Drain Blockage Guidelines
For information on who is responsible for identifying and removing blockages in the stormwater system please refer to the Stormwater Drain Blockage Guidelines (PDF).
Build Over Easement Guidelines
For information regarding consent to build over stormwater easements please refer to the Build Over Easement Guidelines (PDF).
To apply for consent to build over an easement please refer to the Easements / Stormwater page.
Interim Adjustments for Rainfall Intensities for Stormwater Design
ARR November 2024 Updated Climate Change Factors
General Information
Stormwater design follows engineering standards to estimate how much water runs off an area after a storm. This can be done using formulas or computer models. As better methods become available, approaches to stormwater design change.
Climate change is complex, and our ability to predict its effects has improved over time. The latest report from the International Panel on Climate Change (IPCC) has updated how future rainfall patterns are predicted. These new methods provide better estimates of how rainfall may change and how to manage stronger storms. Predictions now extend up to the year 2100.
As rainfall increases, more water will run off into drainage systems. This affects the size of underground pipes needed to carry stormwater (called the minor drainage system) and how excess water flows overland (called the major drainage system).
Australia’s key stormwater and flood management guide, Australian Rainfall and Runoff (ARR), now includes the latest climate change data. In November 2024, the ARR Committee updated climate change factors that engineers must use when designing drainage systems.
With increased rainfall intensities, this results in:
- More catchment runoff
- Requiring larger underground drainage systems
- Increased surface water flow especially in urban areas
- Higher costs for councils, developers, and the community
To manage this, Kingborough Council is updating its stormwater design standards. Previously, underground systems were designed for a storm with a 5% chance of happening each year (5% AEP). Now, designs will be based on a 10% AEP storm, meaning a more frequent storm but with a lower intensity is used as the standard.
For all council and private development projects:
- Major drainage systems must handle a 1% AEP storm for the year 2100
- Minor drainage systems must handle a 10% AEP storm for the year 2100
For Frequently Asked Questions and Information on Climate Change factors refer to these websites.
🔗 Engineers Australia: Climate Change FAQs
🔗 ARR Data Hub: ARR Data Hub
For Engineers, Consultants, and Developers
Kingborough Council has reviewed the latest climate change factors in line with the latest IPCC reports and Australian Rainfall and Runoff (ARR) updates.
- Previously, the Council used a 22.5% increase in rainfall intensity for the year 2100.
- The new factors vary depending on the storm type, location, and climate model used.
- Kingborough Council has adopted an interim standard:
- SSP3-7.0 for catchment analysis (major drainage)
- SSP2-4.5 for underground drainage design (minor drainage)
Changes include:
- Underground systems were previously designed for a 5% AEP storm.
- This has been updated to a 10% AEP storm to reflect changes in rainfall predictions.
To find the latest climate change factors:
- Visit the ARR Data Hub.
- Select the location and check the climate change factors box.
- Click submit.
- Example: For Kingston, the SSP3-7.0 factor for a 2-hour storm in 2100 is 1.55.
Effective Date
These updates apply to all stormwater designs, catchment analyses, and flood studies from 1 February 2025.
