Efektivitas Dam pengendali sedimen tipe terbuka dan tertutup :: Uji model fisik

WIRATNA, Sugeng, Dr.Ir. Istiarto, M.Eng

2006 | Tesis | S2 Teknik Sipil (Mag. Pengelolaan Bencana Alam)

Bencana alam akibat aliran sedimen sering terjadi pada daerah gunung api maupun pada daerah pegunungan. Bencana aliran sedimen mempunyai daya rusak yang besar dan merupakan bencana alam yang sangat berbahaya bagi jiwa manusia dan fasilitas infrastuktur di sepanjang sungai dan wilayah sekitarnya. Salah satu cara penanganan daya rusak akibat aliran sedimen adalah dengan dam pengendali sedimen. Untuk mengetahui efektifitas dam pengendali sedimen dalam mengendalikan aliran sedimen/debris, dilakukan penelitian dengan uji model fisik pada skala 1 : 25. Penelitian ini dilaksanakan dengan mengambil prototipe dam pengendali sedimen BO-D5 sebagai model fisik dengan melakukan beberapa modifikasi. Debit puncak dimodifikasi dari Q2 = 188 m3/detik selama 70 menit menjadi Q2 = 59,84 liter/detik selama 14 menit dan lebar slit dari 3 m menjadi 8,4 cm. Simulasi aliran sedimen/debris menggunakan hidrograf banjir dengan kala ulang 50 tahun pada stasiun AWLR Pulowatu, yaitu pada debit Q1 = 11,2 liter/det selama 10 menit; debit Q2 = 59,84 liter/det selama 14 menit; debit Q3 = 36 liter/det selama 20 menit dan debit Q4 = 16 liter/det selama 16 menit. Simulasi dilakukan terhadap dam pengendali sedimen tipe terbuka dan tipe tertutup. Hasil penelitian diperoleh volume sedimen kontrol (Vc) dam pengendali sedimen tipe terbuka setelah pengaliran debit Q1 = 0,137 m3, Q2 = 2,749 m3, Q3 dan Q4 = 1,748 m3. Kapasitas dam pengendali sedimen tipe tertutup volume sedimen kontrol (Vc) setelah pengaliran debit Q1 = 0,081 m3, Q2 = 1,989 m3, Q3 dan Q4 = 1,761 m3. Volume kontrol dam pengendali sedimen tipe terbuka lebih efektif dibandingkan dengan tipe tertutup.

Natural disaster due to sediment/debris flow often occurs in volcanic area or mountainous area. Sediment/debris flow has a big destruction so it is very dangerous to human lives and infrastructures along the river and it surroundings. One of the countermeasures against sediment/debris flow is by constructing checkdam/sediment control dam. In order to know the effectiveness of the dam to control sediment/debris flow, a physical model test at 1:25 scale was conducted. Existing checkdam K Boyong No 5 (BOD5) is taken as a model with several modification. Peak discharge was modified from Q2 = 188 m3/sec during 70 minutes to Q2 = 59.84 liter/sec during 14 minutes and the width of slits from 3 m to 8.4 cm. Simulation of sediment or debris flow in the model applies simplified flood hydrograph of 50 years return period at AWLR Pulowatu those are Q1 = 11.2 liter/sec during 10 minutes, Q2 = 59.84 liter/sec during 14 minutes, Q3 = 36 liter/sec during 20 minutes, and Q4 = 16 liter/sec during 16 minutes. Implementation of running test of the model use both open and close tipe of checkdam. Results of the expriment reveal that controlled sediment volume (Vc) for open type sediment control dam after flowing of discharge Q1 is 0,137 m3, Q2 is 2,749 m3, and after Q3 and Q4 are 1,748 m3. The controlled sediment volume (Vc) for close type sediment control dam after flowing of discharge Q1 is 0,081 m3, Q2 is 1,989 m3, and after Q3 and Q4 are 1,761 m3. Based on the controlled sediment volume, open type sediment control dam is more effective than close type sediment control dam.

Kata Kunci : dam pengendali sedimen, aliran sedimen, efektivitas, uji model fisik, sediment control dam, debris flow, effectiveness, physical model test