Water Nymphs Dell Bushcare Group

Introduction

Water Nymphs Dell contains a significant area of rainforest and Blue Mountains Hanging Swamps and is an enchanting place to take a walk.

The area also has historical significance. In 1814 Lt. Cox's work party followed a trail of the first European Explorers that passed along the rim of Water Nymphs Dell basin. However, like many areas of bushland close to urban area, the site has suffered from weed invasion and pollution from stormwater runoff. The site has been the focus of a six-year bush regeneration contract under the Urban Runoff Control Program (URCP) and this was further extended by Blue Mountains City Council.

Water Nymphs Dell Bushcare Group 2002

The Bushcare Group in 2002: (left to right) Louise, Greg, Pat, Silvie (Felix), Toula, Morag

The Bushcare Group has been working since June 2000 and they have been integral in maintaining much of the work that has taken place. They meet each third Saturday afternoon on Taylor Ave, Wentworth Falls at 2.00pm. New members are always welcome.

Water Nymphs Dell Bushcare Group 2005

The Bushcare Group in 2005: Karen, Steve, Richard, Karen, Pat, Laura, Cassie, Morag, Rod.

Contract Summary

Summary of Works from January 2003 - November 2005

OBJECTIVE

  • To stabilise the silt flat to prevent it from being washed downstream
  • To maintain a barrier to trap weed propagules (protect area below waterfall)
  • To replace willows with a constructed community of local native swamp plants

STRATEGY IMPLEMENTED

Silt plug (area C)

Treat ground layer weeds such as Buttercup (Ranunculus repens) to prepare for planting.

Construct series of check dams to:

  • contain sediment in case of instability
  • divert and spread water flows
  • catch weed seeds

These were constructed over a period of time in order to monitor and adjust to changes in flows.

Establish sufficient plantings to stablise silt plug

  • by thinning out salix canopy to allow light in for growth of plantings but not too much to promote weed growth beyond ability to deal with it.
  • by weeding around plantings/native regeneration

Commence removal of Willow (Salix sp.) – to enable roots of plants to establish but not to destabilise silt plug by over clearing before the plantings have established.

Willow and Silt Plug area. A&S Contractors Karen Hising and Lyndal Sullivan explain to the group strategy used during their contract period. In the foreground is dried willow used for stabilisation and tubestock plantings. The background is an area a previous revegetation work. Photo: Chris Dewhurst

Perimeter areas (N, S and E)

Promote regeneration by comprehensive weeding

  • along northern and southern edges where good swamp vegetation exists
  • around groups of existing ferns

Protect Central area by comprehensive weeding a buffer between southern area (S) and central area (C)

Plant amongst weedy sections to establish canopy to shade out groundlayer weeds & comprehensive weeding around plantings [where possible replace Juncus microcephalus]

Target weed for woody weeds (except in locations where weeds specifically retained for site stability);

SITE ISSUES

Long periods of site inundation – making it difficult to establish tubestock and also to work without causing damage

Storm events – also contributing to plant losses

Groundlayer weeds limiting regeneration and outcompeting revegetation - Juncus microcephalus, Yorkshire fog

REVEGETATION

1650 tubestock planted were fertilised, mulched and tree guarded.

Monitoring is undertaken by using a marker system of coloured tree guard supports:

Uncoloured – Leptospermum polygalifolium
Square stake – Leptospermum juniperinum
Black - Blechnum nudum
Green - Grevillea acanthifolia
Red - Gahnia sieberiana
Yellow - Bauera rubioides
Brown - Pittosporum undulatum
White - Solanum aviculare

An assessment of plant losses would indicate that:

  • The failure of many plantings early in the contract was in the central willow silt plug area - possibly due to inadequate light, and may also have been to the crowded mass of roots.
  • It was important to position all tree guards to deflect water flows, in order to protect plants from the force of water and the debris it carries.
  • The tall narrow rigid tree guards were not successful as they restricted the development of sideways growth.
  • The species of plants which prospered the best in the silt plug/under the canopy of willows were Gahnia and Leptospermum polygalifolium.

In addition 625 of Carex gaudichaudianna and Baumea rubiginosa were transplanted

Recommendations

Future work in the area should continue the priorities of

  1. Monitor plantings to assess desirable rate of further treatment of willows (balancing need for light for plantings, threat of weed invasion and the loss of soil stability)
  2. Weed around all plantings
  3. Comprehensively weed under central willow area, and also along northern and southern edges around the perimeter where good swamp vegetation is located
  4. Target woody weeds throughout

Gallery

Teaching Louise and Felix about botany.
Photo: Chris Dewhurst

Chris (BMCC Bushcare Officer), Richard and Kit discuss the importance of clearing street gutters of sediment.
Photo: Greg Fitzgerald

Afternoon tea time after a Great Grose Gorse Walk session.
Photo: Chris Dewhurst