Itchen River flow restricted to prevent flooding to Winchester
Giant sandbags have been placed in the River Itchen by the Environment Agency to slow its flow into Winchester and prevent flooding to 100 properties.
Part of the M3 was shut overnight while a crane hauled 30 one-tonne bags into the river at Easton, north of the city.
The agency said it would cause about 300 acres of land to flood up to 4ft (1.2m) deep in water.
Mike O'Neill of the agency said: "Our engineers are trying to come up with novel solutions to reduce flooding."
Livestock that had already come under threat as the river burst its banks earlier in the week have been moved to higher ground.
Easton resident Duncan Gray, whose land will become flooded, said: "We have never seen river levels like this before.
"Once in a blue moon you have to accept events like this, I have to applaud the action of the Environment Agency."
More bags were expected to be distributed into the river overnight.
The river level at Easton is currently at 1.18m (3ft 10ins). The Environment Agency said its typical level range is between 51cm (1ft 8ins) and 1.10m (3ft 7ins).
Soldiers have laid hundreds of sandbags along the river bank at Water Lane in Winchester to raise its height and help secure the flooding threat to homes.