Secondary Flow and Turbulent Kinetic Energy in a Dredged Channel with Riverbank

Sand dredging from the rivers has become an uncontrolled practice that harms the river's ecology. It affects the flow structure of the river, leading to further deterioration of the river's morphology. Several field investigations and experimental studies have conformed to the erosive effects of sand mining pits upstream and downstream of mining locations. We conducted laboratory-scale flume experiments to study the impact of a mining pit on the secondary flow structure across a riverbank cross-section. Three bank slopes were tested, namely, 25°,31°, and 40°, and gravity flow experiments were conducted with and without a mining pit. Turbulent velocity data across the cross-section was analyzed to study the transverse and velocity distribution across the riverbank for both with-pit and without-mining-pit cases. Results show that dredging an upstream mining pit significantly affects the transverse and vertical velocities, especially on the bank slopes and near the bed in the main channel portion. The turbulent kinetic energy in the flow region on the bank slope and near the bed in the main channel portion significantly increases because of the pit excavation. These alterations in the secondary flow within the riverbank can lead to morphological changes and may affect the bank stability of rivers.

Keywords: Sand Mining, Turbulent kinetic energy, turbulence