The course of the river flows through World Heritage listed high elevation rainforest, noted for its Antarctic Beech; and then through lower elevation subtropical rainforest, including trees such as Red Cedar and Small leaf fig.[3] Some of the River Oak growing beside the stream are over 50 metres (160 ft) in height. Logging has been practiced in the area since the 1820s.[3] In the middle course of the river, the geology includes sedimentary rocks such as the Allyn River Member.[4]
^ abAllyn River Visitor's Guide. Government of New South Wales. February 2000. {{cite book}}: |work= ignored (help)
^Roberts, J., Engel, B., Lennox, M., Chapman, J., 1991, Dungog, New South Wales 1:100 000 Geological Sheet 9233, Geological Survey of New South Wales. 1:100,000 geological sheet series, 1v, Map
^"Caergwrle, Allynbrook". Discover people and places. State Library of New South Wales. 2011. Archived from the original on 2 May 2012. Retrieved 13 May 2012.