Wave train model for knickpoint migration

Abstract

International audienceRivers respond to a drop in their base level by incising the topography. The upstream propagation of an incision, as usually depicted by a knickpoint migration, is thought to depend on several parameters such as the drainage area, lithology, and the amplitude of the base level drop. We first investigate the case of the Messinian Salinity Crisis that was characterized by the extreme base level fall (1500 m) of the Mediterranean Sea at the end of the Miocene. The response of drainage areas of three orders of magnitude (103 to 106 km2) highlights the dominant role of the drainage area (with a square root relationship) in controlling the knickpoint migration after a base level fall. A compilation of mean rates of knickpoint propagation for time durations ranging from 102 to 107 years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river: first, wave trains linked to the release of the alluvial cover and then, wave trains related to the bedrock incision, which correspond to the real time response of rivers. Wave trains with very low retreat rates (long lived knickpoints > 1 My) rather correspond to the response time of regional landscape

Morphological dynamics of an englacial channel

“…3 is analogous to that of the Holocene bedrock channel profile development reported by Baynes et al (2015) for the Jökulsárgljúfur canyon, Iceland, albeit over markedly differing timescales. This morphological development is comparable with the wave train model of stepped terrestrial channels (Loget and Van Den Driessche, 2009). Englacial step risers were rarely observed to be undercut and overhanging, suggesting that undercutting is an insignificant process in englacial step evolution and migration, similar to what is observed for many bedrock waterfalls (Lamb et al, 2007;Young, 1985).…”

“…Series of knickpoints or knickzones along a channel often appear as "wave trains" that may exhibit regular frequency or density (e.g. Chin, 2003;Loget and Van Den Driessche, 2009 Wohl, 1993;Wohl et al, 1999). This has been suggested to be the dominant mode of channel adjustment, in response to either regional or local perturbation (Bishop et al, 2005;Larue, 2008;Shumm et al, 2000).…”

“…This has been suggested to be the dominant mode of channel adjustment, in response to either regional or local perturbation (Bishop et al, 2005;Larue, 2008;Shumm et al, 2000). Channel profile development from the progressive headward recession of knickpoints, whose rates of adjustment may be varied, has been referred to as the wave train model (Loget and Van Den Driessche, 2009). However, there is no consensus as to the origin and shape of knickpoints or the mechanisms causing knickpoint recession in bedrock channels across annual to millennial timescales (e.g.…”

“…It is argued that knickpoint propagation is controlled by discharge and the contributing drainage area (e.g. Bishop et al, 2005;Crosby and Whipple, 2006;Loget and Van Den Driessche, 2009) and that substrate characteristics influence both the recession rate and shape of the knickpoint face (Gardner, 1983;Larue, 2008;Phillips and Desloges, 2013). …”

Patterns of Quaternary uplift of the Corinth rift southern border (N Peloponnese, Greece) revealed by fluvial landscape morphometry

“…We crudely estimate what is called here 'recent' from the length of the involved downstream segments (10-25 km for 100-200 km 2 catchments). Indeed, several studies derived relationships between the average propagation rate of an erosion wave and drainage area that consistently point to rates around 1 m year -1 in rivers with A ~ 100 km 2 and time scales of 10 3 -10 4 years (Bishop et al, 2005;Loget and Van Den Driessche, 2009;Ye et al, 2013). According to such relations, the last uplift phase in the northern Peloponnese would have started some 10-20 ky ago.…”