Water Disturbance
The hydrology of the landscape influences and changes the physiochemical environment, which intern along with hydrology, determines the biotic communities that are found in the swamp.[1]
The Tootgarook Swamp is the most substantial control on surface and subsurface hydrology on the Nepean Peninsula. It has a total catchment capacity of almost 3 million cubic metres at its maximum peak[2], therefore showing its immense value for flood protection and potential recharge. The Tootgarook Swamp is in connection with the shallow, largely unconfined Quaternary aquifer.[3] Discontinuous clay and peat layers may provide very local confined areas. Evidence of a perched watertable or near surface impermeable stratum. There is some evidence of low permeability palaesol horizons in the sequence which may cause localised perched watertables or ground water confinement. This, no doubt, is partly due to the proximity of Selwyn Fault, and the presence of an impervious bed at shallow depth to hold the water. To the north-north-west, this impervious bed is tilted in that direction and deeper.[4] Groundwater may also be perched above near peat and clay beneath the swamp. These aquitards are leaky, though may confine water in the underlying Bridgewater Formation aquifer.
Surface Ground water elevations across the Tootgarook Swamp are mainly at or above the surface, these flows keep the soil wet and support the indigenous plants and animals that live there. The drying of a swamp can result in soil erosion, peat subsidisation, release of carbon dioxide, loss of plants and animals that need water, changes to the region’s hydrology and exposure of Coastal Acid Sulphate Soils to air. Any activity that threatens the water available for a swamp should be avoided, including:
When the swamp is infilled, the water that made it wet has to go somewhere. If it isn't seeping back into the foundations of the house built on the former wetland, the water likely is leaking into formerly dry homes of the next low lying property owners and other parcels of land,[5] Groundwater moves through the saturated zone both downward and upward. The downward flow occurs due to gravity and the upward flow occurs because fluids tend to flow towards areas of lower pressure.
Infilling or draining the swamp not only destroys the sensitive wetland ecology but also leave residents susceptible to the effects of climate change.
This infilling results in a reduction in water supply and water storage, the loss of floodplain land and floodplain protection[6] of the swamp and also decreases the amount of water that recharges into the groundwater table. The infilling will increase backwater build-up upon the culverts in Chinaman’s creek. Therefore reducing the ability to control flooding of contiguous areas and flood protection for Rosebud and urban land in the north.
Infilling will increase drainage runoff into the swamp from new developments and gardens, even if the storm water is contained on-site. Water drainage will seep into the swamp and will increase nutrient levels and possibly cause eutrophication. Any new access roads will also create water runoff into the wetland area which will be polluted from vehicle movements including oil particles. Overall the water pollution discharge and leaching of nutrients into the swamp will seriously threaten the sensitive balance of this natural environment, even on a small scale.
These land management practices may be regarded as water affecting activities under the Water Act of 1989 and require approval. Water extracting activities within the swamp are also regulated by the Australian Government's Water Act 2007.
[1] The hydrological Science Journal of the United States of America – 16th December 2011 - Wetland as a Natural Assets.
[2] Chinamans Creek – Rosebud West Flood mitigation and restoration strategy – N.M.Craigie & Associates.
[3] Melbourne Water
[4] Memoirs of the Geological Survey of Victoria – R.A. Keble 1950
[5] National Wildlife Foundation www.nwf.org/News-and-Magazines/National-Wildlife/News-and-Views/Archives/1998/Caution-Building-in-a-Wetland-Can-Be-Hazardous-to-Your-House.aspx
[6] Wetlands Alberta www.wetlandsalberta.ca/wetland-loss/
The Tootgarook Swamp is the most substantial control on surface and subsurface hydrology on the Nepean Peninsula. It has a total catchment capacity of almost 3 million cubic metres at its maximum peak[2], therefore showing its immense value for flood protection and potential recharge. The Tootgarook Swamp is in connection with the shallow, largely unconfined Quaternary aquifer.[3] Discontinuous clay and peat layers may provide very local confined areas. Evidence of a perched watertable or near surface impermeable stratum. There is some evidence of low permeability palaesol horizons in the sequence which may cause localised perched watertables or ground water confinement. This, no doubt, is partly due to the proximity of Selwyn Fault, and the presence of an impervious bed at shallow depth to hold the water. To the north-north-west, this impervious bed is tilted in that direction and deeper.[4] Groundwater may also be perched above near peat and clay beneath the swamp. These aquitards are leaky, though may confine water in the underlying Bridgewater Formation aquifer.
Surface Ground water elevations across the Tootgarook Swamp are mainly at or above the surface, these flows keep the soil wet and support the indigenous plants and animals that live there. The drying of a swamp can result in soil erosion, peat subsidisation, release of carbon dioxide, loss of plants and animals that need water, changes to the region’s hydrology and exposure of Coastal Acid Sulphate Soils to air. Any activity that threatens the water available for a swamp should be avoided, including:
- Direct extraction of water from a swamp (e.g. pumps, de-watering or adjacent bores).
- Changes to the lands original contours. (e.g. infilling, flattening, smoothing.)
- Drains that divert water away from a swamp.
- Dams that prevent water reaching a swamp.
- Plantations that significantly reduce water available for swamps.
- Chemical spraying or any action that may expose the hydrology to chemicals.
When the swamp is infilled, the water that made it wet has to go somewhere. If it isn't seeping back into the foundations of the house built on the former wetland, the water likely is leaking into formerly dry homes of the next low lying property owners and other parcels of land,[5] Groundwater moves through the saturated zone both downward and upward. The downward flow occurs due to gravity and the upward flow occurs because fluids tend to flow towards areas of lower pressure.
Infilling or draining the swamp not only destroys the sensitive wetland ecology but also leave residents susceptible to the effects of climate change.
This infilling results in a reduction in water supply and water storage, the loss of floodplain land and floodplain protection[6] of the swamp and also decreases the amount of water that recharges into the groundwater table. The infilling will increase backwater build-up upon the culverts in Chinaman’s creek. Therefore reducing the ability to control flooding of contiguous areas and flood protection for Rosebud and urban land in the north.
Infilling will increase drainage runoff into the swamp from new developments and gardens, even if the storm water is contained on-site. Water drainage will seep into the swamp and will increase nutrient levels and possibly cause eutrophication. Any new access roads will also create water runoff into the wetland area which will be polluted from vehicle movements including oil particles. Overall the water pollution discharge and leaching of nutrients into the swamp will seriously threaten the sensitive balance of this natural environment, even on a small scale.
These land management practices may be regarded as water affecting activities under the Water Act of 1989 and require approval. Water extracting activities within the swamp are also regulated by the Australian Government's Water Act 2007.
[1] The hydrological Science Journal of the United States of America – 16th December 2011 - Wetland as a Natural Assets.
[2] Chinamans Creek – Rosebud West Flood mitigation and restoration strategy – N.M.Craigie & Associates.
[3] Melbourne Water
[4] Memoirs of the Geological Survey of Victoria – R.A. Keble 1950
[5] National Wildlife Foundation www.nwf.org/News-and-Magazines/National-Wildlife/News-and-Views/Archives/1998/Caution-Building-in-a-Wetland-Can-Be-Hazardous-to-Your-House.aspx
[6] Wetlands Alberta www.wetlandsalberta.ca/wetland-loss/
