STATE of the art flood warning measures on Portland will be unveiled and tested this Friday.

The Environment Agency has finished installing illuminated signs at Chiswell that display messages from a control room in Blandford.

The signs aim to give motorists and residents in the area early warnings about floods and road closures on the island.

There will also be the annual test of Chiswell's flooding siren to ensure nearby residents can hear it and a mobile flood exhibition will be open to the public in the Brandy Row car park from 9am to 2pm.

Agency employees at the mobile exhibition will offer advice and information to people about the new measures, known as Flood Warning Direct.

The new message boards that form part of the scheme have been erected at the roundabout at Wyke Regis facing Portland, at the Masonic Hall car park in Chiswell and at the Portland Heights Hotel.

Experts estimate around 170 homes on the island are at risk of flooding from the sea.

The new signs were erected with the help of the police and highways agency and can display a variety of messages.

Environment Agency spokeswoman Sarah Comely said: "We've tested the new roadside signs for the first time and they are fully operational.

"We are keen to improve our flood awareness service to the residents of Chiswell and look forward to hearing their comments on Friday." Chiswell residents have been coping with floods for centuries.

In February 1972, Victoria Square was turned into a scene of mud and desolation' after a flood.

Gale force winds had brought the island to a standstill after the only road out was completely cut off. Portland also suffered flooding in 1981, 1971 and 1953.

Other records show severe flooding that rose to more than 18ft near Chiswell at the Abbotsbury Swannery in 1824.

The Environment Agency said that the earliest example of flooding found in the county took place at Sturminster Marshal in the 1200s.

An account of the flood says a mill was washed away.