Flowing east, the Humber is one of Britain’s largest estuaries,  fed by several major rivers (Trent, Don, Aire, Ouse and Hull). The Humber NCA is located at the north of Greater Lincolnshire. The Humber NCA, including the tidal estuary, is responsible for draining one fifth of the area of England into the North Sea. Extensive stretches of intertidal and coastal habitats have formed along the estuary including intertidal mudflats, saltmarshes and tidal reedbeds. These provide essential habitats for large numbers of overwintering, migratory and breeding birds and migratory lamprey populations and contribute to the international importance of the Humber Estuary as part of the ‘East Atlantic Flyway’. The Humber Estuary is designated as Ramsar, Special Protection Area (SPA), Special Area of Conservation (SAC) and Site of Special Scientific Interest (SSSI). The NCA is also known for its unique blow wells, which can be habitat for the elusive crystal moss animal.

Much of the landscape is flat and low lying, with some small areas of rising land on both sides of the estuary, where the chalk ridge, forming the Lincolnshire Wolds to the South and Yorkshire Wolds to the North, cuts across it.

More intensive agricultural practices and industrial expansion have resulted in declines in grassland habitats in the NCA.