| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋環境資訊系 === 103 === This study aims to explore the landscape changes of Tamsui river basin, so six satellite image data are chosen from FORMOSAT-2 of the years from 2004 to 2013. In addition, the supervised classification method of maximum likelihood is applied. The accuracy of the supervised classification method reaches more than 90%, and most of the Kappa values are over 0.89.
The results show how the proportions of both water areas and coastal sand areas changed, respectively in the nature preserve zones and Tamsui river basin from 2004 to 2013. The lowest ratio of water areas is found in 2008, respectively 32.51% for Tamsui river basin, but 0.28% for the nature preserve zones. The minimum ratio of coastal sand areas appeared in 2012, respectively 4.50% for the former, but 1.06% for the latter, and it’s the minimum ratio of six years. Both of the results are corresponding to the data of tidal changes, observed in Tamsui river estuary and the data of water level provided by the Water Resources and Sewerage Bureau (WRSB). Similarly, the highest tidal level appeared in 2012, but the lowest in 2008.
In Tamsui river basin, the domains of mangrove during these six years were 129.4, 90.0, 98.7, 84.0, 85.5, and 120.2 ha, respectively. On the contrary, in the nature preserve zones, the mangrove areas are 80, 71.7, 78.6, 72.7 , 70.2, and 86.2 ha. Obviously, from 2004 to 2013 the variations of mangrove areas are consistent both in Tamsui river basin and the nature preserve zones.
In Tamsui river basin, the domains of vegetation, including the classes of grass and mangrove during these six years were 637.5, 586.6, 453.7, 448.5, 539.4, and 450.5 ha, respectively. On the contrary, in the nature preserve zones, the vegetation areas are 117.9, 113.9, 117.4, 121.6 , 123.4, and 122.8 ha. Obviously, from 2004 to 2013 the variations of vegetation areas have changed more violently and there is a slight downward trend in variations; meanwhile, the variations are stable in the nature preserve zones.
Maybe, most of the mangroves in the nature preserve zones have grown prosperous, so compared with those in the other areas along Tamsui river they are more intensive. Therefore, the classification is more concentrated, and the errors of interpretation may be prevented. In this study, the decrease of mangroves in south coast of Shetzu is considered as the result that the WRSB hewed some of them in 2007. In addition, the invasion of typhoons, abundant rainfall, and sewage, all will affect the results of the classification.
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