RURAL REGENERATION - biodiversity, native flora sanctuary
Victorian Desalination Plant
The Victorian Desalination Project green roof is the largest in the southern hemisphere. It covers a number of buildings of the process plant, ranging in pitch from 3.5 to 20 degrees. The undulating slopes of the roof are designed to limit visibility of the industrial buildings from the surrounding public areas and link to the nearby coastal landscape.
The Victorian Desalination Plant provides for desalinated water to be delivered from the private sector to the State Government owned water authorities. The plant is capable of supplying up to 150 billion litres of water a year to Melbourne, Geelong and via other connections to South Gippsland and Western Port towns.
read more courtesy of Aspect Studio Melbourne
The VDP is has been established for two years and growth of endemic species has been strong. By all accounts this project has been both a success in development of low profile extensive metal deck roofs, and the use of endemic plant species on a large scale. The VDP does require harvested stormwater for irrigation to make a successful living roof on the 180mm soil profile. It does also require a high performance low organic, mineral based soil mixture for providing the best growing conditions and a soil mixture that is durable with minimal breakdown.
High levels of wind sheer were expected for the site. These were factored in by designing in the use of a stainless steel mesh over soils, to mitigate lifting of the stone mulches and plants. Planting design incorporated zoning these areas and incorporating species from high wind sheer habitats. Wind exposures have been measured on two separate storm events, post installation, achieving 115km/h speeds. Damage was minimal-to-none, notably with no shift in mulches or the soil profile.
Luckily extreme wind exposures were incurred after sufficient plant establishment had taken place, to allow groundcover species to root at internodes and aid in wind stabilisation.
Over a two year period, species colonies and composition have naturally altered to suite exposures, in terms of wind and sun. Very high exposure areas have transitioned to predominantly low-growing groundcovers, tussocks, compact shrubs and ephemeral forbs.
Establishment
Establishment, due to winter planting, presented notably high levels of foliage coverage quite early. Within the first year seed recruitment of various ephemeral forbs and small shrubs become apparent and notable. In particular Correa alba, Olearia axillaris, Rhagodia candolleana and Senecio spathulatus.
Drought Impacts
Severe hot and dry periods did impact the garden within the first year, presenting minor die-back. Regeneration rates were high, allowing for virtually complete regeneration by the second year. Certain aspects proved to be exposed to dryer winds, whilst others proved notably more protected, each respectively presenting a natural alteration to the species composition, as a coping mechanism.
Species dominances have shifted more so in high exposure areas, with one large section slowly reducing to a Carpobrotus/Tetragonia combination to great effect. This is interesting as this dominance also predominates in the secondary sand-dune zone within local EVC's. Therefore the roof is showing a directly comparable response to surrounding habitats. (coastal dunes)
Overall
The successful use of these particular indigenous species, lies not in the assessment of each species in isolation for suitability for green roof use, rather in the ecological functioning of all the species in unison. Dominances, reductions and re-colonisation, are providing coping mechanisms to a plethora of exposure challenges, and are integral to this Australian green roof design solution.
Considering the amount of risk involved in pursuing a completely indigenous species design solution on this scale, without existing Australian Green Roof Design standards, this project is providing successful responses to myriad and extreme exposure challenges.