A Laboratory Rig for Testing Runoff from Paved Surfaces

When a process is too complex for rigorous mathematical formulation, and simplifying assumptions are introduced for its solution, experimental verification is required, or the approximate numerical model cannot be said to represent the process. Numerical solution of the dynamic wave equations for flow over pavement is such a case. We describe in this chapter a laboratory rig used to test the numerical procedures of the previous chapter (James and Wylie, 2000), and the initial storage theory developed in the previous monograph in this series (James and Johanson, 1999). Our experiments were conducted almost 30 years ago in the Department of Civil Engineering at the University of Natal in Durban. Laboratory conditions were stringently controlled. Experiments are otherwise similar to those recently described by several of the author's graduate students in this series of books. For generality of the mathematical model, the formulation of the wave equations should include a momentum exchange term for rain distributed uniformly over its resulting runoff from the pavement. In the present studies, the mathematical and physical model catchments are also impermeable, to avoid the complexity of infiltration. Under these conditions, the physical and mathematical models may be considered to represent real rain falling on its resultant runoff fro