Hydrologic Performance of Permeable Pavers and a Dome Concrete Forming System: A Comparative Study

The hydrologic performance of permeable interlocking concrete pavers (PICP) and a dome concrete forming system (DCFS) was quantified and evaluated at a retrofitted residential laneway in Toronto, Ontario. The quantification and evaluation were performed by comparing their monitored performance over 14 months with an adjacent concrete pavement. Their monitored performance was then used to assess their ability to mimic predevelopment hydrologic behavior, estimated through modeling. The PICP and DCFS achieved (1) an average runoff volume reduction of 33% and 85%; (2) an average runoff coefficient of 0.48 and 0.12; and (3) an average peak flow reduction of 43% and 89%, respectively. The outflow duration from the DCFS was extended 4.1 times greater than the inflow duration, indicating its potential to attenuate flashy events. The peak flows produced by the DCFS were delayed by nearly 2.5 h from those occurring on the PICP. Correlation analyses indicated a more significant influence of rainfall depth and intensity on the performance of PICP than that of the DCFS. Compared with predevelopment levels, PICP did not match runoff volumes for smaller events ($<10\mathrm{mm}$) but produced less runoff for larger events ($>30\mathrm{mm}$). However, the PICP did not match predevelopment peak flows in 100% of occurrences. The DCFS reduced runoff volumes and peak flows to magnitudes lower than all predevelopment levels. Surface infiltration testing and subsurface hydraulic conductivity estimations indicated that infiltration capability in both systems could be reduced over time. The study demonstrated that the DCFS might need to be prioritized over permeable pavements, especially when installed over low-permeability soils.