Duchess Gully

Our water quality monitoring program has shown Duchess Gully to have good water quality. Find out more about the estuary and its unique features.

Duchess Gully estuary is situated on the mid-north coast of New South Wales, in Bonny Hills.

Duchess Gully is a small coastal creek with an intermittently open entrance. The estuary is tucked in behind beach dunes, draining an area subject to new urban development.

Estuary health and features

Water quality

As part of our water quality monitoring program we assess the water quality and ecosystem health of an estuary using a range of relevant indicators. We sample a subset of the estuaries located between the Queensland border and Taree every 3 years. The most recent sampling in Duchess Gully was completed over the 2018–19 summer when 2 sites were sampled on a monthly basis.

Duchess Gully water quality report card for algae and water clarity showing colour-coded ratings (red, orange, yellow, light green and dark green, which represent very poor, poor, fair, good and excellent, respectively). Algae is rated 'fair' and water clarity is rated 'good' giving an overall rating of 'good' or 'B'.

This report card represents 2 water quality indicators that we routinely measure: the amount of algae present and water clarity. Low levels of these 2 indicators equate with good water quality.

The report card shows the condition of the estuary was good with:

  • algae abundance graded fair (C)
  • water clarity graded good (B)
  • overall estuary health graded good (B).

Find out more about our estuary report cards and what each grade means. Read our sampling, data analysis and reporting protocols and find out how we calculate these grades.

We have monitored water quality in the Duchess Gully since 2012. This table shows the water quality grades for this estuary over that time.

Duchess Gully historic water quality grades from 2012-13 for algae and water clarity. Colour-coded ratings (red, orange, yellow, light green and dark green represent very poor (E), poor (D), fair (C), good (B) and excellent (A), respectively).

Grades for algae, water clarity and overall are represented as:

  • A – excellent
  • B – good
  • C – fair
  • D – poor
  • E – very poor.

Physical characteristics

Estuary type: Creek

Entrance
location 		Latitude (ºS) –31.59
Longitude (ºE) 152.84
Catchment area (km2) 10.6
Estuary area (km2) 0.02
Estuary volume (ML) 5.4
Average depth (m) 0.2
Notes: km2 = square kilometres; m = metres; ML = megalitres.

Water depth and survey data

Bathymetric and coastal topography data for this estuary are available in our data portal.

Land use

The catchment of Duchess Gully is highly disturbed. The lower estuary flows through an area of coastal bushland, but over half of land within the catchment is used for urban areas and associated cleared grazing land. A wastewater treatment plant is located along the creek.

National and marine parks

Community involvement

  • Bonny Hills Landcare forms part of the Hastings Landcare umbrella group. Persistent work over many years has significantly reduced weeds and allowed local native plant species to regenerate on the headland and dune areas around Duchess Gully.
Duchess Gully

Local government management

Local councils manage estuaries within their area unless the estuary is attached to a marine park. Duchess Gully estuary is managed by Port Macquarie–Hastings Council.