Highest Astronomical Tide

The highest high tide is referred to as the Highest Astronomical Tide (HAT), and is defined as the highest level which can be predicted to occur under average meteorological conditions and any combination of astronomical conditions.

In Australia HAT is calculated as the highest level from tide predictions over the tidal datum epoch (TDE), this is currently set to 1992 to 2011.
The HAT and the Lowest Astronomical Tide (LAT) levels will not be reached every year. LAT and HAT are not the extreme water levels which can be reached, as storm surges may cause considerably higher and lower levels to occur.

See Tidal Range

The Highest Astronomical Tide (HAT) has been determined at places where there has been an operational tide gauge at some point in time. Generally HAT is well defined at Standard ports where there is or has been a long term tide gauge.

Queensland HAT

Site	Highest Astronomical Tide (HAT)	Reference level (datum)
Gold Coast Seaway	1.91	LAT
Brisbane Bar	2.73	LAT
Mooloolaba	2.17	LAT
Noosa Head	2.28	LAT
Waddy Point (Fraser Island)	2.37	LAT
Urangan	4.28	LAT
Bundaberg (Burnett Heads)	3.67	LAT
Gladstone	4.83	LAT
Port Alma	5.98	LAT
Rosslyn Bay	5.14	LAT
Hay Point	7.14	LAT
Mackay Outer Harbour	6.58	LAT
Bugatti Reef	3.50	LAT
Shute Harbour	4.33	LAT
Bowen	3.73	LAT
Abbot Point	3.60	LAT
Cape Ferguson	3.84	LAT
Townsville	4.11	LAT
Lucinda (Offshore)	3.96	LAT
Clump Point	3.62	LAT
Mourilyan Harbour	3.50	LAT
Cairns	3.50	LAT
Port Douglas	3.36	LAT
Leggatt Island	3.40	LAT
Thursday Island	3.86	LAT
Goods Island	4.07	LAT
Booby Island	4.31	LAT
Weipa (Humbug Point)	3.38	LAT
Karumba	4.88	LAT
Mornington Island	3.87	LAT

Resources:

HAT for Queensland is from: http://www.msq.qld.gov.au/Tides/Tidal-planes © The State of Queensland (Department of Transport and Main Roads) 2016.