A new wall is to built to protect a railway line that washed into the sea in 2014.
Up to £80 million of Government funding will be made available for the project in Dawlish, Devon.
The structure will be 2.5 metres higher than the existing five-metre tall wall to increase protection to the railway from waves during adverse weather.
Construction is expected to begin in the spring and completed by 2021.
The line, which is used by Great Western Railway and CrossCountry, has since proven susceptible to flooding, forcing services to be suspended on multiple occasions.
Transport Secretary Chris Grayling said: “We cannot allow the disruption and damage endured by Dawlish and the South West to happen again.
“This significant investment demonstrates our cast-iron commitment to delivering a resilient and safe railway, giving passengers, businesses and residents confidence in a reliable service.
The project is part of a £2 billion Government investment to support growth in the South West.
Network Rail is continuing to use a previously-announced £15 million fund to design a long-term solution to protecting cliffs in the coastal area.
Luke Pollard, Labour MP for Plymouth, Sutton and Devonport, said: “It’s taken five years to get ministers to announce the cash for only two-thirds of the upgrades we need at Dawlish.
“The final phase to steady the cliffs remains unfunded.
“It should not have taken years to get only £80 million when ministers are spending billions on new Tube lines for London and HS2 for the Midlands and the North.
“Labour has pledged £2.5 billion to upgrade our train line.
“But with a region stuffed full of Tory MPs why has it taken five years to not even get the full funding that we need from this Government?
“It’s time we got our fair share of funding to make our train line genuinely faster and more resilient.”