Erosion Behavior of Sand-Silt Mixtures: Revisiting the Erosion Threshold

Peng Yao, Min Su, Zhengbing Wang, Leo C. van Rijn, Marcel J.F. Stive, Chunyang Xu, Yongping Chen*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review


The erosion threshold, beyond which bed sediments start to move, is a key parameter describing sediment transport processes. For silt-dominated mixtures, in which the grain size is between sand and clay, existing experimental studies exhibit contradictory observations. That is, the erosion was either sand-like or clay-like, suggesting transitional erosion behavior. To explore the underlying mechanism of the transitional erosion behavior of silt-sized sediment, we revisited the topic of the erosion threshold of sand-silt mixtures by carrying out a series of erosion experiments for different bed compositions. The results suggest that there exists a critical silt content of approximately 35%, separating two domains. Below this critical value, the critical bed shear stress follows the Shields criterion, whereas above this value, the erosion threshold of a mixed bed increases abruptly and remains relatively constant with a further increase in silt content. By combining with existing data, we found that the proposed critical silt content acts as a tipping point, beyond which the mixed bed shifts from a sand-dominated to a silt-dominated domain. For the silt-dominated domain, a stable silt skeleton can be formed by attraction forces that resist erosion. However, the attraction forces are too weak to form a stable silt skeleton when the silt content is too small. Based on this finding, a modified critical bed shear stress formula is proposed for silt-dominated mixtures, which results in a better agreement with experimental data (an averaged bias of 10%), performing better than existing formulas (larger than 30%).

Original languageEnglish
Article numbere2021WR031788
JournalWater Resources Research
Issue number9
Publication statusPublished - 2022

Bibliographical note

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.


  • critical bed shear stress
  • erosion threshold
  • flume experiment
  • sand-silt mixtures
  • silt content


Dive into the research topics of 'Erosion Behavior of Sand-Silt Mixtures: Revisiting the Erosion Threshold'. Together they form a unique fingerprint.

Cite this