Delivering sustainable flood risk management: guidance (2019)

Second edition of statutory guidance to SEPA, local authorities and Scottish Water on fulfilling their responsibilities under the Flood Risk Management (Scotland) Act 2009.

Annex 2

Glossary of terms


These are activities to be taken to reduce the risk of flooding. This may include woodland planting, flood walls, flood warning and others.

Cost/Benefit Analysis

Comparison of present value 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.

Catchment or Catchment Area

The specific land area that drains into a watercourse.

Civil Contingencies

The Civil Contingencies Act 2004 establishes a framework for emergency planning and response at both a local and a national level.

Climate Change

Long-term changes in climate, either through natural variability or human intervention.

Coastal Flooding

Flooding that results from a combination of high tides and stormy conditions.


An impact such as economic, social or environmental damage/improvement. May be expressed quantitatively (e.g. monetary value), by category (e.g. High, Medium, Low) or descriptively.

Controlled Activities Regulations (CAR)

A reference to The Water Environment (Controlled Activities) (Scotland) Regulations 2005. All engineering works in or in the vicinity of rivers, lochs and wetlands now require authorisation under the CAR Regulations.


A closed conduit used for the conveyance of surface drainage water under a roadway, railroad, canal, or other impediment.


DEFRA (Department for Environment, Food and Rural Affairs) is a UK Government Department.

Diffuse Pollution

Pollution which originates from various activities and which cannot be traced to a single source e.g. contaminated run off from built up areas.

Do-Nothing Scenario

An option used in benefit/cost analysis to act as a baseline against which all other options are tested. It assumes no active intervention.

EC Floods Directive

The EC Directive on the Assessment and Management of Flood Risks or EC Floods Directive builds on and is closely related to the Water Framework Directive.


Artificial raising of the natural bank height of a waterway.


Where environmental issues are referred to in this document, this term is used to encompass landscape and visual, flora, fauna, geological or geomorphological features and buildings, air, water, sites and objects of archaeological, architectural or historical interest. (It is recognised that in other contexts the environment has much wider implications).

Environmental Impact Assessment (EIA)

Environmental Impact Assessment (EIA) is a process which identifies the potential environmental effects (both negative and positive) of a proposal.

Flood Risk Management Strategies (FRMS)

High-level plans prepared by SEPA that set out the strategic direction of flood management, through to specific projects or schemes.


Floodplains are land areas adjacent to rivers and streams that are subject to recurring inundation.

Fluvial flooding

Also known as river flooding. Flooding that results from rivers and water courses exceeding their capacity.

Greenhouse Gases

Naturally occurring gases, such as carbon dioxide, nitrous oxide, methane and ozone, and man-made gases like chlorofluorocarbons, which absorb some of the sun's radiation and convert it into heat.

Groundwater Flooding

Flooding that occurs when water levels in the ground rise above surface levels. It is most likely to occur in areas underlain by permeable rocks, called aquifers.


A situation with the potential to result in harm. A hazard does not necessarily lead to harm.

Impermeable Surface

A surface that does not permit the infiltration of water and, therefore, generates surface water runoff during periods of rainfall.

Lead local authority

Each local plan district is governed by a partnership of all responsible authorities which cover that area. The lead local authority has overall responsibility for running the partnership, publishing the local flood risk management plans and reporting on the progress of actions.

Local Flood Risk Management Plans

Plan prepared by lead local authorities that provide a local expression of the strategic plans prepared by SEPA. Include a summary of how actions will be implemented in each local plan area.

Pluvial flooding

Flooding that results from overland flow which has been generated by rainfall before the runoff enters any watercourse or sewer. This is also referred to as surface water flooding.

Post project evaluation

A procedure to review the performance of a project with respect to its original objectives and the manner in which the project was carried out.


Informing the population about flood risks and what to do in the event of a flood.


The probability of an outcome is the relative proportion or frequency of events leading to that outcome, out of all possible events. It describes how likely an event is to happen.

Qualitative Methods

Approaches which use descriptive rather than numerical values for assessment and decision making.

Residual risk

The risk which remains after risk management and mitigation. May include, for example, risk due to very severe (above design standard) storms, or risks from unforeseen hazards.


Resilience is a measure of the ability of something to recover from a flood.

Responsible authorities

Designated under the Flood Risk Management (Scotland) Act 2009 to have responsibility for reducing the risk of flooding in Scotland. In 2017 these include local authorities, Scottish Water, Forestry Commission Scotland, Cairngorms National Park, and Loch Lomond and the Trossachs National Park. The Scottish Government may designate further responsible authorities.

Restoration of natural flooding processes

This is the return of a landscape, ecosystem, or other ecological entity to a predefined historical state where the flooding processes are uninterrupted.

Return Period

The flood return period is a measure of the rarity of an event - the longer the return period, the rarer the event. It is the average length of time (usually in years) separating floods of a similar magnitude.


A combination of the likelihood and consequences of an event.

River Basin District

Geographic areas over which River Basin Management plans area prepared. In Scotland there are 2 River Basin Districts identified under the 2003 Act - one for the Solway/Tweed area and one covering the rest of Scotland.

River Basin Management Planning

River basin planning is a strategic decision-making process introduced by the Water Framework Directive (WFD) which integrates the management of land and water within river basin districts (RBDs).


The Society of Chief Officers of Transportation in Scotland (SCOTS).

Scottish Water

Scottish Water is a publicly owned business, answerable to the Scottish Parliament and the people of Scotland. Its key duties are providing clean, safe drinking water and disposing of waste water from homes and businesses across Scotland.

Sensitivity testing

Method in which the impact on the output of an analysis is assessed by systematically changing the input values


Scottish Environment Protection Agency. SEPA is the public body responsible for environmental protection in Scotland.

Sewer Flooding

Flooding caused by a blockage or overflowing in a sewer or urban drainage system.


Actions taken now to manage the risk of flooding that are robust enough to stand the test of time. There are three pillars of sustainability that must be considered - environmental, social and economic.

Sustainable Development

Sustainable development is an approach to resource use that aims to meet human needs, while preserving the environment so that these needs can be met not only in the present, but also for future generations. The delivery of sustainable development is generally recognised to require reconciliation of three pillars of sustainability – environmental, social and economic.

Sustainable Urban Drainage Systems (SUDS)

A set of techniques designed to slow the flow of water, can contribute to reducing flood risk by absorbing some of the initial rainfall, and then releasing it gradually, thereby reducing the flood peak and helping to mitigate downstream problems, and make a useful contribution to flood management.


Vulnerability is defined as a combination of susceptibility and resilience.

Water Framework Directive (WFD)

The WFD establishes integrated river basin management for Europe. It requires all inland and coastal waters to reach "good status" by 2015, or an alternative or delayed objective.

Whole Life Costs

The total costs associated with a scheme for its full design and potential residual life span, taking proper account of all aspects of design, construction, maintenance and external impacts. A particularly useful approach in helping to determine economic sustainability when used to compare the relative costs of long-life schemes such as flood defences and where decisions between short-term capital costs and long-term maintenance costs need to be made.

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