Ask the residents of San Jose’s drying-out Rock Springs neighborhood and other nearby areas if it pays to ignore warnings about future disasters that seem in normal times to be nothing more than distant, negative fantasies. During the heavy rains of February, when a crisis caused by a poorly-built spillway at the Oroville Dam drew worldwide headlines, the San Jose neighborhood and areas around it suffered at least $50 million of avoidable damage to private property and about $23 million in public property damage. Some estimates of the total toll come to more than $100 million.