Study on the Landscape Ecological Change of Watershed with Natural Disaster

Abstract

The landscape, which is changed as with anthropological or natural disturbance, is a heterogeneous land area composed of cluster of interacting ecosystem that is repeated in various sizes, conditions, topography, and spatial relationships. Evaluating the transition of landscape can emerge that ecosystem processes are being influenced by disturbance. For this reason, it is essential to use appropriate mapping techniques and quantitative methods to assess landscape condition within different disturbance regimes. Landscape metrics were calculated for segmented areas of homogeneous land use in watershed to allow understanding and characterization of ecosystem. The Chen-Yu-Lan watershed, located in central Taiwan, is a sensitivity area for natural disaster such as earthquakes and typhoons. In this study we focus on how the natural disasters affect landscape patterns. The remote sensing technology has great potential for acquiring the detailed and accurate land use information for management and planning of watershed. Hence, we choose time series SPOT images which date on 1996/11/8 (after Typhoon Herb), 1999/3/6 (before the Chi-Chiearthquake), 1999/10/31 (after Chi-Chi earthquake), 2000/11/27 (after Typhoon Xangsane), 2001/11/20 (after Typhoon Toraji), respectively. The study shows that landscape metrics can measure the effect of typhoon and earthquake disturbance regime. The analysis shows that evaluating landscape transition can contribute more detailed information for managing ecosystems.