Author(s): Francesco Caponi; David F. Vetsch; Davide Vanzo

Linked Author(s): Francesco Caponi, Davide Vanzo, David Vetsch

Keywords: Hydropeaking; Vegetation; Recruitment model; River bars; Alpine Rhine

Abstract: The flow regime is a critical driver of riparian vegetation dynamics along river corridors. Plants rely on the natural alternation of benign and disturbance-driven periods to develop and maintain their ecological functions. However, hydropeaking - the rapid sub-daily variation of flow discharge- has been increasingly recognized to affect vegetation growth by interrupting inundation-free periods. Despite this increasing evidence, the effect of hydropeaking on early vegetation establishment remains largely unexplored. Here, we disentangle this effect by applying a recruitment model based on the concept of the window of opportunity (WoO) on a 12-km long reach along the Alpine Rhine River, Switzerland, which experiences daily hydropeaking and showed vegetation recruitment dynamics on alternate gravel bars. To estimate area for potential recruitment, we setup and run a 2D hydrodynamics model and used it to derive spatially distributed water level time series in the period 1996-2022 based on measured discharges. We then created an alternative hydrological scenario, which differs only in the hydropeaking signal, and we compared the associated successful recruitment area to the estimated ones. We found that hydropeaking affects the vegetation extend on bars when floods coincided with the growing season. In contrast, the effect of hydropeaking tends to vanish in years when floods occurred after the growing season. The model results indicate that successful recruitment events depend on vegetation stress resistance, indicating that fast-growing vegetation may also profit from early floods. Our study advances our understanding of complex disturbance-dependent systems in hydropower-impacted systems and may prove a quantitative foundation for the design of e-flows and hydropower operation.

DOI: https://doi.org/10.64697/iahr.proc.ise2026.abs.171

Year: 2026