The response of a mountain drainage basin to extreme events: the impact of Vaia storm on Rio Cordon (Dolomites, Italy)

Giacomo Pellegrini¹, Luca Mao^2,3 & Lorenzo Picco^1
1Department of Land, Environment, Agriculture and Forestry, University of Padova, Padova, Italy.
²Department of Geography, Catchments and Coasts Research Group, University of Lincoln, UK.
³Instituto de Geografía, Pontificia Universidad Católica de Chile, Chile.
Corresponding author e-mail: giacomo.pellegrini@unipd.it

Current literature is limited in understanding the responses of mountain basins to large disturbances, especially when it comes to integrating analyses of sediment transport, geomorphic changes, and topographical conditions, as these aspects are often examined at varying spatial scales. This manuscript explores the impact of the Vaia storm (27-30 October 2018) on the Rio Cordon Basin (Dolomites, Italy). Integrating data from three studies conducted at different spatial scales, it examines hydrological, geomorphological, and sedimentological responses of the basin to the large infrequent event. The findings encompass changes in channel network, step-pool morphology evolution, and sediment flux alterations. Streambed remobilization, boulder mobility, incision, and lateral erosion were observed. The step-pool morphology experienced disruption but recovered to stability within two years. Surprisingly, suspended sediment fluxes and yields after two years form the event (42 t km^-2 years^-1) were consistent with pre-Vaia conditions (40 t km^-2 years^-1). The integration of pre- and post-event data proved valuable for understanding the basin’s responses to extreme events. Based on current conditions, Rio Cordon appears to be returning to a pre-event state, establishing a new dynamic equilibrium, as the Vaia event induced morphological changes while sediment fluxes and step-pool stability remained in line with pre- event conditions.

Vaia storm, Rio Cordon, mountain basin resilience, dynamic equilibrium, sediment transport.