Standard Article

138 Unsteady Flow

Part 12. Open-Channel Flow

  1. Walter H Graf,
  2. Mustafa S Altinakar

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa145

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Graf, W. H. and Altinakar, M. S. 2006. Unsteady Flow. Encyclopedia of Hydrological Sciences. 12:138.

Author Information

  1. Ecole Polytechnique Fédérale, Laboratoire de Recherches Hydrauliques, Lausanne, Switzerland

Publication History

  1. Published Online: 15 APR 2006


Flow is unsteady, if the flow depth as well as other hydraulic parameters vary with time. An unsteady flow is usually also nonuniform. The one-dimensional hydrodynamic equations, known are the equations of Saint-Venant, are developed. The simplified equations of Saint-Venant are used to treat the kinematic wave as well as the diffusive wave. The flood wave is also briefly discussed. Numerical solutions to unsteady flow will be treated in a subsequent chapter (see Numerical Modeling of Unsteady Flows in Rivers).


  • open-channel flow;
  • unsteady flow;
  • equations of Saint-Venant, kinematic wave;
  • diffusive wave;
  • flood wave