Analisis Efektivitas Kolam Retensi USU dalam Mereduksi Banjir di Kampus Universitas Sumatera Utara Berbasis HEC-RAS

Abstract

Flood disasters that often occur in the University of North Sumatra Campus area have caused losses for students and the surrounding community. As an effort to reduce flooding in the area, the Medan City Government built the USU Retention Pond. In its implementation, a study is needed on the effectiveness of retention ponds built in flood-affected areas of the University of North Sumatra campus area, especially around Jalan Dr. Mansyur. In this study, a hydrological analysis was carried out with a 10-year re-flooding of the Gumbel method with a planned rainfall of 160.60 mm, which was then simulated using HEC-RAS 6.5 software. The Retention Pond has been built with 2 Ponds with a maximum storage volume of 3762.5 m3 and 6300 m3 respectively, with a Pool depth of 3.5 meters and there are 1 inlet door and 1 outlet door each in both ponds. From the results of the Unsteady Flow Analysis simulation with a 6-hour rain hyetograph, a discharge of 4,034 m3/second was obtained on Jalan Dr Mansyur along Gate I USU towards the Outlet channel and a discharge of 2,887 m3/second from the direction of Door IV USU to the Outlet channel, the result was obtained that the two Retention Ponds would be full at the 3rd hour after 40 minutes. In the simulation before and after the existence of the Retention Pond, the Retention Pond reduced the flood height by 0.3 meters on Jalan Dr Mansyur 1 and 0.6 meters on Jalan Dr Mansyur 2. But even with the existence of the Retention Pond, there will still be flood inundation with a height varying from 0.10 – 0.30 meters from the drainage surface. With these results, the effectiveness of the Retention Pool was 71%.