Flood inundation during the event

For a buyer-selected area of interest and time range, GFM supplies 20 m Sentinel-1-derived Observed Flood Extent classes with product sensing time and GFM product version, showing where and when model-assisted satellite classification indicates flooding; it does not measure flood depth or establish ground-reported causation.

Open files provide NWS-documented Flood and Flash Flood events with begin/end times, event/episode identity, flood cause, and linked location points. NWS guidance uses reference points to outline affected areas; release and modification/certification dates pin the record. This is reported flood-occurrence evidence, not measured or satellite-derived inundation geometry or depth.

USGS public STN services retrieve event-linked surveyed high-water marks by event, site, filter, or location. Each mark identifies point location, event, flag/survey dates, elevation or height above ground, vertical datum, and quality class; the event resource supplies start/end dates. This is Strong observed point evidence of where floodwater reached, not a continuous footprint.

NOAA operational NWM terrain-routing NetCDF grids provide modelled ponded-water depth in mm at 250 m for CONUS/southern Alaska and 100 m for Hawaii/Puerto Rico/USVI. Configuration, initialization, valid time, release, and code version pin the result. Occurrence use is restricted to analysis-and-assimilation files; forecasts are prospective, and no mode is direct observation or building-specific depth.

Versioned public NWM retrospective files provide three-hourly geospatial RTOUT ponded-water depth for historical valid times. Retain archive release, model configuration, initialization/output-valid times, and code version, and characterize the result as simulated ponding without stream-gauge assimilation rather than direct observed inundation.