DEFORESTATION IN THE DOKI RIVER BASIN AND ITS RUNOFF CHANGE

Using multi-temporal satellite data, the change of land covers in the Doki River basin and its impact on hydrological data for the past 17 years were examined. The land cover classification maps in 1986, 90, and 95 were obtained using multi-temporal Landsat TM. From these results, its observation data were divided into three periods: the first period (1981-86) with the decrease of paddy fields, the second period (1987-92) with the increase of agricultural fields and little urbanization and the third period (1993-97) with golf course development. Through the three periods, deforestation had been carried out and the ratio of forest in the basin decreased from 83 to 76 %. During the observation period, evapotranspiration decreased by 16 % and runoff ratio increased by 13 times. Moreover, seasonal profiles in evapotranspiration showed different patterns each period, which seemed to be affected by different-typed development.