Work has started on a £400,000 project to make homes safer in an area that has flooded three times in 30 years.
The five-month Environment Agency scheme will reduce the risk of flooding to homes in Send Marsh, near Guildford, from the East Clandon stream.
The most recent flood was in 2000, when 16 properties were flooded to a depth of 1m, causing £600,000 of damage.
The stream was diverted in the 1870s for brick-making and could revert to its original course when flooded.
Guildford Borough Council carried out works immediately after the 2000 incident and, although these measures have helped, Environment Agency experts believe an extreme flood could affect many more properties than before.
Flood risk manager Ian Tomes said: "I am delighted that after six years working on developing measures with the local community we are able to make a start on site."
But he warned: "Although the flood risk will be significantly reduced, it will not be eliminated, as living in a floodplain can never be without risk."