Spatial Methods for Green Infrastructure Planning. Strategies for Stormwater Management and Park Access

Planning sustainable and resilient cities is intricate. The variety and abundance of environmental, social and economic issues require systematic and comprehensive solutions, and the effectiveness of these solutions calls for strategic planning and design. Green infrastructure are engineered vegetated systems, such as green roof and rain gardens, and can support sustainability and resilience goals by proving opportunities to improve the natural, built and social environment of cities. The effective implementation of GI programs and project requires not only observing multiple and diverse criteria, but also considering how these criteria are distributed across space. This research proposes a framework for the spatial analysis supporting green infrastructure planning, and uses the Central Oahu Watershed (HI) as a case study. The framework provides guidance on where GI is most needed and would bring the most benefits across the study area, based on local sustainability and resilience goals. Priority was given to stormwater management and the creation of public open space, and suitability analysis in GIS was used to assign GI priority scores across the study area. First, stormwater runoff depths were calculated combining land cover, soil properties and rainfall spatial data according to the SCS-CN method. Second, public park access was estimated based on 10-minute walk network analysis from selected park entrances and on the ratio of resident of these catchment areas and surface of the park itself. Finally, GI priority scores were calculated by combining stormwater management and park access with elevation, a population-weighted vulnerability index, and zoning. The final output consists of a map showing the distribution of GI priority scores across the study area. This framework unpacks the complexity around sustainability, resilience and GI and provides a straight forward, replicable and flexible, approach to GI spatial planning.