Effect of Various Spur Dikes Arrangement on Water Depth Changes in Gradually Varied Flow Condition

River spur dikes are constructed for achieving different goals and researches are concentrated on investigation of their performances regarding the desired goals. While they show drastic impact on the flow hydraulic conditions in waterways including water surface elevation which still need further investigation and should be treated seriously. The objective of this study was to investigate the effect of spur dikes on water surface elevation variation. For this purpose, 18 different arrangements of spur dikes installation were experimentally studied. The tests were run for seven discharges in the range of 12 to 70 liters per second and by measuring and recording the longitudinal and transverse water depth along the channel. The spur dikes arrangement consists of eight unilateral arrangements and ten two-way symmetrical and asymmetrical arrangements. The results indicated that the water level increased in the upstream while it decreased at the downstream down to a specific length. The increment of the upstream water level was associated to the exerted drag force on the spur dike; accordingly, a nonlinear equation was proposed to estimate the drag coefficient of the single spur dike. The data also showed that the rate of upstream water level increment has increased by increasing flow discharge for all arrangements, while the length of the downstream, which is affected by the spur dikes, in two-way arrangement is depended on discharge while it is independed in one-way arrangement. The effect of spur dikes arrangement and flow conditions on the transverse water level has also been presented.