The Portway and Bridge Valley Road will be closed for two days so a large boulder can be removed.
The closures will be in place from Saturday (October 19) to Sunday (October 20) so council workers can secure the boulder, which has fallen partway down the cliff face over the junction.
Bristol City Council says the boulder will be lowered safely while the area is surveyed to determine what further steps are required.
Further closures of Bridge Valley Road may be necessary to remove the boulder and clear the rock trap at the foot of the cliff.
Councillor Kye Dudd, cabinet member for transport at the council, said: “We apologise for the inconvenience caused by these road closures, as we know how frustrating it can be when your journey is disrupted.
“These works are absolutely necessary and must take place soon due to the position of the boulder, and the growing risk to motorists and pedestrians if it were left unattended as we head into winter.
Motorists are advised to check Travelwest’s Twitter account for updates and leave extra time for their journeys.
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