Tsunami vulnerability of buildings and people in South Java – field observations after the July 2006 Java tsunami

A team of scientists from New Zealand and Indonesia undertook a reconnaissance mission to the South Java area affected by the tsunami of 17 July 2006. The team used GPS-based surveying equipment to measure ground profiles and inundation depths along 17 transects across affected areas near the port city of Cilacap and the resort town of Pangandaran. The purpose of the work was to acquire data for calibration of models used to estimate tsunami inundations, casualty rates and damage levels. Additional information was gathered from interviews with eyewitnesses. The degree of damage observed was diverse, being primarily dependant on water depth and the building construction type. Water depths were typically 2 to 4 m where housing was seriously damaged. Damage levels ranged from total for older brick houses, to about 50% for newer buildings with rudimentary reinforced-concrete beams and columns, to 5– 20% for engineered residential houses and multi-storey hotels with heavier RC columns. “Punchout” of weak brick walls was widespread. Despite various natural warning signs very few people were alerted to the impending tsunami. Hence, the death toll was significant, with average death and injury rates both being about 10% of the people exposed, for water depths of about 3 m.