2. Inundation Mapping Quick Facts
Inundation Mapping is currently configured to perform processing at a spatial resolution of 10m. The long-term plan includes a higher-resolution (LiDAR) configuration.
Inundation Mapping performs its processing at the HUC8 scale. All posted Inundation Mapping outputs and model evaluation metrics are generated at the HUC8 scale. HAND and SRC outputs are in meters.
The GMS configuration derives Level Path Branches via an algorithm that starts at the highest stream order, concatenating back to the 3, and calling that collection a branch. Figure 1 shows the Generalized Main Stem (GMS) configuration schematic. A detailed explanation from the authors can be found here. The GMS selection routine takes place in the file derive_level_paths.py.
Figure 1: Generalized Main Stem (GMS) Schematic.
Branch Zero is created alongside GMS and can be used to supplement the output of GMS (Figure 2).
Figure 2: Visualization of the change in coverage between GMS and Branch Zero.
Inundation Mapping data sources include the NHDPlus HR, the National Water Model (NWM), the Advanced Hydrologic Prediction Service (AHPS), the National Levee Database (NLD), the USGS Watershed Boundary Dataset (WBD), and other ancillary datasets.
See Input Data Dictionary for more information.
Generally, the Inundation Mapping HAND is a "high-flow" model, meaning it performs better at higher flows than at lower flows. Two primary reasons for this behavior are 1) the lack of represented bathymetry in the 10m DEM (HAND underestimates in-channel conveyance area) and 2) the Manning’s roughness values in the Inundation Mapping HAND model have been predominantly optimized for model skill at high magnitude flood conditions (i.e. 100yr+ flows).
The Inundation Mapping team has developed automated evaluation software to measure FIM performance in multiple flow scenarios. This software is used to ensure that enhancements and bug fixes improve skill broadly across our national testing domain, and to protect against regressions.
See Evaluating HAND Performance for more information.
The Inundation Mapping project adheres to Semantic Versioning. Please refer to the CHANGELOG for details on the latest changes. If downloading this software, we recommend getting the latest official release.
Please refer to the Inundation Mapping README for details on getting involved.