Valuing structured alternatives for retrofitting blue-green infrastructure at a catchment scale using the Benefit Estimation Tool (B£ST)

ABSTRACT Blue-green infrastructure (BGI) options are considered to be more sustainable practices for water management and bring a range of benefits over and above water management. Davidshall in Malmö, Sweden, has been used as a case area to assess the multiple benefits of implementing BGI, considering seven alternative BGI schemes systematically developed along two scales: naturalness (i.e. more/less engineered/complex) and spatial distribution (e.g. decentral vs. end-of-pipe). The baseline alternative was the existing situation. The Benefit Estimation Tool (B£ST) was used to carry out a socio-economic assessment. The overall benefits varied significantly (two orders of magnitude), depending on the BGI scheme implemented: the greatest values were associated with natural decentral, natural decentral/end-of-pipe, and engineered decentral/end-of-pipe alternatives, those including sub-surface and open dry detention, stormwater tree pits, and rain gardens. The three B£ST categories providing the greatest benefits were enhancing amenity, benefiting health, and reducing flooding. Cultural ecosystem services were provided by all alternatives, and two alternatives (natural decentral and natural decentral/end-of-pipe) also provided regulating ecosystem services. The study showed that amenity and health were the most significant benefits of BGI implementation, contrasting with the main aim of BGI implementation, which was stormwater management (water quality and flood protection).