A Note on an Inherent Difficulty with the Unit Hydrograph Method
This chapter presents previously unpublished work of sometime ago. However, the topic remains timely: the re-appraisal of a popular class of simplified, non--deterministic theories regarding the link between rainfall at the ground surface and the resulting runoff. It is shown that linear unit hydrograph theory overlooks the inherent non-linearity in the time dimension of the process. A modified approach, herein called the initial storage theory (IST), is proposed, and tested in the laboratory using a pavement-rainfall-runoff rig.
We deem a theory to be adequate if it permits the accurate calculation of important features of the runoff resulting from a given rainstorm, and conclude that the IST is an improvement over the basic unit hydrograph method. Experiments will be presented in a separate publication; basic methodology is demonstrated herein.
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