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Alexandra Flood Remediation Project

Areas in and around the township of Alexandra in New Zealand’s South Island have been inundated by floodwaters six times in the last 25 years.

Floods in January 1994, December 1995 and November 1999 had the highest water levels. The last two events caused extensive property damage and major disruption to the community.

Increased flood levels are a result of sediment settling in Lake Roxburgh after the construction of the hydroelectric dam in 1956. This effect was expected, but underestimated by designers at the time. Flood frequency was also underestimated, until the passage of time and events provided a longer period for statistical evaluation.

Further dams were expected to be built upstream in a comparatively short time, halting the flow of sediment into Lake Roxburgh. Some attempt was made by the Crown in the early 1980s to purchase land to higher levels to remove the effects of flooding but this was not comprehensive and, as later events showed, continued to underestimate the elevated flood heights.

In September 2000 the Government agreed to a package totaling $22.134 million (GST inclusive) to protect Alexandra from future flooding by the Clutha River. This package followed negotiations between senior executives of Contact Energy Ltd, the Deputy Prime Minister and the Minister of Finance in which the parties agreed to put in place arrangements that:

  • provided the Alexandra community protection against significant future floods
  • acquired certain flood prone properties (or easements over properties) and properties required for the stopbanks, and
  • resolved all past flood damage claims in association with the acquisition of these properties.

Contact Energy Ltd agreed to contribute $6.8 million (GST exclusive) for purchasing property and easements, settling outstanding claims for flood damage and constructing stopbanks in Alexandra. The Government agreed to match Contact Energy Ltd’s contribution and cover contingency costs over and above Contact Energy Ltd’s capped contribution. The Government’s contribution for the flood remediation works was initially $10.484 million. This increased by a further $5.118 million in April 2001, as a result of valuations and engineering reports.

The Government also agreed to contribute $4 million towards community amenity enhancement including, landscaping, street works and the restoration of facilities such as the swimming pool owned by the Central Otago District Council. Three flood-affected community amenity properties were also purchased.

The project included building flood protection barriers to accommodate a flood crest level of 143.25 metres, one metre higher than the highest previous flood peak recorded in Alexandra in November 1999. A number of properties had to be purchased and structures demolished or removed to make way for the stopbanks or because they still were at risk of flooding. Easements have been purchased for land which is not protected by the stopbanks but which is at risk of some inundation from time to time.

The Alexandra Flood Remediation project was commissioned by the Prime Minister and Deputy Prime Minister in March 2002.

Last updated: 17 September 2007