A hole has appeared behind the end of the German wall at the eastern side of L'Ancresse, near the slipway.
The States of Guernsey has fenced the area off, and work will start next week to fill it.
Under the latest States resolution, Environment and Infrastructure are to keep repairing the crumbling World War Two defence work for a number of years.
A £150,000 repair plan was agreed in April.
Members of the public are being asked to avoid the area and not pass the barriers.
Airport webcam to help Guernsey taxi drivers
Real time pictures of customer demand outside the arrivals door at Guernsey airport seeks to cut taxi waiting times.
Guernsey's Lieutenant Governor joins Year 7s planting a tree
Theo Curle and Alexander Murray campaigned for their school, Blanchelande College, to plant a tree to symbolise the importance of protecting the planet.
Guernsey taxi fares rise by 4.75%
Taxi fares in Guernsey rise from today (25 November). Environment & Infrastructure estimates it will put 40p on an average, two mile, daytime journey.
Police looking for person in connection with Northside Chip Shop damage
Guernsey Police have released an image of a person they would like to speak to about an attack on Northside Chip Shop.
Guernsey passengers can book ferries from next Tuesday
Bookings for ferry sailings from Guernsey from late March 2025 will go on sale next Tuesday (26 November) following approval of Brittany Ferries and Condor's new 15 year contract.
Car fires to floods: Guernsey Fire and Rescue attend 24 bad weather incidents
Fires, floods and flying roof tiles... Guernsey Fire and Rescue dealt with an 'unprecedented number of incidents' yesterday morning (21 November).
