FLOODING 

Flooding is the most frequent hazard for the Gisborne/Tairāwhiti region. At least one severe storm causing flooding can be expected in any year. Events that cause significant flood impacts are less frequent but when they do can have big impact when they occur. The frequent but relatively minor events will not typically have any impact on houses but will result in damage to crops, farm fences and the roading network. Flooding of low-lying parts of the road network disrupt traffic and washouts and dropouts can occur. 

The earliest recorded significant flood event occurred in June 1894 when 172mm of rain caused widespread flooding across the region. Other historical comparable sized events occurred in 1897, 1900, 1901, 1910, 1916, 1917, 1924 and 1933. A significant flood event in February 1938 resulted in the Kouawhara disaster (https://teara.govt.nz/en/floods/page-3) and the Esk Valley flood in April 1938 also impacted the region.

The period between 1939 and 1954 was a quiet period with no significant floods reported while moderate flooding occurred in April 1955. There was again little flooding of significance between 1955 and 1977. A state of emergency was declared on June 22, 1977, after 156mm of rain fell at Gisborne Airport on the previous day and 218mm of rain over the period June 20-22. Inland the rainfall was far higher with 444mm reported at Glenroy Station. The event hit Gisborne city badly with Wainui Road impassable and 15 houses evacuated on Fergusson Drive. Houses along Crawford Road also flooded. Link to reports.

The Waipaoa and Waimata flooded again during storms in June 1984 and July 1985, with the latter slightly smaller than the June 1977 storm with the flood height at Goodwins Road bridge reaching 11.24m compared to 11.7m in 1977. Link to reports.

Cyclone Bola which occurred between March 7-9, 1988, is the biggest event most people recall before Cyclone Gabrielle in 2023. Total rainfall accumulations of c.900mm occurred at the Tauwhareparae and 400mm in the upper Waipaoa. The cyclone resulted in significant damage in the Poverty Bay and Uawa areas. The Waipaoa stopbanks were breached upstream of the railway bridge with around 20 hectares of land inundated and leaving the righthand abutment of the railway bridge stranded mid river. The Waipaoa stopbanks also overtopped at Mullooly Road, at Waituhi, Ford Road, Mahunga and at Smiths bend on Eades Road, Patutahi.

The period between 1988 and 2004 was a quiet period with no significant floods but a rather nasty storm over Labour Weekend in October 2005 did cause severe flooding across the region. The Hikuwai peaked at 13.9m and the Waipaoa at 10.8m which is within 0.5m of the peak floods in Cyclone Bola. Flooding was prevalent in Poverty Bay where 2000 hectares of farmland was damaged by silt and debris and a further 1000 hectares was similarly damaged in Uawa. No state of emergency was declared but seven houses around Tolaga Bay were flooded as was the marae at Mangatuna.

A further quiet period occurred between the 2005 flood and Cyclone Pam in 2015.

Hikuwai River timelapse December 2022. Credit GDC