Integration of the Barabai Watershed Flood Channel with the Eco-Drainage System Concept of a Regulation/Retention Pond

Abstract

Flood is a common problem for Indonesian people, especially during the rainy season. The water flow in the watershed experiences a natural hydrological cycle. The Barabai watershed is a tributary of the Negara River, in the Barito River Basin, South Kalimantan, Indonesia. Almost every year the river overflows, causing inundation and reach the city of Barabai. The flooding that occurred caused damage to river borders and inundated the city, causing the community's life activities to be disrupted. To reduce the flood discharge of the Barabai watershed that entered Barabai City, the Government built an Intake and Flood Channel to divide the flood discharge of the Barabai River (Q₅ years) of 79.79 m³/s into two parts, namely one that passes through the Barabai Flood Channel of 40 m³/sec and the other 39.79 m³/sec continues to flow downstream of the Barabai River. The new intake is built with an intake elevation that is lower than the previous intake building, with the aim that Q2 flood discharge can enter the Flood Channel. However, this intake and flood channel was only able to cope with flooding up to Q₅ with a 62.75% reduction in flood inundation. The concept of integration of the existing flood channel (horizontal flood control system) with a vertical flood control system (regulation/retention pool) is expected to optimize the flood control system that has been built to reduce the peak time of flooding entering the city of Barabai by temporarily holding water in the regulation/retention pool.