From right around that spot (Idaho/West Marginal), southward to SW Brandon, bicyclists, walkers and runners will have to detour off the Duwamish Trail next week – according to this announcement from SDOT:

The Seattle Department of Transportation is repairing the Duwamish Trail where sections have been damaged by tree roots and general deterioration.

The trail will be closed between SW Idaho Street and SW Brandon Street from 7 a.m. to 3:30 p.m. on Monday and Tuesday, August 3 and 4, and may be closed 24 hours a day on Wednesday through Friday, August 5 to 7, if it cannot be made safe for trail users after work hours.

Bicyclists and pedestrians will be detoured onto West Marginal Way SW. Advanced warning signs have been provided along with a notification board at the ends of the trail.