Hierarchically nested river landform sequences. Part 1: Theory

Abstract

Past river classifications use incommensurate typologies at each spatial scale and do not capture the pivotal role of topographic variability at each scale in driving the morphodynamics responsible for evolving hierarchically nested fluvial landforms. This study developed a new way to create geomorphic classifications using metrics diagnostic of individual processes the same way at every spatial scale and spanning a wide range of scales. We tested the approach on flow convergence routing, a geomorphically and ecologically important process with different morphodynamic states of erosion, routing, and deposition depending on the structure of nondimensional topographic variability. Five nondimensional landform types with unique functionality represent this process at any flow; they are nozzle, wide bar, normal channel, constricted pool, and oversized. These landforms are then nested within themselves by considering their longitudinal sequencing at key flows representing geomorphically important stages. A data analysis framework was developed to answer questions about the stage‐dependent spatial structure of topographic variability. Nesting permutations constrain and reveal how flow convergence routing morphodynamics functions in any river the framework is applied to. The methodology may also be used with other physical and biological datasets to evaluate the extent to which the patterning in that data is influenced by flow convergence routing. Copyright © 2018 John Wiley & Sons, Ltd.

Hierarchically nested river landform sequences. Part 2: Bankfull channel morphodynamics governed by valley nesting structure

“…Data analysis methods (Table ) were explained in Pasternack et al . (). Each analysis was implemented using ArcGIS® 10.3 for geospatial processing and Microsoft Excel® for statistical analysis.…”

“…In Pasternack et al . (), we proposed a new, continuum‐based, scale‐independent approach to classifying landforms with respect to a single morphodynamic mechanism that can occur at many fluvial scales. The approach is amenable to signal processing analyses that enable the same typology to be employed over the same wide range of scales that the mechanism spans.…”

“…We chose the mechanism of flow convergence routing as the illustrative mechanism to focus on (see Pasternack et al . () for background literature, classification scheme, and data analysis methods).…”

“…In Pasternack et al . (), a new, scale‐independent, hierarchical river classification was developed that uses five landform types to map the domains of a single fluvial process – flow convergence routing – at each of three–five spatial scales. Given those methods, this study investigated the details of how flow convergence routing organizes nested landform sequences.…”

Three‐dimensional reconstruction of fluvial surface sedimentology and topography using personal mobile laser scanning

“…These technologies are enabling the acquisition of topographic data with unprecedented spatial resolution (Passalacqua et al, 2015). Such datasets have a variety of uses in geomorphology, including landform mapping and classification (Pasternack et al, 2018, Jones et al, 2007, Demarchi et al, 2016, Carbonneau et al, 2012, topographic change detection (Wheaton et al, 2010, Tamminga et al, 2015, surface grain size characterisation using point clouds derived from TLS (Brasington et al, 2012, Heritage and Milan, 2009, Hodge et al, 2009a and SfM photogrammetry (Pearson et al, 2017, Westoby et al, 2015, Vázquez-Tarrío et al, 2017, hydro-and morpho-dynamic modelling (Williams et al, 2016, Williams et al, 2013, Kasprak et al, 2018 and vegetation mapping (Manners et al, 2013, Brodu and Lague, 2012, Jalonen et al, 2014. Recently, a new generation of lightweight LiDAR sensors have emerged.…”