Turbulence Structure and Bank Erosion Processes in Dredged Channels

Abstract

Riverbank erosion represents a critical challenge, profoundly influencing geomorphological dynamics and compromising the stability of human and infrastructural systems. The geomorphological impacts include form changes such as lateral channel migration, meanders, and channel expansion. The anthropogenic effects include the threat to floodplain human habitation, agricultural land, and stability of instream hydraulic structures and buried pipelines. Channel dredging for the extraction of sand and gravel has seen a multi-fold rise in the last few decades. Pit excavation directly impacts the fluvial erosion characteristics of the riverbank. Pit action increases the Reynolds shear stress in the near-bank flow, which causes progressive fluvial erosion of the berm at the bank toe. The erosivity of the main channel flow in the riverbank also leads to channel degradation, which increases the exposed height of the bank slope. Pit dredging leads to the generation of stronger ejection bursts which provide a mechanism for berm sediment mobility and erosion. The study reveals that instream mining has notable effects on the inherent nature of higher-order turbulence statistics, especially near the bank slope and toe, as well as the multiscale morphological structures.