The worst case scenario
There is no map showing exactly what will happen if the emergency spillway collapses tonight. Officials only have a map showing a failure of the dam. That worst case scenario is useful in that it shows where water goes and how fast it gets there.
Water would get to the town of Oroville within an hour.
If Oroville Dam were to suffer a massive breach, water would get to the town of Oroville within an hour, according to GIS maps maintained by CalFire.
Within two hours, the small town of Briggs would be affected. In three hours, Gridley would be hit. Water would reach Live Oak in five hours..
It would take eight to 12 hours for the water to get to Marysville and Yuba City.
If the dam completely failed, flood depths could reach more than 100 feet in Oroville and up to 10 feet in Yuba City.
The CalFire maps represent a catastrophic breach and are not necessarily indicative of what could happen tonight.
Read more here: http://www.sacbee.com/news/state/california/water-and-drought/article132332499.html#storylink=cpy