Authors: Anzy Lee, Jose Castejon, Belize Lane, Colin Phillips – Utah State University
Presentation Type: Poster
Title: The invisible HAND: Assessing HAND across channel settings, terrain resolutions and flow stages
Abstract: Flood maps are essential for emergency response and urban development planning. The Height Above Nearest Drainage (HAND) method offers a low-complexity and straightforward terrain-based strategy for creating Flood Inundation Maps (FIMs). While the HAND approach has been successfully implemented for nationwide flood mapping across the CONUS region, the performance of HAND-FIM strongly depends on the digital elevation model (DEM) as well as the availability of bathymetric data. Moreover, the HAND method has been evaluated for rivers in a limited number of regions leaving its broad scale applicability questionable. Here we examine how the HAND-FIM performance changes with respect to channel setting, DEM resolution, and if it can be improved through the use of high-resolution terrain. To answer our question, we systematically assess how high-resolution terrain can be used to improve the HAND approach by investigating where current methods poorly estimate the underlying reach-average hydraulic geometry parameters (e.g., hydraulic radius, flow area) used to generate the synthetic rating curves (SRC). We utilize benchmarked 2D hydrodynamic models as a means to establish reach and cross section scale rating curves in order to calibrate and validate the HAND SRC. Our goal is to identify high and poor performing combinations of the underlying hydraulic metrics to guide the calculation of HAND for various channel settings and DEM resolutions.