On the vulnerability of woody riparian vegetation during flood events

Abstract

Wood is recognized as a key element of river ecosystem for a large number of positive feedbacks with biotic and abiotic components, both when it is present as large wood deposit or as live vegetation on the riparian zone. Despite the positive impacts of wood, when considering the high flow events, the presence of woody riparian vegetation within the channel can increase the potential risk related to local wood accumulation, bridge clogging or damages at hydraulic structures. Both the effects given by the riparian vegetation and in-channel dead wood need to be considered when evaluating the large wood-related hazards in rivers. For these reasons, we need to increase the knowledge on the relative importance of floodplains in recruiting large wood. An analysis was conducted on the base of a post event field survey on the Ombrone Grossetano River (Italy) which helped to identify the main variables controlling the uprooting process of riparian vegetation. The implementation of a conceptual model for plant stability helped to predict the tree uprooting that occurred during that flood event. The proposed approach can be extended to any other gravel-bed rivers, such that the evaluation of the vulnerability of woody riparian vegetation can give practical advices for maintenance strategies about vegetation cutting.