Design flaws, construction shortcomings and maintenance errors caused the Oroville Dam spillway to break apart in February, according to an independent analysis by Robert Bea for the Center for Catastrophic Risk Management at UC Berkeley. Bea, a co-founder of the center and retired civil engineering professor, found that in the 1960s, when the dam was being planned, designers did not call for a thick enough concrete spillway floor. Nor did they require the continuous steel reinforcement needed to keep its slabs intact during decades of service.