The main flow into the estuary comes from the Ballyboghil River and its terminal tributary, the Corduff Stream.

It covers an area of 3.63 km2 (900 acres), and is divided by a causeway and bridge built in the 1840s to carry the main Dublin–Belfast railway line.

It is internationally recognised as one of the most important east coast sites and is vital for wintering wildfowl and waders and birds on passage.

The former Balleally landfill site located by the railway causeway was landscaped and reopened as Rogerstown Park in 2019.

[citation needed] The site is a statutory Nature Reserve and a candidate Special Area of Conservation under the E.U.