Temporal evolution of stormwater basin soil properties and infiltration rates

Infiltration-based green stormwater infrastructure (GSI) practices are widely used to mitigate the hydrologic impacts of urbanization. However, how GSI performance evolves over time remains poorly understood. In particular, there is little consensus among published studies on whether GSI infiltration rates increase, decrease, or remain constant as GSI practices age. To address this gap, we hypothesized that GSI soil properties change with age and these changes drive corresponding changes in the infiltration rate. Soil properties and infiltration rates were measured in 28 stormwater infiltration basins along a chronosequence ranging in age from 2 to 20 years. Clay, silt, and organic matter contents increased with age while bulk density decreased with age, suggesting that vegetation and soil biota activity as well as fine sediment accumulation contributed to soil profile evolution. Age, clay, silt, and organic matter correlated with infiltration rate, whereas bulk density and porosity did not. Percent silt content was the best predictor of infiltration rate (R2 = 0.46–0.65, p < 0.001); however, age alone provided moderate predictive power (R2 = 0.16–0.45, p = 0.035–0.001). The best performing single and multiple regression models of infiltration rate used age, organic matter, and silt as predictors (R2 = 0.61–0.65, p < 0.001). These data and models revealed that infiltration rate decreased with basin age and silt content, and increased with organic matter, providing a quantitative link between soil properties and infiltration rate evolution with basin age.