Deli River Flood Controlin the Maimun District Area Medan City

Abstract

Flooding is a common issue in urban areas, caused by high rainfall intensity that increases river discharge and leads to overflow, as the river channel capacity cannot accommodate such large water volumes. In the city of Medan, one of the rivers that passes through the areais the Deli River, which stretches for72 km and has a watershed area of 472.96 km², starting from Karo Regency to Medan City.One of the most urgen turban problems that needs to be addressed is flooding.Sei Mati Subdistrict, located in the Medan Maimun District, is one of the areas in Medan considered prone to flooding, especially in residential zone salong the banks of the Deli River. This research employs aquantitative-based approach. It utilizes both primary and secondary data, suchas maximum rainfall data, crossand long sections of the Deli River, land use data, and the locations affected by floods. These data are then analyzed hydrologically to obta in the design flood discharge.There sults of the hydrologi calanalysis are then further analyzed hydraulically using the HEC-RAS 5.0.7 software. From the hydrological analysis, the planned flood discharge was obtained using the Nakayasu Synthetic Unit Hydrograph (SUH) method, resulting in values of: Q2=358.300m³/s, Q5=434.478m³/s, Q10=491.722m³/s, Q25=571.716m³/s, and Q50=571.716m³/s. From the hydraulic analysis using HEC-RAS 5.0.7, it was shown that thereisan approximate increase in flood height of ±25cmforthe 2-year return period compared to the 2023 flood event, with a total water surface elevation of 3.92 m for the 2-year returnperiod. Therefore,the construction of a5-meter-high levee on the right river bank is necessary.This height has accounted for the minimum peak discharge value in the2ndyear,which is434.378 m³/s.This solution is considered optimal for minimizing flood risk during the 2-year return period along the Deli River.