Suffolk Wildlife Trust's Carlton Marshes £5m expansion
Suffolk Wildlife Trust has spent £5m adding 484 acres (196 hectares) to its Carlton Marshes reserve near Lowestoft, Suffolk.
It said the new reedbed areas could absorb large amounts of water from surge tides, protecting properties.
Sir David Attenborough has called the project a "unique opportunity" for wildlife.
Matt Gooch, the trust's Broads sites manager, called it "habitat creation on a landscape scale".
The new areas lie between the River Waveney and the Oulton Dyke, which connects the river with Oulton Broad in Lowestoft.
But he said the landscaping could also provide run-off areas during surge tides, in which the river bursts its banks.
The creation of shallow wading areas is likely to lead to an immediate increase in bird numbers, such as spoonbill (pictured), said the Trust