New Grant to Start : ALTROCLIMA

ALTROCLIMA is a three-year project funded jointly by the Swiss National Science Foundation and the Autonomous Province of the South Tyrol (Italy). It will support two PhD students based at the University of Lausanne, Switzerland, and a research assistant and a post-doctoral researcher at the Free University of Bozen-Bolzano, Italy (Professor Francesco Comiti, and involves a number of project partners in Switzerland and Italy.

Project aims and objectives

Alpine landscapes are experiencing climate warming at rates higher than other regions of the world. Globally, impacts of warming on the cryosphere are evident in all mountain regions including permafrost degradation; rates of mass movement (rockfalls, debris flows, landslides) at higher altitudes; river flows; and terrestrial/ aquatic ecosystems. Predictions of changing snow/ice cover are available to the end of the 21st century and there are attempts to couple climate change to river flow in Alpine landscapes including correct treatment of the cryosphere. How bedload transport will evolve under these drivers is much less well-established despite the important environmental significance of bedload for the ecological functioning of Alpine streams and for its potential hazard to Alpine communities. There are only a few decadal-scale records of bedload transport in mountain basins and almost no studies coupling such records to changing river basin function, historically or in terms of predictions. Such analysis must consider the balance between climate-driven changes in bedload supply (S) and bedload transport capacity (C); but also the feedbacks that follow when SC, such as sediment sorting processes when S<C. It is challenging because bedload transport is exceptionally difficult to measure and globally, unlike other measures of environmental change, we have very few instrumented sites worldwide for bedload transport monitoring extending to more than a decade of observations.

Aims and objectives:  The core aim of this project is to understand and to predict how rapid climate warming has and will impact bedload transport in Alpine environments at the centennial timescale. The objectives are;  O1 to provide the first reliable, multi-site quantification in Alpine environments of how bedload transport is changing under warming; O2 to determine the relative role of landscape-scale processes in driving estimated bedload export in the analyzed basins; O3 to establish an appropriate modelling framework for predicting glacier and hillslope bedload supply to the river network using evidence from O1 and O2; O4 to calibrate and to validate of a predictive model for representing bedload flux through the drainage network supported by data from O3; and O5 to provide the first predictions of Alpine bedload transport under future climate considering changes in both supply and capacity.

Methods: Using an innovative method for analyzing the bedload flushing records provided by high altitude Alpine water intakes we will reconstruct bedload export for more than 60 Alpine basins with varying glacier cover for the Swiss Alps and South Tyrol (O1). We will combine these within-basin reconstructed erosion and deposition patterns and connectivity analyses to explain the changes found in O1 (O2). Using results from O2 we will identify and test against O1 the relative merits of stochastic and physically-based models of subglacial and hillslope bedload delivery to the river network (O3). We will integrate these models to generate network-scale predictions of bedload transport under climate change with relative uncertainty (O4).

Expected results and impact: The research will produce the first decadal-scale multi-site quantification of how bedload transport has changed in Alpine environments due to climate warming and why. It will provide the first predictions with uncertainty of how Alpine bedload transport might evolve under 21st century climate change. The associated understanding and predictions will not only be of academic value but also of importance for water resource managers (including hydropower companies and national/local flood mitigation agencies) in Alpine regions.