Seite - 689 - in Book of Full Papers - Symposium Hydro Engineering

aim of this study is to have a proper design of stepped spillway which can be a good reference for further implementation of a stepped spillway. The experiments were conducted inside a hydraulic laboratory and the model covering the upstream reservoir, approach channel upstream apron of the spillway, dam, spillway and appurtenance structures (See Figure 1). Fig. 1. Plan view of Upper Cisokan Dam 2. EXPERIMENTAL SETUP The Upper Cisokan Dam spillway model is made as three-dimensional model covering the upstream reservoir, spillway and appurtenance structures (crest, chute channel and energy dissipator), and river in the downstream of the spillway. The experiment conducted at a hydraulic laboratory to observe the water profile, water pressure and scouring. The reservoir model in the upstream reach is made as a fixed bed model; it is constructed using of cement mortar and reproduced based on situation drawings. The reproduce upstream model is up to approximately 300 m upstream of the spillway. In particular for water pressure test, pressure transducers were installed inside the model to indicate the pressure measurement. In this experiment, there will be three scenarios; scenario 1 is the initial design where the downstream riverbed model is reproduced as a movable bed made by sand and left unprotected. Scenario 2 is a condition where the downstream protection material using stone riprap for downstream riverbed protection and arrange with u-shape. Scenario 3 is the condition where the downstream protection material is fully using stone riprap. The length of reach modelled is approximately 440 m downstream of the energy dissipator. The 689