Integrated urban green and grey infrastructure

Abstract

Integrated urban green and grey infrastructure combines “green” (natural; living) and “grey” (human-made; anthropogenic) infrastructure constituents to provide facilities in support of key (ecosystem) services and functions to urban communities. Integration may occur in the form of green infrastructure adding improved or additional services or functions to grey infrastructure, or grey infrastructure increasing the functionality of green infrastructure. It may also occur along a green-grey continuum based on the proportional composition of green or grey constituents within integrated green and grey infrastructure systems. Integration occurs at three spatial scales (scale of integration): first, at the intracomponent scale when one infrastructure component includes both green and grey constituents (e.g., a biofiltration facility); second, at the intercomponent scale when two components, one grey and one green, work together to provide particular services or functions (e.g., a levee protecting a wetland from coastal floods); and finally, at the system scale when multiple green, grey, and/or green-grey components establish a system (e.g., rain gardens, planters, trees, street furniture, and car parks working together to provide street calming services). Type of integration refers to how green-grey infrastructure constituents are connected with each other. Physical integration means that infrastructure components and/or systems are physically connected (e.g., a water conveyance system). Functional integration means that green, grey, and/or green-grey infrastructure components and/or systems together provide services or function(s) without being physically connected (e.g., street trees, planters, and raingardens along a street providing bird habitat without being physically connected).