Author(s): Dennis Ronckers; Daan W. Poppema; Davide Wuthrich

Linked Author(s): Davide Wüthrich

Keywords: Driftwood; large wood; backwater rise; debris accumulation; Laser Doppler Velocimetry; carpet length

Abstract: This study investigates the effect of driftwood on submerged culverts through scale experiments, focusing on their accumulation and the hydrodynamic processes occurring underneath. Examining temporal evolution and velocity measurements, this research delves into the implications of driftwood accumulation, including its geometry, hydraulic conditions and associated backwater rise. Findings reveal that accumulation shape is strongly influenced by hydraulic conditions, with higher Froude numbers pulling logs toward the bottom and thus yielding more compact accumulations. This effect holds implications for submerged culverts, where the opening near the bottom diminishes the importance of surface flow resistance. Accurate prediction of accumulation lengths is achieved using wood volume and initial flow velocity. The study also provides valuable data for developing quantitative design equations for backwater rise from driftwood accumulation at culverts. Additionally, detailed measurements of velocity profiles and Reynolds stresses under the accumulations highlight a slightly lower flow velocity, prompting the need for future research to discern its generality and implications for driftwood-induced scour at submerged culverts.

DOI: https://doi.org/10.3929/ethz-b-000675921

Year: 2024