Sedimentation process of suspended matter in Manila Bay supplied from Pampanga River, Pasig River and open ocean is investigated using a three-dimensional numerical model which includes tidal current, residual flow and current due to wind waves. The calculation results well reproduced the major characteristics of the observed sedimentation patterns of silt and clay. The calculation results reveal that the seasonal variability of deposited clay distribution is larger than that of silt in Manila Bay. The area that cysts can accumulate is discussed with the use of the calculation results of clay
