3.2 Land use/cover change detection
Results showed that the ‘water’ and ‘rocks’ thematic classes had a negligible decrease during the studied period. The ‘water’ thematic class, which included rivers, water channels and big man-made pools, might exhibit inter-annual change due to fluctuation of precipitation levels for the three studied periods (figure 3). The presence of snow in one of the images for 1998 could affect the extent of the ‘rangeland type II’ thematic class. ‘Industry’, ‘forest’, ‘residences’ and ‘agriculture’ thematic classes increased from 1985 to 2016, while the ‘rangeland type I’ thematic class steadily decreased (figure 4). From 1985 to 2016, the ‘forest’ thematic class increased ten times, the ‘industry’ thematic class three times, and the ‘residences’ class two times.
<Figure 3>
<Figure 4>
A detailed visual inspection of classified maps revealed that the ‘agriculture’ thematic class expanded mostly at the expense of the ‘rangeland type I’ thematic class, with 3.3% growth in area from 1985 to 2016 (table 2, table 3). Visual qualitative inspection of land use/cover change also revealed forests and urban greenery that had been planted mainly around the industries and mines from 1985 to 2016 (figure 5). Spatial growth of residential areas from 1985 to 2016 primarily occurred at the expense of agricultural lands, ‘rangeland type I’, and in close proximity to existing residential areas and roads (figure 5).
<Table 3>
<Figure 5>
Results also showed that the conversion of ‘agriculture’ to ‘residences’ and ‘forest’ was more pronounced from 1998 to 2016 than from 1985 to 1998, which was different for the transition from ‘rangeland type I’ to ‘industry’ (which dominated from 1985 to 1998).