He said there have also been some sewage and wastewater discharges in the city area and he warned surfers and swimmers not to head out.
"All rivers in the district were up to alert level and threatened to flood over roads but did not quite do so. The whole area is saturated with a number of slips and slumps. Surface flooding will continue for a few days so extreme caution is required on the roads," Mr Davies said.
Acting Civil Defence manager Paul Stuart said nine rural roads were closed by slips and surface flooding and more could be closed if the rain continued.
Mr Davies said although rain had eased in Gisborne city, it was still falling steadily in some regions and at least 12 more hours of rain were expected across the Gisborne district, with a further 50mm in the ranges and 30mm in coastal areas and the city.
He said despite the rain, river levels have started to go down and the worst was over.
In Hawkes Bay, a slip caused by heavy rain closed State Highway 2 between Napier and Wairoa yesterday morning. It reopened around midday.
Heavy sea swells up to seven metres were likely to cause damage at Haumoana and Clifton, the council said.
Up to 250mm of rain could fall in the hills and ranges of Hawkes Bay north of Napier, and up to 120mm in low-lying coastal areas until today, MetService said. South of Napier, up to 150mm could fall in the ranges and up to 80mm in lower-lying areas to midday today.
MetService also warned that severe gales were expected in the Bay of Plenty, Taupo and Taihape, while strong winds were also possible in Taranaki, Whanganui, Manawatu and the Kapiti Coast.
- NZ HERALD STAFF/NZPA