Stochastic model for generating hourly hyetographs

This article describes the construction and the applications of a model to generate hourly rainfall hyetographs. It was developed as a tool for estimating design floods on a small catchment by converting long series of rainfall data (1000 yr) into runoff by means of an appropriate transfer function model. Its performance is assessed through frequency analysis of 1-, 2-,..., 24-h maximum rainfalls. The means and standard deviations of the simulated maximum rainfall distributions are in the same order of magnitude as the values estimated from observed data. Simulated extreme values are distinctly greater than those obtained by extrapolation of the observed series with a simple exponential probability function. The geographical extension of the model is encouraging, as shown by results from three rainfall recorders at three sites on the Mediterranean seaboard displaying different rainfall patterns.