Historic West Country estates and popular beaches are among a list of National Trust properties at risk from sea level rise caused by climate change.
Detailed research by the trust, based on future weather patterns, has shown that "adaptation" strategies to cope with the threat are necessary at 15 sites across Devon and Cornwall.
The estate at Cotehele, which stands on the banks of the River Tamar in Cornwall and dates back to the 15th century, tops the trust's priority list which also includes Greenway, the former home of Agatha Christie on the River Dart.
The locations have been identified as part of a risk assessment project following the trust's Shifting Shores report which was published in 2005.
It aims to "work with, not against, nature" in managing trust land, given the risks of global warming, rising seas, more intense storms and greater coastal erosion.
"Our sense is that there is as much to be concerned about in the South West as there is elsewhere," the trust's coast and marine adviser, Phil Dyke, said. "What we are in the process of doing is developing an adaptation strategy for those places we are most concerned about.
"In terms of Greenway, the key issue to do with sea level rise is the impact on the link spans because we do get a lot of visitors who arrive by boat."
The quay at Cotehele, for hundreds of years the main access to the estate, was a thriving hub in the Victorian era. The buildings are currently home to an information centre and The Edgcumbe restaurant. The main road to the house has also been flooded in the past.
At Greenway, the early Victorian boathouse, a crime scene in Agatha Christie's novel Dead Man's Folly, could also be vulnerable.
Mr Dyke said the trust was assessing how such buildings were used, potentially moving more essential services out of harm's way as had happened on St Michael's Mount.
He said: "There is a question around the future time-scale of when those buildings will remain functioning and functional." Those assessments also include looking at essential infrastructure, such as sewage pumping stations and electricity sub-stations.
Mr Dyke said the trust was continuing to talk to the community near Cotehele about the flooding issues it faced.
More than a decade ago, it proposed breaching a flood defence system put in place in the 1800s to reclaim land for agricultural use. The Haymarsh scheme would have restored a reed bed and created an inter-tidal wetland habitat over some 50 acres.
The proposals, though, met with significant local opposition and they were finally abandoned in 2007 after modelling showed it would have taken "decades" to create the intertidal habitat, rather than ten years as originally thought.