Control structure on lakeside of beach barrier

Year proposed

  2012

Status

  Not implemented

Location description

  Near Taumutu

Description of option

  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. 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

  The adjustable sheet piling wall would prevent the lake falling below a set water level when the lake is opened to the sea. The wall could have 3 levels to: 1) maintain minimum lake level, 2)  rapidly spill large flows & 3) stop flows overtopping wall end

Maximum discharge

Maintenance/Management description

Cost description

  More effort may be required to open lake mechanically due to impact of weir.

Fish passage benefit rating

  Medium

Potential running impacts or benefits

  Structure would ensure min lake level and prevent back flow of seawater into lake (likely to adjust to allow some seawater). Over time the lake salinity would reduce which, combined with higher minimum lake levels, would enhance macrophyte bed recovery.