Percolation through leaf litter: what happens during rainfall events of varying intensity?

Simulated rainfall experiments with a layer of eucalypt leaf litter showed that the flux of percolate emerging from the layer was influenced by the intensity profile of the incident rainfall. Experiments involved several different fixed rainfall intensities, and also seven different temporal patterns of changing intensity (event profiles). The event profiles all had a mean intensity of 10 mm/h and the same 30 min duration, but included intensity bursts or peaks of up to 100 mm/h early or late within the event, as well as events with multiple intensity peaks. The litter percolate flux associated with early rainfall intensity peaks was typically attenuated by nearly 50% in comparison with the intensity of the incident rainfall. In contrast, percolate flux from late rainfall peaks was often magnified, in some cases by up to 360% . Even under rainfall of constant intensity, the percolate flux exhibits fluctuations of about ±25 of the mean flux. In most cases, peaks in percolate flux lagged peaks in the incident rainfall by 4-5 min. The potential importance of diminished or enlarged litter percolate fluxes is their effect on water partitioning and the potential for lateral flow within and beneath litter layers, especially if the peaks in percolate flux exceed local soil infiltrability.