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Natural Area was contracted by the City of Vincent to undertake planning, design and on ground restoration works at Walter’s Brook, Banks Reserve. The brook had become degraded due to large sediment deposits washing in from drain outlets and severe bank erosion due to inappropriate alignment of the drainage channel.
On-ground works followed restoration plans designed by Natural Area and Urban Serenity. Erosion in the area was mitigated with a combination of soft and hard engineered techniques. Straightening of the drainage channel through the installation of gabion walls and gabion mattresses has diffused the impact of running water through the channel and reduced bank erosion. Sections of the bank were recontoured to create a low gradient slope; these banks were covered in a biodegradable erosion control matting to prevent the establishment of weeds and to temporarily stabilise the soil whilst revegetation works establish.
The restoration design plan was prepared in early 2013 with assistance from Urban Serenity. The plans and specifications for gabion cages and mattresses were certified by a consulting engineer.
Initial works commenced in early 2014 and included regrading, removal of some non-endemic trees, removal of wooden palisades and turf. Site works were supervised by an ATCO representative due to the proximity of a HP gas pipeline. Trees were mulched on site and removed. Sand material was stored for re-use on site. The site was treated as potential for ASS and all spoil was treated on site before being reused or removed.
Gabion mattresses and gabion baskets were both used in this project. Mattresses were galmac coated, double twist mesh and baskets were link weldmesh with galfan coating. Mattresses and baskets were assembled on site and filled with limestone (80-200mnm diameter)
A rock revetment was installed to protect an old Morton Bay Fig with cultural significance. Degraded palisades were removed and a new rock revetment was installed. Works in this area were undertaken by hand due to the significance of the tree.
A limestone rock spillway was installed at the headwall of the drain to prevent scouring in the area due to increased drainage flow.
Following construction works, the recontoured banks of the channel were revegetated using native species at a density of 1 plant per square meter. At the top of the channel, sedges were planted at a density of 5 plants per square meter. Revegetation planting increased the visual amenity of he are as well as providing a biofilter to runoff entering the channel from the reserve.