Study of the Effectiveness of Making a Retention Pond for Urban Flood Management: A Case Study of the Barabai River, South Kalimantan

Abstract

The upstream of the Barabai River is experiencing land conversion from forest to agricultural and mining areas. In 2021, f loods and river overflows will inundate nearly 75% of Barabasi City. The solution given is to build a Retention Pool so that the flow of the Barabai River before entering Barabai City is diverted to the Retention Pool. By conducting hydrological and hydraulic flow analysis with the application of HEC RAS with unsteady flow conditions, the water level profile along the Barabai River can be displayed including the flow behavior in the retention pond during flooding. As a result, the retention pond is only effective at accommodating 25% of the discharge during a flood. By optimizing using the HEC RAS program, alternatives to inundation or flooding in Barabai City are obtained, namely: widening the Barabai river 2x, expanding the regulation pool to 95 ha, building a second retention pond of 40 ha, and normalizing the Barabai River that enters Barabai City.