Rainfall simulation experiments on roads

Rainfall simulation offers a rapid and efficient means of undertaking hydraulic, hydrologic and water quality studies on roads, both paved and unpaved, and minimises disruption of traffic. The alternative of monitoring is far more costly, and there is no control on the magnitude of rainfall and runoff events during the period of monitoring. This paper presents details of a rainfall simulator designed and constructed for use in a number of road and road pavement experiments in Australia. Details of the design are presented along with issues involved in undertaking experiments. The rainfall simulator has the potential to include catchment areas of several hundred square metres of road surface and simulate rainfalls up to and beyond 1000year average recurrence intervals. The paper addresses some of the issues related to selection of the area of pavement set aside for simulation, the source of water, the design storms, boundary effects and real-time analysis of data and feedback into the experimental design. Examples of the application of the rainfall simulator are given from experiments conducted in the Blue Mountains of NSW and the Mornington Peninsula of Victoria in Eastern Australia