Tracing suspended matter in Tiab estuary applying ANN and Remote sensing

Abstract

Knowledge about deposition and sedimentation in estuaries is important since these environments are favorable domain for human activity. Variety of hydrodynamic parameters causes sedimentation/deposition in an estuary among them tidal current. It is therefore necessary to monitor these processes in estuaries and provide strategies to control the rate of sedimentation/deposition. Several methods are available to measure total suspended solids (TSS). Using combined methods of direct and indirect suspended sediment measurements in this research, we achieved a reliable method to study the suspended sediment status in an estuary located northern of the Persian Gulf, known as Tiab estuary. Field measurements were performed as two scheduled cruises one in October and one in November 2015. Current velocity and turbidity were recorded using RCM9 device and optical backscatter sensor. Water samples were collected using Niskin Bottle. Measurements were carried out both along the estuary and stationery. Artificial Neural Network (ANN) in combination with Linearity method has been applied to reproduce sufficient SS data. The ANN feed-forward back-propagation provides reliable TSS values with the RMSE and correlation coefficient of 0.137 and 0.943, respectively. Results show that the estuary is flood dominated, thus in general the estuary is under constant sedimentation. Applicability of satellite imagery of Sentinel to trace TSS in this estuary is investigated and improved. The difference between the SST rate in the four tidal phases, including high and low tide and flood and ebb phase, was examined using the NSMI-index. We found the average NSMI index in high tide is 0.216, in the low tide is 0.278, in flood phase is 0.302, and in ebb phase is 0.295. Both field and satellite data show that the concentration of TSS in the ebb phase increases, and in the low and high tide decreases. Both results also revealed that the accumulation of TSS in the meandered area is relatively high.