Study of design discharge and river capacity in Celeng Sub-watershed, Special Region of Yogyakarta

Celeng sub-watershed is a catchment area located in the Oyo watershed. This catchment has circular shape which is situated in the alluvial plain. In the 2018, there was a huge flood occurred in the area that was triggered by Savana Cyclone. The cyclone itself contributed in extreme precipitation, resulted in high discharge in a very short time, and spilled over the riverbank. The research aims (1) to analyze the discharge capacity in the Celeng sub-watershed, (2) to determine the design discharge of Celeng sub-watershed for 2, 5, 10, and 25 years return period, and (3) to evaluate whether the design discharge excess the Celeng river capacity or not. The research uses quantitative analysis through rational method and slope area method. The design discharge measured by rational method and applied to evaluate the river capacity along with rational method. The result shows that the area does not experience flood in all return period.