A comparison of the cost effectiveness of property‐level adaptation and community‐scale flood defences in reducing flood risk

Abstract Adaptations to flood‐proof individual properties (referred to here as property‐level adaptation, PLA) provide a potential means of reducing flood risk at isolated properties, whilst conventional community‐scale flood protection (CSFP) is usually more economical in protecting high‐density urban spaces. This paper develops a risk‐based framework to identify the tipping point when PLA measures become more cost‐beneficial when compared to CSFP in different urban densities. The framework was demonstrated using a hypothetical case study based on a residential area in Teddington, London. Sensitivity analysis was performed by varying the building densities in the urban space. Results show that PLA can have a role to supplement CSFP even in dense urban areas if the CSFP standard of protection is low. However, adding some element of CSFP to PLA can be more cost‐effective than implementing a single higher protection standard of PLA. Given the unique flood risk condition of most urban spaces, and the sensitivity of cost‐effectiveness of flood adaptation measures such as those demonstrated in this work, this approach can provide additional information to assist decisions in finding a sensible portfolio of measures that match that risk condition.