Risk-Based Decision Making in Water Resources X are the Proceedings of the Tenth United Engineering Foundation Conference. The Proceedings were influenced by the terrorist attacks on the U.S. on September 11, 2001; the theme of this conference was Risk of Terrorism. Thirteen papers are included, which discuss risk and vulnerabilities of terrorism of homeland water resources system of systems; methodological perspectives of risk of extreme events; interconnectedness and interdependencies between the water resource system of systems and other infrastructures; institutional and organizational structuring associated with risks of terrorism. The conference was held in Santa Barbara, CA on November 3-8, 2002 and sponsored by the United Engineering Foundation (UEF), Environmental and Water Resources Institute (EWRI) of the American Society of Civil Engineers (ASCE).