Why is the Flood Study being updated and what’s changed?

The main purpose of a flood study is to describe flood behaviour and identify areas that are flood prone. We use computer flood models to estimate where it might flood, and by how much. From time to time, the models are updated and predicted flood levels may change. For the Hewitts Creek Flood Study, we’ve considered Council's revised Blockage Policy, which helps us work out how blocked stormwater structures might affect flooding. We have improved information, such as recent data from land surveying. We've included an extended network of drainage pits and pipes and used more improved and detailed modelling techniques. 

The updated Blockage Policy generally gives us lower flood levels upstream of main culverts. A culvert is a tunnel or drain structure built under a road or railway to allow water to flow underneath. The maps in the report show what the flood levels are in different areas in the catchment. You can view the report in the Document Library, at the drop-in information session or at Thirroul Library.

What about historical floods?

The Hewitts Creek catchment has experienced several significant floods over the past decades, the most recent in 1998 which resulted in extensive damage to both public and private property. The 1998 flood in this area generally equated to a 1% Annual Exceedance Probability (AEP) flood, meaning that there is a 1% chance of a flood of this size or larger occurring at a particular location in any given year.  We also know that larger floods can potentially occur in the future and affect additional areas that may not have experienced flooding in the past. 

Do the maps in the draft report show the flood levels for my property?

There are hundreds of properties in this catchment. The scale of these maps makes it hard to find individual properties and see what the estimated flood levels might be. Sometimes you can get a better look by opening the maps on a computer and zooming in to the area where your property is, however you’re just looking at the estimated levels for broad areas of the catchment rather than specific levels for individual properties. The report is also a draft, which means some information may be updated before the Study is finalised.

Where can I get information about flood levels on my property?

Council has historical flood level records and/or our completed flood studies for some properties, but not all. Please contact our Customer Service team on (02) 4227 7111 to find out what’s available for your property.

What happens next?

After we’ve completed the flood study, we’ll review the Floodplain Risk Management Study to look at what the risks/damages from floods might be and what we could do to mitigate (reduce) those risks. Next, we’ll review the Floodplain Risk Management Plan, to give us a prioritised plan of flood mitigation measures proposed for the catchment. Then we’ll roll out the Plan! Every 5-10 years, we go back to the beginning of this process and start with a review of the flood study to consider new survey data, policy changes, recent major flood events and changes in the catchment such as flood mitigation works or new development.

What flood mitigation work is Council doing in this catchment?

We’ve purchased two houses that were identified in the Hewitts Creek Floodplain Risk Management Study and Plan for Voluntary Purchase, as they were at high risk of serious flooding and not safe to live in. Houses we buy as part of the Voluntary Purchase Scheme are knocked down and the land is turned into parks and open space. We’ve done weed control, work to maintain creek banks and planting at various locations along Council-owned portions of creeks throughout the catchment. We’ve also carried out various flood mitigation works including modifications to the detention basin at Black Diamond Place (Bulli), provision of an overland flow path at The Esplanade (Thirroul), and a range of improvements to the existing culvert at Lachlan Street (Thirroul).

How does Council manage flood risk?

Each year, Council spends millions of dollars on stormwater and floodplain management. Our team of flood experts prepare flood studies and floodplain risk management studies that help us understand the flood behaviour for a particular catchment and see if there are any ways of reducing flooding risk in an area.

Floodplain risk management studies include a plan of potential solutions aimed at reducing the existing and future flood risk. Examples of these solutions include:

  • Emergency response plans based on detailed understanding of flood behaviour
  • Building new structures that collect and carry stormwater into drains or creeks, such as detention basins and swales, or improving existing ones to better manage stormwater and floods
  • Land zoning that says what can and can’t be built on flood-prone land
  • Voluntary purchase of houses built in high flood risk areas

Why doesn’t Council clear out creeks?

Council is responsible for maintaining watercourses (e.g. creeks, overflow paths or drainpipes) on Council-owned land and has a maintenance program for this. Most watercourses in our city are on private property and their maintenance is the responsibility of the land owner. In these cases, Council is unable to perform any work on the watercourse. If you need advice on maintaining watercourses, please contact our Customer Service team on (02) 4227 7111.

What is a catchment?

An area where water is collected by the natural landscape, usually surrounded by mountains or hills. In a catchment, rainwater run-off eventually flows to a creek, river, dam, lake or ocean.

How will my feedback be used?

At the end of the engagement period, all feedback is read and considered. A report will be produced and provided to Councillors, and they will consider whether to adopt the Flood Study.

How can I join the conversation?

Write  Locked Bag 8821, Wollongong DC 2500

Email engagement@wollongong.nsw.gov.au

Phone (02) 4227 7111

Drop-in Information Session:
When: Wednesday 18 September 4pm - 6pm
Where: Bulli Senior Citizens Centre, 8 Hospital Rd, Bulli

You can also submit feedback via the online form.