Natural and man-made causes for the “Elísio de Moura” earth flow in Coimbra, Portugal

The paper reports the 27 December 2000 landslide, which occurred in the city of Coimbra, central Portugal, affecting loose fill soils and slope debris derived from the red sandstone of Triassic age. With urban spread, the base of the hill slope on which farming had taken place over many centuries was terraced to provide residential properties; the excavated material was end-tipped at the top of the slope, modifying the slope gradient from the original 18° to 38°. The loose fill was placed without engineering precautions, directly on to the debris slope material. Following a small slip in 1998, remedial works were undertaken involving large diameter piles anchored into the bedrock. This engineering construction formed the back slope and restricted the extent of the December 2000 landslide, which occurred during a period of unusually heavy rainfall.