ANALISIS AGRADASI, DEGRADASI DAN SEDIMENTASI DI SUNGAI PABELAN PASCA ERUPSI GUNUNG MERAPI 2010

Abstract

Mount Merapi is the most active volcano in Indonesia, the eruption that occurred in 2010 was a major eruption with a return period of 100 years. Of the 140 million m3 potential of Mount Merapi's cold lava, 24 million m3 of which flows into the Pabelan River. One of the disaster mitigation on the Pabelan River is the Sabo Dam infrastructure, currently there are 23 Sabo Dams on the Pabelan River, in 2022 1 additional Sabo Dam has been built, namely PAC-Menayu. In this study, modeling will be carried out using 1D Kanako before the construction of 1 Sabo Dam and after the construction of 1 Sabo Dam with river geometry measured in 2020 and flood discharge generated from rainfall triggering debris flow on February 3 2011 at the Jrakah Rain Post, from rainfall This rainfall distribution is carried out for 6 hours using the PSA coefficient to be input in the HEC-HMS. From the results of Kanako modeling, it was concluded that the construction of the new Sabo Dam was able to reduce sedimentation by 52.88 m3 and it was found that the construction of 24 Sabo Dams effectively retained 32.6% of sediment from the total potential of cold lava of 24,000,000 m3 flowing in the Pabelan River so that it is appropriate as a disaster mitigation effort that can reduce the potential future debris flooding.