Consenting issues are holding up repair work on the Anzac Parade slip near the City Bridge but work is still expected to begin in spring.
Floodwaters in June 2015 washed out a large section of the bank near the Portal St intersection with State Highway 4 bringing down the walkway and part of the road.
Design work has been completed and a contractor is ready to begin work but there have been consenting issues including work not being undertaken during the fish spawning seasons of March - June and August - November.
"The current issue the New Zealand Transport Agency [NZTA] is working through is being able to obtain a consent that will enable the work to happen quickly," a statement from Transport Minister Simon Bridges' office, in response to question from Whanganui MP Chester Borrows said.
"The river bed is significantly different to what NZTA found at other sites.
"The slip site has a high number of underground services, including water mains, which NZTA needs to work around."
Whanganui Mayor Hamish McDouall said the road was important and it needed to be sorted as soon as possible.
He feared what would happened if another washout in the same spot cut off SH4.
"It's too vital," he said.
"Imagine entering 2018. That'd be two and half years since the flood, and nothing.
"We don't want to enter another winter like that."
NZTA is currently providing more information for Horizons Regional Council to assess the consent application.
There were over 120 sites damaged as a result of the June 2015 storm event across both the Manawatu and Taranaki regions with an estimated total repair cost of $47 million.