Officials have discovered holes of more than 50 metres deep in the Oosterscheldedam, part of a massive complex of flood defences protecting the south west of the Netherlands from the sea, the Telegraaf reports on Wednesday.

The holes have emerged in protective mats on the sea bed at both sides of the dam, the paper says.

This means the sea defences will eventually be at risk. The Telegraaf bases its claim on information from Zeeland province’s infrastructure department.

The dam is part of the massive Delta Works project, developed to protect Zeeland from the sea since the devastating floods of 1953.

Erosion

Province experts say that to ensure the sea defences continue do their job measures need to be taken to prevent ‘further subsidence, erosion, movement or damage’ of the sea bottom on both sides of the dam.

However, the transport and infrastructure ministry said the provinces assessment of the situation is ‘not correct’.

The stability of the storm surge barrier is not under threat. ‘This is a natural process which we are monitoring closely,’ a spokesman told the Telegraaf.

The nine-kilometre long Oosterschelde barrier was opened in 1986. Most of it is a dam, but sluice gates were installed in four kilometres of the structure to preserve the marine life behind it.