ランドサットTMデータによる沖縄島北部サンゴ礁の赤土分布評価

抄録

Since the 1960's, a huge quantity of red soil has been carried out to sea onto the coral reefs of the northern part of Okinawa Island, with this being due to development of agricultural land and housing sites. However, the distribution of this red soil has remained unknown. The purpose of this paper is to clarify the distribution of red soil which is sedime nted over the coral reefs at the periphery of Katabaru located on the eastern coast of the norther n part of Okinawa Island, by grasping the degree of contamination based on the relationship between the TM data and the amount of Fe₂O₃ contained in the red soil. These TM data were observed by LANDSAT on August 10, 1984 and April 15, 1988.
As a result, the facts stated below were revealed:
(1) There is a high correlation between the interchannel ratio of the TM data (the ratio of the CCT count of band 1 to the CCT count of band 3) and the amount of Fe₂0₃ contained in the red soil. Thus, the interchannel ratio is an effective index for analyzing the distrib ution of the sedimented red soil.
(2) The distribution of red soil was estimated using the interchannel ratio of the TM data. As a result, a remarkably large amount of red soil was found to be sedimented near the estuary, and other sedimented areas were recognized inside the reef crests and along the coast, as well
(3) The distribution area of red soil off the coast of Katabaru was almost identical both in 1984 and 1988. This is consistent with the fact that large-scale construction work, which involved major topographic alterations to the basins of rivers flowing into this area of coast, were concentrated in the period up to and including the early 1980's, and that there was only a small number of construction projects after 1984.