A cost-benefit analysis model for the retrofit of sustainable urban drainage systems towards improved flood risk mitigation

Purpose The Environment Agency estimates that one in six homes in England (approximately 5.2m properties) are at risk from flooding and 185,000 commercial properties are located in flood-prone areas. Further, an estimate of 10,000 new homes are built on flood plains yearly. The UK has witnessed a significant increase in flood events over the past 10 years. During this period, there has been growing research attention into measures to mitigate the effects of flooding, including the benefits of deploying sustainable urban drainage systems (SuDs) in new developments or as a retrofit. The purpose of this paper is to present the development of a cost-benefit analysis model for the retrofit of SuDs focusing on the potential for improved flood risk mitigation in the context of commercial properties. Design/methodology/approach A synthesis of flood risk management and SuDs literature is used to inform the development of a conceptual cost-benefit analysis model for the retrofit of SuDs and focusing on the potential for improved flood risk mitigation in the context of commercial properties. Findings SuDs have been applied successfully in different parts of the world; however, the uptake of SuDs, in particular, the retrofit of SuDs, has been restricted by a number of issues including a lack of experience and trust in their performance and a lack of understanding in their true benefits. In particular, there is the limited experience of retrofitting SuDs and there are no well-established procedures for evaluating the feasibility, value or cost effectiveness of doing this. Social implications This offers the potential to support the UK government’s flood risk management policy by helping to increase the resilience of properties, whilst offering other benefits to communities such as improvements in air quality and biodiversity and also presenting a clearer understanding of the monetary and non-monetary implication to owners of commercial properties for a more informed and acceptable uptake of SuDs retrofit. Originality/value The proposed model will allow a more comprehensive understanding of the costs and associated benefits associated with SuDs retrofit, highlighting the flood risk mitigation benefits that might accrue over a period of time for commercial property.