The area was declared a NNR in 1987, covers an area of 83 hectares and consists of grass marshes on the north side of the River Thurne between Ludham and Potter Heigham.
The dykes which intersect the marshland are habitats for water soldier Stratoides aloides, whorled water-milfoil, water violet and fen pondweed. They also support waterfowl such as garganey and shoveler. The marshland themselves support birds such as redshank, lapwing, oystercatcher and snipe. In recent years, the dragonfly Norfolk hawker Aeshna isosceles has been attracted back to this area through specific management of the dykes.