Cox Creek Restoration Project

All willow species (Salix sp) and Desert Ash (Fraxinus angustifolia) are declared weed species under the Landscape South Australia Act 2019 because they are aggressive, colonising species of waterways, outcompeting and shading out native plants and aquatic wildlife. Native riparian trees allow 'dappled' sunlight through the canopy all year round, while Ash and Willow create dark shade which blocks light from the creek banks and water column during Spring and Summer. In Autumn, as Australia doesn’t have deciduous native trees (apart from one species in Tasmania), our waterways don’t cope well with the annual leaf drop of Willow and Ash into the watercourse, which dramatically increases nutrient loads and deoxygenates the water as the leaf litter decomposes. This decomposition and unnatural shade regimes also cause water temperature swings which native plants and animals are not adapted to cope with. As the Cox Creek catchment is a tributary to the Mount Bold Reservoir, this also has negative impacts on the water quality of Adelaide's water supply. In Winter, the bare trees allow full sunlight into the water, which again, disadvantages native aquatic species, as they are adapted to survive in dappled sunlight all year round.

Additionally, as both are 'thirsty' species which take up more water than native trees, they reduce environmental flows leaving less water for us and our native species. Willows also have a fibrous root system, trapping sediment and creating flat, shallow creekbeds. This alters creek flow and disadvantages native aquatic species, as many rely on the riffles and pools caused by naturally uneven creekbeds, allowing them to be outcompeted by introduced pest species.

Each site will be revegetated with a selection of the following species, depending on what is already surviving at each location.

Rushes, sedges and groundcovers

• Carex appressa, Tall Sedge
• Gahnia sieberiana, Red-Fruit Cutting-Grass
• Carex fascicularis, Tassel Sedge
• Juncus holoschoenus Joint-Leaf Rush
• Juncus pauciflorus, Loose-flower Rush
• Carex inversa inversa, Knob sedge
• Juncus subsecundus, Finger Rush
• Carex tereticaulis, Rush Sedge
• Juncus pallidus, Pale Rush
• Cyperus vaginatus, Stiff Flat-sedge
• Schoenus apogon, Common Bog-rush
  
• Carex breviculmis, Short-Stem Sedge
• Lomandra micrantha ssp. micrantha, Small-flower Mat-rush
• Lomandra multiflora ssp. dura, Hard Mat-rush
• Microlaena stipoides var. stipoides, Weeping Rice-grass
• Poa clelandii, Matted Tussock-grass
• Microseris lanceolata, Yam Daisy

Shrubs

• Goodenia ovata, Hop Goodenia
• Hakea carinata, Erect Hakea
• Hakea rostrata, Beaked Hakea
• Viminaria juncea, Native Broom
• Rubus parvifolius, Native Raspberry
• Bursaria spinosa, Christmas Bush
• Pultenaea daphnoides, Large-leaf Bush-pea
• Spyridium parvifolium, Dusty Miller
• Hibbertia spp, Guinea-flowers
• Xanthorrhoea semiplana ssp. semiplana, Grass Tree
• Acacia myrtifolia, Myrtle Wattle

Trees

• Acacia melanoxylon, Blackwood
• Eucalyptus dalrympleana ssp. dalrympleana, Candlebark Gum
• Eucalyptus fasciculosa, Pink Gum
• Eucalyptus viminalis ssp. viminalis, Manna Gum
• Banksia marginata, Silver Banksia
• Allocasaurina verticillata, Drooping She-oak
• Acacia provincialis, Swamp Wattle
• Leptospermum continentale, Prickly Tea-tree
• Leptospermum lanigerum, Silky Tea-tree
• Leptospermum myrsinoides, Heath Tea-tree

Replacing invasive weeds with native riparian species will improve important habitat suitable for many native plants and animals, including the Southern Brown Bandicoot, Bassian Thrush, Chestnut-rumped Heathwren, Yellow-footed Antechinus, Yellow-tailed Black Cockatoo, Rakali (native water-rat), Eastern Long-necked Turtle, Brush-tailed Possum, Bibron’s Toadlet, Pygmy Copperhead and a number of native fish species including Galaxias. Threatened plants that will be supported through the project include the Ploughshare Wattle, Mount Lofty Phebalium, Spotted Sun-orchid, Candlebark Gum, Manna Gum, and Pink Gum. Many declining woodland birds and invertebrates will also benefit from the project.

Yes, sometimes they do! Where Bandicoots are present and using Blackberry, a staged approach to weed removal will be undertaken, making sure that alternative habitat is available for the nationally endangered species before existing habitat is removed, even if it is a declared weed! The Bandicoot Superhighway Project put together this excellent Bandicoot habitat management guide to help landowners figure out how best to support Bandicoots on their properties.

Yes, we did! Adelaide Hills Council have been working with Trees For life for many years, and more recently the wonderful Bridgewater Friends of Cox Creek at Bridgewater Recreation Reserve to remove weeds and replace them with native plants, either through bushcare regeneration methods or revegetation where too degraded for regeneration to occur. A willow removal project at a small section of Cox Creek in the reserve was co-funded by a Landscapes Hills and Fleurieu Grassroots Grant. The area was revegetated with over 700 native plants at community revegetation events, planted a safe distance from the SA Water infrastructure underground in that area. This Urban Rivers Project builds on the gains of the previous project and complements Council's biodiversity works program and the tireless efforts of the volunteers that generously give their time to improve the biodiversity values of the site.