It’s early morning in the year 867AD; a Viking Chieftain is venturing up the River Trent towards Nottingham, leading a small fleet of longboats, when he hears a slow rumbling noise behind him. He peers over his shoulder and catches sight of a faint ripple on the water in the distance, slowly growing bigger as it comes towards him, the edges sloshing up the muddy banks. He and his fellow comrades row as hard as they can but there’s no escaping the invisible leviathan as it lifts his craft and surges past him, leaving a trail of small waves and a band of bewildered Vikings in its wake.
Back then it would have been easy to believe this phenomenon was the wrath of a Norse God, but today we know it as a tidal bore – the Trent Aegir – believed to have been named after the king of the sea in Norse mythology. Some believe the name to derive from the Latin word augarium, meaning ‘omen’ or ‘prophecy’, while others think it derives from the French eau guerre or ‘water war’ for the way the wave travels up the river like a wall of water.
Despite manmade constraints such as weirs and dredging lessening its power, the Aegir is still an unstoppable force of nature. It occurs on the lower tidal reaches of the Trent when a high spring tide from the Humber estuary meets the downstream flow of the river. The funnel shape of the river mouth exaggerates the effect, causing a tidal wave of up to 1.5m to travel as far as Gainsborough at around 10mph.
High tides occur during full moon or new moon phases, when the gravitational force of both the sun and moon reinforce one another. Large annual tides occur around the Spring Equinox in March and Autumn Equinox in September, reinforced by full or new moon phases, creating the highest bore waves.
Top fact: Some sources claim that it was here, on the banks of the River Trent at Gainsborough, that King Canute performed his intentionally unsuccessful attempt at turning the tide. In order to prove to his sycophantic courtiers that he didn’t have divine powers, the 11th-century king commanded the oncoming bore to halt, and ended up with rather wet legs.
See the Trent Aegir:
The phenomenon occurs between Derrythorpe and Gainsborough, and the best places to see it are at Morton, East and West Stockwith and Owston Ferry in Lincolnshire. Visit the Environment Agency’s Facebook page https://www.facebook.com/environmentagency?_rdr=p, which publishes predictions of Aegir times and rates its strength from one to five stars.