Potensi Penerapan Infrastruktur Hijau dalam Upaya Mengurangi Genangan Banjir di Kawasan Sub DAS Cisangkuy

Abstract

Abstract. Changes in land use in the upstream area are known to be one of the causes of an increase in surface runoff, which results in an increase in the intensity and frequency of floods. One of the flood events that occurred as a result of runoff from upstream rivers was the flood that occurred in Dayeuhkolot District, Baleendah District, and Bojongsoang District which is the estuary of the confluence of 3 rivers, including the Citarum River, Cikapundung River, and Cisangkuy River. The Cisangkuy SUB-DAS has a run off of 559.6 million m³/year and supplies high runoff water to the Citarum River. The government's efforts, namely the Cisangkuy floodway, can reduce the duration of flood inundation, but when the rainfall is very high, floods continue to stagnate in the three sub-districts. For this reason, this study aims to identify the potential for implementing green infrastructure in reducing flood inundation in the Cisangkuy sub-watershed area. This research consists of three stages. The first stage is analyzing the type and distribution of potential green infrastructure locations using intersection analysis and select by attributes. The second stage calculates the planned flood discharge using Log Pearson Type III and SCS (Soil Conservation Service). The third stage is an analysis of the ability of green infrastructure to reduce flood inundation. The results showed that there are three types of green infrastructure whose criteria are in accordance with the characteristics, namely wet ponds, dry ponds, and Vegetated Filter Strips. Locations that have the potential to be implemented are Pameungpeuk District, Banjaran District, and Cangkuang District. The location points chosen for the retention pond development are in Ranca Tungku Village, Pameungpeuk District, and Kamasan Village, Banjaran District. The calculation results show that the volume of inundation from the Cisangkuy sub-watershed is 20.854.101.25 m3 . The ability of green infrastructure in reducing flood inundation results in the percentage of detention ponds (1.13%) Because the results are less significant, then the simulation is carried out again if the area of the detention pond is expanded, the result is that the detention ponds get results (12.49%), retention ponds (5 %), vegetated filter strip (3.4%). The results of the combination of detention ponds, retention ponds and vegetated filter strips will result in a reduction in the percentage of 20.89%.

Keywords: Green Infrastructure, Flood Inundation, Watershed.

Abstrak. Perubahan penggunaan lahan di Kawasan hulu sungai diketahui sebagai salah satu penyebab peningkatan limpasan permukaan, yang mengakibatkan meningkatnya intensitas dan frekuensi banjir. Salah satu kejadian banjir yang terjadi akibat dari limpasan hulu sungai adalah banjir yang terjadi di Kecamatan Dayeuhkolot, Kecamatan Baleendah, dan Kecamatan Bojongsoang yang merupakan muara dari dari pertemuan 3 sungai, antara lain Sungai Citarum, Sungai Cikapundung, dan Sungai Cisangkuy. Sub DAS Cisangkuy memiliki run off sebesar 559,6 juta m³/tahun dan menyuplai air limpasan yang cukup tinggi ke Sungai Citarum. Upaya pemerintah yang sudah dilakukan yaitu floodway cisangkuy dapat mengurangi lama genangan banjir, tetapi ketika curah hujan sangat tinggi, banjir tetap menggenang di tiga kecamatan tersebut. Untuk itu penelitian ini bertujuan untuk mengidentifikasi potensi penerapan infrastruktur hijau dalam mengurangi genangan banjir di Kawasan Sub DAS Cisangkuy. Penelitian ini terdiri dari tiga tahapan. Tahap pertama yaitu analisis jenis dan sebaran lokasi potensial infrastruktur hijau menggunakan analisis intersect dan select by attributes. Tahap Kedua menghitung debit banjir rencana menggunakan Log Pearson Type III dan SCS (Soil Conservation Service). Tahap ketiga yaitu analisis kemampuan infrastruktur hijau dalam mengurangi genangan banjir.Hasil penelitian menunjukkan terdapat tiga jenis infrastruktur hijau yang kriterianya sesuai dengan karakteristik, yaitu kolam retensi (wet pond), kolam detensi (dry pond), dan Vegetated Filter Strip. Lokasi yang berpotensial untuk diterapkan adalah Kecamatan Pameungpeuk, Kecamatan Banjaran, dan Kecamatan Cangkuang. Titik Lokasi yang dipilih untuk pengembangan kolam retensi berada di Desa Ranca Tungku, Kecamatan Pameungpeuk dan Desa Kamasan, Kecamatan Banjaran. Hasil perhitungan menunjukkan volume genangan yang dari Sub DAS Cisangkuy sebesar 20.854.101,25 m³ . Kemampuan infrastruktur hijau dalam mengurangi genangan banjir mendapatkan hasil dengan persentase kolam detensi (1,13%) Karena hasilnya kurang signifikan, maka dilakukan simulasi kembali jika luas kolam detensi diperluas, hasilnya kolam detensi mendapat hasil (12,49%), kolam retensi (5%), vegetated filter strip (3,4%). Hasil kombinasi dari Kolam detensi, Kolam retensi dan Vegetated Filter Strip akan menghasilkan pengurangan dengan persentase sebesar 20,89%.

Kata Kunci: Infrastruktur Hijau, Genangan Banjir, Daerah Aliran Sungai