kelsey thorton shows us a very important thing she did that saved her life. >> reporter: you can see the overturned truck out here behind me, stuck in these floodwaters, first responders say the driver of the truck balanced on top of it for close to 15 hours, much of which was in the pitch black darkness. just waiting and hoping for someone to find her and call for help. harrowing video shot from above a rescue helicopter shows the moment first responders listed a woman to safety, after she spent the entire night, trapped on top of her overturned truck. >> we could've had a whole different outcome and she could have been swept downstream but strong enough to get on top of the vehicle. >> reporter: the alameda county fire department says the woman underestimated the water depth when she tried to cross a flooded road in a remote area of the family campground in livermore around 7:30 monday night. the rushing water was so strong that it pushed her truck off the road and flipped it into a creek. >> maybe out of tenacity or like i don't know what it was, but the cab was submerged and she