1999 Volume 52 Issue 2 Pages 14-20
Natural revegetation in slope failure sites in University Forest in Chiba, The University of Tokyo, where more than 700 slope failures occurred in July 1970, was investigated using aerial photography. Four research areas were chosen to analyze the 25-year trend in vegetation. Aerial photographs of each research site taken in 1966, 1971, 1976, 1984 and 1995 were overlaid to prepare an orthophotograph and matching scale using graphic software (Adobe Photoshop). The following results were obtained. 1) There is a good correlation between the initial area of slope failure and the length of elapsed time until a denuded slope is completely covered by vegetation. 2) An approximately 150 square meter slope failure became indistinguishable after ten years, and a 1500 square meter failure became indistinguishable after 20 years. 3) Long and narrow slope failures recover faster than other shapes. Even though slopes have been completely covered by vegetation in aerial photography, slopes with failures can still be identified by ground truth data because of shallow soil and old scars.
