Natural Environment

The City of Whitehorse sits to the west of the Dandenong Ranges which greatly influences its weather and topography.

The City has a geology of predominantly sedimentary rocks forming low hills that, before development, were once covered in small expanses of grassland in the otherwise forested parts of Box Hill and Ringwood. The grasslands and wooded areas on these plains provided habitats for a range of animals and bird life. The area is also criss-crossed with waterways and alluvial flats providing wetland habitats for native wildlife.

Enormous flocks of kangaroo (mostly Eastern Grey) and emu were common on the alluvial flats of the Dandenong area in the 1830s. Bird life on the grasslands included Australian Bustard, Little Quail, Stubble Quail, Magpie, Nankeen Kestrel, Brown Hawk. Although few small animals inhabited areas lacking substantial ground leaf litter, the more open wooded grasslands supported species such as the Fat Tailed Dunnert, Gunns Bandicoot and the Plains Wanderer. Reptilian life included the Spinifex Lizard, at least three species of snake, and several skinks.

Geology and Geography

The geology of the City of Whitehorse almost exclusively comprises the gently folded marine mudstones, turbiditic sandstones and mass-flow conglomerates of the Lower Silurian Anderson Creek Formation. The folded sediments are most easily seen in the road cuttings in the side of the Eastern Freeway. It also has some minor Quaternary sediments confined to current waterways and drainage channels.

The geography of the City of Whitehorse comprises undulating terrain incised by creeks and watercourses. Most of the vegetation has been cleared for housing and industry however some natural vegetation is seen at bushland reserves and some road-side reserves.

Climate

The climate of Victoria, including the City of Whitehorse, is highly variable and influenced by large-scale climate drivers that occur on inter-annual timescales in the oceans surrounding Australia, such as the El Niño–Southern Oscillation and the Indian Ocean Dipole. In addition to this natural climate variability, increasing concentrations of Green House Gases are causing rising surface and ocean temperature and decreasing cool-season rainfall.

The City experiences mild to warm summers with an average maximum temperature of around 25°C. In winter, average maximum temperatures are mostly around 13 to 14°C. It falls within a temperate climate zone with no dry season and a warm summer. The region is susceptible to extended periods of hot and dry weather during summer. February is typically the hottest month of the year, with July the coldest. The City experiences temperatures greater than 35°C, on average, 11 days per year. This is predicted to increase to 16 days per year, on average, by 2050 with Melbourne’s ‘fire days’ projected to increase by 42% per year by 2050.

The main rain source for inland Victoria is from eastward moving frontal systems crossing the Southern Ocean. On average, the annual average rainfall is approximately 750mm, however, localised flash flooding may occur during the 15 days, on average, storm events that occur in late spring and early summer. Because topography and climate are intimately related, there is a corresponding east-west gradient in annual rainfall from up to 1400 mm in the eastern highlands around the Dandenong Ranges, and a low of 400 mm on the basalt plains in Melbourne's west.

Victoria’s winter rainfall has decreased by an average of approximately 100mm since 1990 and Melbourne (including Whitehorse) is expected to experience a drop in rainfall during spring of approximately 20% by 2050. This will likely have flow-on effects for summer bushfire seasons.

Waterways

The City of Whitehorse lies within the Melbourne Water catchment zone. The waterways of Gardiners, Dandenong and Koonung Creeks are significant environmental, landscape and recreation locations and form part of an advanced open space network that is highly valued by the community. These waterways are all tributaries of the Yarra River subject to occasional flash floods in intense downpours.

Gardiners Creek rises in the centre of the City of Whitehorse and flows through Blackburn, being fed by a number of drains and channels in Blackburn North, Blackburn South and Forest Hill. The creek then flows southwest, exiting the Municipality through Burwood into the City of Monash at Ashwood.

Dandenong Creek rises in the foothills of the Dandenong Ranges in the Shire of the Yarra Ranges, flowing through the City of Whitehorse before forming the south-eastern boundary of the City of Whitehorse at the Winton Wetland on the northern side of Boronia Rd. Dandenong Creek flows south at this point, passing under the Burwood Hwy at Vermont South and flows into the City of Monash.

Koonung Creek rises in Nunawading and forms the northern boundary of the majority of the City of Whitehorse. The creek flows west, straddling the northern boundary of Box Hill North and leaving the Municipality at its north-western tip before joining up with the Yarra River in the City of Manningham.

Most of the City of Whitehorse is fully developed and is now undergoing a phase of redevelopment, with increases in population density and intensification of land use, particularly along the main transport routes. As a result, the potential for increased flood risk and potential danger has increased and needs to be managed in a proactive manner. The key flood risks are likely to be associated with relatively short and intense rainfall events of a few hours’ duration, but extended long-term rainfall over several days will also create risks and social disruption.

The Bureau of Meteorology is responsible for providing a flood and storm warning service for heavy rainfall in Victoria in cooperation with other government, water and emergency management agencies. For metropolitan Melbourne, Melbourne Water owns and operates the flood warning system and provides warnings for the Bureau to disseminate.

The City of Whitehorse Flood and Storm Plan is developed by the City of Whitehorse Municipal Emergency Management Planning Committee led by Victorian State Emergency Service.

Vegetation

The City of Whitehorse has an abundance of parks, gardens and natural bushland reserves boasting many indigenous plant species.

Trees are an integral aspect of the urban character of Whitehorse. The municipality is dominated by an upper tree canopy which covers 26.6% of the municipality, with an additional 21.5% covered by other vegetation ranging from the exotic tree lined streets of Mont Albert to the native trees which dominate areas of Blackburn, Blackburn North, Vermont and Mitcham.

Parts of the City retain a bushland appearance uncommon in the metropolitan area. Significant areas of remnant vegetation can be found at Bellbird Dell, Cootamundra Walk, Wandinong Sanctuary, Wurundjeri Walk, Yarran Dheran, Antonio Park and the Blackburn Lake bushland reserves. In these areas, the tree canopy cover is extensive and large mature trees dominate. The bushland reserves are managed by Council to minimise the risk of bush fires.

Whitehorse also has its fair share of weed species that can cause issues if they are not managed.

Wildlife

The native wildlife of Whitehorse ranges from insects, bats, frogs and snakes to birds and mammals such as possums and kangaroos.

There are also a number of pest animals that have made a home in Whitehorse including foxes, wasps, rats and mice, pest birds such as the noisy myna bird and carp in Blackburn Lake and Surrey Dive which sometimes also suffer from minor blue-green algae outbreaks. There can also be outbreaks of elm leaf beetle which can cause damage in the western heritage areas of the city.

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