Changes in Bedform Dimensions under Unsteady Flow Conditions in a Straight Flume

  1. J. D. Collinson and
  2. J. Lewin
  1. J. H. A. Wijbenga Project Engineer and
  2. G. J. Klaassen Project Advisor

Published Online: 29 APR 2009

DOI: 10.1002/9781444303773.ch3

Modern and Ancient Fluvial Systems

Modern and Ancient Fluvial Systems

How to Cite

Wijbenga, J. H. A. and Klaassen, G. J. (1983) Changes in Bedform Dimensions under Unsteady Flow Conditions in a Straight Flume, in Modern and Ancient Fluvial Systems (eds J. D. Collinson and J. Lewin), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444303773.ch3

Author Information

  1. Delft Hydraulics Laboratory, Rivers and Navigation Branch, P.O. Box 152, Emmeloord, The Netherlands

Publication History

  1. Published Online: 29 APR 2009
  2. Published Print: 7 FEB 1983

ISBN Information

Print ISBN: 9780632009978

Online ISBN: 9781444303773



  • changes in bedform dimensions under unsteady flow conditions in straight flume;
  • flume tests at Delft hydraulics laboratory;
  • flume experiments;
  • differences in dune celebrities for tests;
  • Allen's computational model


Flume tests are being carried out at the Delft Hydraulics Laboratory to study the changes in bedform dimensions and resistance to flow for unsteady flow conditions. The tests are carried out in a straight flume with uniform bed material (Dm = 0.77 mm). Results are presented for a sudden increase or decrease of the discharge. A comparison is made with the experiments by Gee (1973) and the theoretical work by Allen (1976a and subsequent articles) and Fredsøe (1979). It is concluded that a linear first-order differential equation with constant coefficients for the change in bedform dimensions does not fit the measured change in bedform dimensions. The coefficient of adaptation appears to be higher for decreasing discharges than for increasing discharges. The dune excursion as used in Allen's (1976a) computational model is in the order of 1–2, slightly increasing for increasing water depth. Furthermore, it is concluded that Fredsøe's (1979) method does not correctly simulate the phenomena observed during the tests in the flume with a large change in discharge. To predict the resistance to flow of the minor bed of the Rhine branches in the Netherlands during extreme flood conditions an adaptation of both the computational method of Allen (1976a, b, c, 1978) and Fredsøe (1979) is needed.