||Gradational activities are those that tend to reduce the land to a common elevation
by removing material from higher places and depositing it in lower places (Chamberlin
and Salisbury 1904, page 2), without necessarily reducing the angle of slope at every
point. The work of streams and landslides is almost entirely in the gradational modes.
However, this tendency is opposed by many processes that commonly act in an anti-gradational
mode. These modes are characteristic of volcanism, diastrophism and various kinds
of human and biological activity.
However, many engineering works involve erosion and aggradation because these gradational
modes use less energy than anti-gradational modes. For the same reason, erosion and
aggradation may easily be induced unintentionally by land use (pages 92–96).
To judge the mode of geomorphological activity responsible for a given landform element,
the observer must visualise a former surface that has suffered distortion, burial
or removal of material, and seek evidence that such activity has taken place. (Information
on soil and substrate materials relevant to this investigation should be recorded
as specified in other sections.)
Allow for the recording of more than one mode of activity, together with options concerning