A conventional weir typically consists of an impermeable body constructed of concrete, since its primary functions are to
heading up water and efficiently regulate flow. However, an impermeable body prevents the longitudinal movement of aquatic life and
transportation of physical and chemical substances in water, eventually having a negative impact on the water environment. One of the
advantages of gabions as a building material is that the motion of individual stones comprising the gabion is not of much concern. The
wire mesh of the gabion basket serves to restrain any significant movement. Also, gabion weirs offer an alternative design that could be
adopted for flash flood mitigation. In this study, a series of laboratory experiments was performed in order to investigate the flow over
gabion weirs. For this purpose, two different gabion weir models were tested in two horizontal laboratory flumes of 10-m and 17-m length,
0.3-m width, and 0.3- and 0.5-m depth, respectively, for a wide range of discharge, upstream water depth, downstream water depth, weir
height, weir length, and gabion filling gravel material size. The results of the gabion weir were compared with those of experiments
carried out on solid weirs having the same dimension and it was found that there is a large deviation when the solid weirs equation is
applied to gabion weirs
permeable weirs. So, using one of the existing solid weir flow formulas would lead to an erroneous calculated
value. Multiple regression equations based on the dimensional analysis theory were developed for computing the discharge over gabion
weirs for both free and submerged flow regimes. Also, equations were introduced for computing the discharge coefficient to be applied
with the traditional solid weir equation.