1191 | 801 | Post-wildfire erosion and depositional processes in Western Sardinia | Pala, C. (1); Brunetti, M.T. (3), Cinus, S. (2); Deiana, G. (1); Loddo, S. (2); Melis, M.T. (1); Pioli, L. (1)

On 24 July 2021, a wildfire ravaged Western Sardinia, burning an oak forest, olive groves, vineyards and grazes and damaged several buildings in two different towns. It extended up to 20 km from the ignition point, burning approximately 10,000 hectares in 8 hours. In the following week, small fronts of fire were still burning, until the fire was officially declared extinguished on July 30 when a surface of 20,000 hectares was burned._x000D_
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The south-eastern part of the fire affects the Montiferru Volcanic Complex (western Sardinia, Italy), mainly consisting of lava domes and lava flows. The steep slopes of this relief are covered, from the mid-slope to the bottom area, by cobble-rich colluvial deposits and soils, sometimes with andic characteristics, whereas the upper slopes usually consist of bedrock outcrops._x000D_
In the three months following the wildfire, windstorms remobilised ash across the burned areas and, in November 2021, the first rainstorm occurred. During this event, a rapid mud flow with ash and burnt vegetation flowed to the sea cost, for about 12 km._x000D_
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After the wildfire, we performed field surveys to characterise soil erosion and sedimentation processes. Sheet wash erosion was observed mainly in the slopes mantled by colluvial deposits whereas rill erosion is the main erosional style on the slopes mantled by soils. In valleys, lateral erosion is associated with the formation of plunge pools and exposures of the bedrock. In rills, gullies, and channels, traces of temporary damming were recognized. These temporary dams are made of blocks, cobbles and/or organic materials such as burned logs and branches. They obstruct channels and temporarily collect the sediment transported from the upper areas. When the sediment is remobilised through rainfall-induced debris flows they can create levees and fans.

Pala, C. (1); Brunetti, M.T. (3), Cinus, S. (2); Deiana, G. (1); Loddo, S. (2); Melis, M.T. (1); Pioli, L. (1)
1) Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria-S.S. 554 Bivio per Sestu I, 09042 Monserrato, Cagliari, Italy. 2) General Directorate of Civil Protection – Sardinia Government, Via Vittorio Veneto 28, 09123 Cagliari, Italy; 3) CNR IRPI, via Madonna Alta 126, 06128 Perugia, Italy
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