Acoustic estimation of suspended sediment concentration from turbidity in the nearshore areas off Visakhapatnam

Abstract

Patnaik, KVKRK., Suresh, RRV., 2014. Acoustic estimation of suspended sediment concentration from turbidity in the nearshore areas off Visakhapatnam, Proceedings of the Fifth Indian National Conference on Harbour and Ocean Engineering (INCHOE2014), 5-7 Feb. 2014, CSIR-NIO, Goa, India. Accurate estimation and monitoring of suspended sediment concentration in the nearshore areas is a challenging task involved in the maintenance of draft of navigational channels, ports and harbors. In the nearshore environment Suspended Sediment Concentration varies significantly both in time and space in response to various forcing mechanisms. Though estimation of this through Acoustic remote sensing is a surrogate method, it is proved to be a best method. The present study is based on the simultaneous data obtained from 600 Khz workhorse ADCP, Turbidity sensor and LISST portable. ADCP was side mounted to BTV Sagar Manjusha at a depth region of 20m and programmed to record the data for every one minute for the period of 3 days to cover six tidal cycles. These data are used to develop a location specific version of the sonar equation which converts the ADCP echo intensity to turbidity (NTU). This equation was obtained by relating echo intensity and turbidity. It is also found that the particle size in the study area ranging from 50 – 400 μm. It is also found that the estimated turbidity is in good agreement with the measured turbidity values.