Sediment pattern & rate of bathymetric changes due to construction of breakwater extension at Nowshahr port

Abstract

Erosion, scour and sedimentation are the most common phenomena which should be considered in the design of marine structures. Seas and oceans are dynamic environments, hence studying them in more details, gathering more information about their bathymetric changes and pursuing their historical evolution could be beneficial in the efficient design of marine structures such as: jetties, groins and breakwaters. To achieve this goal one desperately needs to know about currents and waves and the effects of their interactions as well as the rate of sedimentation (Net Gain), and erosion (Net Loss) in the field. On the other hand, to obtain a sufficient depth to facilitate marine traffics in the harbors the rate of sediment deposition must be calculated, offering effective annual dredging programs. In this research the pool of Nowshahr port and some parts to the east and west were modeled. Sediment transport direction was compatible with the counter-clock-wise circulation of the Sothern part of Caspian Sea. Wind data, water surface elevation, and hydrographic points from the bathymetric surveys applied in the hydrodynamic module of Mike 21 and the output of the hydrodynamic module (HD) were used as inputs for sediment transport module (ST). The result of the ST module shows that the main direction considering dominant waves is from northwest of the Caspian Sea to the southeast. Also, net rate of sediment transfer is from west to east. By approaching to the main breakwater arms from the west side sediment transport rate decreases which means deposition occurs behind the western arm.