River Works


August Weather Event 2022

Information relating to the recent weather event in Marlborough

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River Works

The Taylor River Flood Detention Dam, built in 1965, is the largest of its kind in New Zealand. It is 20 m high and involved 400,000 m³ of earthworks. The dam operates by detaining a one-day flood in the dam releasing its flow over two days, thereby reducing a 300 m³/sec flood peak to a 108 m³/sec peak.

The Wairau Diversion is also the largest of its kind in New Zealand. It is capable of carrying 3,000 m³/sec - 55% of the Wairau River's flow - on a direct, shorter path to the sea. Some 2,000,000 m³ of material has been removed from the diversion channel.

The Conders stopbank/groyne at Conders Bend near the Wairau (Renwick) bridge on State Highway 6 is vital in keeping the Wairau River out of the old Upper Ōpaoa River channel that leads to Blenheim.

Other river works data is:

Works Stopbank
Rock in

Wairau Floodway

98 km

850,000 tonnes

Upper Ōpaoa /Roses Floodway

45 km

70,000 tonnes

Lower Ōpaoa /Taylor Floodway

44 km

50,000 tonnes

Drainage Channels'
Flood Pumps

Lower Wairau Drainage Area

160 km