HYDRODYNAMICS INFLUENCES ON MORPHOLOGICAL CHANGES TO SMALL REEF ISLANDS IN MALAYSIA: A CASE STUDY OF SIPADAN ISLAND Ejria Saleh (a*,b,c ) Jasica Chua (d), Farrah Anis Fazliatul Adnan (b), Rodeano Roslee (c), Justin Sentian (c)
a) Borneo Marine Research Institute, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia.
ejsaleh[at]ums.edu.my
b) Small Island Research Centre, Faculty of Science and Natural Resources. Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia.
c) Natural Disaster Research Centre, Faculty of Science and Natural Resources, Universiti Malaysia Sabah, Jalan UMS, 88400 Kota Kinabalu, Sabah, Malaysia.
d) GEOAQUAMATICS PLT, No. E-4-6, Lot 6, 4th Floor, Block E, Plaza Tanjung Aru, Jalan Mat Salleh, 88100 Kota Kinabalu, Sabah.
Abstract
The hydrodynamic processes of a reef island are driven by its surrounding tides, waves, and ocean currents. These processes are also influenced by the seasonal monsoons, which cause geomorphological changes to the island. The objective of this study is to determine the hydrodynamic patterns of the island during different monsoon seasons and to identify the influence of hydrodynamics on the morphology of the reef island. The hydrodynamic simulation model was conducted at Sipadan Island based on a complete tidal cycle, wind, and wave conditions using the Delf3D software. The model was calibrated using tidal data taken at Mabul Island in March 2018 and compared with the tidal simulation at Sipadan Island. The results showed that the tidal currents flow from the south to the north of Sipadan Island during high tide and in the reverse direction during low tide. Erratic current flow patterns were observed at coral reefs and seagrass areas. The wind and wave height patterns during different seasonal monsoons contribute to the geomorphological changes in the southern parts of the island, resulting in the formation of narrow beaches and severe beach erosion. However, the eastern part of the island experiences coastal accretion that promotes the growth of new vegetation. Without action to address eroding areas, the island is predicted to lose its existing mature trees. In the long term, the island appears to be shifting towards the east, which could impact the island^s stability. The findings will be valuable for coastal management and conservation efforts in addressing ongoing geomorphological changes.
Keywords: hydrodynamics, morphology, monsoon, reef island, Sipadan Island
