689 N/A 16013 33 225 0.130 231 0.993 0.000 0.58 24.556 93.58 0.531 1471 B Poor Aquifer 0.488 N/A 36021 27 252 0.093 216 0.995 0.000 0.69 19.110 23.41 0.330 1570 A2 Poor Aquifer 0.749 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. 34007 53 305 0.052 477 0.978 0.000 0.73 4.569 151.71 0.349 1590 B Poor Aquifer 0.489 Mix. Majority of region is of Poor quality aquifer. Gauge sits on Karstic zone. 38001 33 338 0.127 330 0.922 0.290 0.70 5.950 111.25 0.313 1753 B Poor Aquifer 0.292 N/A 35002 34 372 0.162 374 0.986 0.000 0.72 13.263 88.82 0.523 1381 A2 Poor Aquifer 0.792 N/A 10002 46 418 0.392 552 0.932 0.170 0.54 6.899 230.89 0.516 1530 B Locally Important Aquifer 0.721 Including large areas of Poor Aquifer strata. 25158 18 436 0.547 234 1.000 0.000 0.59 6.973 109.55 0.514 1377 A1 Locally Important Aquifer 1.364 N/A 20006 35 471 0.202 490 1.000 0.000 0.67 6.390 77.55 0.600 1463 B Locally Important Aquifer 0.574 N/A 18016 20 491 0.258 300 1.000 0.780 0.64 4.884 116.73 0.348 1441 B Locally Important Aquifer 0.804 N/A 1041 32 523 0.103 512 1.000 0.860 0.69 7.227 116.18 0.379 1329 B Locally Important Aquifer 0.424 N/A
Figure C.4: Pooled Flood Growth Curve Figure C.5: L Moment Plot 3.5
0.7 3 0.6
2.5 0.5
EV1 0.4 LO 2 LN2 0.3
GEV CV
- 0.2 L 1.5 GLO 0.1 Flood Growth Factor Growth Flood LN3 1 %AEP 0.0 50% 20% 10% 5% 2% 1% 0.5% 0.1% Lee CFRAM Catchment Average -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 -0.1 0.5 -0.2
-0.3 0 L-Skewness 0 1 2 3 4 5 6 7 8 Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 Fitted Trendline
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Table C.3 Lough Allua/Lee Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordancy record FSU HGF/ No. Length Count (Di) length FARL URBEXT FLATWET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 19014 47 47 0.226 47 0.892 0.000 0.67 3.462 170.76 0.426 2071 ESB stn Poor Aquifer 0.801 N/A 30001 18 65 0.619 36 0.935 0.000 0.70 5.168 121.02 0.436 1787 A2 Locally Important Aquifer 1.022 N/A 10004 14 79 1.289 42 0.986 0.000 0.54 25.037 30.57 0.517 1700 B Locally Important Aquifer 0.705 N/A 22006 57 136 0.029 228 0.961 0.540 0.66 9.421 328.81 0.414 1819 B Locally Important Aquifer 0.625 Only minor Karstic coverage, vast majority is of locally important aquifer. 39001 31 167 0.123 155 0.987 0.000 0.70 12.506 50.71 0.320 1764 B Poor Aquifer 0.818 N/A 32011 25 192 0.071 150 0.986 0.150 0.69 13.428 70.10 0.337 1613 B Poor Aquifer 0.689 N/A 38001 33 225 0.092 231 0.922 0.290 0.70 5.950 111.25 0.313 1753 B Poor Aquifer 0.292 N/A 34007 53 278 0.038 424 0.978 0.000 0.73 4.569 151.71 0.349 1590 B Poor Aquifer 0.489 Mix. Majority of region is of Poor quality aquifer. Gauge sits on Karstic zone. 36021 27 305 0.067 243 0.995 0.000 0.69 19.110 23.41 0.330 1570 A2 Poor Aquifer 0.749 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. 16013 33 338 0.094 330 0.993 0.000 0.58 24.556 93.58 0.531 1471 B Poor Aquifer 0.488 N/A 18016 20 358 0.186 220 1.000 0.780 0.64 4.884 116.73 0.348 1441 B Locally Important Aquifer 0.804 N/A 10002 46 404 0.282 552 0.932 0.170 0.54 6.899 230.89 0.516 1530 B Locally Important Aquifer 0.721 Including large areas of Poor Aquifer strata. 35002 34 438 0.117 442 0.986 0.000 0.72 13.263 88.82 0.523 1381 A2 Poor Aquifer 0.792 N/A 25158 18 456 0.394 252 1.000 0.000 0.59 6.973 109.55 0.514 1377 A1 Locally Important Aquifer 1.364 N/A 1041 32 488 0.075 480 1.000 0.860 0.69 7.227 116.18 0.379 1329 B Locally Important Aquifer 0.424 N/A 28001 17 505 1.632 272 0.938 0.050 0.62 2.199 169.42 0.329 1423 B Locally Important Aquifer 0.608 N/A
Figure C.6: Pooled Flood Growth Curve Figure C.7: L Moment Plot 3.5
0.6 3 0.5
2.5 EV1 0.4 LO 2 LN2 0.3
GEV Kurtosis
1.5 - 0.2 GLO L
Flood Growth Factor Growth Flood LN3 0.1 1 %AEP 50% 20% 10% 5% 2% 1% 0.5% 0.1% Lee CFRAM Catchment Average 0.0 0.5 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 -0.1 L-Skewness 0 Series1 Pooled L-Moments LO 0 1 2 3 4 5 6 7 8 LN2 EV1 GEV Logistic Reduced Variable GLO LN3 polynomial Fitted Trendline
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Figure C.8: FSSR16 Rainfall- Runoff Hydrograph For Upper Lee Figure C.9: FSSR16 Rainfall- Runoff Hydrograph For Bunsheelin 120 50
45 100 40
35 80 30
60 25 Flow (m3/s) Flow Flow (m3/s) Flow 20 40 15
10 20 5
0 0 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 Time (Hours) Time (Hours)
Calibrated Rainfall-Runoff (Duration 58 hours, PR 93%, CWI 130, Tp factor 1.33) Calibrated Rainfall-Runoff (Duration 58 hours, PR 93%, CWI 130, Tp factor 1.33)
Table C.4: Ballingeary AFA Design Peak Flows 95% Pivotal AREA0.777/ Confidence LOCATION HEP Site QMED QMED Check Limit Flood Growth Curve Flood Growth Factor Design Peak Flows (m3/s) Hydrograph 50 20 10 5 2 1 0.5 0.1 50 20 10 5 2 1 0.5 0.1 Bunsheelin at Ballingeary 19_1755_1 20006 15.2 18 28.6 GLO 1.00 1.24 1.42 1.60 1.87 2.11 2.38 3.15 15.2 18.9 21.6 24.4 28.6 32.2 36.2 48.0 FSR upstream Rainfall- Runoff Bunsheelin at Ballingeary 19_1971_2 20006 16.2 18 30.4 GLO 1.00 1.24 1.42 1.60 1.87 2.11 2.38 3.15 16.2 20.1 22.9 25.9 30.3 34.2 38.5 50.9 FSR Town Rainfall- Runoff Bunsheelin at Lee Confluence 19_927_2 20006 19.3 19 36.2 GLO 1.00 1.24 1.42 1.60 1.87 2.11 2.38 3.15 19.3 24.0 27.3 30.9 36.2 40.7 45.9 60.8 FSR Rainfall- Runoff Upper Lee upstream 19_928_2 19014 26.6 18 50.0 GLO 1.00 1.24 1.42 1.60 1.87 2.11 2.38 3.15 26.6 33.3 38.0 43.1 50.5 57.0 64.3 85.4 FSR Rainfall- Runoff Lee at downstream of 19_925_1 19014 43.1 20 80.9 GLO 1.00 1.25 1.43 1.62 1.90 2.14 2.41 3.20 43.1 53.8 61.5 69.6 81.7 92.2 104.0 138.0 FSR Bunsheelin/Lee Conf. Rainfall- Runoff Upper Lee at Lough Allua 19_1714_2 19014 48.5 22 91.1 GLO 1.00 1.25 1.44 1.63 1.92 2.17 2.45 3.26 48.5 60.9 69.8 79.2 93.2 105.3 119.0 158.2 FSR Rainfall- Runoff Inchgeelagh downstream of 19_1432_3 19014 50.7 13 95.1 GLO 1.00 1.25 1.44 1.63 1.92 2.17 2.45 3.26 50.7 63.6 72.9 82.7 97.3 109.9 124.2 165.2 FSR Lough Allua Rainfall- Runoff
Area and other catchment descriptors for the HEP have been provided in Appendix B: Area and other catchment descriptors for the pivotal site have been included in the earlier tables in Appendix C for each AFA.
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C.2 Castlemartyr AFA
Figure C.10: Castlemartyr AFA Schematic of QMED River Kiltha
19_1909_11 7.0 m3/s
19_1909_15 8.5 m3/s
19_1909_17 8.6 m3/s Womanagh 19_1266_7 19_705_1 Womanagh River 3.0 m3/s 11.6m3/s River
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Table C.5: Kiltha Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordancy record FSU HGF/ No. Length Count (Di) length FARL URBEXT FLATWET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 30020 16 16 0.069 16 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important Aquifer - 0.882 N/A Karstified (conduit) 19020 28 44 0.303 56 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 13002 19 63 0.035 57 1.000 0.000 0.56 4.953 62.96 0.657 1044 B Poor Aquifer 0.645 N/A 36071 20 83 0.591 80 0.823 0.000 0.70 13.640 68.03 0.644 1315 B Regionally Important Aquifer - 0.939 Mix of geology. Majority Karstic. Karstified (conduit) 6030 27 110 0.764 135 0.972 0.000 0.61 20.091 10.40 0.625 1157 B Poor Aquifer 0.701 N/A 26058 24 134 0.322 144 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 16006 33 167 0.294 231 0.994 0.000 0.59 5.763 75.80 0.591 1116 B Locally Important Aquifer 0.562 Gauge within Karstic zone. But this makes up only a very small fraction of the catchment. 25040 19 186 0.118 152 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 24022 20 206 0.074 180 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 25034 26 232 0.736 260 1.000 0.000 0.65 2.572 10.77 0.698 969 A2 Locally Important Aquifer 1.182 N/A 19016 15 247 1.292 165 1.000 0.070 0.66 4.554 117.82 0.687 1267 ESB stn Locally Important Aquifer 1.001 Gauge seated on Karstic area. 40% Karstic. 25044 40 287 0.061 480 0.997 0.000 0.59 2.666 92.55 0.575 1187 A2 Locally Important Aquifer 1.256 N/A 29004 32 319 0.132 416 0.993 1.310 0.65 2.517 121.44 0.631 1107 A2 Regionally Important Aquifer - 0.903 N/A Karstified (conduit) 26018 49 368 0.046 686 0.756 0.340 0.69 0.553 119.48 0.649 1044 A2 Regionally Important Aquifer - 1.006 N/A Karstified (conduit) 26010 35 403 0.077 525 0.937 0.000 0.69 1.906 94.53 0.578 1064 B Locally Important Aquifer 0.919 N/A 30021 26 429 0.285 416 0.994 0.160 0.72 0.848 103.63 0.573 1168 B Regionally Important Aquifer - 0.328 N/A Karstified (conduit) 16051 13 442 0.631 221 1.000 0.000 0.58 1.615 34.19 0.593 895 B Locally Important Aquifer 0.945 N/A
Figure C.11: Pooled Flood Growth Curve Figure C.12: L Moment Plot 3.5
0.7 3 0.6
2.5 0.5 EV1 0.4 LO 2
LN2 0.3 CV
GEV - 0.2 1.5 L GLO 0.1
Flood Growth Factor Growth Flood LN3 1 %AEP 0.0 50% 20% 10% 5% 2% 1% 0.5% 0.1% -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 Lee CFRAMS Catchment Average -0.1 0.5 -0.2
0 -0.3 L-Skewness 0 1 2 3 4 5 6 7 8 Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 Fitted Trendline
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Table C.6 Upper Womanagh Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordancy record FLAT FSU HGF/ No. Length Count (Di) length FARL URBEXT WET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 25034 26 26 0.463 26 1.000 0.000 0.65 2.572 10.77 0.698 969 A2 Locally Important Aquifer 1.182 N/A 6030 27 53 0.481 54 0.972 0.000 0.61 20.091 10.40 0.625 1157 B Poor Aquifer 0.701 N/A 30020 16 69 0.043 48 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important Aquifer 0.882 N/A - Karstified (conduit) 25040 19 88 0.074 76 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 10022 17 105 0.136 85 1.000 29.720 0.54 11.166 12.94 0.660 822 A1 Poor Aquifer 1.527 N/A 24022 20 125 0.047 120 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 16051 13 138 0.398 91 1.000 0.000 0.58 1.615 34.19 0.593 895 B Locally Important Aquifer 0.945 N/A 26058 24 162 0.203 192 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 13002 19 181 0.022 171 1.000 0.000 0.56 4.953 62.96 0.657 1044 B Poor Aquifer 0.645 N/A 10021 24 205 0.121 240 0.997 24.210 0.54 11.851 32.51 0.646 799 A1 Locally Important Aquifer 1.875 N/A 26022 33 238 0.107 363 1.000 0.560 0.67 3.445 61.88 0.598 916 A2 Locally Important Aquifer 1.091 Small catchment, gauge situated within Karstic zone (lower reaches). Upper is aquifer. Caution 6031 18 256 0.784 216 1.000 1.540 0.63 8.102 46.17 0.552 931 A2 Poor Aquifer 1.049 N/A 19020 28 284 0.191 364 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 8002 21 305 0.144 294 1.000 0.540 0.56 3.488 33.43 0.579 791 A1 Locally Important Aquifer 0.765 N/A 16006 33 338 0.185 495 0.994 0.000 0.59 5.763 75.80 0.591 1116 B Locally Important Aquifer 0.562 Gauge within Karstic zone. But this makes up only a very small fraction of the catchment. 9002 25 363 1.139 400 1.000 20.970 0.55 8.927 34.95 0.613 755 A1 Locally Important Aquifer 2.267 N/A
Figure C.13: Pooled Flood Growth Curve Figure C.14: L Moment Plot 3.5
0.7 3 0.6
2.5 0.5
EV1 0.4 2 LO 0.3 LN2
GEV CV
- 0.2 L 1.5 GLO 0.1 Flood Growth Factor Growth Flood LN3 %AEP 1 0.0 50% 20% 10% 5% 2% 1% 0.5% 0.1% Lee CFRAM Catchment Average -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 -0.1 0.5 -0.2
-0.3 0 L-Skewness 0 1 2 3 4 5 6 7 8 Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 Fitted Trendline
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Figure C.15: Typical UPO-ERR Gamma Curve based on Gauge 16005 Figure C.16: Typical UPO-ERR Gamma Curve based on Gauge 14007
100% 100%
90% 90%
80% 80%
70% 70%
60% 60%
50% 50%
40% 40%
% of Peak Flow Peak of % Flow Peak of % 30% 30%
20% 20%
10% 10%
0% 0% -40 -20 0 20 40 60 80 100 -40 -20 0 20 40 60 80 100 Time to Peak Flow (Hours) Time to Peak Flow (Hours)
Table C.7: Castlemartyr AFA Design Peak Flows Pivotal AREA0.777/QMED 95% Confidence Flood Growth LOCATION HEP Site QMED Check Limit Curve Flood Growth Factor Design Peak Flows (m3/s) Hydrograph
50 20 10 5 2 1 0.5 0.1 50 20 10 5 2 1 0.5 0.1 Kiltha u/s Survey 19_1909_9 19020 6.9 7 12.9 GLO 1.00 1.26 1.45 1.65 1.95 2.21 2.50 3.33 6.87 8.68 9.98 11.36 13.40 15.17 17.17 22.91 16005 Extent Kiltha d/s Mill 19_1909_15 19020 8.5 6 16.0 GLO 1.00 1.26 1.45 1.65 1.95 2.21 2.50 3.33 8.54 10.78 12.39 14.10 16.64 18.84 21.33 28.46 16005
Kiltha u/s Womanagh 19_1909_17 19020 8.6 6 16.1 GLO 1.00 1.26 1.45 1.65 1.95 2.21 2.50 3.33 8.59 10.85 12.47 14.20 16.75 18.96 21.46 28.64 16005
Womanagh u/s Kiltha 19_1266_7 19020 3.0 6 5.6 GLO 1.00 1.36 1.61 1.85 2.17 2.42 2.68 3.31 2.97 4.03 4.77 5.49 6.45 7.20 7.96 9.83 36021 Womanagh d/s Kiltha 19_705_1 19020 11.6 6 21.8 GLO 1.00 1.25 1.43 1.62 1.90 2.14 2.42 3.21 11.61 14.50 16.56 18.77 22.03 24.86 28.05 37.22 14007
Area and other catchment descriptors for the HEP have been provided in Appendix B: Area and other catchment descriptors for the pivotal site have been included in the earlier tables in Appendix C for each AFA.
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C.3 Killeagh AFA
Figure C.17: Killeagh AFA Schematic of QMED River Dissour 19_686_10 9.6 m3/s
19_686_15 9.8 m3/s
19_1798_3 13.3 m3/s Womanagh River
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Table C.8: Dissour Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordanc record URBEX FLAT FSU HGF/ No. Length Count y (Di) length FARL T WET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 19020 28 28 0.703 28 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 13002 19 47 0.080 38 1.000 0.000 0.56 4.953 62.96 0.657 1044 B Poor Aquifer 0.645 N/A 30020 16 63 0.160 48 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important Aquifer 0.882 N/A - Karstified (conduit) 16006 33 96 0.683 132 0.994 0.000 0.59 5.763 75.80 0.591 1116 B Locally Important Aquifer 0.562 Gauge within Karstic zone. But this makes up only a very small fraction of the catchment. 26058 24 120 0.748 120 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 29004 32 152 0.306 192 0.993 1.310 0.65 2.517 121.44 0.631 1107 A2 Regionally Important Aquifer 0.903 N/A - Karstified (conduit) 25044 40 192 0.142 280 0.997 0.000 0.59 2.666 92.55 0.575 1187 A2 Locally Important Aquifer 1.256 N/A 26018 49 241 0.108 392 0.756 0.340 0.69 0.553 119.48 0.649 1044 A2 Regionally Important Aquifer 1.006 N/A - Karstified (conduit) 30021 26 267 0.661 234 0.994 0.160 0.72 0.848 103.63 0.573 1168 B Regionally Important Aquifer 0.328 N/A - Karstified (conduit) 24022 20 287 0.173 200 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 20006 35 322 0.634 385 1.000 0.000 0.67 6.390 77.55 0.600 1463 B Locally Important Aquifer 0.574 N/A 26010 35 357 0.180 420 0.937 0.000 0.69 1.906 94.53 0.578 1064 B Locally Important Aquifer 0.919 N/A 25027 43 400 0.189 559 1.000 0.620 0.59 3.905 118.86 0.620 1021 A1 Locally Important Aquifer 1.248 N/A 25038 17 417 0.150 238 1.000 0.210 0.59 7.336 136.10 0.591 1249 B Locally Important Aquifer 0.725 N/A 29001 40 457 0.192 600 0.998 0.660 0.65 2.220 115.48 0.581 1090 A1 Locally Important Aquifer 1.560 Gauge on Karstic Zone. Majority of catchment is locally important aquifer. 25040 19 476 0.275 304 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 16005 30 506 0.284 510 1.000 0.330 0.59 6.524 84.00 0.542 1154 A2 Locally Important Aquifer 1.071 N/A
Figure C.18: Pooled Flood Growth Curve Figure C.19: L Moment Plot 3.5 0.7
3 0.6
0.5 2.5 0.4 EV1 LO 2 0.3 LN2 0.2
GEV CV - 1.5 L GLO 0.1
Flood Growth Factor Growth Flood LN3 0.0 1 %AEP -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 50% 20% 10% 5% 2% 1% 0.5% 0.1% Lee CFRAM Catchment Average -0.1 0.5 -0.2
-0.3 0 L-Skewness 0 1 2 3 4 5 6 7 8 Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 Fitted Trendline
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Figure C.20: Typical UPO-ERR Gamma Curve based on Gauge 16005
100%
80%
60%
40%
% of Peak Flow Peak of % 20%
0% -20 -10 0 10 20 30 40
-20%
Time to Peak Flow (Hours)
Table C.9: Killeagh AFA Design Peak Flows Pivotal AREA0.777/QMED 95% Confidence Flood Growth LOCATION HEP Site QMED Check Limit Curve Flood Growth Factor Design Peak Flows (m3/s) Hydrograph
50 20 10 5 2 1 0.5 0.1 50 20 10 5 2 1 0.5 0.1 Dissour upstream 19_686_10 19020 9.6 7 18.0 GLO 1.00 1.23 1.39 1.56 1.82 2.04 2.30 3.02 9.6 11.8 13.3 15.0 17.5 19.6 22.0 29.0 16005 Dissour at Killeagh 19_686_15 19020 9.8 7 18.3 GLO 1.00 1.23 1.39 1.56 1.82 2.04 2.30 3.02 9.8 12.0 13.6 15.3 17.8 20.0 22.4 29.5 16005 Dissour Downstream at Womanagh 19_1798_3 19020 13.3 7 24.9 GLO 1.00 1.23 1.39 1.56 1.82 2.04 2.30 3.02 13.3 16.3 18.4 20.8 24.2 27.1 30.5 40.1 16005 Confluence
Area and other catchment descriptors for the HEP have been provided in Appendix B: Area and other catchment descriptors for the pivotal site have been included in the earlier tables in Appendix C for each AFA.
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C.4 Womanagh MPW
Figure C.21: Womanagh MPW Schematic of QMED Womanagh River 19_705_1 11.6m3/s Ladysbridge Stream 19_705_2 11.8 m3/s 19_1823_1+ 0.7 m3/s 19_1823_1 12.7 m3/s Dower River 19_1823_5 13 m3/s 19_1824_19 3.3 m3/s 19_1833_1 16 m3/s Ballyling Stream 19_1628_2 3 19_1247_10 17.9 m /s 2.7m3/s 19_1793_1 19.6 m3/s Dissour River 19_1793_2 19.6 m3/s 19_1798_3 13.3 m3/s 19_1794_1 (Killeagh) 30.6 m3/s
19_1941_2+ 32.6 m3/s
Youghal Bay
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Table C.10 Womanagh Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordancy record FLAT HGF/ No. Length Count (Di) length FARL URBEXT WET S1085 AREA BFI SAAR FSU Class Karstic Catchment? QMED Additional Comments 19020 28 28 0.768 28 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 26018 49 77 0.117 98 0.756 0.340 0.69 0.553 119.48 0.649 1044 A2 Regionally Important Aquifer - Karstified (conduit) 1.006 N/A 29004 32 109 0.334 96 0.993 1.310 0.65 2.517 121.44 0.631 1107 A2 Regionally Important Aquifer - Karstified (conduit) 0.903 N/A 25027 43 152 0.207 172 1.000 0.620 0.59 3.905 118.86 0.620 1021 A1 Locally Important Aquifer 1.248 N/A 26058 24 176 0.816 120 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 16006 33 209 0.745 198 0.994 0.000 0.59 5.763 75.80 0.591 1116 B Locally Important Aquifer 0.562 Gauge within Karstic zone. But this makes up only a very small fraction of the catchment. 6070 27 236 0.067 189 0.830 1.260 0.65 6.444 162.02 0.708 1046 A1 Poor Aquifer 1.215 N/A 6012 47 283 0.147 376 0.831 1.250 0.65 5.225 162.80 0.708 1046 A1 Poor Aquifer 1.240 N/A 25014 54 337 0.070 486 1.000 0.470 0.62 5.897 164.41 0.641 1008 A1 Locally Important Aquifer 1.507 N/A 26010 35 372 0.196 350 0.937 0.000 0.69 1.906 94.53 0.578 1064 B Locally Important Aquifer 0.919 N/A 29001 40 412 0.209 440 0.998 0.660 0.65 2.220 115.48 0.581 1090 A1 Locally Important Aquifer 1.560 Gauge on Karstic Zone. Majority of catchment is locally important aquifer. 25044 40 452 0.155 480 0.997 0.000 0.59 2.666 92.55 0.575 1187 A2 Locally Important Aquifer 1.256 N/A 25020 35 487 0.114 455 0.999 0.440 0.63 1.843 197.09 0.670 1015 B Locally Important Aquifer 0.661 N/A 30021 26 513 0.722 364 0.994 0.160 0.72 0.848 103.63 0.573 1168 B Regionally Important Aquifer - Karstified (conduit) 0.328 N/A 19020 28 28 0.768 28 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 26018 49 77 0.117 98 0.756 0.340 0.69 0.553 119.48 0.649 1044 A2 Regionally Important Aquifer - Karstified (conduit) 1.006 N/A
Figure C.22: Flood Growth Curves Figure C.23: L Moment Plot 3.5 0.40 3 0.35
2.5 0.30
EV1 0.25 2 LO 0.20 LN2
1.5 GEV 0.15 Kurtosis
GLO - L Flood Growth Factor FloodGrowth LN3 0.10 1 %AEP 50% 20% 10% 5% 2% 1% 0.5% 0.1% 0.05
0.5 0.00 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 L-Skewness 0 Series1 Pooled L-Moments LO 0 1 2 3 4 5 6 7 8 LN2 EV1 GEV Logistic Reduced Variable GLO LN3 polynomial Fitted Trendline
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Table C.11 Ladysbridge Reach Flood Frequency Analysis Effectiv Pooling Pooling e Station Record Cumulativ Years Discordanc record FLAT FSU HGF/ No. Length e Years Count y (Di) length FARL URBEXT WET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 25034 26 26 26 0.672 26 1.000 0.000 0.65 2.572 10.77 0.698 969 A2 Locally Important Aquifer 1.182 N/A 30020 16 42 42 0.063 32 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important 0.882 N/A Aquifer - Karstified (conduit) 10022 17 59 59 0.197 51 1.000 29.720 0.54 11.166 12.94 0.660 822 A1 Poor Aquifer 1.527 N/A 25040 19 78 78 0.108 76 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 8005 18 96 96 0.656 90 1.000 25.010 0.54 6.893 9.17 0.637 711 A2 Locally Important Aquifer 1.046 N/A 6030 27 123 123 0.697 162 0.972 0.000 0.61 20.091 10.40 0.447 1157 B Poor Aquifer 0.701 N/A 16051 13 136 136 0.577 91 1.000 0.000 0.58 1.615 34.19 0.593 895 B Locally Important Aquifer 0.945 N/A 24022 20 156 156 0.068 160 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 10021 24 180 180 0.176 216 0.997 24.210 0.54 11.851 32.51 0.646 799 A1 Locally Important Aquifer 1.875 N/A 13002 19 199 199 0.032 190 1.000 0.000 0.56 4.953 62.96 0.657 1044 B Poor Aquifer 0.645 N/A 26058 24 223 223 0.294 264 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 8002 21 244 244 0.208 252 1.000 0.540 0.56 3.488 33.43 0.579 791 A1 Locally Important Aquifer 0.765 N/A 6031 18 262 262 1.137 234 1.000 1.540 0.63 8.102 46.17 0.552 931 A2 Poor Aquifer 1.049 N/A 19020 28 290 290 0.277 392 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 36021 27 317 317 0.115 405 0.995 0.000 0.69 19.110 23.41 0.330 1570 A2 Poor Aquifer 0.749 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. 26022 33 350 350 0.156 528 1.000 0.560 0.67 3.445 61.88 0.598 916 A2 Locally Important Aquifer 1.091 Small catchment, gauge situated within Karstic zone (lower reaches). Upper is aquifer. Caution 16006 33 383 383 0.269 561 0.994 0.000 0.59 5.763 75.80 0.591 1116 B Locally Important Aquifer 0.562 Gauge within Karstic zone. But this makes up only a very small fraction of the catchment.
Figure C.24: Pooled Flood Growth Curve Figure C.25: L Moment Plot 3.5 0.7 3 0.6 2.5 0.5 EV1 0.4 2 LO 0.3 LN2
1.5 CV 0.2
GEV - L GLO 0.1 Flood Growth Factor Growth Flood 1 LN3 0.0 50% 20% 10% 5% 2% 1% 0.5% 0.1% -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.5 %AEP -0.1 -0.2 0 -0.3 0 1 2 3 4 5 6 7 8 L-Skewness Logistic Reduced Variable Series1 Pooled L-Moments
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Table C.12 Dower Reach Flood Frequency Analysis Effectiv Pooling Pooling e Station Record Cumulativ Years Discordanc record FLAT FSU HGF/ No. Length e Years Count y (Di) length FARL URBEXT WET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 25034 26 26 26 0.820 26 1.000 0.000 0.65 2.572 10.77 0.698 969 A2 Locally Important Aquifer 1.182 N/A 30020 16 42 42 0.077 32 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important Aquifer - Karstified 0.882 N/A 25040 19 61 61 0.132 57 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 24022 20 81 81 0.083 80 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 26058 24 105 105 0.359 120 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 19020 28 133 133 0.337 168 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 36071 20 153 153 0.658 140 0.823 0.000 0.70 13.640 68.03 0.644 1315 B Regionally Important Aquifer - Karstified 0.939 Mix of geology. Majority Karstic. 16051 13 166 166 0.704 104 1.000 0.000 0.58 1.615 34.19 0.593 895 B Locally Important Aquifer 0.945 N/A 36021 27 193 193 0.140 243 0.995 0.000 0.69 19.110 23.41 0.585 1570 A2 Poor Aquifer 0.749 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. 10021 24 217 217 0.214 240 0.997 24.210 0.54 11.851 32.51 0.646 799 A1 Locally Important Aquifer 1.875 N/A 26022 33 250 250 0.190 363 1.000 0.560 0.67 3.445 61.88 0.598 916 A2 Locally Important Aquifer 1.091 Small catchment, gauge situated within Karstic zone (lower reaches). Upper is aquifer. Caution 19016 15 265 265 1.440 180 1.000 0.070 0.66 4.554 117.82 0.687 1267 ESB stn Locally Important Aquifer 1.001 Gauge seated on Karstic area. 40% Karstic. 26018 49 314 314 0.052 637 0.756 0.340 0.69 0.553 119.48 0.649 1044 A2 Regionally Important Aquifer - Karstified 1.006 N/A 29004 32 346 346 0.147 448 0.993 1.310 0.65 2.517 121.44 0.631 1107 A2 Regionally Important Aquifer - Karstified 0.903 N/A 25044 40 386 386 0.068 600 0.997 0.000 0.59 2.666 92.55 0.575 1187 A2 Locally Important Aquifer 1.256 N/A 26010 35 421 421 0.086 560 0.937 0.000 0.69 1.906 94.53 0.578 1064 B Locally Important Aquifer 0.919 N/A 25027 43 464 464 0.091 731 1.000 0.620 0.59 3.905 118.86 0.620 1021 A1 Locally Important Aquifer 1.248 N/A
Figure C.26: Pooled Flood Growth Curve Figure C.27: L Moment Plot 3.5 0.400 3 0.350
2.5 0.300 EV1 0.250 2 LO
LN2 0.200
Kurtosis - 1.5 GEV L 0.150
GLO Flood Growth Factor Growth Flood 1 LN3 0.100 50% 20% 10% 5% 2% 1% 0.5% 0.1% %AEP 0.050 0.5
0.000 0 -0.600 -0.400 -0.200 0.000 0.200 0.400 0.600 L-Skewness 0 1 2 3 4 5 6 7 8 Series1 Pooled L-Moments LO LN2 EV1 GEV GLO LN3 polynomial Fitted Trendline Logistic Reduced Variable
GLO and GEV are similar up to the 5%AEP. GLO was selected as the more conservative estimate for the more extrme AEP events.
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Table C.13 Ballying Reach Flood Frequency Analysis Effectiv Pooling Pooling e Station Record Cumulativ Years Discordanc record FLAT FSU HGF/ No. Length e Years Count y (Di) length FARL URBEXT WET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 25040 19 19 19 0.057 19 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 23012 18 37 37 0.536 36 0.999 2.430 0.64 11.674 61.63 0.427 1264 A2 Regionally Important 1.022 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. Aquifer - Karstified 8007 15 52 52 0.284 45 1.000 6.490 0.55 3.843 37.94 0.470 845 B Locally Important Aquifer 0.876 N/A 30020 16 68 68 0.033 64 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important 0.882 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. Aquifer - Karstified 6031 18 86 86 0.598 90 1.000 1.540 0.63 8.102 46.17 0.552 931 A2 Poor Aquifer 1.049 N/A 36031 30 116 116 0.634 180 0.958 6.000 0.67 4.251 63.77 0.497 910 A2 Locally Important Aquifer 1.140 N/A 36021 27 143 143 0.060 189 0.995 0.000 0.69 19.110 23.41 0.330 1570 A2 Poor Aquifer 0.749 Gauge situated on Karstic zone. Majority of catchment is of Poor Aquifer. 16051 13 156 156 0.303 104 1.000 0.000 0.58 1.615 34.19 0.593 895 B Locally Important Aquifer 0.945 N/A 16005 30 186 186 0.059 270 1.000 0.330 0.59 6.524 84.00 0.542 1154 A2 Locally Important Aquifer 1.071 N/A 35004 14 200 200 0.299 140 0.994 0.290 0.72 2.285 116.96 0.488 1103 A1 Locally Important Aquifer 1.289 N/A 34009 33 233 233 0.026 363 1.000 1.070 0.73 3.325 117.11 0.443 1257 A2 Locally Important Aquifer 1.309 N/A 6033 25 258 258 1.075 300 0.996 2.790 0.59 9.893 55.23 0.557 857 B Poor Aquifer 1.022 N/A 26009 35 293 293 0.073 455 0.936 0.000 0.68 2.994 98.22 0.538 1019 A2 Locally Important Aquifer 1.058 N/A 24022 20 313 313 0.036 280 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 9010 19 332 332 0.996 285 0.958 24.040 0.54 20.977 94.26 0.530 955 A1 Locally Important Aquifer 2.079 Including large areas of Poor Aquifer strata. 10004 14 346 346 1.159 224 0.986 0.000 0.54 25.037 30.57 0.517 1700 B Locally Important Aquifer 0.705 N/A 35002 34 380 380 0.105 578 0.986 0.000 0.72 13.263 88.82 0.523 1381 A2 Poor Aquifer 0.792 N/A
Figure C.28: Pooled Flood Growth Curve Figure C.29: L Moment Plot 3.5
0.450 3 0.400
0.350 2.5 EV1 0.300
2 LO 0.250 LN2
0.200 Kurtosis 1.5 - GEV L 0.150 GLO Flood Growth Factor Growth Flood 0.100 1 LN3 50% 20% 10% 5% 2% 1% 0.5% 0.1% %AEP 0.050 0.5 0.000 -0.600 -0.400 -0.200 0.000 0.200 0.400 0.600 -0.050 0 0 1 2 3 4 5 6 7 8 L-Skewness Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 GEV GLO LN3 polynomial Fitted Trendline
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Table C.14: Dissour Reach Flood Frequency Analysis Pooling Pooling Effective Station Record Years Discordanc record URBEX FLAT FSU HGF/ No. Length Count y (Di) length FARL T WET S1085 AREA BFI SAAR Class Karstic Catchment? QMED Additional Comments 19020 28 28 0.703 28 1.000 0.000 0.63 11.017 73.95 0.687 1179 A2 Locally Important Aquifer 1.116 N/A 13002 19 47 0.080 38 1.000 0.000 0.56 4.953 62.96 0.657 1044 B Poor Aquifer 0.645 N/A 30020 16 63 0.160 48 1.000 0.990 0.72 2.891 21.41 0.610 1191 B Regionally Important Aquifer 0.882 N/A - Karstified (conduit) 16006 33 96 0.683 132 0.994 0.000 0.59 5.763 75.80 0.591 1116 B Locally Important Aquifer 0.562 Gauge within Karstic zone. But this makes up only a very small fraction of the catchment. 26058 24 120 0.748 120 0.995 1.040 0.65 5.535 59.98 0.697 974 B Locally Important Aquifer 0.548 Gauge situated on very minor Karstic zone within catchment. 29004 32 152 0.306 192 0.993 1.310 0.65 2.517 121.44 0.631 1107 A2 Regionally Important Aquifer 0.903 N/A - Karstified (conduit) 25044 40 192 0.142 280 0.997 0.000 0.59 2.666 92.55 0.575 1187 A2 Locally Important Aquifer 1.256 N/A 26018 49 241 0.108 392 0.756 0.340 0.69 0.553 119.48 0.649 1044 A2 Regionally Important Aquifer 1.006 N/A - Karstified (conduit) 30021 26 267 0.661 234 0.994 0.160 0.72 0.848 103.63 0.573 1168 B Regionally Important Aquifer 0.328 N/A - Karstified (conduit) 24022 20 287 0.173 200 1.000 0.330 0.60 3.291 41.21 0.620 942 A2 Locally Important Aquifer 0.791 N/A 20006 35 322 0.634 385 1.000 0.000 0.67 6.390 77.55 0.600 1463 B Locally Important Aquifer 0.574 N/A 26010 35 357 0.180 420 0.937 0.000 0.69 1.906 94.53 0.578 1064 B Locally Important Aquifer 0.919 N/A 25027 43 400 0.189 559 1.000 0.620 0.59 3.905 118.86 0.620 1021 A1 Locally Important Aquifer 1.248 N/A 25038 17 417 0.150 238 1.000 0.210 0.59 7.336 136.10 0.591 1249 B Locally Important Aquifer 0.725 N/A 29001 40 457 0.192 600 0.998 0.660 0.65 2.220 115.48 0.581 1090 A1 Locally Important Aquifer 1.560 Gauge on Karstic Zone. Majority of catchment is locally important aquifer. 25040 19 476 0.275 304 1.000 6.180 0.60 13.494 28.02 0.576 990 A2 Locally Important Aquifer 1.322 N/A 16005 30 506 0.284 510 1.000 0.330 0.59 6.524 84.00 0.542 1154 A2 Locally Important Aquifer 1.071 N/A
Figure C.30: Pooled Flood Growth Curve Figure C.31: L Moment Plot 3.5 0.7
3 0.6
0.5 2.5 0.4 EV1 LO 2 0.3 LN2 0.2
GEV CV - 1.5 L GLO 0.1
Flood Growth Factor Growth Flood LN3 0.0 1 %AEP -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 50% 20% 10% 5% 2% 1% 0.5% 0.1% Lee CFRAM Catchment Average -0.1 0.5 -0.2
-0.3 0 L-Skewness 0 1 2 3 4 5 6 7 8 Logistic Reduced Variable Series1 Pooled L-Moments LO LN2 EV1 Fitted Trendline
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Figure C.32: Typical UPO-ERR Gamma Curve based on Gauge 36021 Figure C.33: Typical UPO-ERR Gamma Curve based on Gauge 16005
100% 100%
90% 90%
80% 80%
70% 70%
60% 60%
50% 50%
40% 40%
% of Peak Flow Peak of % % of Peak Flow Peak of % 30% 30%
20% 20%
10% 10%
0% 0% -10 -8 -6 -4 -2 0 2 4 6 8 10 -40 -30 -20 -10 0 10 20 30 40 Time to Peak Flow (Hours) Time to Peak Flow (Hours)
Figure C.34: Typical UPO-ERR Gamma Curve based on Gauge 25027
100%
90%
80%
70%
60%
50%
40% % of Peak Flow Peak of % 30%
20%
10%
0% -20 -10 0 10 20 30 40 Time to Peak Flow (Hours)
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Table C.15: Womanagh MPW Design Peak Flows Pivotal AREA0.777/QMED 95% Confidence Flood Growth LOCATION HEP Site QMED Check Limit Curve Flood Growth Factor Design Peak Flows (m3/s) Hydrograph
50 20 10 5 2 1 0.5 0.1 50 20 10 5 2 1 0.5 0.1 Womanagh upstream Kiltha 19_1266_7 19020 11.6 6 21.8 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 11.6 14.6 16.7 18.9 22.2 25.1 28.4 37.7 25027 Kiltha upstream Womanagh 19_1909_17 19020 11.8 6 22.1 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 11.8 14.8 16.9 19.2 22.6 25.5 28.9 38.4 25027 Womanagh downstream Kiltha 19_705_1 19020 12.7 6 21.3 GLO-P 1.00 1.35 1.58 1.80 2.08 2.29 2.51 3.00 0.7 0.9 1.1 1.2 1.4 1.6 1.7 2.1 36021 Womanagh upstream Ladysbridge 19_705_2 19020 12.7 6 23.8 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 12.7 15.9 18.2 20.6 24.3 27.4 31.0 41.2 25027 Ladysbridge 19_1823_1+ 25034 13.0 6 24.5 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 13.0 16.4 18.7 21.2 25.0 28.2 31.9 42.4 25027 Womanagh downstream 19_1823_1 19020 3.3 5 6.2 GLO-P 1.00 1.24 1.41 1.60 1.87 2.11 2.38 3.14 3.3 4.1 4.7 5.3 6.2 7.0 7.8 10.4 36021 Ladysbridge Womanagh upstream Dower 19_1823_5 19020 16.0 6 30.1 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 16.0 20.1 23.0 26.1 30.7 34.7 39.2 52.1 25027 Dower upstream Womanagh 19_1824_19 25034 17.9 6 33.7 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 17.9 22.5 25.8 29.2 34.4 38.9 43.9 58.4 25027 Womanagh downstream Dower 19_1833_1 19020 2.7 4 5.0 GLO-P 1.00 1.26 1.45 1.65 1.94 2.20 2.49 3.32 2.7 3.4 3.9 4.4 5.2 5.9 6.6 8.9 36021 Womanagh upstream Ballying 19_1628_2 19020 19.1 6 35.8 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 19.1 23.9 27.4 31.1 36.6 41.3 46.7 62.1 25027 Ballying upstream Womanagh 19_1247_10 22022 19.6 6 36.9 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 19.6 24.6 28.2 32.0 37.6 42.5 48.0 63.9 25027 Womanagh downstream Ballying 19_1793_1 19020 13.3 7 24.9 GLO-P 1.00 1.23 1.39 1.56 1.82 2.04 2.30 3.02 13.3 16.3 18.4 20.8 24.2 27.1 30.5 40.1 16005 Womanagh upstream Dissour 19_1793_2 19020 30.6 7 57.3 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 30.6 38.3 43.9 49.8 58.5 66.1 74.7 99.3 25027 Dissour upstream Womanagh 19_1798_3 19020 32.6 7 61.2 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 32.6 40.9 46.8 53.1 62.4 70.5 79.7 105.9 25027 Womanagh downstream Dissour 19_1794_1 19020 11.6 6 21.8 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 11.6 14.6 16.7 18.9 22.2 25.1 28.4 37.7 25027 Womanagh downstream 19_1941_2+ 19020 11.8 6 22.1 GLO-P 1.00 1.25 1.44 1.63 1.92 2.16 2.45 3.25 11.8 14.8 16.9 19.2 22.6 25.5 28.9 38.4 25027
Area and other catchment descriptors for the HEP have been provided in Appendix B: Area and other catchment descriptors for the pivotal site have been included in the earlier tables in Appendix C for each AFA.
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Appendix D. Future Peak Flows and Levels
Tables D.1 and D.2 lists the design peak flows and levels at key HEPs adjusted for the combined future scenarios outlined in Table 11.3 of the main report.
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Table D.1: Future Peak Flows Location MRFS Design Peak Flows (m3/s) HEFS Design Peak Flows (m3/s) HEP 50%AEP 20 10 5 2 1 0.5 0.1 50%AEP 20 10 5 2 1 0.5 0.1 Ballingeary AFA Bunsheelin at Ballingeary upstream 19_1755_1 18.3 22.7 25.9 29.3 34.3 38.6 43.5 57.5 19.8 24.6 28.0 31.7 37.1 41.8 47.1 62.3 Bunsheelin at Ballingeary Town 19_1971_2 19.4 24.1 27.5 31.1 36.4 41.0 46.2 61.1 21.0 26.1 29.8 33.7 39.4 44.4 50.0 66.2 Bunsheelin at Lee Confluence 19_927_2 23.2 28.8 32.8 37.1 43.4 48.9 55.1 72.9 25.1 31.2 35.5 40.2 47.0 53.0 59.7 79.0 Upper Lee upstream 19_928_2 32.0 39.9 45.6 51.7 60.7 68.4 77.2 102.5 34.6 43.3 49.4 56.0 65.7 74.1 83.7 111.0 Lee at downstream of Bunsheelin/Lee Conf. 19_925_1 51.7 64.6 73.7 83.5 98.1 110.6 124.8 165.7 56.0 69.9 79.9 90.5 106.2 119.9 135.3 179.5 Upper Lee at upstream of Lough Allua 19_1714_2 58.2 73.1 83.7 95.0 111.8 126.3 142.7 189.9 63.1 79.2 90.7 102.9 121.1 136.9 154.6 205.7 Inchgeelagh at downstream of Lough Allua 19_1423_3 60.8 76.3 87.4 99.2 116.8 131.9 149.1 198.3 65.9 82.7 94.7 107.5 126.5 142.9 161.5 214.8 Castlemartyr AFA Kiltha upstream 19_1909_9 8.4 10.7 12.3 14.0 16.5 18.6 21.1 28.2 9.2 11.6 13.3 15.1 17.8 20.2 22.9 30.5 Kiltha at Castlemartyr 19_1909_15 10.8 13.6 15.7 17.8 21.0 23.8 27.0 36.0 11.7 14.8 17.0 19.4 22.9 25.9 29.3 39.1 Kiltha at Womanagh Confluence 19_1909_17 10.8 13.7 15.8 17.9 21.2 24.0 27.1 36.2 11.8 14.9 17.1 19.5 23.0 26.0 29.5 39.3 Womanagh upstream of the Kiltha 19_1266_7 3.6 4.8 5.7 6.6 7.7 8.6 9.6 11.8 3.9 5.2 6.2 7.1 8.4 9.4 10.4 12.8 Womanagh downstream of the Kiltha 19_705_1 14.4 18.0 20.6 23.3 27.4 30.9 34.8 46.2 15.7 19.5 22.3 25.3 29.7 33.5 37.8 50.2 Killeagh AFA Dissour Upstream 19_686_12 11.5 14.1 16.0 18.0 21.0 23.5 26.4 34.7 12.5 15.3 17.3 19.5 22.7 25.5 28.6 37.6 Dissour at Killeagh 19_686_15 11.7 14.4 16.3 18.3 21.3 24.0 26.9 35.4 12.7 15.6 17.7 19.9 23.1 26.0 29.2 38.3 Dissour at Womanagh Confluence 19_1798_3 15.9 19.5 22.1 24.9 29.0 32.5 36.6 48.1 17.2 21.2 24.0 27.0 31.4 35.3 39.6 52.1 Womanagh MPW Womanagh downstream of the Kiltha 19_705_1 14.4 18.1 20.7 23.5 27.6 31.2 35.2 46.9 15.7 19.6 22.5 25.5 30.0 33.9 38.3 50.9 Womanagh upstream Ladysbridge 19_705_2 14.6 18.3 21.0 23.8 28.0 31.7 35.8 47.6 15.9 19.9 22.8 25.9 30.5 34.4 38.9 51.7 Ladysbridge 19_1823_1+ 0.9 1.2 1.4 1.5 1.8 2.0 2.2 2.6 0.9 1.3 1.5 1.7 1.9 2.1 2.3 2.8 Womanagh downstream of Ladysbridge 19_1823_1 15.7 19.6 22.5 25.5 30.0 33.9 38.3 50.9 17.0 21.3 24.4 27.7 32.6 36.8 41.6 55.3 Womanagh upstream Dower 19_1823_5 16.1 20.2 23.1 26.2 30.8 34.8 39.4 52.3 17.5 21.9 25.1 28.5 33.5 37.8 42.7 56.8 Dower upstream Womanagh 19_1824_19 4.0 4.9 5.6 6.3 7.4 8.3 9.4 12.4 4.3 5.3 6.1 6.9 8.0 9.0 10.2 13.5 Womanagh downstream of the Dower 19_1833_1 19.7 24.7 28.3 32.1 37.7 42.6 48.1 64.0 21.4 26.8 30.7 34.8 40.9 46.2 52.2 69.4 Womanagh upstream Ballying 19_1628_2 22.0 27.5 31.5 35.8 42.1 47.5 53.7 71.4 23.8 29.9 34.2 38.8 45.6 51.5 58.2 77.4 Ballying upstream Womanagh 19_1247_10 3.2 4.0 4.6 5.3 6.2 7.0 8.0 10.6 3.5 4.4 5.0 5.7 6.7 7.6 8.6 11.5 Womanagh downstream Ballying 19_1793_1 23.3 29.2 33.5 38.0 44.7 50.4 57.0 75.8 25.3 31.7 36.3 41.2 48.4 54.7 61.8 82.2 Womanagh upstream Dissour 19_1793_2 24.0 30.1 34.4 39.1 45.9 51.9 58.6 78.0 26.0 32.6 37.3 42.4 49.8 56.3 63.6 84.6 Dissour upstream Womanagh 19_1798_3 15.9 19.5 22.1 24.9 29.0 32.5 36.6 48.1 17.2 21.2 24.0 27.0 31.4 35.3 39.6 52.1 Womanagh downstream of the Dissour 19_1794_1 37.1 46.5 53.2 60.4 71.1 80.3 90.7 120.6 40.2 50.4 57.7 65.5 77.1 87.0 98.3 130.7 Womanagh tidal outfall 19_1941_2+ 39.5 49.6 56.8 64.4 75.8 85.6 96.7 128.6 42.9 53.7 61.5 69.8 82.1 92.8 104.8 139.4
Table D.2: Future Total Tide Plus Surge Levels Location MRFS Design Total Tide Plus Surge Level (mODM) HEFS Design Total Tide Plus Surge Level (mODM) Source 50%AEP 20 10 5 2 1 0.5 0.1 50%AEP 20 10 5 2 1 0.5 0.1 Womanagh Tidal Outfall ICPSS Point S_31 1.11 1.40 1.60 1.82 2.15 2.43 2.74 3.65 0.93 1.21 1.52 1.74 1.97 2.33 2.63 2.97
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