Topic: Woolston Cut and Woolston Tidal Barrage

Topic type:

Heathcote flooding and control measures
The Heathcote River has often been praised for its slow flowing between shallow banks, but this has been the cause of numerous floods. Between 1925 and 1960 sixteen major floods occurred.

People were attracted by the appearance of the river upstream from the industrial area and had their homes built to look out on the river with its grassy banks and willow trees.

Many home owners in Richardson, Aynsley and Clarendon Terraces had their sections and garages flooded and the flood waters entered 23 houses. The situation was aggravated by the slow flow of the river around the Woolston loop.

The choice of schemes to remedy this situation was to widen the river bed around the Woolston Loop or to construct a flood channel across the neck of the loop. The latter scheme, called The Woolston Cut, was to be much more effective in reducing the flood levels upstream, and would cost one third of the river widening scheme.

The Woolston Cut
In 1986 a major flood alleviation channel, the Woolston Cut was commissioned on the Lower Heathcote River Christchurch. It was 510 metres in length and cost over two million dollars.

The Cut was designed to reduce flooding problems in the residential areas up-river. This has been very successful but problems relating to sea water penetration have been rather more severe than anticipated. The effects include bank erosion and tree death. Along the banks as far upstream as the Opawa bridge most of the trees died. To remedy the situation control gates were built at the upstream end of the Cut and left closed except in times of flooding. When they are opened the flood waters can flow rapidly through the Cut instead of slowly around the loop.

These 'control gates' at the upstream end of the Woolston Cut is also known as the Woolston Tidal Barrage. The barrage consists of four radially hinged steel gates supported on concrete piers. A concrete bridge runs over the top of the piers to provide access for servicing and monitoring gate operation and access across the river. The size of the gates and opening between piers has been configured so that three out of four openings are sufficient to pass flood water.

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Woolston Cut and Woolston Tidal Barrage

Creative Commons Attribution-Noncommercial-Share Alike 3.0 New Zealand License
Woolston Cut and Woolston Tidal Barrage by Cecil is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 New Zealand License