Moonee Ponds Creek flows within or along the boundary of the park for 8 km of its length, entering near the Somerton Road car park and effectively enclosing the western part of the park. The creek appears on an 1847 survey map of the area as "Moonee Moonee Chain of Ponds". This should not be taken as a description of the creek in this area, as the lower reaches of the creek would have bestowed the name. There is no historical description that can be definitely connected to this part of the creek - Governor Burke's 1837 comments about frequent water holes, as quoted in Gross, are not specific as to location, although I have not seen Gross's source.
Perhaps some idea of the original shape of the creek can be formed by looking at the billabong south of the quarries, which does indeed consist of several ponds with vegetated ground in between them. The map mentioned above shows one unlabelled blob on the creek within the park which might be a larger water hole - a similar blob on the map upstream of the park is labelled "water hole" in the surveyors field book, page 94.
The bed of the creek for most of its length was probably soil or sediment deposited by the creek itself in an earlier era, and stabilized by vegetation and dead wood. In a number of places the banks are now vertical walls of sediment up to 3 or 4 metres high (and even higher on private land upstream of the park). The banks have obviously eroded and continue to do so, and the bed has certainly eroded as well by varying amounts, with loose sand deposited in other places. Some old trees still growing in the bed show an original soil level well below the top of the banks, and may indicate where pools existed.
Degradation of the creek would have started soon after sheep were brought to the district. With their hard hooves they compacted the soil of the catchment area, causing rainfall to run off rapidly into the creek rather than soak into the soil. The higher peak flows that resulted, together with destruction of stream-side vegetation by sheep, would have caused erosion. Flows would have been further increased by overgrazing and by clearing of trees from the catchment.
Conversion from a chain of ponds into a deep, steep sided channel affects not only plants and animals that live in and around the ponds but also the habitat value of the whole floodplain, by lowering the water table. This is shown diagrammatically in Hazell (2003), page 307. The diagram also shows a "stranded pond": applying the term "billabong" to such a pond (like the ones in the park) is incorrect, since a billabong (or oxbow lake) is the former path of a channelized stream.
The creek channel will not get much deeper overall because it has reached bedrock in a number of places. All three local rock types can be seen in the bed of the creek - mudstone at the eastern end of the picnic ground, granodiorite north of the homestead driveway and basalt downstream of this.
However the vertical banks that have been created by erosion are not stable and they continue to erode. In a number of places (usually on the outside of bends) attempts have been made to prevent this by by piling large pieces of quarried granite against the bank. This has often been successful, but will never look natural. Most of it may have been done before the formation of the park, although the restoration plan refers to a site which was "treated with graded rock material in the late 1980s". In a few places waste material including asphalt has been used. In a couple of places rocks have also been placed across the path of the creek.
An alternative method of stabilizing the banks is to grade them back to a stable slope and revegetate. This has been done in a couple of places, including just south of the homestead driveway, but is only suitable where there are no trees and fast-flowing water does not impact the bank.
The restoration plan contains a short chapter about the creek, and includes design recommendations for rock fill to protect banks. Protection of banks should not be confused with "restoration" of the creek - it is just designed to protect old trees and maintain the current form of the creek, which is unnatural. Complete restoration of the creek would first require restoration of the catchment and upstream sections of creek, or construction of some sort of retarding basin and sediment trap upstream.
The restoration plan also proposes "construction of a series of small rock chutes along the bed of the channel. These prevent further deepening, inhibit erosion of the toe zones of channel banks, and encourage deposition of materials against the toes of banks and subsequent vegetation colonisation of these sites." Again this is not claimed to be restoration, but is designed to make the creek look more natural. It is obviously not relevant where the creek has already reached bedrock.
The management plan (page 7) contains the following:
Restoration of the creek will need to accommodate the modified flows, high sediment load and reduced water quality that is likely to continue to characterise the creek.and
Prepare a Creek Management Plan to stabilise the banks of the Moonee Ponds Creek, Greenvale Creek and other major drainage lines in the Park. Control bank erosion through subtle engineering works designed to control stream flow rates, where possible creating a series of small rock-walled weirs designed to recreate the original "pond" character of the creek.
There is no creek management plan and there would not be much point in having one since Parks Victoria would never have any money to implement it. Any future stabilization or restoration of the creek will have to be done by Melbourne Water, who are responsible for all waterways flowing into Port Phillip Bay. In the absence of this the banks will continue to erode until the creek attains a form which is stable with the current flow regime, which means it will be considerably wider and more sinuous than it is now.