The two physical factors (i.e., slope and elevation) showed
consistent negative effects on urban expansion for all four periods,
except elevation in the period of 1984e1992. However, the
magnitude of the unique effects of the physical factors decreased
along with the urbanization process. The physical factors were the most important variable to affect urban expansion in the early
stages (1972e1984), but they became less important than socioeconomic
factors in the following years. The decrease in the effects
of physical factors on urban expansion may be due to the
following: 1) with the urbanization process, the previously lesssuitable
areas, such as mountainous areas with high elevations
and slopes, started to be urbanized because of the shortage of land
for construction (Ye et al., 2011); 2) the advancement of technology
decreased the construction cost for locations with high
elevations and steep slopes and thus increased the likelihood of
urban expansion in the mountainous areas (Ye et al., 2011); and 3)
along with improvements in the standard of living, wealthy people
could afford the high development costs in the mountainous areas
to access better environmental quality. This change in lifestyle
further reduced the magnitude of the effects of elevation and
slope on urban expansion.