FIMserv v.1.0: A tool for streamlining Flood Inundation Mapping (FIM) using the United States operational hydrological forecasting framework

In the United States, the National Oceanic and Atmospheric Administration-Office of Water Prediction (NOAA-OWP) utilizes the National Water Model (NWM) for operational hydrological forecasting. Its Flood Inundation Mapping (FIM) framework translates NWM discharge to inundation extent using the Height Above the Nearest Drainage (HAND) approach. The simplicity of the OWP HAND-FIM framework enables rapid, large-scale FIM predictions across the U.S., fostering a growing user and developer community beyond NOAA. In this paper, we introduce “FIM as a Service (FIMserv)”, an open-source toolset that streamlines OWP HAND-FIM predictions with enhanced functionalities: (1) FIM generation from retrospective and forecasted NWM discharge, (2) Simultaneous simulations of multiple watersheds for various flood events, (3) FIM from Group on Earth Observations Global Water Sustainability (GeoGLOWS) discharge, (4) evaluation of NWM and GeoGLOWS discharge against USGS observations. FIMserv operates as a standalone notebook on local/cloud systems and as a Community Resource within the CIROH cloud cyberinfrastructure.