Rapidly varying transient flows in alluvial rivers

Abstract

Extensive changes can occur in alluvial river morphology over relatively short time periods due to such extreme events as a flash flood or flood resulting due to dam break or dike failure. In the present paper the results obtained through the application of a fully coupled one-dimensional alluvial river model are presented for simulation of such sharp hydraulic and bed transients in an alluvial river. Here the governing system of partial differential equations was discretized by making use of the generalized Preissmann finite difference scheme. The resulting set of non-linear partial difference equations was solved by using Newton Raphson iterative procedure in which the solution for banded matrix of Jacobians was obtained through a hexa-diagonal solution algorithm. The model presented herein has been validated through a number of proofs of the concept tests and by simulating the Quail Creek Dike failure which occurred on 31 December 1988 and 1 January 1989 in Washington County, Utah, USA. The present model was further extended to simulate the processes of grain sorting, wash load transport and non-equilibrium sediment transport. The results obtained from these simulations are presented in this paper.

Keywords:

• Alluvial
• dike
• grain sorting
• flood
• non-equilibrium transport
• transients
• wash load