Why is the Flood Study being reviewed and what’s changed?
What about historical floods?
At the start of the Collins Creek Flood study review, we sent out more than 6,000 brochures and questionnaires asking the community about the floods they have experienced in the past. We received over 500 responses. Many people reported having experienced a flood in the past and specifically in August 1998. Those residents that have reported flooding are captured by the flood extend of our flood maps which gives us additional confidence in our results. The 1998 flood in this area was not as big as a 1% Annual Exceedance Probability (AEP) flood, which would explain why some areas are within the mapped flood extent while residents haven't been impacted by a flood to date. A 1% AEP flood means there is a 1% chance of a flood of this size or larger occurring at a particular location in any given year.
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?
How does Council manage flood risk?
- 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
How do you predict flood levels?
There’s a chance that floods of any size will occur in future. As the size of a flood increases, the chances of it occurring becomes smaller. Some rare types of floods may not have occurred for over 100 years, so we have to predict the height of future floods using computer models. These models produce different flood levels and velocities (speeds) for a variety of different-sized floods. To predict flood levels, Council works with experts to establish and operate the computer models. Council also gets valuable community input on historical floods so we can adjust the model and make sure it copies what’s happened in the past.
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 can I join the conversation?
- Bulli Senior Citizens Centre, Saturday 22 June 9:30–11am
- Bulli Surf Club, Tuesday 25 June 4 – 5:30pm
How will my feedback be used?
At the conclusion 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.