“De facto defence A structure that provides a flood defence function but for which flood defence is a secondary or indirect purpose.” “Formal defence A formal defence asset that directly limits the spread of flood water and, primarily because of this function, is owned and/or maintained by its present owner, regardless of whether this is the Environment Agency, another authority or a private owner.”
“This policy defines what is included on the Flood Map. The Flood Map comprises the following data: 1. Flood Zones Flood Zones are areas which could be affected in the event of flooding from rivers ... Flood zones ignore the presence of the following types of flood defence and structures: • Raised walls and embankments • Barriers, barrages and gates • Engineered or controlled flood storage areas • Pumping stations Other infrastructure, including bridges, culverts, engineered channels and bypass channels, and embankments (e.g. railway or road embankments) that are not flood defences, is included in all modelling and mapping of flood zones (apart from our national generalised modelling produced in 2004). The Flood Zones policy statement details the purpose and development of flood zones. 2. Flood Defences The Flood Map shows the location of the following types of flood defences: • Raised walls and embankments • Tidal barriers and barrages • Engineered or controlled flood storage areas • Pumping stations All other types of flood defences or structures, or natural or manmade infrastructure, including bridges, culverts, engineered channels and bypass channels, embankments that are not flood defences, and natural washlands, are not shown on the Flood Map.”
“Policy Flood Zones show areas of land that could flood from rivers and/or from the sea. They identify the extents over which flooding could occur, if the flooding is not constrained by flood defences.”
“Flood defence infrastructure, such as flood walls and embankments, intended to protect an area against flooding to a specified standard of protection.” “Standard of protection: The design event or standard to which a building, asset or area is protected against flooding, generally expressed as an annual exceedance probability.”
“37. Canals, as inland waterways, operate differently to rivers and other watercourses as defined under the Land Drainage 1991. While some will fall within river or coastal flood plains, others will be outside flood-risk areas. Generally, canals have a limited number of feeders, which are often controlled so that they can be diverted away from the canal at times of flood. Sluices are controlled to discharge excess water from the canal during periods of high inflow to insure that water levels do not exceed the freeboard and overtop to flood adjacent land. Canals also have some ability to store water before it is discharged, attenuating flood peaks and reducing the potential for flooding. In some cases, canals cross river catchment boundaries, and water could be accepted in one catchment and discharged in another. 38. The implications for development are twofold. Firstly, since the concept of a flood plain is not applicable, waterside development or redevelopment of previously developed land may not face the same flood-risk constraints as development alongside a river. Canals may thus retain their potential to act as catalysts for urban and rural regeneration”
“4.1 Water Level Under normal flow conditions in the Canal the sluice’s automatic control system is designed to control the water levels within the Canal to enable safe navigation of vessels using the Port. In achieving this, water levels are maintained so that the risk of flooding is also minimised”