Community warnings during floods
Victoria State Emergency Service (SES) is the control agency for flood, storm, tsunami and earthquake in Victoria, and is the responsible Authority for issuing emergency information and warnings to communities. For more information visit the VicEmergency website emergency.vic.gov.au
Detailed information regarding regarding flood warnings notifications issued can be found on SES Floodsafe website http://www.ses.vic.gov.au/get-ready/floodsafe
Southern Rural Water has approval from the SES to provide updates about releases from its storages and the SES is the responsible agency for issuing community warnings.
High flow figures from SRW storages
When website and social media updates will start
High flow release figures from our storages will be available when:
- releases climb above 3,500 ML/day at Lake Glenmaggie
- Thomson River up stream of Cowwarr Weir climbs above 3,500 ML/day
- releases climb above 6,000 ML/day for Lake Narracan and Blue Rock Lake.
On Facebook, if you turn on your notifications for Southern Rural Water you will never miss one of our updates. To do this follow the instructions on this Youtube clip https://www.youtube.com/watch?v=Raw-c62HfE0
Lake Glenmaggie – No Current High Flows
Calculated inflows into Lake Glenmaggie: XX ML/day (falling)
Total capacity: 177,640 ML
Current storage level: XX ML (falling)
Total releases: XX ML/day (falling)
Notes: This will be our last update unless conditions change.
For more information on Macalister River flood warnings visit the Bureau of Meteorology website. Minor Flood Warning: 7,500ML Moderate Flood Warning: 22,000ML Major Flood Warning: 35,000ML
Cowwarr Weir – No Current High Flows
Thomson River at Coopers Creek
Megalitres per day:
Thomson River Upstream of Cowwarr Weir
Megalitres per day:
When flow reaches 8,000 ML/per day upstream of Cowwarr Weir and is expected to rise, access to the low level bridge at Cowwarr Weir cannot be guaranteed.
Please visit the Bureau of Meteorology website for current flood warnings downstream on the Thomson River.
Blue Rock Lake – No Current High Flows
Total Capacity : 208,000ML
Current storage level:
Calculated inflows into Blue Rock Lake:
Total releases – at this time on the Tanjil River down stream of Blue Rock Lake:
For more information on the Latrobe River flood warnings visit the Bureau of Meteorology website.
Official Flood Warnings – Tanjil River at Tanjil South
Minor Flood Warning: 7,500
Moderate Flood Warning: 11,700ML
Major Flood Warning: 18,500ML
Lake Narracan – No Current High Flows
Total capacity: 7,230 ML
Current storage volume:
Calculated Latrobe River flows at Thoms Bridge:
Calculated inflows into Lake Narracan:
Total outflows- at this time on the Latrobe River down stream of Lake Narracan:
Notes: For more information on the Latrobe River flood warnings visit the Bureau of Meteorology website.
Official Flood Warnings on the Latrobe River at Thoms Bridge
Minor Flood Warning: 8,500ML Moderate Flood Warning: 11,900ML Major Flood Warning:
What is a One in 100 Year Flood?
A one in 100-year flood is a flood that has a 1 in 100 or 1% chance of occurring in each and every year.
In a 70 year lifetime there is a 50/50 chance of a 1 in 100 flood being exceeded at any location.
Can You Have Two 100-year Floods in One Year?
Yes, two 100-year floods can occur one after the other.
Who is in Charge of Responding to the Floods?
The Victoria State Emergency Service (VICSES) is the control agency for flood response works in partnership with support agencies such as DEPI to manage responses to flooding.
How does Victoria’s Flood Warning System Work?
Flood warning information is acquired through the Victorian streamflow gauging network.
The network has 750 gauging sites that serve a range of purposes, including 283 that are used as primary flood warnings sites.
Other sites are used to provide further back up information and flash flooding information. Data collected is immediately made available to those organisations that require it.
Who Develops Flood Maps?
Melbourne Water and Catchment Management Authorities develop flood maps for areas at risk.
These maps are used for both land planning and by the SES to provide flood information during flood emergencies.
Flood maps have been completed across the state for the 1 in 100-year flood. In a number of key areas across the state, this is supplemented by additional information on flood extent and height for a range of flood sizes.
What is a Levee?
A levee is a natural or man-made mound or wall to confine floodwaters.
Levees can reduce the risk of flooding for adjacent properties, but no levee can eliminate all flood risk.
Levees can also increase the risk of flooding downstream through the loss of natural floodplain storage or increase flooding to unprotected area.
Who is Responsible for Maintaining Levees?
- Private landowners are responsible for maintaining levees on their land. They may be required to obtain a planning permit to undertake works from their local Council.
- Local councils and/or Melbourne Water are responsible for maintaining levees which protect urban communities.
- There are a smaller number of levees on public land built many decades ago which have no clear ownership responsibility.
Why Don’t Water Corporations Hold Back More Water During Flooding Events to Protect Downstream Communities?
Most water corporation dams were built to capture sufficient water to meet the supply needs of the community.
They have very little additional capacity to mitigate the impacts of flood events on developments located on flood plains.
In extreme floods, dams simply cannot hold back the massive volumes of water that flow into a reservoir over a short period of time. Dams must spill water once the capacity of the reservoir is reached and allow the water to continue its passage through the water courses and across the floodplains.
Dam spillways are designed, however, to allow extreme floods to pass through the reservoir without compromising the dam structure itself, thereby reducing the impact on downstream communities.
Who is Responsible for Dam Safety?
Under Victorian legislation dam operators and owners are responsible for dam safety.
The Minister for Water maintains sufficient oversight of dam safety to ensure responsibilities are being met and to intervene where required.
What Would Cause a Dam to Fail?
Dams can fail if water flows over the dam wall during high rainfall or floods.
This is because the capacity of the spillway is not able to pass the flows safely.
Also, where construction and materials are inadequate, dams can fail due to piping and erosion and subsequent water flow through the embankment or foundation of the dam.
Does Vegetation in and Around Streams Have an Impact on Flooding?
In major floods, such as January 2011 , flood height is controlled primarily by the intensity and amount of rainfall, not vegetation.
Vegetation along riverbanks can have a beneficial effect on flooding in lowland areas as it slows the rate of water movement.
However, in large floods, the main control on local flood level will be through constrictions that choke the flow down. These are usually road embankments, or bridge openings. Such constrictions are much more important than the local effect of vegetation.
How safe is floodwater?
Floodwater can contain contaminants like animal waste, agricultural chemicals and petrol. Avoid swimming in floodwaters, swollen creeks, rivers and other tributaries at all times.
If you are unsure whether it is safe to swim in a river that has been affected by floodwaters, seek advice from the local council.
Is My Water OK to Drink?
Floodwater can contain contaminants like animal waste, agricultural chemicals and petrol.
For those members of the community who are on a town supply of drinking water, the relevant water corporation will advise its customers if the tap water is unsafe to drink, use for cooking, cleaning or bathing via local media and their websites.
For those members of the community on private water supplies (tanks, bore water), advice on managing these supplies post flood is contained in the Department of Health’s flood recovery packs which are available at relief and recovery centres and on the DHS website.
What About Water for Stock?
Floodwater can contain contaminants like animal waste, agricultural chemicals and petrol and may be dangerous to stock.
Advice on managing these supplies post flood is contained in the Department of Health’s flood recovery packs which are available at relief and recovery centres and on the DHS website.
Flood history at Glenmaggie
Flood history at Glenmaggie
Below shows a comparison of flows into Glenmaggie and flows out of Glenmaggie for the ten highest floods on record.
Glenmaggie – ten largest floods (ranked on outflows)
Peak inflow – 250,000 to 300,000
Peak outflow – 147,600
Peak inflow – 123,000
Peak outflow – 110,600
Peak inflow –102,000
Peak outflow – 88,900
Peak inflow –108,000
Peak outflow – 88,100
Peak inflow – 83,200
Peak outflow – 77,000
Peak inflow – 69,700
Peak outflow – 75,500
Peak inflow – 62,600
Peak outflow – 66,500
Peak inflow – 91,000
Peak outflow – 62,400
Peak inflow – 69,000
Peak outflow – 59,000
Peak inflow – 93,700
Peak outflow – 58,000