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Home My WebLink About2560353 - F.I. Received Doc. - Flood Risk Aassessment RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 1 FLOOD RISK ASSESSMENT FOR PROPOSED DEVELOPMENT SITE AT Moy Etra, Castleshane, Co. Monaghan Document No: ...................................... 22-148/FRA Issue No Description Made Checked Approved Date A Flood Risk Assessment -- -- -- 06/05/2026 RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 2 Contents 1.0 Introduction ..................................................................................................................................... 3 2.0 DETAILS/CLASSIFICATION OF THE PROPOSED DEVELOPMENT ....................................................... 3 3.0 Location and Description of Site ...................................................................................................... 4 STAGE 1 ASSESSMENT - FLOOD RISK INDENTIFICATION (SCREENING STAGE) ............................................. 6 4.1 Initial Assessment of Potential Sources of Flooding .................................................................... 6 4.2 Review of Available Data Sets ..................................................................................................... 7 4.3 Conclusion of the Stage 1 Assessment ........................................................................................ 8 5.0 STAGE 2 ASSESSMENT - INITIAL FLOOD RISK ASSESSMENT (SCOPING STAGE) ............................... 9 5.1 Confirmation of Sources of Flooding that may affect the Site .................................................... 9 5.2 Appraisal of the availability and adequacy of existing information ............................................ 9 5.3 Comparison of SFRA map to proposed layout and actual site topography .............................. 10 5.4 Impact of Flood Waters ............................................................................................................. 10 5.5 Flood Zone Classification of the Site.......................................................................................... 10 5.6 Appropriateness of the Proposed Development ....................................................................... 12 6.0 PROPOSALS FOR THE MANAGEMENT OF THE FLOOD RISK ........................................................... 13 7.0 COMMENSURATE ASSESSMENT OF THE RISK OF FLOODING ........................................................ 14 7.1 Likelihood of Building Flooding ................................................................................................. 14 7.2 Structural Damage to the Building ............................................................................................ 14 7.2.1 Foundations ............................................................................................................................... 14 7.2.2 Ground Floor Construction ........................................................................................................ 14 7.2.3 External Walls ............................................................................................................................ 14 7.3 Economic or Environmental Damage ........................................................................................ 15 7.4 Access to/from Site.................................................................................................................... 15 7.5 Danger to persons ..................................................................................................................... 15 7.6 Impact on existing Communal Flood Protection Infrastructure ................................................ 15 7.7 Impact of Flow Paths ................................................................................................................. 15 8.0 APPLICATION OF THE JUSTIFICATION TEST .................................................................................... 16 9.0 SUMMARY & CONCLUSION............................................................................................................ 17 RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 3 1.0 Introduction 1.1 This report is a Site-Specific Flood Risk Assessment for a proposed dwelling house at Moy Etra, Castleshane, County Monaghan. 1.2 The report has been carried out in accordance with, and takes into account, the following documents: • The Planning System and Flood Risk Management - Guidelines for Planning Authorities (November 2009) - DOEHLG and OPW • Planning Policy Guidelines for Flooding – OPW • Development and Flood Risk. Guidance for the Construction Industry - CIRIA C624 • Guidance for Assessing and Managing Flood Risk for New Developments (2005) – DEFRA (UK) 1.3 The principle reference document used is ‘The Planning System and Flood Risk Management - Guidelines for Planning Authorities (November 2009) published by DOEHLG and OPW. This document is referred to as ‘the Guidelines’ throughout the remainder of this report. 1.4 Each of these documents recommends that a staged approach should be adopted, carrying out only such appraisal or assessment as is needed for the purposes of decision-making at the appropriate level. 2.0 DETAILS/CLASSIFICATION OF THE PROPOSED DEVELOPMENT 2.1 The proposed development is a new dwelling house. The proposed site layout is shown on Fig.2.1 2.2 The proposed development type is classified as a ‘Highly Vulnerable Development’ in Table 3.1 of the ‘Planning System and Flood Risk Management – Guidelines for Planning Authorities’ (November 2009) published by the DOEHLG and OPW. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 4 Fig 2.1 – Proposed Site Layout 3.0 Location and Description of Site 3.1 The development site is located circa 2.0km south of Castleshane village as shown on Fig.3.1 while an aerial view of the site and surrounding area is shown on Fig. 3.2 3.2 The site has an area of circa 0.53Ha and is polygonal in shape. 3.3 The existing topography of the site is such that the land falls east to west toward an open channel to the front boundary of the site from 55m AOD to 47.0m AOD over a distance of circa 66.0m. The eastern/rear boundary is stepped, with the front boundary being formed by an open channel and the L1510 Public Roadway. Land to the north is made up of an existing dwelling house with land to the south agricultural. (Note: All levels throughout this report relate to the Malin Head datum) N Proposed House RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 5 3.4 The site is located c.65km (as the crow flies) inland from the Irish Sea. A stream flows south to north immediately to the front of the site and discharges into the Cor River c.760m to the north on the eastern side of the N2 roadway. Fig 3.1 – Location Map Site Location RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 6 Fig 3.2 – Aerial View of Site STAGE 1 ASSESSMENT - FLOOD RISK INDENTIFICATION (SCREENING STAGE) 4.1 Initial Assessment of Potential Sources of Flooding 4.1.1 Limited Fluvial Flooding is considered to be a possible flood risk at this stage of the assessment given that relative proximity of the site to the open channel. 4.1.2 Pluvial Flooding is not considered to be a possible flood risk at this stage of the assessment given the falling topography of the site and proximity to the open channel. 4.1.3 Coastal Flooding is not considered to be a possible flood risk at this stage of the assessment given the location of the site relative to the Irish Sea. 4.1.4 Groundwater Flooding is not considered to be a possible flood risk at this stage of the assessment given the presence of unproductive bedrock features in the area. Site Location RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 7 4.2 Review of Available Data Sets (a) Strategic Flood Risk Assessment Documents (SFRA) 4.2.1 Monaghan County Council in more recent times prepared a Strategic Flood Risk Assessment Report (SFRA) for Settlement Centres within the County Area 2019-2025. 4.2.2 The SFRA map (figure 4.1 below) presents the most up to date flood model for the open channel in this area. An undeveloped and unhabitable, low lying narrow strip of the subject site appears to potentially be in proximity to the predicated flood zone A. Fig 4.1 – Extract PFRA Mapping (Monaghan Co Co) (b) Historic Flood Event Data 4.2.3 Historic Flood Event Data is available via the OPW flood mapping website www.floodmaps.ie. The available data provides historical evidence of flooding having occurred during extreme conditions. There are no recorded flood events in the vicinity of the subject site. (c) Visual Inspection and Site Survey 4.2.4 The site was inspected on 17/02/2026. The site is currently lying idle and is covered in grass. No flooding was evident during the site inspection. 4.2.5 A view of the site, looking towards the east from the public roadway is shown on Fig. 4.2 RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 8 Fig. 4.2 – Image of site from public roadway 4.3 Conclusion of the Stage 1 Assessment 4.3.1 No firm evidence of actual flooding having occurred at the site in the past has been found. 4.3.2 The SFRA map indicates that it is possible to rule out coastal flooding as well as pluvial and groundwater flooding. 4.3.3 The SFRA map indicates that a limited section of a low lying portion of the subject site to the front may potentially be subject to flooding under the 1 in 100 event. 4.3.7 It is therefore concluded that the assessment should proceed onto Stage 2 (Scoping Stage) and concentrate on the potential of the site being subject to fluvial flooding from the open channel that runs to the front of the site during extreme events. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 9 5.0 STAGE 2 ASSESSMENT - INITIAL FLOOD RISK ASSESSMENT (SCOPING STAGE) 5.1 Confirmation of Sources of Flooding that may affect the Site 5.1.1 The Stage 1 Assessment has identified pluvial flooding as the most likely potential sources of flooding that could affect the site. 5.1.2 The identified source and pathway for this flooding are: Source of Flooding Pathway Exceptionally high and prolonged rainfall High flows in the open channel exceeding the channel banks and overflowing onto surrounding lands 5.2 Appraisal of the availability and adequacy of existing information 5.2.1 The most relevant items of available information are considered to be the: a) Monaghan County Council SFRA map b) Topographical Survey 5.2.2 Monaghan County Council’s Strategic Flood Risk Assessment (SFRA) was undertaken in 2018 to inform and assist in the preparation of the Monaghan County Council Development Plan. These maps indicate the extent of the predicted fluvial flooding and pluvial Flooding. 5.2.3 However the SFRA maps are based on a LiDAR Topographical survey and should be recognized as being preliminary only and not to be fully accurate at a local level. 5.2.4 The topographical survey of the site offers concise and highly accurate details of ground levels throughout the site and surrounding lands. The topographical survey therefore represents an important site-specific data set which shall allow a more accurate determination of the location and extent of flooding that may occur during extreme and prolonged rainfall events in conjunction with the SFRA map. 5.2.5 It is therefore proposed in order to determine the location and extent of fluvial flooding, if any, to use these data sources to compare the SFRA model extents to the actual contours of the site from the topographical survey. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 10 5.3 Comparison of SFRA map to proposed layout and actual site topography 5.3.1 Upon initial review, it would appear that the modelled flooding seems to reflect the topography in this area. The open channel is represented by 2no blue lines with the site boundary in red. The majority of the flooding associated with the 100 year event (green hatch) inside the subject site red line lies within the bounds of the open channel with some minor overflow for the 1 in 1000 year event depicted in yellow hatching as shown in figure 5.1 below. The 1 in 1000 year event is limited to approximate 1m strip of the sit along the stream. Fig. 5.1 – Initial review of SFRA fluvial map and site survey 5.4 Impact of Flood Waters 5.4.1 Upon initial review, comparing Monaghan County Council’s SFRA fluvial flood map extents with the site specific topographical survey, that the modelled flood extents does not interact with the proposed development. 5.5 Flood Zone Classification of the Site 5.5.1 The Planning Policy Guidelines for Flooding define three levels of fluvial flood zones as follows: • Zone A – probability of flooding is greater than 1 in 100 years RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 11 • Zone B – probability of flooding is between 1 in 100 years and 1 in 1000 years • Zone C – probability of flooding is less than 1 in 1000 years 5.5.2 On this basis, the majority of the actual “usable” part of the site .i.e. not the open water channel, appears to lie in Flood Zone C. With a small portion to the front boundary, parallel to the open channel and adjacent to the site entrance (which is shared with the existing dwelling to the north) appears to lie within Flood Zone B and the open channel itself containing the majority of Flood Zone A. Fig. 5.2 – Flood map, topographical survey and proposed layout 5.5.3 Upon closer assessment of the existing/proposed shared entrance area and its interaction with the modelled flood extents, the fall of the open channel and indeed surrounding topography falls continuously south to north. While the flood model indicates flooding for the 1 in 100 year event at the entrance, this flooding may/may not actually happen in this area. The flood model was developed using LIDAR measurements and the model may not have picked up the existence of this channel crossing/entrance when showing flooding in RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 12 the channel at this location. However, if this entrance should flood, from the levels highlighted in Figure 5.3 below, flood depths will be in the order of c.200mm in extreme events before naturally draining north as the flood waters retreat. This depth of water should not impact on access to the proposed property. Fig. 5.3 – Existing/Proposed shared entrance levels and modelled flood map 5.6 Appropriateness of the Proposed Development 5.6.1 The consequences of flooding in general include: risks to persons who will use the development; the damage to buildings and structures and the potential environmental damage. 5.6.2 The Guidelines recognize that the extent of the consequences of flooding are highly dependent on the development type and Table 3.1 accordingly groups development types into three different classes as follows: • Highly Vulnerable Development • Less Vulnerable Development • Water –compatible Development 5.6.3 The proposed residential development of can be classified as ‘a highly vulnerable development’ as per Table 3.1 of the Guidelines. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 13 5.6.4 Table 3.2 of the Guidelines (reproduced as Table 5.1 of this report) provides a matrix of vulnerability versus flood zone which defines what type of development can be considered as being ‘appropriate’ for a particular flood zone and what type of development must satisfy a ‘Justification Test’ before it can be deemed suitable. 5.6.5 In this particular case, based on Monaghan County Council’s SFRA map and the site specific topographical survey, it is our opinion that the proposed development does NOT need to satisfy the criteria set out in the Justification Test for Development Management (Box 5.1 of the Flood Guidelines) and is deemed ‘APPROPRIATE’ development as per the Flood Management Guidelines. Table 5.1 – Determination of the Appropriateness of the Development (Source: Table 3.2 of the Flood Guidelines) 6.0 PROPOSALS FOR THE MANAGEMENT OF THE FLOOD RISK 6.1 Under new build circumstances, Monaghan County Council require a freeboard of 0.5m from the top flood level to the proposed finished floor level. With a 1in 1000 year top of water flood value of c.47.5m AOD based on the SFRA map and the site specific topographical survey, this would suggest a minimum FFL of 48.0m. 6.4 In this regard and based on existing site levels and the positioning of the proposed dwelling, a finished floor level of 54.25m is being proposed. This proposed level is 6.25m above Monaghan County Council’s SFRA suggested 1000 year fluvial flood levels of c.47.50m. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 14 7.0 COMMENSURATE ASSESSMENT OF THE RISK OF FLOODING 7.1 Likelihood of Building Flooding 7.1.1 The SFRA Flood Maps are based on local rainfall data and topography. 7.1.2 From this, flood extents maps are then generated based on LIDAR surveys of the area input into the model. The use of LIDAR would lead one to use the maps as indicative only. 7.1.3 As per section 5 and 6 above, taking into account the actual local site specific topography in conjunction with Monaghan County Council’s SFRA map, the modelled 1 in 1000 year fluvial flood event (Flood Zone B) does not extend into the actual usable space within the subject site. 7.1.4 With a suggested finished floor level in the order of 54.25m, this will put the proposed dwelling above the required 500mm above the SFRA assumed top water fluvial flood level. 7.2 Structural Damage to the Building While there is a considerable elevation difference between the open channel and the proposed FFL, the client may wish to consider that the following water resilient construction features be incorporated into the design of the foundations and floor of the house: 7.2.1 Foundations Concrete blocks used to construct the ‘dead building’ should be sealed with an impermeable material or encased in concrete to prevent water movement from the ground to the wall construction. 7.2.2 Ground Floor Construction • Floors should be ground-bearing non-reinforced 150mm thick concrete floor slabs • A Damp Proof Membrane (min. 1200 gauge) should be placed above the hardcore blinding to minimise the passage of water through ground floors. • Floor insulation should be of the closed-cell type 7.2.3 External Walls • Avoid Timber frame walls • Avoid Brick walls or use engineering grade brick to 0.3m above flood level • Apply external cement based render, preferably with lime content, to blockwork • Cavity insulation should incorporate rigid closed cell materials • Use stainless steel cavity ties • Avoid standard gypsum plasterboard - Apply internal cement based render and plaster, preferably with lime content. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 15 7.3 Economic or Environmental Damage 7.3.1 The FL of the development shall be set above the existing ground levels and SFRA suggested flood levels. This is considered to represent reasonable protection against the likelihood of flood waters entering the house and causing damage to its structure/building fabric or to the contents contained within it. 7.3.2 The possible adoption of ‘water resilient’ construction methods shall ensure construction methods shall ensure that the economic damage caused by any flooding that may occur is minimised. 7.3.3 Overall the economic consequences of flooding of the site are considered to be negligible. 7.3.4 The possibility of sea water contamination of a well (if present) providing drinking water is not an issue in this case. 7.3.5 It is not proposed to carry out any environmental sensitive activity nor to store hazardous material at the site. 7.4 Access to/from Site 7.4.1 Existing/proposed access to/from the site shall not be prevented during current 1.0% AEP Flood event. 7.5 Danger to persons 7.5.1 With a floor level to be set above the current and future SFRA 0.1% flood event top water level, danger to persons is not a concern. 7.6 Impact on existing Communal Flood Protection Infrastructure 7.6.1 Existing flood protection measures shall not be impacted upon by the proposed development. 7.7 Impact of Flow Paths 7.7.1 The location of the building shall have no material impact on flow paths or cause the displacement of flood waters onto other lands. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 16 8.0 APPLICATION OF THE JUSTIFICATION TEST 8.1 Albeit the flood risk assessment would suggest that the SFRA map indicates that the site is located within Flood Zone C for fluvial flooding. For thoroughness, it is therefore suggested to demonstrate that the proposed development satisfies all of the criteria of the Justification Test as it applies to development management as outlined in Box. 5.1 of the Guidelines. 8.2 Criterion No.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 into account these Guidelines. 8.2.1 It is considered that the proposed small residential development fully meets the planning objectives and represents a permitted use for the zoning of the subject lands in the Development Plan. 8.3 Criterion No.2 (i) The development proposed will not increase flood risk elsewhere and, if practicable, will reduce overall flood risk 8.3.1 It is not proposed to alter the existing ground levels on site and it is anticipated that the positioning of the proposed development shall be outside extents of the standard 1 in 100 year pluvial flood as per sections 5 and 6 above. It is also noted that the proposed development has incorporated an BRE365 infiltration soakaway to address all surface waters, therefore, any hardstand surface water proposed by the development will not be directed to the stream but to an infiltration soakaway. The proposed development shall therefore not increase flood risk elsewhere. (ii) The development proposed includes measures to minimize flood risk to people, property, the economy and the environment as far as is reasonably possible 8.3.2 The finished floor level of 54.25m will be set approx 6.25m above the top water flood level of the 0.1% fluvial flood. This measure should ensure that the flood risk to people, property, the economy and the environment is reduced and shall be exceptionally low. (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 8.3.3 The proposed development shall not adversely impact the effectiveness of any protection measures nor block access to/from any such measures for maintenance purposes. 8.3.4 The development shall have no impact on existing emergency services access to the area. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 17 (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 8.3.5 The proposed development shall support the proper planning in a rural node setting. 9.0 SUMMARY & CONCLUSION 9.1 The proposed development is a ‘highly vulnerable development’ from a flood risk perspective. 9.2 Screening Assessment shows that the site is in close proximity to 1 in 100 year fluvial flooding as per Monaghan County Council SFRA Map. 9.3 Scoping Assessment and closer examination of the site specific topographical survey and SFRA Map shows that the map flood extents does not extend into the subject site. 9.4 In this regard, based on Monaghan County Council’s SFRA map and a site specific topographical survey, the main site associated with this development is considered to be located in Flood Zone C. 9.5 The proposed floor level shall be set in the order of 54.25m, some 6.25m above the anticipated top water flood level of the 1 in 1000 year event based on the SFRA map. 9.6 A commensurate assessment of the risks of flooding associated with the development concludes that: • The proposed building shall not flood under the future 1.0% AEP flood event. • The economic and environmental impact of any flooding shall be minimal. • Access to/from the site shall remain possible even during a 1.0% AEP flood event. • The proposed development shall have no impact on the management of, or access to, existing communal flood protection measures. 9.7 The proposed development is deemed to be ‘appropriate development’ based on Table 3.2 of the Flood Management Guidelines and applying Monaghan County Council’s SFRA map relative to the site specific topographical survey. 9.8 A Justification test was carried out on the proposed development for completeness. The proposed development meets all of the Criteria set out in the Justification test. 9.9 The proposed development will have no affect on or exacerbate flooding in the immediate vicinity or wider area. RECEIVED: 08/05/2026 Cathal McGlone Flood Risk Assessment Coyle Civil & Structural May 2026 Page 18 9.10 In summary it is concluded that the proposed development meets the aims and objectives of the ‘Planning System and Flood Risk Management Guidelines’ and shall not represent an unacceptable flooding risk nor exacerbate flooding in the immediate vicinity or wider area. RECEIVED: 08/05/2026 RECEIVED: 08/05/2026