If you can't find answers to your questions below, contact Council's Help and Service Centre on 9777 1000.


more info small Why does flooding occur?

Flooding is a natural process. It happens periodically as a result of heavy rainfall in a catchment when the water level in a creek or river rises. Specifically, it occurs when the runoff generated from the storm exceeds the capacity of the drainage system. The effects of flooding in the Willoughby City LGA are magnified by the proximity of urban development to natural and modified creeks and channels. Floodwaters overflow the banks of creeks and channels inundating the floodplain which may include roads, residential, commercial and industrial properties.

more info small What are the consequences of flooding?

Flooding causes severe economic damage and emotional distress. Flooding in urban and rural NSW is estimated to cost our economy about $250 million each year, and the human impact is even greater.

Flooding can be dangerous to people and animals and cause damage to buildings, infrastructure and utilities. It may also cause the loss of valuable belongings and disruption of essential services. Some examples of the risks associated with flooding:

  • Fast moving waters may knock down a person
  • Only about 600mm of moving water can float and wash away of an average vehicle
  • Nearly 50% of deaths are caused by cars while people are trying to escape from a flood affected area

more info small What is flash flooding?

Flash flooding occurs following intense rainfall with resulting flood levels rising to their peak within a very short time, typically between 30 minutes and 2 hours. This tends to occur in steep urbanised catchments such as in the Willoughby City LGA and gives residents very little warning time and little time to prepare.

more info small What is a 1 in 100 year flood?

A 1 in 100 year flood (commonly known as a 100 year flood) is a large flood that has a 1% chance of occurring in any year. If an area has experienced a 1 in 100 year flood in a certain year, it does not mean that there is no chance of another 1 in 100 year flood occurring in the next 99 years. In fact, some parts of NSW have had more than one of these floods in a single decade.

more info small What is Probable Maximum Flood?

The Probable Maximum Flood (PMF) is the largest flood that could conceivably occur within a particular catchment, and is a very rare and unlikely event.

more info small What is Council doing to manage the flooding problem in Willoughby?

Willoughby City Council’s responsibility is to manage lands subject to flooding on two levels.

Firstly, in accordance with the NSW Government’s Flood Prone Land Policy, Council is responsible for formulating and implementing Floodplain Risk Management Plans. These plans involve catchment-wide studies that identify significant flooding issues and floodplain management studies that identify potential flood mitigation solutions and strategies. Flood mitigation options could typically involve floodplain modification, property modification and emergency response measures.

Secondly, Council has a responsibility to ensure future developments are compatible with flood hazards and do not create flooding problems in other areas. As such Council may enforce planning (development) controls such as minimum heights of floor levels above ground level and prohibiting specific land uses in areas prone to flooding. These controls are set out in Willoughby Council Development Control Plan pdf format Attachment 22 - Floodplain Management Technical Standard.

more info small How are floodplains managed in NSW?

In NSW, Local government has the primary responsibility for controlling the development of flood prone land, but the NSW Government, through the Department of Environment, Climate Change and Water (DECCW) and the State Emergency Service (SES), also has an important role to play in managing the flood risk across the State.

The NSW Government’s Flood Prone Land Policy is directed at providing solutions to existing flooding problems in developed areas and ensuring that future developments will not create flooding problems in other areas. The State Government subsidises flood mitigation works to alleviate existing problems and provides specialist technical advice to assist councils with their floodplain management responsibilities.

The NSW Government provides technical and financial support to local councils to develop Floodplain Risk Management Plans which consist of the following stages:

  1. Flood Study
  2. Floodplain Risk Management Study
  3. Floodplain Risk Management Plan
  4. Implementation of the Plan

Read more about these stages below.

more info small What is a Flood Study?

The first stage in the development of a Floodplain Risk Management Plan for a particular catchment involves a Flood Study, which is a comprehensive technical investigation of flood behaviour for that catchment. These Flood Studies show the distribution, extent, levels and velocity of floodwaters across sections of the floodplain for different flood events including the 1 in 100 Year Flood and Probable Maximum Flood.

more info small What is a Floodplain Risk Management Study?

Following a Flood Study, the next stage in the floodplain risk management process is a Floodplain Risk Management Study. The purpose of the study is to identify, assess and compare various risk management options and consider opportunities for environmental enhancements as part of mitigation works. The management study draws together the results of the flood study and data collection exercises. It provides information and tools to allow strategic assessment of the impacts of management options for existing, future and continuing flood risk on flood behaviour and hazard and includes the social, economic, ecological and cultural issues in addition to an assessment of costs and benefits of all options. The study also considers and determines suitable Flood Planning Levels and planning controls to guide future development.

Undertaking a Floodplain Risk Management Study is a very long and involved process.

more info small What is a Floodplain Risk Management Plan?

A Floodplain Risk Management Plan formalises and prioritises mitigation works and other floodplain management measures that are recommended in the Floodplain Risk Management Study. The Plan is formally adopted and implemented by Council.

more info small What is the current status of Floodplain Risk Management Plans in Willoughby?

Flood Study Status:

Flood Studies have been completed for the following catchments:

  • Flat Rock Creek (Mainstream flooding only)
  • Sailors Bay Creek
  • Scott’s Creek (Mainstream flooding only)
  • Sugarloaf Creek
  • Swaines Creek

The Blue Gum Creek draft flood study is currently being reviewed by Council prior to public exhibition.

Floodplain Risk Management Study and Plan Status:

Floodplain Risk Management Studies have been completed for the following catchments:

  • Sugarloaf Creek

In addition to the above detailed studies, Willoughby City Council engaged with consultants to undertake an Overland Flooding Investigation for its Local Government Area. The investigation provides preliminary information on flooding in areas that have been identified as being at risk of flooding.

Council is currently in the process of reviewing the Overland Flooding Investigation map. To see if your property is in an area subject to flood related planning controls, contact Council's Help and Service Centre on 9777 1000.

more info small Scientists are warning of rising temperature and less volume and frequency of rain. Why are we going to experience flooding if there is less rainfall?

Climatologists have suggested for some time that climate change would lead to more intense rainfall globally. They suggest that while frequency of smaller rainfall events may decrease and we may experience drought conditions, more extreme events such as a 1 in 10 year event and larger may occur more often. This will result in more flooding events globally.

more info small How can I find out if my property is subject to flood related planning controls?

Council is currently in the process of reviewing the Overland Flooding Investigation map. To see if your property is in an area subject to flood related planning controls, contact Council's Help and Service Centre on 9777 1000.

more info small What is the purpose of the flooding investigation and the resulting planning controls?

The flooding investigation and new planning controls (Technical standard 3- Nov 2009 ) guide development of land in areas subject to flooding in the Willoughby City Local Government Area (LGA), pending the completion of Floodplain Risk Management Studies for each of the catchments comprising the overall drainage system.

The broad objectives of the new planning controls are to:

  • Provide controls for the assessment of applications on land in flood prone areas.
  • Alert the community to the potential hazards and extent of land affected by flooding.
  • Inform the community of Council’s policy in relation to the use and development of land in flood prone areas in the Willoughby City LGA.
  • Reduce the risk to human life and damage to property caused by flooding through controlling development in flood prone areas.

more info small What are the different types of flooding?

The flooding investigation and the resulting planning controls (Technical standard 3- Nov 2009) look at the two types of flooding which result in inundation of property in flood prone areas of the Willoughby City LGA – Main Stream Flooding and Local Overland Flooding. (See definitions below.)

more info small What is Main Stream Flooding?

Main stream flooding is the flooding of normally dry land which occurs when water overflows the natural or artificial banks of a stream, river, estuary, lake or dam.

more info small What is Local Overland Flooding?

Local Overland Flooding results from runoff which travels as sheet flow over grassed and paved surfaces.

The Overland Flooding Investigation caters for two levels of Local Overland Flooding, Local Drainage and Major Drainage, which are distinguished by the depths of flooding and the potential danger to personal safety and damage to property.

At the lower end of the scale, Local Drainage problems may involve shallow depths of overland flooding (up to 300 mm deep) with generally little danger to personal safety. Problems could typically arise because of deficiencies in building practice where floor levels are too close to finished ground levels.

At the upper end of the scale, Local Overland Flooding may involve the flow paths of original drainage lines, whether natural or altered by urban development, and may be categorised as Major Drainage. Depths of flooding are generally in excess of 300 mm and conditions may result in danger to personal safety and damage to property (premises and vehicles).


more info small My property is highlighted pink/red/blue on the map. What does this mean and what controls apply to it?

  • If your property is highlighted pink, it is subject to Local Overland Flooding - Local Drainage planning controls
  • If your property is highlighted blue, it is subject to Local Overland Flooding - Major Drainage planning controls
  • If your property is highlighted red, it is subject to mainstream flood planning controls

For more information refer to the definitions above and the following: pdf format Attachment 22 - Floodplain Management Technical Standard.

more info small Will the new planning controls affect my property?

The new planning controls apply to land which is affected by local overland flooding or mainstream flooding in their respective catchments.

You can request flood information specific to your property from Council. This will be provided as a Section 149 certificate.

more info small What are the implications of my property being identified as flood prone (ie a flood control lot) if I want to carry out development on my site?

If your land is identified as being subject to flooding, you are not permitted to undertake development specified in the General Housing Code provisions of State Environmental Planning Policy (Exempt and Complying Development Codes) 2008 as Complying Development (ie by the issue of a Complying Development Certificate). Any such development specified therein would require the submission of a Development Application to Council for approval.

more info small Will the value of my property be altered if I am flood affected?

If your property is now deemed to be subject to Main Stream or Local Overland Flood related planning controls the real flood risks on your property have not changed, only Council’s classification has been altered. A prospective buyer of your property could have previously discovered this flood risk if they had made the appropriate enquiries.

more info small Will I be able to get house and contents insurance if I am flood affected?

Flood cover, as part of some home and contents insurance policies, has recently been made available in NSW by some insurers. Premiums for flood cover will vary and are typically based on the assessed flood risk for individual properties which are determined by the insurer. In general, flood cover is available for properties subject to low flood risk at minimal cost. Properties with a higher flood risk may be charged a premium to reflect the likelihood and seriousness of impacts of a flood on that property.

However, it should be noted that flood cover has traditionally not been available as part of standard home and contents insurance, or has been subject to strict conditions either limiting the source of flooding or capping coverage, or both. Contact your insurer to check if your insurance policy needs to be updated. You should confirm the availability of flood cover, and any relevant conditions and costs that might apply with your insurer.  

more info small What can I do to be flood prepared?

Visit the NSW State Emergency Service website at www.ses.nsw.gov.au for further information regarding flood preparation measures, in particular the NSW Flood Safe Guide.

more info small What can I do to minimise flooding?

Flooding is a significant issue which affects the entire community, and actions by individuals may have serious consequences on others within the catchment. To play your part:

  • be aware if your property is affected by flooding or contains a potential overflow path;
  • be aware of what drainage easement affects your property;
  • be conscious of flow paths around your dwelling and keep them clear - be careful not to dispose of grass clippings and other garden cuttings in or near the watercourse and remove any obstructions that may cause blockages;
  • new fences for properties subject to flood related planning controls need to comply with Council requirements in Technical standard 3- Nov 2009
  • do not construct raised gardens or plant significant trees or vegetation within flow paths - Certain species such as Jacaranda, Poplar, Willow, Fig, Camphor Laurel, rubber Trees and other types with aggressive root systems can cause pipelines to become blocked or cracked;
  • do not perform any significant work (earthworks, creek bank protection, bridges, piping etc) to the watercourse through your property without first consulting Council;
  • do not lay any pipes, construct a bridge or divert a watercourse without first consulting Council - unapproved work can increase flooding for both you and your neighbours; and
  • do not fill in low lying areas of your yard without seeking Council approval may cause water to pond and increase flooding potential on both your property and your neighbour’s.

With your help, we can minimise flood risks and damages.

more info small Who can I contact for more information?

Contact Council’s Help and Service Centre on (02) 9777 1000.