The popular cycling and walking path will be closed between Station Road, Sandford and Woodbrough Road, Winscombe from Monday 19 October.
Part of Winscombe Millennium Green will also be closed during the works. No public rights of way that cross the Strawberry Line will be affected by the work.
Cllr James Tonkin, North Somerset Council's executive member whose portfolio includes transport, said: "A new retaining wall is needed to stabilise the collapsed embankment on the Strawberry Line near Ilex Lane.
This will help protect this route which is important to the many thousands of people who visit it annually. It will also help protect the houses whose gardens back on to the line from Broadleaze Way."
The retaining wall will support a 36m long and 2m high section of slope and will be constructed using a king post technique. This is where steel beams are set vertically in concreate and precast concrete panels are slotted in between the beams and the area behind is back filled with aggregate and soil.
The works will be carried out by local firm EJ McGrath Construction Limited at a cost of £118,300.
Diversion signs will be in place during the closure. Local volunteer rangers from Sustrans will be signposting the diversion route for cyclists and pedestrians.