Rock-ice avalanche flume experiments reveal a non-linear hillslope erosion rule governed by ice-content

Rock-ice avalanches expand greatly in size and hazard potential by eroding bed material as they propagate downslope. And yet, the mechanisms driving hillslope erosion, and particularly the role of ice content, remain unconstrained owing to the scarcity of data available from either field or experimental settings. Here, we investigate the effects of ice content on rock-ice avalanche erosion in a temperature-controlled flume. We find that variations in ice content exert a major influence on erosion capacity. The erosion rate follows a non-linear rule with ice content, increasing to a peak at 40–60% before declining. This pattern remains robust under limited meltwater conditions. This non-linear relationship stems from the competing effects that the increase in flow velocity is offset by the reduced density of high ice-content mixtures. Grain collisional stress demonstrates a strong correlation with erosion rates and exhibits a parallel trend with variations in ice content. This work lays a foundation for predicting rock-ice avalanche entrainment and provides valuable insights into modeling landscape evolution in cryospheric systems.