Application of photogrammetry and markov model on monitoring human disturbance in shihmen reservoir catchment

Forest watershed is often regarded as environmentally sensitive areas for watershed resource conservation because of its dynamic and fragile terrain. The watershed ecosystem is easily disturbed by many natural and man-made factors, especially improper land use that result in the fragmentation of landscape and the occurrence of landslide. This study aims to assess the effect of human activities on Shihmen reservoir catchment in the northern Taiwan using photogrammetric technique and Markov model. Firstly, Digital Aerial Survey System was used to interpret main land-use types and human development area in 2004 and 2007, and understand the dynamics of human activities and landslides from 2004 to 2007. Secondly, a transition probability matrix was applied to investigate the conversion relationship between human development and landslide. Finally, a Markov model was established to predict the extent of land use changes in the future. The result showed that the study area was classified into five land-use types (i.e., forest, human development, road, water, and landslide). Both human development and landslide area revealed an increasing trend from 2004 to 2007. Moreover, the result of transition analysis of land-use change pointed out that human development has the most conversion of 0.4% into landslide among four land types. The simulation of land-use change using the Markov model indicated that, based on the current land dynamic, the occurrence of landslides in the Shihmen reservoir catchment would increase due to the frequent human activities.