Extracting the critical rooting length in plant uprooting by flow from pullout experiments

Valentina Bau', Simone Zen, Giulio Calvani, Paolo Perona

Research output: Contribution to journalArticlepeer-review


The growth and establishment of riparian vegetation on river bedforms is of hydrological as well as ecological importance as it helps in enhancing spatial heterogeneity and thus the biodiversity of river corridors. Yet, during floods, flow drag and scouring may reduce the rooting length of plants determining plant mortality via uprooting. In order for uprooting to occur, bed scouring must proceed until the rooting length reaches a critical value and drag forces exceed root residual anchorage. Therefore, the critical rooting length of a plant rep-resents a crucial parameter to estimate the probability of plant removal due to flow erosion. However, diÿculties in quantifying such length at the field scale have limited so far the per-formances of biomorphodynamic models for river bed evolution. In this work, we propose to assess the critical rooting length from controlled plant pullout experiments. To this aim, a free-body model of the forces acting on a flexible plant in a stream at di˙erent erosion stages is developed. At incipient uprooting, we conjecture that the root resistance at the critical rooting length equals that of a plant with equal rooting length when pulled out in static con-ditions. To illustrate our approach, we validate our model on three di˙erent datasets obtained from small- and real-scale plant uprooting experiments. A comparison between modelling and experimental observations reveals that the model provides valid results, despite its de-terministic approach. The critical rooting lengths are finally used to assess the probability density function of the time-to-uprooting via a physically-based stochastic model
Original languageEnglish
JournalWater Resources Research
Early online date9 Nov 2019
Publication statusE-pub ahead of print - 9 Nov 2019


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