Integrating Green and Gray: Creating Next Generation Infrastructure

TLDR

Traditional built infrastructure alone cannot meet 21st‑century climate resilience needs, so integrating natural systems—such as forests, floodplains, and soils—with gray infrastructure can enhance performance, resilience, and cost‑effectiveness while protecting communities. This report guides developing‑country service providers and partners on how to seize the opportunity to integrate green and gray infrastructure. It offers a framework for evaluating green infrastructure across technical, environmental, social, and economic dimensions, and provides guidance for policymakers and development partners to set incentives and enabling conditions for mainstreaming integrated solutions.

Abstract

Traditional infrastructure systems worldwide rely on built solutions to support the smooth and safe functioning of societies. in the face of multiplying environmental threats, this approach alone can no longer provide the climate resiliency and level of services required in the 21st century. Natural systems such as forests, floodplains, and soils can contribute to clean, reliable water supply and protect against floods and drought. In many circumstances, combining this “green infrastructure” with traditional “gray infrastructure,” such as dams, levees, reservoirs, treatment systems, and pipes, can enhance system performance, boost resilience, lower costs, and better protect communities. Service providers such as water utilities, flood management agencies, irrigation agencies, and hydropower companies can deliver more cost-effective and resilient services by integrating green infrastructure into their plans. However, to guide its appropriate use in mainstream infrastructure programs, green infrastructure must be as rigorously evaluated and carefully designed as gray projects. This report guides developing country service providers and their partners on how to seize this opportunity. It offers service providers a framework to evaluate green infrastructure from a technical, environmental, social, and economic perspective, and to assess key enabling conditions, with illustrative examples. It also provides guidance for policymakers and development partners, who must set the incentives and enabling conditions to mainstream solutions that unite green and gray infrastructure.