Water Table Fluctuation from Green Infrastructure Sidewalk Planters in Philadelphia

Abstract

Popularity of infiltration-based green infrastructure (GI) has spurred concern about rising groundwater tables and the potential detrimental effect on building foundations. This study examines water table fluctuations adjacent to green infrastructure sidewalk planters during two winters (2014–2015 and 2016–2017) in Philadelphia. Groundwater mounding is observed in the latter period but not the former. Due to the proximity to a park, the water table rise is the combined effect from both the GI and the park. For the first winter, the sidewalk planters were not fully vegetated or maintained. It is hypothesized that the increased groundwater mounding in 2016–2017 was from the increased infiltration rate caused by improved vegetation and maintenance. Groundwater mounding was not observed beyond 3 m from the GI except for large storms. Because the water table rise was transient, groundwater mounding had minimal impact beyond 3 m for current GI configurations and soil conditions. The observations conform to prior computer simulations. The results also show that intraseason water table fluctuations are far greater than those created by local infiltration.