Characterization of Undrained Porous Pavement Systems Using a Broken-Line Model

Abstract

Past attempts at characterizing the hydrologic response of porous pavement systems have not distinguished between the different behaviors of drained and undrained pavements. Most models used that are appropriate for traditional catchments can be applied successfully to drained porous pavements; however, these models do not match the expected hydrologic behavior of undrained porous pavements. Undrained porous pavements exhibit a fill-and-spill response to rainfall events. While forcing an undrained pavement’s fill-and-spill behavior into a conventional runoff model may simplify design, it does so at the cost of accuracy. This research models the rainfall-runoff relationship for undrained porous pavements and proposes a broken-line model as an appropriate characterization of the behavior. The breakpoint of the model represents the initial abstraction of the pavement, and the slope of the upper line is primarily a function of the infiltration capacity of the underlying soil. Because both the initial abstraction and slope are functions of the pavement storage capacity and 24-h infiltration depth, a broad range of pavements were modeled and the results were compiled into figures, allowing the direct lookup of the model’s parameters. This new characterization of the hydrologic behavior of porous pavement provides a simple but more accurate model of the actual behavior, which will enable designers and regulators to easily calculate and understand an undrained pavement’s hydraulic behavior.