AEP: Annual Exceedance Probability is the probability that a given rainfall total accumulated over a given duration will be exceeded in any one year.

Arterial Drainage Scheme: Works undertaken under the Arterial Drainage Act. Such works were undertaken, and are maintained on an ongoing basis, by the OPW

Catchment Flood Risk Assessment and Management Study Or CFRAM Study: A study to assess and map the existing and potential future flood hazard and risk from fluvial and coastal waters, and to define objectives for the management of the identified risks and prepare a Plan setting out a prioritised set of measures aimed at meeting the defined objectives.

Communities: Cities, towns, villages or townlands where there are a collection of homes, businesses and other properties

Consequences: The impacts of flooding, which may be direct (e.g., physical injury or damage to a property or monument), a disruption (e.g., loss of electricity supply or blockage of a road) or indirect (e.g., stress for affected people or loss of business for affected commerce)

Drainage: Works to remove or facilitate the removal of surface or sub-surface water, e.g., from roads and urban areas through urban storm-water drainage systems, or from land through drainage channels or watercourses that have been deepened or increased in capacity.

Flood: The temporary covering by water of land that is not normally covered by water.

Flood Extent: The extent of land that has been, or might be, flooded. Flood extent is often represented on a flood map.

Flood Hazard Map: A map indicating areas of land that may be prone to flooding, referred to as a flood extent map, or a map indicating the depth, velocity or other aspect of flooding or flood waters for a given flood event. Flood hazard maps are typically prepared for either a past event or for (a) potential future flood event(s) of a given probability.

Flood Risk Management Plan (Plan): A Plan setting out a prioritised set of measures within a long-term sustainable strategy aimed at achieving defined flood risk management objectives. The Plan is developed at a River Basin (Unit of Management) scale, but is focused on managing risk within the AFAs.

Flood Risk Map: A map showing the potential risks associated with flooding. These maps may indicate a particular aspect of risk, taking into account the probability of flooding (e.g., annual average economic damages), but can also show the various receptors that could be affected by floods of different probabilities.

Floodplain: The area of land adjacent to a river or coastal reach that is prone to periodic flooding from that river or the sea.

Floods Directive: The EU ‘Floods’ Directive [2007/60/EC] is the Directive that came into force in November 2007 requiring Member States to undertake a PFRA to identify Areas for Further Assessment (AFAs), and then to prepare flood maps and Plans for these areas.

Fluvial: Riverine, often used in the context of fluvial flooding, i.e., flooding from rivers, streams, etc.

Habitats Directive: The Habitats Directive [92/43/EEC] aims at securing biodiversity through the provision of protection for animal and plant species and habitat types of European importance.

Hazard: Something that can cause harm or detrimental consequences. In this context, the hazard referred to is flooding.

Hydraulics: The science of the behaviour of fluids, often used in this context in relation to estimating the conveyance of flood water in river channels or structures (such as culverts) or overland to determine flood levels or extents.

Hydrology: The science of the natural water cycle, often used in this context in relation to estimating the rate and volume of rainfall flowing off the land and of flood flows in rivers.

Hydrometric Area: Hydrological divisions of land, generally large catchments or a conglomeration of small catchments, and associated coastal areas. There are 40 Hydrometric Areas in the island of Ireland.

Measure: A measure (when used in the context of a flood risk management measure) is a set of works, structural and / or non-structural, aimed at reducing or managing flood risk.

National CFRAM Programme: The programme developed by the OPW to implement key aspects of the EU ‘Floods’ Directive in Ireland, which included the CFRAM Studies, and built on the findings of the PFRA.

Pluvial: Refers to rainfall, often used in the context of pluvial flooding, i.e., flooding caused directly from heavy rainfall events (rather than over-flowing rivers).

Public Consultation Day Or PCD: A public and stakeholder consultation and engagement event advertised in advance, where the project team displayed and presented material (e.g., flood maps, flood risk management options) at a venue within a community, with staff available to explain and discuss the material, and where members of the community and other interested parties could provide local information and put forward their views.

Return Period: A term that was used to describe the probability of a flood event, expressed as the interval in the number of years that, on average over a long period of time, a certain magnitude of flood would be expected to occur. This term has been replaced by ‘Annual Exceedance Probability, as Return Period can be misleading.

Risk: The combination of the probability of flooding, and the consequences of a flood.

River Basin: An area of land (catchment) draining to a particular estuary or reach of coastline.

Riverine: Related to a river.

Significant Risk: Flood risk that is of particular concern nationally. The PFRA Main Report sets out how significant risk was determined for the PFRA, and hence how Areas for Further Assessment have been identified.

Standard of Protection Or SoP: The magnitude of flood, often defined by the annual probability of that flood occurring being exceeded (the Annual Exceedance Probability, or ‘AEP’), that a measure / works is designed to protect the area at risk against.

Strategic Environmental Assessment Or SEA: An SEA is an environmental assessment of plans (such as the Plans) and programmes to ensure a high level consideration of environmental issues in the plan preparation and adoption, and is a requirement provided for under the SEA directive [2001/42/EC].

Surface Water:  Water on the surface of the land. Often used to refer to ponding of rainfall unable to drain away or infiltrate into the soil.

Survey Management Project: A project commissioned by the OPW in advance of the CFRAM Studies to specify and manage a large proportion of the survey work.

Sustainability: The capacity to endure. Often used in an environmental context or in relation to climate change, but with reference to actions people and society may take.

Tidal: Related to the tides of the sea / oceans, often used in the context of tidal flooding, i.e., flooding caused from high sea or estuarine levels.

Topography: The shape of the land, e.g., where land rises or is flat.

Unit of Management Or UoM: A hydrological division of land defined for the purposes of the Floods Directive. One Plan has been prepared for each Unit of Management, which is referred to within the Plan as a River Basin.

Vulnerability: The potential degree of damage to a receptor (see above), and/or the degree of consequences, that could arise in the event of a flood.

Water Framework Directive Or WFD: The Water Framework Directive [2000/60/EC] aims to protect surface, transitional, coastal and ground waters to protect and enhance the aquatic environment and ecosystems and promote sustainable use of water resources.

Waterbody: A term used in the Water Framework Directive (see below) to describe discrete section of rivers, lakes, estuaries, the sea, groundwater and other bodies of water.