Flood Discharge Analysis with Nakayasu Method Using Combination of HEC-RAS Method on Deli River in Medan City

The problem in this research is how in the rainy season the water does not overflow, does not occur flood and during the dry season does not occur drought so it can adjust the condition or existence of Deli river which is around Medan city. Deli River floods often occur, either caused by a smaller capacity than the existing discharge, lack of maintenance and drainage and disposal systems that do not fit with the environment, resulting in flood subscriptions every year. The purpose of this research is to know flood discharge at Deli river as Flood control in Medan city. This research is analyzed on several methods such as log Pearson, Gumbel and hydrograph unit, while HEC-RAS method is modeling conducted in analyzing the water profile of the Deli River. Furthermore, the calculation of the periodic flood discharge using the Nakayasu Method. Calculation result at Deli River return period flood discharge 2 years with an area of 14.8 km 2 annual flood hydrograph the total is 26.79 m 3 /sec on the hours at the 4th time. Return period flood discharge 5 years with an area of 14.8 km 2 annual flood hydrograph the total is 73,44 m 3 /sec. While 25 annual return period total flood hydrograph is 146.50 m 3 /sec. With flood analysis can reduce and minimize the risk of losses and land can be mapped if in the area there is flooding.