Return period of vegetation uprooting by flow

Fluvial environments are dynamic systems whose evolution and management are strongly affected by the resilience of riparian vegetation to uprooting by flow. Similarly to other natural phenomena, the interactions between flow, sediment and vegetation uprooting is governed by both the magnitude and duration of hydrological events. In this work, we analytically derive the link between probabilities of plant uprooting by flow and the return time of corresponding hydrologic erosion events. This physically-based analysis allows to define the key parameters involved in the plant uprooting dynamics, and to link the uprooting probability of riparian vegetation to plant biomechanical characteristics, hydrological regime and sediment parameters. For example, we show how the rooting depth changes the return time of critical hydrologic event uprooting plants with different probabilities. The model also shows the difference between magnitude driven and duration driven flow uprooting events.The proposed approach is eventually validated against data from field measurements and numerical simulations of pioneer woody species for two flood events with different return period. Our approach demonstrates the strong interrelations between the hydrological river regime and vegetation properties and suggests that such interactions may be key for species recruitment and consequent ecosystem shifts when hydrological regime is altered by either human or climate changing scenarios.