This proceedings, ""Risk-Based Decision Making in Water Resources V"", contains edited papers presented at the Fifth Engineering Foundation Conference held in Santa Barbara, California on November 3-8, 1991. During the Conference there was a growing sense of the need for a stronger theoretical and methodological foundation to deal with risk of extreme and catastrophic events. Emerging issues such as the possibility of global climate change, the safety of dams under extreme hydrologic conditions, the protection of lives and properties from catastrophic natural hazards, the protection of our groundwater and surface water resources from major contamination by toxic and hazardous materials, and the nationwide state of deterioration of our water resources and other public works infrastructure linger and call for more, concerted effort in addressing them.