Restoring Tygum Lagoon
Home to more than 280,000 people from at least 185 different cultures, Logan City is a young municipality located between Brisbane, Ipswich and the Gold Coast. The area, recognised as one of Australia’s most diverse cities, is a mixture of new estates, revitalised older suburbs and thriving commercial, retail and manufacturing precincts, hosting abundant service and wholesale industries.
The City holds many important and diverse wetlands, featuring complex and highly productive ecosystems providing key ecological and hydrological functions such as biodiversity conservation, flood mitigation, and water quality improvement.
All the catchments within Logan City drain to and are directly connected with Moreton Bay, a Ramsar Site of international importance. Acutely aware of the importance of its many Wetlands from a recreation, aesthetic and cultural heritage perspective, Logan City Council is actively engaged in enhancing its management practices throughout the catchment to protect these vital systems from detrimental impact and further degradation.
In keeping with that aspiration, the Council has been working with BMT WBM and PLACE Design Group to rehabilitate Tygum Lagoon, a shallow open water lake situated adjacent to the Logan River in Waterford West. The project has been so successful that it won a ‘Merit Award’ in the ‘Excellence in Infrastructure’ category at the recent annual Stormwater Industry Association of Queensland Awards for Excellence.
Prior to the commencement of the rehabilitation project, Tygum Lagoon was reported to have “relatively limited aesthetic, recreational and environmental values”.
In 2007, a rehabilitation strategy for the lagoon was developed by BMT WBM (on behalf of Logan City Council) “to restore and maintain the recreational and environmental values of Tygum Lagoon”. This strategy was undertaken in two parts: (1) condition assessment report and (2) strategy report.
The ‘Condition Assessment Report’ provided an assessment of the current condition of Tygum Lagoon, including aspects such as water quality, sediment quality, bathymetry, flora and fauna. The assessment also identified key management issues and formed the platform for the subsequent development of this ‘Strategy Report’.
The strategy report was subsequently developed to provide an assessment of potential remediation actions, and describes the recommended rehabilitation strategy for the lagoon, including conceptual design(s), staging plan and cost estimates associated with these actions/designs.
eWater’s urban stormwater modelling software, music (model for urban software improvements conceptualisation) was used throughout the project, highlighting key management issues for the lagoon and to assess the performance of various stormwater management strategies. For example, music showed that an adjacent road area was the largest contributor of stormwater pollutant loads into the lagoon, and was used to assess various strategies to reduce stormwater pollutant loads entering the lagoon from this area.
The Rehabilitation Strategy was designed to encompass a whole of catchment approach to waterway restoration and included effective collaboration both within Council (Branch liaison) and externally with Park users and the adjacent community.
The recommended rehabilitation strategy for the lagoon included the following:
• Stage 1 – Reduce stormwater pollutant loads and enhance lagoon outlet
• Stage 2 – Community engagement, promotion of usage & reduction of exotic fish
• Stage 3 – Improve aquatic habitat values
• Stage 4 – Fish stocking
The strategy subsequently informed the Tygum Lagoon Master Plan which is now the overarching planning tool to support effective water sensitive urban design outcomes, managing the interface between the lagoon and the surrounding natural and urban environments. Developed through a highly successful and phased community consultation, the Master Plan advocates a water sensitive urban design methodology integrating water quality outcomes with the requirements of regional and localised open space networks, accessibility, biodiversity considerations and overall connectivity with the Logan River.
Aspects of the Master Plan include:
• the provision and enhancement of habitat for local fauna around the lagoon (low grassland, marshland, low thickets, tall riparian vegetation) to encourage increased fauna presence
• the restriction of general access to key habitat zones
• the encouragement of community involvement in the revegetation of key habitat zones and vegetated links to other parts of the open space network
• the establishment of edge planting to intercept rural land or road runoff
• the establishment of tall stands of vegetation at strategic locations to filter strong winds and reduce water turbidity
• improving access by local schools / interest groups for monitoring and rehabilitation works to enhance education experience.
The majority of the recommended actions (given in the ‘Strategy Report’ and ‘Master Plan’) have now been implemented. As a result, the recreational and environmental values of the lagoon have significantly improved.
The rehabilitation of Tygum Lagon has been an overwhelming success, and demonstrate what can be achieved for similar water-bodies requiring remediation.