To divert water from rivers, several structures can be employed. Bottom intake is one of the hydraulic structures which is generally used for this purpose in steep streams. Bottom racks are associated with the problems such as deformation, corrosion, vibration and clogging by foliage, sediments, and freezing. A new type of bottom intakes is introduced to overcome these difficulties in which the racks are replaced by a trench filled with a coarse porous medium. In the present study, we analyze the experimental results of a systematic series of measurements conducted in a two-storey laboratory flume. Measuring the diverted discharge is done alongside other important factors such as grain size distributions, total and remained discharges, velocity, and intake geometric properties. Furthermore, the results of our experiments are compared with those obtained from the formulas proposed in previous studies. The hydraulic characteristics of these formulas are investigated, and the necessary points for their improvement are determined. Also, we introduce new formulas for estimating discharge coefficient and diversion rate based on dimensional analysis, our experimental data, and multivariate regression. The validation of these formulas is verified through the hydraulic principles describing intake behaviors and statistical verification tests. Comparison between the calculated data and our measurements shows that the proposed formulas are in good agreement with the experimental results.

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