Sentinel-1 SAR Polarization Combinations for Flood Inundation Spatial Distribution Mapping (Case Study: South Kalimantan)

41.98% of disaster events occurred in 2021 in Indonesia were flood disasters. Rain of 2.08 billion m³ during the second week of January 2021 occurred in South Kalimantan, Indonesia, where the volume of rainwater was not proportional to the capacity of the Barito Watershed. It caused flooding in 11 cities/regencies. In the discourse of flood disaster mitigation, it is important to be able to map the flood inundation spatial distribution. Research with remote sensing methods, especially active remote sensing, which can penetrate clouds and free from weather disturbances can be an option in analysing flood inundation distribution. Sentinel-1 is one of the active remote sensing with Synthetic Aperture Radar (SAR) C-band imaging mission which is being widely used for flood disaster analysis. Generally, research on flooding is carried out using only VV or VH polarization. Only some researches use combination of both polarizations. Therefore, in this paper, combinations of those two polarizations are used in order to explore the use polarization combination in mapping the distribution of flood inundation, especially for case studies of flood disasters in South Kalimantan. However, in this study case, VV and VH polarization combination are not suitable in mapping flood inundation. VH polarization only showed best result in mapping flood inundation with overall accuracy of 89%, while VV and VH polarization combination resulted overall accuracy of 73%.