Surface Flow and Spread Calculations for the Preliminary Design of Porous Pavement Bike Lanes

Abstract

This study investigated methods for predicting and managing surface water spread and depth on porous pavement bike lanes adjacent to impervious traffic lanes. Results are presented from a theoretical and experimental study into the hydraulic performance of porous pavement bike lanes. Analysis of the Saint-Venant equations was used to show that the distance required for water running onto a porous pavement to fully infiltrate into the pavement is linearly proportional to the width of the adjacent impervious traffic lanes and the rainfall intensity. It is inversely proportional to the sum of the rainfall intensity and pavement hydraulic conductivity. This result was validated by a series of large-scale laboratory experiments. A second model is presented for calculating the spacing of curb opening inlets along the side of a porous pavement that is relatively flat in the longitudinal direction. A graphical analysis of the runoff hydrograph that flows into the porous pavement was used to predict the peak discharge per unit length of pavement that must be handled by a curb opening inlet. This peak flow, combined with a local regulatory limit on the spread, leads to a simple algebraic expression for the required length of curb opening inlet per unit length of bike lane. Examples of how both these results can be used in preliminary design calculations are presented.