Generalization of the Khi-analysis of landscapes to channel-hillslope systems

International audienceThe Khi-analysis of river profiles (Perron and Royden, 2012) is a powerful method to highlight geomorphic disequilibriumin river networks. Recent studies (e.g. Willett et al., 2014) demonstrated how this proxy can be usedto infer reorganization of river networks in response to processes such as fluvial captures of horizontal migrationof drainage divides. Rapid river adjustments to such perturbations may however limit the use of this approach(Whipple et al., 2017) Because hillslopes have potentially longer response times than channels, they likely havethe capability to record geomorphic disequilibrium over longer time-scales than channels.We consequently presenthere a generalization of the Khi-analysis to the entire landscape, i.e. to the channel-hillslope system. We will firstpresent a theoretical formulation of the Khi-analysis to the full hillslope-channel system by considering the continuityof the slope-area relationship at the hillslope-channel transition. We will then show how this generalizedKhi-analysis allows to linearize the entire channel-hillslope longitudinal profiles taken from synthetic numericaland laboratory-scale topographies at steady-state. We fill finally illustrate the use of generalized Khi-analysis toinfer geomorphic disequilibrium in some natural case studies