Waikato Regional Council is monitoring high and rising Piako River levels.
Rainfall in the river's catchment in recent days has been similar to that seen in recent cyclones when there was surface flooding.
"The good news is that the river is unlikely to do any significant overtopping of stopbanks and cause more surface flooding in emergency ponding areas such as paddocks at this stage," said regional hazards team leader Rick Liefting.
There is potential for some "limited overtopping" and users, including duck shooters in the Kopuatai Peat Dome area, need to be aware the river's level is high and rising.
The catchment is very saturated and surface water from the latest rainfall will take time to drain away.
No more rain is forecast for several days.
The Piako River drains into the Firth of Thames. It is one of the two main rivers systems which drains the Hauraki Plains.