Including uncertainty in valuing blue and green infrastructure for stormwater management

Blue and green infrastructure (BGI) provides a wide range of ecosystem services (ES) and other benefits when managing stormwater, beyond flow and pollution control. A number of tools have been developed to value these benefits. In the UK, stormwater measures that utilise BGI are known as Sustainable Drainage Systems (SuDS). This paper outlines the Benefits of SuDS Tool (B£ST), developed in the UK by the Construction Industry Research and Information Association (CIRIA) for valuing the benefits of BGI stormwater measures. The tool has been applied to case studies across Europe. B£ST includes a set of benefits based on ecosystem services applied to the use of BGI for stormwater management. The paper focuses on the uncertainties in this multiple benefit assessment, detailing the processes used in the tool. Examples illustrate the scale of the uncertainties in tools like B£ST. The uncertainties when using BGI valuation tools such as B£ST to help inform the delivery of stormwater measures are demonstrated in the paper as potentially of sufficient magnitude to warrant explicit consideration by professionals and decision makers.