How does Council know what works will help reduce the impacts of flooding?

Each year, Council spends millions of dollars on stormwater and floodplain management. Council’s team of flood experts prepare flood studies and floodplain risk management studies that help us understand the flood behaviour for a particular catchment (an area which leads to a river or creek) 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: 

  • building swales or detention basins that collect and carry stormwater into drains or creeks
  • making changes to culverts to so that water will flow through them easier
  • 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

What did the Collins Creek catchment flood study find?

We completed a Flood Study and Floodplain Risk Management Study and Plan for the combined catchments of Whartons, Collins and Farrahars Creeks, Bellambi Gully and Bellambi Lake. These catchments have experienced a number of significant floods in recent decades including those in August 1998, March 2014, August 2015 and June 2016. 

One of the flood problem areas that was identified during the Study is in the vicinity of Dumbrell Road, Bulli, in the Collins Creek catchment. 

What is Council planning to do to reduce flooding in Dumbrell Road?

Two measures are planned which will work together to reduce the risk of blockage and culvert overflow at Dumbrell Road. First we plan to refurbish the channel between Bulli Community Centre and Dumbrell Road to reduce the risk of debris being generated from within the channel. After the refurbishment is complete, the channel will be planted with new vegetation.

The second proposed measure is a debris control device next to Gordon Hutton Park to intercept debris sourced from the upper catchment before it can be transported to the Dumbrell Road culvert.

What is a debris control device?

A structure designed to catch debris such as branches, boulders and dumped rubbish. The structure keeps the build-up of materials away from the entrance to culverts and drains, which helps stop them getting blocked.

What is a culvert?

A tunnel or drain structure that is built under a road or railway to allow water to flow underneath. 

What is a culvert headwall?

A concrete wall built at the inlet or outlet of a drainpipe or culvert.

Pictured: inlet headwall to the Dumbrell Road culvert, Bulli

What type of vegetation will be planted along the channel?

Flood-friendly native vegetation selected to help stabilise banks, reduce the supply of debris and have low maintenance requirements. 

How will this affect me?

During the first stage where we are doing channel stabilisation works, you can expect to see a Council works crew, their vehicles and equipment in the area. This work is expected to start in Autumn 2019 and be finished by Winter 2019, weather permitting. The works crew will aim to minimise disruption, however there may be some traffic control required at times. Works are expected to take place Monday – Friday, 7am to 3pm. You may experience some construction noise during these hours. We will keep you updated about our plans for the second stage of the project, construction of the debris control device, as they progress. We plan to do this work during the 2019/20 financial year.   

Who will maintain the channel?

After construction, the channel will be included with Council’s program for regular inspection and maintenance to control weed infestation and remove materials that can block the culvert.

Why doesn’t Council clear out creeks?

Council is responsible for maintaining watercourses (including creeks, overflow paths or drainage pipes) on Council-owned land and has a maintenance program for this. The majority of watercourses throughout the city of Wollongong are on private property and the maintenance of these is the responsibility of the land owner. In these cases, Council is unable to perform any work on the watercourse. If you require advice on maintenance of watercourses, please contact our Customer Service team by phoning (02) 4227 7111 or emailing council@wollongong.nsw.gov.au

In many cases, vegetation in watercourses can help reduce flood risk by slowing down the flow of stormwater, and preventing it from arriving all at once in areas where the creek bed flattens out or where several creeks join up. This effect is very important because it helps prevent serious dangers like properties or roads being flooded by fast-flowing water in a short amount of time. 

As well as helping prevent the most serious flood hazards, appropriate creek vegetation adds beauty to our city, and provides vital habitat. It helps to manage water quality by filtering pollutants, regulates temperatures in urban areas and reduces erosion that can generate debris, or damage land, buildings, or roads.


Pictured: example of creek vegetation

We are continuing to work in the publicly-owned creeks across our city to reduce infestation by problematic creek vegetation such as weeds, and replace it with stable, low-maintenance vegetation. This enhances the many functions of  our urban creeks without worsening flood risk. An example of this are the reeds you may have seen growing in detention basins. 

What can I do around my yard to help keep watercourses clean?

  • Be careful not to dispose of grass clippings and other garden cuttings in or near watercourses and remove any obstructions that may cause blockages or divert flood waters. 
  • Be aware of any drainage easements or overflow paths that affect your property. Seek Council approval before altering your driveway or footpath levels, as this may cause water to flow off the road and down your driveway.
  • Take care when planting trees near a drainage pipe. 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 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. 
  • Do not fill low-lying areas of your yard without seeking Council approval, as this may cause water to pond and increase flooding potential on your and your neighbours’ properties. 
  • Think about drainage on your property. Keep drainage inlets clear of any rubbish or blockages. Remember, large paved areas will increase runoff, so you may need extra drainage. 

How can I join the conversation?

There are a number of ways to ask us questions or share your feedback with us: