Residents between 92 and 135 Somme Pde can access their properties from London St via Russell St, Spier St or Kaikokopu Rd.
Aramoho Shopping Centre will still be open through the one-way system from Somme Pde and from the centre’s Kaikokopu Rd entrance.
The riverbank, opposite 131 Somme Pde, began caving in during Cyclone Dovi in February 2022.
Further dropouts followed, resulting in an increase in the amount of work needed for repairs.
In July, council transport manager Damien Wood said subsidence was affecting the Somme Pde footpath and berm but not the road itself, and repairs were proceeding with a “degree of haste” to prevent further damage.
Initial work began to repair the dropout on June 26.
The traffic detours will be in place until the end of December.
Eva de Jong is a reporter for the Whanganui Chronicle covering health stories and general news. She began as a reporter in 2023.