Ordos area is the desert-wind erosion desertification steppe transition zone and the complex ecological zone. As the research area, Ordos City has the similar natural geographic environment to ShenDong coalfield. To research its ecological patterns and natural evolution law, it has instructive to reveal temporal and spatial changes of ecological environment with artificial disturbance in western mining.
In this paper, a time series of AVHRR-NDVI(Normalized Difference Vegetation Index) data was used to monitor the change of vegetation temporal and spatial dynamics from 1981 to 2006 in Ordos City and ShenDong coalfield, where were as the research area. The MVC (Maximum Value Composites) method, average operation, linear regression, and gradation for NDVI change trend were used to obtained some results, as follows: ¬vegetation coverage had obvious characteristics with periodic change in research area for 26 years, and vegetation growth peak appeared on August, while the lowest appeared on January. The extreme values in Ordos City were 0.2351 and 0.1176, while they were 0.2657 and
0.1272 in ShenDong coalfield. The NDVI value fluctuation was a modest rise trend overall in research area. The extreme values were 0.3071 and 0.1861 in Ordos City, while they were 0.3454 and 0.1904 in ShenDong coalfield. In spatial distribution, slight improvement area and slight degradation area were accounting for 42.49% and 8.37% in Ordos City, while slight improvement area moderate improvement area were accounting for 70.59% and 29.41% in ShenDong coalfield. Above of results indicated there was less vegetation coverage in research area, which reflected the characteristics of fragile natural geographical environment. In addition, vegetation coverage was with a modest rise on the whole, which reflected the natural environment change.
The aim of obtaining a continuous space distribution of mining-induced subsidence in a large scale, damage intensity,
and its dynamic evolution, furthermore understanding the rule of the subsidence, is extracts finally the surface movement
parameters of the mining-induced subsidence. Using 9 issues of ENVISAT ASAR data over 2009 year and by both of DInSAR
processing algorithms, an atmospheric effect can eliminate and real subsidence region can be determined by a
cumulative phase 2 PASS D-InSAR, and a temporal decoherence effect can be reduced and each stage deformation can
be extracted by an adjacent phase 2 PASS D-InSAR.
Results are as follows: (1) 8 phase variation regions according with the criterion of mining subsidence are extracted from
70 phase variation regions with the two methods of D-InSAR. (2) 16 main profiles (along with the strike, dip) of
subsidence contained in 8 typical subsidence basins are obtained. Annual maximum subsidence reaches -210.0mm
during the period of image acquisitions, from Jan. to Sep. 2009, the maximum rate is ±1.2 mm/d, and the average daily
subsidence rate is ±0.60mm/d. (3) Sampling the minimum Standard Deviation(SD) is ± 4.3 mm, maximum SD is ±
8.1mm, and the total SD Mean is ± 5.9mm. Root Mean Square Error (RMSE) of data processing is ± 0.41 mm, the
maximum RMSE is ± 0.74 mm, total average RMSE of observations is ± 0.55mm.
The monitoring accuracy is self-consistent at sub-centimeter level, and it can reveal the rule of mining subsidence and
extract partly parameters of mining damage. The result presents also that mine surface by the impact of mining activities
are frequent and severe, deterioration of surface stability, and the risk of collapse, slip or mudslides is higher than outside
coalfield.
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