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.
Prominent Guernsey man appointed Commissioner for Standards
Architect and long-time community stalwart Andrew Ozanne will oversee any interim complaints about politicians.
Record festive parcel delivery for Guernsey Post
Christmas parcel volumes are up 2% on last year at more than 700,000 individual items.
Channel Islands Ferry Operators Working Group expands
DFDS and the States of Jersey have confirmed their interest in joining the Ferry Operators Working Group to improve sea travel between Guernsey and Jersey.
Sculpture to remember the Alderney evacuees
Fundraising is underway for a permanent memorial to the Alderney evacuees who never made it home after the war.
Channel Islands could technically have a White Christmas
Wintry showers are predicted for 25 December 2025 and if just one snowflake is recorded, the islands will technically have a White Christmas.
Flu cases in Guernsey 'creeping up'
The island's Director of Public Health says cases are climbing and urges people to take measures to slow down infection.
CI ferry operators to work together to improve inter-islands travel
A 'Ferry Operators Working Group' has been set up to improve sea travel between Guernsey and Jersey.
Talks ongoing to enable Guernsey ferries to access St Malo
Major port improvement work next year will mean there is only one ramp available for all ferries to use.
