Outer Trial Bank: UK 'Doughnut' Island Worth £3 million, Built as Tidal Barrage Now Being Abandoned

A doughnut-shaped island off the coast of England, United Kingdom, built as a tidal barrage several decades ago has been abandoned.

The initial construction of the doughnut island called Outer Trial Bank is one of the two islands, with the other called Inner Trial Bank, was halted by the UK government. Its purpose was to capture freshwater but it was deemed to be inefficient and expensive.

Trial Bank Islands

The failed engineering project of the 1970s surrounding the Trial Bank islands is still visible today in the waters of the Wash, a rectangular bay with multiple estuaries located off the East coast of England. The so-called "two test islands" served to investigate the quality of water constructed on the former seabed.

In 1972, the British government spearheaded the ambitious plan of the Trial Bank Islands, with the idea to build not only a tidal barrage but also a power station and freshwater reservoir to capture the outflow current coming from the river Nene, according to the travel company Atlas Obscura.

It did not take long for the project to push through when the construction started in 1975. The test cost was £3 million but the government determined the project was both "costly and impractical" since the central reservoir became salty and silty, the travel company said.

Based on recent reports, the once promising donut island was completely abandoned.

What is a Tidal Barrage System?

A tidal barrage is like a dam but with turbines at the bottom of its reservoir. The said structure creates a barrier between the sea and the tidal basin to produce power. The tidal barrage system involves the use of gates which regularly opens and closes to control the flow of water and utilize power generation, according to the University of Strathclyde in Glasgow, Scotland.

With these, tidal barrages are a feat in hydraulics engineering but with numbers not as many as dams and other related artificial structures. This is according to the said Glasgow university, which says that there are several proposed tidal barrage schemes worldwide but only a few of them have come to fruition.

A tidal barrage is ideally installed across the inlet of an ocean bay or lagoon that serves as a tidal basin. According to the US Energy Information Administration, tidal power has a potential disadvantage since tidal station can have negative impact on animals and plants in estuaries connected to tidal basins.

While tidal barrages are not as popular as dams, the latter has been deemed by some scientists and conservationists alike to be detrimental to fish and other marine creatures.

In recent years, a dam removal project is underway across the US with the aim of restoring natural habitats; since the large structures, sometimes called "river barriers" can block the pathway of foraging, and mating freshwater organisms.