Study on siltation for implementation of the nautical depth concept in the port of cochin , india

The port of Cochin has the largest siltation rate among Indian ports: more than 20 million m3 per year. Siltation occurs mostly during the Monsoon (June-September) when both river discharges and ocean dynamics are high. The need for continuous maintenance dredging has serious budgetary impacts for the Cochin Port Trust (COPT). Therefore, COPT ordered a study to analyze the siltation processes and to assess the feasibility to implement the nautical depth concept. An extensive monitoring campaign, including measurements of waves, currents, tide, wind, salinity, bathymetry, sea bed composition, suspended sediment concentration and mud rheological properties is conducted during one year to cover the seasonal variation of hydrodynamic and morphodynamic processes. These data feed a numerical 2D/3D model to simulate hydrodynamics, wave transformation, tidal circulation, salinity, sediment transport and siltation processes in the harbor, the navigation channel and the surrounding areas. The Telemac platform is applied, including the Tomawac (waves) and Delwaq (sediment transport) modules. Understanding the physical processes of siltation will allow to suggest methods for arresting it. In order to investigate the nautical implications of a new nautical depth criterion in the Port of Cochin simulations are performed using a ship maneuvering simulator especially equipped for maneuvering in mud conditions in shallow ports (Flanders Hydraulics Research). This 3D nautical model contains visualization of the port infrastructure, signalization and the most important landmarks. A range of mud layer characteristics (density, viscosity and layer thickness) is selected based on the results of the monitoring campaign. Two pilots of the Port of Cochin operate a full mission bridge simulator to evaluate all relevant inbound and outbound maneuvers to the harbor at different bottom/mud conditions with the relevant vessel types. The simulations are analyzed based on both the assessment of the pilots and objective criteria such as application of rudder, propeller and tug boats. After assessing the feasibility for a nautical depth for the Port of Cochin, monitoring and maintenance methods are investigated as well as the implications for dredging.