PENGENDALIAN BANJIR SUNGAI JAJAR KABUPATEN DEMAK Flood Control of Jajar River at Demak Regency

LESTARI, FITRIA MAYA and AFIFAH, RISDIANA CHOLIFATUL (2011) PENGENDALIAN BANJIR SUNGAI JAJAR KABUPATEN DEMAK Flood Control of Jajar River at Demak Regency. Undergraduate thesis, F. TEKNIK UNDIP.

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Abstract

Kejadian banjir dirasakan menjadi sesuatu yang luar biasa apabila kita tidak mampu lagi untuk mengendalikannya seperti fenomena pada Sungai Jajar. Dalam kondisi demikian kita tidak mungkin lagi menghindari timbulnya kerugian sebagai akibat dari bencana yang terjadi, dan yang masih mungkin bisa dilakukan hanyalah mengurangi dampak kerugian yang ditimbulkan. Secara solusi struktural upaya pengaturan dan pengarahan banjir berupa Normalisasi dan pembuatan Floodway guna mengatasi limpasan yang terjadi di beberapa ruas sungai dengan menggunakan periode ulang 50 tahun. Dari perhitungan hidrologi dihasilkan debit sebesar 555.112 m3/dt yang dialirkan melalui ruas Sungai Jajar bagian hilir sepanjang 11.6 km, sedangkan debit sebesar 224.816 m3/dt dialirkan ke Sungai Branjangan sepanjang 12.76 km. Dengan menggunakan program HEC-RAS, dihasilkan Normalisasi Sungai Jajar dengan dimensi penampang ganda yaitu lebar dasar sungai 50 m, kemiringan lereng 1:2, lebar bantaran 10 m. Sedangkan Normalisasi Sungai Branjangan sebagai floodway dengan dimensi penampang tunggal yaitu lebar dasar sungai 30 m, kemiringan lereng 1:2. Untuk menstabilkan pembagian debit pada daerah percabangan, dibuat Bangunan Ambang Pengatur Muka Air Rendah (MAR) dengan dimensi bangunan 2.6 x 3 x 32 m dimaksudkan agar debit normal 11.335 m3/dt mengalir ke Sungai Jajar untuk memenuhi debit minimum Bendung Jajar. Dibuat juga Bangunan Girdel dengan dimensi 23.9 x 3 x 2.6 m, berfungsi untuk menahan erosi agar butiran tanah tidak ikut tergerus aliran air, sehingga pembagian debit tetap konstan. Kata Kunci : Normalisasi Sungai, Floodway, Bangunan Ambang ABSTRACT Flood can be an extraordinary thing if we are no longer able to control, like the phenomenon in Jajar River. In such circumstances it is impossible for us avoid losses as the result of the particular disaster and the reducing impact of it may be the only thing we can still do. The structural solution in the effort of setting up and directing the flood is in the form of several improvement including “Normalisasi” and floodway creating to overcome some overflows in several sections of the river by using a return period of 50 years. With the solution structure of a river improvement and flooodway to overcome the run off that occure several section of rivers. The hydrological calculations has resulted in debit for “Normalisasi” in the downstream segment Jajar River along 11.6 km of 555.112 m3/dt . While the discharge is channeled to the planning of Normalization in Branjangan River along 12.76 km of 224.816 m3/dt. By using HEC-RAS program, Normalization of Jajar River with a double cross-sectional dimensions of the riverbed 50 m wide, 1:2 slope, floodplain width of 10 m is produced. While the normalization of Branjangan River as a Floodway with a single cross-sectional dimension produces 30 m width of riverbed, and slope 1:2. To stabilize the discharge distribution at bifurcation area, the Building Regulatory Threshold “Muka Air Rendah (MAR)” is created the dimensions of the Building is 2.6 x 3 x 32 m so that the normal 11.335 m3/dt discharge flows into the Jajar River to fulfill its minimum discharge of Weir Jajar. The Girdel dam with the dimensions of 23.9 x 3 x 2.6 m, is also created to hold the soil erotion, so that beads of soil won’t be rubbed down by the water flow, and the distribution of discharge remains constant. Keywords: Normalization River, Floodway, Threshold Building

Item Type:Thesis (Undergraduate)
Subjects:T Technology > TA Engineering (General). Civil engineering (General)
Divisions:Faculty of Engineering > Department of Civil Engineering
Faculty of Engineering > Department of Civil Engineering
ID Code:34352
Deposited By:Mr UPT Perpus 2
Deposited On:03 Mar 2012 15:13
Last Modified:03 Mar 2012 15:13

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