Modeling Neighborhood-Scale Uncertainty of Impervious Cover Change and its Potential Impacts on Robust Stormwater Management

Cities and metropolitan areas are currently developing climate change impact assessments and strategies for resilience and adaptation. Given the long time horizons for infrastructure planning, construction, and operation, population and land use change are a substantial source of uncertainty. Our research explores several future scenarios for stormwater management in Allegheny County, Pennsylvania. Based on empirical relationships demonstrated in the literature, this paper establishes a new method for calculating change in impervious area from neighborhood and municipal scale population projections. Our work fills a critical gap for these projections, refining prior estimation techniques that operated at either the block or watershed level. The results and their impact on stormwater volumes supported the creation of management scenarios for local planning stakeholders, city government agencies, and regional authorities. This work formed the basis of a participatory framework for improving decisions under deep uncertainty called Robust Decision Making (RDM). The pilot project lent independently verifiable transparency and supplemented the technical rigor of planning for cost-effective green infrastructure strategies. In turn, it contributes to on-going deliberative processes about the potential location and scale of stormwater investments, policies, and other climate-related adaptation projects in the region.

The land use change methodology above was part of a larger study undertaken by the RAND Corporation and funded by a MacArthur Foundation grant.