The average bed shear stress and bed friction factor of samples with any roughness was derived from the head loss between upstream and downstream of a test section in an erosion tunnel. The method was validated in both hydraulically smooth (plexiglass; Reynolds number less than 25,000) and rough regimes (calibrated particles with known roughness). As a first step toward using this method on nat...

Accurate forecasts of bed forms and their roughness during a flood wave are essential for flood management. Bed forms remain dynamic even under steady discharge and are subject to a continuous process of creations and destructions of individual bed forms. Dune evolution during the rising limb of a flood wave is quite well understood and can be modeled. However, dune evolution during the falling...

Hydrodynamic river models are applied to design and evaluate measures for purposes such as safety against flooding. The modeling of river processes involves numerous uncertainties, resulting in uncertain model results. Knowledge of the type and magnitude of these uncertainties is crucial for a meaningful interpretation of the model results. The aim of this study is to quantify the uncertainty d...

A numerical model based on the smoothed particle hydrodynamics method is developed to simulate depth-limited turbulent open channel flows over hydraulically rough beds. The 2D Lagrangian form of the Navier-Stokes equations is solved, in which a drag-based formulation is used based on an effective roughness zone near the bed to account for the roughness effect of bed spheres and an improved sub-...

Whether or not a sediment particle is entrained from a channel bed is associated with both average bed shear stress and shear stress fluctuation, the latter being flow-dependent and also related to bed irregularities. In the first part of this study, a preliminary analysis of possible fluctuations induced by bed roughness is presented for the case of immobile plane bed comprised of unisized sed...

A new relationship between the roughness height and the main hydrodynamic and sediment parameters for plane beds under oscillatory conditions is presented. In order to derive such a relationship, a large data base encompassing plane-bed experiments was compiled from previous investigations and analyzed. Different methods to estimate the roughness height were investigated. Comparisons between th...

Turbidity currents in the ocean and lakes are driven by suspended sediment. The vertical profiles of velocity and excess density are shaped by interaction between the current and bed as well as between the current and the ambient water. This paper presents 48 series of experiments in which saline gravity currents flow through a laboratory sinuous flume. flume contains three successive bends wit...

Density or gravity currents have been always one of the main causes for sedimentation along many of the dam reservoirs. So controlling this phenomenon is very important for increasing useful life of such reservoirs. In this research study the effect of a combination of rough bed and obstacle on the control of sedimentary density current has been investigated. Experiments were conducted in a til...

Alluvial channel stage-discharge and depth-discharge relations were studied in a large sand-bed recirculating flume. From this study, it was found that the form of these relations are intimately related to: 1. Regime of flow 2. Form of bed roughness a. Characteristics of the bed material b. Concentration of fine sediment c. Temperature 3. Rate of change of discharge with time In the range of sh...

[1] Data from laboratory flumes and natural streams show that the critical Shields stress for initial sediment motion increases with channel slope, which indicates that particles of the same size are more stable on steeper slopes. This observation is contrary to standard models that predict reduced stability with increasing slope due to the added downstream gravitational force. Processes that m...