Here we detail how Curve2Flood estimates a flood inundation map.

First, let's talk inputs.

Curve2Flood Flood Inundation Map Inputs

VDT Database or VDT Curvefile

Curve2Flood currently accepts using the Automated Rating Curve (ARC) tools VDT database or the VDT Curvefile.

These files contain pre-computed hydraulic outputs that provide Curve2Flood a means to convert streamflow or discharge into water depth and top-width.

These inputs are supplied to Curve2Flood by providing the 'Print_VDT_Database' and 'Print_Curve_File' arguments in your Curve2Flood input file. These arguments are the path to the VDT Database and Curvefile.

Streamflow

Curve2Flood requires the 'COMID_Flow_File' argument in its input file to simulate a flood inundation map. This points to a comma-separated value (CSV) file containing the streamflow for the stream reaches in your VDT Database and Curvefile.

Curve2Flood requires at least one streamflow column in this file but can accept multiple streamflows. Curve2Flood will build a probabilistic flood inundation map based upon the number of streamflows provided and the number of times each cell in the output flood inundation map is flooded.

Here is what an example 'COMID_Flow_File' looks like:

DEM/Topobathymetric Surface

Here we can provide Curve2Flood either the original DEM we used when running ARC or the DEM that has been processed by Curve2Flood.

The argument 'DEM_File' is required in the Curve2Flood input file and points Curve2Flood to the path where the DEM file is stored.

This is terrain that Curve2Flood will use to perform its flood inundation mapping.

Land Cover Dataset (Optional)

We can optionally provide Curve2Flood a path to a land use raster that has the same grid as our input DEM file.

The argument 'LU_Raster_SameRes' points Curve2Flood to this *.tif file input.

Curve2Flood will add all land use raster cells classified as water to our output flood inundation map.

The argument 'LAND_WaterValue' will provide Curve2Flood the pixel value in the 'LU_Raster_SameRes' raster that corresponds to water.

Flood Inundation Mapping Process

Curve2Flood will query the VDT Database (default) or the Curvefile in order to determine the appropriate depth and top-width to match with the input streamflow.

The these top-width and depth values are used to estimate flood inundation. The depth and top-width assigned to each stream cell in the modeled area uses these values and inverse distance weighting to calculate water surface elevations. Water surface elevations at a raster cell that are greater than the elevation of the DEM at that cell are deemed to flooded by Curve2Flood.

Optionally providing Curve2Flood the 'StrmShp_File' input in the Curve2Flood input file will allow Curve2Flood to filter any isolated and erroneous flood inundation estimates that are not connected to the original flowline shapefile from which the streamflow estimate originate. The 'StrmShp_File' input is a path to the polyline stream shapefile that the hydrologic modeling used to estimate streamflow.

The 'OutFLD' argument specifies where the output flood inundation raster will be stored. the 'OutFLD' raster will contain raster cell values between 0 and 100 that correspond to the percentage of streamflows that inundated that raster cell. A polygon geopackage of the same name will also be output by Curve2Flood.

Follum et al. (2022) provides a detailed overview of the process.

References

Follum, M. L., Vera, R., Tavakoly, A. A., & Gutenson, J. L. (2020). Improved accuracy and efficiency of flood inundation mapping of low- , medium- , and high-flow events using the AutoRoute model. Natural Hazards and Earth System Sciences, 20(2), 625–641. https://doi.org/10.5194/nhess-20-625-2020