Hydraulic Interpretation of Sand Size Distributions

1976/07/01 by Gerard V. Middleton · 284 citations
Agricultural and Biological Sciences · Earth and Planetary Sciences · Environmental Science · Mathematics · #Bed load #Bedform #Classification of discontinuities #Environmental science #Fluvial #Geological formations and processes #Geology #Geomorphology #Geotechnical engineering #Grain size #Hydrology (agriculture) #Hydrology and Sediment Transport Processes #Mathematics #Mechanics #Petrology #Physics #Sediment #Sediment transport #Settling #Shear (geology) #Soil erosion and sediment transport #Structural basin #Suspension (topology) #Traction (geology) #Turbulence

paper · doi:10.1086/628208

published in The Journal of Geology 84(4), 405-426 (University of Chicago Press)

openalex publication_date 1976/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

Grain size distributions commonly show discontinuities and straight line segments when plotted (using the phi transformation) on probability paper. The different components making up the distribution have commonly been interpreted as subpopulations of grains moved by different transport mechanisms. The paper considers this hypothesis for the restricted case of the two coarsest components observed in many samples of river bed materials. By comparing analyses of bed materials and suspended load, it is shown that the components may be interpreted as (C) traction, and (A) intermittent suspension subpopulations, moved by the dominant discharge of the river. From an analysis of theory, experiments and field data on turbulence in open channels, it is shown that a satisfactory though approximate hydraulic criterion for separating the two mechanisms of sediment transport is as follows: grains move by traction if their settling velocity is larger than the shear velocity of the stream, and by intermittent suspension if their settling velocity is smaller than the shear velocity. This criterion is confirmed by comparison with hydraulic and sediment data for the Middle Loup, Niobrara, Elkhorn, Missouri, Mississippi and Rio Grande Rivers. Consequently, it should be possible to determine the dominant shear velocity of ancient fluvial sands by determining the size "break" between their two coarsest components.

Cited by

• Formation process of the gravel‐dominated deposit from the 2011 Tohoku‐oki tsunami in Ofunato, northeastern Japan, inferred by integrating sedimentology and tsunami modelling
• Discrimination between coastal subenvironments using textural characteristics
• Contemporary accumulation of marine sand in a macrotidal estuary, southwest Wales
• Grain-size distribution function of polymodal sediments in hydraulic and aeolian environments, and numerical partitioning of the sedimentary components
• Morphological analysis of mineral grains from different sedimentary environments using automated static image analysis
• A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis
• Variability of deltaic processes in terms of sediment supply, with particular emphasis on grain size

Related

• Interpretation of Polymodal Sediments
• The nature of saltation and of ‘bed-load’ transport in water
• The formation and migration of sand ripples in closed conduits: experiments with turbulent water flows
• Bedforms in a turbulent stream.Part 2: Formation of ripples by primary linear instability and of dunes by non-linear pattern coarsening
• Flow resistance in alluvial channels