Author(s): Jean Deivi Huaraca Canchari, Julio M. Kuroiwa, Luis Fernando Castro Inga

Linked Author(s): Jean Deivi Huaraca Canchari, Julio M. Kuroiwa, Luis Fernando Castro Inga

Keywords: Engineered Log Jams (ELJ); Permeable Groynes; Local Scour; Riverbank Erosion Control; River Hydrodynamics;

Abstract: This article summarizes the result of an experimental program in which the main objective was studying the influence of permeability on the maximum local scour caused by a stream on an Engineered Log Jam (ELJ) groyne. A series of 5 experiments was conducted to study the influence of groyne permeability on the local scour at the groyne tip. One permeable groyne, whose length (perpendicular to the flow direction) was 0.475 m and whose width was 0.26 m was placed on the right side of a rectangular channel. Groynes were made up of cylindrical wood pieces that represented tree trunks. They were interlocked to form a rectangular prism that was a scaled down ELJ groyne. Permeabilities of these structures ranged from 28 % to 51 %. Tests were conducted in a 12 m long flume whose net width was 1.9 m. Maximum discharge was 155 L/s. Initial bed slope was 0.008 m/m. The streambed was composed by sand whose average diameter, D50, was 0.204 mm. An Acoustic Doppler Velocimeter (ADV) was used to measure and map 3D velocities at selected cross sections and around the groyne. A 3D laser scanner was used to capture bed topography before and after the tests. As a result of the experiments it was observed that local scour at the groyne tip decreases when groyne permeability increases. ELJ groyne permeabilities were 28%, 36%, 42.5%, 45.5% and 51%. For these permeabilities local maximum local scour, recorded at the groyne tip were 0.225 m, 0.092 m, 0.090 m, 0.088 m and 0.087 m, respectively. A practical lower limit for maximum local scour was found when the groyne permeability was between 42.5 and 51%. ELJ groyne permeability may be included as a design criterion when local scour is to be reduced in an erosion control project.

DOI: https://doi.org/10.3850/38WC092019-1433

Year: 2019