The Lead Local Flood Authority in Oxfordshire is Oxfordshire County Council.

Main River

Main rivers are a statutory type of watercourse in England and Wales and are usually larger streams and rivers. A main river is defined as such on the Environment Agency’s Main River map, and can include any structure or appliance for controlling or regulating the flow of water in, into or out of a main river. The Environment Agency’s powers to carry out flood defence works apply to Main Rivers only. See our Flood Risk Map for a list of all Oxfordshire main rivers.

National Planning Policy Framework

The National Planning Policy Framework sets out government’s planning policies for England and how these are expected to be applied. The framework acts as guidance for local planning authorities and decision-takers, both in drawing up plans and making decisions about planning applications.

Ordinary Watercourse

Any watercourse not defined by the Environment Agency as a main river. Ordinary watercourses are generally smaller than main rivers, and can include streams, ditches and piped watercourses. See our Flood Risk Map for a map of all Oxfordshire main rivers.

Preliminary Flood Risk Assessment

The Preliminary Flood Risk Assessment (PFRA) provides an overview of past floods and the possible harmful consequences of future floods, leading to the identification of Areas of Significant Risk. The floods to be included are those which had significant harmful consequences for human health, economic activity or the environment (including cultural heritage), or which would have significant harmful consequences for those matters if they were to occur now.

Residual Risk

Residual risks are those remaining after actions have been taken to mitigate or defend against flood risk. Examples of residual flood risk include: the failure of flood management infrastructure such as a breach of a raised flood defence, blockage of a surface water conveyance system, overtopping of an upstream storage area, or failure of a pumped drainage system; failure of a reservoir; or a severe flood event that exceeds a flood management design standard, such as a flood that overtops a raised flood defence, or an intense rainfall event which the drainage system cannot cope with.

Riparian Owner/Responsibility

All landowners and tenants whose property has a watercourse within or adjacent to the boundaries of their land, are riparian owners of that watercourse. Riparian owners have a responsibility for maintaining the watercourse and bank, clearing debris and keeping any ditches or structures clear. This ownership extends to watercourses that are piped (culverted) under the land.


A sewer is a pipe which carries and removes either rainwater (surface water runoff), foul water (from toilets, sinks etc) or a combination of both. A sewer can be categorised as either a private or public sewer. A private sewer is solely the responsibility of the occupiers/owners of the properties that it serves. A public sewer is a sewer that has been adopted and maintained by a Sewerage Undertaker.

Strategic Flood Risk Assessment

Strategic Flood Risk Assessments (SFRAs) are studies carried out by one or more local planning authorities to assess the risk to an area from flooding from all sources, now and in the future. An SFRA takes into account the impacts of climate change and assesses the impact that land use changes and development in the area will have on flood risk. They are background evidence-based documents which inform the Local Development Framework.

Surface Water Management Plans

A long-term action plan to manage surface water in an area and should influence future capital investment, drainage maintenance, public engagement and understanding, land-use planning, emergency planning and future developments.

Sustainable Drainage Systems

Methods of management practices and control structures that are designed to drain surface water in a more sustainable manner than conventional techniques. These include permeable surfaces, swales, wetlands and ponds.

Water Framework Directive

The Water Framework Directive was introduced in December 2000 and became UK law in December 2003. The directive focuses on improving the ecology of our water ecosystems and aims to protect and enhance the quality of surface water, groundwater, estuaries and coastal waters. The Environment Agency are the lead authority responsible for the delivery of these targets, but must work closely with lead local flood authorities, such as the County Council, to ensure that targets are achieved.


A watercourse is any channel through which water flows. The channel can be natural or man-made. It can be above or below ground and does not have to contain water all year round.


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