It never rains, only pours for region

03:31, Jun 27 2014
Nelson flooding
FLASH FLOODS: The latest downpour turned streets into rivers in just an hour.

Another year, another flood. The region has been hit again by a deluge that raises more questions about the ability of urban infrastructure to cope with increasingly frequent severe weather.

Central Nelson suburbs were hit this time with Wednesday's downpour turning streets into rivers in just an hour.

It follows the flash flooding in Richmond and Stoke in April last year that damaged homes and businesses, and the December 2011 floods that left a swathe of destruction across the region.

Those two events brought insurance claims totalling more than $50 million, and also left councils with multi-million dollar repair costs and further flood protection work.

On the two year anniversary of the 2011 floods Insurance Council chief executive Tim Grafton said climate change scenarios all pointed to the Nelson area receiving higher levels of rainfall.

Unless measures were put in place to minimise the social and economic effects, the likely increased severity and frequency of severe weather events would push up costs, he warned.


One of the disturbing aspects about the latest flooding is how quickly it happened.

As one resident of hard-hit Murphy St put it: "There was just nothing and then there was everything."

Other long time residents in Toi Toi, Victory and Nelson South, who watched their streets turn into fast-flowing rivers, say they have never experienced anything like it.

One was puzzled that a nearby stream had not overflowed, suggesting a blockage could be responsible for the flooding. Others reported storm drains simply could not cope, and with the ground already saturated, the water had nowhere to go.

After the April floods last year the Nelson and Tasman councils committed to improving stormwater culverts and drains in Stoke that became blocked and overflowed. They also commissioned further work to improve flood capacity in the area.

The Nelson council will undoubtedly look at what can be learned from the latest deluge, and what actions can be taken to lessen the damage from future events.

It may not be an easy assessment. As a Tasman official pointed out in the wake of the 2011 floods, that were rated as a one-in-500 year event, councils could technically build infrastructure to cope with such storms, but the cost and the amount of land required would be prohibitive.

Last year's floods were classed as a more than one-in-100 year event, a threshhold that will still require a substantial infrastructure upgrade to meet.

This week's downpour was short, sharp and localised, but still managed to wreak a degree of havoc. The scientific consensus is clear that severe weather events will become more frequent, and Nelson is in the firing line of moist northwesterlies. To meet the challenge, the council has to continue the acceleration of upgrades to old stormwater systems. It's a spending priority that's likely to be accepted by most ratepayers.

The Nelson Mail