A vessel can transmit current loads through mooring lines into the pontoon. For catamarans, houseboats and ferries, projected area can matter as much as displacement.
Northern WA, NT and QLD projects should explicitly address the applicable wind region, storm tide, debris and operational cyclone plan. "Cyclone area" cannot be solved only by thicker aluminium. The complete system includes piles/anchors, gangway, shore structure, vessel evacuation and water level range.
Mean spring tidal range at Queensland standard ports
Heights above Queensland Port Datum (LAT 1992). Bars span mean low water springs to mean high water springs.
Show the data
Port
MLWS (m)
MHWS (m)
Spring range (m)
HAT (m)
Gold Coast Seaway
0.16
1.47
1.31
1.97
Mooloolaba
0.30
1.70
1.40
2.21
Cooktown
0.75
2.45
1.70
3.28
Brisbane Bar
0.42
2.22
1.80
2.78
Mourilyan Harbour
0.88
2.71
1.83
3.58
Cairns
0.82
2.67
1.85
3.57
Bowen
0.73
2.88
2.15
3.77
Lucinda (Offshore)
0.85
3.04
2.19
4.06
Weipa (Humbug Point)
0.77
3.01
2.24
3.33
Bundaberg (Burnett Heads)
0.61
2.94
2.33
3.68
Townsville
0.83
3.17
2.34
4.22
Shute Harbour
0.58
3.35
2.77
4.39
Urangan
0.73
3.54
2.81
4.33
Gladstone
0.77
4.01
3.24
4.87
Karumba
0.42
3.91
3.49
4.85
Rosslyn Bay
0.67
4.28
3.61
5.21
Port Alma
0.93
4.98
4.05
5.96
Mackay Outer Harbour
0.79
5.35
4.56
6.62
Hay Point
0.99
5.86
4.87
7.18
A gangway that is comfortable at Gold Coast Seaway is solving a 1.31 m problem. The same gangway at Hay Point is solving a 4.87 m one — which is why gradient has to be checked against the range at your site, not a national average.Source: Maritime Safety Queensland — Semidiurnal Tidal Planes 2024. Tidal Datum Epoch 2010–2029. 264 locations published; 19 standard ports shown. Retrieved 2026-09-12.
