Pengaruh Pasang Air Laut Terhadap Banjir Kali Welang

Gasa, Ainun Mumtaz Muhammad (2025) Pengaruh Pasang Air Laut Terhadap Banjir Kali Welang. Masters thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Kali Welang merupakan sungai di Kabupaten dan Kota Pasuruan yang sering mengakibatkan banjir di wilayah hilir. Banjir ini diperparah oleh curah hujan tinggi, sedimentasi, dan pengaruh signifikan dari pasang surut air laut yang menyebabkan aliran balik (backwater), sehingga meningkatkan tinggi dan luas genangan. Penelitian ini bertujuan untuk memperoleh debit banjir rencana, menganalisis pengaruh pasang surut terhadap tinggi muka air, dan mengkaji dampak kenaikan permukaan air laut saat fenomena supermoon terhadap luasan genangan. Metodologi penelitian ini menggunakan pemodelan hidrologi menggunakan HEC-HMS untuk menghitung debit banjir rencana dengan periode ulang 2 hingga 100 tahun. Selanjutnya, pemodelan hidrolika 2D dengan HEC-RAS digunakan untuk menyimulasikan genangan dalam tiga skenario: banjir tanpa pasang surut, banjir dengan pasang surut normal (tinggi pasang 2,18 m), dan banjir dengan pasang surut saat supermoon (tinggi pasang 3,05 m). Hasil analisis menunjukkan debit banjir rencana periode ulang 100 tahun (Q100) mencapai 409,7 m³/detik. Pengaruh pasang surut secara signifikan memperluas genangan banjir pada Q100 dari 0,57 km² menjadi 1,53 km², sebuah peningkatan sebesar 62,7%. Fenomena supermoon memperparah kondisi ini, dengan luas genangan Q100 mencapai 1,73 km², atau meningkat 11,15% dibandingkan kondisi pasang surut normal. Peningkatan luasan terbesar akibat supermoon terjadi pada periode ulang Q5, yakni sebesar 34,81%. Disimpulkan bahwa pasang surut air laut, terutama saat supermoon, memiliki peran krusial dalam meningkatkan tinggi dan luasan genangan di hilir Kali Welang.
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The Welang River, which flows through the Regency and City of Pasuruan, frequently causes flooding in its downstream area. This flooding is exacerbated by high rainfall, sedimentation, and a significant influence from tidal backwater effects, which increase the height and extent of inundation. This study aims to determine the design flood discharge, analyze the impact of tides on water surface elevation, and examine the effect of sea-level rise during a supermoon phenomenon on the inundated area. This research methodology employed hydrological modeling with HEC-HMS to calculate the design flood discharge for return periods ranging from 2 to 100 years. Subsequently, 2D hydraulic modeling with HEC-RAS was used to simulate the inundation under three scenarios: flooding without tidal influence, flooding with normal tides (a high tide of 2.18 m), and flooding with supermoon tides (a high tide of 3.05 m). The analysis revealed that the 100-year return period design flood discharge (Q100) is 409.7 m³/s. The influence of tides significantly expands the Q100 flood inundation area from 0.57 km² to 1.53 km², a 62.7% increase. The supermoon phenomenon worsens this condition, with the Q100 inundation area reaching 1.73 km², an 11.15% increase compared to normal tidal conditions. The largest increase in inundation area due to the supermoon occurs at the 5-year return period (Q5), with an increase of 34.81%. It is concluded that ocean tides, particularly during a supermoon, play a crucial role in increasing the height and extent of flooding in the downstream area of the Welang River.

Item Type:	Thesis (Masters)
Uncontrolled Keywords:	Kali Welang, Pasang Surut, Banjir, Genangan , HEC-RAS, HEC-HMS, Supermoon, Welang River, Tidal, Flooding
Subjects:	T Technology > TC Hydraulic engineering. Ocean engineering > TC333 Breakwaters T Technology > TC Hydraulic engineering. Ocean engineering > TC424 Water levels T Technology > TC Hydraulic engineering. Ocean engineering > TC530 Flood control
Divisions:	Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22101-(S2) Master Thesis
Depositing User:	Ainun Mumtaz Muhammad Gasa
Date Deposited:	23 Jul 2025 06:39
Last Modified:	23 Jul 2025 06:39
URI:	http://repository.its.ac.id/id/eprint/120869

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