Date: 06 Jan 2023
Indicative fluvial flood maps through the National Indicative Fluvial Mapping Project
The OPW, as lead agency for flood risk management in Ireland, have updated OPW datasets that are available for use in the preparation of spatial plans.
Indicative fluvial flood maps have been prepared for all watercourses in the country with a catchment greater than 5km2 through the National Indicative Fluvial Mapping (NIFM) project that was completed in 2020.
National Indicative Fluvial Maps (NIFM)
These maps provide important flood hazard information for areas not covered under the National CFRAM Programme, and were developed using much more robust analysis than that used previously to prepare the PFRA indicative mapping.
However, the maps did not make use of channel survey data, and do not take flood defences into account. These maps have been prepared for two potential future scenarios taking account of the potential impact of climate change; the Mid-Range future Scenario (MRFS) and High-End Future Scenario (HEFS), as well as for current conditions.
The updated indicative flood mapping were prepared for the purpose of an initial assessment, at a national level, to assist in the review of areas of potentially significant flood risk, as required by the EU 'Floods' Directive 2007/60/EC. They provide only an indication of areas that may be prone to flooding and are therefore not necessarily locally accurate.
As such, while the indicative maps may be used for strategic-level assessments, they should not be used:
- To assess the flood hazard and risk associated with individual properties or point locations, or to replace a detailed flood risk assessment, or,
- As the sole basis for defining the Flood Zones, or for making planning policy and development management decisions.
Further user guidance and details on the preparation of the NIFM outputs and mapping are available at: https://www.floodinfo.ie/publications/?t=50 and https://www.floodinfo.ie/map/nifm_user_guidance_notes/.
National Coastal Flood Hazard Maps
The national scale coastal flood hazard maps from the ICPSS project that were published by OPW under the PFRA in 2012 are now superseded by the outputs of the National Coastal Flood Hazard Mapping (NCFHM) 2021 project and these updated coastal flood hazard maps have recently been published on the www.floodinfo.ie web portal.
These coastal flood hazard maps, for both flood extent and depth, have been produced for a range of annual exceedance probabilities for the Present Day as well as for multiple Future Scenarios (including: MRFS, HEFS, H+EFS and H++EFS).
The maps show the worst case scenario as any flood defences potentially protecting the coastal floodplain are not taken into account, and so are in-line with the definition of the Flood Zones as set out in the Guidelines.
The NCFHM maps are based on more up-to-date estimates of extreme coastal levels than those used for the CFRAM coastal maps (that were based on the ICPSS data). As such the NCFHM maps may be considered in preference to the CFRAM with regards to the definition of the Flood Zones.
Further user guidance and details on the preparation of the NCFHM 2021 project outputs and mapping are available at: https://www.floodinfo.ie/publications/?t=48.
These datasets, including those for potential future scenarios taking account of the possible impacts of climate change, are available to view on the OPW portal, www.floodinfo.ie, and may be obtained in GIS format from the OPW Data Management Section via email (email@example.com).
Any queries in relation to the use of OPW datasets to produce flood zones in the preparation of development and local area plans can be directed to firstname.lastname@example.org.