It has now been two years since the June 2015 floods which caused damage, disruption and upheaval for many local residents and businesses, particularly in South Dunedin.
Since then, the Dunedin City Council has made a significant effort to understand the causes of the flooding and reduce the impact of similar occurrences.
We have addressed infrastructure issues which contributed to the floods.
A new filter screen has been installed at the Portobello Rd pumping station. The old screen and design meant debris blocking the screen could not be easily cleared by staff. This meant stormwater flows were not pumped away as quickly as they should have been and this made the flooding worse. The new screen is working well.
Looking forward, the focus is on how we improve the capacity of the stormwater system. This is because in the long term scientific and central government advice tells us to expect more frequent and severe rainstorms.
We have identified some options that need further detailed investigation to ensure any work would be successful, and the funding for this detailed investigation will be budgeted into next year’s long-term plan, along with an estimate for carrying out the physical works.
The 1500 mud tanks in South Dunedin have all been subject to rigorous cleaning and inspection. The tanks are clear and in good working order. However, leaves and debris on the grates can prevent water getting into the tanks. This can cause surface flooding on the roads.
We are regularly sweeping streets around the city. However, the reality is we can’t be everywhere at once. Therefore, we also greatly appreciate efforts by residents to rake leaves and debris from the grates near their homes, particularly during the autumn months, or alert us to problems (03 477-4000).
We have introduced new minimum floor levels for mainly residential buildings, including new homes, across low-lying parts of the city. This includes South Dunedin but is not limited to this part of the city. In most areas, these levels will be higher than the current specifications and will provide a greater level of protection for new residential buildings in heavy rainfall events.
As the response to the April 2017 heavy rainfall event demonstrated, we learnt lessons from the June 2015 floods in respect to civil defence emergency management.
In the end, much less rain fell in the April 2017 event than was initially forecast. However, the proactive measures taken such as giving out thousands of sandbags, having staff and volunteers out door-knocking in vulnerable areas, and setting up information centres were all very much appreciated by the community and demonstrated that we are ready to respond.
Our community development team has also been engaging with the South Dunedin community over the past two years, including allocating a community development adviser to the area for 20 hours a week.
This adviser is meeting regularly a large number of groups that operate in South Dunedin, to explore ways to strengthen the community’s resilience.
Many of these people live in South Dunedin, and all have strong networks. We will be using these networks so residents can share ideas about their preferences as to how we respond to storm events and any challenges due to rising sea levels.
Opening the South Dunedin Pop-up Community Hub later this year will also help to further strengthen the relationships and increase the DCC’s presence. The other main threat in the long term, as outlined in the Parliamentary Commissioner for the Environment’s 2015 report, is rising sea level forcing up groundwater.
The low level of South Dunedin, along with high groundwater levels, makes flooding more likely. Any rise in sea level will increase the risk and potential impact of this already flood-prone area. To address this, we are working closely with the Otago Regional Council as it gathers data about changes that happen.
The DCC and the ORC are working together to monitor environmental changes including sea level rise now and into the future.
We need to have enough information to understand what changes are under way so that we are well prepared to take action if sea level rise causes the groundwater in South Dunedin to rise in the coming decades.
This work will mean that we can identify trigger points which may require the community to adapt and change. Predicting the nature and rate of environmental change is complex and uncertain. However, if we begin now, we can respond to the changes in a co-ordinated and considered way, with a fully informed community that is involved as options and ideas are put forward.
- David Benson-Pope chairs the DCC’s planning and environment committee.
