Damning Report by Auditor-General of Thames-Coromandel Council’s Management of Stormwater Systems

In December 2018 the Auditor-General published a report on how Thames-Coromandel District Council (TCDC) (and two other councils) were managing their stormwater systems to reduce the risk of flooding.  While there are some recent improvements, overall, the Auditor-General was scathing of TCDC’s management of its stormwater systems. 

Here are the main conclusions in the A-G report– 

Incomplete understanding of the flood risk

TCDC had “an incomplete understanding of the flood risk in their districts. Much of their assessment of flood risk has been based on information collected after a flood. This reactive approach risks TCDC focusing on reducing the effects of the most recent flood, rather than considering all possible flooding events and their effects. It also means that they cannot forecast accurately, and risk being poorly prepared for unanticipated events.”

“This means that TCDC is unlikely to have had informed conversations with its communities about the potential risk of flooding and the cost of reducing that risk.”

Thames-Coromandel District Council does not know the condition of 64% of its above-ground stormwater assets and 75% of its stormwater pipes.

TCDC was unable to accurately determine how many habitable floors were flooded in recent flood events.

Councillors and Community Ill-Informed

“Weaknesses in TCDC’s information about their flood risk and the current state of their stormwater systems mean Councillors have not had all the information they need to make well-informed decisions.

TCDC needs to provide their communities with information that is relevant, reliable, and accessible so they can have the “right debate” to plan for the future. “

TCDC is Not Maintaining its Stormwater Systems

Thames-Coromandel District Council is planning to spend 89% of depreciation.

The A-G outlined his concern that TCDC is not adequately reinvesting in their assets to maintain current levels of service.

“If nothing changes, the under-investment will increase the risk of the stormwater system being unable to cope with heavy rainfall, resulting in people’s properties being flooded.

Our concerns are based on the gap between the depreciation of stormwater assets and what councils were spending on the renewal of those assets. This gap indicates that the assets are likely to be wearing out faster than they are being renewed.”

OAG chart

Between 2014/15 and 2016/17, TCDC spent 36% of planned capital expenditure.

 Poor Understanding Climate Change Flood Risk

The Auditor-Gen’s report emphasized that information about climate change and land use change is needed to understand flood risk.

“Climate change is expected to increase existing risks and create new risks. Climate change will affect flood risk through  

  • projected changes in rainfall
  • a likely increase in extreme rainfall in most areas
  • an increase in sea levels that decreases the effectiveness of stormwater systems in draining the rainfall away, because of the backflow of water into pipes and watercourses;
Davy St sunny day flooding 26 Nov 2018 3.9 m tide
Davy Street Thames at Spring Tide – No Rain

“As a consequence, flooding in New Zealand is likely to become more intense and more frequent. TCDC needs to “consider the effects of climate change and urbanisation to understand their future flood risk and ensure that their stormwater systems maintain their effectiveness in reducing the risk of flooding.”

TCDC has begun development of its Shoreline Management Plans around the coast.  If these plans are properly resourced and use the best expertise they will hopefully provide much-needed information on coastal flooding risk.  But as the A-G stated in typical conservative fashion TCDC “has more to do”

(In response to the report, TCDC has indicated that they –
• Are planning further modelling to identify the flood risks and the capacity of the
stormwater systems of the main towns on the Coromandel.
• Have improved their asset management practices, including the introduction of
new asset management software and the implementation of a council-wide asset
management policy.
• Have increased their planned capital spending by 72 per cent (compared to 131
per cent by Porirua City Council and 31 per cent by Dunedin City Council), primarily
to renew stormwater infrastructure and to improve levels of service.
• Has created a new team to manage the delivery of capital projects.

TCDC mayor, Sandra Goudie, says the report makes it clear that the Auditor-General
understands that TCDC is making improvements in the way stormwater is managed on the Coromandel. “We need to keep in mind that no local council in New Zealand can cope with extreme weather events,” she says.  “I’m confident that we’re moving in the right
direction with regard to not only our attempts to manage our stormwater systems better, but also with regard to investment in our infrastructure in general and also our attempts to manage coastal erosion as effectively as possible.)

Unfortunately these last comments talking about coastal erosion in the context of stormwater show a fundamental misunderstanding of future coastal flooding risk.  In coming decades sea flooding, not erosion will be the dominant flooding risk as seas rise.