Benefits of coupled green and grey infrastructure systems: Evidence based on analytic hierarchy process and life cycle costing

Abstract Green infrastructure complements grey infrastructure to provide effective urban stormwater management. Design of coupled green and grey infrastructure systems need a systems-based analysis considering multiple criterion. This study used analytic hierarchy process (AHP) and life cycle costing (LCC) to evaluate environmental and economic benefits of various types of coupled green and grey infrastructure systems. AHP results showed that, based on the local conditions and characteristics, the coupled green and grey scenario with green space, permeable pavement, green roof, and stormwater detention cell performed better than other scenarios in urban residential drainage and flood control. Also for the coupled green and grey scenario, the simulation results showed that no flooding was occurred during the ten-year return period rainfall. Coupled green and grey infrastructure scenarios can save the life cycle cost up to 94% compared to the traditional grey infrastructure scenario considering the design, construction, operation, and maintenance stages. Approximately 13% of commercial loan interest (1.03 million USD) can be saved for homebuyers. In future, urban designers and developers should consider the optimization of coupled green and gray infrastructures system under multiple criterion for the environment, economy, and safety benefits.