Discussion of Flood Sizes


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Discussion of Flood Sizes

There are varying levels of floods.

Major floods

These occur when the Wairau, Omaka or Ōpaoa rivers break out of their floodway stopbanks and can be life-threatening. The police, Civil Defence and other agencies will be involved, with radio stations used for messages to the public. The township of Blenheim has been hit by flood, but major floods are rare. The last was the July 1983 flood of the Wairau River.

Go to the Civil Defence Radio page for more information on emergency messaging

Moderate floods

These occur when minor river breakouts occur, perhaps from smaller rivers such as the Pukaka or Waitohi, or from Ruakanakana Creek, or minor overflows from the bigger rivers of Wairau, Ōpaoa, or Taylor. Life is not directly threatened by moderate floods, but there is potential damage to farm stock, houses and property. Roads are often closed. Civil Defence is not involved. Such events occur typically once every five years and last occurred in July 1998, involving many rivers in the district.

Small floods (freshes)

These occur predominantly in the Wairau River and affect farmers and contractors using riparian or floodway land. Stock and machinery need to be moved to higher ground. These floods typically occur every four months.