Hydrologic Characterization of Undrained Porous Pavements

Abstract

Results of a simplified analysis of the hydrologic performance of undrained porous pavements, pavements without underdrains but that allow infiltration, are reported. The characterization of porous pavement behavior presented is appropriate for initial pavement design purposes. During any given storm, there are four distinct phases of porous pavement behavior: infiltration, accumulation, runoff, and drawdown. Analytical and graphical methods are presented for describing each of these phases from which a nonconvoluted approximate runoff hydrograph can be derived. This approach approximates peak runoff and time of that peak for a given storm depth, rainfall distribution, and pavement design. Second, a generalized method for calculating a porous pavement’s effective curve number (ECN) based on the National Resources Conservation Service (NRCS) [formerly Soil Conservation Service (SCS)] runoff curve number is presented. The analysis shows that for undrained porous pavements, the ECN is a function not only of the pavement and soil properties, but also of the storm depths and hyetographs used in the analysis. A standard calculation and presentation method is suggested that will allow local regions or municipalities to generate a local ECN design tool appropriate for their intensity-duration-frequency (IDF) data, which are only a function of the effective storage depth and the daily effective soil infiltration depth. A plot of the maximum ECN for all pavement depths and soil types is presented for each NRCS storm type as a reference for generating local ECN figures.