Authors: Yixian Chen – The University of Alabama
Title: Improved River Slope Datasets for the United States Operational Flood Inundation Mapping Hydrofabic and Next Generation Water Resources Modeling Hydrofabric
Presentation Type: Poster
Abstract: The NOAA OWP operational Flood Inundation Mapping (FIM) forecasting framework uses the NHDPlusHR DEM to calculate slope as Manning’s equation parameter for compiling the Synthetic Rating Curves (SRC). The SRCs translate the National Water Model streamflow forecasts into stage and inundation extent at river reach scale nationwide using the Height Above Nearest Drainage approach (referred to as OWP HAND-FIM) to warn communities of potential floods. River slope is asserted to be a major source of uncertainty there. The recently developed global ICESat-2 River Surface Slope (IRIS) dataset, known for its accuracy, holds potential for improvements for this. We developed a spatial joining approach to align the reaches between OWP HAND-FIM Hydrofabric (FIM HF) and IRIS, addressing differences in reach flowline sources. This created the CONtiguous United States (CONUS) FIM HF IRIS dataset, integrating IRIS river slopes for 117,357 spatially corresponding FIM HF main-stream reaches. Using a common attribute, IRIS data were transferred from FIM HF IRIS to the CONUS Next Generation Water Resources Modeling Hydrofabric (NextGen HF), creating the NextGen HF IRIS dataset. When applied to OWP HAND-FIM, FIM HF IRIS improved FIM accuracy (CSI) by an average of 31% and 9% respectively over FIM HF slopes and NextGen HF slopes. By referencing a common attribute, the latest SWOT vector data, sharing the same flowlines as IRIS, can be used by OWP HAND-FIM and NextGen via the two resulting datasets.