DESIGN OF STILLING BASIN FOR DECREASING BACK WATER IN THE DAM FOOT

This research studies the hydraulic behavior and the problem solving alternatives of original until final design, and the most effective stilling basin and downstream regulator channel for decreasing back water from the upstream water level in the dam foot. The methodology consists of physical modeling in the Laboratory of River and Swamp, Department of Water Resources, Faculty of Engineering, University of Brawijaya. The methods include the USBR for the hydraulic analysis, the Hind’s formulation for the side channel analysis, the energy equation by analyzing the standard step for the transition and the chute way analysis, and the USBR type III for designing the stilling basin. A square cross-section with the Manning coefficient of 0.40 is used for determining the control of the Tail Water Level (TWL) and a trapezoidal crosssection with the Manning coefficient of 0.39 is used for the final design. However, the equation of Schotlisch and Veronise is used for the local scouring analysis. The result of Model Test and analysis indicates that there are some differences among the analysis in every point of the building. Therefore, the relative error is needed to know how big the error in the comparison result.