Developing the Great Lakes Cities Permeability Index

Stormwater runoff pollution bears significant responsibility for water quality degradation, particularly in urban areas. Green infrastructure leverages the absorptive qualities of deep-rooted native plants, the storage and filtration capacity of soil, and the pollutant removal function of healthy soil's microbial community to capture raindrops where they fall. Protecting, restoring and mimicking natural drainage using green infrastructure reduces runoff pollution, filters stormwater, and helps to reduce flooding and combined sewer overflows, while recharging natural hydrologic functions and improving community health.The Great Lakes Cities Permeability Index will assist cities to target, apply, and track community scale green infrastructure for improved water quality and community health. Combining geographic information system analysis of landscape capacity for green infrastructure—referred to generally as permeability, a Green Values™ stormwater calculator to estimate hydrologic and cost-effectiveness, and a web based public implementation registry, the GLCPI project will assess existing permeability at various geographic, hydrological and administrative scales, such as watersheds, blocks or sewersheds within cities.The Permeability Index will help focus cities' and their citizens' efforts to protect water quality by capturing stormwater through on-site green infrastructure (GI). The Permeability Index will quantify the potential for GI implementation to improve effective permeability to levels desired by each city, allow municipalities and individuals to register GI installations as they are implemented, and estimate costs and hydrological effectiveness associated with scaled GI implementation. The Center for Neighborhood Technology (CNT) has partnered with four Great Lakes municipalities—Chicago, Milwaukee as well as the county-wide Milwaukee Metropolitan Sewerage District (MMSD), and Evanston on Lake Michigan, and Fort Wayne, IN on the Maumee River, a tributary of Lake Erie—to develop the Great Lakes Cities Permeability Index (GLCPI) project. This paper summarizes results of the initial planning phase of the project.