Global Flood Mapper v2: Open-Access Flood Mapping and Exposure Assessment with Sentinel-1 SAR

We present Global Flood Mapper v2 (GFM v2), which adds flood depth estimation, on-demand GeoTIFF export, cloud-based impact assessment against high-resolution land cover and five global population datasets to quantify exposure uncertainty, and parameter-encoded URLs for reproducibility and sharing. Its predecessor, GFM v1, was already an open-access, globally operational web portal for rapid, analysis-ready flood mapping that runs entirely in the browser without coding, downloads, or data preprocessing; GFM v2 builds on this foundation without sacrificing that ease of use. Unlike fully-automatic monitoring services, which publish precomputed output from fixed, provider-set detection parameters and do not process every Sentinel-1 acquisition, GFM v2 gives users direct control over which acquisitions are processed and how: users can compare pre- and during-flood imagery, adjust detection thresholds and terrain masks to local conditions, and select any area and date, ensuring small-scale or localized events can always be mapped, regardless of whether an automated monitoring service happened to cover them. By lowering technical barriers without sacrificing user control, GFM v2 supports timely, evidence-based flood response and management.