The
Lake Taupo Erosion Study report identifies nine areas at high risk of erosion - including Taupo township - and suggests measures to counter the problem.
The study, commissioned by Taupo District Council and Environment Waikato, found no homes were at immediate risk of erosion but said council reserves along the foreshore were threatened.
Early costings for combinations of the measures in two high-risk areas run into hundreds of thousands of dollars each.
The report recommends "soft" structural options such as beach replenishment and revegetation, combined with monitoring of erosion.
These methods were favoured over seawalls, breakwaters and groynes because they would maintain the existing natural character of the beaches.
However, the report acknowledged that beach replenishment alone would not halt shoreline erosion.
Altering lake-level flows from rivers and restricting shoreline development were further methods suggested to counter erosion.
The report said that historically, responses to erosion at Lake Taupo had been reactive, with a large number of seawalls and groynes installed.
The report provides initial costings for managing erosion in the high-risk areas of Kuratau and Whareroa, but the councils warned that the costings were only estimates, saying further site-specific investigation and community consultation were required to determine the true cost of each option.
No costings were provided for erosion control in Taupo township.
However, the initial estimate for Kuratau, which has experienced the highest level of erosion on the lake, runs to almost $1.5 million.
A combination of rock walls, beach replenishment, revegetation and offshore reefs was suggested to protect its 300m foreshore.
Environment Waikato Taupo representative, Laurie Burdett, acknowledged some of the options were costly, but said it was up to the community to decide which were acceptable. She said Taupo was comparatively lucky in that most of the erosion affected reserves rather than residential areas.
"We've got time now to plan a sustainable solution," she said.
The regional council's project manager, Adam Munro, said it was not possible to control erosion completely.
"We've got to bear in mind that erosion is a natural process and it's really only a problem when it interacts with humans and development."
But the study had given the councils a better understanding of the causes of erosion at the various locations around the lake, Mr Munro said.
It had also shown the importance of monitoring to determine erosion rates.
More monitoring, including beach profiling, water-depth measurements and sediment sampling would allow examination of daily, weekly, yearly and longer cycles of erosion.
The study began in late 2005 and was carried out by Beca Infrastructure for the councils.
The technical findings and a similar flood hazard study due for release at the end of the month will go out to public consultation in April and May.
The feedback from the community and stakeholders, including iwi, will then be used to develop a Lake Taupo Erosion and Flood Strategy, due for completion by year's end.
The strategy will guide future erosion-management decisions, set out funding responsibilities and identify work programmes and timeframes.
