The plaque at the mouth of the Waihao River, east of Waimate, was unveiled at a ceremony attended by about 80 people to mark the centenary of the Waihao Box, a vital component in the Wainono drainage system.
That was appropriately done by Peter Hayman, grandson of Walter Hayman, the first chairman of the Wainono Drainage Board when it was established in 1868.
The simple wooden structure, which allows water to flow through the coastal shingle bank, especially in times of floods, protects about 2500ha of rich, productive farmland alongside the lower reaches of the river.
It is the second on the river. The first, about 2km further north, was washed away about 16 years after it was built in 1896.
Board chairman Mick Laming said at the celebrations yesterday that a major part of the second structure, built in 1910, remained but over the years had been extended about 53m inland because of coastal erosion and reduced by about the same amount on the sea side.
"It's not just for drainage, but also for recreation and the fishery. It is a historic structure that has served our community in so many ways over the years."
Farmer Murray Bruce, whose land borders the river opposite the box, outlined its history and said the box represented a significant amount of work by pioneering families.
But it was not without controversy.
When built in 1910, the drainage area was extended to help pay for it, a move challenged legally as far as the Privy Council.
Other speakers included chief executive Bryan Jenkins, of Environment Canterbury (ECan) which administers the drainage system, Mr Hayman, Waimate District Council council Peter Foley, who represents the area, and Waitaha representative Anne Te Maiharoa Dodds.
