Authors: Jose Castejon, Anzy Lee, Belize Lane, Colin Phillips – Utah State University
Presentation Type: Poster and Lightning Talk
Title: Can a single rating curve really capture the complexity of a river reach? Yes.
Abstract: Advancing our ability to predict flood inundation extent is crucial for effective planning and emergency response, as floods are becoming more frequent and severe and continue to threaten human life and property. In the United States, efforts to estimate flood extents have been made through the National Water Model (NWM) utilizing the Height Above Nearest Drainage (HAND) approach. HAND uses forecasted values of discharge from the NWM and Synthetic Rating Curves (SRCs) to map potential flood inundation. SRCs are currently constructed using reach-average geometric and hydraulic channel attributes extracted from a 10-m resolution Digital Elevation Model (DEM). However, the increasing availability of high-resolution topography provides an opportunity to explore ways to integrate the full 3D channel variability into the HAND approach and improve flood prediction and operations efforts. In this study, calibrated 2D hydrodynamic models are used to create families of SRCs for 3 northern-California reaches with high-resolution bathymetric topography. The SRC families represent sets of stage-discharge rating curves for each cross section along the reach. We utilize the inundated areas produced with the benchmarked 2D model to evaluate the prediction capabilities of each rating curve within the SRC families. Results from this analysis demonstrate that a single rating curve can accurately reproduce reach-scale flood inundation, which percentile of the SRC families provides the best prediction and how the HAND SRC can be adjusted to match the best prediction SRC. The use of a single SRC across a reach will support the NWM to continue to operate at low computational cost through the HAND approach but with a more robust flood inundation prediction capacity.