Abstract: These statistics have become what are now known as physical catchment descriptors (PCDs). A PCD describes a characteristic of a catchment as a single number. A list of the most commonly used PCDs in the FSU methodologies are summarised as follows; Catchment Area (AREA), Standard Period Average Annual Rainfall (SAAR), Baseflow Index derived from Soils (BFIsoil), Flood Attenuation from Reservoirs and Lakes (FARL), Drain Density (DRAIND), Mainstream Slope (S1085), Arterial Drainage Index (ARTDRAIN2) and Proportion of Urban Landcover Extent (URBEXT).

Lineage: When the FSU Programme was originally launched, 216 flow gauging stations were used. After further detailed analysis of Irish gauging stations in 2025 under the Flood Estimation Methodologies for Ireland (FEMI) research, it was decided to use a smaller dataset of 134 gauging stations that met new suitability criteria. More information can be found on https://www.gov.ie/en/office-of-public-works/collections/flood-studies-update-fsu-programme/

Purpose: The data has been developed to inform the Flood Studies Update (FSU) Programme. The FSU is a programme of research and development, undertaken by the Office of Public Works (OPW), to provide improved methods of extreme rainfall and flood estimation at both gauged and ungauged river locations in the Republic of Ireland.