Lawson Creek is a significant mid-Mountains stream as it supplies moisture and nutrients to South Lawson Park, Blue Mountains National Park and the World Heritage Area, supporting flora and fauna diversity in these areas. It also contributes to the amenity of the popular and scenic bushwalking track between Adelina and Junction Falls. The Creek is a tributary of the Erskine Creek catchment.
Lawson Creek is perennial and 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. However the swamps further downstream are in a reasonable condition and as members of a protected ecological community (EPBC Act C’wlth 1999; Biodiversity Conservation Act NSW 2016) they are the subject of regular volunteer StreamWatch monitoring and ongoing bush regeneration work by a BMCC bush regeneration team.
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. This swamp stores and feeds a constant supply of water via Lawson Creek to two spectacular downstream waterfalls, Adelina and Junction Falls. At the latter falls the tributary Ridge Creek discharges into Lawson Creek. Cataract Creek merges with Lawson Creek a little further south. A further two kilometres south Lawson Creek discharges into Bedford Creek, which flows into Glen Erskine Creek to form Erskine Creek, which discharges into the Hawkesbury-Nepean River system.
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. The Creek slowly regained its natural forms and macroinvertebrate life returned to normal levels after several years.
To some extent this massive flow of sediments was a natural event resulting from very heavy rainfall, but 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 the flow to completely overwhelm the Creek.
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 adverse 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.
For further detailed reading see Lawson Creek Condition Report 2013 at http://bmcc.nsw.gov.au/sustainableliving/environmentalinformation/livingcatchments
The Greater Sydney Local Land Services website is also a useful resource: http://greatersydney.lls.nsw.gov.au
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 and weed seed flows into the upper reaches of Lawson swamp.
2018 has been a dry year, but some heavy showers in October 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.