Sheriff's Capt. John Robertson said a man found the body on the river embankment at the rear of his property in the 3100 block of Silverado Trail around 11:30 a.m.
The death is regarded as suspicious but there are no signs of foul play, Robertson said. The man had identification near him and is believed to have been a transient resident of Napa County, Robertson said.
The man, believed to be in his 40s, has been dead at least a week and an autopsy is scheduled for Monday, Robertson said. The Napa County Sheriff's Department also is investigating the death, Robertson said.