SEIsmic Monitoring of mountain Rivers: an innovative way to quantify the control of extreme climatic events on river dynamics – SEISMORIV

In most mountain ranges around the Earth, river floods caused by intense precipitation, or the drainage of natural dammed lakes are expected to progressively increase in frequency and magnitude with global climate change. Those more frequent and stronger extreme floods will likely more predominantly set the pace at which alpine rivers evolve and cause hazards for populations over daily to multi-year timescales. However, our limited knowledge of the physics of extreme floods and their impact on river landscapes impedes anticipation of future river landscape changes. Extreme floods can be very damaging, and thus often cannot be observed by traditional measurement methods. This instrumental limit is the main cause of our inability to answer fundamental scientific questions, such as (1) how much, how far and how fast is material (water and sediments) conveyed by rivers during extreme floods? (2) how do the physics of extreme floods impact the long term dynamics of rivers? (3) to what extent do extreme floods determine the long-term evolution of landscapes under a changing climate? The goal of this project is to bring new insights into answering these fundamental questions by overcoming traditional instrumentation difficulties through the innovative use of seismic observations.
We present a novel strategy using seismic observations to provide unprecedented, quantitative observational constraints on extreme flood physics, and to quantify the short to long-term impacts of extreme floods on river landscapes. Our approach builds on recent advances in the emerging field of fluvial seismology, from which an innovative theoretical seismo-mechanical framework was proposed to crucially link river physics (turbulent flow, sediment transport) to seismic signals. The first aim of this project is to demonstrate the validity of the seismo-mechanical framework in natural settings. For this we will monitor designated field sites with state-of-the-art instrumentation of river physical parameters. This will enable us to thoroughly test and validate the newly established seismo-mechanical framework. The second aim of this project is to apply the seismo-mechanical framework to specific river landscapes where extreme floods likely dominate the pace at which landscapes evolve, i.e. they control most of the river geomorphic changes and are the main source of hazard risk for populations. In doing so, we will provide unique quantitative constraints on the physics of moderate to large floods occurring around the world, and on their legacy in the landscape. The large dataset gathered at the multiple targeted sites will allow extracting generic relationships to be used to answer the fundamental question asked above. The third and last aim of the project is to build a communicative platform around the SEISMORIV accomplishments as well as a database gathering all findings acquired in SEISMORIV. This step will set very good grounds to initiate an international, scientific collaborative effort to facilitate the growth and establishment of the novel and rapidly growing field of environmental seismology.