Catchment Action Plan: Mid Brisbane  

Site: Glamorgan Vale Rd  

Area: 8 ha  

Date Planted: May 2022  

In 2014 Ipswich City Council (ICC), in partnership with multiple stakeholders and the local Marburg community, produced the Upper Black Snake Creek Improvement Plan (UBSCIP). A whole-of-system values-based approach identified catchment salinity as a key threat to water quality of the Brisbane River and the Mount Crosby Treatment Plant, potentially impacting on water supply. Seqwater monitor this threat at multiple sites on Black Snake Creek and downstream of the confluence with the Brisbane River. The UBSCIP identified multiple objectives: for this project including reducing salinity and sediment, as well as flood risk.  

A site investigation and an implementation plan were undertaken, with the initial work site chosen primarily because the landholders had an interest in rehabilitating country. The site is highly visible, with a broad channel arrangement and significant exposed earth, so any changes due to the rehabilitation efforts will be pronounced. A geomorphic investigation of the site was undertaken.  

The investigation identified most of the degradation within the channel and floodplain was likely due to subaerial erosion processes primarily from cattle impacts. Cattle pugging can strip topsoil and groundcover, creating concentrated flows within the floodplain and stream banks. The lack of groundcover in these impacted areas makes them prone to the impacts of rainfall splash, runoff and stream flow, leading to degradation of the channel and floodplain. There was no major evidence of fluvial scour or mass failure processes within the channel, most likely due to the low stream power and low bank heights.  

Based on this assessment, catchment officers recommended the removal of stock from the floodplain and riparian zone. Riparian and floodplain vegetation was planted to improve the bank and floodplain condition over time, and ultimately reduce erosion and improve flood mitigation. Planting included deep-rooted vegetation to lower the saltwater table and reduce salinity downstream over time.  

The planting area was fenced and cattle removed; with an initial planting flooded soon after being laid down. The flood did minor damage and required debris removal but as it was slow moving, across a broad floodplain, the flood is now seen in hindsight as an element of the success of this planting. The areas planted and flooded have achieved exceptional growth in comparison to other sites in the district and those planted on this site shortly after the rain event.  

A spectacular aspect of this project is the recovery of the landscape and the coverage of the couch grass once the cattle were removed. The improved health and vibrancy of the site post-rehabilitation can be seen by the diversity of flora and fauna now observed at the site.  

Twelve months after completion the entire exposed area is now completely covered. This high level of cover will reduce erosion and improve flood mitigation in future rainfall events.  

Now in its fourth phase, projects under the UBSCIP have led to more than 40,000 trees being planted across 10 properties. Critical success factors for this project were clarity of communication with landholders as well as project partners and contractors, quality site investigation to inform robust design for the site, oversight of the contractor in the implementation of the site preparation, and planting to ensure the design was implemented appropriately while meeting landholder needs.