Last edited 28 May 2021


A floodplain is land adjacent to a watercourse over which water flows or would flow in times of flood, if defences were not in place.

The flood zone area classification system devised by the Environment Agency refers to:

Ref The HS2 London-West Midlands Environmental Statement, Department for Transport, November 2013.

NB Culvert, screen and outfall manual, (CIRIA C786) published by CIRIA in 2019, defines a floodplain as: ‘Land on either side of a river that is below the highest defined flood level.’

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