EVALUASI PENANGGULANGAN BANJIR DI KECAMATAN BANGIL AKIBAT LUAPAN SUNGAI KEDUNGLARANGAN

Abdillah, Ahmad Wisam (2021) EVALUASI PENANGGULANGAN BANJIR DI KECAMATAN BANGIL AKIBAT LUAPAN SUNGAI KEDUNGLARANGAN. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Banjir merupakan salah satu permasalahan yang sering terjadi pada musim penghujan. Kecamatan Bangil, Pasuruan, juga tidak terlepas dari masalah banjir. Banjir berasal dari luapan Sungai Kedunglarangan. Pada awal tahun 2020 beberapa desa di Kecamatan Bangil terendam banjir. Sedikitnya terdapat 3 desa, yaitu Desa Kalirejo, Desa Manaruwi, dan Desa Masangan yang terendam banjir dengan ketinggian genangan berkisar antara 30 hingga 50 cm. Banjir yang setiap tahun terjadi ini sangat mengganggu aktivitas masyarakat terdampak karena kegiatan-kegiatan masyarakat seperti bekerja dan anak-anak sekolah terbatasi. Banjir juga menggenangi area persawahan yang siap panen sehingga merugikan para petani.
Metode penanggulangan banjir yang sering digunakan antara lain normalisasi sungai, perencanaan tanggul, perencanaan boezem, dan perencanaan sudetan. Berdasarkan pengamatan dilapangan, di area sekitar penggal Sungai sebagai objek studi merupakan area rawa, tambak, dan sawah. Oleh karena itu, metode yang dapat diterapkan adalah normalisasi dan perencanaan tanggul sungai. Kapasitas alir penampang melintang sungai dianalisa dengan dua cara, yaitu secara manual dan dengan bantuan program HEC-RAS. Adapun untuk menganalisa stabilitas lereng sungai menggunakan aplikasi Geo5 untuk menentukan apakah lereng sungai aman dari kelongsoran atau tidak.
Dari hasil perhitungan debit banjir maksimum rencana dengan periode ulang 25 tahun diperoleh debit banjir sebesar 246,929 m3/detik. Penampang melintang sungai direncanakan didesain menggunakan double trapesium serta penambahan perencanaan tanggul di atas tanah dasar khusus untuk STA 0+000 hingga STA 0+450, sedangkan STA 0+500 hingga akhir tidak direncanakan tanggul. Dimensi penampang melintang sungai setelah normalisasi yaitu lebar sungai 85 m (dengan tanggul), 76 m (non tanggul), lebar dasar sungai 12 m, lebar terasering 11 m, kedalaman muka air sungai diukur dari dasar sungai sebesar 6,289 m, kemiringan lereng 1:1,5 untuk lereng trapesium atas dan bawah. Dimensi tanggul memiliki lebar atas 1,00 m, lebar dasar tanggul 4,5 m, dan ketinggian tanggul 1,50 m. Pada permukaan lereng sungai memiliki stabilitas tanah yang baik. Namun ketika analisa Geo5 menggunakan garis kelongsoran yang lebih besar, analisa Geo5 menunjukkan adanya ketidak stabilan pada tanah lereng sungai yang berpotensi terjadi kelongsoran. Untuk mengantisipasi kelongsoran tersebut ada beberapa alternative yaitu dengan perencanaan geotextile wovwn, pemasangan batu bronjong, perencanaan angkur, atau bisa mengombinasikan ketiga alternative tersebut.
Penanggulangan banjir ini diharapkan dapat memberikan rasa aman dan nyaman kepada masyarakat, terlebih lagi mampu menyelamatkan mata pencaharian masyarakat sekitar yang sebelumnya terdampak banjir tahunan karena meluapnya Sungai Kedunglarangan.
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Floods are one of the problems that often occur during the rainy season. Bangil Sub-District, Pasuruan, is also inseparable from the problem of flooding. The flood comes from the overflow of the Kedunglarangan River. In early 2020 several villages in Bangil District were flooded. There are at least 3 villages, namely Kalirejo Village, Manaruwi Village, and Masangan Village which were flooded with puddle heights ranging from 30 to 50 cm. Floods that occur every year are very disturbing community activities because community activities such as work and school children are limited. Floods also inundate rice fields that are ready to harvest and causing losses to farmers.
Flood control methods are often used include river normalization, embankment planning, boezem planning, and drainage planning. Based on field observations, the area around the cut of river as the object of study is an area of swamps, ponds, and rice fields. Therefore, the method can be applied is normalization and planning of river embankments. Cross section capacity analysis use 2 (two) method, there are manual method and with HEC-RAS Program. River slpoe identified by Geo5 to analysis about stability of land in order to anticipate landslide.
The result of this study is that the maximum flood discharge for the 25 year return period of the Kedunglarangan River is 264,929 m3/second. It is planned that the cross section of the river is in the form of a double trapezoid and an embankment is built on the subgrade (just for STA 0+000 until STA 0+450, STA 0+500 untill ending of cutting Kedunglarangan river not planned with embankment). The dimensions of the cross section are the width of the river 85 m (crossection with embankment, 75 m for crossection not planned embankment), the width of the river bed 12 m, the width of the terraces 11 m, the river depth is measured from the top of the embankment as deep as 6,289 m, the slope of the upper and lower trapezoidal river is 1:1.5. The dimensions of the embankment are the top width of 1,00 m, the bottom width of 4,50 m and the height of the embankment 1,50 m. The surface of river slopes and embankments have good soil stability. However, when analyzing a large landslide line, the landslide can occur. Therefore, to anticipate the occurrence of landslides, the alternatives that can be used are planning woven geotextiles, installing gabion stones, planning anchors, or a combination of the three alternatives above.
Flood control is expected to provide a sense of security and comfort to the community. Moreover, with this flood control, it is hoped that it will be able to save the livelihoods of the surrounding community who were previously affected by the annual floods due to the overflow of the Kedunglarangan River.

Item Type:	Thesis (Undergraduate)
Uncontrolled Keywords:	Tanggul, Banjir, Geo5, HEC-RAS, Sungai Kedunglarangan, Normalisasi, Rating Curve, Hidrograf Satuan Sintetis (HSS). ================================================================================================================== Embankment, Flood, Geo5, HEC-RAS, Kedunglarangan River, Normalization, Rating Curve, Synthetic Unit Hydrograph (HSS).
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC530 Flood control
Divisions:	Faculty of Civil Engineering and Planning > Civil Engineering > 22201-(S1) Undergraduate Thesis
Depositing User:	Ahmad Wisam Abdillah
Date Deposited:	31 Jul 2021 16:19
Last Modified:	31 Jul 2021 16:23
URI:	http://repository.its.ac.id/id/eprint/84651

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