NUMERICAL SIMULATION OF TIDAL CIRCULATION IN THE PICHAVARAM MANGROVE ESTUARY

Abstract

A vertically averaged numerical model is developed using the Surface water Modeling System (SMS) for the Pichavaram Mangrove Estuary to study the tidal characteristics which enables the simulation of the whole water circulation within the water body. The Pichavaram mangrove ecosystem is a complex network of creeks, mangroves and mud flats housed between the Vellar and Coleroon rivers, 15 km north of Chidambaram, Tamil Nadu, India. A portion of the Coleroon river drains into the mangroves, and tidal flow is through the Coleroon mouth and a small inflow from an inlet in the north. The reduction of freshwater flow over the years has led to a degradation of the mangroves and changes in sedimentation patterns. The results are calibrated against data collected previously. From the simulated results it is noticed that the tidal flow from the Coleroon mouth dominates the entire system. The maximum flood and ebb tide speed reached 0.777 ms-1 and 0.468 ms-1 during monsoon and post monsoon periods, respectively. The tide showed a pronounced asymmetry in mangroves and a 12% increase in total depth of water with a maximum increase in water level of about 5 cm is noticed between monsoon and post monsoon conditions. The dominance of ebb tide is noticed due to friction in the mangrove forest, which has resulted in slower flood current and greater tidal asymmetry in the waterway.