At a council meeting yesterday, she said the agency didn't have as much money as it used to.
"There's a huge gap in funding.
"They are $300 million down in income from petrol tax and excise duty."
Emergency funding for roads that are damaged by storms or flood may also be cut significantly by the NZTA.
Over the past few years several million dollars has been spent on preventative maintenance such as the rock walls, gabion baskets and recently the concrete section over the blow hole.
Mark Allingham, the council's group manager infrastructure services, said NZTA would now decide on how much to contribute to work on a case-by-case basis rather than giving a set rate.
"We can apply for extra money which will be given to us at a 50 per cent or higher rate.
"Any emergency goes through a cost benefit analysis.
"It really depends on what money is in the coffers when we apply."
Councillor Viv Napier said it was a huge risk to council.
"I want to be kept very much up to date with how this is going and if we need to lobby to whoever."
The remainder of council's local roads cost $2,801,741 and is subsidised via the $1,389,511 from the NZTA.
Council would need an increase in its funding assistance rate from its current 49 per cent to 55.3 per cent to equal the loss of the special purpose road funding.
In the Greater Wellington Regional Council's original submission to NZTA about the review, which the three Wairarapa councils supported, it said an increase in rates of 1 per cent is equivalent to around $100,000 in South Wairarapa.
"Given that roading expenditure makes up a significant proportion of total expenditure in rural areas such as South Wairarapa, even a minor change in the funding assistance rate for these organisations will be significant."
The changes would take place in a year and a half and the 50 per cent rate would be phased in.
