Identification of Areas Damaged by Localized Heavy Rain using Satellite Data and Aerial Color Photographs

Abstract

In 1993 the localized heavy rain attacked Kagoshima City as well as neighboring towns and caused severe damage. Many areas suffered from landslides. As a result, a great number of farmlands and roads were covered with debris flow. To take effective measures to protect farmlands from natural disasters, it is considered to be important to assess the degrees of damage accurately and effectively.
Satellite has been used to monitor a wide area. In this study, therefore, the remote sensing techniques was applied to evaluate its practical use. The data observed on Aug. 12, 1993 by a satellite were used since it was known that stricken areas were scattered widely and that many small landslides occurred here and there on the day.
Aerial photographs taken on the same day were also analyzed at the same time. Usually aerial photographs have been visually examined by human eyes. However this demands technical skill and exertion. Therefore some techniques of image analysis were attempted to identify the stricken areas accurately and speedly. The relation between the difference of Shirasu and Andesite, and the incident of a landslide was also studied.
The results of the analyses based on the satellite data and aerial photographs were compared and practical problems in the analyses were evaluated.