Bedrock-alluvial streams with knickpoint and plunge pool that migrate upstream with permanent form

Li Zhang, Toshiki Iwasaki, Tiejian Li, Xudong Fu, Guangqian Wang, Gary Parker

Research output: Contribution to journalArticle

Abstract

Purely alluvial rivers cannot sustain knickpoints along their long profiles, as they would be obliterated by diffusional morphodynamics. Bedrock streams with a partial alluvial cover, however, form and sustain slope breaks over long periods of time. Here we consider the case of an initial profile of a bedrock-alluvial stream with a sharp slope break, or knickpoint, from high to low midway. We show that if the initial flow is sufficiently Froude-supercritical in the upstream reach and Froude-subcritical in the downstream reach, a three-tiered structure can evolve at the slope break: a hydraulic jump at the water surface; a scour hole in the alluvium above the bedrock, and a plunge pool carved into bedrock. Once the profile adjusts to balance uplift, it can migrate upstream without changing form.

Original languageEnglish (US)
Article number6176
JournalScientific reports
Volume9
Issue number1
DOIs
StatePublished - Dec 1 2019

ASJC Scopus subject areas

  • General

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