On behalf of City of Gold Coast (CoGC), Water Technology undertook an expert technical assessment (geomorphic condition assessment) and stakeholder consultation, with consideration of stream health condition, primary values and issues within the catchment areas. The outcomes of the assessment were used to prepare an Erosion Management Plan. The Erosion Management Plan aims were to:
- Identify the erosion processes occurring within each catchment,
- Outline general management techniques for each erosion process using specific examples from each catchment.
The technical assessment focussed on Wongawallan Creek, Guanaba Creek and Tamborine Creek with reference to present day processes of erosion/deposition, historic geomorphologic change, and likely morphologic trajectories (future changes) both under normal conditions and from flood events. The Plan was developed using various recognised stream management techniques including some aspects of RiverStyles® framework (Brierley & Fryirs, 2005). The management rationale and recommendations provided in the plan are assisting the City of Gold Coast to plan and implement river health projects, mitigate risks and improve the environmental condition of the Wongawallan and Guanaba stream networks.
Through and assessment of the creeks historic and current condition and processes, the likely future trajectory of the creek was assessed. The creeks are frequently controlled by bedrock, with bedrock bars and other exposed bedrock features (channel, bank, and floodplain) observed throughout the catchments. Increased storm frequency (or intensity) will exacerbate existing issues particularly where eroded bank faces are exposed. However, erosion issues within both catchments are acute issues, not widespread.
A vast majority of the stream network in both the Wongawallan and Guanaba Creek catchments were found to be in very good condition, showing high stability, in-channel complexity and resilience. However, active erosion processes are evident within both catchments. A majority of the observed erosion was associated with natural stream processes, exacerbated by land use changes, road crossings and changes in climate.