Satellite image processing methods for land use and land cover mapping and change detection and applications to landslide studies in the Three Gorges Area, China.

摘要

The mountainous landscape in the Three Gorges Area (TGA), along Yangtze River, China has been experiencing drastic changes since the commencement of the construction of the Three Gorges Dam in 1994. Landslide frequency has increased in areas with a recent increase in human activities. However, information about landscape changes and their impacts on landslides is scarce. This research attempts to develop image processing methods for monitoring land use and land cover (LU/LC) changes and their impact on landslides in the mountainous TGA using remote sensing technology. The case study was conducted in Zigui County of Hubei Province in China. Both optical and radar satellite images were applied for the LU/LC mapping in this study.;In this thesis, a procedure using a decision rule-based classification method is developed to combine spectral, textural, terrain information and expert knowledge in the optical satellite image classification of this complicated, high-relief environment. With this method, multi-temporal images are classified to produce the LU/LC maps during the study period 1987--2006 with overall accuracies between 73.4% and 89.5%. The results show that the main trend in LU/LC change in the study area throughout the monitoring period was a steady reduction in natural vegetation areas. About 32% of the total area of natural vegetation, including forest, shrub and grass lands, was lost to built-up areas, crop fields and orange orchards.;The application of satellite radar imagery is investigated because of the difficulty in optical data acquisition over the constantly cloud covered study area. A new method is developed for minimizing terrain effects in radar images. With this method, terrain effects in the radar images are effectively reduced and LU/LC mapping accuracy using radar images is improved. After terrain effect correction, multi-polarized radar data from different satellite sensors are assessed for LU/LC mapping.;The impact of LU/LC change on landslide hazard is assessed by logistic regression analysis. The results show that although many landslides occurred under the naturally favorable landslide conditions, human activities also caused many landslides to occur in some naturally unfavorable areas.;Key Words. remote sensing, land use and land cover, change detection, landslide hazard, Three Gorges