The entire area was divided into two broad groups
of major landforms, with and without important relief
expression. For the first group, we differentiated
four geomorphic regions: very low hills, low hills,
high hills, and sierras. The second group was formed
by four other regions: valleys, plains, highplains, and
piedmonts. The thresholds for discriminating criteria
Ž . relief amplitude and slope steepness are given in
Tables 1 and 2, respectively, for both groups of
landforms; in this way, the method can be replicated
in similar environmental conditions.