Pemetaan Bencana Banjir Berdasarkan Faktor Ancaman Fisik Di Kabupaten Purworejo

M Muas Ramadhani, Dr. Ir. Catur Aries Rokhmana, S.T., M.T., IPU.

2025 | Tesis | S2 Teknik Geomatika

Kabupaten Purworejo belum memiliki peta bencana banjir dengan data terkini dan masih mengacu pada peta lama dari BNPB tahun 2022. Kabupaten Purworejo merupakan wilayah yang sering mengalami banjir. Menurut data Badan Penanggulangan Bencana Daerah (BPBD) Kabupaten Purworejo, banjir besar pernah melanda pada Maret 2025 karena intensitas hujan yang tinggi, menyebabkan rumah dan jalan tergenang. Penelitian ini bertujuan memetakan ancaman fisik bencana banjir di Kabupaten Purworejo. Pengolahan peta ancaman fisik banjir dilakukan dengan memanfaatkan teknologi penginderaan jauh dan pengolahan data berbasis platform Google Earth Engine (GEE). Analisis faktor tutupan lahan menggunakan GEE dengan mempertimbangkan berbagai faktor seperti curah hujan, kelerengan, tutupan lahan, infiltrasi, dan genangan banjir. Data tutupan lahan diklasifikasi dari citra Sentinel-2A, sedangkan data kelerengan dan genangan banjir diperoleh dari DEMNAS serta data curah hujan dari CHIRPS. Data infiltrasi diambil dari Kementerian ESDM. Validasi klasifikasi menggunakan metode Random Forest dengan tingkat akurasi 95,43?rdasarkan matrix confusion. Pemetaan genangan banjir juga divalidasi menggunakan matrix confusion dengan data kejadian banjir BPBD Kabupaten Purworejo. Hasil penelitian menunjukkan bahwa Kabupaten Purworejo memiliki empat kategori ancaman banjir, yaitu ancaman tinggi seluas 5.746,74 ha, ancaman sedang 35.803,712 ha, ancaman rendah 115.1.694,01 ha, dan wilayah tanpa ancaman seluas 75.279,49 ha. Faktor utama penyebab ancaman banjir adalah kelerengan, curah hujan, dan infiltrasi tanah. Peta ancaman fisik bencana banjir Kabupaten Purworejo menunjukkan bahwa mayoritas wilayah memiliki potensi ancaman banjir.

Purworejo Regency does not yet have a flood disaster map with updated data and land cover and is still using the 2022 map from the BNPB. Purworejo Regency is an area that frequently experiences flooding disasters. According to data from the Purworejo Regency Regional Disaster Management Agency, a major flood hit Purworejo Regency on March 29, 2025 due to excessive rainfall intensity, causing houses and roads to be submerged in water. This study was conducted to map the threat of flooding in Purworejo Regency. This study was conducted to map flood hazard threats in Purworejo Regency as part of disaster mitigation efforts. Flood hazard mapping can be carried out by utilizing remote sensing technology and spatial data processing on the Google Earth Engine (GEE) platform. The threat analysis of land cover was done using Google Earth Engine. Mapping of physical threats from flood disaster was carried out by integrating various factors such as rainfall, slope, land cover, soil infiltration, and flood inundation in Purworejo Regency. Land cover data was classified from Sentinel-2A imagery, slope and flood inundation from the National Digital Elevation Model (DEMNAS), rainfall from CHIRPS satellite data, and soil infiltration data from the Ministry of Energy and Mineral Resources. The accuracy test of the Random Forest classification results used a confusion matrix with a total accuracy of 95.43%. Flood inundation modeling has been tested for accuracy with data from the Purworejo Regency Regional Disaster Management Agency. The physical threat map of flood dangers in Purworejo Regency was tested for accuracy by comparing flood events recorded by the Flood Disaster Management Agency. The results show that Purworejo Regency has four categories of flood threats: high threat covering an area of 5,746.74 ha, medium threat covering an area of 35,803.712 ha, low threat covering an area of 11,694.01 ha, and the rest are no flood threat. The area of physical flood hazard factors includes land cover covering 75,279.94 ha, flood inundation covering 57,655.93 ha, and soil infiltration covering 48,460.61 ha. Mapping of physical threats from flood disaster in Purworejo Regency indicates that the majority of the region is potentially at risk of flooding.

Kata Kunci : Banjir, Random Forest, Google Earth Engine, Curah Hujan, Tutupan Lahan, Kelerengan, Infiltrasi Tanah