The Heritage Lottery Fund (HLF) awarded the cash for the project, A Forgotten Landscape, which involves the Levels between Avonmouth and Lawrence Weston.
The ferry at Aust, the two Severn bridges and the community railway from Temple Meads to Severn Beach are also within the project’s scope.
It will begin in January.
The Levels once formed part of the wider Somerset and Avon Levels, but over the centuries they have become cut off by the expansion of the city of Bristol, industrial development in Avonmouth, and motorway construction.
The project, which is expected to take three-and-a-half years, will restore wildlife habitats across the area, which has an array of wetlands, hedges, wildflower grassland and orchards.
Private and public organisations will work on the project, hosted by South Gloucestershire Council.
Savita Custead, who chairs the Landscape partnership, said: “It is a beautiful and distinctive landscape with a long, fascinating history of human interaction with it and the funding will ensure that both local communities and visitors to the area can help conserve, enjoy and learn about the area’s rich heritage.”
There will be volunteer programmes, wildlife identification classes, and training in traditional skills, such as coppicing, pollarding and hedge-laying.
Traditional practices, such as salt marsh-grazing and cider-making, will be promoted.
Nerys Watts, head of the HLF South West, said such projects were particularly important because they brought together “community groups and public bodies with a shared passion of caring for our incredible natural environment”.