Transcript

Coombabah Catchment Story

This Map Journal is part of a series prepared for the catchments of South East Queensland. .

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Understanding how water flows in the catchment

To effectively manage a catchment it is important to have a collective understanding of how the catchment works. This map journal gathers information from experts and other data sources to provide that understanding.

The Coombabah Sub-Catchment Story describes the location, extent and values of the sub-catchment. It demonstrates the key features which influence water flow, including topography, geology, natural features, human modifications and land uses as well as outlining the potential impacts of climate change. The story also includes key messages from a suite of sediment, benthic fauna, vegetation, water quality, tidal processes and bathymetry studies undertaken between 2019-2023.

This story outlines information drawn from 1) the ‘walking the landscape’ process for the Northern Gold Coast Catchment, 2) available data and information on the sub-catchment and 3) specific studies of sediment, vegetation, benthic fauna, water quality, tidal processes and bathymetry, undertaken for the Coombabah wetland system by the Department of Environment, Science and Innovation (DESI), the City of Gold Coast (CoGC) and the Department of Transport and Main Roads (DTMR).

The studies were undertaken partly in response to community concerns that the Coombabah wetland system was undergoing siltation and changes in channel width and depth. Additional studies of vegetation, sediments, benthic invertebrates and water quality were undertaken by DTMR as part of the Coomera Connector Road upgrade. These studies, coupled with an historical overview, provide an understanding of the current state of the wetland system as well as past changes. They also provide insight into how the system may change in response to increasing urbanisation and changing climate.

The Coombabah Sub-Catchment Story was prepared by the Queensland Wetlands Program in the Queensland Department of Environment, Science and Innovation in collaboration with local partners.

Table of contents

• Overview of the Coombabah Sub-Catchment
• Values
• Historical Perspectives
• Land Use & Modified Features
• Geology
• Hydrology & Water Flow
• Hydrological Studies of Coombabah Wetland System
• Sediment & Marine Fauna Studies of Coombabah Wetland System
• Vegetation
• Vegetation Studies
• Waterbirds and shorebirds
• Watching Wildlife at Coombabah
• Future Risks of Coombabah Sub-Catchment
• Ongoing Management & Monitoring of Coombabah Sub-Catchment

Photo: Coombabah Reserve & Mangrove Walk - provided by Gold Coast City Council.

Coombabah Sub-Catchment Overview

Nestled within the Northern Gold Coast Catchment region, the Coombabah sub-Catchment sits within the Coomera River Catchment. Originating within the Nerang National Park, Coombabah Creek flows downstream and converges with the Coombabah Lake before flowing into the lower reaches of the Coombabah Creek where it connects with the estuarine area of the Coomera River. This sub-catchment holds significant importance to the Gold Coast Region. Positioned within the Southeast Queensland Bioregion, its distinct features, notably the lake, creek and associated coastal wetlands provide a diverse range of wetland values.

Values

The Coombabah sub-catchment, from its headwaters to its estuarine reaches, has many cultural heritage and ecological values. Major parts of the Coombabah wetland system are part of the internationally recognised Moreton Bay Ramsar Site. Much of the Coombabah wetland system is also incorporated in the Moreton Bay Marine Park and the Coombabah declared Fish Habitat area. Please click the following links for more information about Ramsar wetlands, state marine parks and declared fish habitat areas.

The sub-catchment is an invaluable educational resource, offering a living laboratory for understanding wetland ecosystems. Its accessibility and diverse ecological features make it an ideal site for fostering environmental awareness and understanding among residents and visitors alike. The CoGC and Queensland Government support use of the sub-catchment for recreation and ecological education, and for local schools and universities to use the facilities for learning. Click Here for more information about recreational and educational services for Coombabah Lakelands Conservation Area.

Photo: Coombabah Lake - Provided by Ralph Dowling

Values

Much of the headwaters of the Coombabah Creek Sub-Catchment are contained within the Nerang National Park and adjacent Nerang State Forest (Park). This Park plays a foundational role in the hydrological tapestry of the sub-catchment; its 1600 hectares serve as the primary collector of rainwater and numerous small tributaries start in this area and then converge and shape the course of Coombabah Creek.

The Park has a diverse range of vegetation such as eucalypt and dry rainforests, creating a substantial wildlife refuge for many threatened species, including Macadamia integrifolia M. tetraphylla, spiny gardenia, powerful owl, greater glider, koala, glossy black-cockatoo and the Richmond birdwing butterfly. Remnant gallery rainforest thrives in the gullies.

The Park is a popular recreational destination, drawing individuals keen on immersing themselves in nature through activities such as hiking, horse riding, and exploring the extensive mountain bike trails.

Management plans are in place to preserve and protect the Parks natural and cultural values while providing nature-based recreational opportunities. Click Here for more information about the Nerang National Park Management Plan.

Nerang National Park - provided by Queensland Government

Main image by Gary Cranitch © Queensland Museum

Values

As the Coombabah Creek meanders downstream towards the lake, it supports ecological values within the riparian zone. This critical nature corridor is a hub of biodiversity, providing a refuge for wildlife and passage for the movement of animals, thereby helping support viable populations throughout the sub-catchment.

Riparian vegetation plays a critical role in supporting the health of rivers, creeks, and streams. The influence of vegetation extends to the micro-climate of the water systems, providing essential shading and debris that contribute to habitat complexity and influence water flow and channel formation. The effects of vegetation both living and dead, slow water flows and encourage the deposition of sediment particles, influencing water quality and clarity. Additionally, riparian vegetation enhances landscape resilience by stabilising banks and preventing erosion.

Vegetated buffer conceptual model - Provided by Queensland Government

Values

The Coombabah Lake and its surrounding wetlands are part of a large wetland complex which includes freshwater wetlands and tidal wetlands. The system connects to the Gold Coast Seaway, Moreton Bay, and Jumpinpin via lower Coombabah Creek and the Coomera River. Coombabah Creek meanders for approximately 15km from its headwaters in the Nerang National Park to feed into the lake. The lake is also fed by tributaries from Helensvale, Arundel, Gaven, Pacific Pines, Parkwood and upper Coombabah Creek. Below the lake, Saltwater Creek joins lower Coombabah Creek just before it reaches the Coomera River.

Acknowledged as an important fish habitat by the Queensland Government since the 1960s, Coombabah Lake was initially gazetted as a fish sanctuary under the Fisheries Act (1957-62). Subsequent formalisation included the estuarine portions of Coombabah Creek above and below the lake being gazetted as a Wetland Reserve in 1983. Much of the area was listed in 1993 as part of the internationally important Moreton Bay Ramsar Site. More recently, the lake and estuary were designated a declared Fish Habitat Area under the Fisheries Act 1994 and a Marine National Park Zone under the Marine Parks (Moreton Bay) Zoning Plan 2008 and the Marine Parks (Moreton Bay) Zoning Plan 2019.

Indigenous Archaeological Sites - provided by Ralph Dowling

Main image by Gary Cranitch © Queensland Museum

Historical Perspectives

Coombabah Lake is part of an old wetland system that has been a stable geomorphic landscape feature for tens of thousands of years, with the first signs of Coombabah Lake emerging during the last Glacial Maximum i.e. 28,000-18,000 years before present (yr. BP). Prior to ~8000 yr. BP, Coombabah Lake would have been a freshwater system. This system is believed to have gradually changed to a saltwater coastal lagoon system as sea levels rose toward the post-glacial Holocene sea level high-stand (~7,500 yr. BP) when seawater flooded the broader Coombabah-Helensvale Valley. As the sea level receded again (~2000-200 yr. BP), the lake system took on a brackish nature, receiving both tidal and freshwater inputs.

Settlement has contributed to rapid change throughout the sub-catchment. Since the ~1850s, the broader sub-catchment and Coombabah wetland system has undergone significant change because of land clearing and associated activities such as grazing. In the 1860s a network of channels was constructed to drain freshwater wetlands to improve pasture. This also facilitated saltwater intrusion and mangrove expansion into previously freshwater or brackish areas adjacent to the lake.

The Coombabah Lake was originally known as Oyster Lake until the late 1920s, due to the abundance of oyster reefs and mangrove oysters within the system. This resulted in an oyster harvesting enterprise from about 1880, however, it was short-lived due to an introduced marine mud worm (Polydora sp.) from New Zealand that eradicated the entire population of oysters. The loss of the oyster beds combined with development in the catchments resulted in significant sediment movement within the bottom of the lake.

The photo is from the City of Gold Coast Libraries Local Studies Collection, Title: Aerial view over Coombabah Lake showing adjoining wetlands and swamp regions, Queensland. Identifier: LS-LSP-CD095-IMG0035. Creator: Unidentified. Date 1950-59

Historical Perspectives

The breakthrough of tidal water at Jumpinpin in about 1894 (the exact date is unknown), and the opening of the Gold Coast Seaway has resulted in stronger incoming and outgoing tides, increasing both the deposition of silt and the tidal range – allowing for saltwater intrusion into the lake and wetland areas.

By 1978 the start of housing developments began around Jabiru Island and Helensvale, and by 2021 much of the sub-catchment was high-density residential areas with riverside/estuary canal estates, marinas, and golf courses. Prior to European settlement, the area around Coombabah Lake was inhabited by the Kombumerri First Nations people who continue to live locally.

Despite the extensive development, this wetland complex is the last remaining representative of its type and size within the Gold Coast region. To see how much the landscape has changed around the Coombabah Lake from 1944 to the present Click Here and use the sliders.

Land Use & Modified Features

The landscape of the Coombabah Creek Sub-Catchment has undergone significant transformations due to the expansion of urbanisation, leading to modification of its natural features.

A quarry adjacent to Nerang National Park and Coombabah Creek includes detention ponds designed to treat runoff, before discharge into the creek system.

The sub-catchment is intersected by an extensive road network, notably The Pacific Motorway, which cuts through the middle of the sub-catchment. The Gold Coast Highway is a partial barrier, between the upper freshwater Coombabah Creek and the lower brackish/marine Coombabah Lake. On the western side of the wetland system, an elevated commuter train line serves not only as a transportation route but also acts as a barrier due to its positioning above typical flood levels.

Man-made alterations to the hydrological nature of the sub-catchment include the construction of canal systems and several tidal gates to accommodate waterfront estates and private jetties. Weirs and tidal gates have been strategically installed to regulate water levels within the sub-catchment. The Coombabah Wastewater Treatment Plant within the CoGC's Coombabah Lakes Conservation Area, plays a crucial role in treating wastewater before it is transferred by pipeline and released at the Gold Coast Seaway. The wastewater treatment plant is also a haven for wildlife, attracting migratory, resident shorebirds and other wildlife. Numerous water storage areas within the sub-catchment contribute to the modification of water flows and groundwater filtration.

Stage 1 of the Coomera Connector is a State-controlled north-south transport corridor that runs between Foxwell Drive at Coomera and Nerang Broadbeach Road. Click Here for more information about the Coomera Connector.

Coomera Connector Map - provided by City of Gold Coast

Geology

There are various rock types that make up the geology of the sub-catchment. The upper reaches of the sub-catchment consist of fractured metamorphic rock, which contain fractured rock aquifers that allow for localised infiltration of rainwater in the headwaters of the system. During periods of high rainfall, the upper, steeper, reaches of the sub-catchment experience increased runoff into the creek system, influencing hydrological dynamics further downstream.

In the lower areas of the sub-catchment encompassing the lake, estuary and other wetland habitats, there are large areas of unconsolidated sediments, including alluvial deposits and marine mud. These geological features absorb and retain water which can contribute to groundwater recharge through infiltration processes.

Substantial portions of the lower sub-catchment landscape have undergone in-fill for urban development. These areas have generally non-permeable surfaces which alter the natural processes of water recharge and infiltration into the groundwater systems. Understanding the distinct geologies within the sub-catchment is crucial for understanding the intricate ecological balance and water dynamics that shape this diverse and vital ecosystem.

Hydrology & Water Flow

Coombabah Creek, the main watercourse of the sub-catchment, is a near permanent freshwater system. The headwaters of the Creek and lower wetland system originate in the Nerang National Park. Rainfall and associated overland flow feed the network of tributaries draining into Coombabah Creek and recharge groundwater aquifers. The smaller tributaries extend from suburbs such as Helensvale, Arundel, Gaven, Pacific Pines, Nerang, and Parkwood. The freshwater that enters the system ultimately finds its way into the Coral Sea.

Steeper slopes in the upper reaches contribute to fast runoff during high rainfall events, occasionally flooding the system. Additionally, runoff from hard surfaces, drainage, and stormwater increases the flow downstream. Before the upper waters of Coombabah Creek reach the lake, the Gold Coast Highway acts similar to a bund, with a channel break to allow the water to continue into Coombabah Lake. This restriction of water flow along with infilling of Coombabah Creek has created a distinction between freshwater and saltwater systems and associated flora and fauna on each side of the highway.

Historically a freshwater system, the Lake's character has transformed into an estuarine ecosystem over time due to the opening of the Jumpinpin and the Gold Coast Seaway. Tidal inputs via Lower Coombabah Creek, Saltwater Creek, and the Coomera River have contributed to this transformation.

Water quality within the sub-catchment is influenced by various inputs, including rare recycled water spill events during periods of very high rain and stormwater input. Despite the porous alluvium geologies underlying the lake, groundwater infiltration is also restricted by extensive urbanisation and other impermeable surfaces throughout the lower sub-catchment.

An additional factor influencing the hydrology of the system is the occurrence of natural weather and climatic events, including floods and droughts. The relatively small size of the Sub-Catchment increases its vulnerability to the impacts of drought, excessive siltation, and reduced freshwater input to flush the system. Compared to natural floodplains, the developed areas of the Coombabah sub-catchment are less effective at water storage and flood mitigation.

Main image by Gary Cranitch © Queensland Museum

Hydrological Studies of Coombabah Wetland System

In late 2020, several tide gauges were deployed in the lake and estuary to conduct a comprehensive tidal survey of the system. Data were collected over 18 months, to identify changes in hydrological depths and dynamics. The tidal data compared to historic records for the Coombabah wetland system suggest that the tidal levels have changed slightly over the period 1985-2020. The most notable change is the increased tidal prism which is leading to lower low waters and higher high waters. This may be due to several factors including the opening of the Gold Coast Seaway and the lag time needed to establish a new equilibrium. Additionally, the Highest Astronomical Tide (HAT) has increased at the southern end of the lake and even more so at the mouth of Coombabah Creek. However, it should be noted that these data are limited, and further investigations are required to confirm the trend over a longer time period. The altered hydrology resulting from the openings to the ocean, combined with the impacts from European settlement such as wetland drainage and urban expansion in the sub-catchment, have resulted in vegetation change, most notably the transition from saltmarsh/marine couch to mangrove-dominated communities.

Bathymetric surveys (underwater topography) of Coombabah Lake and Creek were undertaken over 2020/21 and again in 2023 to investigate sedimentation processes and bed form evolution. A combination of methods was used to survey the lake including the use of a traditional manned survey vessel. To survey deeper parts, a remote-controlled vessel fitted with a Ceescope single beam echosounder was used. Shallow sections and exposed banks were surveyed using a drone.

The results from 2020/21 and 2023 survey/s were compared with bathymetric data from 2005 to detect changes over time (noting all bathymetric data was referenced relative to AHD). The bathymetric images show that the average depth of the lake has decreased since 2005 with increasing siltation and mangrove growth and expansion of the mangrove islands in the north-east of the site. Of note is the north-western arm which has undergone significant shallowing and mangrove encroachment since 2005 and southwestern parts of the lake which have become shallower since 2005. Other parts of system have experienced channel widening and deepening. The southern creek entrance and much of the northern creek entrance have deepened since 2005, with significant differences observed between 2021 and 2023. The increased channel depths since 2021 is most likely due to high rainfall events and strong freshwater inputs causing erosion and redistribution of sediments.

The overall morphology of this wetland system appears to be heavily shaped by hydrological events. Flood and drought can reshape the habitat available for species. Flood can trigger erosion, mobilisation, transport and redistribution of sediments resulting in accretion of some parts and deepening of others. Droughts, however, tend to slow systems down causing deposition and accretion from reduced freshwater inputs. The tidal studies and depth changes observed at Coombabah Lake and creek as well as altered channel morphology give clues as to what might be expected from future drought and flood events and from rising sea levels.

To see the changes in Bathymetry over time, Click Here and use the sliders.

Photo: Coombabah Lake tide gauge sites - Provided by DES

Main Photo: 2012 Coombabah Lakelands - Provided by Ralph Dowling

Sediment and Marine Fauna Studies of Coombabah Wetland System

Studies of the sediment source and biological health of the Coombabah wetland system undertaken in 2021, have confirmed that the overall system is in a relatively healthy state with water quality predominantly meeting established guidelines. The studies revealed a diverse array of species.

The abundance and distribution of macrobenthic invertebrates remained consistent with previous studies and is indicative of a healthy estuarine ecosystem. Although there were some observed species differences, these variations suggest successional changes, a natural phenomenon expected over time and influenced by factors such as the extended period between sampling sessions and/or limited sampling to capture seasonal variations. Across the wetland system, good species richness and abundance were observed, with spatial variations likely attributed to differences in site positioning, sampling frequency, and seasonal variations. The greatest species richness and abundance were observed in proximity to mangroves, attributed to the habitat, refugia and feeding grounds this ecosystem provides. The upstream areas featured more freshwater-tolerant species, while typical marine species were found within the estuarine region.

The sediment composition and pattern are consistent with previous studies, with finer sediments in the upper creek and lake and coarser sediments in the lower creek (estuary). The water quality results are consistent with the resuspension of sediments, particularly in the upper lake, which is typical of a shallow estuarine environment.

The estuarine waters connecting Coombabah Lake to the mouth of the Coomera River serve as a vital link between fresh and marine environments. Numerous species traverse this area for activities like spawning, nursing young, seeking refuge, or feeding. This includes many species such as Australian bass, bream, estuary cod, flathead, garfish, luderick, mangrove jack, sea mullet, tailor, whiting, banana prawns, king prawns, bay prawns, along with occasional sightings of dolphins and turtles.

Click Here to view the CoGC's final report on Water Quality and Biological Health of Coombabah Lake.

Photo: Research and sampling on Coombabah Lake - provided by CoGC

Vegetation

The diverse vegetation types within the Coombabah Creek Sub-Catchment significantly influence and are influenced by water flow and quality. Prior to European development, the sub-catchment contained rainforests, vine forests and scrubs in the upper reaches of the Nerang National Park. The mid to lower reaches along the creek and the wetland outskirts, supported varying degrees of open eucalypt forests that were dominated by species such as blue gum (Eucalyptus tereticornis). Within the lower floodplain, vast areas of swamp paperbark (Melaleuca quinquenervia) dominated the landscape, accompanied by pockets of wet eucalypt species like flooded gum, red mahogany, brush box, and stringybark. Surrounding the lake and wetland areas were pockets of mangroves and saltmarshes, as well as other coastal communities including heath.

Even though there has been considerable vegetation clearance in the sub-catchment since 1944, vegetation diversity offers significant ecological value, supporting biodiversity and contributing to overall system health. Beyond providing habitat for local wildlife, healthy vegetation plays a crucial role in purifying water and slowing runoff, which enhances water retention via groundwater and aquifer infiltration. The root systems, stabilise banks against erosion and potential damage during high-flow events. The Coombabah Sub-Catchment plays an important role in conserving threatened species such as saltmarsh (vulnerable) and lowland tropical rainforest (critically endangered), both protected under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC).

To see the changes in vegetation over time, Click Here and use the sliders.

Main Photo: Coombabah Lakelands Saltmarsh and Ponding - Provided by Ralph Dowling

Vegetation Studies

The vegetation studies of Coombabah wetland in 2021 identified changes in vegetation patterns and their relationship to changes in tidal levels. Findings reveal variations in vegetation communities are primarily influenced by the flat topography of the lake and wetland area. While pockets of freshwater ponding support freshwater species, increasing saltwater intrusion and higher tidal levels have led to the dominance of estuarine species which are more tolerant of the saline conditions.

Before 1944, the entire lake system was brackish, with a surrounding mosaic of vegetation comprised of Melaleuca quinquenervia (swamp paperbark), saltmarsh, and small communities of mangroves near the mouth of the lake and lower estuary. Since then, most of the original vegetation communities have been cleared for residential development and/or have been affected by land use change. Openings to the open ocean via the Gold Coast Seaway and Jumpinpin may have increased saltwater intrusion causing significant dieback of melaleuca and casuarina and loss of marine couch (Sporobolus virginicus) and saltmarsh which are gradually being replaced by Avicennia marina (grey mangroves). Evidence from the studies suggest that encroachment of mangroves into marine couch and saltmarsh communities will continue as long as current eco-geomorphic/hydrologic (interactions between ecology, geomorphology and hydrology) conditions prevail.

Upstream areas in the southern part of the system, have been predominantly affected by freshwater runoff from surrounding urban areas creating freshwater ponds and swamps in areas previously under tidal influence. Downstream and around the lake, saltwater intrusion and geomorphic processes have led to the formation of saline ponds over areas that were once claypan and salt flat. These ponds are being progressively colonised by mangroves.

While the studies suggest the extent of the different vegetation communities have been relatively stable since 2012, the studies also suggest a “reshuffling” of communities is occurring. As the site has become wetter, Casuarina glauca is moving to slightly higher and drier areas as is Melaleuca quinquenervia. Further changes to vegetation extent and pattern are likely to continue into the future due to landscape alterations and rising sea level, including an increased extent of intertidal vegetation dominated by mangroves. Landscape alterations have fundamentally shifted the system's hydrological processes and coincidentally changed the dynamics of the ecosystems within the sub-catchment.

Click Here to view the DES final report on Coombabah Lake's assessment of Vegetation Change 1944 - 2021.

Photo: Coombabah Saltmarsh - Provided by Ralph Dowling

Main Photo: Coombabah Lake - Provided by Gold Coast City Council

Waterbirds & Shorebirds

Coombabah Creek and Coombabah Lake are important habitat for a range of aquatic birdlife which includes migratory and resident shorebirds, raptors, waterbirds, terns and gulls. Migratory shorebirds at the site include eastern curlew, whimbrel, bar-tailed godwit, black-tailed godwit, terek sandpiper, sharp-tailed sandpiper, common greenshank and pacific golden plover, some of which are listed as vulnerable or threatened.

The resident shorebirds include pied oystercatchers and large numbers of black-winged stilts. The red-necked avocet is an important regular visitor. White-bellied sea-eagles, brahminy kites and whistling kites are common.

Terns include the greater crested tern, caspian tern, and regular large populations of Australian terns. Whiskered terns make occasional visits to the lake. The water birds include silver gull, Australian pelican, black swan, great egret, intermediate egret, little egret, pied cormorant, little pied cormorant, little black cormorants, royal spoonbill and striated heron.

Black swan at Coombabah Lake, provided by Robert Westerman

When the tide is low, the silty sandbanks of Coombabah Lake support many shorebirds but when the tide comes in and submerges the banks, the birds start to move to the edge of the lake or other locations. At high tide many move to roost sites away from the lake, sometimes using shallow areas in the creek. Whimbrels, terek sandpipers and sharp-tailed sandpipers will roost in mangrove trees. However, eastern curlews and bar-tailed godwits need a clear sandy place. On spring high tides, the birds often fly to the Broadwater or South Stradbroke Island.

Waterbirds at Coombabah Lake, photo Robert Westerman

Main Photo: Black-winged stilts and pelican at Coombabah - Provided by Robert Westerman

Watching Wildlife at Coombabah

Within the surrounding melaleuca swamplands and along the connecting creeks, other local birds such as the pied butcherbird, scarlet honeyeater, noisy miner, kookaburra, whipbird, superb fairywren, leaden flycatcher, willie wagtail, and various kingfishers have been observed.

The construction of raised footpaths, boardwalks, and bird hide locations within the Coombabah Lakelands Conservation Area provides an ideal opportunity to spot the many different bird species and other local wildlife. The large network of trails is a major highlight for bird watchers and those wanting to get a closer look into the varying and unique ecosystems. As well as a top birding hotspot on the Gold Coast, the area also offers sightings of koalas, eastern grey kangaroos, and red-necked wallabies, making it a diverse and appealing destination for wildlife enthusiasts.

For more information about bird watching locations within the Coombabah Lakelands Conservation Area, please Click Here.

Photo: Coombabah Lakelands Bird Hideout- Provided by Gold Coast City Council

Future Risks for Coombabah Sub-Catchment

One of the risks associated with the Coombabah sub-catchment revolves around rising sea levels. This potential alteration in lake and estuary depth and extent poses a direct threat to the intertidal ecosystems and wetland values. Notably, sea levels within Coombabah Lake have already reached the level of the previous Holocene High Stand, making it crucial to manage any additional water level rise effectively to prevent adverse effects on the surrounding landscapes.

Climate change introduces another layer of risk, particularly in the form of severe weather events. Storm surges, capable of increasing sediment load through tidal inundation and excessive runoff from the sub-catchment's surroundings, further exacerbate potential challenges and changes to the system.

Adding to the complexities, the catchment is identified as a hotspot for future development, which can present a risk to its wetland values. Increases in population density bring secondary inputs into the systems, subsequently impacting water flow, velocity, and quality. Planning for future development and associated infrastructure such as road upgrades requires designated buffer zones and areas for rehabilitation to mitigate potential negative impacts.

Main Photo: Coombabah Lake View Sunset - Gold Coast Tourist Parks

Ongoing Management & Monitoring of the Coombabah Sub-Catchment

The Coombabah Creek sub-catchment is considered to be important area for biodiversity in the Northern Gold Coast region. Its story showcases how natural and modified features within the landscape can impact how water flows. This unique system demonstrates resilience and adaptation to natural climatic events such as drought and flood. The dynamic ecosystems throughout the sub-catchment may undergo physical and chemical changes in response to these events, but generally recover or evolve over time. While droughts and floods can pose challenges to human settlements, they are intrinsic to the natural water cycle of wetlands. The observed siltation within the Coombabah Creek system during the dry period from 2016 to 2019, highlights the system's sensitivity to fluctuations in water availability. However, recent studies between 2019 and 2021 indicate that the water quality, sediments, and macrobenthic communities within the Coombabah system are in a relatively healthy state.

It's essential to recognise that historical alterations to the site's hydrology, driven by increased settlement and urbanisation since the 1970s, have significantly impacted the movement of water within the system, and influenced vegetation communities. Looking ahead, flood and drought events as well as predicted climate change and rising sea levels are expected to further transform the Coombabah system. The expansion of mangroves is anticipated at the expense of saltmarsh and marine couch communities, with further potential losses of coastal freshwater wetlands and terrestrial vegetation. An increase in urban density also poses further constraints on the system, emphasising the ongoing challenges and changes the Coombabah system will face in future.

Ongoing research, monitoring and management are required to ensure that the values within the sub-catchment are protected and that any changes to the downstream processes of these differing systems have minimal impact on the ecosystems that rely on it. Knowing how the sub-catchment functions, adapts and changes over time is important for future planning, including climate resilience. With this knowledge, we can make better decisions about how we manage our sub-catchments and protect our coastal ecosystems.

Main Photo: Coombabah Lakelands Saltmarsh and Ponding - Provided by Ralph Dowling

Acknowledgements

Developed by the Queensland Wetlands Program in the Department of Environment and Science in collaboration with:

• The Queensland Herbarium and Biodiversity Science
• Jon Knight – scientific advisory role
• The Queensland Hydraulic Laboratory
• Griffith University
• The City of Gold Coast Council (CoGC)
• Queensland Parks and Wildlife Service (QPWS)
• Department of Transport and Main Roads (TDMR).
• Justine Dillion - Kombumerri Noonuccal Ngugi Gorenpul Traditional Owners
• Kombumerri Rangers
• Kombumerri Country and People

This resource should be cited as:

Walking the Landscape – Coombabah Creek Sub-Catchment Map Journal v1.0 (2024), presentation, Department of Environment, Science and Innovation, Queensland.

Photos provided by:

• City of Gold Coast
• Queensland Government
• Ralph Dowling
• Robert Westerman
• Gary Cranitch © Queensland Museum

The Queensland Wetlands Program supports projects and activities that result in long-term benefits to the sustainable management, wise use and protection of wetlands in Queensland. The tools developed by the Program help wetlands landholders, managers and decision makers in government and industry.

Contact: wetlands@des.qld.gov.au

or visit: https://wetlandinfo.des.qld.gov.au

Disclaimer

This Map Journal has been prepared with all due diligence and care, based on the best available information at the time of publication. The department holds no responsibility for any errors or omissions within this document. Any decisions made by other parties based on this Map Journal are solely the responsibility of those parties. Information contained in this Map Journal is from a number of sources and, as such, does not necessarily represent government or departmental policy.

Data source, links and information

ArcGIS for Desktop | ArcGIS Online | Story Map Journal 

Some of the information used to put together this map journal can be viewed on the QLD Globe.

The Queensland Globe is an interactive online tool that can be opened inside the Google Earth™ application. Queensland Globe allows you to view and explore Queensland spatial data and imagery. You can also download a cadastral SmartMap or purchase and download a current titles search.

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Last updated: 19 June 2024