Long term morphodynamic evolution of Kakinada bay using upscaling methods

Abstract

Kakinada Bay has evolved over the last century dynamically by the action of wind, waves, tides and currents. Formation of Hope Island and development of Coringa Mangroves are attributed to the hydrodynamic 'forcings' and sediment dynamics. This study aims to predict the future morphological development of Kakinada Bay for next 100 years. The morphological model was built up in the DELFT 3D package. Model setting parameters were fixed after analysing their effect on the simulation results. For reducing the computational time and effort for simulating long term morphological development, upscaling methods such as morphological acceleration factor (MORFAC) and morphological tide were incorporated in the morphological model. Morphological tide was formed using tidal constituents - M2, O1 and K1. The MORFAC value for this study was chosen as 30 after undergoing the sensitivity test analysis using Brier Score Skill (BSS) Score. The model was run for 19 years for hindcasting and 100 years for forecasting. In order to establish confidence in the model, it was calibrated and validated using hindcast modelling. The hindcast simulation results were used to match the simulated shoreline with satellite observed shoreline from year 1988 to 2000, and 2006 to 2013 and the results were in good agreement. It was observed that the south-western part of the bay has accreted more rapidly while south-eastern part of the bay has undergone slight erosion. Thereafter long term morphological model was run for 100 years to predict the future evolution of bay. Results of these simulations show the capability of the long term morphological model to predict the spatial and temporal geo-morphological changes.