Divide mobility controls knickpoint migration on the Roan Plateau (Colorado, USA)

Abstract

Knickpoints in longitudinal river profiles are proxies for the climatic and tectonic history of active mountains. The analysis of river profiles commonly relies on the assumption that drainage network configurations are stable. Here, we show that this assumption must be made cautiously if changes in contributing area are fast relative to knickpoint migration rates. We studied the Parachute Creek basin in the Roan Plateau, Colorado, United States, where knickpoint retreat occurs in horizontally uniform lithology so that drainage area is the sole governing variable. In this basin, we identified an anomalous catchment in the degree to which a stream power–based model predicted knickpoint locations. The catchment is experiencing area loss as the plateau edge is eroded by cliff migration in proximity to the Colorado River. Model predictions improve if the plateau edge is assumed to have migrated over the time scale of knickpoint retreat. Finally, a Lagrangian model of knickpoint migration enabled us to study the kinematic links between drainage area loss and knickpoint migration and offered constraints on the temporal aspects of area loss. Modeled onset and amount of area loss are consistent with cliff retreat rates along the margin of the Roan Plateau inferred from the incisional history of the upper Colorado River.

Topographic disequilibrium, landscape dynamics and active tectonics: an example from the Bhutan Himalayas

“…This observation suggests that the time scale for channel re-equilibration is here faster than that of the perturbation driven by divide migration, consistent with conclusions from recent numerical experiments by Whipple et al (2017b). This result implies that drainage reorganization by progressive divide migration is not expected to leave here a particular geomorphic signature, most probably because of a relatively high erosional efficiency (Whipple et al, 2017b), in contrast with other field cases where the time for divide migration may have outpaced that of the erosional river response (Schwanghart and Scherler, 2020).…”

“…(Giachetta and Willett, 2018;Struth et al, 2019)). However, an additional feedback may operate as the drainage area reduction upstream of the knickpoint may limit and refrain the upstream knickpoint migration (Schwanghart and Scherler, 2020). Such feedback, by eventually significantly lowering the expected upstream migration of major knickpoints, may contribute to the preservation and surface uplift of the upstream low-relief region over time, to the over-steepening of the downstream river segments and therefore to the large dimensions of observed major knickpoints.…”

Rise of the Colorado Plateau: A Synthesis of Paleoelevation Constraints From the Region and a Path Forward Using Temperature-Based Elevation Proxies

“…River longitudinal profiles may also constrain CP uplift timing (Roberts et al, 2012). However, complications due to varying rock erodibility (Cook et al, 2009;Pederson and Tressler, 2012), normal faulting and paleocanyon integration (Karlstrom et al, 2014), as well as drainage reorganization and resulting changes to stream power (Schwanghart and Scherler, 2020) limit straightforward correlation between river profiles and uplift. Nevertheless, an inverse correlation between channel steepness and upper mantle p-wave velocity in the Virgin River drainage suggests epeirogenic uplift affects modern CP river profiles (Walk et al, 2019).…”

A systematic approach and software for the analysis of point patterns on river networks

“…The margins of the Chilao Flats show highly asymmetric divides (Scherler & Schwanghart, 2020) (Figure 7) which suggest possibly past and ongoing drainage reorganization. Such reorganization may significantly alter drainage areas and discharge, and thus affect knickpoint celerities which in return could result in more scattered knickpoint locations (Schwanghart & Scherler, 2020).…”

“…Many geomorphic phenomena along rivers can be represented as spatial point processes. For example, bank failures (Fonstad & Marcus, 2003; Liang et al, 2015), landslide dams (Korup, 2006; Tacconi Stefanelli et al, 2015; Fan et al, 2020), riffle‐pool sequences (Golly et al, 2019), wood jams (Wohl, 2013; Scott et al, 2019), and knickpoints (Berlin & Anderson, 2007; Phillips & Lutz, 2008; Gailleton et al, 2019; Schwanghart & Scherler, 2020) are phenomena that occur at specific locations along rivers and that – at particular spatial scales of analysis – can be represented as point features. Many questions about these processes are inherently linked to their spatial arrangement.…”