REHABILITASI BENDUNG SINOMAN DI KALI BRANGKAL UNTUK MENGATASI BANJIR DI DESA SOOKO, KOTA MOJOKERTO TESIS

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REHABILITASI BENDUNG SINOMAN DI KALI BRANGKAL UNTUK MENGATASI BANJIR DI DESA SOOKO, KOTA MOJOKERTO

TESIS

Untuk Memenuhi Sebagian Persyaratan Mencapai Derajat Magister

Oleh: IWAN JOKO SULOMO NIM S941302019

PROGRAM PASCASARJANA UNIVERSITAS SEBELAS MARET SURAKARTA 2015to user commit

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DAFTAR ISI

HALAMAN JUDUL ............................................................................................................... i HALAMAN PERSETUJUAN................................................................................................. ii HALAMAN PENGESAHAN ................................................................................................. iii PERYATAAN ........................................................................................................................ iv KATA PENGANTAR ............................................................................................................. v UCAPAN TERIMA KASIH.................................................................................................... vi DAFTAR ISI .......................................................................................................................... viii DAFTAR GAMBAR ............................................................................................................... x DAFTAR TABEL ................................................................................................................... xi DAFTAR SIMBOL ................................................................................................................. xiii DAFTAR LAMPIRAN ............................................................................................................ xv ABSTRAK ............................................................................................................................... xvi ABSTRACT ............................................................................................................................ xvii BAB I PENDAHULUAN ........................................................................................................ 1 1.1 Latar Belakang ...................................................................................................... 2 1.2 Rumusan Masalah ................................................................................................. 2 1.3 Batasan Masalah ................................................................................................... 2 1.4 Tujuan Penelitian .................................................................................................. 3 1.5 Manfaat Penelitian ................................................................................................ 3 BAB II TINJAUAN PUSTAKA DAN LANDASAN TEORI 2.1 Tinjauan Pustaka .................................................................................................. 4 2.1.1 Debit Banjir ............................................................................................... 4 2.1.2 Tinggi Muka Air ....................................................................................... 6 2.1.3 Bendung .................................................................................................... 6 2.2 Landasan Teori...................................................................................................... 6 2.2.1 Debit Banjir ............................................................................................... 6 2.2.2 Tinggi Muka Air ....................................................................................... 23 2.2.3 Bendung .................................................................................................... 25 BAB III METODE PENELITIAN .......................................................................................... 28 3.1 Lokasi Penelitian ................................................................................................... 28

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3.3 Data ....................................................................................................................... 29 3.4 Alat yang digunakan .............................................................................................. 29 3.5 Langkah-langkah Penelitian................................................................................... 31 3.6 Analisis Data .......................................................................................................... 32 BAB IV HASIL DAN PEMBAHASAN ................................................................................. 33 4.1 Debit...................................................................................................................... 33 4.1.1 Data Hujan ................................................................................................ 33 4.1.2 Uji Kepanggahan Data Hujan ................................................................... 33 4.1.3 Hujan Maksimum Harian Rerata Daerah .................................................. 36 4.1.4 Agihan Frekuensi Hujan ........................................................................... 37 4.1.5 Hujan Rancangan ...................................................................................... 41 4.1.6 Intensitas Hujan, Pola Agihan Hujan Jam-jaman ..................................... 42 4.1.7 Analisis Hidrograf Terukur ....................................................................... 44 4.1.8 Debit Rencana ........................................................................................... 46 4.2 Tinggi Muka Air ................................................................................................... 50 4.2.1 Geometri Jaringan Sungai ......................................................................... 50 4.2.2 Input data Tampang Melintang Sungai ..................................................... 51 4.2.3 Input bangunan bendung dengan menu inline structure ........................... 52 4.2.4 Input data aliran dan boundary condition ................................................ 52 4.2.5 Hasil simulasi ............................................................................................ 53 4.3 Bendung ................................................................................................................. 56 4.3.1 Input bangunan bendung dengan menu inline structure ........................... 56 4.3.2 Hasil simulasi ............................................................................................ 57 4.4 Peninggian Tanggul ............................................................................................... 60 BAB V KESIMPULAN DAN SARAN .................................................................................. 64 5.1 Kesimpulan ............................................................................................................ 64 5.2 Saran ...................................................................................................................... 64 DAFTAR PUSTAKA LAMPIRAN

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DAFTAR TABEL

Tabel 2.1. Nilai Kritik Q dan R.............................................................................................. 7 Tabel 2.2. Tabel Agihan Chi Kuadrat X2 ............................................................................... 11 Tabel 2.3. Tabel Nilai kritis Do untuk Uji Smirnov-Kolmogorov ......................................... 11 Tabel 2.4. Nilai Variabel (k) Reduksi Gauss ......................................................................... 12 Tabel 2.5. Nilai Sn dan Yn..................................................................................................... 12 Tabel 2.6. Nilai Variabel (Y) Reduksi Gumbel ..................................................................... 13 Tabel 2.7. Nilai k Agihan Log Pearson Type III ................................................................... 13 Tabel 3.1 Parameter dan Variable yang terkait dengan penelitian ........................................ 29 Tabel 4.1 Hujan Maksimum Tahunan DAS Brangkal ........................................................... 33 Tabel 4.2 Hujan Harian Maksimum dan Jumlah Hujan Tahunan Sta. Cakarayam ............... 34 Tabel 4.3 Nilai Kritik Q untuk Uji Kepanggahan .................................................................. 34 Tabel 4.4 Uji Kepanggahan Sta. Cakarayam ......................................................................... 35 Tabel 4.5 Uji Kepanggahan Stasiun Hujan DAS Brangkal ................................................... 35 Tabel 4.6 Nilai Koefisien Tiessen .......................................................................................... 36 Tabel 4.7 Hujan Maksimum DAS Brangkal .......................................................................... 37 Tabel 4.8 Analisis Agihan Frekuensi Hujan dengan Metode Agihan Normal ...................... 37 Tabel 4.9 Hasil Pengukuran Dispersi..................................................................................... 38 Tabel 4.10 Perhitungan Variabel Pengukuran Dispersi Dengan Logaritma .......................... 38 Tabel 4.11 Hasil Pengukuran Dispersi Dengan Logaritma ................................................... 39 Tabel 4.12 Perbandingan Hasil Pengukuran Dispersi Normal Dengan Dispersi Logaritma 39 Tabel 4.13 Hasil Uji Agihan Frekuensi ................................................................................. 39 Tabel 4.14 Metode Chi Kuadrat............................................................................................. 40 Tabel 4.15 Metode Smirnov-Kolmogorov ............................................................................. 41 Tabel 4.16. Perhitungan Hujan Rancangan Metode Log Pearson Type III ........................... 42 Tabel 4.17 Agihan Hujan Jam-Jaman untuk beragam Kala Ulang ........................................ 44 Tabel 4.18 Hujan Harian Pos Hujan Tanggal 2 Desember 2010 .......................................... 45 Tabel 4.19 Hidrograf Aliran Metode HSS Nakayasu ............................................................... 47 Tabel 4.20 Rekapitulasi Debit Rancangan dengan Metode Nakayasu ................................. 50 Tabel 4.21 Elevasi Muka Air di Kali Brangkal Hasil Simulasi Pada Kondisi Eksisting....... 53

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Tabel 4.22 Elevasi Muka Air di Kali Brangkal Hasil Simulasi pada Kondisi Modifikasi Mercu Bendung ................................................................................................... 57 Tabel 4.23 River Station yang Perlu Peninggian Tanggul ..................................................... 62

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DAFTAR GAMBAR

Gambar 2.1 Hidrograf Satuan Sintetik GAMA I .................................................................. 14 Gambar 2.2 Sketsa Penetapan WF ........................................................................................ 16 Gambar 2.3 Sketsa Penetapan RUA ..................................................................................... 17 Gambar 2.4 Hidrograf Satuan Sintesis Metode Nakayasu..................................................... 19 Gambar 2.5 Hidrograf Snyder-Alexeyef................................................................................ 23 Gambar 2.6 Perhitungan Profil Muka Air Tahap Langsung ................................................. 24 Gambar 2.7 Tipe Mercu Bendung ........................................................................................ 25 Gambar 3.1. Peta Lokasi Bendung Sinoman ......................................................................... 28 Gambar 3.2. Bendung Sinoman, di Kali Brangkal ................................................................ 30 Gambar 3.3 Langkah–langkah Penelitian ............................................................................. 31 Gambar 4.1 Lokasi Stasiun Penakar Hujan di DAS Brangkal............................................... 36 Gambar 4.2 Grafik Hubungan Tinggi Muka Air dan Debit................................................... 44 Gambar 4.3 Hidrograf Terukur dengan Hitungan.................................................................. 45 Gambar 4.4 Grafik HSS Nakayasu DAS Brangkal ............................................................... 50 Gambar 4.5 Kali Brangkal dalam Permodelan Hec-Ras ....................................................... 51 Gambar 4.6 Menu Input Data Tampang Melintang ............................................................... 51 Gambar 4.7 Bendung Sinoman dalam Permodelan Hec-Ras ............................................... 52 Gambar 4.8 Pengaturan Boundary Condition Permodelan Kali Brangkal ............................ 52 Gambar 4.9 Profil Muka Air Kondisi Bendung Eksisting ..................................................... 53 Gambar 4.10 Modifikasi Bendung dalam Permodelan HEC-RAS........................................ 56 Gambar 4.11 Profil Muka Air Pada Kondisi Modifikasi Mercu Bendung ............................ 57 Gambar 4.12 Profil Muka Air Pada River Station 14 ............................................................ 60 Gambar 4.13 Grafik Kapasitas Tampung dengan Volume Hidrograf ................................... 61 Gambar 4.14 River Station yang perlu Peninggian Tanggul ................................................. 63 Gambar 4.15 River Station 14 yang sudah ditinggikan ......................................................... 63

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Iwan Joko Sulomo, 2015. Rehabilitasi Bendung Sinoman di Kali Brangkal Untuk Mengatasi Banjir di Desa Sooko, Kota Mojokerto, Pembimbing I: Prof. Dr.Ir. Sobriyah MS . Pembimbing II: Dr. Ir. Mamok Suprapto, M. Eng. Tesis Magister Teknik Sipil, Minat Utama Teknik Rehabilitasi dan Pemeliharaan Bangunan Sipil, Program Pasca sarjana, Universitas Sebelas Maret, Surakarta.

ABSTRAK

Banjir merupakan permasalahan umum yang sering melanda sebagian besar wilayah Indonesia.Salah satunya terjadi di Kali Brangkal yang berada di Kota Mojokerto. Pada Tahun 2004 terjadi banjir di Kota Mojokerto, Banjir tersebut disebabkan karena adanya beberapa ruas tanggul yang putus di hulu Bendung Sinoman. Akibatnya, timbul genangan air di Desa Sooko,Kota Mojokerto. Selain itu, ada dugaan bahwa penyebab jebolnya tanggul akibat dari dampak pembendungan pada Bendung Sinoman. Untuk itu permasalahan banjir perlu segera diatasi sebab daerah yang banjir merupakan daerah pemukiman penduduk Penelitian ini dilakukan dengan pendekatan sederhana untuk mencari kesesuaian debit puncak dan bentuk hidrograf aliran antara hidrograf terukur dan hidrograf satuan sintetis pada daerah aliran Kali Brangkal, beberapa metode seperti metode Gama I, metode Nakayasu, metode Snyder, metode ITB-1 dan metode ITB-2 digunakan untuk menghitung debit puncak. Untuk memperoleh profil muka air dilakukan simulasi dengan bantuan software Hec-Ras. Konsep yang direncanakan dalam rangka pengendalian banjir tersebut yaitu dengan modifikasi Bendung Sinoman dengan mengurangi tinggi mercu bendung, penurunan mercu bendung diharapkan dapat menurunkan tinggi muka air dihulu bendung yang menjadi penyebab banjir Hasil dari penelitian ini, menunjukkan bahwa hidrograf yang paling sesuai dengan hidrograf terukur adalah hidrograf sintetik Nakayasu. Debit puncak pada hidrograf kala ulang 100 tahun adalah sebesar 636,25 m3/s. Hasil simulasi dengan input debit kala ulang 100 tahun pada kondisi bendung eksisiting terjadi banjir. Dan dilakukan modifikasi terhadap Bendung Sinoman dengan mengurangi tingggi mercu 3m hasilnya belum dapat mengatasi banjir. Untuk mengatasi hal itu perlu peninggian tanggul 1 m di tanggul sebelah kiri dan 1.5 m di tanggul sebelah kanan. Hasil simulasi dengan peninggian tanggul, banjir di hulu bendung dapat teratasi. Kata kunci : Debit Banjir, Mercu bendung, Hec-ras,Tanggul,Tinggi Muka Air.

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Iwan Joko Sulomo, 2015.Bendung Sinoman Rehabilitation at Brangkal River to Overcome Flood in Sooko Village, Mojokerto, Supervisor I: Prof. Dr.Ir. Sobriyah MS.Supervisor II:Dr. Ir. Mamok Suprapto, M. Eng. Thesis of Civil Engineering, Majoring on Rehabilitation technique and Civil Building Maintenance,Postgraduate Program, Universitas Sebelas Maret, Surakarta.

ABSTRACT Flood is common problem that occurs at most areas in Indonesia, one of them is happened at Brangkal river which is located in Mojokerto. In 2004, flood struck Mojokerto due to its overflow. The flood is appeared because of the embankment breakage at several joints in headwater of BendungSinoman. Thus, the pool was created in Sooka village, Mojokerto. Besides, there is a conjecture related to the embankment burst which is caused by damming at BendungSinoman. Hence, the flood problem should be overcome for the area where it occurred is the settlement area. The first step of this study is to obtain the compatibility of peak discharge and the shape of flow hydrograph between measured hydrograph and synthetic unit hydrograph at area of Brangkal river flow, some method as Gama I,Nakayasu,Snyder, ITB-1 dan ITB-2 is used to measure the peak discharge. To discover the profile of water surface, Hec-ras software is used to simulate it, and the planned concept to control the flood is modification on Bendung Sinoman by decreasing the height of dam summit to decrease the height of water surface at dam headwater causing the flood. The result of this study shows that the suitable hydrograph of measured hydrograph is Nakayasu synthetic hydrograph. The peak discharge at hydrograph in 100 year cycle is 636.25 m3/s. the simulation result on discharge input in 100 year cycle at existing dam condition creates flood, and the modification on Bendung Sinoman by decreasing 3m on the height of dam summit still creates flood, on the other word, it does not overcome the flood problem occurred. To overcome this problem, the embankment elevation is needed for 1m height on the left and 1.5m height on the right. The result of embankment elevation simulation is that it can overcome the flood occurred at dam headwater. Keywords: flood discharge, dam summit, Hec-Ras, levee, water level

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REHABILITASI BENDUNG SINOMAN DI KALI BRANGKAL UNTUK MENGATASI BANJIR DI DESA SOOKO, KOTA MOJOKERTO TESIS

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