Erosional Process of Cohesive Sediments

Abstract

Tests on erosion of the cohesive sediments in the Chikugo estuary in Japan were conducted. The results indicate that the decrease in the rate of erosion at constant shear stresses is caused rapidly 20 to 30 minutes after the start of tests and that tue decrease is caused by the increase in the solid fraction and the yield value of the seaiment remaining uneroded due to shear stress. In order to simulate the erosion process of sediments, a model in which the increase in the yield value of sediment is assumed to be proportional to the integration value of the absolute value of the sediment velocity gradient with respect to time was developed. The simulation based on this model is shown to be available to estimate the amount of sediments eroded in the erosional process of cohesive sediments.

Resuspension potential of surficial sediments in Saguenay Fjord (Québec, Canada)

“…Above this threshold, erosion takes place at a rate determined by the excess bed shear stress according to linear (Ariathurai and Arulanandan, 1978), exponential Parchure and Mehta, 1985) or power-law (Kusuda et al, 1984) expressions. There is also a power law expression based on applied bed shear stress without threshold condition (Lavelle et al, 1984) and a generalized exponential expression based on bed shear strength (Dennet, 1995).…”

“…Additionally, geophysical, geotechnical, bottom current and benthic faunal data were also collected over the study area (Maurice, 2000;Ouellet et al, 2001;Schmitt, 2001;Urgeles et al, 2002) in order to obtain information about the characteristics of water-sediment interface. Several authors determined law to define the erosion potential (Ariathurai and Arulanandan, 1978;Kusuda et al, 1984;Parchure and Mehta, 1985). In this study, in order to obtain the best estimation of the resuspension potential of the surficial sediments a new approach had to be developed.…”

Erosion of mud/sand mixtures

“…This behaviour resembles the previously described mass erosion. Kusuda et al (1982) showed the importance of shear stress history on erosion rates. Erosion rates at a certain constant shear are higher than when this same shear stress is reached after a stepwise increase of the shear stress.…”

Dynamic equilibrium of sediment carbon content in an estuarine tidal flat: characterization and mechanisms

“…Unstable fine material on the sediment surface is easily resuspended because of the low threshold of shear stress for entrainment (e.g. Kusuda et al 1984). This physical instability of material deposited on the sediment surface is believed to enable the quick return of sediment carbon content from high to background levels (e.g.…”