Wairarapa and Wai-iti Streams

The Christchurch earthquake series caused widespread land damage across Christchurch City, including damage to the city’s waterways. Impacts on the city’s waterways included bed heave, settlement, liquefaction, and lateral spread of banks.

PDP completed a detailed drainage and ecological assessment for the Wairarapa and Wai-iti streams for both pre-earthquake and post-earthquake conditions. The assessment was based around the Christchurch City Council’s six-values values approach (drainage, ecological, cultural, landscape, recreational and heritage) to waterway management.


Wairarapa Stream in Mona Vale Gardens

Comparisons between pre-earthquake and post-earthquake conditions were made with the objective of identification of areas where any of the six values has been adversely impacted by earthquake activity. This included hydraulic modelling to assess the divergence in conveyance capacity of the streams pre- and post-earthquake, along with recommendations on how to ensure the conveyance capacity was similar to pre-earthquake levels. This was done to fulfil the ultimate purpose of this project: to remediate these waterways to conditions where each of the six values is at least as it was prior to the earthquake activity, while also identifying areas where improvements beyond this could easily be made.