Hydraulic model tests and numerical simulations were executed to determine shape of stilling basin type energy dissipator of the A Headworks that local scour occurred at the downstream of apron in. As a result, length of horizontal portion of the pool of the dissipator should equal 25m that is maximum value of length of the entire pool in past cases, and depth of the pool should equal 30% of maximum value of water level difference around gate, in ordet to get the highest performance about dissipating energy on a lean budget for limited time. In addition, it is not easy to control undular jump by changing the length of pool, more effective means is to change the depth of pool, under the conditions of this study.
