Predictions of steady state and transient landscape morphology using sediment‐flux‐dependent river incision models

Abstract

[1] Recent experimental and theoretical studies support the notion that bed load in mountain rivers can both enhance incision rates through wear and inhibit incision rates by covering the bed. These effects may play an important role in landscape evolution and, in particular, the response of river channels to tectonic or climatic perturbation. We use the channel-hillslope integrated landscape development (CHILD) numerical model with two different bedrock incision models that include the dual role of the sediment flux to explore the transient behavior of fluvial landscapes. Both models predict that steady state channel slopes increase in landscapes with higher rock uplift rates. However, the incision models predict different transient responses to an increase in uplift rate, and the behavior of each incision model depends on both the magnitude of change in uplift rate and the local drainage area. In some cases, the transient channel behavior is indistinguishable from that predicted for transport-limited alluvial rivers. In other cases, knickpoints form in some or all of the drainage network, as predicted by the detachmentlimited stream power model. In all cases the response in the lower parts of the network is highly dependent on the response in the upper parts of the network as well as the hillslopes. As the upper parts of the network send more sediment downstream, channel incision rates may rise or fall, and slopes in the lower parts of the channel may, in fact, decrease at times during the transient adjustment to an increase in rock uplift rate. In some cases, channel incision in the upper parts of the network ceases during the transient while the hillslopes adjust to the new uplift rate; drainage density may also change as a function of uplift rate. Our results suggest that if the sediment flux strongly controls bedrock incision rates, then (1) the transient fluvial response will take longer than predicted by the detachment-limited stream power model, (2) changes in channel slope may be much more complex than predicted by the detachment-limited stream power model, and (3) changes in the fluvial system will be closely tied to sediment delivery from the hillslopes. Importantly, our results outline quantitative differences in system behavior produced by competing models and provide a framework for identifying locations in natural systems where differences in channel morphology can be used to discern between competing fluvial erosion models.Citation: Gasparini, N. M., K. X. Whipple, and R. L. Bras (2007), Predictions of steady state and transient landscape morphology using sediment-flux-dependent river incision models,

Characteristics of steady state fluvial topography above fault‐bend folds

“…The sensitivity of sediment production on hillslopes is thus expected to make fluvial geomorphology even more sensitive to lateral advection than simulated in this paper, if one incorporates sediment-flux-dependent incision rules [Whipple and Tucker, 2002;Gasparini et al, 2006;Crosby et al, 2007;Gasparini et al, 2007]. One prediction of landscape evolution models with sediment-flux-dependent incision is the production of oversteepened reaches [Gasparini et al, 2006;Crosby et al, 2007].…”

The SPACE 1.0 model: a Landlab component for 2-D calculation of sediment transport, bedrock erosion, and landscape evolution

“…2). Assuming that increasing mean sediment thickness leads to higher proportions of bedrock covered by sediment and that sediment cover inhibits erosion (e.g., Beaumont et al, 1992;Whipple and Tucker, 2002;Sklar and Dietrich, 2004;Gasparini et al, 2006Gasparini et al, , 2007 Hobley et al, 2011), the volumetric erosion rate of bedrock per unit bed area may be written as…”

“…The major limitation of basic stream power and shear stress models is the lack of a description of how sediment influences channel bed erosion. A large number of sediment-flux-dependent incision models, in which the interaction of sediment flux with sediment transport capacity enhances or inhibits bedrock erosion, have been developed to fill this gap (e.g., Dietrich, 1998, 2004;Whipple and Tucker, 2002;Gasparini et al, 2006Gasparini et al, , 2007Turowski et al, 2007;Chatanantavet and Parker, 2009;Hobley et al, 2011). Sediment may act as "cover," inhibiting bedrock erosion, or as "tools," accelerating bedrock erosion (see review by Hobley et al, 2011).…”

Geomorphic indices of rivers and drainage in China’s Longmen Shan Fault zone and their implications for regional tectonic activity

“…Sediment flux has close relation to channel erosion (Gasparini et al, 2007). However, extensive research on sediment flux and orographic precipitation show that the systematic patterns of channel gradient in the study area are not the result of the variations in climate (Kirby & Whipple, 2003).…”

“…Neglecting hillslope processes, the evolution of a landscape is governed by the competition between rock uplift and fluvial erosion (Gasparini, Whipple, & Bras, 2007), as:…”