Studi Perencanaan Rehabilitasi Bangunan Pelimpah (Spillway) pada Embung Takisung Kabupaten Tanah Laut Kalimantan Selatan

Abstract

Perencanaan rehabilitasi bangunan pelimpah(spillway) bertujuan untuk mengetahui besar debit banjir, merencanakan desain dimensi bangunan, dan menganalisis kestabilan bangunan. Perencanaan ini dilakukan di Embung Takisung Kabupaten Tanah Laut Kalimantan Selatan. Tahap awal perencanaan ini adalah dengan meninjau secara detail debit inflow yang masuk ke waduk yang selanjutnya digunakan untuk perhitungan penelusuran banjir. Hasil dari penelusuran banjir berupa debit outflow yang akan digunakan sebagai dasar perencanaan pelimpah, profil muka air, serta perencanaan peredam energi. Hasil perencanaan yaitu besar debit menggunakan metode HSS Nakayasu sebagai debit inflow dengan kala ulang 100 tahun dan kala ulang 1000 tahun sebagai kontrolnya. Debit inflow sebesar Q100th = 61,729 m3/detik; Q1000th = 72,541 m3/detik serta debit outflow sebesar Q100th = 30,453 m3/detik; Q1000th = 37,767 m3/detik. Kemudian hasil perencanaan pelimpah yang sesuai dengan kondisi daerah studi dari topografi, hidrologi dan hidrolikamenggunakan Q100th. Perhitungan stabilitas pelimpah dengan keadaan air kosong, muka air normal dalam kondisi normal dan gempa, dan muka air banjir debit Q1000th serta keadaan ekstrim diperoleh hasil aman terhadap guling, geser dan daya dukung tanahnya tidak melebihi dari tegangan ijin tanah sehingga memenuhi syarat. Spillway rehabilitation planning aims to determine the discharge of major floods, dimensional design of the structure, and analyze the stability. This planning was carried out at the Takisung Retarding basin, Tanah Laut Regency, South Kalimantan. The initial stage of this planning is to review in detail the incoming discharge that enters the reservoir which is then used for flood routing on the spillway. The result of flood routing is in the form of outflow which will be used as the basis for planning the spillway, the water level profil, and the planning of the stilling basin. The result of the planning is a large discharge using the HSS Nakayasu method as an inflow discharge with a return period of 100 years and a return period of 1000 years as the control. Inflow discharge of Q100th = 61,729 m3/second; Q1000th = 72,541 m3/second and an outflow discharge of Q100th = 30,453 m3/second; Q1000th = 37.767 m3/second. Then the spillway planning results are in accordance with the conditions of the study area from topography, hydrology and hydraulics using Q100th. Analyze of the stability with the load with empty water, normal water level in normal and earthquake conditions, and flood water level with Q1000th discharge and extreme conditions which results in safety against overturning, shearing and soil carrying capacity not exceeding the allowable stress of the soil so that it meets the requirements.