Like many montane rivers in the western U. S., the Middle Fork of the John Day River is characterized by alternating narrowand wide-valley segments. Although the river has a low gradient (generally < 0.01) alluvial channel, changes in valley width exert a clear infl uence on channel morphology. A spatial hierarchical model of channel morphology was applied to the Middle Fork to understand reach...

Local scour around a cylindrical pier in a channel with an erodible bed or natural bed is a common problems in bridge or pile supported structure. The highly unsteady complex flow field around a circular pier produces scour hole mainly for the presence of vortices. The main mechanism that drives the formation and evolution of the scour hole around bridge pier is horse shoe vortex motion. In the...

This paper presents an experimental research on the distribution of local friction factor, fb, and global friction factor, f, over the cross-section of a channel with V-shaped bottom, which typically occurs in sewers and culverts. Several series of experiments were conducted for measuring velocity and boundary shear stress. It is found that, Darcy-Weisbach, f, is more sensitive than other resis...

introduction the floods particularly in arid regions of iran damage railroads each year. most of the damages are in the rail bridges on stream channels because of the channel bed replacements, sudden rainfalls and disjointed bed materials. dry channels of the streams, the flat surface of the ground, and lack of vegetation cover result in seasonal and annual channel bed replacements. these chann...

abstract the concept of armouring is used to discuss the coarse surface layer in rivers. selective erosion in an alluvial channel reach for which there is no upstream sediment supply can lead to formation of a layer coarser than the under laying material. this phenomenon inhibits sediment transport from the reach.numerical modeling of armouring river bed, provides an approach to simulation of t...

The accurate representation of morphodynamic processes and the ability to propagate changes in the riverbed over a wide range of space and time scales make the design and implementation of appropriate numerical schemes challenging. In particular, requirements of accuracy and stability for medium and long term simulations are difficult to meet. In this work, the derivation, design, and implement...