Editorial l Flood risk now starkly revealed

00:25, Mar 06 2014

Yesterday's extensive flooding starkly proved the vulnerability of certain parts of Christchurch which had already been identified as potential flood-risk areas in a council-commissioned report released just a month ago.

That report, by Tonkin and Taylor, took a long view and warned that large parts of the city could be submerged by rising sea levels within the next century. This week's storm, which led to a combination of rain and tide which caused widespread inundation, showed us that the problem is real and immediate.

No doubt compounded by the broken stormwater system, the flooding yesterday was widespread and affected more than 100 homes in Richmond, St Albans and Mairehau, but overflowed into streets also close to the Avon and Heathcote rivers and the Estuary, where land has subsided up to 50cm following the earthquakes. The full effect of that quake subsidence hasn't been known to date. It is now.

Council officials were calling the storm a one-in-100 year event. The trouble with such assessments is that they are based on historical readings which don't mean as much as the weather becomes more volatile due to climate change, and the effects of rising sea levels are felt with the combination of the worst weather and the higher tides. Protecting land and property for future events has now ceased to be a theoretical concern for officials and householders to consider at some leisure. The threats and the problems are here and now.

Yesterday's events also turn the spotlight on to the positions of EQC, Southern Response and other insurance companies when it comes to factoring the flood risk into earthquake repairs and rebuilds. The Insurance Council has said that insurers are responsible for properties and foundations, but not the land they sit on. EQC recognises higher flood risks due to subsidence as a form of land damage, but will not pay for a property's floor level to be raised if that is not required as part of earthquake remediation. Southern Response is prepared to raise floor levels on properties in the case of rebuilds, but not repairs, and not if the work is not required to obtain a consent. These positions do not exclude what is now a very real possibility - that quake- damaged but repaired houses might subsequently be flooded because of land changes due to the earthquakes. Who should pay for what in different circumstances is not at all clear, and may have to be decided in the courts.

The Christchurch City Council needs to consider these issues carefully. It is, after all, the building consent authority and as such it is bound by section 71 of the Building Act. This states that an authority "must" refuse to grant a building consent if the land on which the work is to be carried out is at risk to one or more natural hazards (including flooding), unless adequate protection from that hazard is provided. There are perhaps 17,000 properties in flood-prone areas in the city. It is important that any work being done on them takes the now all-too- obvious flood risk into consideration.


The Press