What is the Marrickville Development Control Plan 2011 (MDCP 2011)?

The MDCP 2011 provides detailed planning and design guidelines to support the planning controls in the Marrickville Local Environmental Plan. It identifies additional development controls and standards for addressing development issues – in this case flooding. 

What is a flood study?

A flood study is a comprehensive investigation of flood behaviour within a catchment. It provides detailed information about the nature of flood risk including the distribution, extent, depths, levels and velocity of floodwaters for a range of storm events, including a 100 year flood.

What is a 100 year flood event?

A 100 year flood event is a flood that is predicted to occur on average once every 100 years. There is a 1% probability of it occurring in any given year. However, if an area has had a 100 year flood, it doesn’t mean that it would be another 99 years before the next one happens. For example, the last time the Brisbane River flooded before the 2011 disaster was in 1974. These were both 100 year events. 

A 100 year flood is also expressed as a 1% AEP flood event. This is the Annual Exceedance Probability (AEP) and is the chance of a storm of a given intensity and duration happening at least once in any year.

The 100 year flood, or 1% AEP, is used as the standard for identifying flood affected properties and determining residential development controls.

Why did Council undertake this flood study?

Under the NSW Government’s Flood Prone Land Policy, Councils are responsible for managing flood affected areas to help reduce the risk to people and property. Flooding costs owners, residents and local government a lot of money. People affected by floods can also suffer significant distress and hardship.

The flood study is the first stage of an overall floodplain management plan for the catchment. The plan will identify ways of managing flood risk which may include:

  • controls on development
  • helping people at risk (e.g. flood warning systems) and
  • changing behaviour of the flood itself (e.g. upgrade of stormwater systems)

How has Council determined if a property is flood affected?

Properties flooded in a 1% AEP storm event, where more than 10% of the property area is inundated and the flood depth is greater than 0.15 metres, are initially identified as being flood affected.

Each property is then reviewed to determine if it is either:

  • Exposed to water depths generally in excess of 0.3 metres in or adjacent to the property, as this may be dangerous, cause property damage or both; and/or
  • Located in the floodplain of an original watercourse (which may now be piped, channelised or diverted), or sloping areas where overland flows develop along alternative paths once the capacity of the stormwater system is exceeded; and/or
  • Located in a major overland flow path through developed areas outside of defined drainage reserves.

This process ensures that only those properties which are subjected to a genuine flood risk are identified.

Can a flood affected property be developed?

Properties affected by flooding can, in most instances, be developed providing acceptable risk management criteria are demonstrated and applied. The planning controls applicable under Marrickville Local Environmental Plan 2011 and Marrickville Development Control Plan 2011 to a flood affected property are specific to the proposed land use, the floodplain and the extent of flooding on your property. You will need to obtain and use this information when preparing a development application for your property.

Will the value of my property be affected if it has been identified as flood affected?

Prospective buyers are able to find out if a property is flood affected because Council has a duty to disclose this information.  The information is made available on Section 149 Planning Certificates. If you are concerned that the flood classification may affect the value of your property you should seek valuation advice.