Abstract
In consequence of statistical study on landslides which took place on the upper reach of Tenryu river caused by heavy rain of June 1961, the total area of landslides in a drainage basin increases as a sigmoid curve but the mean area of landslides doesn't expand accompanied with increase of precipitation, was found. Therefore it could be concluded that increase of total area of landslides in a drainage basin is performed by increase of number of landslides but not by expands of area of each landslides.
