At least €230 million needs to be spent protecting parts of the rail line between Dublin and Wicklow from falling into the sea.
Irish Rail says in the last 20 years there have been more storm events than there have been in the last century, increasing erosion.
Assessments by the transport company have found the infrastructure works are needed along parts of the south Dublin Dart line that runs to Wicklow.
The Irish Times reports some of the most vulnerable sections are around Dalkey and Killiney, sections between the Merrion Gates and Dun Laoghaire Harbour and Bray Head and Greystones.
Irish Rail says wave "overtopping" onto the tracks and "track washout" where the sea has eroded the land under the line have increased in the last 20 years - and that if action isn't taken the track would be at risk in certain sections within a decade.
A contract's been awarded to an engineering firm to carry out the preliminary design and environmental assessments ahead of planning applications for the works being lodged.