Delays can be expected for two weeks around County Hall in Norwich as Bracondale closes from today.
Motorists will have to avoid Bracondale between the County Hall roundabout and the King Street turn off - leading to Riverside - from 9.30am this morning to September 3.
The closure is part of a city council scheme to replace gullies in that part of the city to help with flooding issues.
The council has recommended using Ipswich Road and the A146 around through Lakenham Road, Barrett Road and Martineau Road as a diversion.
If the work is not finished by August 25, the road will be reopened for Bank Holiday Weekend and will resume the following Tuesday.
A council spokesman said the road would stay open in the outbound direction, and buses and emergency vehicles would not be affected by the closure.
The spokesman said: 'The work is being carried out to the most robust spec possible to minimise the need for future maintenance.'
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