Evaluating the performance of topobathymetric LiDAR to support multi‐dimensional flow modelling in a gravel‐bed mountain stream

Abstract

Stream biophysical processes are commonly studied using multi‐dimensional numerical modelling that quantifies flow hydraulics from which parameters such as habitat suitability, stream carrying capacity, and bed mobility are derived. These analyses would benefit from accurate high‐resolution stream bathymetries spanning tens of kilometres of channel, especially in small streams or where navigation is difficult. Traditional ground‐based survey methods are limited by survey time, dense vegetation and stream access, and are usually only feasible for short reaches. Conversely, airborne topobathymetric LiDAR surveys may overcome these limitations, although limited research is available on how errors in LiDAR‐derived digital elevation models (DEMs) might propagate through flow models. This study investigated the performance of LiDAR‐derived topobathymetry in support of multi‐dimensional flow modelling and ecohydraulics calculations in two gravel‐bedded reaches (approximately 200 m long), one morphologically complex and one morphologically simple, and at the segment scale (32 km‐long stream segment) along a 15 m‐wide river in central Idaho, USA. We compared metre and sub‐metre‐resolution DEMs generated from RTK‐GPS ground and Experimental Advanced Airborne Research LiDAR‐B (EAARL‐B) surveys and water depths, velocities, shear stresses, habitat suitability, and bed mobility modelled with two‐dimensional (2D) hydraulic models supported by LiDAR and ground‐surveyed DEMs. Residual statistics, bias (B), and standard deviation (SD) of the residuals between depth and velocity predicted from the model supported by LiDAR and ground‐survey topobathymetries were up to −0.04 (B) and 0.09 m (SD) for depth and −0.09 (B) and 0.20 m s−1 (SD) for velocity. The accuracy (B = 0.05 m), precision (SD = 0.09 m), and point density (1 point m−2) of the LiDAR topobathymetric survey (regardless of reach complexity) were sufficient to support 2D hydrodynamic modelling and derivative stream habitat and process analyses, because these statistics were comparable to those of model calibration with B = 0 m and SD = 0.04 m for water surface elevation and B = 0.05 m s−1 and SD = 0.22 m s−1 for velocity in our investigation. © 2020 John Wiley & Sons, Ltd.

Field evaluation of a compact, polarizing topo‐bathymetric lidar across a range of river conditions

“…High-resolution topographic and bathymetric surveys of rivers afford advantages for geomorphic change detection, habitat assessment, and flow modeling (Wheaton et al, 2013;Tonina et al, 2020). Provided the river can be navigated safely, multibeam echo sounders (MBES) function as efficient acoustic workhorses for hydrographers, as they are designed to acquire bathymetry along swaths that are at least several times the water depth.…”

“…A technology with potential to address issues associated with both shallow water mapping and the safety issues inherent to streamgaging is airborne lidar bathymetry (ALB). Over the past two decades, ALB systems initially designed for marine and coastal environments (Guenther, Cunningham, LaRoque, & Reid, 2000;Nayegandhi, Brock, & Wright, 2009) have been used for surveying inland waterways, specifically river channels (Hilldale & Raff, 2008;Kinzel, Legleiter, & Nelson, 2013;Kinzel, Wright, Nelson, & Burman, 2007;Legleiter et al, 2016;Mandlburger, Pfennigbauer, Schwarz, Flöry, & Nussbaumer, 2020;Mandlburger, Pfennigbauer, Wieser, Riegl, & Pfeifer, 2016;McKean et al, 2009;Saylam, Hupp, Andrews, Averett, & Knudby, 2018;Tonina et al, 2020). Manufacturers have produced bathymetric lidars that vary in system design, power, and performance, but mostly employ a 532 nm (green wavelength) waterpenetrating laser.…”

Climate Change Shrinks and Fragments Salmon Habitats in a Snow‐Dependent Region

“…The uncertainty associated with the LiDAR's vertical elevation measurements has a standard deviation of 0.1 m, which has a limited impact on flow hydraulic predictions for ecohydraulics applications, for example, 0.06 standard deviation of cell suitability index and less than 0.01 m error on water surface elevations (Tonina et al, 2020).…”

Aerofotogrametria Digital como Ferramenta Integrativa para Geração de Modelos Digitais Topobatimétricos de Reservatórios D’água

“…Um MDTB nada mais é do que a representação digital contínua de uma superfície única resultante da combinação da topografia emersa e a topografia submersa (Danielson et al 2016;National Oceanic and Atmospheric Administration 2007), de determinado reservatório (Erena et al 2019), curso d'água (Dietrich 2017;Javernick, Brasington & Caruso 2014) ou ambiente costeiro (Danielson et al 2016). A necessidade de que o MDTB apresente alta resolução espacial e precisão posicional adequada é compreendida ao entender que dele depende a performance de modelos numéricos multidimensionais e hidrodinâmicos utilizados, entre outros razões, para a definição do balanço hídrico do reservatório (Lane et al 2010;Tonina et al 2018;Tonina et al 2020).…”