Where are the world's largest tidal ranges?

There are several locations across the world with high tidal ranges. In this article, we'll explore two larges and find out what makes them so different. Before we do this, we need to know what a tidal range is.

What is a tidal range?

A tidal range is the difference between a high tide and its corresponding low tide in a given area (or vice versa). As we know, the moon has the biggest influence on the tide frequency and range, you can find out how the moon affects tide here, the largest tidal ranges occurring during spring tides. The spring tides, and therefore their effect on the tidal range is increased when a spring tide coincides with the equinox. This happens on Earth around 20 March and 23 September.

What other factors affect a large tidal range?

Large tidal ranges occur in coastal locations. Land formations and topology of the seabed affect tidal range, for example, bodies of water between two land masses funnel water, restricting their ability to dissipate, resulting in a large tidal range. The highest tidal ranges in such locations can see the difference between the rise and fall of 12m, wherein open water, this range is just 0.6m

Let's explore the highest tidal ranges in the world.

Largest tidal range - Bay of Fundy, Canada

Located between the landmasses of New Brunswick and Nova Scotia, the Bay of Fundy has an average tidal range of a staggering 16.3m (53ft). The entrance to the bay narrows, creating the natural bottleneck, resulting in a high range. The semidiurnal (where there are two high and low tides daily, read out about semidiurnal tides here) tide occurs in the Bay of Fundy 6 hours and 13 minutes apart.

The mouth of the bay sees 115 billion tonnes flow in and out of it twice a day. The highest tide ever recorded occurred in 1869. The Saxby Gale, a tropical cyclone hit the Bay of Fundy between 4th and 5th October killing at least 37 people. During the Saxby Gale, the water level rose to 21.6 m (71 ft).

Above is the tide times for the next couple of days for Ile Haute in the Bay of Fundy, Canada.

Second Largest tidal range - Severn Estuary, United Kingdom

Located between the landmasses of England and Wales, the Severn Estuary is the point at which the river Severn, Great Britain's longest river, flows into the Bristol Channel. The average tidal range for the Severn Estuary is 15m (50ft). As with the Bay of Fundy, the high tidal range in the Severn Estuary is the result of tidal funnelling by the English and Welsh landmasses.

The Severn Estuary experiences a phenominon called a Tidal Bore, where the rising tide moves into the Severn Estuary and the surging water forces its way upstream in a series of waves. The Severn Bore is popular with surfers, creating among the longest surfable waves in the world. Local man, Steve King holds the record of 7.6 miles (12.2km) of stand up surfing on the severn bore in March 2006.

A storm surge in January 2014 saw the tide reach 3.58m (11ft) higher than the mean average for the region.