  We study numerically the avalanches in a two--dimensional critical height
sandpile model with sand grains added at the center of the system. Smaller
avalanches near the center of the system are isotropic. Larger avalanches are,
however, affected by the boundary of the system, to a degree that increases
with the avalanche size. Up to linear system size $L=1001$, we did not find an
obvious indication for lattice--induced anisotropy.
