This paper deals with the study of the geometry of the scour hole and topography of the bed around a T-shaped unsubmerged spur dike located in a 90° bend. The experiments were carried out in a channel with a 90° bend. Uniform sediments having an average diameter of 1.28 mm were used under clear-water scour conditions. The effects of parameters like the length of a spur dike, the wing length of a spur dike, the location of a spur dike in the bend, the radius of bend, and flow intensity on the scour around a T-shaped spur dike were investigated. A new equation for scour parameters at a T-shaped spur dike is developed.

To alleviate the scour depth around a series of existing spur dikes (SDs), a protective SD located upstream of the first was experimentally investigated. To determine the optimal design parameters, various values, lengths, angles and the spacing of a protective SDs were experimentally tested under different clear-water conditions in a straight river reach and a fixed flow depth. To investigate the behaviour of the flow field around the SDs, acoustic Doppler velocimeter was used to measure instantaneous velocity components on a rough rigid bed. The results indicate that a properly designed protective SD is able to decrease the average of the maximum scour depth around the main SDs. The optimum design parameters of a protective SD are recommended for each length for a particular experiment.

This paper experimentally studies the hydraulic characteristics of arced weirs located in a reservoir. The accuracy and ability of the response surface methodology (RSM), especially central composite design (CCD), to describe the hydraulic performance of this type of weir is validated using experimental data. The discharge coefficient of arced weirs is presented as a function of headwater ratio ($H_o/P$ ) and magnification ratio ($L/W$ ) using both traditional and response surface methodologies. The results indicate that like the traditional methodology, RSM-CCD introduces an acceptable model to determine the discharge coefficient of the arced weirs, but it requires a much lower number of experiments. The results show that the discharge coefficient of an arced weir decreases by increasing $H_o/P$ and $L/W$ [or arc angle ($\mathrm{\Theta }$ )]. In addition, compared to a linear weir, the efficiency of an arced weir can increase up to 50%. Finally, based on the experimental results, a method is introduced for designing the in-reservoir arced weirs.