Flow through Gabion Stepped Spillways

Abstract

This paper presents the results of the experimental studies on the flow through the gabion steppedspillways. The width of the gabion stepped spillways is 0.40 m and the slopes of the gabion stepped spillways are30 Ì, 45 Ì, and 60 Ì with total spillway drop height 1.50, 2.12, and 2.60 m, respectively. The step height is 5 percentof the total spillway drop height. The discharge through the gabion stepped spillways was varied from 4 to 68 l/s. Itwas found that nappe flow occurred at low flow rates, transition flow at intermediate discharges and skimmingflow at larger flow rates. The regimes of flow could be identified by the ratio of critical flow depth and stepheight. The energy loss varied inversely with the modified drop number, i.e. energy loss increased when modifieddrop number decreased. As the energy loss of flow increased, the velocity of flow at the spillway outlet decreased.The energy of flow was dissipated more in the gabion stepped spillways than in the horizontal stepped spillwaysabout 10 percent. The velocity of flow at the outlet of the gabion stepped spillways was less than that of thehorizontal stepped spillways by about 14 percent.

Keywords : Stepped spillways / Gabions / Energy loss / Outlet velocity