More Hauraki residents could be forced to flee their homes as flooding moves down the Piako River.

Water already surrounds some houses after the river breached stop banks near Ngatea.

Waikato Regional Council says the flood schemes are designed to overflow in designated zones - and evacuees were given a heads up earlier in the week.

Hazards team leader Rick Liefting said people should pack up and get out if they feel unsafe.

"This flood peak that we're seeing is forecast to move further down the system into some more ponding zones - there may be the need for some people to self-evacuate"

Mr Liefting also said water levels haven't been this high in around 30 years - but the flood scheme is designed to overflow in some spots and has been working "as designed".

"We have seen some pretty unprecedented water flow through there and we do have quite comprehensive flood protection schemes."

Mr Liefting is confident the flooding will be relatively contained.