Fish Passage for Upper Harbour Highway
CLIENT: New Zealand Transport Agency
DATE: 2008 - ongoing
The new Upper Harbour Motorway forms the northern part of the 48-kilometre Auckland Western Ring Route and will cross a number of streams along its length. Bioresearches worked closely with the engineering and construction teams on this project to guide the design of culverts that will allow native fish to pass on their annual migration to the sea. This initially involved a survey of the fish species present in these streams in order to target design features to their particular swimming abilities.
Fish-friendly culvert design was achieved using a number of measures including placement of baffles inside the culverts that have been shown to be effective in reducing water velocity, allowing resting areas and recreating habitat for native fish species such as inanga, eels and banded kokopu. In steeper sections of the catchments, a series of rock weirs have been used to create stepped pools for migratory fish to pass. Stream sections upstream and downstream of culverts have been recreated with a variety of instream habitat types and extensive plantings that will establish a natural-looking shaded stream over time. In some places these measures replace older style hanging culverts that formed barriers to migrating fish within these streams.
We worked with: