A trio of spillway failures at the 770-ft-tall earthfill Oroville Dam that prompted the evacuation of more than 188,000 people from central California has renewed questions about the reliability of hundreds of dams in the state and more nationally.

Situated in narrow valleys, arch dams are not as common as other types of dams, such as embankment dams and gravity dams. 

After more than 188,000 people evacuated from central California towns north of Sacramento, crews at Oroville Dam on Feb. 13 scrambled to fill erosion that developed hours after an emergency spillway was put into service for the first time in the dam’s 50-year history.