In terms of the importance of hydraulic structures, this study was initiated with the objective of investigating the effect of side seepage on the hydraulic characteristics of the hydraulic structures. A physical sand model of dimensions 2000 x 300x 850 mm was constructed and an experimental program, that included 75 tests, was designed. The tests were divided into 3 sets in order to simulate different combinations for side seepage. The first set was intended to investigate the case of not allowing side seepage to occur �i.e. a reference case for comparison purposes�. The other two sets were intended to investigate the side seepage �with width equal to half, and same length of hydraulic structure floor width�. For each set, the effect of position and depth of the driven sheet pile, under the structure foundation, was studied under different effective water heads. Runs were carried out and measurements were undertaken �i.e. uplift pressure and seepage discharge�. Measurements were analyzed and represented. The results showed that allowing side seepage might cause an increase in the uplift force by 47% �i.e. more than the case of not allowing side seepage�. Allowing side seepage might cause an increase in the seepage discharge by 229%.