The catchment area of the river benefits from melting snow in spring. Gloucester district, although incredibly hot in the main summer months, nevertheless has an annual rainfall averaging 1,300 millimetres (51 in). As a result, combined with the merging streams and rivers, periodic serious flooding occurs in the Avon Valley at Gloucester, sometimes cutting all transport links.
The Gloucester River eventually flows into the Manning River, a major waterway which flows into the Tasman Sea through a minor delta east of Taree.
In 2004, assessments of water sampling done in 1997 by the NSW Environment Protection Authority, revealed poor water quality, with high levels of nutrients leading to excess algae. Along the river, downstream from Stratford, bank erosion and the invasion by exotic plant species have degraded the river.
^Hose, Grant; Turak, Eren. "Mann504 - Avon River downstream of Stratford". River Health in the New South Wales Lower North Coast, Hunter and Central Coast Catchments. Department of Environment, Water, Heritage and the Arts. Retrieved 24 January 2008.