INFRASTRUCTURE PERFORMANCE DURING JUNE 2015 FLOOD EVENT
A report from Water and Waste Services provided an overview of the extreme rain event of 3 June 2015, its impacts and the performance of the drainage infrastructure. It focused primarily on the impact of the events that were experienced in South Dunedin, as that had been an area of particular public interest.
The analysis presented in the report was based on a flow balance model that had been developed for the purposes of assessing the impact of pumping station performance. The flow balance model had also been used to assess the relative impacts of the high groundwater levels in South Dunedin that significantly increased the amount of runoff generated by the rainfall.
The rain event significantly exceeded the capacity of the stormwater system in South Dunedin. The post event analysis had identified some opportunities to improve the performance of the existing infrastructure in large scale rain events, but would not prevent serious flooding in a similar future rain event.
Work was already underway to redesign the screens at the Portobello Road pumping station to make it easier to keep them clear during large events and was expected to be completed during the current financial year.
The planned infrastructure improvements would slightly reduce the impact of future flooding. However extensive flooding of low lying areas in large scale rain events or long duration rain events remained highly likely, particularly if the rain event coincided with high groundwater conditions.
The General Manager Infrastructure and Networks and Group Manager Water and Waste commented on various aspects of the report and responded to questions from Councillors.
Councillor Thomson left the meeting from 3.52 pm to 3.55 pm and Councillor Staynes left the meeting from 3.54 pm to 4.35 pm during the course of questions. Councillor Vandervis left the meeting from 4.36 pm to 4.38 pm and Councillor Peat left the meeting at 4.38 pm.
Following questions it was moved (The Mayor/Wilson):
“That the Council:
a) Notes the report on Infrastructure Performance during the June 2015 Flood Event.”
b) Notes the serious implications and consequences of rising ground water levels in parts of Dunedin.
c) That staff investigate and report back on a work programme to address the issues caused by rising ground water levels in South Dunedin and other parts of the city.
d) Notes that the report should include:
i) Possible responses to a range of sea level and climate change scenarios.
ii) Budgetary, infrastructural and community implications of both scenarios and responses.
iii) Catchment wide stormwater systems, ownership and effective management.
e) Notes that Council’s long term aims, as much as possible, are:
i) that the environment of affected parts of Dunedin is improved to an acceptable level.
ii) that no Dunedin citizen, ratepayer or householder is seriously disadvantaged as a result of any measures taken to deal with the challenges of ground water and rising sea levels.”
Councillor Peat returned to the meeting at 4.42 pm.
During discussion the work of staff was acknowledged during the time of the flooding.
Following discussion Motion (a) was put and carried on a division 14:0 with one abstention.
For: Councillors Benson-Pope, Bezett, Calvert, Hall, Hawkins, Lord, MacTavish, Noone, Peat, Staynes, Thomson, Whiley, Wilson, The Mayor
Council minutes – 30 November and 14 December 2015 7
Abstention: Councillor Vandervis, on the grounds that the motion did not identify the major flood causes as he understood them
Motions (b) – (d) were put and carried on a division 13:1 with one abstention.
For: Councillors Benson-Pope, Bezett, Calvert, Hall, Hawkins, Lord, MacTavish, Noone, Peat, Staynes, Thomson, Wilson, The Mayor Against: Councillor Whiley Abstention: Councillor Vandervis
Motion (e) was put and carried on a division 12:2 with one abstention.
For: Councillors Benson-Pope, Bezett, Hall, Hawkins, Lord, MacTavish, Noone, Peat, Staynes, Thomson, Wilson, The Mayor Against: Councillors Calvert, Whiley Abstention: Councillor Vandervis
It was moved (The Mayor/Staynes):
“That the meeting adjourns for ten minutes.”
The meeting adjourned from 5.35 pm to 5.47 pm.
[Item 17 ends]