Civil Defence is on high alert on the East Coast after nearly 24 hours of rain.

Tolaga Bay Holiday Park Manager Mike Brooker says it has been steady and heavy since about eight o'clock last night.

He says there is about 20 centimetres of surface water and the stream running near the camping ground is over-flowing.

Mr Brooker says they have about four guests in cabins, luckily no one is out in a tent.

Meanwhile, a dozen houses in Mangatuna will have to be evacuated should the river levels rise any higher and a number of roads have been closed.