Drivers are being warned not to stop on State Highway 46, near Mt Tongariro, due to a build up of debris in streams flowing from the mountain's recent eruption.
Taupo District Council civil defence coordinator Phil Parker said motorists would have about 15 minutes to get clear if the "significant volume of water", which had built up in streams blocked by boulders from the eruption two weeks ago, collapsed.
Warning signs were in place along the highway reminding drivers not to stop, Parker said.
A culvert on the highway would carry the majority of any debris flow if the main debris dam collapsed.
The area was being monitored "extremely closely" by NZ Transport Agency and Massey University.
"Further work is planned to improve understanding of the debris dams and how far material might go if the largest one collapses."
Any debris flow was not expected to affect buildings, but could affect SH46 within about 15 minutes of a collapse, Parker said.
"We will review our advice – and what we plan to do - once we have the results of further analysis."
Civil Defence, Conservation Department and GNS Science had released a revised map of the summit hazard zone since the eruption near Te Maari craters on August 6.
A 3km summit hazard zone was now smaller than before and was focused around the eruption area at Te Maari.
It is considered unlikely there would be more eruptions from existing or new vents, GNS Science said.
- © Fairfax NZ News
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