Coastal Erosion at Tanjong Piai, Johor, Malaysia

Tanjung Piai, Johor, Malaysia, is a ramsar site, located at the southern-most tip of mainland Asia, and consists mainly of mudflats and mangrove forests. The coast has experienced severe erosion for several decades, in spite of the construction of various coastal defense structures. The reported rates of shoreline retreat were between 2 to 4 m/year. Hydrodynamic modeling using 2008 field data indicate that the maximum current speed observed along the east coast of Tanjung Piai ranges from 0.2 - 0.5 m/s, while the west coast experiences lower current speeds of less than 0.2 m/s. Strong currents occur at the tip of Tanjung Piai with a speed of 0.5 to 0.8 m/s. The simulation also indicates that some local current patterns are formed near the tip due to the presence of a small island as the flow entering the study area during flooding were reflected to the east while the flow during the ebb tide tend to move toward the opposite direction. Wave simulations show that most of the waves come from Singapore and the Straits of Malacca, with amplitudes of over 1.5 m, are reduced to less than 0.8 m as they travel towards Tanjong Piai coast. These local hydrodynamic conditions, combined with the existence of regular ship wakes, are believed to be the reason for the intensive erosion at Tanjung Piai. Model simulations incorporating the proposed coastal protection measures indicated positive and negative impacts of the hydrodynamic changes around the study area. The results shown that the magnitude of the current speed and wave height would be reduced in the area behind the structures but slightly increased on the other parts of the coast. These changes will determine the sediment transport movement in the area. Therefore, it is necessary to understand the hydrodynamic characteristics before implementing any kind of coastal protection measures because they may protect some area from erosion, but may not be favourable to the other parts of the coast.