ABSTRACT
Lahars, defined as debris flows of volcanic origin, are rapid mass movements that pose a serious threat to urban areas located near volcanoes. Quito, capital city of Ecuador, is a classic example, as large portions of the city are built upon fans descending from the flanks of the Guagua Pichincha volcano. Numerous deposits of large lahars that have occurred in the last 10,000 years are present on the fans. Two numerical models adopting completely different approaches were applied to the Pichincha lahars in order to delineate potential lahar inundation areas on two large fans present within the city boundaries. The models were also compared in terms of accuracy and of operational characteristics. Fieldwork consisted in the collection of data from various fields including volcanology, meteorology, stratigraphy and engineering geology. Data processing was principally aimed at constructing the main characteristics of potential lahars.
