A longitudinal comparison of stormwater runoff mechanisms in growing and shrinking regions: Evaluating impervious composition and green infrastructure connectivity changes

Growing and shrinking regions are experiencing increased vulnerability to urban flooding because of climate change. While traditional stormwater runoff mitigation policies, such as regulating total impervious areas (TIA) and enhancing green infrastructure (GI) connectivity, have been widely adopted, their effectiveness remains uncertain in the face of divergent patterns of land use change and population shifts. To address this uncertainty, this research examines the impacts of impervious composition and GI connectivity on runoff within the Chicago-Naperville and Detroit-Warren-Ann Arbor combined statistical areas over time, representative growing and shrinking regions in the Midwestern US, respectively. The impervious composition is quantified using TIA and hydraulic connectivity, while GI connectivity is measured using FRAGSTATS. Ordinary least squares and panel data regression models are employed, controlling for socio-demographic, climate, and biophysical variables. The results indicate that regulating both TIA and hydraulic connectivity decreases stormwater runoff. The impact of GI connectivity on runoff depth varies by region. In Chicago, a less linearly connected and more clumped GI configuration decreases runoff depth. Conversely, in Detroit, a less clumped but more linearly connected GI layout is more effective. The findings highlight the importance of developing tailored stormwater runoff management and flood mitigation plans in association with development trends.