The ship-generated waves in restricted waterways can influence the behavior of sediment resuspension and bank erosion. The suspended sediment concentration (SSC) measurement is one of the key parameters in analyzing sediment resuspension. Therefore, through field measurements in the Falta stretch of the Hooghly river, India, the sediment resuspension due to ship-generated waves are investigated. The velocity was measured using the ADCP and based on the back-scattering intensity, SSC has been estimated. Thus, the introduced data collection technique and proposed methodology of estimating SSC is an essential step in better understanding of the impact of ship-generated waves in restricted waterways.
Natural rivers are mainly governed by the incoming natural water and sediments from the upstream, undergoing severe morphological changes, which eventually stabilizes by altering the river flow and redeposition of the excess sediments. Unlike natural streams, inland waterways experience human interference as they are cheap, eco-friendly modes of transportation of bulk materials. There is a steep increasing traffic of marine vehicles in inland waterways for the purpose of trade and transport worldwide. The navigation of marine vehicles in inland waterways influences the hydrodynamic and fluvial conditions by generating waves and currents. The most impact of these waves is experienced at the shallow water depth near the banks where the wave breaking and shoaling occurs (Fleit et al., 2019; Chakraborty et al., 2022). Ship-induced waves play a pivotal role in shoreline erosion, resuspension of sediments, and loss of aquatic life. Thus, to conserve the natural ecosystem, a study of the sediment transport due to ship-generated waves is important.
One of the important parameters to understand the sediment transport is suspended sediment concentration (SSC) (Dwinovantyo et al., 2017). The measurement of SSC can be done in various ways such as conventional (laboratory analysis), optical and acoustic methods. The conventional method is primitive and has lot of disadvantages. It is labor extensive, as several water samples are required at various depths at the measurement station. Moreover, this method fails to provide time-series and spatial variation of SSC. On the other hand, Optical backscattering sensors (OBS) measure SSC by means of backscattered light, and their measurements are restricted to a single point in a fixed deployment (Lin et al., 2020). The spatial variation of SSC could be obtained by multiple deployments of OBS along the spatial direction. However, this arrangement may disturb the natural flow field and influence the sediment transport. The OBS are highly sensitive to particle size variation and perform poorly in regions of varying sediment size (Ludwig and Hanes, 1990). Along with optical backscattering-based devices, acoustic tools have become widely popular within the hydro science community (Thorne and Hanes, 2002). The backscattering intensity obtained from the ADCP could be used extensively to analyze SSC in a riverine environment (Latosinski et al., 2014; Dwinovantyo et al., 2017; Manik and Firdaus, 2021). Recent studies also found a good correlation between acoustic backscatter from ADCP and measured concentration by direct measurement (Guerrero M, et al., 2011). Moreover, a measurement from ADCP resolves the issue of spatial and temporal variation of SSC.
