According to the sheriff's office, Webb fell and struck his head just a short distance from Triangle Lake, a location popular for cliff jumping and natural rock waterslides that is near Eugene, Oregon.
"So full of life in every moment of the day," Ducks coach Dan Lanning posted to Twitter on Wednesday night. "Your smile and energy will be missed Spencer. I love you!"
The sheriff's office said bystanders and responding paramedics were unable to revive Webb, who was about 100 yards down a steep trail, and Lane County Sheriff's Search and Rescue personnel assisted with bringing him back to the roadway.
Authorities said his death appeared to be accidental.
Webb, from Sacramento, was set to begin his fifth season at Oregon. He played in all 14 games last season, catching 13 passes for 87 yards and a touchdown. In 2019, he had 18 receptions for 208 yards and three TDs.
"We are deeply saddened to learn of the passing of Spencer Webb," said a statement issued Thursday by Oregon athletic director Rob Mullens and Lanning. "Our hearts go out to his family, teammates, and friends at such a difficult time. We will miss Spencer greatly."
Webb attended Christian Brothers High School and was the No. 1-ranked tight end in California.