Extreme Coastal Flood Inundation Mapping Based on Sentinel 1 Using Google Earth Engine

Abstract

Coastal flooding frequently occurs along the Northern Coast of Java due to the continuous land subsidence and sea level rise. On May 23rd, 2022, an extreme tidal flood happened and impacted a wide area around the central part of the Northern Coast of Java, with reports indicating that the inundated area was larger than that of typical flood events. Although several researchers have conducted local inundation mapping in various districts, comprehensive flood mapping of this event over a larger area has not yet been undertaken. Such study would benefit for hydraulic flood models. Therefore, this study aimed to map the coastal flood extent around the central part of the Northern Coast of Java using Sentinel-1 imagery data processed through the Google Earth Engine (GEE). The delineated inundation at several points was then compared with field observations from a previous study. The analysis suggests that Sentinel-1 is generally capable of estimating flood extent, although additional measures are necessary for mapping in densely populated urban areas. The findings indicate that the area inundated by the May 2022 flood was at least 5,562 hectares larger compared to the flooding in April 2022.