Revealing the natural complexity of fluvial morphology through 2D hydrodynamic delineation of river landforms

• Published in: Geomorphology (Amsterdam, Netherlands) Vol. 210; pp. 14 - 22
• Main Authors: Wyrick, J.R., Senter, A.E., Pasternack, G.B.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2014; Elsevier
• Subjects: 2D modeling; Base flow; Channels; Computational fluid dynamics; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fluid flow; Fluvial geomorphology; Fluvial landforms; Freshwater; Geomorphology, landform evolution; Hydrology; Hydrology. Hydrogeology; Landforms; Marine and continental quaternary; Morphological units; Raster; Surface water; Surficial geology; Two dimensional; 2D modeling; Fluvial landforms; Fluvial geomorphology; Morphological units; hydraulics; fluvial sedimentation; imagery; discharge; two-dimensional models; rivers; models; maps; morphology; Decision making; hydrodynamics; velocity; classification; surface water; landforms; fluvial environment; depth; channels; alteration; errors; landform evolution; theory
• ISSN: 0169-555X; 1872-695X
• DOI: 10.1016/j.geomorph.2013.12.013

Fluvial landforms at the morphological-unit scale (~1–10 channel widths) are typically delineated and mapped either by breaking up the one-dimensional longitudinal profile with no accounting of lateral variations or by manually classifying surface water patterns and two-dimensional areal extents in situ or with aerial imagery. Mapping errors arise from user subjectivity, varying surface water patterns when the same area is observed at different discharges and viewpoints, and difficulty in creating a complete map with no gaps or overlaps in delineated polygons. This study presents a new theory for delineating and mapping channel landforms at the morphological-unit scale that eliminates in-field subjective decision making, adds full transparency for map users, and enables future systemic alterations without having to remap in the field. Delineation is accomplished through a few basic steps. First, near-census topographic and bathymetric data are used in a two-dimensional hydrodynamic model to create meter-scale depth and velocity rasters for a representative base flow. Second, expert judgment and local knowledge determine the number and nomenclature of landform types as well as the range of base flow depth and velocity over each type. This step does require subjectivity, but it is transparent and adjustable at any time. Third, the hydraulic landform classification is applied to hydraulic rasters to quickly, completely, and objectively map the planform pattern of laterally explicit landforms. Application of this theory will reveal the true natural complexity, yet systematic organization, of channel morphology. •A new theory for more objectively delineating and mapping river landforms•Method is transparent, repeatable, and automatic for any study site and scale.•Method eliminates field subjectivity and creates contiguous polygon map.•Two example maps highlight complexity of a channel's morphologic structure.