B£ST (Benefits EStimation Tool)
B£ST (Benefits EStimation Tool) is an Excel spreadsheet tool which provides guidance to estimate the monetary benefits of Blue Green Infrastructure (BGI), including Sustainable Drainage Systems (SuDS) and Natural Flood Management (NFM), without the need for specialist economic input. Estimates are based on the performance of the whole system rather than individual components.
B£ST begins with simple qualitative assessments to quickly identify which benefits should be evaluated further. B£ST provides support to help quantify and monetise each benefit chosen. On completion of the evaluation, a series of graphs and charts present the benefits in terms of ecosystem services and natural, social and other capitals. B£ST can support investment decisions, help to identify stakeholders and find potential funding routes.
Site and project data in Excel spreadsheets.
Guidance; Quantitative data on ecosystem services; Tables / statistics / reports; Economic assessment; Ecosystem service impact score / Development impact score; Cost-benefit assessment
How does it work?
The benefit categories most appropriate to assess for a scheme are selected through initial qualitative screening questions. This also enables a high-level indication of the potential range of benefits provided from limited input information. Site-specific data is then entered for the chosen categories.
B£ST is based on robust research evidence and provides a structured approach to evaluating a wide range of benefits. Where feasible, it enables benefits to be quantified and monetised. Summary tables present results under the Ecosystem Services (ESS) framework and in terms of natural, social and other capitals. A series of graphs are automatically generated for use in reports. An Option Comparison Tool enables data from more than one assessment to be compared against baseline in terms of net present cost, benefit and value. B£ST enables a robust, standard approach to assessing the benefits of BGI that is consistent with broader (e.g. government) economic appraisal guidance.
Key data sources:
Terrestrial, freshwater or marine focus?
- Marine Focus
User Time Requirements:
Low-moderate requirement depending on extent of the project – The initial coarse assessment can be undertaken rapidly.
CIRIA (formerly Construction Industry Research and Information Association).
Natural Greenspace in Surrey
B£ST was used to evaluate the benefits of establishing a SANG (Sustainable Alternative Natural Greenspace) to support new housing development. The site was Burpham Court Farm, a 32-acre site north of Guildford, leased and managed by Surrey Wildlife Trust. The establishment of a SANG would involve making the site accessible to the public. B£ST was used to evaluate the ecosystem service benefits of the SANG.
Roundhay Park, Leeds
Yorkshire Water undertook a study at Roundhay Park, in Leeds, to assess the potential of four options to reduce combined sewer overflow (CSO) and improve water quality. The costs, immediate benefits and wider benefits of SuDS and conventional drainage approaches were compared to the current drainage performance in the existing urban area. Option 1 (storage of water in concrete tanks during storms) and option 2 (storage tanks and pipe upsizing) were conventional approaches. Option 3 (combination of swales, detention basins, geocellular storage and connected pipes in public areas) and option 4 (same as 3 and also administered in private areas) were SuDS approaches. Option 1 was cheapest and reduced CSO spills but provided limited other benefits. Options 2, 3 and 4 offered similar underground sewer drainage performance. 3 and 4 both added a surface drainage benefit, and wider community and environmental benefits. Only option 3 generated a positive net present value (benefits greater than costs).
In 2013, Glasgow City conducted a restricted Environmental Impact Assessment to assess the costs, flood risk benefits and wider benefits provided by surface water management options, including SuDS. B£ST was used to assess the implementation of SuDS (e.g. green roofs, permeable paving, swales) with other surface water management measures that could form part of the city’s redevelopment plan. The proposed option was compared to a baseline ‘do nothing’ case. The benefit models assessed were amenity, carbon sequestration, enabling development, flood risk, health, recreation and water quality. The majority of the benefits provided by a SuDS approach were associated with flood risk reduction. Other notable benefits included recreation, water quality and amenity. The estimated benefits of the SuDS option were always greater than the costs (the benefit-cost ratio was 2.3 after confidence levels were applied).
Advice is to apply the tool as early in the decision-making process as possible while the opportunity to incorporate BGI is available.
The tool allows the user to incorporate site-specific, locally derived values (see ‘value library’) – these should be used where possible in order to develop a more accurate and robust assessment.
The tool considers uncertainty by using user-defined estimates of confidence (scores range from 0 – 100% confidence). Optimism bias (i.e. where users overstate benefits and understate costs) is also considered as part of the methodology.
Based on information provided by the user during the screening process and benefit assessment, the tool includes a sheet that identifies potential stakeholders with whom it may be appropriate to engage.
Users are required to provide personal details when downloading some documents from the website, these details are added to a mailing list, if consent is given to do so.
Third Party Reviews/ Cross:
Ashley, R.M. Digman, C.J. Horton, B. et al. (2018)
Evaluating the longer term benefits of sustainable drainage
Proceedings of the Institution of Civil Engineers
Water Management 171 April 2018 Issue WM2
Pages 57–66 https://doi.org/10.1680/jwama.16.00118
Morgan, M. and Fenner, R. (2017)
Spatial evaluation of the multiple benefits of sustainable drainage systems
Proceedings of the Institution of Civil Engineers
Ossa-Moreno, J., Smith, K.M and Mijic, A. (2017)
Economic analysis of wider benefits to facilitate SuDS uptake in London, UK
Sustainable Cities and Society 28, 411-419