ANALISA BANJIR AKIBAT KERUNTUHAN BENDUNGAN BAJULMATI DENGAN PROGRAM HEC-RAS

Sunan Mukti Sriwibowowati, Dian - Sisinggih

Abstract


ABSTRAK: Waduk Bajulmati merupakan waduk yang dibangun untuk memenuhi kebutuhan irigasi sebanyak 1800 ha di daerah irigasi Kabupaten Situbondo dan Banyuwangi. Pada hilir Bendungan Bajulmati perkembangan masyarakat di daerah hilir menjadi daerah pemukiman, pertanian, industri, perdagangan dan banyaknya fasilitas umum, hal ini menyebabkan makin bertambahnya tingkat bahaya akibat keruntuhan bendungan. Tujuan penelitian ini adalah melakukan analisa keruntuhan bendungan dengan menggunakan program HEC-RAS versi 5.0.3 yang dikembangkan oleh Hydrolic Engineering Center. Penelitian ini, melakukan simulasi keruntuhan bendungan akibat overtopping dan piping. Keruntuhan akibat overtopping merupakan penyebab keruntuhan Bendungan Bajulmati yang menimbulkan dampak paling besar dengan banjir desain PMF dengan puncak debit QInflow sebesar 2490.878 m³/det dan menghasilkan luas genangan sebesar 1646.0146  ha dengan tinggi genangan maksimum sebesar 21.31  m. Akibat dari keruntuhan Bendungan Bajulmati ini terdapat 5 desa di 2 kecamatan di bagian hilir Bendungan Bajulmati yang terkena genangan. Terdapat  30024 jiwa penduduk terkena risiko akibat dari keruntuhan Bendungan Bajulmati. Dengan jumlah penduduk terkena risiko tersebut dan jarak Bendungan Bajulmati sampai hilir yang sejauh 9.8 km, maka Bendungan Bajulmati termasuk dalam  klasifikasi bendungan dengan bahaya tingkat 4 yaitu bahaya sangat tinggi. Estimasi total kerugian yang harus ditanggung akibat banjir karena keruntuhan bendungan Bajulmati sebesar Rp 476,691,534,795.

 

Kata Kunci: Keruntuhan Bendungan, Bendungan Bajulmati, Overtopping, Piping, HEC-RAS

 

ABSTRACT:. Bajulmati Reservoir is a reservoir built to meet the irrigation needs of 1800 ha in the irrigation area of ​​Situbondo and Banyuwangi Districts. At the downstream of the Bajulmati Dam the development of communities in the downstream area becomes residential, agricultural, industrial, trade and many public facilities, this causes an increase in the level of danger due to the collapse of the dam. The purpose of this study was to analyze the dam collapse using the HEC-RAS version 5.0.3 program developed by the Hydrolic Engineering Center. This research, carried out a simulation of dam collapse due to overtopping and piping. Collapse due to overtopping is the cause of the collapse of the Bajulmati Dam which has the greatest impact with the flood of PMF design with a peak flow of QInflow of 2490,878 m det / sec and produces a pool area of ​​1646.0146 ha with a maximum inundation of 21.31 m. As a result of the collapse of the Bajulmati Dam there were 5 villages in 2 sub-districts in the lower reaches of the Bajulmati Dam which were inundated. There were 30024 residents affected by the risk of the collapse of the Bajulmati Dam. With the population affected by this risk and the distance of the Bajulmati Dam to the downstream which is as far as 9.8 km, the Bajulmati Dam is included in the classification of dams with level 4 hazards, namely very high hazards. The estimated total loss to be borne due to flooding due to the collapse of the Bajulmati dam was Rp. 476,691,534,795.

Keywords: Dam Break, Bajulmati Dam, Overtopping, Piping, HEC-RAS


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