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RAS2FIM is a software repository designed to generate Flood Inundation Mapping (FIM) geospatial grids from one-dimensional Hydrologic Engineering Center - River Analysis System (HEC-RAS) flood simulation models.
RAS2FIM was created using open-source tools and is written in Python. It is maintained by a small team of at the NOAA National Water Center, but all are welcome to collaborate. RAS2FIM combines the uses of programmatic geospatial tools with the HEC-RAS API to create flood inundation raster stacks keyed to the National Water Model hydrofabric. This workflow was created so that these grids can be referenced to historical, current and forecasted stream flow rates for flood mapping services.
The repository is currently undergoing a significant documentation phase. Please refer to the CHANGELOG for the latest updates. Check out the RAS2FIM Quick Facts or the Known Issues and Opportunities for Improvement pages. Check out the README for information on getting started and to see scientific credits and references.
From the user supplied HEC-RAS models, RAS2FIM utilizes HEC-RAS in a one-dimensional steady-state hydraulic analysis to determine a 'reach averaged' depth. A reach averaged depth is determined for multiple flow rates which are used to create a 'synthetic rating curve'. For each reach in the National Water Model where a provided HEC-RAS model conflates, a synthetic rating curve is stored to determine what flood map should be used at a given flow rate.
At even average depth intervals, flood inundation depth grids are computed against user-supplied terrain data.
Using HEC-RAS Mapper in an automated fashion, multiple flood depth grids are simulated for a subject National Water Model reach (feature-id). These grids are converted to an Interagency Flood Risk Management (InFRM) compliant structure.
For RAS2FIM, a user will need to supply geospatial one-dimensional HEC-RAS models for rivers. This can be a single river or several models similar to those published as Base Level Engineering.
All models must be:
- On the same geographic projection (example: EPSG:2277)
- Be contained within the same HUC-8 watershed (example: 12090301)
In addition to the HEC-RAS models, there are a few additional input datasets to execute RAS2FIM, listed below. The required input datasets are in a requestor-pays Amazon Web Service s3 bucket. AWS CLI tools will be necessary to obtain.
Location:
s3://noaa-nws-owp-fim/ras2fim/inputs/X-National_Datasets
Required National Datasets Files:
-
nwm_flows.gpkg: NWM v2.1 flowlines, converted to geopackage. -
WBD_National.gpkg: Watershed Boundary Dataset, converted to a geopackage. -
nwm_wbd_lookup.nc: NetCDF file that contains a lookup between the Watershed Boundary Dataset and National Water Model flowlines.
The other required input dataset is a terrain surface (Digital Elevation Model, DEM) file which will be used for the creation of the flood depth grids. Note that this surface is not used to alter or modify the supplied HEC-RAS models. It is only used for flood depth delineation. Spatially, these surface data can be in any coordinate reference system (CRS) and the program will reprojection them into the CRS of the provided HEC-RAS models. The user supplied terrain can be either a GeoTIFF or Virtual Raster (VRT).
Detail regarding the core function of the scripts in RAS2FIM can be found here.
Development initially started in 2019 with the Center for Water and the Environment of the University of Texas by Andy Carter under the guidance of Dr. David Maidment. In 2021, the code base was refined through the NOAA National Water Center by the Flood Inundation Mapping team. The first public release was 7 Nov 2021.