The 21 February 2005, catastrophic waste avalanche at Leuwigajah dumpsite, Bandung, Indonesia

Background On 21 February 2005 the Leuwigajah dumpsite, Bandung (Java, Indonesia) was affected by a large slide after heavy rainfalls. Second deadliest waste slide in history, it buried 71 houses and killed 143 people. Amongst the contemporary disastrous events of this type, only a few have been documented. We explored failure preconditions, triggering mechanisms and local context that conducted to this disaster. We carried on four field investigations on the site. A series of aerial photographs were acquired and completed by topographical measures on the ground. The morphology of the slide and its trajectory were reconstructed. To constrain the movement condition, we studied the internal structure of the source area and realized surveys among stakeholders of the dumpsite and citizen. Results 2.7 × 10 6 m 3 of waste materials spread 1000 m from the source in a rice field with an average thickness of 10 m. The material displays a preferential fabric parallel to the previous topography. Numerous internal slip surfaces, underlined by plastic bags explain the low friction coefficient. The presence of methane within the waste dump was responsible for explosions prior to sliding and for the fire that affects whole sliding mass. Conclusions Resulting of a combination of heavy rainfall and consecutive explosions due to biogas sudden release, this disaster was predictable in reason of i) a front slope of the dump of about 100% before the failure; ii) a poor dumpsite management; iii) the extreme vulnerability of the marginalized scavengers living at risk at the foot of the instable dump.