As consequence of the Station fire (fig. 1), which burned 160,557 acres of the San Gabriel Mountains of southern California in August and September, 2009 (National Interagency Fire Center, 2009), postfire floods and debris flows now pose significant hazards to life and property (Cannon and others, 2009). Emergency-response and public-safety agencies are faced with making evacuation decisions and deploying staff and emergency-response equipment both well in advance of each coming winter storm and during actual storms themselves. In this report, we provide information that is critical to this process.