Original paper

Rainfall simulator experiments on the importance o of when rainfall burst occurs during storm events on runoff and soil loss

de Lima, João L.M.P.; Carvalho, Sílvia C.P.; P. de Lima, M. Isabel

Abstract

The influence of the temporal structure of rainfall on the discharge hydrographs and associated transport processes has not yet been fully explored. Nevertheless, the expectation is that characteristics of the rain spells have important effects on both runoff and soil loss, in particular the time when heavy rainfall bursts occur during storm events. This experimental study focuses especially on the influence of when such bursts occur during rain storm events of equal duration and depth on runoff and soil loss processes. Laboratory experiments were conducted using a rainfall simulator and a soil flume to study the different responses caused by rain events characterized by a constant base intensity interrupted by short 5-minute rainfall bursts. These bursts occurred at different times during the event. On average, the greatest runoff and amount of sediment transported were caused by the rainfall bursts that occurred later in the event. Results obtained in the laboratory experiments are expected to represent the response typical of advanced, centred and delayed rainfall patterns. Thus, rain storm temporal variability and patterns should be considered in the definition of design hyetographs for rainfall-runoff and rainfall-erosion modelling. Ignoring the time of occurrence of the heaviest rain intensity within storm events can cause both under and over estimation of runoff discharge and soil loss.

Keywords

rainfall patternrainfall simulationrunoffsoil losslaboratory experiments