Bounded on two sides by the River Waveney and Oulton Dyke Petos Marsh covers 80 hectares of agricultural land.
Original proposals to strengthen or setback existing floodbanks and to remove a short section of piling were not approved of by the landowner. Adjacent to Petos Marsh is Carlton Colville SSSI and Barnby Broad and Marshes SSSI. Both of these SSSIs form part of the Suffolk Wildlife Trust Carlton Marshes Reserve. Unable to construct the defences around the edge of Petos Marsh an alternative solution needed to be developed in order to continue to provide the level of defence these nationally important sites require.