OBSERVATION OF FORESHORE VARIATION IN IWO-JIMA

Toshiyuki Shigemura, Kenjiro Hayashi, Koji Fujima

Abstract


The variation of the foreshore in Iwo-jima is studied by analyzing a series of aerial photographs taken seasonally for the past 4 years since 1987, and data of various surveys obtained for the past 10 years since 1982. These observations are compared with results of numerical analysis of the effects of storm waves on the foreshore. The findings obtained through these analyses are: (l)The island is still rising at a yearly rate of more than 30 cm/year; (2)The foreshore is eroded in summer and fall when typhoons often hit the island, but is restored back in winter and spring of the following year. The seasonal variation of the foreshore area ranges from 300,000 m2 to 600,000 m2 depending on the magnitude and frequency of the typhoons hitting the island in a year; (3)The foreshore area is increasing at a rate of 50,000 m2/year which is caused by the upheaval of the island; (4)A one-line model can be applicable for the prediction of the short-term variation of the shoreline caused by storm waves.

Keywords


Iwo-Jima; foreshore variation

Full Text: PDF

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.