The practically ungaugeable and damaging storms of the Atacama Desert, Chile

This study presents an analysis of the convective storms occurring in the Atacama Region of Chile, which produce damaging floods in populated areas. These convective storms are rarely recorded with gauges due to their spatially bounded character, challenging traditional measuring methods and approaches for their analysis. Precipitation data gained from the integrated multi-satellite retrievals for the global precipitation measurement mission through the product IMERGv07 are used to study precipitation properties, such as intensity, duration and frequency, as well as rainfall spatial distribution. Interviews with key informants were used to characterize the Atacama storms and corresponding floods and damage. Results show lower rainfall intensities than those commonly observed in, e.g., Mediterranean climate. Spatial variability of the rainfall properties is very high, with intensity–duration–frequency curves that can drastically change in distances of about 10 km. Frequent storm events, i.e., with return periods of around 2 years, can already activate ephemeral streams, trigger flash floods and cause damage to populated areas. Results from a study case in a small watershed (4.1 km2) served to demonstrate that very low infiltration rates due to the formation of a saline crust over the desert surface are responsible for the high runoff and corresponding floods affecting people. Rainfall analysis needs to consider information from the specific location of interest. Otherwise, errors in rainfall and streamflow estimations can arise, with important consequences for territorial planning and engineering design. Atacama storms motivate the development of special types of warning systems and the adoption of measures to prevent damage caused by floods.