TidesandCurrents
TIDES AND CURRENTS
Astronomical tides at Townsville range from 3.9 to 6.6 ft (1.2 to 2.0 m) during neap tides, and 1.3 to 9.5 ft (0.4 to 2.9 m) during spring tides (DMA, 1991). Mean sea level is 5.3 ft (1.6 m). The Port of Townsville Port and Shipping Directory explains that the smallest neap range, of about 1 ft (0.3 m), occurs about two days before the moon's third quarter. It further states: "The diurnal inequality of 0.9 meters chiefly affects high water, and is the largest when the moons declination is large and altogether absent when the moon is on the equator. When the sun has south declination the higher tides at springs occur during the day, and when in north declination, at night. Also when the sun is south, the higher tide of the Lunation is at new moon, and when north, at full moon. When Perigee occurs, about the time of a full or new moon, the tides are at the highest."
Local harbor authorities state that currents in the Entrance Channel are mainly influenced by the tides, and may pose a problem to ships navigating Platypus Channel. The flood tide sets west across the channel at velocities generally less than 1 kt. The strongest current noted is about 1.2 kt. The ebb tide current is negligible.
Source: http://www.nrlmry.navy.mil/port_studies/thh-nc/australi/townsvil/text/sect6.htm
