Flooding major disaster for Sth Canty

FLOOD RISK: South Canterbury is more likely to be affected by a flood than any other natural hazard.
FLOOD RISK: South Canterbury is more likely to be affected by a flood than any other natural hazard.

The rupture of the Alpine Fault would create the greatest civil defence emergency in South Canterbury, but we're most likely to be affected by flooding.

The Canterbury Civil Defence Emergency Management Group's draft long-term plan went out for public comment yesterday.

According to the plan, the potential consequences of flooding in South Canterbury were ''minor to moderate'', but its likelihood was high.

Timaru District Council emergency management adviser Lamorna Cooper said people took for granted the effects of flooding.

''South Canterbury's flooding can be generated by two different weather patterns - affecting either the coastal rivers in the east or the Rangitata as weather patterns flow over the Southern Alps,'' Ms Cooper said.

''It doesn't necessarily have to be caused by a river overflowing. It can just as likely be caused by intense rain events concentrated in one particular area, as we have seen in Pleasant Point in recent years.

''In 2011 and 2012, South Canterbury experienced ''one-in-a-hundred year'' floods at Washdyke and Pleasant Point.

Last year, Washdyke ratepayers voted in favour of Environment Canterbury's proposed $1million flood protection scheme.

''We have to prepare for one flooding event of significance every year,'' Ms Cooper said.

''It's about the cumulative effect.

Several homes with minor flood damage can add up to a major event which stretches all agencies,'' she said.

However, the draft plan said the Alpine fault posed an ''extreme'' risk if it ruptured. The fault, which is classed as being active one in every 200 to 400 years, could produce up to a magnitude 8 earthquake.

The last known event was in 1717.''In localised civil defence emergencies you can call on the assistance of other councils, but if the Alpine Fault went, it would affect all districts in the South Island and everyone would be dealing with it,'' Ms Cooper said.

Ms Cooper said South Canterbury's other significant hazards were rural fire, snow, major air accidents and heavy rainfall.

Heavy rainfall could trigger many other hazards, such as flooding and coastal erosion.

Ms Cooper said the inclusion of major air accidents took into account the fact the Timaru airport could take larger aircraft if required, thus increasing the potential for a larger event.Submissions on the draft long-term plan close on February 21.

The Timaru Herald