Abstract
It is now well established that extreme events such as earthquakes , landslides, floods or storms have a significant effect in shaping landscapes. River terraces, knickpoints, alluvial fans and other morphological markers are routinely used to date and quantify landscape response to changes in climate or tectonics over long time-scale (>10.000 yr). However, those markers are rarely used to assess the natural variability of extreme events’ frequency and magnitude because both the formation and the evolution of those markers in response to internal or external solicitations remains poorly studied.Here, we propose to develop a new approach based on a multidisciplinary study of the small time-scale evolution of landscapes (from 0.1 to 50000 yr). We aim to investigate the feedbacks between river high-discharge events and earthquake cycle deformation, which are the elementary driving processes linking tectonics, climate and landscapes. This approach is complex and requires deciphering the signature of climatic and tectonic processes (1) from the detailed study of present-day landscape features, and (2) by considering their stochastic nature as well as their couplings and feedbacks. This requires exploring many fundamental but unresolved questions: What are the morphological signatures (magnitude and frequency distribution) of climatic and tectonic perturbations in the topography equilibrium? What is the time-scale over which abrupt changes due to extreme events remain visible? Is steady-state a purely theoretical concept or does it apply to natural landscapes subjected to extreme events?We will address these issues through an integrated approach combining the development of a new generation of both experimental and numerical models, remote sensing data, and field observations.At this short time scale, compared to previous studies considering tectonic and climatic forcing separately, the proposed approach, which takes into account the stochastic nature of floods and earthquakes as well as the deformation associated with all earthquake cycle periods, represents a new milestone in landscape evolution understanding. Beyond the expected scientific results and technical benefits, this project by its generic nature will be useful to improve flood- and seismic-hazard assessment, in terms of predictability and mitigation.