WHY WAS THE AUGUST 2010 ZHOUQU LANDSLIDE SO POWERFUL?

Abstract

On August 8, 2010 in the northwestern Chinese province of Gansu, rainstorm-triggered debris flow devastated the small county of Zhouqu. A modeling study, using a new multiple-phase scalable and extensible geo-fluid model, suggests that the cause is the result of an intersection of several events. These were a heavy rainstorm, not necessarily the result of global warming, which triggered the landslide and followed a drought that created surface cracks and crevasses; the geology of the region, notably the loess covering heavily weathered surface rock; and the bedrock damage, which deepened the surface crevasses, inflicted by the 7.9 magnitude Wenchuan earthquake of May 12, 2008. Deforestation and topsoil erosion also contribute. The modeling results underscore the urgency for a high priority program of re-vegetation of Zhouqu county, without which the region will remain exposed to future disastrous, “progressive bulking” type landslides.

Keywords

• progressive bulking, graded sloping, extreme precipitation, vegetation effects on storm-triggered landslides