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HomeMy WebLinkAbout2560523 - F.I. Received Doc. - Flood risk assessment FLOOD RISK ASSESSMENT AT LARAGH CASTLEBLAYNEY CO. MONAGHAN Prepared for Cillian & Maggie Coleman Prepared by Traynor Environmental Ltd Reference Number 25.756 TE Date of Issue 8th May 2026 Belturbet Business Park, Creeny. Belturbet, Co Cavan T: + 353 49 9522236 E: nevin@traynorenv.com www.traynorenvironmental.ie RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 2 Issue Date Details Prepared by Checked/Approved by 1 8th May 2026 Final Francis Mc Mahon Environmental Consultant Nevin Traynor Environmental Scientist Project Title: Flood Risk Assessment Client: Cillian & Maggie Coleman Office Reference: 25.756 TE Status: Final Date: 8th May 2026 Technical Reviewer Signature FNevin Traynor Environmental Scientist Date: 8th May 2026 Traynor Environmental Belturbet Business Park Creeny Belturbet Co. Cavan H14AY94 Tel: 049 9522236 Email: info@traynorenvironmental.ie © This Report is the copyright of Traynor Environmental Ltd. Any unauthorized reproduction or usage by any person other than the addressee is strictly prohibited. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 3 CONTENT 1.0 INTRODUCTION 4 1.1 Flood Risk Management Guidelines (2009) 4 1.2 Methodology 4 1.3 Definition of Flood Risk 4 1.4 Stages of the Flood Risk Assessment 5 1.5 Likelihood of Flooding 5 1.6 Definition of Flood Zones 6 1.7 Development Plans and Policy Context 7 2.0 The Planning System and Flood Risk Management Guidelines OPW 8 2.1 The Planning Systems and Flood Risk Management Document 8 2.2 Vulnerability and Land Use 9 2.3 Stages of Flood Risk Assessment 12 3.0 SITE DESCRIPTION & LOCATION 13 3.1 Site Description 13 3.2 Development Proposal 13 3.3 Site levels & topography Survey 14 4.0 GEOLOGY & HYDROGEOLOGY 15 4.1 Soils 15 4.2 Hydrology 16 4.3 Affected Water bodies 18 5.0 FLOODING HISTORY 19 5.1 Published information 19 5.2 Historical OSI Maps. 19 5.3 OPW National Flood Hazard Mapping 20 5.4 CFRAM & Flood Mapping Review 22 5.5 Compliance with the Sequential Approach 22 6.0 ASSESSMENT OF FLOODING MECHANISMS 23 6.1 Preamble 23 6.2 Initial assessment 23 6.3 Flood mechanisms 23 6.4 Benefiting lands 24 7.0 SPR MODEL 25 8.0 SUMMARY OF FINDINGS AND RECOMMENDATIONS 26 8.1 Flood risk to proposed developments 26 8.2 Flood risk to adjacent developments 26 8.3 Design considerations/Mitigation Measures 26 9.0 CONCLUSION 27 APPENDIX A - TOPOGRAPHICAL SURVEY 28 APPENDIX B - SITE INVESTIGATION 12.02.26 30 RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 4 1.0 INTRODUCTION Traynor Environmental Ltd. have been appointed to carry out a Site-Specific Flood Risk Assessment (FRA) for the proposed development at Laragh, Castleblayney, Co. Monaghan. The applicants, Cillian & Maggie Coleman, are seeking permission to construct a new two-storey dwelling house, detached domestic garage, new entrance onto the public road, wastewater treatment system and percolation area, together with all associated site development works at Laragh, Castleblayney, Co. Monaghan. Section 15.22.8 of the Monaghan County Development Plan 2025–2031 requires that development proposals in areas potentially at risk of flooding be supported by a Site-Specific Flood Risk Assessment, prepared in accordance with the DECLG “The Planning System and Flood Risk Management Guidelines for Planning Authorities (2009)” and Departmental Circular PL2/2014. The Office of Public Works (OPW) Preliminary Flood Risk Assessment (PFRA) maps indicate that part of the application site is vulnerable to pluvial flooding events. In this regard, the Applicant shall submit a Flood Risk Assessment for the proposed development, completed by a competent professional with hydrological experience, confirming that the development: • Will not be at risk of flooding • Will not exacerbate flooding in the immediate vicinity or wider area. • Will not obstruct or impede important flow paths • Will not result in residual risks to the area and/or development that cannot be managed to an acceptable level. The flood risk assessment shall also clearly demonstrate proposed management of any residual risks. 1.1 Flood Risk Management Guidelines (2009) As per the Flood Risk Management Guidelines (2009), where flood risk may be an issue for any proposed development, a flood risk assessment (FRA) should be carried out that is appropriate to the scale and nature of the development and the risks arising. The flood risk assessment outlined herein is intended to be sufficiently detailed to quantify the risks and effects of any flooding, necessary mitigation measures, together with recommendations on how to best manage any residual risks. As per the document ‘The Planning System and Flood Risk Management (2009) the flood risk assessment will consist of the following sections: • Site description • Site layout • S-P-R model; sequential approach; justification test • Determination of flood level • Mitigation measures • Conclusions Traynor Environmental carried out site inspections on 12th February 2026. The inspection consisted of a walkover and visual inspection of the site and in the vicinity of the site. 1.2 Methodology The methodology used for the flood risk assessment is based on ‘The Planning System and Flood Risk Management Guidelines for Planning Authorities’ (2009)’ and also incorporating the Strategic Flood Risk Assessment. The FRM Guidelines require the planning system at national, regional, and local levels to: • Avoid development in areas at risk of flooding, particularly floodplains, unless there are proven wider sustainability grounds that justify appropriate development. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 5 • Adopt a sequential approach if applicable to flood risk management when assessing the location for new development based on avoid, substitute, justify, mitigate, and proceed; and • Incorporate flood risk assessment into the process of making decisions on planning applications and planning appeals. 1.3 Definition of Flood Risk Flood risk is a combination of the likelihood of a flood event occurring and the potential consequences arising from that flood event and is then normally expressed in terms of the following relationship: Flood risk = Likelihood of flooding x Consequences of flooding. To fully assess flood, risk an understanding of where the water comes from (i.e. the source), how and where it flows (i.e. the pathways) and the people and assets affected by it (i.e. the receptors) is required. Figure 1 below shows a source-pathway- receptor model. Figure 1: Source-Pathway-Receptor Model The principal sources of flooding are rainfall or higher than normal sea levels. The principal pathways are rivers, drains, sewers, overland flow and river and coastal floodplains. The receptors can include people, their property and the environment. All three elements as well as the vulnerability and exposure of receptors must be examined to determine the potential consequences. 1.4 Stages of the Flood Risk Assessment The detail and complexity of the study required should be appropriate to the scale and potential impact of the development. For the purposes of this study, the following have been considered: • Available information on historical flooding in the area. • Site level information. • Details of structures, which may influence hydraulics of the watercourse and consideration of the effect of blockage of structures. • Estimates of design levels when works have been completed. 1.5 Likelihood of Flooding The Guidelines define the likelihood of flooding as the percentage probability of a flood of a given magnitude or severity occurring or being exceeded in any given year. It is generally expressed as a return period or annual exceedance probability (AEP). A 1% AEP flood indicates a flood event that will be equalled or exceeded on average once every hundred RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 6 years and has a return period of 1 in 100 years. Annual Exceedance Probability is the inverse of return period as shown in Table 1 below. Table 1: Correlation between return period and AEP Return Period (years) Annual Exceedance Probability (%) 1 100 10 10 50 2 100 1 200 0.5 1000 0.1 1.6 Definition of Flood Zones Flood zones are geographical areas within which the likelihood of flooding is in a particular range and are split into three categories in The Guidelines: 1.6.1 Flood Zone A Flood Zone A where the probability of flooding from rivers and the sea is highest (greater than 1% or 1 in 100 for river flooding or 0.5% or 1 in 200 for coastal flooding); Most types of development would be considered inappropriate in this zone. Development in this zone should be avoided and/or only considered in exceptional circumstances, such as in city and town centres, or in the case of essential infrastructure that cannot be located elsewhere, and where the Justification Test has been applied. Only water-compatible development, such as docks and marinas, dockside activities that require a waterside location, amenity open space, outdoor sports and recreation, would be considered appropriate in this zone. 1.6.2 Flood Zone B Flood Zone B where the probability of flooding is moderate (between 0.1% or 1 in 1000 and 1% or 1 in 100 for river flooding a nd between 0.1% or 1 in 1000 or 0.5% or 1 in 200 for coastal flooding); Highly vulnerable development, such as hospitals, residential care homes, Garda, fire and ambulance stations, dwelling houses and primary strategic transport and utilities infrastructure, would generally be considered inappropriate in this zone, unles s the requirements of the Justification Test can be met. Less vulnerable development, such as retail, commercial and industrial uses, sites used for short-let for caravans and camping and secondary strategic transport and utilities infrastructure, and water-compatible development might be considered appropriate in this zone. In general, however, less vulnerable development should only be considered in this zone if adequate lands or sites are not available in Zone C and subject to a flood risk assessment to the appropriate level of detail to demonstrate that flood risk to and from the development can or will adequately be managed. 1.6.3 Flood Zone C Flood Zone C where the probability of flooding from rivers and the sea is low (less than 0.1% or 1 in 1000 for both river and coastal flooding. Flood Zone C covers all plan areas which are not in zones A or B. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 7 Development in this zone is appropriate from a flood risk perspective (subject to assessment of flood hazard from sources oth er than rivers and the coast) but would need to meet the normal range of other proper planning and sustainable development considerations. It is important to note that when determining flood zones the presence of flood protection structures should be ignored. This is because areas protected by flood defences still carry a residual risk from overtopping or breach of defences and the fact tha t there is no guarantee that the defences will be maintained in perpetuity. 1.7 Development Plans and Policy Context The Monaghan County Development Plan 2025–2031, including the Strategic Flood Risk Assessment (SFRA), has been considered in the preparation of this SFRA. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 8 2.0 The Planning System and Flood Risk Management Guidelines OPW This Flood Risk Assessment has been undertaken in accordance with “The Planning System and Flood Risk Management: Guidelines for Planning Authorities & Technical Appendices” produced by the Office of Public Works in November 2009. 2.1 The Planning Systems and Flood Risk Management Document The Planning Guidelines give guidance on flood risk; its identification, assessment and management in areas of potential development. The Guidelines recommend a “precautionary approach” (See Sections 1.11, 2.30, 3.1 and 5.16 of the Guidelines) when considering flood risk management in the planning system. The core principle of the guidelines is to adopt a risk-based approach to managing flood risk and to avoid development in areas that are at flood risk. This sequential approach is based on the identification of flood zones for river, lake and coastal flooding, as shown in Figure 2 and Table 2. Figure 2: Indicative Flood Zones (OPW & DoEHLG, 2009) Table 2: Correlation between return period and AEP Flood Zone Definition Annual Exceedance Probability A Probability of flooding from rivers and the sea is highest Greater than 1% or 1 in 100 for river flooding or 0.5% or 1 in 200 for coastal flooding B Probability of flooding from rivers and the sea is moderate Between 0.1% or 1 in 1000 and 1% or 1 in 100 for river flooding and between 0.1% or 1 in 1000 year and 0.5% or 1 in 200 for coastal flooding C Probability of flooding from rivers and the sea is low. Flood Zone C covers all areas of the plan which are not in zones A or B Less than 0.1% or 1 in 1000 for both river and coastal flooding RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 9 2.2 Vulnerability and Land Use The guidelines recognise that the vulnerability of potential development to flooding depends on the specific type of land use. Thus, defining the vulnerability of land use types to flooding can help when choosing appropriate development types in areas that are prone to flooding. Table 3 characterises different land use types and their vulnerabilities. Table 3: Extract from Guidelines for Planning Authorities - Classification of vulnerability of different types of development Vulnerability Class Land uses and types of development which include: Highly Vulnerable development (including essential infrastructure) Garda, ambulance and fire stations and command centres required to be operational during flooding; Hospitals; Emergency access and egress points; Schools; Dwelling houses, student halls of residence and hostels; Residential institutions such as residential care homes, children's homes and social service homes; Caravans and mobile home parks; Dwelling houses designed, constructed, or adapted for the Elderly or, other people with impaired mobility; and Essential infrastructure, such as primary transport and utilities distribution, including electricity generating power stations and sub-stations, water and sewage treatment, and potential significant sources of pollution (SEVECO sites, IPPC sites etc) in the event of flooding Less vulnerable development Buildings used for; retail, leisure, warehousing, commercial, industrial and non-residential institutions Land and buildings used for holiday or short-let caravans and camping, subject to specific warning and evacuations plans; Land and buildings used for agriculture and forestry Waste treatment (except landfill and hazardous waste); Mineral working and processing; and Local transport infrastructure Water-compatible development Flood control infrastructure Docks, marinas and wharves; Navigation facilities; Ship building, repairing and dismantling, dockside fish processing and refrigeration and compatible activities requiring a waterside location; Water-based recreation and tourism (excluding sleeping accommodation); Lifeguard and coastguard stations; Amenity space, outdoor sports and recreation and essential facilities such as changing rooms; and Essential ancillary sleeping or residential accommodation for staff required by uses in this category (subject to a specific warning and evacuation plan The probability and vulnerability of flooding informs the requirement for the application of a Justification Test. The decision matrix, illustrated in Table 4 below, shows a simple way of combining probability and vulnerability of flooding in order to classify the potential risk to the proposed development. Where the risk is considered high, then a Justification Test is required and applied. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 10 Table 4: Extract from Guidelines for Planning Authorities - Matrix of vulnerability versus flood zones required to meet the Justification Test. Vulnerability Class Flood Zone A Flood Zone B Flood Zone C Highly Vulnerable development (including essential infrastructure) Justification test Justification test Appropriate Less vulnerable development Justification test Appropriate Appropriate Water-compatible development Appropriate Appropriate Appropriate The Justification Test represents a series of conditions that must be met when flood risk is considered significant. Even if the Justification Test is not applied, an appropriately detailed Flood Risk Assessment should be completed in order to fully consider flood risk to the potential development. These conditions are set out in Table 5 below (section 5.15 of the Guidelines). Table 5: Extract from Guidelines for Planning Authorities – Box 5.1 Justification for development management Section 5.16 of the guidelines describes how developments in flood risk areas and mitigated and managed and are presented below: 5.16 Where development has to take place in areas at risk of flooding following the application of these Guidelines, the risks should be mitigated and managed through the location, lay-out and design of the development to reduce such risks to an acceptable level. The residual risks to the proposed development should be considered carefully, taking into account the type of development and its vulnerability, how flood risks to the occupants will be managed, insurance provision, scale of the risks and the provision of flood defence works. A precautionary approach would be to set floor levels above the 1% flood level ignoring the moderating effects of flood defences. However, within an existing built-up area the approach above may not produce an appropriate streetscape and therefore for proposed developments with a lower vulnerability, flood resistant and flood resilient construction methods to reduce the impact of flooding would be appropriate. In this Box 5.1 Justification Test for development management (to be submitted by the applicant) When considering proposals for development, which may be vulnerable to flooding, and that would generally be inappropriate as set out in Table 3.2, the following criteria must be satisfied: 1. The subject lands have been zoned or otherwise designated for the particular use or form of development in an operative development plan, which has been adopted or varied taking account of these Guidelines. 2. The proposal has been subject to an appropriate flood risk assessment that demonstrates: (i) The development proposed will not increase flood risk elsewhere and, if practicable, will reduce overall flood risk; (ii) The development proposal includes measures to minimise flood risk to people, property, the economy and the environment as far as reasonably possible; (iii) The development proposed includes measures to ensure that residual risks to the area and/or development can be managed to an acceptable level as regards the adequacy of existing flood protection measures or the design, implementation and funding of any future flood risk management measures and provisions for emergency services access; and (iv) The development proposed addresses the above in a manner that is also compatible with the achievement of wider planning objectives in relation to development of good urban design and vibrant and active streetscapes. The acceptability or otherwise of levels of residual risk should be made with consideration of the type and foreseen use of the development and the local development context. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 11 situation the flood risk assessment should be thorough and measures to manage these residual risks carefully detailed…. In all cases, a precautionary approach should be taken to allow for uncertainties in data and risk assessment procedures and to enable adaptability to future changes in risk, including the effects of climate change. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 12 2.3 Stages of Flood Risk Assessment “The Planning System and Flood Risk Management: Guidelines for Planning Authorities” document outlines that a staged approach to Flood Risk Assessment should be adopted and the stages of appraisal and assessment are as follows: • “Stage 1 Flood Risk Identification – to identify whether there may be any flooding or surface water management issues related to either the area of regional planning guidelines, development plans and LAP’s or a proposed development site that may warrant further investigation at the appropriate lower-level plan or planning application levels; • Stage 2 Initial Flood Risk Assessment – to confirm sources of flooding that may affect a plan area or proposed development site, to appraise the adequacy of existing information and to scope the extent of the risk of flooding which may involve preparing indicative flood zone maps. Where hydraulic models exist the potential impact of a development on flooding elsewhere and of the scope of possible mitigation measures can be assessed. In addition, the requirements of the detailed assessment should be scoped; and • Stage 3 Detailed Flood Risk Assessment – to assess flood risk issues in sufficient detail and to provide a quantitative appraisal of potential flood risk to a proposed or existing development or land to be zoned, of its potential impact on flood risk elsewhere and of the effectiveness of any proposed mitigation measures.” The Guidelines recognise that 'all stages may not be needed to complete a Flood Risk Assessment.' The required level of detail 'will depend on the level of risk and the potential conflict with proposed development and the scale of mitigation measures being proposed.' This flood risk assessment report is considered appropriate and sufficient to allow an informed decision with respect to the proposed development on the grounds of flood risk. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 13 3.0 Site Description & Location 3.1 Site Description The application site is located Laragh, Castleblayney, Co. Monaghan. Access to the site will be via the existing road. The site is bounded to the east by the L41131 road and to the north, south and west by agricultural grassland. Figure 3: Site Location 3.2 Development Proposal Permission to construct a new two storey style dwelling house, detached domestic garage, establish new entrance onto public road, new sewerage wastewater treatment system and percolation area, together with all associated site development works. at Laragh Castleblayney Co. Monaghan. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 14 Figure 4: Site Layout 3.3 Site Levels and Topography Survey The topographical site survey is incorporated into the site layout plan. All elevations quoted being relative to point on the site. The proposed finished floor levels of the new development will be 56.00m. Further levels are shown in table 6 below. Table 6: Site Elevations Location Proposed Elevation (m) Proposed Development finished floor level 56.00 Elevation at the development entrance 47.20 Elevation at the North boundary 55.00 Elevation at the South boundary 53.00 Elevation at the East boundary 55.20 Elevation at the West boundary 47.20 Level of access road into the site 50.00 RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 15 4.0 GEOLOGY & HYDROGEOLOGY The hydrogeology of the site was assessed by means of a desk study of relevant literature. This included available geological and hydrogeological information and maps from the Geological Survey of Ireland (GSI) and the EPA. Groundwater can be defined as water that is stored in, or moves through, pores and cracks in subsoils. 4.1 Soils The alluvial deposit maps of the Geological Survey of Ireland (GSI) were consulted to assess the extent of any alluvial depos its in the vicinity of the development site. Alluvial deposits can be an indicator of areas that have been subject to flooding in the recent geological past. Figure 5 below illustrates the sub-soils mapping for the general area of the site. The tests showed that the site has a Sub-surface value rating of 67.32min/25mm indicating average percolation characteristics of the Sub-surface. A surface value rating of 60.51min/25mm was attained indicating average percolation characteristics of the surface. Bedrock was not encountered in the trial hole. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 16 4.2 Hydrology The potential of rock to store and transport water is governed by permeability of which there are two types, intergranular and fissure permeability. The GSI, EPA and the Department of Environment, Heritage, and Local Government (DOEHLG) have developed a Programme of Groundwater Protection Schemes (GPWS), with the aim of maintaining the quality and quantity of groundwater in Ireland, and in some cases improving groundwater quality, by applying a risk assessme nt approach to groundwater protection and sustainable development. From the GSI maps for the area it can be seen that the bedrock aquifer underlying the site is located within an area of moderate groundwater vulnerability. Figure 6: Groundwater/Aquifer Map From the GSI Groundwater Aquifer Map Site is classified as PI - Poor Aquifer - Bedrock which is Generally Unproductive except for Local Zones Figure 7: Vulnerability Map From the GSI Vulnerability Map Site is classified as Moderate RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 17 Figure 8: Bedrock Map From the GSI Bedrock Map Site is classified as SMV - Silurian Metasediments and Volcanics Figure 9: Teagasc soil Map From the Teagasc Subsoil Map Site is classified as Sandstone and shale till (Lower Palaeozoic) & Alluvium RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 18 4.3 Affected Water bodies The application site is located within the Hydrometric Area (Erne 36), Catchment (Erne 36), Sub-Catchment (Annalee_SC_010) and Sub-Basin (KNAPPAGH_010). An existing surface water drain is located along the eastern boundary at the site entrance. A site inspection was undertaken on 12th of February 2026 following a period of extensive rainfall to assess the performance of the local drainage infrastructure and identify any evidence of pluvial flooding. At the time of inspection, there was no evidence of pluvial flooding within th e site, and the existing drain was observed to be operating effectively with no signs of surcharging or overflow onto the site. There was however pluvial ponding present in the field to the Northwest of the proposed site. Furthermore, the area identified in mapping as being potentially at risk of pluvial flooding showed no visible indicators of standing water, ponding, sediment deposition, or flood-related debris. This observation indicates that, under the rainfall conditions experienced prior to the inspection, the site drainage arrangements were functioning adequately. The photos from the site inspection are included in Appendix B. Topographical survey data indicate that ground levels across the site range approximately from 47.20m to 55.20m, with the proposed Finished Floor Level (FFL) set at 56.00m. Based on available mapping and site inspection, there is no indication that the site forms part of a functional floodplain. Figure 10: Ground Waterbodies Risk From the EPA Map Site Shows the Ground Waterbodies Risk as Not at risk IE_NW_G_061 RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 19 5.0 Flooding History As part of the study data collection phase, a number of available sources of information generally as set out in the Planning and Flood Risk Management – Guidance for Planning Authorities were investigated in order to build an understanding of the potential risk of flooding to the site. The following review highlights the key findings of the anecdotal evidence collectio n exercise. 5.1 Published Information 5.1.1 OPW National Preliminary Flood Risk Assessment The OPW is the lead agency for flood risk management in Ireland and is the national competent authority for the EU Floods Directive. OPW works in close partnership with all Local Authorities in delivering the objectives of the CFRAM Programme. 5.1.2 OPW National Flood Hazard Mapping The OPW’s online National Flood Hazard Mapping Database provides information on reported floods, in the form of reports, photographs and newspaper articles. The database provides information on historic flooding events. No flooding events are recorded within the site area. 5.2 Historical OSI Maps The historical 6” OSI maps, dated c.1830-1840, and slightly more detailed 25” OSI maps, dated later c.1900-1910, shows structures on the proposed site. The land would have been typically used for residential purposes. There are no indicators of flooding on historical maps. Figure 11: Historical OSI Maps Historic 6 Inch Mapping Historic 25 Inch Mapping 5.3 OPW National Flood Hazard Mapping The historic flood event data map for Laragh, Castleblayney, Co. Monaghan area obtained from the OPW flood mapping RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 20 website. The map provides no evidence of any actual historical flood incident occurring at the site. The historic flood event data map for the site area obtained from the OPW flood mapping website is shown in Figure 12. The map provides no evidence of any actual historical flood events occurring at the site. Figure 12: OPW National Flood Hazard Map In Summary the OPW Flood Mapping indicates that: • OPW flood maps indicate that no flooding events occurred on the proposed site. Figure 13: Floodinfo.ie (Pluvial/Rainfall flood mapping) RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 21 Figure 14: Monaghan County Council Pluvial Flood Map 5.4 CFRAM & Flood Mapping Review RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 22 A review of the OPW Floodinfo.ie portal and CFRAM flood mapping confirms that the site is not located within any mapped 1% AEP (1 in 100 year) fluvial flood extent or 0.1% AEP (1 in 1000 year) flood extent. The site is mapped within Flood Zone C (Low Probability of Flooding) under the Planning System and Flood Risk Management Guidelines (2009). No historical flood events are recorded within or adjacent to the site boundary. Accordingly, the site is not identified as being at risk from fluvial flooding under current national flood mapping datasets. 5.5 Compliance with the Sequential Approach In accordance with the Planning System and Flood Risk Management Guidelines for Planning Authorities (2009), the Sequential Approach seeks to direct development towards lands at the lowest probability of flooding (Flood Zone C) in preference to lands within Flood Zones A or B. A review of CFRAM mapping and Floodinfo.ie confirms that the application site is located within Flood Zone C (Low Probability of Flooding) and is not affected by mapped fluvial or pluvial flood extents. Accordingly , the proposed development complies with the Sequential Approach. As the site is located within Flood Zone C, the Justification Test is not required. While PFRA screening identifies a potential pluvial susceptibility within the wider area, detailed national flood mapping (CFRAM and Floodinfo.ie) confirms that no 1% AEP or 0.1% AEP flood extents intersect the site boundary. Site inspection further confirmed the absence of ponding, sediment deposition, or other indicators of historic surface water flooding within the application site. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 23 6.0 Assessment of Flooding Mechanisms 6.1 Preamble The Irish government, as part of its development control procedures, advises against inappropriate development in areas at risk of flooding and the avoidance of new developments increasing flood risk elsewhere in accordance with their Planning Policy Document. The following assessment determines the flood hazards to the life and property at the site in order to subsequently assess the site and proposed development relative to the Flood Risk Framework contained within the Planning Policy Document. 6.2 Initial Assessment The following is a record of the screening assessment of the development site for potential flooding mechanisms requiring subsequent detailed assessment, based on the information obtained from the background information review and consultations. Table 7: Possible Flooding Mechanisms Source/Pathway Significant Comment/Reason Fluvial Flooding Flood Plain No According to section 4.0 above Structure Blockage No No significant hydraulic structures have been identified downstream that would materially influence flood behaviour at the site. Flood Defence Failure N/A There is no flood defences located in the vicinity of the site. Coastal Flooding Tidal/Coastal N/A The site is not affected by tidal or coastal flooding due to its inland location within County Monaghan. Other Urban drainage No Urban drainage is not identified as a flood risk mechanism affecting the site. Fluvial Flooding No According to section 4.0 above Groundwater N/A Based on available mapping, historic records, and site inspection, groundwater flooding is not identified as a significant risk at this location. Pluvial Flooding Possible PFRA screening mapping indicates potential pluvial susceptibility within part of the site; however, no detailed 1% or 0.1% AEP pluvial flood extents are mapped within the site boundary. Infrastructure failure No Infrastructure failure not expected to be an issue on the site. Rainfall Ponding Possible A shallow localised topographical depression is present; however, no evidence of recurring ponding was observed during site inspection and the risk is not considered significant.. Reservoirs /Canals/ Artificial Sources N/A There are no impoundments or reservoirs in close proximity, or which drain to the site. 6.3 Flood Mechanisms Flooding is a natural process and can happen at any time in a wide variety of locations. Flooding can come from rivers and the sea, directly from rainfall on the ground surface and from rising groundwater, surcharging sewers, and drainage systems. 6.3.1 Fluvial Flooding RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 24 Fluvial Flooding occurs when rivers and streams break their banks and water flows out onto the adjacent low-lying areas (the natural floodplains). This can arise where the runoff from heavy rain exceeds the natural capacity of the river channel and can be exacerbated where a channel is blocked or constrained or, in estuarine areas, where high tide levels impede the flow of the river out into the sea. Different rivers will respond differently to rainfall events, depending on a range of factors such as the size and slope of t he catchment, the permeability of the soil and underlying rock, the degree of urbanization of the catchment and the degree to which flood waters can be stored and slowly released into lakes and along the river’s floodplains. A storm of a given rainfall depth and duration may cause flooding in one river, but not in another, and some catchments may be more prone than others to prolonged rainfall or a series of rain events. River flooding can occur rapidly in short, steep rivers or after some time, and some distance from where the rain fell, in larger or more gently flowing rivers. Changes in rainfall patterns, such as mi ght be caused by climate change, will have different impacts on flood magnitudes and frequency in different catchments. The Historical OSI Maps and OPW National Flood Hazard Mapping did not identify the site as being at risk of fluvial flooding. 6.3.2 Pluvial flooding This type of flooding is defined as flooding from rainfall-generated overland flow before the runoff enters any watercourse or sewer. This mainly occurs when intense rainfall, often of short duration, that is unable to soak into the ground or enter drainage systems, can run quickly off land and result in local flooding. It can also result when the drainage system is overwhelmed by heavy rainfall, becomes blocked or is of inadequate capacity. Flood risk from pluvial flooding exists in all areas. Provision of adequate storm water drainage systems will minimise the risk of pluvial flooding sources. There is no area inside the site boundary being at risk of pluvial flooding according to the Historical OSI Maps, OPW National Flood Hazard Mapping and OPW National Flood Hazard Mapping. There is no evidence of seasonal flooding within the site boundary. The proposed development will incorporate Sustainable Drainage Systems (SuDS) principles in accordance with the Greater Dublin Strategic Drainage Study (GDSDS) and Monaghan County Council requirements. Surface water runoff will be managed through controlled collection and discharge, utilising permeable ground areas for infiltration where appropriate and directing runoff away from the dwelling footprint. The development will ensure that post-development runoff rates do not exceed greenfield conditions and that surface water is managed at source as far as practicable. These measures will reduce peak runoff rates, limit localised ponding, and provide additional resilience during short-duration intense rainfall events. The proposed Finished Floor Level (56.00m) is set significantly above surrounding ground levels. While infiltration capacity of the subsoils is lower than peak rainfall intensity during extreme design events, any exceedance would result in shallow, temporar y and localised ponding only. There is no credible source–pathway–receptor linkage that would give rise to significant flood risk to the proposed dwelling. 6.3.3 Groundwater flooding Groundwater flooding occurs when water levels in the ground rise above surface elevation following prolonged and heavy rainfall. It is most likely to occur in low-lying areas underlain by permeable rocks. Groundwater flooding may take weeks or months to dissipate because groundwater flow is much slower than surface flow and water levels thus take much longer to fall. Based on available mapping, historic records, and site inspection, groundwater flooding is not identified as a significant risk at this location. 6.3.4 Coastal / Tidal Flooding Coastal or tidal flooding occurs due to high sea levels, storm surges or tidal interactions. The site is inland in Co. Monaghan and is not influenced by coastal processes. Therefore, coastal flooding is not considered a credible risk mechanism. RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 25 6.4 Benefiting Lands The application site is located within lands identified as Drainage District Benefiting Lands under the OPW Arterial Drainage Scheme. Benefiting Lands refer to lands that historically benefited from arterial drainage works and do not in themselves indicate the presence of flood risk or a functional floodplain. The designation of lands as Benefiting Lands under the OPW Arterial Drainage Scheme does not equate to functional floodplain status and does not in itself indicate that the lands are at risk of flooding. Based on available mapping and site inspection, there is no evidence that the application site forms part of an active floodplain. A review of OPW Floodinfo.ie mapping confirms that the site does not fall within any mapped 1% AEP (1 in 100 year) or 0.1% AEP (1 in 1000 year) fluvial flood extents. Furthermore, no evidence of floodplain connectivity, overban k flow, silt deposition, or flood-related scour was observed during the site inspection. 7.0 S-P-R MODEL The flood risk assessment has been undertaken using the Source–Pathway–Receptor model. Potential Sources: • Fluvial flooding from the existing drain • Pluvial (intense rainfall) events • Groundwater rise following prolonged rainfall Potential Pathways: • Overbank flow from adjacent drain • Surface water ponding during extreme rainfall • Subsurface groundwater migration Potential Receptors: • Proposed dwelling (FFL 56.00) • Access road Based on the review of national flood mapping datasets, topographical survey information, site inspection findings, and the site’s classification within Flood Zone C, no viable source–pathway–receptor linkage has been identified that would give rise to significant flood risk to the proposed development. The proposed Finished Floor Level (FFL) of 56.00m is set above surrounding ground levels and lies outside all mapped flood extents, providing an additional conservative allowance relative to potential extreme rainfall events. Figure 15: Source – Pathway – Receptor Model Source Pathway Receptor Storm Rainfall event (1 in 100 yr.) Enclosed Topographical Depressions Stormwater Fluvial Flooding Groundwater Flow Finished Floor Level of proposed/existing development. 56.00m Local Road Sewage Treatment Plant Third Party Properties RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 26 8.0 SUMMARY OF FINDINGS AND RECOMMENDATIONS 8.1 Flood Risk to Proposed Developments The proposed development: • Will not be at significant risk of flooding; • Will not exacerbate flooding in the immediate vicinity or wider area; • Will not obstruct or impede important flow paths; • Will not reduce flood storage capacity; • Will not result in residual risks that cannot be managed to an acceptable level. The proposed Finished Floor Level of 56.00m is located well outside mapped 1% and 0.1% AEP flood extents and provides an additional conservative allowance relative to surrounding ground levels. 8.2 Flood Risk to Adjacent Developments The development will not cause any direct increased flood risk to adjacent properties or land holdings as the ground level is not being raised. 8.3 Design Considerations/Mitigation Measures 8.3.1 Flood Storage Compensation No additional flood storage compensation is deemed necessary. 8.3.2 Drainage Design Surface water drainage design shall be in accordance with the requirements of Monaghan County Council Water Services Department and any additional codes of practice or guidelines as may be required. 8.3.3 Maintenance The developer is to ensure that maintenance of the site drainage which will include management of vegetation, cleaning of obstructions etc. is provided for as part of the overall management plan for the site. 8.3.4 Climate Change Allowance In accordance with the OPW Planning System and Flood Risk Management Guidelines (2009), consideration has been given to potential climate change impacts, including allowances for increased peak river flows (typically +20% under CFRAM guidance). The site is located within Flood Zone C and lies outside mapped 1% and 0.1% AEP flood extents. Even when applying a precautionary climate change allowance, the site remains outside predicted flood extents and does not form part of a functional floodplain. Accordingly, climate change does not alter the flood risk classification of the site and the proposed development remains appropriate from a flood risk perspective. Groundwater Levels Upgradient water Pluvial Flooding RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 27 9.0 CONCLUSIONS This Site-Specific Flood Risk Assessment has been prepared in accordance with the Planning System and Flood Risk Management Guidelines for Planning Authorities (2009). Based on: • Review of OPW Flood Hazard Mapping and Floodinfo.ie datasets, • CFRAM flood extent mapping, • Historical OSI mapping, • Site walkover inspection, • Topographical survey data, • Consideration of Benefiting Lands mapping, The site is located within Flood Zone C (Low Probability of Flooding). There is no mapped fluvial or pluvial flood extent affecting the site. The drain, located along the eastern boundary, is confined within defined banks and no evidence of overbank flooding was observed. The proposed development: • Is located within Flood Zone C (Low Probability of Flooding); • Is not affected by mapped fluvial or pluvial flood extents; • Will not increase flood risk elsewhere; • Will not obstruct flood flow paths or reduce flood storage; • Does not require the application of the Justification Test. Any residual risks are considered low and can be adequately managed through appropriate site drainage design, provision of the proposed Finished Floor Level, and ongoing maintenance of surface water infrastructure. This assessment satisfies the requirements of Section 15.22.8 of the Monaghan County Development Plan 2025–2031 and the Planning System and Flood Risk Management Guidelines for Planning Authorities (2009). Accordingly, the proposed development is appropriate at this location from a flood risk perspective. Signed: Nevin Traynor BSc. Env, H. Dip I.T, Cert SHWW. For Traynor Environmental Ltd FLOOD RISK ASSESSMENT COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX A – TOPOGRAPHICAL SURVEY RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 28 RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 29 RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 30 FLOOD RISK ASSESSMENT COMPLETED BY TRAYNOR ENVIRONMENTAL LTD APPENDIX B – SITE VISIT CARRIED OUT ON 12.02.26 RECEIVED: 13/05/2026 Flood Risk Assessment Laragh, Castleblayney, Co. Monaghan 31 Site Entrance View towards the proposed house Existing Drain in adjacent field Existing Drain along site boundary Proposed site area Proposed site area RECEIVED: 13/05/2026 RECEIVED: 13/05/2026