Flood mapping through an integrated interpretation of SAR imagery, terrain indices, and social media evidence

Floods are among the most destructive water-related disasters, causing severe damage to infrastructure, agriculture, human lives, and regional economies. Analyzing past flood events is therefore essential for improving disaster management and risk mitigation strategies. This study presents an integrated interpretation framework combining Synthetic Aperture Radar (SAR) remote sensing, GIS-based analysis, and Volunteered Geographic Information (VGI) to delineate flood inundation areas in data-scarce environments.The proposed approach was applied to the flood event of ۲۸ July ۲۰۲۲ in Firozkoh County, Tehran Province, Iran. Sentinel-۱ SAR images acquired before and after the event were processed to detect inundated areas, resulting in the identification of ۱,۳۶۹.۲۹ hectares of flooded land, corresponding to approximately ۰.۶% of the county’s total area (۲۳۸,۴۷۰ hectares). A kernel density–based heat map was generated to highlight spatial concentrations of flood impacts.Due to the lack of in situ ground truth data, validation was conducted using terrain-based flood susceptibility indicators. The Topographic Wetness Index (TWI) and Stream Power Index (SPI) were computed and the relationship between the TWI-SPI index and SAR-derived outputs was assessed using Spearman’s rank correlation coefficient (ρ = ۰.۵۳), indicating a moderate positive correlation. In addition, social media data from Twitter were analyzed as qualitative social corroboration to provide contextual evidence of flood occurrence and affected locations.The results demonstrate that integrating SAR imagery with terrain indices and VGI can support flood mapping and situational awareness in regions where conventional ground-based data are unavailable. The proposed framework highlights the complementary value of remote sensing, GIS, and volunteered data for post-event flood assessment and disaster management.

کلیدواژه ها:

Flood mapping ، Disaster management ، SAR ، Sentinel-۱ ، GIS ، VGI