Managing flooding

Civil Engineering student Zaaid Shah has researched solutions for the flood-prone Taieri Plans.

The Taieri Plains are so low-lying that part is actually below sea level. Periodically the Taieri River, fed also  by the Silverstream and Waipori rivers, will flood its banks. Compounding this problem is projected sea level rise. As soon as 2100 it's likely that there will be a tidal saltwater lagoon on the Taieri, where there once was one about 2500 years ago.

Zaaid considered many possible solutions that could form part of a flood management system, looking at how they had been used internationally. He identified those which had the best potential for the Taieri river catchment, then he ran simulations for those options, to see how they would perform. He used data from the flood event in July 2017, except for Waipori where he had to use approximations. 

As a result of his analysis Zaaid recommends a flood management system for the Taieri Plains that incorporates the following:

  • A new dam at the bottom of the Taieri Gorge, above Outram Glen, using a reservoir to store water in the Taieri Gorge. This would enable the flow to the Taieri Plains to be controlled to a maximum of 50 cumecs.
  • Improving use of the existing ponding areas by creating diversion channels into these areas and equalising the height of the bunds to maximise their capacity.
  • Using Lakes Waihola and Waipori as natural reservoirs.

Zaaid also considered construction of a tidal gate in the lower Taieri River, between Henley and Taieri Mouth, but this is not required at the current sea level.  

March 2018

Image credit: "Mr Thinktank", used under Creative Commons licence Attribution 2.0 Generic (CC BY 2.0)