Author(s): Takaaki Okamoto; Kenta Tanaka; Kazumasa Matsumoto; Michio Sanjou

Linked Author(s): Takaaki OKAMOTO, Michio Sanjou

Keywords: Backwater rise; Porosity of woody debris jam; Surface hydraulics; Bridge clogging; PIV

Abstract: Large wood in rivers seriously increases the destructive power of flood flow. Large wood accumulates at bridges and woody debris jam blocks rivers, which leads to increased water levels. In Shiso city Japan in 2018, the floodplain flow occurred around the bridge and the river bank was eroded. However, there are few experimental studies published on bridge clogging process at a single pier bridge. In this study, the flume experiments were performed in a 10m and 40cm wide flume. First, wooden dowels (6.0, 7.0 and 8.0 cm length) were used to model driftwood. Model logs were supplied to the flow at 4.0m upstream from the model bridge. Backwater rise due to woody debris jam was measured by a point gauge. The results were compared with the porous board tests (Okamoto et al. (2020, JFRM) and we examined the effect of the log length on the porosity of woody debris jam. Next, we measured the flow velocity under the woody debris jam at the bridge using PIV. The effect of velocity field on the driftwood accumulation was investigated.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022781

Year: 2022