When farmland is flooded by seawater

Storm surges and king tides

Published on Tuesday, January 09, 2018

What happens to farmland which has been flooded by seawater? 

  • The impact will depend on how long the crop or pasture is covered by seawater. If it’s only for a short time – up to 48 hours – and gets good rainfall, grasses should bounce back. 
  • Rain is needed to wash the salt away. It’s likely the saltwater was diluted by the rains during the storm which measured up to 70mm.
  • The last similar event in the areas was 15 July 1995. This was during winter, there was plenty of rain to wash out, and pasture recovered well over a three month period.

Pasture and soil

  • Salt should wash away fairly quickly with rainfall. The more porous the soils the quicker it washes out.
  • Pasture dies after three days without oxygen. Overseas studies on inundation suggest:
    • 24-48 hours most pasture will recover, some discolouration
    • 48-96 hours most of the grass will die but some stems survive, clover survives
    • After 96 hours all pasture dies and requires renewal.
  • Most of the area impacted now falls in the 24-48 hour category; some pooling remains and those areas have surpassed 96 hours.
  • Your soil/texture profile affects how much seawater can impact it. Clay soils have low penetration (1-2cm); sandy soils have higher penetration (up to 15cm). This is good news for many farmers whose soil is marine clay. Near Kaiaua there is more sand-based soil.
  • Soils are not expected to become sodic.

Animal health:

  • Precautionary approach of deferring grazing until after the next heavy rainfall. 
  • Ensure stock have access to fresh clean water.
  • Talk to your vet if there are any concerns.

Actions farmers can take:

  • If it’s possible to pump seawater off, do so.
  • Make a feed budget. Consider there may already be feed shortages in the area and take this into account.
  • You may need to offload stock – make a plan and make decisions early.
  • Talk to your accountant about possible tax flexibility or other standard income assistance for you/workers.
  • Talk to your farm consultant if your pasture has been covered for several days or longer - will there be a need to regrass?
  • Talk to your farm consultant about soil testing for sodium or conductivity. Some consultants may be able to offer this as a rapid field test.
  • Talk to your local Rural Support Trust who are working with regional councils, CDEM, MPI and agri-business.

Read a more detailed analysis by Matthew Taylor, Soil Scientist and Diffuse Contamination Specialist at the Waikato Regional Council

 

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News & Alerts

Good Yarn Workshops coming up!

Tuesday, April 17, 2018

Author: Bridget Frame

Good Yarn Workshops:

  • KAIKOURA - Wednesday 9th May 10.30pm - 2pm Lobster Inn
  • CULVERDEN - Thursday 10th May 10.30pm - 2pm Rugby Clubrooms

 
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First winter storm sweeping the country

midday, 10 April 2018

Tuesday, April 10, 2018

Author: Terri Anderson

As the winter weather is making itself felt, most recently with tornadoes in Taranaki and Ruapehu, please stay safe and travel only if absolutely necessary.

Treat all lines as live and report power outages to your supplier.

Please ask for assistance if you need it, and keep an eye on your neighbours.

For updates at this stage please refer to https://www.facebook.com/TaranakiCivilDefence/ and https://www.facebook.com/ruapehudc/

Weather updates http://www.metservice.com/national/home.

Pic below of unoccupied home, taken from Ruapehu District Council facebook page.

 

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Keeping an eye on Cyclone Hola

Monday, March 12, 2018

Author: Terri Anderson

https://twitter.com/twitter/statuses/972915753044201472

NIWA: With Hola passing offshore today, its strongest winds will too!

NIWA's high resolution modelling indicates some gusts to 70 km/h for: eastern Northland, Great Barrier Island, the Coromandel, coastal Bay of Plenty, & Gisborne Ranges, then a bit gusty in Auckland tonight.

 

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What did the Fox Say?

Top 10 Drought Tips from Andy Fox on Hokonui Muster

Tuesday, March 06, 2018

Author: LindsayWright

Additional support and options for farmers to consider as they head into winter with lower than expected feed levels following the recent dry spell, enabling them all to forward plan and be proactive about risks ahead. 

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