Flood protection appraisals: guidance for SEPA and responsible authorities

Appraisal guidance for the Scottish Environment Protection Agency (SEPA) and responsible authorities.

4. Stage two: develop, describe and value

4.1. Introduction

4.1.1. This stage will identify a broad range of actions that could help to meet the objectives ( Section 3.2) and eliminate unreasonable or unfeasible actions so that the effort focuses on appraising realistic, feasible options.

4.2. Identify a long list of actions

4.2.1. Consideration must be given to a broad range of structural and non-structural actions, both individually and in combination across a catchment or coastal area. The actions may reduce the likelihood of flooding, reduce the damages should a flood occur, or avoid creating new flood risk (or exacerbating existing risk). A narrowly defined search may only identify the best action(s) from a poor set.

4.2.2. Standard lists of actions that can be used as a starting point are published by SEPA (2015b; In prep.).

4.2.3. The management of flood risk may impact on many aspects of the social, natural and historic environment. Wherever possible, SEPA and the responsible authorities should manage flood risk in ways that will improve the environment at the same time as reducing the risks to people and property. Opportunities to do more, while still cost-effectively reducing risk, should be promoted.

4.2.4. Consideration should also be given to the situation and physical aspects of the land and any existing flood risk management actions (including their residual life and standard of protection). Local scale actions should be developed in the context of wider objectives and actions set out in the Flood Risk Management Strategies.

4.2.5. A long-list of actions should therefore be identified with the following points in mind:

4.2.6. Meeting the objective(s)

  • Consider all actions that could partially or completely address the risk of flooding that is predicted or has been observed.
  • Consider actions which are effective at the property, neighbourhood or catchment scale or coastal area, as appropriate.
  • Consider whether there are opportunities to combine actions that address flooding from different sources.

4.2.7. Delivering sustainable flood risk management

  • The actions should aim to deliver sustainable flood risk management (Scottish Government 2011a).
  • Consider the impact that actions will have on flood risk now and in the future. Actions to manage flood risk should reflect the needs of future generations and be adaptable to a changing climate and other drivers of changing flood risk (Sections 4.6.5 and 9.8).
  • Consider actions which could deliver wider benefits such as better places for people to live (e.g. improved amenity or urban regeneration), improved environment (e.g. improvement in water quality) or improved biodiversity.
  • Consider opportunities to improve existing actions e.g. change maintenance regimes or enhance/replace existing actions.

4.2.8. Working with stakeholders

  • Consider actions that could be delivered by the full range of stakeholder organisations.
  • Actions may be added to or refined by the Local Flood Risk Management Partnerships, the Local Advisory Groups or through engagement with all stakeholders.

4.3. Screening the long-list of actions

4.3.1. Screening exercises may be required to reduce a long-list to a shorter list of actions. This will remove any that are clearly unfeasible, leaving a smaller number of actions for further appraisal. Any actions that are technically inappropriate (e.g. an offshore breakwater to deal with fluvial flooding risk) or technically impractical (e.g. a diversion channel over a hill where there are more sensible alternatives) and actions that have insurmountable constraints should be screened out. Complex and integrated solutions, however, should not be shied away from.

4.3.2. Sustainability must be a key consideration and actions that are clearly unsustainable should be rejected early. If necessary, broad positive and negative impacts can be identified for each of the actions. At this stage, technical details are not necessary and impacts do not need to be valued. Experience and informed judgment should be used to help eliminate actions.

4.3.3. There are various legal constraints on what actions can be progressed or, more specifically, the manner in which they are progressed. These mainly deal with the impact on people and the natural or built environment (see Box 4.1). Specific legal obligations should be clarified early in the appraisal process including consideration of how such obligations can be met.

4.3.4. A high level scoring or matrix analysis exercise may be helpful. The reasons for rejecting actions should be clearly stated and recorded. If in doubt, retain the action for further appraisal.

Box 4.1: Examples of legal constraints and considerations

Health and safety

Actions can introduce significant health and safety risks whether during construction, under maintenance or in use. Likewise actions can contribute to an overall reduction in risks to health and safety by reducing flood risk itself or by removing/replacing structures which are inherently hazardous to maintain (e.g. culvert trash screens).

The screening process needs to take a pragmatic approach with regard to actions and not exclude those actions which introduce additional risks during construction, under maintenance and in use, provided that those additional risks can be managed in line with legislation (e.g. Health and Safety at Work etc. Act 1974; Construction (Design and Management) Regulations 2007).

Environmental and heritage protection

Many structural actions have the potential for negative impacts on the natural and/or built environment. Where these impacts are likely to be significant, a Strategic Environmental Assessment ( SEA) / Environmental Impact Assessment ( EIA) and a Habitats Regulations Appraisal maybe required [3] . Furthermore, a range of species, habitats and historic sites are protected by legislation to protect them from damage. It is essential to identify these environmental legislative requirements early in the appraisal process. Late consideration of environmental impacts and/or failure to adhere to environmental legislation can lead to damage to the environment, delays and legal challenges.

At the screening stage, the aim is to modify or remove any actions that raise insurmountable environmental problems, for example:

  • An action is considered to have an adverse impact on the conservation objectives of a Natura site (Special Area of Conservation or Special Protection Area) such that the site integrity itself is compromised and mitigation will not prevent the adverse impact [4] ;
  • The action introduces an unacceptable risk of pollution to surface or groundwater that cannot be avoided or reduced.

This does not mean that actions with any adverse impacts on the environment should be screened out - only those with insurmountable problems. Opportunities should be sought throughout the appraisal process to prevent adverse impacts and to deliver wider benefits. Early engagement with stakeholders is recommended.

4.4. Shortlist of actions: developing options

4.4.1. The screening exercise will have removed any unfeasible actions from the long-list, leaving a shortlist of actions for further assessment. This shortlist of actions should be used to build up viable options to meet the flood risk management objectives. The options should include the 'do nothing' and/or 'do minimum' options; other 'do something' options can be identified using an iterative process to build up viable solutions.

4.5. The 'do nothing'/'do minimum' option

4.5.1. The starting point will be to develop a 'do nothing' or 'do minimum' option. This provides a consistent baseline against which the other options can be compared.

4.5.2. The 'do nothing' case describes the future situation with no further intervention - i.e. cease all current activities and walk away. Identifying the 'do nothing' option correctly is important to the analysis and needs careful consideration:

  • Where there are no existing flood risk management actions, the 'do nothing' option is obvious; there is no intervention in natural processes;
  • Where there is an existing scheme, the 'do nothing' option will be to walk away and abandon all associated maintenance and repair, allowing nature to take its course. For health and safety reasons, it may be necessary to take minimal steps to make any abandoned works safe and these costs should be taken into account. (Simply continuing with maintenance and repair of the existing structure then becomes one of the 'do something' options.);
  • Where there is flood warning or forecasting scheme, the operation of this scheme would cease. Continuing with or altering the scheme would become a 'do something' option;
  • Similarly, any activities to promote or subsidise property level protection would cease under the 'do nothing' option. It should be assumed that where property level protection exists, it may still be applied - however, without a flood warning scheme, property level protection is likely to be significantly less effective.

4.5.3. Where there is a statutory requirement to continue with activities then a 'do minimum' baseline should be used. This is the minimum amount of action needed to meet the legal requirement. Statutory requirements leading to a 'do minimum' baseline may be:

Note that the 'do minimum' option entails costs and these should be taken into account.

4.5.4. Identifying a true 'do nothing' baseline can be difficult without individual models for a specific area. Therefore, for strategic appraisals, a 'do minimum' option may need to be used as the baseline.

4.6. The 'do something' options

4.6.1. 'Do something' options will build on the 'do-minimum' option. The 'do something' options should be developed by looking for opportunities to use non-structural actions and best-practice actions that seek to enhance the (urban and rural) landscape's natural ability to slow and store flood water as well as considering more traditional engineering.

4.6.2. Options should be identified by combining and refining viable ways of meeting the flood risk management objectives. Adding complexity and more features might reduce flood risk but add to cost. The purpose of appraisal is to identify the best balance between the outcomes.

4.6.3. Ministerial guidance (Scottish Government 2011a) does not specify certain design standards - but it does expect all appraisals to include an option that protects to a 1% AEP plus allowances for climate change. Other incremental levels of protection should to be considered during option development. The approach should be risk-based, linking benefits to costs with the aim of maximising the reduction in overall risk.

4.6.4. There is always the possibility that during the lifetime of an action, a flood will occur that is more extreme than the design event. Consequently, arrangements to understand and deal with residual risks (for example, if design limits are exceeded by flood events) should be considered as part of option development.

4.6.5. In particular, pressures such as climate change, land use change and demographic change will lead to changes in flood risk in the future. Because of the uncertainties in projections of future flood risk, it is preferable wherever possible to design actions that can be adapted in future (a managed adaptive approach) rather than to design for climate change and other changes up front (a precautionary approach) (Box 4.2). However, this may not be possible for large one-off interventions where building in climate change and other future adaptations at the start may be the only feasible approach. Section 9.8 provides further guidance on how to take climate change and other drivers of future flood risk into account.

Box 4.2: Reference material for climate change adaptation


Email: Neil Ritchie, neil.ritchie@scot.gov

Phone: 0300 244 4000 – Central Enquiry Unit

The Scottish Government
St Andrew's House
Regent Road

Back to top