Hydraulic analysis and ecological and physical study of hydraulic Alas-Singkil river Southeast Aceh, Indonesia

Abstract

The problem of flooding that occurs around the Lawe Alas-Singkil, Aceh Province is the conservation function of the area from upstream to downstream needs serious attention. The area around the watershed is degraded due to several factors. This factor is closely related to illegal logging, exploitation of nature with mineral mining to the conversion of area functions. This study aims to identify the existing conditions of the riverbanks, how the relationship between community social activities and the banks of the Alas-Singkil River, and to study the physical conditions of the river from upstream to downstream. The study method in this research includes a literature study, hydrological conditions of the Alas-Singkil Watershed, field surveys, identification of existing conditions, and study of the ecology and physicality of the river. Survey the condition of flora and fauna in the study area and the economic and social activities of the community. The results of the study on the hydrological conditions of the Alas-Singkil watershed with an area of 10,090.13 km2 and a river length of 316.26 km, in the upstream form of mountains and natural forests where deforestation has occurred due to forest conversion to cocoa plantations, planting of corn on the hills and so on, The maximum annual daily rainfall is high (151-300 mm), so the potential for flood disaster is even greater. In the rainy season, large amounts of water cause mountains or hills in Southeast Aceh to melt and become a flash flood disaster. Many of the rivers in the middle and downstream have turned into plantations and rice fields and some are still swamps. The condition of the river in the Alas-Singkil watershed generally occurs silting or sedimentation in the river body, the existing condition of the Alas-Singkil riverbank, where there are still many settlements on the riverbanks. The downstream Krueng Singkil is experiencing more frequent flooding, either due to the overflow of Krueng Singkil in the upstream part and the blocked river flow and rising tides. The frequency of inundation and flood disasters in Singkil City reaches 3 to 4 times each year with an inundation height of 0.5-3.0 meters. It is necessary to repair the riverbanks by using vegetation components found on the banks of the Alas-Singkil River and overcoming floods in the upstream and downstream rivers to protect the ecosystem and people living on the riverbanks. The solution that can be done is to restore the conservation function of the area around the Lawe Alas watershed. and built channel diversion flood from the Lae Soraya river in the village of Gelombang directly to the sea.