Lawson Creek

Lawson Creek is a significant mid-Mountains stream:

  • it supplies moisture and nutrients to  South Lawson Park, Blue Mountains National Park and the World Heritage Area;
  • supports flora and fauna diversity in these areas;
  • contributes to the amenity of the popular and scenic bushwalking track between Adelina and Junction Falls;
  • is very beautiful;
  • can be easily damaged by big stormwater flows, weeds, pollution and careless use by people.
Lawson Creek catchment Source: The condition of upland swamps in the Blue Mountains, NSW, Australia: Stygofauna abundance and richness linked to the percentage of catchment impervious surface cover Nicole Ashby, Nicole Collas, Andrew McCormack and Natalie O’Donnell

Section of Lawson Creek sub-catchment. Source: The condition of upland swamps in the Blue Mountains, NSW, Australia: Stygofauna abundance and richness linked to the percentage of catchment impervious surface cover N Ashby, N Collas, A McCormack N O’Donnell 2011

The Creek is a perennial tributary of the Erskine Creek catchment. Lawson, Ridge and Cataract Creeks constitute a sub-catchment of Erskine Creek catchment. This catchment is a contributor to the extensive Hawkesbury-Nepean River system.

  • The Creek rises south of Lawson shopping centre and the GWH, via a series of minor tributary streams and drain lines that flow into a probably quite altered swamp/lagoon complex.
  • Originally there were many fine swamps in this area but they are now largely degraded or non-existent, although remnant peaty soils still contribute to surface seepage into the main stream.
  • After forming into a single, distinct channel, the Creek flows to Lawson Swamp, which is located approximately one kilometre south of the main Blue Mountains (GWH) ridge. Lawson Swamp is part of a protected ecological community (EPBC Act C’wlth 1999; Biodiversity Conservation Act NSW 2016) and is the subject of regular volunteer StreamWatch monitoring and ongoing bush regeneration work by a BMCC bush regeneration team. See: https://www.bmcc.nsw.gov.au/environment/waterways/swamps
  • Lawson Swamp stores and feeds a constant supply of water via Lawson Creek to two spectacular and popular downstream waterfalls, Adelina and Junction Falls.
  • At Junction Falls the tributary Ridge Creek discharges into Lawson Creek. A little further south Cataract Creek flows into Lawson Creek.
  • Finally, two  kilometres downstream, Lawson Creek terminates, discharging into Bedford Creek, which flows into Glen Erskine Creek to form Erskine Creek, which discharges into the Hawkesbury-Nepean River system.
Cataract Creek July 2018 (Photo P Ardill)

Cataract Creek, no erosion, no sediment! July 2018 (Photo P Ardill)

Federal Falls Cataract Creek, sediments, July 2018 (Photo P Ardill)

Federal Falls Cataract Creek, sediments, July 2018 (Photo P Ardill)

Cataract Creek catchment July 2018 (Photo P Ardill)

Cataract Creek catchment July 2018 (Photo P Ardill)

Ridge Creek July 2018 (Photo E Carmichael)

Ridge Creek, good condition! July 2018 (Photo E Carmichael)

Junctio Falls Lawson Creek. Photo: V Hong

Junction Falls, Lawson Creek 2017 Photo: Vera Hong

Erskine Creek catchment Photo: V Hong

Erskine Creek catchment, 2017 Photo: Vera Hong

Sassafras and Coachwood trees, Cataract Creek, July 2018 Photo: E Carmichael

Track, Sassafras and Coachwood trees, Cataract Creek, July 2018 Photo: E Carmichael

Siltation

Lawson Creek is in a broadly healthy condition, but the upper reaches are permanently stressed by regular adverse urban impacts such as weed growth, and these adverse impacts are often compounded in severity by specific degradation events. Such an event occurred in 2009-10, when a combination of heavy rains and massive stormwater flows, urban construction work, vegetation clearing and a collapsed track led to massive siltation of the Creek, upstream of Adelina Falls. Water flow was reduced to a trickle and macroinvertebrate life forms (bugs) disappeared for several years.

The bushcare group observed this situation and notified the BMCC bushland management team. Contractors were employed to install a series of rehabilitative sediment control structures in the Creek, to control sand flows and to create pools of water for bug habitat improvement.

To some extent this massive flow of sediments was a natural event resulting from very heavy rainfall. However, the concentration of stormwater flows into narrow pipes and gutters and other urban development factors such as the creation of hard surfaces and the removal of natural vegetation cover caused this dramatically increased flow to completely overwhelm the Creek.

Stormwater overwhelmed by sand Feb 2010

Lawson Creek pipeline overwhelmed by sand, Feb 2010  Photo: P.Ardill

Coir logging Feb 2010

BMCC contractors installed coir logging to enable sand dispersal, Feb 2010 Photo: P.Ardill

Main creek channel clogged by sand Aug 2010

Lots of sand, shallow depth, poor bug habitat. Lawson Creek August 2010 Photo: P.Ardill

Remediating collapsed track Sept 2010

BMCC contractors reconstructed a collapsed section of track, Sept 2010 Photo: P.Ardill

Due to its proximity to urban areas and influences, Lawson Creek requires constant monitoring for adverse impacts. Bushcare activities can provide this on-site monitoring role as well significantly helping to mitigate these negative influences by improving surrounding natural vegetation quality, in much the same way that Sydney Water uses natural vegetation to protect the sensitive Sydney water catchment.

Minimal sand, sandstone bedrock, healthy Spiny Crayfish. Lawson Creek, 2016

Minimal sand, sandstone bedrock, healthy Spiny Crayfish, Lawson Creek 2016 Photo: P.Ardill

Improved condition, Lawson Creek, Nov 2016. Much less sand, more vegetative matter, better bug habitat

Improved condition, Lawson Creek, Nov 2016. Much less sand, more vegetative matter, better bug habitat. Photo: P. Ardill

In 2016 BMCC bush regeneration contractors commenced swamp rehabilitation and stormwater control works at the eastern end of Ferris Lane, adjacent to the carpark. Large stands of Privet, a declared noxious weed, have been removed and a stormwater detention basin will be built, managing stormwater, sediment and weed seed flows into the upper reaches of Lawson swamp.

Unmanaged stormwater on track, flowing through weeds and carrying seed into Lawson Creek, Waratah Street, June 2007

Unmanaged stormwater  flowing through weeds and carrying seed into Lawson Creek and swamp,  June 2007 Photo: P.Ardill

Stormwater and swamp works, Ferris Lane, Lawson, Oct 2016

Stormwater and swamp works, Ferris Lane Lawson, Oct 2016 Photo: P.Ardill

 

Blechnum ferns stabilising Lawson Creek bank. October 2017

Blechnum ferns stabilising Lawson Creek bank, October 2017 (Photo: P Ardill)

Severe bank erosion downstream Lawson swamp December 2017 Photo: P Ardill

Severe bank erosion downstream  from Lawson swamp, December 2017 Photo: P Ardill

Natural debris, good bug habitat, Lawson Creek, October 2018

Natural debris, good bug habitat, Lawson Creek, October 2018 Photo: P Ardill

The silted section of Lawson Creek is steadily recovering. In October, 2018, heavy showers sent a minor flood down the Creek, carrying away sand and creating a log jam of natural debris. This will become good bug habitat and a natural pool is already forming downstream of the log jam.  Pictured below is the same site in October, 2010.

Silted main creek channel 2010

Silted main creek channel Oct 2010 Photo: P. Ardill

StreamWatch macroinvertebrate sampling in May 2019 revealed that bugs are starting to recolonise the silted section of stream. Mayfly nymphs (particularly sensitive to pollution) Damselfly nymphs, Dragonfly nymphs, Water Treaders (True Bugs) and Water Boatmen (True Bugs) were all present.

Erosion

Creek banks and their adjoining riparian areas are very sensitive to any form of continual disturbance as the soils are often fine silt sediments that erode easily, especially if the natural vegetation cover is depleted and after heavy rains. The long-term impacts of unregulated disturbance, trampling, excessive and careless use can be devastating, resulting in vast areas becoming denuded of natural vegetation and eroded. Severe bank collapse may occur. Weeds thrive in these disturbed situations.

Excessive use resulted in a 100 square metres section of Lawson Creek bank and adjoining riparian vegetation, above Adelina Falls,  becoming severely damaged over the period 2016-2017. Swamp vegetation many metres from the bank was trampled and the soil lost its natural cover. No swamps, no waterfalls! The BMCC Bush Regeneration Team remediated the damage by brushmatting the affected area, laying down layers of cut, natural vegetation to cover the bare areas and allow seed to scatter and germinate.

Brushmatting of Lawson Creek, Adelina Falls, showing bare stream banks. 2017 Photo: BMCC

Commencement of brushmatting of Lawson Creek, Adelina Falls, showing still bare stream bank and exposed tree roots at left Photo: BMCC 2017

Overuse resulted in swamp vegetation being destroyed and severe erosion along both banks of Lawson Creek above Adelina Falls 2016-17. Extensively brushmatted by BMCC Regeneration Team 2017-18. Photo: P Ardill March 2019

Section of remediated area of Lawson Creek above Adelina Falls. Photo: P Ardill March 2019

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