The Waipaoa River is in the Gisborne District, in the northeast of New Zealand's North Island. It rises on the eastern slopes of the Raukà «mara Range, flowing south for to reach Poverty Bay and the Pacific Ocean just south of Gisborne. For about half of this distance, its valley is followed by State Highway 2. The river has several important tributaries, among them the Wharekà Âpae, Waikohu, Mangatà «, Te ÃÂrai, Waingaromia and Waihora rivers. Major settlements along the banks of the river include Te Karaka, Ormond, and PÃÂtà «tahi. Waipaoa is MÃÂori for "PÃÂoa's river", PÃÂoa being the captain of the Horouta canoe (hence "Waipaoa River" is tautological).
The river has formed the fertile and highly productive Poverty Bay flats on the edge of Gisborne. The Waipaoa River Flood Control Scheme was built in the 1950s. Stopbanks are to be raised by 2031, as eroded soil, especially from the Waingaromia and Mangatà « catchments, has built up the river bed, the annual flow of sediment being 15 million tonnes. Despite this pollution, many of the headwaters have indigenous fish.
In the lower river, water quality is poor for E. coli, clarity, turbidity, ammoniacal nitrogen and total phosphorus. The sediment, building up at a rate of several centimetres a year even many kilometres into Poverty Bay, shows that removal of tall trees such as rimu, mataë, beeches and kahikatea and subsequent conversion of forests to farmland by the early 20th century increased sediment flows by 2 to 3 times the former rate.