Structural barrier or 'simple baffle' wall

Year proposed

  1970

Status

  Not implemented

Location description

  Taumutu

Description of option

  A baffle wall - at least 400 ft wide - to minimise the filling up of the channel with shingle after it has been closed by sea action. Mr Royds also proposed two other minor options that would require the prior construction of the baffle wall.

Opening, closing, and lake level control description

  Baffle structure designed to assist with mechanical opening reliability and reduce effort required to excavate opening.

Maximum discharge

  above 300 cumecs

Maintenance/Management description

   Likely problems include baffle wall potentially becoming outflanked by outflowing lake, and heavy seas coming over the whole beach line bringing shingle to the landward side of the cut. Wall would be exposed to the open sea as well as scouring during lake outflows. 'A structure of this kind fronting the open sea is "as strong as its weakest pile"'

Cost description

  1969:

  Construction cost = approx $140,000

  Total annual cost of keeping lake open (with baffle) = $37,500.

Fish passage benefit rating

  Low

Potential running impacts or benefits

  Intended to improve mechanical opening reliability and reduce effort required to excavate opening.