Skenario Pengurangan Risiko Banjir di DAS Rejoso, Pasuruan Melalui Penerapan Infrastruktur Hijau dan Abu-Abu

Dmayo, Rendra Alfito (2025) Skenario Pengurangan Risiko Banjir di DAS Rejoso, Pasuruan Melalui Penerapan Infrastruktur Hijau dan Abu-Abu. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Ketidakseimbangan hidrologi yang terjadi di DAS Rejoso terjadi akibat masifnya konversi lahan terbangun dan penambangan batu pasir sehingga mendorong terjadinya banjir. Bencana banjir yang terjadi di DAS Rejoso telah merendam 4000 rumah di 17 desa di 3 kecamatan, memutus jalan penghubung antar kecamatan, serta melumpuhkan jalur pantura. Hal ini menyebabkan kondisi dari DAS Rejoso termasuk dalam kategori paling kritis di Pasuruan. Penelitian ini bertujuan untuk merumuskan skenario pengurangan risiko banjir melalui penerapan infrastruktur hijau dan abu-abu. Metode yang digunakan mencakup pemodelan limpasan permukaan menggunakan model SWAT untuk menghitung debit limpasan pada tahun 2023 serta prediksi tahun 2043 berdasarkan skenario tata ruang. Hasil simulasi SWAT menunjukkan performa model yang memuaskan dengan nilai R² dan Nash-Sutcliffe Efficiency (NSE) berturut-turut sebesar 0,98 dan 0,516 di Rejoso Hulu serta 0,98 dan 0,906 di Rejoso Hilir. Berdasarkan hasil simulasi tahun 2023, teridentifikasi sebanyak 12 titik Sub-DAS berpotensi banjir dengan total volume limpasan sebesar 39.581,86 m³. Titik Sub-DAS yang berpotensi meliputi Sub-DAS 1, 2, 3, 4, 5, 8, 9, 12, 17, 19, 25, dan 26, yang tersebar di Kecamatan Rejoso, Grati, dan Winongan. Pada tahun 2043, jumlah Sub-DAS yang berisiko banjir diprediksi meningkat menjadi 14 SubDAS, dengan tambahan titik risiko baru pada Sub-DAS 18 dan 20. Total limpasan luapan air pada tahun 2043 diperkirakan mencapai 50.854.789,24 m³. Dalam upaya mengurangi risiko banjir di masa mendatang maka disusun empat skenario pengurangan limpasan yang melibatkan penerapan infrastruktur hijau dan abu-abu. Setiap skenario dianalisis menggunakan pendekatan sensitivitas sebesar 10% terhadap masing-masing jenis infrastrukturnya. Skenario no action sebagai asumsi, tingkat perlindungan banjir akan tetap sama di masa mendatang menunjukkan tidak ada pengurangan limpasan. Skenario hijau dilakukan dengan melakukan intervensi infrastruktur hijau meliputi bioretensi, perkerasan permeabel, taman hujan, atap hijau rain harvesting, constructed wetland, detention pond, perforated pipe. Pada skenario hijau pada kawasan banjir melakukan intervensi pada wilayah yang memiliki potensi risiko banjir berhasil menurunkan limpasan sebanyak 11,51%. Pada skenario hijau pada sumber rawan banjir dengan fokus intervensi infrastruktur hijau pada seluruh wilayah DAS Rejoso, memberikan pengurangan limpasan sebesar 17,76%. Skenario abu-abu dengan melakukan penambahan kapasitas drainase dapat mengurangi limpasan sebesar 10,63%, namun efektivitas yang dihasilkan lebih rendah dibandingkan skenario hijau. Terakhir, pada skenario kombinasi hijau—abu-abu menunjukkan hasil terbaik dengan pengurangan limpasan sebesar 39,56% sehingga debit limpasan yang dihasilkan mengalami penurunan sebesar 7.222.635,58 m³. Berdasarkan berbagai skenario tersebut, terdapat penurunan risiko banjir yang signifikan, terutama di Sub-DAS 4, yang mengalami pengurangan limpasan hingga 100%, sehingga menyebabkan potensi risiko bencana banjir hanya mencakup 13 Sub-DAS. Pada Sub-DAS 9, 18, dan 20 mengalami pengurangan limpasan lebih dari 50% dari kondisi dasar. Selain itu, pada Sub-DAS yang berpotensi banjir lainnya juga menunjukkan penurunan debit limpasan banjir yang signifikan.
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The hydrological imbalance in the Rejoso Watershed is primarily caused by massive land conversion for built-up areas and extensive sand and stone mining activities, which have triggered frequent flooding. Flood events in DAS Rejoso have inundated 4,000 houses across 17 villages in three sub-districts, disrupted inter-district road access, and paralyzed the northern coastal route (Pantura). These conditions categorize DAS Rejoso as one of the most critical watersheds in Pasuruan. This study aims to formulate flood risk reduction scenarios by applying green and grey infrastructure. The method used involves surface runoff modeling using the SWAT model to calculate runoff discharge for 2023 and future projections for 2043 based on spatial planning scenarios. The SWAT simulation results show satisfactory model performance with R² and Nash-Sutcliffe Efficiency (NSE) values of 0.98 and 0.516, respectively, in Rejoso Hulu and 0.98 and 0.906 in Rejoso Hilir. Based on the 2023 simulation results, 12 sub-watershed points with flood potential were identified, with a total runoff volume of 39,581.86 m³. The Sub-DAS points with potential flooding include Sub-DAS 1, 2, 3, 4, 5, 8, 9, 12, 17, 19, 25, and 26, which are spread across the districts of Rejoso, Grati, and Winongan. By 2043, the number of flood-prone sub-watersheds is projected to increase to 14, with new risks emerging in Sub-DAS 18 and 20. The total projected runoff volume in 2043 is estimated at 50,854,789.24 m³. To address future flood risks, five runoff reduction scenarios were developed, incorporating green and grey infrastructure interventions. Each scenario was analyzed using a 10% sensitivity approach for each infrastructure type. The no-action scenario, which assumes the current level of flood protection remains unchanged, shows no reduction in runoff. The green infrastructure scenario, which includes interventions such as bioretention, permeable pavement, rain gardens, green roofs, rainwater harvesting, constructed wetlands, detention ponds, and perforated pipes, was applied in two ways. When focused on flood-prone areas, it resulted in a 11.51% reduction in runoff. When applied across the entire watershed, it achieved a 17.76% reduction. The grey infrastructure scenario, involving increased drainage capacity, resulted in a 10.63% reduction, although less effective than the green scenarios. The combined green–grey infrastructure scenario yielded the best result with 39.56% runoff reduction, resulting in a decrease in runoff discharge of 7,222,635.58 m³. Based on the various scenarios analyzed, there was a significant reduction in flood risk, particularly in Sub-DAS 4, which experienced a 100% reduction in runoff, thus limiting the potential flood risk to only 13 Sub-DAS. Sub-DAS 9, 18, and 20 also experienced a runoff reduction of more than 50% compared to the baseline conditions. Additionally, other Sub-DAS areas with flood potential also exhibited significant reductions in flood runoff.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Banjir, DAS, Infrastruktur Hijau, Infrastruktur Abu-Abu, Skenario, Flood, Watershed, Green Infrastructure, Grey Infrastructure, Scenario
Subjects:	G Geography. Anthropology. Recreation > GB Physical geography > GB1399.2 Flood forecasting. G Geography. Anthropology. Recreation > GB Physical geography > GB1399.9 Floods T Technology > TD Environmental technology. Sanitary engineering > TD171.75 Climate change mitigation
Divisions:	Faculty of Architecture, Design, and Planning > Regional and Urban Planning > 35201-(S1) Undergraduate Thesis
Depositing User:	Rendra Alfito Dmayo
Date Deposited:	29 Jul 2025 04:09
Last Modified:	29 Jul 2025 04:09
URI:	http://repository.its.ac.id/id/eprint/122570

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