Local Flood Risk Management Strategy

Climate change mitigation:

Actions to limit the impact of human activity on the climate, primarily through avoiding and reducing the emissions of heat-trapping greenhouse gases into the atmosphere.

Combined sewer:

Underground pipe systems which carry both wastewater and surface runoff to a sewage treatment plant.

Convective storms:

These are commonly referred to as thunderstorms and are associated with sudden temperature changes. They are more likely to occur in the summer.

Culvert:

Where a watercourse flows through an underground pipe or conduit.

Decommissioning:

The process of retiring redundant flood management assets at the end of their service life

Exceedance:

Flood events which exceed the drainage system’s design level of surface.

Flood:

Any case where land not normally covered by water becomes covered by water (as defined by the Flood and Water Management Act 2010).

Foul sewer:

Underground pipe systems which carried only wastewater (e.g., from toilets, sinks, showers, and kitchen appliances) to a sewage works for treatment.

Fluvial flooding:

Flooding resulting from water levels exceeding the bank level of a river.

Greenfield:

Land that has never been developed other than for agricultural or recreational purposes.

Groundwater flooding:

Occurs when water levels in the ground rise above the natural surface to cover land not normally covered by water. Areas underlain by permeable strata (e.g., Chalk, river gravels) are particularly susceptible.

Gully:

Drainage pit covered by an open metal grated, located at the edge of a road. Drains rainwater from the road into the sewerage system.

Internal Drainage Board (IDB):

A public body that manages water levels in areas of special drainage need. Applicable to only one area in Buckinghamshire for which the Buckingham and River Ouzel Internal Drainage Board has flood risk management responsibilities.

Lead Local Flood Authority (LLFA):

County councils and unitary authorities which lead in managing local sources of flood risk (i.e., flooding from surface water, groundwater, and ordinary watercourses)

Lifetime of development:

Residential development should be considered for a minimum of 100 years unless there is specific justification for considering a different period. For non-residential development, 75 years forms the starting point for assessment.

Local flood risk:

Flooding from sources other than Main Rivers, which principally concerns surface water, groundwater, and Ordinary Watercourses.

Main river:

A large river or stream designated on the Main River Map. The Environment Agency has permissive powers to maintain and carry out flood risk management work on main rivers.

Management train:

The sequence of drainage components that collect, convey, store, and treat runoff as it drains through the site.

Multiple benefits:

The economic, environmental, and social benefits that can accompany the reduction in risk to people and property through flood risk management measures.

Nature-based solutions:

A suite of techniques which sustainably manage and restore natural systems to help to tackle flooding and climate change.

Natural flood management:

A type of nature-based solution that involves the alteration, restoration, or use of landscape features to reduce flood risk. This may include regenerative soil management practices, peatland restoration, leaky dams, ponds, reconnecting floodplains and creating upstream storage areas.

Net zero:

The point at which the amount of greenhouse gases being put into the atmosphere by human activity in the UK equals the amount of greenhouse gases that is being taken out of the atmosphere.

Ordinary watercourses:

All watercourses which are not designated as ‘Main Rivers’. Lead local flood authorities and internal drainage boards have permissive powers to carry out flood risk management work on ordinary watercourses.

Overtopping:

This occurs when flood levels exceed the defence’s design levels or its standard of protection (see Standard of protection).

Placemaking:

A participatory approach to the planning, design and management of public places that improves urban vitality through harnessing the ideas, inspiration, and assets of the local community.

Pluvial flooding:

Flooding from intense rainfall causing water to runoff or pond on the ground surface.

Preliminary Flood Risk Assessment:

A high-level assessment of flood risk in the county based on historic and predicted flooding that was required by the Flood Risk Regulations 2009.

Resilience:

The capacity of people and places to plan for, better protect, respond to and to recover from flooding and coastal change (or other impacts of climate change).

Resilience measures:

Measures designed to reduce the impact of water that enters property and businesses; could include measures such as raising electrical appliances.

Resistance measures:

Measures designed to keep flood water out of properties and businesses; could include flood guards for example.

Riparian owner:

The owner of land that is next to a watercourse or has a watercourse running through or beneath it.

Risk:

In flood risk management, risk is defined as a product of the probability or likelihood of a flood occurring, and the consequence of the flood.

Risk of Flooding from Surface Water:

A dataset from nationally available mapping of surface flooding from a 3.3%, 1% and 0.1% annual chance of flooding

River basin:

An area of land from which all surface runoff flows towards a single river via a sequence of streams, rivers and occasionally, lakes.

Sequential Test:

A decision-making tool applied in strategic planning to review options for locating development sites across the planning authority area. This approach to ensure that new developments are steered towards areas with the lowest flood risk from all sources of flooding.

Stakeholder:

A person or organisation affected by the problem or solution or interested in the problem or solution. They can be individuals or organisations, the public and local communities.

Standard of protection:

The design level to which flood defences can provide a reduction in risk from river flooding, this is usually described in terms of a flood event return period (for example a 1 in a 100-year standard of protection).

Storm overflows:

Permissive discharge of flow that exceeds the capacity of a combined or partially separated sewer to a surface water body.

Strategic Flood Risk Assessment:

An assessment of flood risk from all sources and its implications for land use planning in the county.

Supplementary Planning Documents:

Non-statutory documents that provide more detail on policies provided in the Local Plan. The guidance in these documents are material considerations when determining planning applications.

Surface runoff:

This term refers to rainwater (including snow melt) which flows over the ground surface and has not entered a watercourse, drainage system or public sewer. This is often associated with periods of intense rainfall and where the ground is saturated or impermeable.

Surface water sewer:

Sewers which carry rainwater directly to a watercourse or the sea.

Surface Water Management Plan:

This plan outlines the preferred surface water management strategy in an area and identified the actions, timescales, and responsibilities of each local partner.

Sustainability:

In the context of this Strategy, sustainability refers to managing and reducing flood risk in Buckinghamshire in a way which does not compromise our ability to address the socio-economic and environmental needs of the future.

Sustainable drainage systems (SuDS):

Management practices and features that are designed to manage rainfall as close to its source as possible, to mimic natural drainage and encourage its infiltration, attenuation, and passive treatment.

Swale:

A shallow vegetated channel designed to conduct and retain water, but also may permit infiltration.

UKCP18:

The UK Climate Projections produced by the Met Office in 2018 provide climate data at a UK scale. These are derived from regional climate models run for Northwest Europe from 1980-2080.

Water table:

The point below the ground at which the upper surface of groundwater can be detected. This level may be seasonal and altered by rainfall.

Water Framework Directive:

An EU Directive, transposed into UK law, that requires surface waters and groundwater to achieve good status. This is to deliver multiple benefits including reduced pollution and a better environment for biodiversity and people.