Landslide Dams Formed by the 2004 Mid-Niigata Prefecture Earthquake in Japan

Abstract

It was a remarkable aspect that a tremendous number of landslides were triggered by the Mid-Niigata Prefecture Earthqauke. Because the epicenter was located at a depth of 13 km just in the landslide prone area of central part of the Niigata Prefecture, severe damage was caused by the earthqauke-induced landslides. Furtehermore many landslide dams were formed mainly in the watershed of the Imogawa-River by the displaced soil mass of the earthquake-induced landlslides. Some large landslide dams should pose a great threat of flood and debris flow in case of dam collapse to the settlemnt of the Ryuko-District in the downstream area of the watershed. It was urgently needed to arrange the emergency operations to avoid the destructive collapse of the major landslide dams. This contribution illustrates overview of landslide dams and emergency operations against dam collapse.