PREDICTIONS OF STRATIGRAPHIC ARCHITECTURE IN RELATION TO CHANNEL MOBILITY OF DRYLAND RIVERS: INSIGHT FROM THE MOJAVE RIVER OF CALIFORNIA (USA)

Exploring the relations between flood frequency and channel migration in ephemeral, dryland rivers may improve our understanding of watershed biogeochemistry and river morphogenesis in desert landscapes, but also inform predictions of stratigraphic architecture on, e.g., early Earth and Mars. We present an integrated analysis of discharge, time-lapse remote sensing, and chronologically calibrated subsidence rates from the Mojave River of California (USA), which is one of the largest watercourses in the Great Basin of the western USA. Estimations of formative-flood conditions reveal a slight downstream decrease in bankfull discharge along the Mojave River, rather than the downstream increase that is typically observed in perennial streams of more humid climate zones. Notwithstanding, an analysis of bankfull-discharge intermittency shows that the number of days per year during which the channel experiences formative or higher stages is roughly maintained along the river’s length. Historical peak-flood records suggest that, over timespans of decades to centuries, the incidence of channel-formative events might have responded to modulation in watershed runoff due to the varying precipitation in the river’s headwaters. Thanks to our integrated analysis, we eventually predict that, while maintaining hydraulic sections that are fully comparable with many other rivers worldwide, dryland desert streams such as to the Mojave River may generate a surprisingly wide range of depositional geometries in the stratigraphic record.