Rockfalls change the runout and frequency of debris flows at Punta Nera (Eastern Italian Alps)

In the Dolomitic region, many debris flow basins have headwaters characterized by extremely steep slopes of bare outcropping rock. Cliffs are commonly incised multiple chutes which rapidly deliver runoff at their base where channels incise scree deposits. Debris flows mobilize and transport sediment along such ephemeral following intense summer convective rainstorms. basin Punta Nera, a series rockfalls, occurred in upper part headwater between 2013 2016, caused dramatic changes dynamics. Starting from 2014, runout events increased so much that it reached national road, runs toe fan, attracting media attention prompting adoption protective measures. Here, we use newspaper reports, direct observations, aerial terrestrial photograph, monitoring data topographic surveys to document rockfalls activity. The sudden increase availability changed magnitude events, critical conditions for debris-flow occurrence.