Cloud-Powered Flood Mapping and Impact Assessment: Leveraging Sentinel-1 SAR Imagery for Thailand's Disaster Response

Abstract

This research presents a cloud-based application approach to flood mapping and impact assessment in Thailand, integrating Sentinel-1 Synthetic Aperture Radar (SAR) imagery with Google Earth Engine's computational capabilities. The study addresses the critical challenge of automated flood monitoring in Thailand's increasingly flood-prone landscape, where climate change and urbanization intensify disaster risks. The methodology combines multiple resolution geospatial datasets through a sophisticated processing framework that integrates dual-polarization SAR data analysis, advanced speckle reduction techniques, and topographic constraints. The system employs a robust change detection algorithm with a calibrated threshold value of 1.30, enhanced by permanent water body masking and connectivity analysis. The methodology was validated through case studies in five geographically diverse provinces: Chiang Rai, Phra Nakhon Si Ayutthaya, Nong Khai, Kanchanaburi, and Pattani. For instance, the Chiang Rai case study revealed 19,788 square kilometers of flooded area, impacting 6,392 residents and 16,795 buildings. The analysis highlighted differential vulnerability patterns, with agricultural areas experiencing a higher impact (5.41%) compared to urban zones (1.23%). This case study achieved an overall accuracy of 95.90% and a kappa coefficient of 0.92. Across all provinces, the system demonstrated exceptional performance with an average accuracy of 94.53% and an average kappa coefficient of 0.89. The cloud-based architecture facilitates efficient processing of large-scale datasets while maintaining high analytical precision. This capability makes the system an invaluable tool for emergency response and resource allocation. By providing timely and accurate flood metrics through an interactive web-based platform, this research significantly advances Thailand's flood monitoring capabilities, providing decision-makers with timely, accurate information for enhanced disaster management and response planning.