Benefit-cost analysis
A comparison of present value coastal defence scheme benefits and costs as part of an economic appraisal. The benefit-cost ratio is the total present value benefits divided by the total present value costs.

Breakwater
A rock or concrete armour-faced structure which may be aligned normal or parallel to the coastline.

Breastwork
Vertical or raking timber or steel-piled structures supporting horizontal planking and containing a rock infill.

Climate Change
Long-term changes in climate specifically linked to those changes resulting from human intervention in atmospheric processes through, for example, the release of greenhouse gases to the atmosphere from the burning of fossil fuels.

Coastal defence
A term used to encompass both coastal protection against erosion and sea defence against flooding.

Coastal process unit
A length of shoreline in which the physical processes are relatively independent from the processes operating in the adjacent coastal process units. For management purposes, coastal process units provide the framework for considering the potential wider impacts of policies in a particular management unit(s) on the adjacent shoreline. Where Strategy Plans are to be developed following Shoreline Management Plan (SMP) completion, they may be on the basis of a coastal process unit.

Coastal squeeze
The process by which the coastal habitats and natural features are progressively lost or drowned, trapped between coastal defences and rising sea levels.

Competent Authority
In relation to the Habitats Regulations, a Competent Authority is any Minister, Government Department, public or statutory undertaker, public body of any description or person holding public office. For a coastal defence project, this includes at least the following organisations: the Local Planning Authority (which decides on planning permission), the Operating Authority (which makes decisions about the design), and, if it has to decide whether to fund a scheme, Defra/National Assembly for Wales .

Downdrift effects
Impacts occurring in the lee of any coastal activity resulting from associated changes to coastal processes, particularly sediment supply.

Erosion
The loss of land or encroachment by the sea through a combination of wave attack and, in the case of coastal cliffs, slope processes (e.g. high groundwater levels). This may include cliff instability, where coastal processes result in the periodic reactivation of landslide systems or promote rock falls.

Flood defence
A structure which protects against flooding, by rivers as well as by the sea, or the activity of providing protection against flooding by management of flood defences and flood warning

Flooding
Refers to inundation by water whether this is caused by breaches, overtopping of banks or defences or by inadequate drainage of rainfall or underlying groundwater levels.

Gabion mattress
Rock filled mesh baskets or linked pre-cast concrete units which act as a defence against scour.

Groynes
Structures in rock and timber generally perpendicular to the shoreline used to control beach material movement.

Hard defences
Structures such as walls or banks designed to contain rivers or the energy of waves and tide.

High-Level Targets
Targets set for Operating Authorities by Defra to ensure and demonstrate the delivery of the Government's stated policy aims and objectives for flood and coastal defence.

Maintenance
Refers to the activities involved in keeping coastal defence structures such as flood banks, walls, gates, etc. in a defined operational state, and in keeping the hydraulic performance of watercourses within defined limits. It does not refer to improvements to such works to maintain the same level of protection against a new or increased risk .

Managed realignment
The management of a process of establishing a new coastal defence line, often set back from the existing position, with the aim of improving the long-term sustainability of the coastal defence, or contributing to other aims such as habitat creation.

Operating Authority
A body with statutory powers to undertake flood defence or coast protection activities, usually a maritime District Council or Unitary Authority or the Environment Agency.

Physical processes
Coastal phenomena such as sediment transport, erosion and accretion responsible for shaping the coast and underpinning its dynamic qualities; it refers to geological/earth science processes only.

Planning Policy Guidance
A series of notes issued by the government setting out national policy guidance on planning issues, such as the countryside, nature conservation, coastal planning, unstable ground, etc.

Precautionary principle
An approach which takes avoiding action based on the possibility of significant environmental or other damage, even before there is conclusive evidence that the damage will occur.

Return Period
The return period of an extreme storm or weather event is usually expressed in years. For example, an event with a return period of fifty years has a probability of 1 in 50 of being exceeded in any given year. There can be no guarantee that such an event will not be exceeded more than once in fifty years.

Revetment
A cladding of stone, concrete or other material to stabilise and protect shorelines, embankments or shore structures against erosion by wave action or currents.

Scheme
In the context of flood and coastal defence and the FCD: PAG (Flood and Coastal Defence: Project Appraisal Guidance) series, a scheme usually relates to the implementation of works on the ground. It is normally the case that a scheme (or schemes) is identified as a consequence of a broad-based investigation and has quite specific objectives. Stages of scheme development may include pre-feasibility studies, detailed appraisal and construction.

Sea Defence
A structure that prevents the ingress of sea over the land, or the activity of providing protection against flooding from the sea by management of flood defences and flood warning

Sea Level Rise (SLR)
Phenomenon mainly produced by isostatic movement (north-west Britain is rising following glacial withdrawal at the end of the last Ice Age, causing the south-east of England to sink), combined with subsidence of the coast associated with a tectonic fault between the Solent and north-east France, and more recently exacerbated by global sea level rise as a result of climate change. The rise in sea levels due to global warming causing thermal expansion of the oceans and to a lesser extent from melting of the ice caps and glaciers. Relative sea level rise refers to the effective change in sea level relative to the land surface and takes account also of long-term land movement. The combined effect of these changes are thought to result in an annual SLR in Southern England of about 6mm per year.

Sediment cell
A length of coastline and its associated near-shore area within which the movement of coarse sediment (sand and shingle) is largely self-contained. Interruptions to the movement of sand and shingle within one cell should not affect beaches in an adjacent sediment cell. The boundaries of sediment cells are usually defined by major headlands or large estuaries.

Sediment sub-cell
A sub-set of a sediment cell within which the movement of coarse sediment (sand and shingle) is relatively self-contained. The sediment sub-cell is in many cases, likely to provide the appropriate basis for the development of Shoreline Management Plans.

Shoreline
The interface between the land and sea.

Shoreline Management Plans (SMPs)
Refer to plans developed by members of Coastal Defence Groups, covering a stretch of coastline, which address factors such as the geological structure of the coast, the natural processes which influence it, the land use in the area, development plans and the flood and erosion risks along the coast. The SMP proposes a strategy for the future approach to the defence of the coast where that is appropriate looking ahead for up to fifty years but subject to five yearly review.

Soft defences
Those defences which generally rely on natural materials or use natural response mechanisms to control river and coastal flooding and erosion. For example, the encouragement of saltmarsh growth to protect the banks of estuaries, management of beaches to absorb wave energy, the use of water meadows and reed beds to reduce river flow velocities and the use of washlands to reduce peak river flows. Their effective use requires a thorough understanding of the natural forces and responses in the river or coastal system.

Standard of protection
The level of a defence required to provide the necessary protection for a particular return period event.

Strategic
Used to describe the undertaking of any process in a holistic manner taking account of all associated impacts, interests of other parties and considering the widest possible set of potential options for the solution of a problem.