11 February 2011
Drainage System Recovers from Record Deluge
Melbourne Water’s drainage system is recovering from one of its biggest tests on record, with figures showing some parts of the network experienced a 1-in-500 year rainfall intensity on 4–5 February 2011.
Melbourne Water manages a network of 1,400 kilometres of stormwater drains and over 350 retarding basins and wetlands, as well as the 8,400 kilometres of rivers and creeks that ultimately receive the stormwater and take it out to the bay. This is in addition to about 25,000 kilometres of drains managed by local councils.
General Manager of Asset Planning, Paul Pretto, said Melbourne Water’s system had coped well with the millions of litres dumped on the city in a matter of hours.
“Many of our flood-monitoring rain gauges recorded at least double their February average within a 24-hour period, and most of it came in just two-to-four hours.” said Dr Pretto.
“Melbourne’s capacity to deal with flash floods comes not just from concrete stormwater drains but also the open space around suburban waterways and sportsgrounds, which are designed to fill with water running off our streets and protect the city.
“People may have noticed their local park, sports field or riverside path was completely flooded, which is exactly what they’re supposed to do under those circumstances.
“There are over 200 Melbourne Water retarding basins around the city with many of them doubling as sportsfields, designed to hold onto floodwater and release it slowly into the drainage system to minimise flooding.”
Dr Pretto said local council and Melbourne Water drainage systems were designed to national standards but that no urban drainage system in the world could have reasonably swallowed the intense rainfall that Melbourne experienced on 4–5 February.
“While the system performed well the sheer intensity of this event meant that not everyone got through unscathed. We’re very conscious that a lot of property has been affected and we’ll be working with councils to see what improvements can be made,” added Dr Pretto.
“This is doubly important because science suggests that in future we can expect more intense storms but less rain overall. We need to look at more innovative ways to protect from flooding but also harvest stormwater as a resource.”
Melbourne Water invests $17 million a year in maintaining its drainage system and commits about $50 million to expanding and upgrading the system. This is over and above investments in drainage made by local councils.
Media Contact: Andrew McGinnes (03) 9235 7277; 0403 930 846
Rainfall Data – 4 to 5 February 2011
In the 24 hours from 9am on 4 February to 9am on 5 February 2011, metro Melbourne experienced intense storms. Rainfall was highest in the eastern and south-eastern suburbs, with some isolated parts of the system seeing rainfall intensity consistent with a 1-in-500 year storm. Other parts were lower than this (around 1-in-20 years) but the February rainfall averages for virtually all areas were exceeded with a few hours.
Melbourne Water collects rainfall data from about 150 stations across Melbourne as part of its role as a flood manager.
Inner eastern suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Burwood East | 106mm | 60mm |
| Kew | 99mm | 48mm |
| Ashwood | 131mm | 54mm |
| Burnley | 116mm | 46mm |
| Blackburn | 103mm | 49mm |
Inner western suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Altona | 138mm | 42mm |
| Brooklyn | 86mm | 49mm |
| Footscray | 49mm | 45mm |
| Sunshine | 47mm | 47mm |
| Maribyrnong | 61mm | 44mm |
| Spotswood | 88mm | 47mm |
| Deer Park | 47mm | 48mm |
| Keilor | 59mm | 44mm |
| St Albans | 52mm | 49mm |
| Flemington | 65mm | 39mm |
Inner northern suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Coburg | 68mm | 49mm |
| Fairfield | 86mm | 42mm |
| Fawkner | 69mm | 47mm |
North-eastern suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Doncaster | 104mm | 48mm |
| Heidelberg | 84mm | 43mm |
| Lower Plenty | 99mm | 43mm |
| Mernda | 72mm | 39mm |
| Kinglake | 77mm | 74mm |
| Greensborough | 126mm | 41mm |
| Ivanhoe | 77mm | 52mm |
Outer eastern suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Beenak | 145mm | 55mm |
| Knox | 111mm | 47mm |
| Lilydale | 117mm | 47mm |
| Maroondah Reservoir | 65mm | 60mm |
| Mount Evelyn | 124mm | 58mm |
| Mount Dandenong | 103mm | 62mm |
| Montrose | 104mm | 52mm |
| Lysterfield | 161mm | NA |
| Ringwood | 112mm | 46mm |
Outer northern suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Bundoora | 89mm | 44mm |
| Craigieburn | 69mm | 42mm |
| Darraweit Guim | 86mm | 38mm |
| Konagaderra | 60mm | 40mm |
| Epping | 98mm | 44mm |
| Fawkner | 69mm | 47mm |
| Jacana | 64mm | 40mm |
| Somerton | 81mm | 50mm |
| Wallan | 72mm | 41mm |
Outer western suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Hoppers Crossing | 112mm | 42mm |
| Rockbank | 61mm | 45mm |
| Diggers Rest | 67mm | 49mm |
| Bulla | 54mm | 42mm |
| Sunbury | 57mm | 44mm |
| Romsey | 64mm | 40mm |
| Mt Macedon | 98mm | 55mm |
South-eastern suburbs - Rainfall figures
| Suburb | February 5 2011 rainfall | Average rainfall for February |
|---|---|---|
| Berwick | 168mm | 46mm |
| Caulfield North | 140mm | 57mm |
| Cranbourne | 61mm | 55mm |
| Elsternwick | 141mm | 47mm |
| Frankston North | 59mm | 41mm |
| Hampton Park | 159mm | 43mm |
| Mentone | 149mm | 52mm |
| Oakleigh South | 137mm | 48mm |
| Officer | 195mm | 52mm |
| Rowville | 147mm | 46mm |
| Sandringham | 140mm | 48mm |
| Springvale West | 144mm | 50mm |