The Hunter-Coquun estuary: bioregional thinking as spatial determinant

- Perez Lopez, Irene

Title
The Hunter-Coquun estuary: bioregional thinking as spatial determinant
Creator
Perez Lopez, Irene
Publisher Link
http://dx.doi.org/10.25817/xzj4-ny66
Resource Type
still image
Description
The Hunter River and its Estuary are part of the Hunter Bioregion, within the Sydney Basin, a distinct geographical, geomorphological, biophysical, climatic, ecological, and cultural region (Figure 1 – Hunter Bioregion). Newcastle is the largest urban centre in the Hunter and the second settlement established by colonisers in 1804. The Traditional Custodians of the Land are the Awabakal people on the southern bank of the river, the Worimi people on the northern bank, and the Woonarua people inland. In this section of the coast, geology, hydrology, and sedimentary processes formed the lowlands and the coast, resulting in different types of estuaries presented in Figure 2 – Hunter-Central Coastal Estuaries, based on the different depositional processes and barriers formation. As illustrated in Figure 3, the Hunter Estuary Hydrology is covered by a complex hydrological system, formed by two barrier systems, the Tomago-Tomaree, and the Stockton Sand beds, defining an inter-barrier depression forming the Hunter Wetlands National Park, listed under the Ramsar Convention. The more extensive aquifers in the bioregion are situated below the inner and outer barrier, receiving the highest rate of recharge in the region. Early chronicles reveal exuberant biodiversity, describing a river with rich alluvial soil, exuberant riverbanks, short tender grass clear of trees, and dense eucalypt dominated forest with “immense gum and iron-bark trees, giant cedars and graceful wattles”. Mining, farming, and grazed modified pastures transformed the Hunter, resulting in over 85% of the native vegetation lost, only 40% of forested areas retained, and 99% of riparian vegetation removed from the river and its tributaries. The suburb of Corrumbah–Carrington, is strategically located on the Coquun–Hunter Estuary, three kilometres west to the mouth, facing Thorsby and Cottage creeks on its west side and the river basin and the estuary’s mouth on the east. Like the rest of the riverine waterfront, Carrington has suffered a drastic modification of its geomorphology and ecology. Early historical maps, chronicles, and environmental history reports reveal several riverine tidal islands over the estuary dominated by low and swampy grounds fringed with mangroves and dense vegetation of banksias or honeysuckles, tee trees, and swamp oaks. The area, originally accessible only by boat or foot in lower tides, is being progressively infilled by ballast and the dumping of industrial waste, accumulating at least two meters resulting in the connection to the mainland on the north. Carrington sits in the terrain of water’ despite the land reclamation and infill. Too much water or not enough water and the intensification of storms and extreme climatic events dominate its history, becoming its major vulnerability. The engineering of the river to control flooding after one of the most devastating natural disasters in Australia’s history, the 1955 Maitland floods, is partly responsible for changes in the river’s basin and flow dynamics. Natural levees have been substituted by hard edges throughout the construction of channels and flood levees that have deprived the river of new layers of alluvial soil and eradicated riparian vegetation. Floods are influenced by river and creek flooding episodes, tidal influence, oceanic inundation from high ocean tides and storm surges, and the projected impacts of sea level rise – projections show that 80% of Carrington will permanently be below sea level by 2100, as presented in Figure 4 (Hunter Estuary Risk Management Plan). Adaptation in Carrington requires a multiple-action approach, including responses to weather variability to cope with alternating dry and wet periods; the transition into a climate-resilient suburb model through new models of inhabitation and infrastructures; the improvement of water performance in the built environment by living with less water and optimizing water usage; and the restoration and expansion of the riverine ecological corridors. The public domain offers opportunities to develop a blue-green public water-sensitive network of roads and pedestrian pathways, public spaces and parks, and water bodies, which aligns with flood adaptative development strategies, as illustrated in Figure 5 – Carrington Blue-Green Infrastructures. These require the coordination of strategies to adapt to four different scenarios: no rains and droughts, flooding associated with storm runoff and overflows, flash flooding from creeks, river flooding episodes, and ocean flooding from high water levels in the ocean and harbour, typically as a combination of big tides and storm surge and sea level rise. The landscape strategy takes the form of a ‘blue-green buffer’—forming corridors connecting Carrington with Throsby Creek and beyond. The western part of Carrington, facing Throsby Creek, is primarily public land, public spaces, or neglected and polluted industrial land. The strip provides ‘space for the river’, acting as a blue-green buffer for Thorsby Creek flash events or flooding episodes in the Hunter-Coquun catchment. Simultaneously, the area serves as space to retain, treat, and store water, rainwater, and runoff while offering recreational, cultural, and environmental opportunities. Design strategies combine Water Sensitive Urban Design (WSUD) and Alternative (or Nature-based) Flood Defence to generate blue-green corridors and urban spaces acting as buffer zones to protect the urban environment and enhance natural water systems. This helps manage runoff, reduce urban heat island effects, and guarantee urban ecological connectivity to foster biodiverse corridors for flora and fauna since major environmental pressures in Newcastle LGA include the fragmentation of fauna habitats with limited integration of these in planning locally. The scale of this public space buffer creates opportunities to construct green embankments and levees, terraced floodable wetlands, and floodable parks planted with mangroves and submergible planting for aesthetic and water treatment purposes, as illustrated in Figure 6 – Carrington Detail Section.
Subject
ecological design; estuary urbanism; climate adaptation; living infrastructures; Hunter River Australia
Identifier
http://hdl.handle.net/1959.13/1506080
Identifier
uon:55810
Rights
© The Author(s) 2024. These works are licensed under the CC BY-NC-ND 4.0 license (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Language
eng
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Thumbnail File Description Size Format
ATTACHMENT01 Hunter River Bioregional Scale 3 MB PNG Image
ATTACHMENT02 Central Coast - Hunter Coastal Estuaries 1 MB PNG Image
ATTACHMENT03 Hunter River Estuary Hydrological systems 1 MB PNG Image
ATTACHMENT04 Hunter Estuary Hydrological System and Flood maps 2 MB PNG Image
ATTACHMENT05 Carrington Blue and Green infrastructure network 3 MB PNG Image
ATTACHMENT06 Carrington 826 KB PNG Image
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