Analysis of steady river flow through a sluice gate with a case study of Ciliwung River

During wet seasons, tropical rain may cause high discharge on rivers. To prevent flooding in the watershed area, sluice gates can be installed to control the water surface level. However, operating a sluice gate is not a trivial task; we must be aware of the backwater effect. Backwater is an increase of the upstream water level resulting from an obstruction of the flow, here is caused by the installation of a sluice gate. In addition, characteristic of the upstream and downstream flow which depend on flow types (subcritical or supercritical) must also be examined. In this paper, we analyse the behaviour of steady river flow through a sluice gate. On a river flow, the presence of a sluice gate (with a fixed opening), will change the total energy of the flow. Then, using the specific energy curve we can determine water surface level behind the gate. Further, by implementing the standard step method, a steady water surface on the upstream part of the gate can be calculated. This surface forms a backwater flow that extends far enough behind the gate. Characteristic of this backwater flow depends crucially on the flow discharge and the opening of the sluice gate. For the case study, we took the Ciliwung River with the Manggarai sluice gate, located nearly in the middle of the river. With the aim of preventing flooding in the watershed area, we calculated several scenarios of sluice gate opening under various river discharge. Our results may help sluice gate operator in controlling the Manggarai sluice gate of the Ciliwung River.