  We investigate the integer quantum Hall system in a two dimensional lattice
model with spatially correlated disorder by using the efficient method to
calculate the Chern number proposed by Fukui \textit{et al}. Distribution of
charge density indicates that the extended states at the center of each Landau
band have percolating current paths, which are topologically equivalent to the
edge states that exist in a system with boundaries. As increasing the strength
of disorder, floating feature is observed in an averaged Hall conductance as a
function of filling factor. Its relation to the observed experiments is also
discussed.
