Large channel confluences influence geomorphic heterogeneity of a southeastern United States river

Abstract

[1] Detection of biological patterns in structurally complex rivers is difficult but essential in the management of imperiled species. On the basis of the network dynamics hypothesis (NDH), we predicted that tributaries exert a strong influence on main stem morphology, mediated by tributary sediment inputs. We predicted that the likelihood that a tributary will affect main stem geomorphology depends on the ratio of the tributary basin area to the main stem basin area (T BA :M BA ). Although the results of this study do not indicate that T BA :M BA is a useful predictor of the presence of shallow alluviumdominated confluences (i.e., shoals) in the Etowah River, in Georgia, alluvial shoals were closer to tributary mouths than were other shoal types, indicating an association with tributaries. Shoals near large tributary confluences also contained a larger proportion of gravel and cobble bed sediments and were wider than adjacent, downstream shoals. These confluence-associated shoals may be ecologically different in that aquatic macrophyte occurrence is higher in wide shoals with coarse sediments, and several state and federally listed darters (Percidae) are associated with shoals and these aquatic macrophytes. Recognizing confluence-associated shoals as unique shoal types may aid researchers in understanding the distribution patterns of these aquatic organisms.

The spatial heterogeneity of riverbed saturated permeability coefficient in the lower reaches of the Heihe River Basin, Northwest China

“…Over large spatial scales, riverbed texture and slope decrease, and channel width increases in a downstream direction (Vannote et al ., ). However, geomorphic variation in part could exist to change the properties of channel (Duncan et al ., ). In this study, the river was divided into East River and West River below LXS transect, which were further divided into more tributaries in the lowest reaches of the rivers (Figure ).…”

Review of Flow Hydrodynamics and Sediment Transport at Open Channel Confluences

“…Hence, the greatest sediment transport occurs around the edges of the scour-hole which is generally observed at the downstream corner of the confluence [63]. The lateral flow characteristics play a key role in controlling the grain size and sorting of bed material in the downstream direction of the confluence [13,[64][65][66][67][68][69].…”

Sediment transport at the river confluences: few observations from a sub-tropical plateau fringe river of eastern India

“…Study of Mueller (1972), Mesa and Mifflin (1986), Robinson et al (1995), Benda et al (2004b), Macnab et al (2006), and Sklar et al (2006), Ghosh (2016aGhosh ( , 2019a are some of the important exceptions that have paid attention to the confluence hydro-sediment dynamics viewed from the tributary catchment context. Besides, study of Richards (1980), Bruns et al (1984), Rhoads (1987), Ward and Stanford (1995), Montgomery (1999), Ferguson et al (2006), , and Duncan et al (2009) have highlighted confluences as the point of discontinuity in the hydrosediment continuum within a fluvial network. Apart from these, study of Best (1985Best ( , 1986Best ( , 1987Best ( , 1988, Biron et al (1993), Boyer et al (2006), Ghobadian and Bejestan (2007), Szupiany et al (2009), Ribeiro et al (2012), Martin-Vide et al (2015), and Nazari-Giglou et al (2016) are also important in this regard to explore the nature of hydro-sediment dynamics and related issues and explanations at the confluence hydro-dynamic zone.…”