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In February 2001, widespread flooding occurred throughout the Atacama Desert of northern Chile and southern Peru. It was particularly severe in the Rio Loa basin, where roads and bridges were disrupted and the town of Calama inundated. The instantaneous peak flow in the Rio Salado, a tributary of the Rio Loa, reached 310 m(3) s(-1), an order of magnitude higher than any previously recorded event. The flood is estimated to have a return period of 100-200 years and is shown to have been caused by intense, long-duration rainfall in the western Cordillera associated with La Nina. The surface water response is typical of and areas and highly dependent on antecedent conditions, but is quite different in perennial and ephemeral catchments. Ephemeral flood flows suffer high transmission losses, recharging phreatic aquifers. Perennial rivers have lower runoff coefficients, but baseflow levels remained high after the event for several months due to bank storage rebound and interflow. Extremely high energies of similar to 3000 W m(-2) were generated by the floods in the Cordillera, becoming less in the Precordillera and downstream. Erosion and sediment transport were consequently highest in the upper and middle reaches of the rivers, with mixed erosion-deposition in the lowest reach. The new insights gained from the interpretation and quantification of this event have important implications for palaeoenvironmental analysis, hazard management, water resource evaluation and the palaeohydrological evolution of the Andes. Copyright (c) 2005 John Wiley & Sons, Ltd.