Monitoring of landscape dynamics in a typical reservoir system in the Northern Taiwan

As Taiwan is densely populated and the use of land is nearly saturated, human activities gradually moved to the hillside and mountainous area in recent years. Scattered human development patches in watershed landscape not only increase the occurrence of landslides and debris flow, but also deteriorate the integrity and functionality of the watershed ecosystem. This study takes the Shihmen reservoir catchment in the upstream of Tahan river as an example to investigate the effects of human activities on the watershed landscape. Land use maps of 2002 and 2007 were produced by digital photogrammetry to compare the difference of human development between the two periods. Six landscape indices were used to assess the effects of human development on the landscape integrity of Shihmen area. Finally, a binary logit model was applied to examine the possible factors contributing to the observed land cover change. The results of this study showed that the human development in the Shihmen area was expanded from 3683.4ha in 2002 to 3778.0ha in 2007. Landscape structure comparisons indicated that number of patch, shape index, fractal dimension, Shannon diversity index, and Shannon evenness index were increased between the two periods due to the disturbance effect of human activities. Conversely, the mean patch size was decreased. The result of logit regression analysis revealed that the occurrences of human development were related to slope, distance to landslide, forest, and previous human activity area.