The accident was discovered shortly before 9 a.m. Monday when workers noticed a car down an embankment.
The driver, 78-year-old Peggy Conway Riley, was found inside the car and pronounced dead at the scene.
A Silver Alert had been issued for Riley on Sunday by the Orange County Sheriff's Office.
Investigators said the vehicle ran off the left side of the road, went down an embankment and landed in a creek.
Investigators are trying to determine when the accident occurred and what caused it.