Channel to Forsythe combined with sheet pile weir at Taumutu

Year proposed

  2012

Status

  Not implemented

Location description

  Canal to Wairewa outlet combined with sheet pile weir at Taumutu.

Description of option

  A canal from Lake Ellesmere to Lake Forsyth was proposed, with a permanent pier outlet structure from Lake Forsyth out into the sea. See earlier (database option 26). This could be used in conjunction with a 500 to 600m long steel sheet piling wall driven deep into the gravel on the lakeside of the beach barrier extending across the area usually opened by bulldozer (database option 27). Sheet piling would be extended sufficiently to prevent erosion at the ends of the wall or below the pilings. A section of the wall could be raised or lowered as required to achieve the desired water level in the lake (Gibbs & Norton, 2012).

Opening, closing, and lake level control description

  Canal outlet to Wairewa provides almost continuous fish passage and normal water level control; the large sheet pile weir provides flood relief and the flexibility to allow saltwater intrusion.

Maximum discharge

Maintenance/Management description

Cost description

Fish passage benefit rating

  Medium

Potential running impacts or benefits

  Te Waihora water would assist in maintaining Wairewa opening (i.e. potentially continuous fish passage), good control over saltwater intrusion, adjustable minimum lake levels.