Situated in the south-central portion of the province, along the north shore of the Bay of Fundy at the mouth of the St. John River, the city is split by the south-flowing river and the east side is bordered on the north by the Kennebecasis River where it meets the St. John River at Grand Bay.
The St. John River itself flows into the Bay of Fundy through a narrow gorge several hundred feet wide at the centre of the city. It contains a unique phenomenon called the Reversing Falls where the diurnal tides of the bay reverse the water flow of the river for several kilometres. A series of underwater ledges at the narrowest point of this gorge also create a series of rapids.
The topography surrounding Saint John is hilly; a result of the influence of two coastal mountain ranges which run along the Bay of Fundy – the St. Croix Highlands and the Caledonia Highlands. The soil throughout the region is extremely rocky with frequent granite outcrops. The coastal plain hosts numerous freshwater lakes in the eastern, western and northern parts of the city.
In Saint John the height difference from low to high tide is approximately 8 metres (28 ft) due to the funnelling effect of the Bay of Fundy as it narrows. The Reversing Falls in Saint John, actually an area of strong rapids, provides one example of the power of these tides; at every high tide, ocean water is pushed through a narrow gorge in the middle of the city and forces the St. John River to reverse its flow for several hours
