Transport and storage of bed material in a gravel‐bed channel during episodes of aggradation and degradation: a field and flume study

Abstract

The dynamics of sediment transport capacity in gravel-bed rivers is critical to understanding the formation and preservation of fluvial landforms and formulating sediment-routing models in drainage systems. We examine transport-storage relations during cycles of aggradation and degradation by augmenting observations of three events of channel aggradation and degradation in Cuneo Creek, a steep (3%) gravel-bed channel in northern California, with measurements from a series of flume runs modeling those events. An armored, single-thread channel was formed before feed rates were increased in each aggradation run. Output rates increased as the channel became finer and later widened, steepened, and braided. After feed rates were cut, output rates remained high or increased in early stages of degradation as the incising channel remained fine-grained, and later decreased as armoring intensified. If equilibrium was not reached before sediment feed rate was cut, then a rapid transition from a braided channel to a single-thread channel caused output rates for a given storage volume to be higher during degradation than during aggradation. Variations in channel morphology, and surface bed texture during runs that modeled the three cycles of aggradation and degradation were similar to those observed in Cuneo Creek and provide confidence in interpretations of the history of change: Cuneo Creek aggraded rapidly as it widened, shallowed, and braided, then degraded rapidly before armoring stabilized the channel. Such morphology-driven changes in transport capacity may explain the formation of flood terraces in proximal channels. Transport-storage relations can be expected to vary between aggradation and degradation and be influenced by channel conditions at the onset of changes in sediment supply. Published in 2011. This article is a US Government work and is in the public domain in the USA.

Large-scale dam removal on the Elwha River, Washington, USA: River channel and floodplain geomorphic change

“…Instead, comparison with theoretical and flume-based observations of Lisle et al (2001) indicated that the sediment wave demonstrated dispersive properties. The patterns that we observed-pool filling, bed aggradation followed by degradation and incision, temporarily increased braiding, and bed sediment fining-are all consistent with sediment-wave dispersion (e.g., Lisle et al, 2001;Cui and Parker, 2005;Lisle, 2008;Pryor et al, 2011). The dominantly dispersive wave behavior (cf.…”

“…Well-controlled laboratory and flume investigations provide valuable steps toward understanding how sediment-supply pulses affect processes such as stream-channel evolution, bar formation, and avulsion (e.g., Lisle et al, 1997;Braudrick et al, 2009;Madej et al, 2009;Tal and Paola, 2010;Pryor et al, 2011); and modeling studies allow simulated manipulation of landscapes over a range of scales (e.g., Cui and Parker, 2005;Jerolmack and Paola, 2007;Karssenberg and Bridge, 2008;Wang et al, 2011). However, opportunities to study landscape response to major sediment influx over large field scales are much rarer and usually are not anticipated in advance (e.g., dam failure, volcanic eruptions, landslides, or debris flows; Meyer and Martinson, 1989;Montgomery et al, 1999;Hoffman and Gabet, 2007;Casalbore et al, 2011;Gran, 2012;Guthrie et al, 2012;Pierson and Major, 2014;Tullos and Wang, 2014).…”

Does variable channel morphology lead to dynamic salmon habitat?

“…Overall, the positive relationships shown in some series in Figure 11 also lend support to the theory of morphology-driven variability in habitat. While results from a single catchment are presented, the episodic sediment supply regime and characteristics of channel response in Carnation Creek are not unique, and have been widely observed in other channel networks with varying degrees of hillslope-channel coupling (Madej and Ozaki, 1996;Sutherland et al, 2002;Hoffman and Gabet, 2007;Pryor et al, 2011). For example, Frissell et al (1986) states how landslides might impact channels at the reach-scale through altering sediment storage units, while Montgomery (1999) attempts to connect geomorphic process domains to disruption of the River Continuum Concept (Vannote et al, 1980).…”

“…Process. Changes in sediment loads from debris flows are common in mountain landscapes, and have also been shown to influence bar and pool characteristics downstream (Madej and Ozaki, 1996;Hoffman and Gabet, 2007;Pryor et al, 2011). Previous research highlights the connection between channel morphology and topography and larger-scale sediment supply dynamics, such as those imposed by channel-hillslope coupling (Hoffman and Gabet, 2007;Hassan et al, 2019).…”

“…Landforms 45, 295-311 (2020) MacVicar and Roy, 2007;Caamano et al, 2012). Beschta, 1983;Pryor et al, 2011;Buffington, 2012), but this variability is not often explicitly considered when modeling aquatic habitat for management purposes, nor is it clear what effect morphology has on habitat-regulating hydraulics at different flow levels through time. For a given valley gradient, a range of channel morphologies is possible as a function of sediment supply and calibre (Montgomery, 1997;Church, 2006;Hassan et al, 2008).…”