Criteria and tools for determining drainage divide stability

Abstract

10 11Watersheds are the fundamental organizing units in landscapes and thus the controls on 12 drainage divide location and mobility are an essential facet of landscape evolution. Additionally, 13 many common topographic analyses fundamentally assume that river network topology and 14 divide locations are largely static, allowing channel profile form to be interpreted in terms of 15 spatio-temporal patterns of rock uplift rate relative to base level, climate, or rock properties. 16Recently however, it has been suggested that drainage divides are more mobile than previously 17 thought and that divide mobility, and resulting changes in drainage area, could potentially 18 confound interpretations of river profiles. Ultimately, reliable metrics are needed to diagnose 19 the mobility of divides as part of routine landscape analyses. One such recently proposed 20 metric is cross-divide contrasts in c, a proxy for steady-state channel elevation, but cross-divide 21 contrasts in a number of topographic metrics show promise. Here we use a series of landscape 22 evolution simulations in which we induce divide mobility under different conditions to test the 23 utility of a suite of topographic metrics of divide mobility and for comparison with natural 24 examples in the eastern Greater Caucasus Mountains, the Kars Volcanic Plateau, and the 25 western San Bernadino Mountains. Specifically, we test cross-divide contrasts in mean gradient, 26 mean local relief, channel bed elevation, and c all measured at, or averaged upstream of, a 27 reference drainage area. Our results highlight that cross-divide contrasts in c only faithfully 28 reflect current divide mobility when uplift, rock erodibility, climate, and catchment outlet 29 elevation are uniform across both river networks on either side of the divide, otherwise a c-30 anomaly only indicates a possible future divide instability. The other metrics appear to be more 31 reliable representations of current divide motion, but in natural landscapes, only cross-divide 32 contrasts in mean gradient and local relief appear to consistently provide useful information. 33Multiple divide metrics should be considered simultaneously and across-divide values of all 34 metrics examined quantitatively as visual assessment is not sufficiently reliable in many cases. 35We provide a series of Matlab tools built using TopoToolbox to facilitate routine analysis. 36 37

Landscape ‘stress’ and reorganization from χ‐maps: Insights from experimental drainage networks in oblique collision setting

“…; Mudd, ; Whipple et al. ; Forte and Whipple, ). A potential pathway to promote stability is then for the water divide to migrate toward the channel head with the higher χ value (Willett et al.…”

Base Level and Lithologic Control of Drainage Reorganization in the Sierra de las Planchadas, NW Argentina

“…Using TopoToolbox 2.3 (Schwanghart & Scherler, ), we calculated χ values for all channels draining the Sierra de las Planchadas, using an A 0 value of 1,000,000 m 2 (see Text S5). The choice of outlet elevation can potentially change χ values (Forte & Whipple, ); due to the high local base level differences across the range, we used the regional base level elevation of the junction between Rio Chaschuil and the main channel that drains the Fiambalá Basin, 1,500 m, as the outlet for our χ analysis (Figures b and S5, see Text S5.1). The choice of m/n can also affect the shape of the linearized channel profile; an incorrect m/n value can lead to distortions in χ values and obscure information about the transient conditions affecting a drainage network (Gailleton et al, ; Mudd et al, ; Robl et al, ).…”

“…Local headwater relief, as it is intrinsically linked to slope, can be used to approximate relative erosion rates between adjacent drainage basins (Forte & Whipple, ; Whipple, Forte, et al, ). As the location of a drainage divide is largely controlled by erosion rates on either side of the divide, local headwater relief can provide an indication of the direction of drainage reorganization through progressive divide migration and potential stream capture events (Gilbert, ; Whipple, Forte, et al, ).…”

“…As the location of a drainage divide is largely controlled by erosion rates on either side of the divide, local headwater relief can provide an indication of the direction of drainage reorganization through progressive divide migration and potential stream capture events (Gilbert, ; Whipple, Forte, et al, ). Generally, catchments with lower headwater relief are at risk of area loss from adjacent drainages with higher relief (Forte & Whipple, ).…”

Geomorphic response to active tectonics: Numerical and field‐based approaches

“…They follow an approach introduced by Willett et al (2014) that, though recently challenged by Forte and Whipple (2017), has proven promising in various contexts. They follow an approach introduced by Willett et al (2014) that, though recently challenged by Forte and Whipple (2017), has proven promising in various contexts.…”