Analisis Hubungan Spasial Keparahan Kebakaran Terhadap Amblesan Lahan Gambut Menggunakan Metode DInSAR dan dNBR di Kabupaten Pulang Pisau Tahun 2019

Amalia Puspita, peatland, burn severity, dNBR, DInSAR, land subsidence, Pulang Pisau Regency

2026 | Skripsi | TEKNIK GEODESI

Kebakaran hutan dan lahan pada ekosistem gambut menyebabkan hilangnya material organik serta memicu deformasi vertikal berupa amblesan lahan (land subsidence). Kabupaten Pulang Pisau, Provinsi Kalimantan Tengah, merupakan salah satu wilayah dengan lahan gambut yang mengalami kebakaran cukup luas pada tahun 2019 akibat kondisi musim kemarau yang diperkuat oleh fenomena El Niño. Meskipun pemetaan area terbakar dan deformasi lahan telah banyak dilakukan secara terpisah, informasi mengenai hubungan antara tingkat keparahan kebakaran dengan amblesan lahan gambut masih terbatas. Oleh karena itu, dilakukan identifikasi area bekas kebakaran dan tingkat keparahan kebakaran, estimasi deformasi vertikal lahan gambut pascakebakaran, serta analisis hubungan spasial dan signifikansi statistik antara tingkat keparahan kebakaran dan amblesan lahan gambut di Kabupaten Pulang Pisau tahun 2019.

Analisis tingkat keparahan kebakaran dilakukan menggunakan citra Landsat 8 pre-fire tanggal 1 Juni–4 Juli 2019 dan post-fire tanggal 16 November–2 Desember 2019 dengan metode Differenced Normalized Burn Ratio (dNBR). Estimasi deformasi vertikal dilakukan menggunakan pasangan citra Sentinel-1 SLC mode Interferometric Wide (IW) tanggal 17 Juni 2019 dan 2 Desember 2019 melalui metode Differential Interferometric Synthetic Aperture Radar (DInSAR). Validasi hasil klasifikasi dNBR dilakukan menggunakan data hotspot kumulatif NASA FIRMS periode 5 Juli–15 November 2019 dengan confidence >30% untuk sensor MODIS serta kategori Nominal dan High untuk sensor VIIRS melalui matriks konfusi (confusion matrix). Data curah hujan bulanan CHIRPS turut digunakan untuk mendukung interpretasi temporal kejadian kebakaran. Hubungan antara tingkat keparahan kebakaran dan deformasi vertikal dianalisis menggunakan overlay spasial, sedangkan perbedaan nilai deformasi antar kelas keparahan kebakaran diuji menggunakan uji Kruskal–Wallis pada tingkat kepercayaan 90%.

Hasil penelitian menunjukkan bahwa kelas Moderate-High Severity merupakan kelas keparahan kebakaran yang paling dominan dengan luas 281.323,98 ha (30,45?ri total luas area penelitian), diikuti kelas Low Severity seluas 270.692,82 ha (29,30?ri total luas area penelitian). Validasi menggunakan data hotspot menghasilkan user's accuracy sebesar 72,33%. Rata-rata deformasi vertikal pada kelas Unburned, Low Severity, dan Moderate-High Severity berturut-turut sebesar 0,216 ± 0,852 cm, -0,321 ± 0,912 cm, dan       -1,877 ± 0,925 cm. Hasil tersebut menunjukkan bahwa semakin tinggi tingkat keparahan kebakaran, semakin besar kecenderungan terjadinya amblesan lahan gambut. Uji Kruskal–Wallis menghasilkan nilai H sebesar 26,664 dengan p-value sebesar 1,621 × 10?? (<0>

Peatland fires cause the loss of organic material and induce vertical deformation in the form of land subsidence. Pulang Pisau Regency, Central Kalimantan Province, is one of Indonesia's peatland regions that experienced extensive fires during the 2019 dry season, which was intensified by the El Niño phenomenon. Although burned areas and land deformation have been widely investigated separately, information regarding the relationship between burn severity and peatland subsidence remains limited. Therefore, burned areas and burn severity were identified, vertical deformation following peatland fires was estimated, and the spatial relationship and statistical significance between burn severity and peatland subsidence in Pulang Pisau Regency in 2019 were analyzed.

Burn severity was assessed using Landsat 8 pre-fire imagery acquired between June 1 and July 4, 2019, and post-fire imagery acquired between November 16 and December 2, 2019, through the Differenced Normalized Burn Ratio (dNBR) method. Vertical deformation was estimated from a pair of Sentinel-1 Single Look Complex (SLC) images acquired on June 17 and December 2, 2019, using the Differential Interferometric Synthetic Aperture Radar (DInSAR) method. The dNBR classification was validated using cumulative NASA FIRMS hotspot data collected from July 5 to November 15, 2019, applying a confidence threshold of >30% for MODIS and the Nominal and High confidence categories for VIIRS through a confusion matrix. Monthly CHIRPS rainfall data were also utilized to support the temporal interpretation of fire occurrence. The relationship between burn severity and vertical deformation was evaluated through spatial overlay analysis, while differences in deformation values among burn severity classes were assessed using the Kruskal–Wallis test at a 90% confidence level.

The results showed that the Moderate-High Severity class was the dominant burn severity class, covering 281,323.98 ha (30.45% of the total study area), followed by the Low Severity class, which covered 270,692.82 ha (29.30% of the total study area). Validation using hotspot data yielded a user's accuracy of 72.33%. The mean vertical deformation values for the Unburned, Low Severity, and Moderate-High Severity classes were 0.216 ± 0.852 cm, -0.321 ± 0.912 cm, and -1.877 ± 0.925 cm, respectively. These findings indicate that higher burn severity is associated with a greater tendency for peatland subsidence. The Kruskal–Wallis test yielded an H statistic of 26.664 with a p-value of 1.621 × 10?? (<0>

Kata Kunci : gambut, kebakaran lahan, dNBR, DInSAR, land subsidence, Kabupaten Pulang Pisau/