ABSTRACT
Intensive measurements have been conducted experimently to get an accurate assessment for hydraulic roughness of the alluvial beds which is considered to be an essential parameter in determining of many hydraulic relations such as stage discharge, water level, design of water ways, degradation and aggradation. The experimental tests include six different types of alluvial materials, each type has a grain size distribution which can be characterized by its median diameter and geometric standard deviation. Those two parameters, for the involved experimental materials, are as follows: 0.089 mm, 1.42 & 0.210 mm, 1.3 & 0.235 mm, 1.85 & 0.390 mm, 1.65 & 1.070 mm, 3.31 & 1.960 mm, 2.95 & 4.0mm, 2.0.
In all tests the main hydraulic parameters such as: flow discharge, depth, slope and bed configuration were measured. The hydraulic roughness is expressed in this research by Chezy coefficient. It has been found that the Chezy coefficient is highly affected by the following three parameters: relative roughness, bed material characteristics and the geometry of the bed forms. Also, the Chezy coefficient was found to be proportional to the relative roughness in the case of the planed beds, while for the formed bed the adverse result was found.
