Role of stationary convective bands and antecedent conditions on the flood response to the Vaia storm (October 27-30, 2018) in the Eastern Italian Alps
- 1Department of Land Environment Agriculture and Forestry, University of Padua, Padova, Italy (mattia.zaramella@unipd.it)
- 2Research Institute for Geo-Hydrological Protection, National Research Council of Italy, Padova, Italy
- 3Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
- 4Institute of Atmospheric Sciences and Climate, National Research Council of Italy, Bologna, Italy
- 5Faculty of Science and Technology, Free University of Bozen-Bolzano, Bolzano, Italy
- 6Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy
Between the morning of 27 October 2018 and the evening of 29 October 2018, heavy precipitation over the Eastern Italian Alps led to damaging flooding. The event, which occurred at the end of a climatic anomaly of prolonged drought, developed into two phases, with a first phase (October 27-28) dominated by more stratiform orographically-enhanced precipitation. After a short lull, a second and more intense phase of the event took place on the 29th, when a cold front from the Gulf of Lion entered the Mediterranean basin triggering explosive cyclogenesis. A characteristic of the second phase of the storm is the rainfall organization in well-defined convective bands, some of which persisted at the same location for up to 3 hours. The bands, aligned from southeast to northwest, were initially located downstream of the pre-alpine region.
The work aims to investigate the impact of the stationary convective bands and of the dry antecedent conditions on the flood response to the storm. The availability of high-resolution rainfall estimates from weather radar and of dense rain gauge network data, along with flood response observations from stream gauge data and post-event surveys, enables to study the hydrometeorological and hydrological mechanisms associated with this extreme storm and the consequent flood response.
Observational and model analyses of the hydrologic runoff in two areas heavily impacted by the storm (Noce river basin, in the Trentino Province, and upper Cordevole river basin, in the Veneto Region) illustrate how the structure and evolution of the stationary convective bands translate into scale dependent flood response. For the upper Cordevole river basin, the event envelope curve shows two peculiar behaviors: (a) basin scale ranging from 1 to 200 km2, with peak unit discharges decreasing from 10 to 4 m3s-1km-2; (b) basin scale ranging from 200 to 2000 km2, with smaller peak unit discharges. The spatial extent of the first region is controlled by the structure of the central convective band. Moreover, the spatial moments of catchment rainfall are exploited to identify the impact of the convective cells motion along the stationary band on the flood response.
How to cite: Zaramella, M., Marchi, L., Marra, F., Comiti, F., Crema, S., Marchio, M., and Borga, M.: Role of stationary convective bands and antecedent conditions on the flood response to the Vaia storm (October 27-30, 2018) in the Eastern Italian Alps, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18668, https://doi.org/10.5194/egusphere-egu2020-18668, 2020.
