Author(s): Seyed Mahdi Jafari Mohammadi; Kaisa Vastila; Juha Jarvela
Linked Author(s): Juha Järvelä, Kaisa Västilä
Keywords: No Keywords
Abstract: Floodplain vegetation strongly influences river hydraulics by modifying flow resistance, sediment transport, and habitat structure. However, predicting drag forces from patchy canopies remains challenging due to variations in spatial scale, canopy density, configuration, and flow submergence. This study examined how patch configuration, density, and relative submergence affect vegetation-induced drag across plant, patch, and reach scales. Flume experiments using nature-like woody vegetation arranged into compact and elongated patches at two densities were conducted under emergent and submerged flow conditions. Drag forces were measured directly with a custom drag plate system. Results show a nonlinear increase in drag with spatial scale, with reach-scale canopies producing the greatest drag. Vegetation caused higher drag under emergent conditions, while increased submergence reduced overall drag and minimized configuration-related differences. These findings emphasize the need to incorporate scale, density, configuration, and submergence in ecohydraulic modeling and nature-based flood management.
Year: 2026