Assessment of Dredging-induced Sedimentation on Winter Flounder Spawning Habitat

This study investigates the fate of sediment suspended due to dredging in Newark Bay, New Jersey to characterize exposure of winter flounder spawning habitat. Winter flounder is a recreationally and commercially significant species which has experienced a steady population decline over the last twenty years. Winter flounder eggs are demersal and adhesive. Possible factors affecting spawning habitat are currently being investigated, including net deposition on eggs during dredging operations. To investigate potential egg exposures to elevated sedimentation rates, a numerical modeling study was conducted. The three-dimensional hydrodynamic model CH3D-WES (Curvilinear Hydrodynamic model in Three Dimension, Waterways Experiment Station version) was applied to Newark Bay and adjacent water bodies. The model was calibrated to water level and current data. Bottom stresses during January of 2008 were estimated and analyzed to assess depositional environments in the bay. The Particle Tracking Model (PTM), linked to the Newark Bay CH3D model, was utilized to simulate dredged sediment transport and deposition. The development of tools which reliably predict sediment transport due to dredging operations represents a critical advance to the field of dredged material management. These predictions can be used to assess the impact of dredging and placement operations on contaminant transport, sensitive habitat, endangered species, rehandling, and beneficial use activity. PTM is a Lagrangian particle tracking model specifically designed to assess the fate of specified sediment sources, such as dredging operations. Relevant hydrodynamic processes are provided to PTM from CH3D and PTM includes all relevant sediment and dredging processes. For this application, PTM was used to simulate dredging operations representative of typical conditions for maintenance dredging. Model results from this application quantified deposition in possible winter flounder spawning habitat, primarily in shoals within Newark Bay. Results indicate that deposition in these habitat areas would be significantly less than the amount required to detrimentally impact spawning.