Drigg is an example of a small, bar-built estuary on the north-west coast of England. It is fed by three rivers (the Irt, Mite and Esk) which discharge through a mouth that has been narrowed by large sand and shingle spits. The sediments within the estuary are largely muddy within the Rivers Irt and Mite, while those of the Esk are more sandy, particularly towards the mouth. There is a substantial freshwater influence in the upper reaches of all three rivers, with good development of associated animal communities. Within the site are some of the least-disturbed transitions to terrestrial habitats of any estuary found in the UK.
Drigg represents Atlantic decalcified fixed dunes (Calluno-Ulicetea) in north-west England. There are substantial areas of the habitat type, showing a wide range of ecological variation. Some areas are dominated by heather Calluna vulgarisand bell heather Erica cinerea. Within the dry dune heath are wetter areas in which cross-leaved heath Erica tetralix is prominent. There are large areas of acidic dune grassland with a prominent lichen component and also areas where sand sedge Carex arenaria grows in carpets of the moss Racomitrium canescens.
Drigg contains a number of dunes with Salix repens ssp. argentea. These span a range of hydrological conditions from very wet to relatively dry. The slacks also grade into more acidic 2190 Humid dune slacks with some interesting intermediate types. This site is representative of dunes with Salix repens ssp. argentea in north-west England.
Annex I habitats present as a qualifying feature, but not a primary reason for selection of this site