Utilization of Sentinel 1 SAR for Flood Mapping in North Konawe Regency, Southeast Sulawesi Province, Indonesia

Abstract

Abstract Flood disaster is one of the natural disasters caused by the high intensity of rainfalls which causes rapid rise in stream or river. This is mostly the case in tropical area, such as Indonesia. Konawe Utara regency is one of the regencies in Southeast Sulawesi that recently experienced flash floods in 2019. As a result, the flood caused significant environmental and economic losses and damaged several public infrastructures. This study uses SAR Sentinel 1 imagery to rapid map of the flood event. The method used in this study is the Normalized Difference Sigma-Naught Index (NDSI). This method can identify the comparison of the Backscatter value from the image before and during the flood. Then, extracting the flood information using vectorization tools and calculating geometry features were conducted in the open-source QGIS software. The results of this study show that the flood occurred in some important areas of North Konawe Regency and inundated six (6) districts namely Wiwirano district, Oheo district, Molawe district, Langgikima district, Asera district, Andowia district. Among those areas, Oheo district is the most affected area of flooding with 1836.88 hectares (4,1 % total area of Oheo district). This area included 186.24 hectares of settlement area and bussiness, 664.39 hectares of agriculture area. The rest area of inundation consisted of forests, shrubs and bare lands. More importantly, the flood also inundated the capital city of North Konawe regency located in Asera district with affected area of 25.76 hectares. This flood has paralyzed economic activities and local government administration. The result of this study shows the potential Sentinel 1 SAR in assisting rapid assessment during disaster period and will help local government in considering mitigation approaches.