Pengaruh Pembangunan Bendungan Cabean Terhadap Pengendalian Banjir Di Sungai Galuk, Kabupaten Blora

Hasananda, Zahrah Ramadhania (2026) Pengaruh Pembangunan Bendungan Cabean Terhadap Pengendalian Banjir Di Sungai Galuk, Kabupaten Blora. Other thesis, Institut Teknologi Sepuluh Nopember.

Text 2036221036-Undergraduate_Thesis.pdf - Accepted Version Restricted to Repository staff only Download (69MB) | Request a copy

Abstract

Banjir merupakan salah satu bencana hidrometeorologi yang sering terjadi akibat kapasitas penampang sungai yang tidak mampu mengalirkan debit banjir. Salah satu upaya pengendalian banjir di Kabupaten Blora adalah pembangunan Bendungan Cabean. Namun, efektivitas bendungan dalam mereduksi banjir dipengaruhi oleh kondisi sungai di hilir serta pola pengoperasian pintu pelimpah. Oleh karena itu, penelitian ini bertujuan untuk menganalisis kondisi banjir sebelum pembangunan Bendungan Cabean, mengevaluasi pengaruh variasi bukaan pintu pelimpah terhadap pengendalian banjir, serta menentukan alternatif pengendalian banjir apabila genangan masih terjadi. Metode yang digunakan meliputi analisis hidrologi untuk memperoleh debit banjir rencana, penelusuran banjir (flood routing) pada Bendungan Cabean dengan lima skenario bukaan pintu pelimpah, pemodelan hidraulik menggunakan HEC-RAS, serta analisis stabilitas lereng menggunakan GeoStudio. Alternatif pengendalian banjir dilakukan melalui normalisasi sungai dan pembangunan tanggul pada lokasi yang masih mengalami genangan. Hasil analisis menunjukkan bahwa pada kondisi eksisting masih terjadi luapan pada Sungai Galuk, Sungai Sambirejo, dan Sungai Kedunglo dengan luas genangan berturut-turut sebesar 0,0955 km², 0,1089 km², dan 0,1211 km² untuk debit banjir kala ulang Q25, Q50, dan Q100 dengan sebagian besar kedalaman genangan kurang dari 0,76 m. Analisis pengoperasian pintu Bendungan Cabean pada debit banjir kala ulang Q100 menunjukkan bahwa skenario pintu pelimpah tertutup (0%) memberikan reduksi terbesar sebesar 66,60%, diikuti dengan pintu terbuka ¼ (25%) sebesar 62,38%, pintu terbuka ½ (50%) sebesar 60,02%, pintu terbuka ¾ (75%) sebesar 55,81%, dan pintu terbuka penuh (100%) sebesar 54,06%.Hasil tersebut menunjukkan bahwa semakin besar bukaan pintu pelimpah, semakin kecil kemampuan Bendungan Cabean dalam mereduksi banjir karena debit yang dialirkan ke hilir semakin besar. Selanjutnya, penerapan normalisasi sungai dan pembangunan tanggul pada skenario pintu pelimpah terbuka penuh mampu meningkatkan efektivitas pengendalian banjir dengan mereduksi luas genangan sebesar 73,93% dibandingkan kondisi eksisting. Hasil analisis stabilitas menggunakan GeoStudio menunjukkan bahwa penampang hasil normalisasi pada Sungai Galuk, Sungai Sambirejo, dan Sungai Kedunglo memiliki nilai Factor of Safety (FoS) masing-masing sebesar 6,176, 12,604, dan 9,141. Seluruh nilai tersebut lebih besar dari 1,5, sehingga memenuhi kriteria stabilitas dan dinyatakan aman terhadap potensi kelongsoran.
======================================================================================================================================
Flooding is one of the most common hydrometeorological disasters, occurring when river channel capacities are insufficient to convey flood discharges. One of the flood mitigation measures implemented in Blora Regency is the construction of Cabean Dam. However, the effectiveness of the dam in reducing flood impacts is influenced by downstream river conditions and the operational pattern of its spillway gates. Therefore, this study aims to analyze flood conditions prior to the construction of Cabean Dam, evaluate the influence of various spillway gate opening scenarios on flood control performance, and determine alternative flood mitigation measures in areas where inundation still occurs. The methodology employed includes hydrological analysis to determine design flood discharges, flood routing analysis at Cabean Dam under different spillway gate opening scenarios, hydraulic modeling using HEC-RAS, and slope stability analysis using GeoStudio. Alternative flood mitigation measures were implemented through river normalization and levee construction at locations that remained inundated. The results indicate that, under existing conditions, flooding still occurs along the Galuk River, Sambirejo River, and Kedunglo River, with inundation areas of 0.0955 km², 0.1089 km², and 0.1211 km² for the Q25, Q50, and Q100 return-period floods, respectively. Most inundation depths were less than 0.76 m. Analysis of Cabean Dam operation under the Q100 flood event shows that the closed spillway gate scenario (0%) provides the highest flood reduction of 66.60%, followed by gate openings of 25%, 50%, 75%, and 100%, resulting in flood reductions of 62.38%, 60.02%, 55.81%, and 54.06%, respectively. These results indicate that larger spillway gate openings reduce the dam’s flood mitigation effectiveness because greater discharges are released downstream. Furthermore, the implementation of river normalization and levee construction under the fully open spillway gate scenario (100%) improved flood control effectiveness by reducing the inundation area by 73.93% compared to existing conditions. Stability analysis using GeoStudio shows that the normalized river sections of the Galuk River, Sambirejo River, and Kedunglo River achieved Factor of Safety (FoS) values of 6.176, 12.604, and 9.141, respectively. All values exceed the minimum stability criterion of 1.5, indicating that the proposed river sections are stable and safe against slope failure.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Flood, Cabean Dam, Flood Mitigation, Flood Reduction, Spillway Gate Operation, HEC-RAS, GeoStudio, Banjir, Bendungan Cabean, Pengendalian Banjir, Reduksi Banjir, Pola Operasi Pintu Bendungan, HEC-RAS, GeoStudio
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) 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 Vocational > 22301-Civil Infrastructure Engineering (D4)
Depositing User:	Zahrah Ramadhania Hasananda
Date Deposited:	03 Aug 2026 03:58
Last Modified:	03 Aug 2026 03:58
URI:	http://repository.its.ac.id/id/eprint/139499

Actions (login required)

View Item