| A deep catastrophic landslide occurred at the upstream of the Way Ela river, Ambon, Maluku, Indonesia in July 2012. Its sediment blocked river channels, and formed a natural dam. And there is a village downstream where about 5 thousand people live. They suffer serious damages in the case that the natural dam overflows and debris flow occurs. In order to minimize the damages, it is necessary to evacuate residents before breaches, and it is important to predict the water level of the dammed-up lake of the natural dam. The amount of rainfall up to overflow was estimated based on the water level using the daily rainfall data and the observation data of the Aerial Placeable Floating water stage gauge (the APF gauge) installed at the lake. In addition, we collected the past rainfall data in the region and organized the records of occurrence of rainfall in 1-day and 3-day period so that it can be used for countermeasures such as warning, evacuation, etc.Keywords: natural dam, debris flow, monitoring, APF gauge, Way Ela river |
