Great Sandy Strait catchment story – Susan River

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• Susan River
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Transcript

The Susan River flows into the Mary River just upstream of the mouth, and has an extensive estuary that provides valuable habitat for a diversity of fishes. The catchment is generally flat and low-lying with soils that support numerous small wetlands. The catchment is important to the Butchulla people. Land use is mostly grazing, together with residential and associated services, conservation and natural areas, forestry and irrigated cropping (sugar).

The catchment story for the Susan River is available here (see transcript below). Please note that this catchment story will open as a map journal in a new tab, and you can come back to this map series to view the other catchment stories in the other tabs.

Main image. Grazing on native pastures and farm dam, Bunya Creek subcatchment, Photo by Department of Environment and Science, Queensland Government.

Susan River – Map Journal Transcript

The Susan River has an extensive estuary that provides valuable habitat for a diversity of fish species, and is a declared fish habitat area. The catchment is generally flat and low-lying with mostly highly weathered sandstone-derived soils, with pans of clay (and potentially ferricrete) beneath the surface that provide local perching capacity as aquitards and support the development of numerous small wetlands. Soils in most of the catchments are of marine origin, resulting in elevated soil salinity and areas prone to scalding when cleared. Land use is mostly grazing on native pastures, together with residential and associated services, conservation and natural areas, forestry, irrigated cropping (sugar) and other farming (pineapples).

Main image. Grazing on native pastures and farm dam, Bunya subcatchment, Photo by Department of Environment and Science, Queensland Government.

Table of contents

1. Introduction
2. First Nations peoples
3. Modified features—infrastructure, dams, weirs and bores
4. Modified features—sediment
5. Water quality
6. Water flow
7. Vegetation
8. Vegetation clearing
9. The subcatchments
10. Upper Susan subcatchment
11. Stockyard subcatchment
12. Bunya subcatchment
13. Lower Susan subcatchment

Introduction

• The Susan River is the largest of several waterways that flow largely unconstrained into a large estuary north of the Mary River entrance and adjacent to the Great Sandy Strait.
• The Susan catchment is within the southern part of the Maryborough sedimentary basin, where folding has forced up anticlines* and deformed its layering.
• Gently undulating to flat catchment, mostly below 20 metres above sea level (ASL), enabling tidal waters to extend well up into the tributaries, with headwaters up to 60 metres.
• Several anticlines of the Maryborough Formation extend north-west to south-east as hard ridges, bisecting the catchment at Halfway Hill, and bounding it to the east at River Heads.
• In the upper catchment, between these folds, are elevated plains and hill crests that are remnants of a deep weathered surface, resulting in extensive duricrust (aluminium and iron oxides).
• To the north, a series of low hills of volcanic basalt have extruded through the sedimentary layers.
• Average annual rainfall of approximately 1,001 to 1,201 millimetres per year.
• Geology is dominated by ferricrete and arenite-mudrock (Maryborough Formation and Burrum Coal Measures), together with smaller areas of basalt and rudite, in the upper parts.
• The lower parts are dominated by alluvium associated with the creek lines and miscellaneous unconsolidated sediments (marine muds).
• Within the Maryborough Basin, groundwater recharges to the west in the older, elevated geologies and discharge to the east in flatter, permeable geologies and through fractured rocks, such as those in the Susan catchment.
• The Maryborough Formation and rudite are largely impervious and do not provide for groundwater infiltration (aquitards), water flows laterally into drainage lines.
• Groundwater within the Susan catchment generally recharge in the upper parts, seeping into the drainage lines, which support GDEs such as melaleuca wetlands; the lower parts are groundwater dependent through the alluvium.
• The more porous Burrum Coal Measures, alluvium and basalt provide for water infiltration, where not developed, and the ferricrete provides for some local water infiltration.
• Several small patches of basalt occur in the north where groundwater expresses as springs at their footslopes and dry rainforest is associated; one is a large quarry mined for gravel and rock.
• The soils are mostly highly weathered sandstone-derived soils, with pans of clay (and potentially ferricrete) beneath the surface that act as aquitards and support the development of numerous small wetlands (i.e. areas mapped as 'contains wetlands'**).
• Sediments of the Maryborough Formation were deposited in a marine environment (i.e. when submerged by higher sea levels) and tend to contain high concentrations of salt with surface salts and visible salt scarring in some cleared areas.
• The Susan River anticline has marine deposits in the valleys and these deposits are eroding in some areas.
• There are many groundwater dependent ecosystems (GDEs) across the catchments, but groundwater infiltration and recharge is limited vertically where the hard geology is close to the surface (i.e. Maryborough Formation and/or aquitards).
• Due to the largely flat landscape and relatively low rainfall, most creeks are dry or flow slowly, and following rainfall events there are overland flows across much of the catchment.
• Tidal flows and natural connectivity that extends upstream from the large estuary also prevent the freshwater from draining away.
• Land use is mostly grazing on native pastures with large areas of residential and associated services, conservation and natural areas, forestry, irrigated cropping (sugar) and other farming (turf and pineapples) and other minor land uses.
• The area is important to First Nations peoples for its pathways, food resources, traditional use and management, and spiritual values.
• High values of the systems have been recognised through the presence of the Great Sandy Strait Ramsar site, Great Sandy Marine Park, Susan River declared Fish Habitat Area (FHA), Hervey Bay—Tin Can Bay Dugong Protection Area, Vernon Conservation Park, Directory of Important Wetlands Australia (DIWA, Great Sandy Strait), Great Sandy Biosphere, and nature refuges.
• Much of the catchment is wetland, with large areas of ‘contains wetlands’, palustrine and intertidal wetlands and relatively small lacustrine wetlands.
• Melaleuca drainage lines extend well up the catchment.
• Unique perched palustrine wetland ‘island’ surrounded by intertidal wetlands (mangroves and saltmarshes) on Kangaroo Island, which are receiving freshwater from groundwater discharge (aquifer).
• Large areas of salt couch not seen in other parts of the Great Sandy Strait.
• Many farm dams, particularly in Sunshine Acres residential development, and other barriers include bunded palustrine wetlands (Bunya Creek), natural rock bars (e.g. Kangaroo Island) and road crossings.
• Several bores, which extract water for mostly domestic purposes, and can influence groundwater systems.
• High value species and habitats include ground orchids, wallum heath with Eucalyptus tereticornis and melaleucas, Illidge’s ant-blue butterfly, flying fox roosts, bird feeding (e.g. brolgas, spoonbills, jabirus), and shorebird feeding and roosting areas, water mice, dolphins, dugongs and marine turtles.

Main image. Pineapple farming, Photo by Department of Environment and Science, Queensland Government.

*An anticline is a fold that is convex upward, and a syncline is a fold that is concave upward.

**Areas mapped as ’contains wetlands’ typically include many small wetlands, which are too small to map individually.

First Nations peoples

The Susan catchment is significant for the Butchulla people.

The catchment provided food and medicine and there is evidence of the Butchulla people’s occupation, including fish traps and areas where stone tools were sharpened. Fish including freshwater and saltwater fish were a staple food.

The catchment has important pathways for the Butchulla people.

Living off the land, the Butchulla people used fire as a tool to harvest certain foods, using traditional burning methods.

Modified features—infrastructure, dams, weirs and bores

Buildings and important infrastructure such as roads and tracks and railways, and creek crossings create barriers and impermeable surfaces that redirect water through single points or culverts. This can lead to channelling of water and increases the rate of flow and potential for erosion in some parts of the catchment. Modifications to channels, such as straightening and diversions, can also increase flow rates.

Roads and levees - conceptual diagram by Queensland Government

Low permeability surfaces - conceptual diagram by Queensland Government

Dams and weirs also modify natural water flow patterns, by holding water that would otherwise flow straight into the stream network. There are rural water storages (farm dams), weirs and bunds in parts of the catchment.

There are a number of bores*, which extract water for mostly domestic use, cropping and cattle and can influence groundwater systems.

Infrastructure, such as roads crossings, dams, weirs, pontoons and boat ramps, can affect fish passage through the catchment.** ^

Culvert road crossing on Black Swamp Creek, Photo by Department of Environment and Science, Queensland Government.

Main image. Piped road crossing on Bunya Creek, Photo by Mary Chang.

*Includes registered water bores used for water supply only, provided by derived data set from DNRM&E that excludes monitoring bores.

See links at the end of this map journal for further information on the following literature.

**Enhanced Management of Ramsar Site Wetlands within the Great Sandy Strait Catchments (Department of National Parks, Sports and Racing 2016).

^Great Sandy Strait Biopassage Remediation Project – Final Report (Berghuis 2012).

Modified features—sediment

Increases in the volume and speed of runoff, and disturbed vegetation through activities such as grazing and construction, can increase erosion in the landscape and the stream channels. This can result in sediment being carried downstream and reduced water quality. The construction stage of a development typically generates more sediment in runoff than more mature stages of a development.

Suspended sediment can reduce water quality in the Great Sandy Strait as it:

• transports nitrogen and phosphorus (and other potential contaminants such as metals),
• travels in flood plumes,
• reduces light when in suspension, and
• can smother benthic communities such as seagrasses, corals and other invertebrates (e.g. filter-feeding bivalves).

Furthermore, the impacts of suspended sediment contributes to the cumulative impacts of other stressors (e.g. freshwater flood plumes, elevated nutrients, impacts from storms) to increase the overall impact on organisms of the Strait.

Main image. Eroding bank, Bunya Creek, Photo by Mary Chang.

Water quality

Water quality is influenced by diffuse runoff and point source inputs. Runoff is from a variety of land uses, including rural, residential and forestry areas.

Diffuse runoff includes on-site sewage facilities (e.g. septic tanks) and stormwater discharges, particularly from low permeability surfaces common in urban areas. The concentration of potential contaminants in the stormwater discharge depends on the land use of the area.

Septic tank diagram provided by SEQ catchments, Ipswich City Council and West Moreton Landcare, using IAN Library products.

Point source inputs include the Nikenbah sewage treatment plant (STP), which provides irrigation water for cane lands. Some of the rural areas use septic tanks.

Cattle, pigs and other animals can also directly influence water quality by disturbing the substrate and/or trampling vegetation.

Catchment conceptual model, Provided by Queensland Government.***

See links at the end of this map journal for further information on the following references.

*Reef 2050 Water Quality Improvement Plan (Queensland Government 2018)

Related literature: Reef 2050 Water Quality Improvement Plan - Report Cards (Queensland Government 2017)

Water flow

Water flows across the landscape into the waterways of the catchments (click for animation)*.

The remaining water either sinks into the ground where it supports a variety of groundwater dependent ecosystems (GDEs), including terrestrial GDEs, or is used for other purposes. Groundwater naturally expresses as springs** and/or pools below the steep basalt caps.

The smaller channels and gullies eventually flatten out to form larger waterways that flow through lower lying land. They pass through unconsolidated areas which store and release water, prolonging the time streams flow.

Main image. Powerline easement, Stockyard subcatchment, Photo by Department of Environment and Science, Queensland Government.

*Please note this application takes time to load.

**Springs are defined as hydrogeological features by which groundwater discharges naturally to the land surface or cave.

Vegetation

Water that falls as rain, or moves over the land as runoff, is slowed by vegetation, which then allows it to filter down into the soil and sub-soil. Slowing the flow of surface water helps to retain it longer on the land which in turn allows it to filter down through the soil and bedrock to recharge groundwater aquifers.

Water moving slowly across the surface of the land also reduces the potential for erosion to occur and reduces the associated issues with water quality and sedimentation further downstream. Reducing the speed of runoff also plays a role in protecting banks and parts of the landscape prone to gully and rill erosion.

Vegetation conceptual model, Photo by Queensland Government.

Historically, the area was dominated by eucalypt woodlands and forests, melaleuca woodlands and coastal communities including heath. Rainforests and scrubs grew on the northern ridge and coastal areas supported mangroves and saltmarshes.

These different vegetation types combine to make up the preclearing vegetation of the Susan catchment.*

The wetlands and creeks of the catchment provide habitat for many important aquatic species, including plants, fish and birds. These areas are also used for fishing, crabbing and boating.

Wetland (aquatic ecosystem) types, WetlandInfo, Department of Environment and Science, Queensland.

*Broad Vegetation Groups derived from Regional Ecosystems (REs), which are vegetation communities in a bioregion that are consistently associated with a particular combination of geology, landform and soil.

Main image. Lagoon on Black Swamp Creek, Photo by Department of Environment and Science, Queensland Government.

Vegetation clearing

Large parts of the mainland catchments have been cleared or partially cleared* for a range of land uses, particularly grazing but also residential development and other farming. Many areas have regrown** since initial clearing.

Explore the Swipe Map using either of the options below.***

• Interactive Swipe App where you can zoom into cleared areas and use the swipe bar (ESRI version)
• Interactive Swipe App where you can use the swipe bar. Use the white slide bar at the bottom of the map for a comparison (HTML version)

Vegetation clearing and associated activities change the shape of the landscape and can modify surface and groundwater flow patterns.

Main image. The Springs residential development, Photo by  Department of Environment and Science, Queensland Government.

*The 2011 remnant vegetation mapping was undertaken at a map scale of 1:100,000 and 1:50,000 in part (including the Wet Tropics and south-east Queensland) and based on the Landsat imagery for 2011. It does not show all clearing, particularly relatively thin linear infrastructure.

**Smaller areas of regrowth are not shown in this mapping. This dataset was prepared to support certain category C additions to the Regulated Vegetation Management Map under the Vegetation Management (Reinstatement) and Other Legislation Amendment Bill 2016. This dataset is described as: The 2013 areas of non-remnant native woody vegetation that have not been cleared between 1988 and 2014 that are homogenous for at least 0.5 hectare and occur in clumps of at least 2 hectares in coastal regions and 5 hectares elsewhere.

***Depending on your internet browser, you may experience issues with one or the other. Please note this application takes time to load.

The subcatchments

A 'catchment' is an area with a natural boundary (for example ridges, hills or mountains) where all surface water drains to a common channel to form rivers or creeks.*

The Susan River is a single catchment, often included as a subcatchment of the Mary River. The Susan River does however consists of several distinct areas which have similar characteristics:

• Upper Susan subcatchment (Susan River and unnamed tributaries)
• Stockyard subcatchment (Stockyard and Black Swamp creeks)
• Bunya subcatchment (Bunya Creek and unnamed tributaries)
• Lower Susan subcatchment (the Susan river, Kangaroo Island, Johnnys Creeks and unnamed tributaries)

*Definition sourced from the City of Gold Coast website - see links at the end of this map journal.

Main image. Cane farming, Bunya subcatchment, Photo by Department of Environment and Science, Queensland Government.

Upper Susan subcatchment

• The geology of the Upper Susan subcatchment is dominated by the deeply weathered surface of ferricrete, arenite-mudrock (Burrum Coal Measures) in the upper parts, and arenite-mudrock (Maryborough Formation), and alluvium in the lower parts.
• Gently undulating to flat subcatchment up to 40 metres above sea level.
• Average annual rainfall of approximately 1,001 to 1,201 millimetres per year.
• The Maryborough Formation is largely impervious and does not provide for ground water infiltration, instead, water remains on the surface or seeps sideways into drainage lines.
• The more porous Burrum Coal Measures and limited alluvium provide for water infiltration where not developed.
• On the slightly elevated surface of the Susan upper catchment, soils are mostly highly weathered and sandstone-derived, having pans of clay (and potentially ferricrete) intermittently beneath the surface that act as aquitards and support the development of numerous small wetlands (i.e. areas mapped as 'contains wetlands'*).
• Much of the upper catchment is conservation and natural environments, and other land uses are mostly grazing on native pastures with large areas used for recreation and culture, conservation and natural environments and irrigated cropping (sugar), and small areas of forestry, mining (quarries) and residential.
• The area is important to First Nations peoples.
• Most of the subcatchment is wetland, with large areas of ‘contains wetlands’ and palustrine wetlands, including reed beds.
• Some pools form in the alluvium where tributaries merge.
• Freshwater wetlands connect downstream to intertidal saltmarsh and mangrove.
• Hydrologically well-connected, with one dam upstream from the Susan River’s tidal limit at the Hervey Bay Road and several farm dams on side tributaries in the lower parts.
• Freshwater rises and falls with tidal flows along the main channel of the Susan River east of the Hervey Bay Road, exacerbating flooding of this lower catchment after heavy rainfall.

*Areas mapped as ’contains wetlands’ typically include many small wetlands, which are too small to map individually.

Stockyard subcatchment

• The geology of the Stockyard subcatchment is dominated by ferricrete and arenite-mudrock (Maryborough Formation) in the upper parts, and alluvium in the lower parts.
• The top of the catchment has basalt caps.
• Gently undulating to flat subcatchment up to 50 metres above sea level, with parts of the lower catchment below HAT (Highest Astronomical Tide) and tidal.
• Average annual rainfall of approximately 1,001 to 1,201 millimetres per year.
• The Maryborough Formation is largely impervious and does not provide for ground water infiltration.
• The alluvium provides for water infiltration where not developed, and the ferricrete provides for some local water infiltration.
• Mixed land use including grazing on native pastures, residential and associated services, conservation and natural areas (Vernon Conservation Park), irrigated cropping (sugar) and other farming (turf, pineapples and other fruits and berries), manufacturing and industrial (sawmill), mining (quarries) and waste treatment and disposal (Nikenbah sewage treatment plant).
• Much of the subcatchment is wetland, with large areas of ‘contains wetlands’*, palustrine wetlands and several lacustrine wetlands, which are well-connected to intertidal saltmarsh and mangrove forests.
• Stockyard Creek is a near-permanent system and includes several large permanent lagoons, such as downstream from the conservation park where the creek widens out into melaleuca wetlands.
• Major barriers include two dams within the main channel and a straightened spillway, together with barriers associated with causeways (fire-fighting access) and roads (e.g. Hervey Bay Maryborough Road bisects the main channel and associated melaleuca wetlands).
• Many small farm dams and septic tanks in Sunshine Acres residential development.
• Several bores extract water for mostly domestic purposes.
• Hervey Bay’s Nikenbah STP recycles urban water in an inter-basin transfer from the adjacent catchment onto cane lands upstream from freshwater wetlands.
• Evidence of scalding and salinity issues along parts of lower Black Swamp Creek and Stockyard Creek.
• High tides hold up waters in Black Swamp Creek where fresh water is moving up and down, and this tidal influence in the lower catchment can exacerbate local flooding after heavy rainfall.
• High value species and diverse habitats include a high diversity of ground orchids (Black Swamp Reserve), wallum heath with Eucalyptus tereticornis and melaleucas along the drainage lines (Vernon Conservation Park), bird feeding areas (e.g. brolgas, spoonbills, jabirus), shorebird feeding and roosting areas and flying fox roosts.

Main image. Maryborough Hervey Bay Road crossing of Black Swamp Creek, Photo by Department of Environment and Science, Queensland Government.

*Areas mapped as ’contains wetlands’ typically include many small wetlands, which are too small to map individually.

Bunya subcatchment

Farm dam, Photo by Department of Environment and Science, Queensland Government.

• The Bunya subcatchment has mixed geology of arenite-mudrock (mostly Maryborough Formation with Elliott Formation and Burrum Coal Measures), basalt caps, rudite and ferricrete in the upper parts, and in the lower parts alluvium and miscellaneous unconsolidated sediments (marine mud).
• Mostly flat subcatchment below 10 metres above sea level (ASL), with some steep headwaters up to 50 metres ASL and tidal influence extends high in the catchment.
• Average annual rainfall of approximately 1,001 to 1,201 millimetres per year.
• The Maryborough Formation and rudite are largely impervious and do not provide for groundwater infiltration.
• The more porous Elliott Formation, Burrum Coal Measures, alluvium and basalt provides for water infiltration, where not developed, and ferricrete provides for some local water infiltration.
• Groundwater expresses as springs / pools below the steep basalt caps.
• Mixed land use including grazing on native pastures, residential and associated services, conservation and natural areas, irrigated cropping (sugar) and other farming (turf and pineapples), forestry, waste treatment and disposal (Nikenbah sewage treatment plant, STP), mining (quarries).
• Nikenbah STP water used to irrigate cane lands.
• Relatively little native vegetation apart from some riparian vegetation along wider alluvial areas. Melaleucas indicate key hydrological areas.
• High values of the systems have been recognised through the presence of the Great Sandy Strait Ramsar site, Great Sandy Marine Park, Susan River declared FHA, Hervey Bay—Tin Can Bay Dugong Protection Area, the DIWA (Great Sandy Strait) and Great Sandy Biosphere.
• The subcatchment includes large intertidal and palustrine wetlands, together with areas of ‘contains wetlands’* and lacustrine wetlands.
• Several farm dams and bunded estuarine areas that are now palustrine wetlands, with bunds becoming drowned-out following heavy rainfall and/or large tide.
• Several bores extract water for mostly domestic purposes.
• Evidence of salt scalds in cleared areas.
• High value species and habitats include dolphins, dugongs and marine turtles.
• Bunded palustrine areas are important for migratory shorebirds and waterfowl.

Main image. Main Street, Ghost Hill, upper Bunya Creek subcatchment, Photo by Department of Environment and Science, Queensland Government.

*Areas mapped as ’contains wetlands’ typically include many small wetlands, which are too small to map individually.

Lower Susan subcatchment

• This Lower Susan subcatchment has mixed geology of ferricrete, arenite-mudrock (Maryborough Formation and Burrum Coal Measures), rudite, with a broad area of alluvium and miscellaneous unconsolidated sediments (including marine muds surrounding coastal sand ridges in the estuary).
• Mostly flat subcatchment below 10 metres above sea level (ASL), with isolated hills up to 20 metres ASL.
• Much of the lower catchment is below Highest Astronomical Tide (HAT) and under tidal influence, with a network of mangrove and saltmarsh islands.
• Downstream the Susan River discharges into the Mary River at its confluence near River Heads, and also via Kangaroo Passage, a back channel to the Mary River behind Kangaroo Island.
• Natural rock bars around Kangaroo Island influence water flow.
• Average annual rainfall of approximately 1,001 to 1,201 millimetres per year.
• The Maryborough Formation and rudite are largely impervious and do not provide for ground water infiltration.
• The more porous Burrum Coal Measures and alluvium provide for water infiltration, where not developed, and the ferricrete provides for some local water infiltration.
• Islands of sand within the estuary act as sponges above the less permeable marine muds, allowing surface water to enter the groundwater systems sitting above the less porous marine mud.
• Land use is mostly grazing on native pastures, saltmarsh and wetland areas including ponded pastures, irrigated cropping (sugar) including cane affected by marine influence, residential and associated services, with conservation and natural areas.
• Estuarine channels are important for boat anchorages and recreational fishing.
• High values of the systems have been recognised through the presence of the Great Sandy Strait Ramsar site, Great Sandy Marine Park, Susan River declared FHA, Hervey Bay—Tin Can Bay Dugong Protection Area and DIWA (Great Sandy Strait).
• Most of the catchment is wetland, with large areas of ‘contains wetlands’*, palustrine wetlands and a relatively large lacustrine wetland.
• Extensive intertidal mangroves and saltmarsh dominate the lower catchment.
• Kangaroo Island has unique perched palustrine wetlands surrounded by intertidal wetlands (mangroves and saltmarshes).
• There are unique freshwater/brackish vegetation communities and large representatives of certain intertidal and subtidal wetland types e.g. intertidal (saline) grasslands, and bare saltpans that are important feeding and roosting areas for migratory shorebirds.
• Several farm dams, including bunded estuarine wetlands that are now palustrine wetlands.
• High value species and habitats include Illidge’s ant-blue butterfly, flying fox roosts, shorebird feeding areas and roosts, dolphins, dugongs and marine turtles.
• Tidal areas are important for recreational and commercial fishing for banana prawns, snapper, mullet, mud crab, whiting, bream (yellowfin), tailor, gar, flathead, winter whiting, grunter, estuary cod, luderick and mangrove jack.

*Areas mapped as ’contains wetlands’ typically include many small wetlands, which are too small to map individually.

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Last updated: 23 July 2020