River Dredging to Fix Post-quake Flooding

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Posted December 11, 2018

Dredging has started on a Blenheim river that lost several sections of riverbank in the 7.8-magnitude earthquake, causing flooding upstream in heavy rain.

The Marlborough District Council started dredging the ?paoa River on Tuesday as part of a $200,000 project to bring it back down to pre-quake water levels.

Slumping of the ?paoa riverbank, brought on by the Kaik?ura earthquake in November 2016, caused water levels to rise in the lower ?paoa and Taylor River by up to 30 centimetres.

The Taylor River had since become more prone to flooding in heavy rain, especially around the amphitheatre in central Blenheim.

The council had already reduced the amount of aquatic weed in the river, which helped with river levels and water flow.

Council rivers and drainage engineering manager Geoff Dick said this next stage would see the ?paoa River's edges returned to their original position.

Dick said the 7.8-magnitude earthquake caused a lot of damage to the river, including "liquefaction-induced lateral spread" along a "large number of bends" on the lower ?paoa River.

Work was also set to begin from December 10 on a section of the stop bank north of Park Terrace to permanently repair earthquake damage.

The long-standing project involved the reconstruction of the stop bank to modern standards, including a more stable riverside slope.

A new concrete block retaining wall and boundary fence would be created along the new boundary, and the walkway from Stuart St into town would be upgraded.

The council purchased the land adjacent to the river to secure maintenance and increase public access through a new extension to the Taylor River Reserve.

Access to the reserve from Stuart St and past Opawa St would be closed while reconstruction was underway. An alternative access path to the ?paoa River would be available from Opawa St.

The riverside track would be closed from December 10 to December 21. It would re-open for the Christmas holiday period, before work resumed again on January 7, 2019.

The $400,000 construction project was expected to be completed by April next year.

Source: stuff