This paper investigates how the variation of gap height of radial gate in scaled down dam would affect the volumetric flow rate. Both fluid/structure interaction (FSI) numerical simulation and experimental works on a scaled-down dam model were conducted, eventually both approaches yield results with discrepancy not exceeding 9.63%. For 10 mm and 12 mm gap, lowest water flow rate is being observed in the Gate 2 compared to Gate 1 and Gate 3. Conversely, the Gate 2 registered highest water flow rate for gate with gap of 8 mm. Generally, it is found that the volumetric flow rate increases along with the increase with the gap height of radial gate. Moreover, the volumetric water flow rate in actual dam also be determined using Reynolds number.