Continental Scale Assessment of Variation in Floodplain Roughness with Vegetation and Flow Characteristics

Abstract

Quantifying floodplain flow resistance is critical to multiple river management objectives, but characterization of how floodplain vegetation dissipates flow energy lacks comprehensive analysis. By utilizing over 3.4 million discharge measurements, in conjunction with vegetation measurements from NASA’s Global Ecosystem Dynamics Investigation (GEDI), this study characterizes floodplain roughness and its determinates across the continental United States. Estimated values of the floodplain roughness coefficient, Manning’s n, are provided based on its variation with vegetation aboveground biomass and canopy height for different landscapes classes. Results show flow resistance in floodplains decreasing as flow velocity increases but increasing with the fraction of vegetation inundated. A new function is proposed for predicting n based of vegetation biomass, inundation fraction, and flow velocity (RMSE = 0.024, r2 = 0.74). This analysis provides evidence of key hydraulic patterns of energy dissipation in floodplains, and integration of the proposed function into flood and habitat models may reduce uncertainty.

Continental Scale Assessment of Variation in Floodplain Roughness With Vegetation and Flow Characteristics

“…After data processing and quality control, a total of 4,927 estimates of floodplain Manning's n were calculated successfully at 804 sites, based on the analysis of 3,379,166 total measurements obtained from 31,142 unique gauge sites (Barinas et al., 2023). Included with this data set of generated n values (see data set in Supporting Information ) are all the necessary variables measured by the USGS that were used when inverting Manning's equation to solve for n : measured discharge ( Q ), width ( w ), depth ( z ) obtained from USGS field measurements, and friction slope ( S ) from the NHD data sets.…”

“…The scripts to reproduce the data set, figures and tables in this study are openly available at Barinas et al. (2023) under a Creative Commons Attribution License format (free registration required).…”