Monthly Archives: May 2015

Wompoo Gorge Lowland Subtropical Rainforest Restoration Project, Coopers Creek, New South Wales

Key words : Connectivity, Lowland Subtropical Rainforest, Threatened Species

Introduction. Much of the state- and nationally listed Lowland Subtropical Rainforest at Wompoo Gorge, located on Coopers Creek near Rosebank, was partially cleared for pasture early last century. Parts of the cleared forest regenerated naturally with the removal of agricultural activities from the site during the 1940s-50s, but Lantana (Lantana camara) established in large gaps (Fig 1) and prevented any further rainforest regeneration. This weed domination reduced the function of an important habitat linkage between Nightcap and Goonengerry National Parks. Twenty-seven threatened species (10 threatened flora species and 17 vulnerable animal species) have been recorded on the site, which has been identified as a key climate change and wildlife corridor.

In 2009 a program of ecological restoration commenced, guided by the recommendations of the Wompoo Gorge (South) Ecological Restoration Plan (updated in 2013). The aim of the restoration works was to control Lantana and other weeds, restoring the integrity of the rainforest and helping to supporting the region’s exceptional biodiversity.

A monitoring program was established on site prior to commencement of works. This included eight transects and photopoints. Structural and floristic information has been collated and photos taken prior to the commencement of works, and subsequently over the course of restoration work. Data have been entered into then MERV (Monitoring and Evaluation of the Restoration of Vegetation) database and used to produce reports.

Figure 1. (map) Lantana cover prior to restoration. By 2014 very little lantana remained with regenerating rainforest taking the place of weeds.

Figure 1. (map) Lantana cover prior to restoration. By 2014 very little lantana remained with regenerating rainforest taking the place of weeds.

Works undertaken: Lantana has been controlled by a range of methods (Figs 2-4) including: mechanically with a tractor; spraying with a splatter gun; over-spraying dense, less accessible areas; hand weeding with brush hooks and loppers; and, cut/scrape and paint of scattered Lantana among remnant vegetation. Other less dominant weeds have been controlled to facilitate replacement of Lantana with regenerating rainforest. Follow-up work includes flattening down dead Lantana, spot spraying and hand weeding. No planting has been undertaken but fruit from native plants on site has been collected and spread throughout regeneration areas.

Figure 2. September 2009: Prior to lantana control

Figure 2. September 2009: Prior to lantana control

Figure 3.  17 September 2009: Tractor crushes down lantana

Figure 3. 17 September 2009: Tractor crushes down lantana

Figure 4. 21 October 2009: Second tractor run slashing lantana

Figure 4. 21 October 2009: Second tractor run slashing lantana

Results: Lantana has been virtually eliminated from extensive areas and vigorous regeneration of a high diversity of species has occurred (Figs 5-6). Common regenerating species include: Poison Peach (Trema aspera), Red Cedar (Toona ciliata), Giant Stinging Tree (Dendrocnide excelsa), Tamarind (Diploglottis australis), Sandpaper Figs (Ficus coronata) White Cedar (Melia azedarach) Bangalow Palm (Archontophoenix cunninghamiana), Brown Kurrajong (Commersonia bartramia), Pencil Cedar (Polyscias murrayi), Celerywood (P. elegans), Quandong (Elaeocarpus grandis) , Black Bean (Castanosperma australis), Sally Wattle (Acacia melanoxylon). Groundcovers included Soft Bracken Fern (Calochlaena dubia), Cunjevoi (Alocasia brisbanensis) Juncus (Juncus sp.), Cyperus (Cyperus spp.) and Basket Grass (Oplismenus aemulus). A range of later stage rainforest species have also germinated including Hairy Walnut (Endiandra pubens), Maiden’s Blush (Sloanea australis) and White Bolly Gum (Neolitsea dealbata).

Figure 5. ‘’Oct 2010: Resilient native regeneration in tractor cleared area

Figure 5. Oct 2010: Resilient native regeneration in tractor cleared area

Figure 6. May 2014: Natives have replaced lantana throughout cleared area

Figure 6. May 2014: Natives have replaced Lantana throughout cleared area

What we have learned. Wompoo Gorge has proven to be a highly resilient site, located as it is between two major sources of propagules. The site’s unique location, resilience and beauty has made it an ideal site to educate and inspire the community to restore rainforest Field days held on site have assisted in raising regional awareness of the value of the Lowland Rainforest EEC, the habitat it provides and of the degrading impacts of weeds. Various weed control techniques have also been discussed and demonstrated. Involving Green Army participants alongside professional regenerators has helped Green Army participants gaining valuable knowledge, skills and training in ecological restoration.

In 2014 NSW National Parks and Wildlife Service acquired the property realising the goal of former property owner Dailan Pugh to protect the property in perpetuity for the benefit of conserving native species and for future generations.

Acknowledgements: The project has received funding from the NSW Environmental Trust’s Restoration and Rehabilitation program. Additional funding has been invested through the former Northern Rivers Catchment Management Authority, the Great Eastern Ranges Initiative and a Raymond Borland Landcare grant. In 2015 Green Army teams have commenced working on site, alongside professional bush regenerators, undertaking additional and complimentary restoration works.

Contact: Paul O’Connor, Technical Manager, EnviTE Environment, 56 Carrington Street (P.O.Box 1124) Lismore  2480 Australia.

Tel: +61 2 6627 2841 Mob: + 61 427 014 692. Email: paulo@envite.org.au

 

Twelve years of healing: Rehabilitating a willow-infested silt flat – Stormwater Management.

Alan Lane

Key words: urban stream, erosion, siltation, soft engineering, head wall

Introduction: Popes Glen Creek is a small permanent stream rising close to the centre of the township of Blackheath, NSW, Australia. Its upper catchment (10 ha) comprises low-permeability urban development, roadways, shops and parklands.

The funneling of runoff from the low-permeability catchment into the headwaters of Popes Glen Creek resulted in intense and destructive runoff after rain, carrying down large and small debris, depositing sheets of silt, uprooting or burying vegetation, causing erosion of the creek banks and threatening to undermine the head wall of the silt flat downstream. This resulted in the formation of a 1 ha silt flat at the headwaters of the creek, covered with dense infestations of mature Crack Willow (Salix fragilis), Purple Ossier (S. purpurea) and mid-storey and ground-layer weeds. This has been revegetated as a permanent wetland as described in a previous summary (https://site.emrprojectsummaries.org/2015/02/22/)

This summary describes the runoff management aspects of the project, where the aims were:

  1. to reduce the impact of runoff
  2. to reduce the incursion of silt
  3. to remediate the main channel
  4. to stabilise the head wall.
Fig 1: Notched weir diverting water towards sedimentation pond.

Figure 1: Notched weir diverting water towards sedimentation pond.

Figure 2: Sedimentation pond

Figure 2: Sedimentation pond

Works carried out:

1. Diversion of part of the flow and capturing sediment. A diversion channel was constructed with flow regulated by a notched weir in the main stream. This diverts approximately half the volume of the flow into a sedimentation pond were silt is captured, reducing the quantity deposited downstream (Figures 1 and 2).

2. Construction of low-impact detention cells. “Soft engineering” detention cells constructed across the silt flat from coir logs and woody debris found on site retain and slow the release of flow, dispersing it across the silt flat and raising the water table, suppressing weeds and supporting the vegetation of the created wetland (Figures 3 and 4).

3. Elimination of the highly incised main channel. Natural debris falling into the main channel creates a series of small pondages. These retain and slow the flow and allow overflow to disperse across the silt flat. (Figure 5).

4. Protection of the creek banks. Dense plantings of deep-rooted swamp vegetation e.g. Red-fruited Saw Sedge (Gahnia sieberiana) and Black Wattle (Callicoma serratifolia) (Figure 6), and loosely woven structures constructed from woody debris (Figure 7) protect creek banks and silt flat from erosion and scouring.

5. Stabilisation of the headwall. Contractors employed with funds from the Environmental Trust have constructed a major structure with railway sleepers and rock armouring to stabilise the head wall (Figures 8 and 9).

Figure 3: Volunteers building a detention cell from woody debris found on site.

Figure 3: Volunteers building a detention cell from woody debris found on site.

Figure 4: Raised water table enabled wetland sedges (Carex gaudichaudiana and Eleocharis sphacolata) to displace Creeping Buttercup (Ranunculus repens).

Figure 4: Raised water table enabled wetland sedges (Carex gaudichaudiana and Eleocharis sphacolata) to displace Creeping Buttercup (Ranunculus repens).

 

Lessons learned and future directions:  This project is on track to replace the forest of willows with wetland vegetation, transform a highly incised creek and weed-infested silt flat into a healthy Upper Blue Mountains Swamp – an endangered ecological community scheduled under the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999.

The volunteer group will continue working with Council and contractors to complete the planting program and to monitor the evolution of the site, including its vegetation, water quality and colonisation by macroinvertebrates, birds and frogs.

Stakeholders and funding bodies: This work is supported by a grant from the Government of New South Wales through its Environmental Trust and by the Blue Mountains City Council,  which also oversaw the engineering works. All photographs: Alan Lane and Paul Vale.

Figure 5: A natural pondage formed when debris was allowed to remain in the stream.

Figure 5: A natural pondage formed when debris was allowed to remain in the stream.

Figure 6: Dense plantings of Black Wattle (Calicoma serratifolia) and Gahnia (Gahnia sieberiana) protect creek banks from erosion.

Figure 6: Dense plantings of Black Wattle (Callicoma serratifolia) and Gahnia (Gahnia sieberiana) protect creek banks from erosion.

Figure 7: Volunteers using woody debris to protect the silt flat from scouring.

Figure 7: Volunteers using woody debris to protect the silt flat from scouring.

Figure 8: Part of the original head wall approximately 3 m high and 20 m wide.

Figure 8: Part of the original head wall approximately 3 m high and 20 m wide.

Figure 9:  Part of structure constructed to stabilise the head wall.

Figure 9: Part of structure constructed to stabilise the head wall.

Contact information: Dr Alan Lane, Coordinator Popes Glen Bushcare Group, PO Box 388, Blackheath NSW 2785, Australia. Tel: +61 2 4787 7097; Paul Vale, Deputy Coordinator Popes Glen Bushcare Group, 81 Prince Edward St, Blackheath NSW 2785, Australia. Tel: +61 2 4787 8080; and Ray Richardson, Chairman of Steering Committee, Environmental Trust Grant 2011/CBR/0098. Tel: +61 2 4759 2534.