Temporal variation of intermittent surges of debris flow

SummaryDebris flows (especially those of high-density or high viscosity) usually appear in the form of surge sequence. Each debris flow event consists of tens or hundreds of surges. A debris flow is thus equal to a surge series which is expected to feature the intrinsic properties. Statistics of observation data indicates that different events have the similar distributions in parameters such as velocity, flow depth, discharge, runoff, and time interval, which can be considered as the signs of an underlying dynamics. But there are currently difficulties in extracting the dynamics from the surge series. This paper is concerned with the temporal variations of surge series based on observation data in the last forty years in Jiangjia Gully (JJG). The temporal process of a surge series is characterized by the accumulative curve of the interval time. A surge series is found to be dominated by the peak discharge in that the peak discharge determines the exponent of the distribution. Moreover, the average discharge evolves with surge progress and finally decays in a power-law form. It follows that a surge series behaves as a whole which requires a unified dynamical framework to encompass all the appearances.