New Report Confirms Risks to Whitianga Stormwater Spending

Back in August, I pointed out that the Thames-Coromandel District Council had ignored Government sea level rise guidance and Regional Council sea flooding maps when considering the proposal for a $6.5 million upgrade of the Whitianga Town Centre. According to that advice and mapping, the whole project area could potentially be flooded by the sea in coming decades. 

Now a major new report – “Climate Change & Stormwater and Wastewater Systems” has concluded that many coastal stormwater and wastewater systems will not be able to cope with climate change stresses and sea level rise.

The report’s co-author, Professor Iain White of Waikato University says the increase in extreme rainfall events would also add stress to the system by overwhelming the networks, restricting opportunities for maintenance, and increasing the occurrence of infiltration of wastewater into stormwater.

“We already know that sea level rise will affect all coastal infrastructure, and as many of our water networks use gravity to discharge to water bodies, the most costly areas of the network are often located in low-lying areas or on the coast,” White said. “From this, increasing sewage overflows, pipes corroded by salt water, and exposure to liquefaction are all more likely.”

An increase in the number and frequency of coastal storms would hit coastal infrastructure, in particular, causing increasing inundation, physical damage, and electrical failure at treatment plants.

Yet in spite of this mounting body of evidence, the council seems hellbent on proceeding with the Whitianga upgrade project including spending millions on stormwater systems which seem doomed to come under stress from climate change and eventually fail due to rising seas.

The council still refuses to obtain an expert assessment of the risk of sea flooding before funds are committed.

The report has major implications throughout the District. For example, Thames’s wastewater treatment plant is situated on low-lying land only about 0.5 m above sea level

 It is astounding that the Council remains oblivious to the way climate change is predicted to affect our vital stormwater and wastewater systems. 

“This will have a considerable impact on many aspects of New Zealand life, including health, disaster resilience, drinking water, ecology, and transport, not to mention how flooding or infrastructure failure will impact on communities,” said Professor White

see here for more comment from Iain White