The Wairoa River of the Hawke's Bay region in New Zealand runs south for 65 kilometres from the inland east coast region of the North Island, west of Gisborne, before flowing into northern Hawke Bay at the town of Wairoa.
The full Māori name of the river is Te Wairoa Hōpūpū Hōnengenenge Mātangi Rau, which means the long, bubbling, swirling, uneven waters.[1] The Wairoa River and its tributaries are vital for mahinga kai and hold high cultural value for Māori iwi and hapū of Te Rohe o Te Wairoa, many of whom report an overwhelming sense of spiritual connection when they are at the river.[2]
The Hangaroa River and the Ruakituri River merge at Te Reinga Falls, near Te Reinga. This is where the Wairoa River begins.
Lake Waikaremoana is formed in the rockfall-dammed headwaters of the Waikaretaheke River. It has a confluence with the Waiau River 14 miles from the coast.[3]
Wairoa River Valley between Te Reinga and Frasertown
Sediment and erosion
The Wairoa River carries large quantities of fine sediment (clays, silts and sands) that cloaks both the bed and the banks of the river. The rate of sediment loss has increased because of changes in land use from native forest to pasture, and forestry and farming land use practices, with current sediment losses estimated to be approximately 240% higher than before human arrival.[4]
In 2023, an assessment of the lower Wairoa River, downstream of Marumaru, suggested that the river had a gravel (or bedrock) bed down to Awamate until about 3000 years ago.[5] It remains unclear whether it was gravel-bed before widespread land cover change around 100 years ago. The lower river (downstream of Awamate) is most likely naturally soft-bottomed.
Extreme weather events
In 1948 a big flood of the Wairoa River submerged the traffic bridge in Wairoa and flooded parts of the town to a depth of 3 feet (0.91 m). This flood flow is one of the largest recorded for any river in New Zealand.[3] The river rose to a "record height", the bridge "took a battering", and "telephone lines 4.3 metres above road level were carrying grass and twigs, showing the phenomenal rise of the floodwaters".[6]
Cyclone Gabrielle resulted in erosion of stream banks, removal of riparian vegetation, and stream-bed disturbance in Wairoa River. A 2023 study estimated that erosion control measures on land could reduce sediment loads in the river by up to 60%, improving visual clarity and creating better conditions for sensitive fish species.[7] However, this would result in significant economic impacts, including reduction in farm revenue and employment.[8]
Walkway
In 2010, the Wairoa Township River Walkway project commenced. The Walkway is a pedestrian and cycle path starting at the bridge on the south bank of the Wairoa River. It is planned that it will eventually completely encircle the town.[9]
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