Adele Morrison, 78, was last seen at a shopping centre in Gloucester after leaving home in Port Macquarie on March 16, as a one-in-100-year flood event began on the mid north coast.

Large tracts of NSW went underwater as rivers filled by torrential rain broke their banks.

Tens of thousands of people were evacuated across the state, with Sydney's Hawkesbury-Nepean Valley and the mid-north coast the hardest hit.

Ms Morrison's car was spotted in the swollen Barrington River on March 25.

On Saturday evening, a property owner along the river notified police after locating the body of a woman on the riverbank of his rural property in Barrington.

A crime scene was established and examined by specialist forensic police.

The body is yet to be formally identified but is believed to be that of the missing woman.

A report will be prepared for the coroner.

The discovery of Ms Morrison's body takes the death toll from last month's widespread flooding to two.

A 25-year-old man died in Glenorie in northwest Sydney on March 24.

The Pakistani national was on his way to his first day of a new contracting job when his car was trapped in flood waters at Glenorie in northwest Sydney.

Australian Associated Press