Sediment pulses and extreme events: Assessing the effect of storm characteristics on propagation dynamics

Abstract

The objective of this research is to assess the effect that extreme hydrologic events have on the propagation of sediment pulses in river corridors. These sediment-flow hazards are associated with large amounts of loose material suddenly deposited in rivers by the action of external factors or processes of natural or anthropogenic origin, including landslides, debris flows from tributaries, dam removal projects, and mining-related activities. Their occurrence is associated with severe channel aggradation and degradation, floodplain deposition, damage of infrastructure, and impairment of riparian and aquatic ecosystems. Given that the intensity of rainfall events have been significantly enhanced due to the influence of various human activities, sediment pulses are expected to become more common, with a more pronounced downstream impact as such climatic changes directly affect the magnitude, duration, and frequency of flows in riverine environments. Herein, numerical simulations were performed to characterize the propagation of a fine-grained sediment pulse for the 10-, 100-, and 500-yr storms. Results indicate that magnitude, frequency, and duration of the storms primarily influence the temporal variation of the total sediment discharge. In particular, these storm characteristics have a marked impact on the relationship between pre- and post-pulse conditions in the river channel, the dissipation of the pulse peak discharge, and the travel time of the pulse apex.