A Qualitative Analysis of the Distribution of Bed-Surface Elevation and the Characteristics of Associated Deposits for Subaqueous Dunes

  1. Michael D. Blum3,
  2. Susan B. Marriott4 and
  3. Suzanne F. Leclair5
  1. Suzanne F. Leclair5 and
  2. Astrid Blom1,†

Published Online: 17 MAR 2009

DOI: 10.1002/9781444304350.ch7

Fluvial Sedimentology VII

Fluvial Sedimentology VII

How to Cite

Leclair, S. F. and Blom, A. (2009) A Qualitative Analysis of the Distribution of Bed-Surface Elevation and the Characteristics of Associated Deposits for Subaqueous Dunes, in Fluvial Sedimentology VII (eds M. D. Blum, S. B. Marriott and S. F. Leclair), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304350.ch7

Editor Information

  1. 3

    Baton Rouge, Louisiana, USA

  2. 4

    School of Geography and Environmental Management, University of the West of England, Bristol BS16 1QY, UK

  3. 5

    Department of Earth and Environmental Sciences, Tulane University, Dimwiddie Hall, New Orleans, LA 70118, USA

Author Information

  1. 1

    WL/Delft Hydraulics, P.O. Box 177, 2600 MH Delft, The Netherlands

  2. 5

    Department of Earth and Environmental Sciences, Tulane University, Dimwiddie Hall, New Orleans, LA 70118, USA

  1. Department of Civil Engineering, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands

Publication History

  1. Published Online: 17 MAR 2009
  2. Published Print: 15 FEB 2005

Book Series:

  1. Special Publication Number 35 of the International Association of Sedimentologists

Book Series Editors:

  1. Ian Jarvis

Series Editor Information

  1. School of Earth Sciences and Geography, Centre for Earth and Environmental Science Research, Kingston University, Penrhyn Road, Kingston-upon-Thames KT1 2EE, UK

ISBN Information

Print ISBN: 9781405126519

Online ISBN: 9781444304350

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Keywords:

  • bed-surface elevation and characteristics of associated deposits;
  • controls on probability distribution of bed-surface elevations;
  • cross-set formation model;
  • sediment continuity models;
  • bed-elevation probability distribution and dune geometry;
  • effect of initial vertical sorting;
  • dune deposits as clues for reconstructing bed-elevation probability distribution

Summary

This paper analyses controls on the probability distribution of bed-surface elevations, Ps, and the structure and texture of the associated deposits, in dune-forming conditions. It is important to understand these controls in order to develop predictors required to implement a new theory that is based on a probabilistic approach of the Exner equation for sediment continuity, and to improve the interpretation of sedimentological records of fluvial origin. Experiments were conducted in three flumes of different sizes, with flow depth ranging from 0.15 to 0.87 m, flow velocity ranging from 0.5 to 0.84 m s−1, and with sand-to gravel-dominated mixtures. Distributions of bed-surface elevations were measured from time-series and/or successive bed profiles. Vertical profiles of bed composition (i.e. vertical sorting) and/or structure (i.e. cross-sets) of the deposits were analysed.

Results show that the dimensionless bed shear stress and vertical sorting are the major controls on the range and shape of the non-dimensional Ps curve. Here, the dimensionless bed shear stress is used as a component of the sediment transport stage. Low values of sediment transport stage produce Ps curves that are short-ranged and quite evenly spread around the average bed level. The presence of a coarse bed layer, which affects the composition of the transported sediment, has a similar effect on the Ps curve. Otherwise, the Ps curves tend to be skewed toward the lowest values of bed surface elevation. Interactions between sediment transport stage, vertical sorting, dune height, and the Ps curves mean that the last of them can be partially reconstructed from the analysis of the geometry and texture of cross-sets. The distribution of elevation of cross-set lower boundaries mimics the Ps curve toward its lower limit. The ratio of mean dune height over flow depth indicates approximately the upper limit of the Ps curve, and these variables can be estimated via cross-set thickness distribution. It is hoped that this study will help develop a comprehensive theory that could predict sediment transport from the characteristics of dunes and their deposits, and vice-versa.