Natural Flood management in Scotland

There is growing recognition that alongside more traditional structural measures, Natural Flood Management (NFM) can represent a key part of a catchment-based approach to sustainable flood risk management. When used effectively, it can help reduce the impact of floods, as well as improving water quality, increasing biodiversity and delivering other benefits. Although primarily aimed at reducing the maximum water volume of a flood, temporarily storing excess flood water and delaying the arrival of the flood peak downstream, NFM can also provide a wide range of other benefits to society. To date however, methods to assess these additional ecosystem services and integrate consideration of their value into decision-making processes for appraisal of flood risk measures have been lacking.

Funded primarily by the Scottish Government, with support from the EU Interreg Building with Nature programme, SEPA, University of Dundee and others, the Eddleston Water Project was set up in 2009 as a case study for assessing the effectiveness of NFM measures[1]. The Project, which is led by the Tweed Forum, is a long-term empirical study of the implementation and effectiveness of NFM measures to reduce flood risk to downstream communities, and to improve wetland habitats, whilst maintaining sustainable farming livelihoods in the catchment. Recent attention has focussed on assessing the value of other benefits delivered by NFM measures; as a result, the Eddleston Water Project appointed Mott MacDonald to conduct a research study to investigated how multiple benefits from NFM can be effectively integrated into current decision-making processes for the appraisal of flood risk management measures in Scotland.

A Steering Group was established to oversee the technical quality of the study and ensure that relevant stakeholders were actively engaged. The Steering Group was responsible for the definition of the scope of the study, providing technical direction during the study and reviewing deliverables.  The Steering Group comprised of individuals from the following organisations:

  • Tweed Forum
  • University of Dundee
  • Scottish Government
  • Scottish Borders Council
  • Scottish Environment Protection Agency
  • NatureScot (formerly Scottish Natural Heritage)

Consultation with stakeholders

An online survey was conducted to explore the views of key stakeholders on the incorporation of multiple benefits in the form of ecosystem services into the Scottish flood risk management decision-making process.The primary purpose of the survey was to ascertain the views of Local Authority flood risk management officers and their consultants. The survey was also used to obtain and collate views from academics, regulators and government officers further extending on the groups represented by the Steering Group.

Key findings from the survey included that the most well-known (defined by “awareness”) ecosystem services method across all surveyed groups was CIRIA B£ST[2] with 60% of survey respondents reporting awareness. The survey showed that a majority of consultants perceive that appraising ecosystem services never or rarely impacted on Flood Risk Management Scheme appraisal outcomes. The survey also highlighted that many individuals feel lost in a jargon heavy process in a complex and challenging field with many competing issues.

Newly created ponds at Ruddenleys, providing flood storage and new habitats
Newly created ponds at Ruddenleys, providing flood
storage and new habitats

How can benefits be measured and integrated into current decision-making processes?

Currently, there is an extensive number of potential tools and frameworks that could be used to integrate ecosystem services benefits into the flood risk decision-making process. However, none of these present a single comprehensive, consistent, and agreed methodology. Many of the potential tools utilise different methodologies and present the results of the assessment in different formats. This variety of tools has led to uncertainty within practitioners as to the ‘correct’ methodology to use and has potentially prevented the inclusion of ecosystem service benefits within flood risk appraisals.The existing guidance provided by the Scottish Government on undertaken flood risk management appraisals[3] does not set defined requirements for the consideration of ecosystem services giving project teams ample justification to avoid what some, as shown by the engagement survey,
perceive to be a time consuming and pointless additional task.

To try and provide a single agreed methodology a detailed review of existing current environmental and social appraisal methodologies within the flood management sector was undertaken. The Ecosystems Knowledge Network Tool Assessor [4] (ESKN) was used as the central source of information on the available assessment methods and case studies. This information from the ESKN tool assessor was supplemented by the expert knowledge of the project steering group and the results of the engagement survey.

The list of potential environmental evaluation methods underwent a two-stage assessment: firstly, to ensure that the methodologies considered were suitable and secondly, to identify the preferred method according to set criteria. The first stage involved screening 28 methodologies on accessibility, whether they monetised a suitable range of environmental benefits and whether they were applicable to Scotland. Nine methodologies made it through to the second stage of the assessment where the methodologies were ranked on a set of criteria agreed with the project steering committee and stakeholders, shown below:

  • Level of work required
  • Accuracy of results
  • Technical complexity
  • Repeatability
  • Compatibility with Scottish flood risk management appraisal process
  • Ability to also consider energy, water and materials use


Using the assessment criteria agreed, the review concluded that B£ST[5] was the leading appraisal tool to support the evaluation of multiple benefits within flood risk management appraisals. Key factors for the selection of B£ST included that the tool is open access and does not require any specialist software. It is provided with a comprehensive accompanying guidance document that provides relevant information and data requirements. In addition the publisher, CIRIA, states that B£ST is not a single release and will be updated in the future. The tool is suitable for assessing a range of multiple benefits including:

  • Amenity
    o Remeandered sections at Cringletie, looking upstream. The straight line of the 1800’s water course is visible between the road and the remeandered sections
    Remeandered sections at Cringletie, looking
    upstream. The straight line of the 1800’s water
    course is visible between the road and the
    remeandered sections
  • Asset performance
  • Biodiversity and ecology
  • Building temperature
  • Carbon reduction and sequestration
  • Education
  • Enabling development
  • Flooding
  • Health
  • Noise
  • Recreation
  • Traffic calming
  • Water quality
  • Water quantity

Where appropriate it can be used to quantify disbenefits (detriment) in addition to benefits and compare output for multiple options within a project. Importantly the tool was the most well-known tool within the target user community (although the extent of the target community’s experience in using the tool is thought to be low). The valuation methodology in the tool is in line with good practice, as well as with government appraisal guidance[6] and consistent with other approaches in the sector.

The review of B£ST acknowledged that it is not an all-encompassing solution to the assessment of multiple benefits. The identified limitations of the tool include:

  • It does not currently include a spatial element to the assessment of wider benefits.  At the time of writing plans have been announced for the incorporation of spatial tool in the next release of B£ST.
  • There is limited support for the identification of opportunities.
  • B£ST does not specifically allow for the incorporation of peatland carbon sequestration and relies on an external tool to assess woodland carbon sequestration.
  • As with all methods, it may be appropriate to obtain more detailed or locally based information when doing more detailed studies or where decisions are sensitive to small changes in the generalised national data within the tool.
  • Following on from the preceding point, B£ST was primarily developed using English and Welsh data for an English and Welsh target user group. Therefore, the B£ST guidance and tool terminology sometimes deviate from that used in Scotland.  It is also necessary for users to select appropriate donor locations from the available English and Welsh in tool options.

As part of the project, B£ST was tested on the Eddleston Water to trial its suitability. It was found to be intuitive to use with easy access to guidance material.The tool was able to reliably quantify all significant multiple benefits in the form of ecosystem services for the project. The project was shown to provide benefits across Amenity, Biodiversity and ecology, Carbon sequestration, Education, Flows in watercourse, Water quality and pollution. Using a 100-year appraisal period, the ecosystem services associated with the implemented NFM (116 log structures, 30 ponds, 2.9km of remeandering and planting of 330,000 native trees) was estimated to be approximately £4.2M, with further gains from more extensive options.

What does this mean for Flood risk management appraisals in Scotland?

A review of the existing Scottish flood risk management appraisal guidance identified opportunities for B£ST to be integrated into the current decision-making process and inform the appraisal of flood risk management options across setting objectives, long list appraisals, short list appraisal and prioritisation.  Changes to the process of Scottish flood risk management appraisal could to be made to further embed NFM ecosystem service valuation and assessment


The findings of this project have demonstrated that B£ST can be effectively integrated into the current flood risk management decision-making process. B£ST was reviewed against other potential methodologies and was recommended as the preferred approach to support the integration of multiple benefits into the existing flood risk management decision-making process.  When used on the Eddleston Water the tool effectively valued the benefits associated with the project.

The well-known, easy to use and freely available tool will support the accurate assessment of multiple benefits on a wide range of project scales, flooding types (fluvial, coastal and surface water) now and into the future. By prompting the tool to be used across flood risk management appraisals in Scotland it is hoped that that consistency of the methods used is improved, ultimately increasing the value of flood risk management investments.

The study was funded by Scottish Government and the EU Interreg Building with Nature programme, and overseen by a Project Group from Tweed Forum, SEPA, SNH, Scottish Borders Council & Scottish Government.


Professor Chris Spray is a Senior Research Fellow in Geography & Environmental Science at Dundee University, and a member of the Tweed Forum.

Ben O’Hickey is an environmental scientist with Mott MacDonald consultants.


[1] Eddleston Water Project website https://tweedforum.org/our-work/projects/the-eddleston-water-project/

[2] Horton, B., Digman, C.J., Ashley, R.M. and McMullan, J. B£ST Guidance – Guidance to assess the benefits of blue and green infrastructure using B£ST.  CIRIA (2019).  Available at: https://www.susdrain.org/files/resources/BeST/w047b_bst_guidance_release_5_v0b_issued.pdf

[3] Scottish Government.  Flood protection appraisals:  Guidance for SEPA and responsible authorities.  2016 https://www.gov.scot/publications/guidance-support-sepa-responsible-authorities/

[4] JNCC. Ecosystem Knowledge Network Tool Assessor. 2020


[5] CIRIA, W047b B£ST Guidance – Guidance to assess the benefits of blue and green infrastructure using B£ST. 2020

[6] HM Treasury. The Green Book – Central Government Guidance on Appraisal and Evaluation.2018

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