The Derwent estuary extends from the rural river town of New Norfolk south to the Iron Pot lighthouse.
The estuary is a unique environment; a partially enclosed body of water where tidal seawater and fresh river water mix. The sheltered waters of the estuary support unique habitat and species specifically adapted to life in this environment.
What we recognise today as the Derwent estuary was formed between 6,500 and 13,000 years ago when the sea level rose flooding a river valley.
Today, wetlands and shallow mud flats dominate the upper Derwent estuary, north of the Bowen Bridge. The middle estuary has a convoluted shoreline with numerous small bays and inlets. Below the Tasman Bridge there is a single large bay - Ralphs Bay - to the east and on the west a relatively straight shoreline scattered with cliffs and beaches.
There are 17 reserves in the Derwent estuary, including:
- Derwent River Conservation Area - the largest reserve on the estuary including most of the wetlands and mudflats north of Dogshear Point.
- East Risdon State Reserve - perhaps the most healthy piece of remnant foreshore bush, this reserve includes the endangered tree species Eucalyptus risdonii and E. morrisbyi. These species are both found only on Hobart's eastern shore.
- Goulds Lagoon Wildlife Sanctuary - a remnant wetland listed on the Directory of Important Wetlands and open to the public for bird watching.
- Tinderbox Marine Reserve - protecting a great variety of seaweeds, fish and invertebrate animals, and including Tasmania's only underwater snorkel trail.
- Ralphs Bay and South Arm reserves protecting important salt marsh and wading bird habitat.