Flooding on the Wairau Plain

Blenheim and the Wairau floodplain have experienced at least one damaging flood every decade since European settlement. In the early days, floods occurred so often and flood control works were so ineffective, that Blenheim was known as the Beaver or Beavertown. ¹

Flooding in the centre of Blenheim, with the Marlborough Express office in the background. Marlborough Historical Society - Marlborough Museum Archives. 998.165.0007
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The size of Blenheim's floods was virtually impossible to estimate because they were uncontained and widespread.

The main floodwaters which inundated the Wairau Plain came from storms sweeping across the Richmond Ranges and dumping heavy rainfall in the various tributaries (such as the Goulter, Northbank and Waihopai Rivers) of the Wairau River.²

An earthquake in 1848  lowered the bed of the Wairau Lagoons by 1.5 metres which increased tidal movement of water, improved navigability over the Wairau Bar and provided better boat access into the Wairau and Ōpaoa/Opawa Rivers.³

Trading boats went up the tidal Ōpaoa/Opawa River and this trading post became the town of Blenheim - at the confluence of  the Taylor, Fairhall, Omaka and Upper Ōpaoa/Opawa Rivers and their floodwaters.⁴

The Wairau plain was regularly inundated. Major floods occurred in 1868 and 1923 when an unusual weather pattern caused the Taylor and Wairau Rivers to simultaneously flood.

In February 1868, rain fell from the South East for 20 hours and then the wind changed to North West and rain fell for another day. "From hill to hill there stretched an unbroken sheet of water, which swept on towards the sea, carrying....dead and drowning sheep, ripened corn sheaves and even the goods and chattels of the waterlogged farmers."⁵  

Market Place in flood [David Burns, saddler, holding broom]. Looking from Market St. N. towards Government Buildings. Marlborough Historical Society - Marlborough Museum Archives. 0000.900.0810
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With the demise of the Marlborough Provincial Council in 1874, several river boards  (including the Spring Creek and Lower Wairau river boards) were established on the floodplain to look after the interests of "their" districts.⁶  However there were many years of quarrelling between the rival river boards, which often carried out work detrimental to the settlers on the opposite sides of the river.⁷

Floods in 1904, 1911 and 1916 were large and damaging  in spite of intensive river works carried out from 1877 to 1902.⁸ Something had to be done. Coping with the flood menace was a huge drain on local body coffers, with £12,000 of flood protection works wiped out in one event.⁹

In 1917, a Government Commission recommended that one authority should be appointed to control the whole of the river and its tributaries.¹⁰ In July 1921, The Wairau River Board was formed and the problem of flood prevention could at last be tackled for the benefit of the whole plain.¹¹

The Wairau River Board (1921 to 1956) began a comprehensive plan for the rivers of the  floodplain. Stop banks were raised and moved back within a widened floodway on the lower Wairau River. Further up river, groynes were constructed to hold the river bank.  The Fairhall River was diverted into the Ōpaoa, and the course of the Taylor River through Blenheim was straightened. Although reduced, flooding still continued. ¹²

With increased government powers and subsidies, the Marlborough Catchment Board took over river control between 1956 and 1989. A new river scheme included the Taylor flood detention dam, the Wairau Diversion, a guide wall at the Wairau River mouth and extensive stop bank upgrading. ¹³ 

Cat stuck on the roof of the Tuamarina Dairy Factory during the 1983 flood. Marlborough Historical Society - Marlborough Museum Archives
Click image to enlarge

Marlborough residents were reminded of the might of the Wairau again in 1983. Heavy rain saw the river rise steadily on Saturday 9 July. The flood rapidly developed and early on Sunday, stop banks overflowed and were breached near Tuamarina causing extensive flooding. Life and property were at risk, with some evacuees helicoptered from the roof of the local cheese factory. The flooding caused stock losses and widespread damage.  The Marlborough Catchment Board learnt a lot from this flood, but maintained there would have been much greater damage if the Wairau Valley Scheme had not existed. ¹⁴

The Marlborough District Council took over river responsibilities in 1992 and set about another major upgrade to the Wairau system, still continuing to this day. 

Story written, 2009, by Joy Stephens and Brin Williman, Rivers & Drainage Engineer Marlborough District, with involvement in Marlborough river works for more than 20 years.

Updated May 2022

Sources used in this story

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