Experimental evidence for fl uvial bedrock incision by suspended and bedload sediment

摘要

Fluvial bedrock incision sets the pace of landscape evolution and can be dominated by abrasion from impacting particles. Existing bedrock incision models diverge on the ability of sediment to erode within the suspension regime, leading to competing predictions of lowland river erosion rates, knickpoint formation and evolution, and the transient response of orogens to external forcing. We present controlled abrasion mill experiments designed to test fl uvial incision models in the bedload and suspension regimes by varying sediment size while holding fi xed hydraulics, sediment load, and substrate strength. Measurable erosion occurred within the suspension regime, and erosion rates agree with a mechanistic incision theory for erosion by mixed suspended and bedload sediment. Our experimental results indicate that suspension- regime erosion can dominate channel incision during large fl oods and in steep channels, with signifi cant implications for the pace of landscape evolution.