Effect of sediment deposition on the efficiency of Fayoum weir

• The bed sediment upstream Fayoum weir is a positive effect on the flow characteristics.
• The increase of head weir ratio (H/P) and channel bed slope cause increase in Fayoum discharge coefficient.
• Developed new discharge–head relationship in the case of bed sediment and no sediment in upstream Fayoum weir.
• Developed empirical formulae give agreements results with experimental data (percentage of error 2.7%).

Weirs are one of the main heading-up water structures. It is constructed along waterways to control the head, discharge and sometimes load sediment. The sedimentation depth increases upstream a weir due to decreasing velocity in the zone of backwater curve and the flow passes over the crest level. The main objectives of this research are to study the effect of bed sediment depth and length in upstream of weir on the flow characteristics and the weir efficiency. The research methodology included experimental, theoretical and statistical studies. The depths of sedimentation are taken 25%, 50%, 75%, and 100% of the weir height and the lengths of sedimentation are taken 50%, 100%, 150%, 200% and 250% of the weir height. All models are tested at different channel bed slopes, 0:0, 1:500, 1:250, 1:200 and 1:150. The discharge coefficient Cd increases as the ratio of H/P increases for no sediment and for different upstream sediment depths. New discharge stage relationship is developed for case of sediment and no sediment upstream the Fayoum weir. In addition, different empirical formulae are obtained for computing the discharge coefficient in case of upstream sediment Fayoum weir.