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A scientist who drowned in a rain-swollen stream on the slopes below Egmont National Park on Tuesday was warned of the risks before starting her tramp, Department of Conservation staff say.

Diane May Campbell-Hunt, 56, a Dunedin ecologist and botanist, drowned while crossing the Kaupokonui Stream with her 17-year-old daughter.

Mrs Campbell-Hunt was carrying a heavy pack when the stream became a raging torrent and swept her away.

Her daughter called for help on a cellphone, and told police they had been crossing the stream in waist-deep water.

As her cellphone battery failed, police urged the teen to stay put to wait for search teams.

Mrs Campbell-Hunt's body was found about 500m downstream.

DOC staff at Dawson Falls said they had warned the pair of the risk when there was heavy rain and had advised them of an escape route down the Auroa Track from Lake Dive should the streams rise.

DOC visitor centre ranger Joy McLean-Apps, said the mother and daughter had signed the intentions book and were told the streams were dangerous when there was heavy rain.

But when the pair left on Monday for Lake Dive Hut, the storm that hit at 2am on Tuesday had not been expected to arrive until 13 hours later.

"The front came in early," Mrs McLean-Apps said. "The information we had to give them is that it wouldn't start until 3pm."

She said it rained constantly from 2am: "The rivers are massive. It's a huge dumping of rain."

Mountain Safety Council bush programme manager Chris Tews said the incident was a "terrible reminder" to always be cautious when crossing rivers. It is always better to err on the side of caution and wait until conditions improve.

"Even experienced trampers can strike problems in the outdoors. Survival may then rely on your ability to wait it out until conditions improve."

Council staff recommended trampers attend a river safety course on when, where and how to cross safely.

Mrs Campbell-Hunt was the first person to die on Mt Taranaki in more than three years.

Search and rescue co-ordinator Sergeant Andrew Ross said the searchers themselves had faced extreme danger from flash flooding. "When you get a bit of rain up there the streams turn into raging torrents. A couple of the streams there are notorious."

Mrs Campbell-Hunt wrote a book on Wellington's Karori Wildlife Sanctuary, and in 2006 was awarded a Top Achiever Doctoral Scholarship to study at Otago University's geography faculty.

Her thesis subject was wildlife sanctuaries in New Zealand.

Karori's chief executive, Nancy McIntosh-Ward, said Mrs Campbell-Hunt had spent much of the past six months interviewing people associated with the sanctuary, including board members, managers and research workers.

"A lot of us are quite shocked by her death."