Lawson Creek

Lawson Creek is a significant perennial, Blue Mountains stream.

Lawson Creek Image: V Hong 2017
Lawson Creek Image: V Hong 2017
  • It supplies moisture and nutrients to  South Lawson Park, Blue Mountains National Park and the World Heritage Area.
  • The creek and its water supports flora and fauna diversity in these areas.
  • It contributes to the amenity and beauty of the popular and scenic bushwalking track between Adelina and Junction Falls.
  • The creek can be easily damaged by big stormwater flows, weeds, pollution and by careless and selfish 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

Lawson Creek and the surrounding bushland and park areas are community owned natural assets managed by Blue Mountains City Council and the NSW National Parks and Wildlife Service. The local fauna is protected, including the creek fauna. Unauthorised vegetation clearing or collecting of animals, plants and landscape features, such as rocks, flowers, seeds and timber, are not permitted.

Erskine Creek catchment Photo: V Hong
Erskine Creek catchment Photo: V Hong 2017

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.

  • Lawson Creek rises south of Lawson shopping centre and the GWH, via a series of minor tributary streams and drain lines that flow into a now quite altered swamp/lagoon complex.
  • Originally there were many fine swamps in this area but they are now largely degraded or non-existent, although the 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 then 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.

Click on an image to view Lawson, Ridge and Cataract Creeks.

Junctio Falls Lawson Creek. Photo: V Hong
Junction Falls, Lawson and Ridge Creeks 2017 Photo: V Hong
 

Sediments and siltation

Due to its proximity to urban areas and influences, Lawson Creek requires constant monitoring for adverse impacts, and bushcare activities provide this on-site monitoring role. Bushcare also significantly helps to mitigate these impacts, by improving surrounding natural vegetation quality, in much the same way that Sydney Water encourages the growth of the natural vegetation that borders and protects the sensitive Sydney water catchment.

The creek is in a broadly healthy condition, but the upper reaches are permanently stressed by regular adverse urban impacts such as weed growth and dispersal of its seeds.

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

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.

Bushcare Group members 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. 

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 debris will create good bug habitat, and a natural deep pool is already forming downstream of the log jam. 

Click on an image to view the recovery of Lawson Creek from the 2010 sediment event.

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. See Archives/Lawson Creek recovery.

Erosion

Creek banks and their adjoining riparian areas are very sensitive to any form of continual disturbance such as concentrated stormwater flows and overuse. 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, and excessive and careless use can be devastating, resulting in areas of stream bank becoming denuded of natural vegetation and eroded. Total bank collapse may occur. Weeds thrive in these disturbed situations.

Blechnum ferns stabilising Lawson Creek bank. October 2017

Blechnum ferns stabilising Lawson Creek banks, 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

In one case, excessive use resulted in a one hundred square metres section of Lawson Creek bank and adjoining riparian vegetation, above Adelina Falls, becoming severely damaged over the period 2016-2017. A wide section of swamp vegetation 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. However, it will take years for the natural vegetation to recover.

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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