Analisis Karakteristik Dan Pengaruh Pasang Surut Terhadap Banjir Rob

Nurpratama, Ichwan Wahyu (2025) Analisis Karakteristik Dan Pengaruh Pasang Surut Terhadap Banjir Rob. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Analisis dinamika hidrologi dan pemodelan banjir di DAS Jragung, Kabupaten Demak, dilakukan untuk mengatasi kerentanan terhadap banjir rob. Evaluasi model hidrologi menggunakan data curah hujan satelit NASA dari 2005 hingga 2024. Data satelit seringkali bias, sehingga dikalibrasi menggunakan metode Quantile Mapping untuk meminimalisir deviasi dan menghasilkan masukan akurat untuk HEC-HMS serta perhitungan kala ulang curah hujan. Proses kalibrasi menyesuaikan distribusi kumulatif data model agar sesuai dengan data observasi historis.Perhitungan tinggi hujan rencana menggunakan Distribusi Log Pearson III. Transformasi data hujan harian menjadi jam-jaman dilakukan dengan metode Mononobe, dengan puncak intensitas hujan pada jam pertama dan penurunan bertahap selama enam jam. Performa model sangat memuaskan, dengan fase kalibrasi (2005–2019) mencapai R2 dan NSE 0.96, RMSE 5.47, dan bias 0.05. Meskipun sedikit menurun pada fase validasi (2020–2024), model tetap dalam kategori sangat baik dengan R2 dan NSE 0.91, RMSE 6.69, dan bias -4.62. Ini menegaskan keandalan model dalam mereplikasi kondisi hidrologi aktual. Pemodelan banjir dua dimensi menggunakan HEC-RAS membandingkan skenario banjir tanpa dan dengan pengaruh pasang surut air laut. Skenario tanpa pasang surut menunjukkan peningkatan kedalaman genangan dari 6.05 meter (2 tahun) menjadi 7.19 meter (50 tahun), mencerminkan korelasi dengan intensitas hujan. Namun, ketika pasang surut air laut dipertimbangkan, luas genangan meningkat signifikan. Sebagai contoh, pada kala ulang 2 tahun, luas genangan meningkat drastis dari 33.52 km2 menjadi 145.06 km2. Demikian pula, pada kala ulang 50 tahun, luas genangan melonjak dari 57.82 km2 menjadi 373.83 km2. Peningkatan konsisten dan substansial ini mengindikasikan dampak besar pasang surut air laut terhadap extent dan kedalaman genangan banjir di wilayah pesisir Demak. Oleh karena itu, integrasi variabel pasang surut sangat krusial dalam perencanaan mitigasi banjir yang efektif dan realistis di kawasan pesisir.
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Hydrological dynamics analysis and flood modeling in the Jragung Watershed, Demak Regency, were conducted to address vulnerability to tidal flooding. The hydrological model evaluation used NASA satellite rainfall data from 2005 to 2024. Satellite data is often biased, so it was calibrated using the Quantile Mapping method to minimize deviations and produce accurate input for HEC-HMS and rainfall return period calculations. The calibration process adjusted the cumulative distribution of model data to match historical observation data. The calculation of the planned rainfall height used the Log Pearson III Distribution. The transformation of daily rainfall data into hourly data was carried out using the Mononobe method, with the peak rainfall intensity in the first hour and a gradual decrease over six hours. The model performance was very satisfactory, with the calibration phase (2005–2019) achieving R2 and NSE of 0.96, RMSE of 5.47, and bias of 0.05. Despite a slight decline during the validation phase (2020–2024), the model remained in the excellent category with an R2 and NSE of 0.91, an RMSE of 6.69, and a bias of -4.62. This confirms the model's reliability in replicating actual hydrological conditions. Two-dimensional flood modeling using HEC-RAS compared flood scenarios with and without tidal influence. The scenario without tidal influence showed an increase in inundation depth from 6.05 meters (2 years) to 7.19 meters (50 years), reflecting a correlation with rainfall intensity. However, when tidal influence was considered, the inundation area increased significantly. For example, at the 2-year return period, the inundation area increased dramatically from 33.52 km2 to 145.06 km2. Similarly, at the 50-year return period, the inundation area jumped from 57.82 km2 to 373.83 km2. This consistent and substantial increase indicates the significant impact of tidal influence on the extent and depth of flood inundation in the coastal area of Demak. Therefore, the integration of tidal variables is crucial in effective and realistic flood mitigation planning in coastal areas.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Banjir rob, Pasang surut, Pesisir, Kedalaman, Demak Coastal flooding, Tidal, Coast, Depth, Demak
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Divisions:	Faculty of Civil, Environmental, and Geo Engineering > Civil Engineering > 22101-(S2) Master Theses
Depositing User:	Ichwan Wahyu Nurpratama
Date Deposited:	28 Jul 2025 02:54
Last Modified:	28 Jul 2025 02:54
URI:	http://repository.its.ac.id/id/eprint/121829

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