Perencanaan Pengendalian Banjir Kali Sadar Bagian Hilir Di Mojokerto

Purbalaras, Ardhika Pasaratri (2021) Perencanaan Pengendalian Banjir Kali Sadar Bagian Hilir Di Mojokerto. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kali Sadar adalah salah satu sungai yang lokasinya berada di Mojokerto, Jawa Timur. Kali Sadar memiliki panjang 27.750 meter, dengan luas DAS 88,749 〖km〗^2, dan elevasi hulu +900 meter, serta elevasi hilir +20 meter dari permukaan laut. Ketika memasuki musim hujan, bagian hilir Kali Sadar mengalami banjir. Daerah hilir Kali Sadar berada di Kota Mojokerto, hal ini menyebabkan dampak yang cukup merugikan warga setiap musim hujan.. Bagian kali yang di tinjau adalah sepanjang 4.900 m. Terdapat 2 kemungkinan faktor terjadinya banjir. Pertama, pada bagian hulu sungai, memiliki kontur yang cukup curam, namun pada bagian hilir memiliki kontur yang terbilang cukup landai. Kondisi tersebut menyebabkan proses pengaliran debit banjir membutuhkan waktu yang lama. Kedua, kapasitas penampang Kali Sadar tidak dapat menerima debit limpasan. Maka, dapat direncanakan pompa air, pintu air, kolam tampung dan normalilasi Kali Sadar untuk menanggulangi salah satu faktor penyebab banjir. Dalam mengatasi banjir tersebut membutuhkan data pengukuran eksisting penampang sungai, data hujan, peta topografi dan data tata guna lahan. Data pengukuran eksisting penampang sungai berguna untuk menghitung kapasitas sungai eksisting (Q sungai eksisting), sedangkan data hujan digunakan untuk curah hujan rata-rata maksimum. Peta topografi digunakan untuk mengetahui luas DAS. Data tata guna lahan digunakan untuk menggambarkan pemanfaat daerah tersebut. Berdasarkan data hujan, peta topografi dan data tata guna lahan maka didapatkan debit banjir rencana (Q banjir rencana). Jika Q sungai eksisiting < Q banjir rencana, maka perlu dilakukan normalisasi, perencanaan kolam tampung, perencanaan pintu air, dan pompa air. Dalam menanggulangi over topping dilakukan normalisasi dengan cara membuat tanggul setinggi 0,5 – 1 meter pada penampang yang mengalami over topping dengan kemiringan tanggul 1:1 dan lebar mercu 1 meter. Penampang yang mengalami peninggian tanggul terjadi pada Sta 500-3600. Tetapi, metode normalisasi ini tidak dapat maksimal dalam menampung debit rencana yang disebabkan kondisi eksisting tidak bisa dilakukan normalisasi. Oleh karena itu, metode yang digunakan adalah pembuatan kolam tampung. Kolam tampung berlokasi pada hilir Kali Sadar dengan luas 40.000 m^2dan memiliki kedalaman kolam tampung 3,5 m. Kolam tampung ini juga menggunakan pompa dan pintu air. Pompa air yang digunakan berkapasitas rencana, 4,329 m^3⁄s dan menggunakan 4 pintu air yang memiliki lebar pintu 4,25 m dan tinggi pintu 3,5 meter. ==================================================================================================== Sadar River is located in Mojokerto, East Java. It has 27,750 m of length, and 88,749 〖km〗^2 of area and elevation range between +20 to +900 of downstream and upstream respectively. It was experiencing flood that generate inundation aroud residential area especially during rainy seasons. This study is focussed on 4900 m length of river. There are two main factors as flood trigger. Firstly, an upstream area of the river has steep contour and suddenly change into a flat area at the downstream. This condition is affecting the flow time in channel especially in downstream area as an upstream area contributes high flow rapidly. Secondly, the capacity of Sadar River is smaller than runoff discharge. Hence, water pump, sluice gate, storage and normalization of Sadar River can be designed toovercome flood occurrence. In order to prevent flood in Sadar River, the design of flood control is required. Some of data related to the design would be used such as, river cross section, rainfall height data, topographic map, and land use map of Sadar River Basin. Cross section data is used as channel capacity analysis, while rainfall height is raw data for return period of rainfall analysis. Topographic map analysis resulted the basin border and area as well. Land use situation provides the information of covering area types; hence the runoff coefficient can be determined. According to the data above, the design of flood was calculating with the following conditions. If an initial channel capacity is shorter than design flood, then the normalization, reservoir, sluice gate and pump in Sadar River should be analysed. 0,50 to 1,0 m of dike is added along flooded segment of Sadar River. It has 1:1 of slope ratio and 1,0 m of top width. This construction would be applied from Sta. 500 to Sta. 3600. However, this construction is not enough to accommodate flood design as normalization work could not be done in Sadar River. In advance, artificial reservoir is added to provide more storage for flood. The reservoir is planned at the upstream of inundation area. It has 40.000 m2 of area and 3,50 m of depth. This facility is equipped by gate and pump as outlet system. The pump would be 4,329 m3/s of capacity, while 4 gates with 4,25 m of width and 3,5 m of height were designed to be installed.

Item Type: Thesis (Undergraduate)
Uncontrolled Keywords: Flood, Sadar River, Normalization, Mojokerto, HEC-RAS, Banjir, Kali Sadar, Normalisasi, Mojokerto, HEC-RAS
Subjects: T Technology > TC Hydraulic engineering. Ocean engineering
T Technology > TC Hydraulic engineering. Ocean engineering > TC167 Dams, reservoirs
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: Ardhika Pasaratri Purbalaras
Date Deposited: 25 Feb 2021 18:01
Last Modified: 25 Feb 2021 18:01
URI: https://repository.its.ac.id/id/eprint/82890

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