Flooding is the most costly natural disaster in South Australia and can have impacts on people's safety and wellbeing, the eonomy, the environment, communities and on public services. The floods linked to the extreme weather event in September and October 2016, caused an estimated $51 million of damage to agriculture and greater than $20 million damage to local government infrastructure. A changing climate and increased development on floodplains present ever increasing challenges to manage these risks.
An independent review of the extreme weather event in 2016 recommended improvements in dam and levee bank management because the failure of dams and levees can greatly increase the costs of flooding to the economy, communities and the environment.
During the 2016 floods, many dams failed or threatened to fail, endangering human life and downstream property or damaging the operation of the dam. According to a report by the University of South Australia, dam failure flood risks are significant. Evidence shows that dam design and maintenance is often not adequate: many spillways (if they exist) have inadequate flood capability and there are often structural issues with dam walls. Better regulation of dam design, construction and maintenance combined with better education, linked to an understanding of the risk rating of a dam could help to reduce the potential impact of floods.
Levee bank management.
For some communities, levee banks are an important part of flood protection, however it is often unknown who should look after their maintenance and whether they can provide the protection against flood risk, for which they were originally constructed. Levee bank failure along the Gawler River in 2016 contributed to the significant economic costs of the floods in the Virginia horticultural area.
Impacts of floods resulting from levee bank failure are inevitably high because communities are often not prepared for flood in those areas as they assume the levee bank will protect them.
Dam and Levee Bank Management frameworks.
Draft position papers have been developed, to provide a framework for improved levee bank and dam management in South Australia for discussion and feedback. The frameworks have been developed considering ideas from researchers, approaches interstate and feedback from Commonwealth, State and local government staff involved in flood management.
The dam management and levee bank policies aim to reduce the impacts of floods on the economy, communities and the environment by ensuring that:
- roles and responsibilities for dam and levee bank management are clearly articulated, agreed and understood and can be implemented
- dam management risks for both existing and new dams can be managed by landholders and do not significantly increase the potential impacts of floods in South Australia
- there is clarity on how levee banks can be factored into flood risks and flood response as there is confidence in their location, function and performance.
Priorities for improved flood management in South Australia
Flood management is a shared responsibility between Australian, South Australian and local government and the wider community.
There are opportunities for a more strategic and coordinated approach to flood management, going beyond dam and levee bank management, addressing issues such as sharing flood risk information, managing flood warning infrastructure and the interaction with stormwater management and land use planning.
The draft discussion paper on priorities for improved flood management in South Australia seeks ideas on other priority flood management issues to be addressed and how best to address these issues.
Aligning with other regulation development
If improved levee bank and dam management or other improvements in flood management require legislative changes or regulation development, these will be aligned with changes or regulation development under the proposed Landscape SA Bill or Planning Reform.