The Waiari stream runs from South to North in East Waitara, with its headwaters south of SH3, in farmland.
The two main tributaries run through culverts under the highway and join downstream, forming the Waiari Stream. From there, the stream runs through urban areas, farmland and the Waitara Golf Course, until it reaches its outlet into the Waitara River.
The Waiari and Tangaroa catchments form the Waitara East catchment. Some interfaces between the two catchments make it advisable to undertake the Waiari, after the Tangaroa project.
The Waiari is an awa of great significance for tangata whenua. As per the NPDC Proposed District Plan, there are nine wāhi tapu sites within the Waiari catchment, one of them within the stream bed.
Puke Ariki Collection. This paepae was found on the edge of a farm drain in Easter 1959, at Richmond Street, Waitara. Found at a depth of nearly 2m although a certain amount of post-European infilling had taken place in the area.
Digging sticks (ko) were also found near the paepae. For a more detailed description see publication 'Records of the Canterbury Museum Vol. VII No. IV.
Courtesy of Manukorihi hapū.
The two legs of the stream pass through undersized culverts at SH3. These culverts detain water upstream of the highway, resulting in flooding issues in Rahiri, Aratapu and Tuiti streets, as well as Hamua, Tawake and Uenuku places. Habitable floors are at risk of flooding and significant overland flowpaths produce safety concerns, especially around the Princess Street/SH3 intersection.
In the urban area between SH3 and the farmland, there are also a number of flooding challenges caused by undersized infrastructure, inappropriately located houses and lack of appropriate overland flow-paths.
The lower reaches of the stream lie behind the Waitara River stop bank. This means that when the Waitara River is in flood, the water in the Waiari Stream cannot enter the river, resulting in flooding of the houses in this area. This has occurred as historic urban development didn’t acknowledge that it was originally a flood plain and swamp.
There are significant residential growth areas within the catchment, with potential to worsen the existing flooding risk if adequate stormwater management is not in place.
Farming and urban development are the main activities that have shaped the Waiari in modern times and contributed to its deterioration. Those have resulted in loss of habitat for native species and the ability of the awa to buffer the effects of runoff contaminants and improve water quality, as significant sections of the stream have been piped or channelled. Often the channel appears drastically narrowed and encroached.
Tangata whenua have lost their connection to the awa, due to its poor ecological health and the fact that it runs predominantly through private land. There is little opportunity for the creation of public amenity, such as walkways.
There are numerous barriers for migrating native fish, with no native species found in the upper Waiari (upstream of the SH3 culverts). This reveals that SH3 is a barrier even for fish species that climb. In the lower reaches of the stream, several native fish were identified in 2021 survey, including banded kōkopu, giant kōkopu, inanga, tuna and redfin bully.
The Waka Kotahi project SH3 Waitara to Bell Block route improvements – Princess Street Roundabout presented an opportunity to divert flows from the upper Waiari catchment into the Waitara River, via a diversion stormwater pipeline. This would alleviate flood issues both in the upper and lower Waiari catchments.
The upper Waiari project enables NPDC and mana whenua to collaborate with Waka Kotahi for better outcomes for the community. The first stage of the project is the construction of a new stormwater pipe down SH3. This pipe will take the stormwater from the new Princess Street roundabout and flood flows from the upper Waiari catchment. NPDC will share the cost of this pipeline with Waka Kotahi and the asset will be maintained by Waka Kotahi.
In upcoming phases, NPDC will build a new pipe along Rahiri Street and upgrade other parts of the local stormwater network. These pipes will allow low flows to remain in the natural channel while diverting high flows to the new pipe down SH3. This will cultural and ecological values in the awa while reducing flood risk to properties, both upstream and downstream of SH3.
The project will look at mitigation of the fish barriers in this area of the catchment as well as opportunities to collaborate with landowners to improve the ecological health of the waterways.
The construction of the first phase (SH3 pipe) began in January 2022 and is expected to be finished in 2023.
The Rahiri Street pipeline and additional upgrades will be constructed between 2024 and 2027. These are currently in the engineering design and consultation stages.
This project will be funded from the Waitara Stormwater Programme budget.
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Page last updated: 12:47AM Mon 19 September 2022