Northern Ireland Planning Service

PPS 15: Planning and Flood Risk
Glossary

Biodiversity - (Biological Diversity) the total variety of all living things
Ecosystem - a living community of interacting plants and animals and their physical environment
Culvert - a structure with integral sides, soffit and invert, including a pipe that contains a watercourse as it passes through or beneath a road, railway, building, embankment etc, or below ground
Catchment - the area drained, either naturally or with artificial assistance, by a watercourse, including all drainage channels, tributaries, floodplains, estuaries and areas of water storage
Drainage - assessment a statement of the drainage issues relevant to a development proposal and the measures to provide the appropriate standard of drainage. The detail of the assessment will be proportionate to the nature of the proposal. (It may also be called a Drainage Impact Assessment
Flood defence - a structure or works designed to prevent the inundation of land and property from watercourses and/or the sea. Such defences may take the form of floodwalls or embankments or the management of water levels through drainage works
Flood plain - the generally flat areas adjacent to a watercourse or the sea where water flows in time of flood or would flow but for the presence of flood defences. The limits of floodplain are defined by the peak water level of an appropriate return period event
Flood Risk - the statistical probability of an event occurring combined with the scale of the potential consequences of that event
Flood storage - an area, usually within floodplain where water is stored in time of flood
Freeboard - a height added to the predicted level of flood to take account of waves or turbulence and the uncertainty in estimating the probability of flooding
Groundwater - water below the surface of the ground in the saturation zone and in direct contact with the ground or subsoil
Habitat - the natural home of a plant or animal
Pondage - see Flood Storage
River basin - see catchment
Run-off - that proportion of rainfall which is not absorbed into the ground and finds its way into watercourses, eventually flowing to the sea
Storm surge - the increase in sea level caused by the combined effects of low atmospheric pressure, wind and a high tide
Surcharging - a flow of water in a culvert or pipe which is above the design flow
Watercourse - a river, stream, canal, ditch, drain, cut, culvert, dyke, sluice, valve, overland carrier, millrace or layde. Water mains and sewers are not included in this definition
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