Nappies, formula and pizza have been ferried to stranded trampers and families - including a family with a newborn - after a major slip on the Kapiti Coast.

About 1000cu m of earth came down on Otaki Gorge Road yesterday morning, Senior Kapiti Coast District Council roading engineer John Perkins said.

"We've brought food in, we've brought nappies in for the baby that was on the other side.''

Contractors had taken baby formula, pizza and other necessary items to those cut off by the slip, Mr Perkins said.

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The Department of Conservation had a helicopter on standby if there were any problems with the newborn overnight.

The slip happened at Devil's Elbow, about 11km from the highway.

"All going well it will be cleared at the end of today, but there's no guarantee on that,'' Mr Perkins said.

About 400cu m had so far been cleared, Mr Perkins said.

Kapiti Coast District Council spokesman Roger Foley said the slip had cut off "a handful of houses'' and would strand trampers coming out from a weekend in the Tararua Ranges.