Glossary - Flood Risk Planning Terms

AEP Annual Exceedance Probability – The annual probability of a flood exceeding the peak floodwater level. Culvert a structure with integral sides, soffit and invert, including a pipe that contains a watercourse as it passes through a 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 Coastal Flooding flooding from sea water, often arising through storm surge 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). Drainage Infrastructure equipment such as culverts, weirs and sluices provided to facilitate drainage 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 Hazard the features of flooding which have harmful impacts on people, property or the environment (such as the depth of water, speed of flow, rate of onset, duration, water quality etc). Floodplain 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 the 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 Risk / Inundation Areas areas susceptible to flooding from the 4 main sources, ie rivers, the sea, surface water and reservoirs