Where Best Laid Plans Get Waylaid: Assessing the Green Infrastructure Planning Implementation Gap in U.S. Cities

Cities worldwide have ambitious plans to develop green infrastructure for a wide range of sustainability and resilience benefits. Yet many of these plans are never realized, and there is limited empirical research examining the scale or cause of this implementation gap. In this study we address this research need, examining the implementation of green infrastructure projects in 51 city plans from 12 diverse U.S. cities through a combination of plan content analysis, satellite imagery analysis, web searches, and key informant interviews. The results show many plans for green infrastructure are too vague to track, and even among trackable projects with a clear design and proposed location in plan documents, only 36% have started construction. The implementation gap varies across cities’ plan networks, with green infrastructure projects in comprehensive plans and recently adopted plans significantly more likely to be constructed. Follow-up interviews with relevant officials in the cities confirm many challenges to implementation but also suggest focusing on plans might miss some green infrastructure efforts. This study reveals the implementation gap for planned green infrastructure is considerable, especially for smaller or medium-sized cities. Interviews with city officials indicate limited funding, competing priorities, lack of a clearly defined green infrastructure work plan, and staffing shortages are common barriers. Integrating green infrastructure into comprehensive plans could increase the likelihood of implementation, as can clearly defining green infrastructure projects, diversifying funding sources, having a green infrastructure champion, providing local manuals, regulatory requirements, incentives, and tracking and assessing benefits.