A modelling of a dimensionless synthetic unit hydrograph

Abstract

When use of a synthetic unit hydrograph on ungauged and non-comparable catchments is required, a further complication is how to choose a suitable time-step to use. The computed time-step is rarely an integral multiplier or divider of the rainfall time-step thus necessitating reanalysing the rainfall chart, at the new time-step. It would be easier if the time-step of the unit hydrograph could be expressed as a continuous function. In February 1995 there was a flash flood in mid-Eastern Botswana which resulted in all gauges being washed away. The only available data were from upland recording rain gauges from which the reconstruction of the flood hydrograph had to be done. Use of a dimensionless synthetic unit hydrograph (DSUH) was indicated. This is the first part of a two-part paper which involves analyticising (transforming a numerical/graphical function into a continuous one i.e. rendering it analytical) the dimensionless unit hydrograph i.e. developing a piecewise/zonal continuous function of time vs. the runoff.

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