The Haisborough, Hammond and Winterton site lies off the north east coast of Norfolk, and contains a series of sandbanks which meet the Annex I habitat description ‘Sandbanks slightly covered by sea water all the time’. The central sandbank ridge in the site is composed of alternating ridge headland associated sandbanks (Dyer & Huntley, 1999). This ridge consists of the sinusoidal banks which have evolved over the last 5,000 years, originally associated with the coastal alignment at the time that the Holocene marine transgression occurred (Cooper et al, 2008). The bank system consists of: Haisborough Sand, Haisborough Tail, Hammond Knoll, Winterton Ridge and Hearty Knoll. Hewett Ridge and Smiths Knoll form an older (~7,000BP) sequence of sandbank ridges located along the outer site boundary. Inshore are the Newarp Banks and North and Middle Cross Sands which lie on the south west corner of the site. These banks are believed to be geologically recent, their genesis dating to around the 5th Century AD (Cooper et al, 2008).
Sabellaria spinulosa reefs are located at Haisborough Tail, Haisborough Gat and between Winterton Ridge and Hewett Ridge. They arise from the surrounding coarse sandy seabed to heights of between 5cm to 10cm. The reefs are consolidated structures of sand tubes showing seafloor coverage of between 30 per cent to areas where reef occupies 100 per cent of the sediment. Some parts of the reefs appear to be acting as sediment traps, with exposed tube height accordingly reduced within the core parts of reefs.