STUDI KELAYAKAN BANGUNAN PENANGGULANGAN BANJIR DI SUNGAI MUJUR DESA TEMPEH TENGAH KECAMATAN TEMPEH KABUPATEN LUMAJANG

Abstract

Gunung Semeru merupakan salah satu gunung api paling aktif di Indonesia yang terletak di antara wilayah administrasi Kabupaten Malang dan Lumajang. Produk letusan utama dari Gunung Semeru adalah lontaran material pijar, guguran awan panas dan lahar di musim hujan masuk ke sungai-sungai yang berhulu di Gunung Semeru diantaranya adalah Sungai Mujur. Daerah Aliran Sungai Mujur memliki luas DAS 208,31 km². Kondisi dinding penahan (revetment) di Sungai Mujur Desa Tempeh Tengah, Kecamatan Tempeh Kabupaten Lumajang kapasitas dan kualitasnya sudah banyak berkurang seperti di hulu Dam Soponyono tanggul sisi kiri jebol. Upaya penangggulangan banjir direncanakan dengan menggunakan dinding penahan/revetment. Analisa profil aliran dilakukan dengan menggunakan software HEC-RAS 4.1.0, sedangkan untuk analisa stabilitas lereng revetment menggunakan Metode Fellenius. Perencanaan pengendali banjir Sungai Mujur menggunakan debit banjir rancangan Q25 th yaitu sebesar 192,98 m³/dt. Pada kondisi eksisting ditemukan 3 patok cross section yang meluber. Hasil analisa perencanaan bangunan revetment didapat II alternatif perencanaan. Alternatif I dengan tinggi revetment 3,7 m di hulu Dam Soponyono dan 4,6 m di hilir Dam Soponyono dengan kondisi penampang sungai asli. Untuk Alternatif II dengan tinggi revetment 3,2 m di hulu Dam Soponyono dan 4,6 m di hilir Dam Soponyono dengan dilakukan normalisasi pada penampang sungai.

Kata kunci: Banjir, HEC-RAS, stabilitas, dinding penahan, revetment

Mount Semeru is one of the most active volcanoes in Indonesia, located between the administrative areas of Malang and Lumajang Regencies. The main eruption product from Mount Semeru is a burst of incandescent material, hot clouds and lava in the rainy season into the rivers that headed at Mount Semeru include the Mujur River. Mujur watershed has an area of  208.31 km². The condition of retaining  wall in Mujur River of Tempeh Tengah Village, Tempeh Sub-district of Lumajang Regency, its capacity and its quality have decreased as much as in the upstream Dam Damonyono dam. Efforts to control floods are planned using retaining walls. Flow profile analysis was performed using HEC-RAS 4.1.0 software, while for stability analysis of revetment slope using Fellenius Method. Planning for flood control of the Mujur River uses a flood discharge of Q25th design which is 192.98 m³/sec. In the existing conditions found 3 cross section stakes that overflow. The results of the analysis of the planning of the revetment building obtained II alternative planning. Alternative I with a 3.7 m high revetment upstream of Soponyono Dam and 4.6 m downstream of Soponyono Dam with the original river cross section. For Alternative II with high revetment 3.2 m upstream of Soponyono Dam and 4.6 m at downstream of Soponyono Dam by normalization at river cross section.

 

Key words: Flood, HEC-RAS, stability, retaining wall, revetment