The projected impacts of smart decline on urban runoff contamination levels

There has been mounting interest about how the repurposing of vacant land (VL) through green infrastructure (the most common smart decline strategy) can reduce stormwater runoff and improve runoff quality, especially in legacy cities characterized by excessive industrial land uses and VL amounts. This research examines the long-term impacts of smart decline on both stormwater amounts and pollutants loads through integrating land use prediction models with green infrastructure performance models. Using the City of St. Louis, Missouri, USA as the study area, we simulate 2025 land use change using the Conversion of Land Use and its Effects (CLUE-S) and Markov Chain urban land use prediction models and assess these change’s probable impacts on urban contamination levels under different smart decline scenarios using the Long-Term Hydrologic Impact Assessment (L-THIA) performance model. The four different scenarios are: (1) a baseline scenario, (2) a 10% vacant land re-greening (VLRG) scenario, (3) a 20% VLRG scenario, and (4) a 30% VLRG scenario. The results of this study illustrate that smart decline VLRG strategies can have both direct and indirect impacts on urban stormwater runoff and their inherent contamination levels. Direct impacts on urban contamination include the reduction of stormwater runoff and non-point source (NPS) pollutants. In the 30% VLRG scenario, the annual runoff volume decreases by 11%, both physical, chemical, and bacterial pollutants are reduced by an average of 19%, compared to the baseline scenario. Indirect impacts include reduction of the possibility of illegal dumping on VL through mitigation and prevention of future vacancies.

How U.S. Shrinking Cities Plan for Change: Comparing Population Projections and Planning Strategies in Depopulating U.S. Cities

This research examines the mismatch between the reality of a city’s population loss and the planning strategies they have adopted. Thirty-five depopulating U.S. cities’ comprehensive plans are analyzed to determine whether they are acknowledging past depopulation trends, how they are projecting future population changes, and what planning strategies they are pursuing in light of their depopulation trends. Findings illustrate a majority of cities acknowledge depopulation; however, they rely on optimistic population projections for the future. Despite this, a mix of planning strategies, ranging from smart decline to pro-growth, are used regardless of a city’s acknowledgment/acceptance of population loss.