The FAN model, developed by the Federal Emergency Management Agency (FEMA, 1990) was one of the earliest attempts to generate a mathematical model of alluvial fan flooding that incorporated the impact of channel avulsions on flood risk. The FAN model implements a methodology for delineating alluvial fan flooding hazards first proposed by Dawdy (1979), and later modified by FEMA based on recommendations made by DMA (1985).2 The FEMA FAN methodology has been criticized in the literature (McGinn, 1979; Burkham, 1988; French, 1987, 1992; Fuller, 1990; NRC, 1996) since its inception, but remains a key component of FEMA’s floodplain delineation guidelines for alluvial fans (2003). Reaction to the FEMA methodology by floodplain managers has been mixed.