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

Next SRST Meeting

Thursday, January 17, 2019

Author: SuperUser Account

Next meeting of the Southland Rural Support Trust -

General Meeting

Location:  FF Building, Invercargill

Tuesday 12 February 2019

Time:

Trustees Only: 10am

Facilitators and Key Partners: 11am

Stakeholders: 1.00pm

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Categories: Southland

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Flooding watch in north island

24 December 2018 10am

Monday, December 24, 2018

Author: Terri Anderson

Monday 10am: Heavy rain for Northland, Coromandel Peninsula, Bay of Plenty and Gisborne from Tolaga Bay northwards.

Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.

Before severe rain

· Keep an eye on weather reports and enact your plans for moving stock and supplementary feed to higher ground if needed.

· Clear gutters and drains where possible

· Have to hand a smartphone, a charger for the car, a torch, and a battery-powered radio

· Check your insurance cover details

 

During a flood or storm

· Keep an eye on https://www.civildefence.govt.nz/ and your regional council websites/facebook or radio station

· The safety of you, your family, and workers comes first.

· Move stock to safety, shelter and water and make sure they can't wander. Are the electric fences working?

· Turn off utilities if told to do so by authorities as it can help prevent damage to your home or community. Unplug small appliances to avoid damage from power surges.

· Do not attempt to drive or walk through floodwaters unless essential.

· Check power and phones. Report outages.

· Check dogs, poultry and pets.

· Check on neighbours - do they need help or can they help you?

· Check buildings at risk, feed stacks. · Use generators if necessary to keep pumps, refrigeration, electric fences and household appliances running. Flood pumps may need attention. 

 

Further information:

https://www.dairynz.co.nz/business/adverse-events/flood/

https://beeflambnz.com/news-views/topics/flooding

MPI Animal welfare 

 

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Flooding watch in north island

24 December 2018 10am

Monday, December 24, 2018

Author: Terri Anderson

Monday 10am: Heavy rain for Northland, Coromandel Peninsula, Bay of Plenty and Gisborne from Tolaga Bay northwards.

Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous.

Before severe rain

· Keep an eye on weather reports and enact your plans for moving stock and supplementary feed to higher ground if needed.

· Clear gutters and drains where possible

· Have to hand a smartphone, a charger for the car, a torch, and a battery-powered radio

· Check your insurance cover details

 

During a flood or storm

· Keep an eye on https://www.civildefence.govt.nz/ and your regional council websites/facebook or radio station

· The safety of you, your family, and workers comes first.

· Move stock to safety, shelter and water and make sure they can't wander. Are the electric fences working?

· Turn off utilities if told to do so by authorities as it can help prevent damage to your home or community. Unplug small appliances to avoid damage from power surges.

· Do not attempt to drive or walk through floodwaters unless essential.

· Check power and phones. Report outages.

· Check dogs, poultry and pets.

· Check on neighbours - do they need help or can they help you?

· Check buildings at risk, feed stacks. · Use generators if necessary to keep pumps, refrigeration, electric fences and household appliances running. Flood pumps may need attention. 

 

Further information:

https://www.dairynz.co.nz/business/adverse-events/flood/

https://beeflambnz.com/news-views/topics/flooding

MPI Animal welfare 

 

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Dairy NZ flood information

for Otago and Southland

Wednesday, December 12, 2018

Author: Terri Anderson

DairyNZ

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Categories: National, Otago, Southland

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