The Spatial Planning in Purworejo Regency-based Flood Hazard using Sentinel-1A Imagery

Abstract

Flood disasters in Indonesia increased by 23% over a period of 70 years. In Central Java Province, the incidence of floods has also experienced a significant increase, including flooding in Purworejo Regency. Floods in Purworejo Regency occur in almost every rainy season in the same location. In 2020 and 2021, floods hit the same 13 villages. The utilization of the Sentinel-1A Imagery technology can quickly and accurately visualize the distribution of locations where there are indications of flood inundation. This research aims to do rapid flood mapping for spatial planning. The method used in this research is the processing of Sentinel-1A imagery, flood mapping in Purworejo Regency, validation test of processed Saentinel-1A imagery, and flood analysis with the Purworejo Regency Spatial Planning. The Sentinel-1A data processing is in the form of a combination process between Composite RGB and the Change Detection and Thresholding (CDAT) method. Sentinel-1A imagery was taken at two different times, namely when there was a flood and when there was no flood. The Flood Map Processed by Saentinel-1A imagery will be verified and validated. The validity test results using the Kappa coefficient are 0.841, and the accuracy value is 94%. The Kappa coefficient value and accuracy show that the flooding results from the Saentinel-1A image processing are valid and accurate. The results of the analysis between spatial planning and flood inundation in Purworejo Regency are > 50% of the flooded areas in the form of paddy fields and plantations.