Remote Sensing Application Study on Environmental Hazards in Shaanxi, China
III. Landslide and Debris Flow Hazards
As the geomorphic features remain and effects of human activities continuo, landslide and debris flow hazards are always in a developing tendency and they are the main forms of hazards of debris flows happening all over the province. Since each of these hazards is in a small scale, it is not easy to be recognized in the images. So the images were enlarged to 1:50,000, no matter satellite or airborne images, the signs are relatively much clear, the stable and active landslide and debris flows can be defined. In Northern Shaanxi, these hazards are in large areas but concentrated in several regions. They appear to be developing along deep loess valleys in Guanzhong, and can be divided into 8 dense concentrated areas and 4 concentrated areas. While in the south of the province, they appear to be in separate distributions, and some of them in zones, forming heavy disastered areas.
IV. Active Structures, Ground Fissures and surface subsidence Hazards
Active rifting is concentrated mainly along the boundaries of Guanzhong areas in the center of Shaanxi, and it is clearly shown in the remote sensing images, spreading in light grey line shape. And secondarily it appears in the mountain areas in the South of the province. Such
active structures often cause landslide, debris flow hazards to happen. And in the center and the east parts of Guanzhong Basin, especially in Xian, concentrated are serious damaging ground fissures. Through interpretation of remote sensing images, most of them shown are to be in certa9in directions and zones, making a hint that they are controlled by structures, at the same time, indicating that the controlling structures are still in activities. On the surface, their formations are normally in conformity with regional tectonic lines, their development is in relation with excessive pumping of underground
V. Ground Water Pollution
Remote sensing image captured in dry season and computer processed bear certain image features for water pollutions, of which the normal bear certain image features for water pollutions, of which the normal colour has changed ( such as the waste water from iron and steel works, from chemical works. Power plants using coal) and water polluted with sand and soil, water additionally polluted. These features are sometimes even very clear. Clear water is in deep blue, water with much sand and soil is in light grey or grey. And when clear water is joined with sand and soil bearing water, or to say, polluted, the colour would be changed. This provides direction information for the administrations.
VI. Air Pollution
Air pollution is one of the most serious environmental hazards and is a kind of hazards still developing and concerning every individual. And this result of concentrations of lots of industrial waste gas, coal smoke and dust . Remote sensing images chosen are those taken after strong wind and they show clear states and ranges of exhausting with dust from chimneys and the polluted area concerned, of the exhaust of high temperature gas from big chemical plants chimneys. And according to the states and ranges shown and circumscribed the degrees of pollution can be define. Integrating with ground survey, the intensities of the pollution can be classified. And with comparison lution development can be studied.
VII. Thunderstorms and Hail Hazards
Though thunderstorms and hails often occur in relationship with climate changes they happen to be in regions and areas of certain geomorphy of certain features. Such as plain and hilly areas in front of mountain renges, the margin areas of the basins in the mountains. Through geomorphic study of remote sensing images, integrating weather conditions, the features of regularities of these hazards can be found out and the plans for the constructions can thus be made.
