I love the idea set forth by Brian R. this month. Anne J.'s example of fan and irrigated valley interface sparked my memory of some interesting constrasting examples wherein the full geometry of alluvial fans is laid bare by irrigation on them.
Alluvial fans are often milked for all they are worth in many of the world's deserts. Particularly well-watered fans display a remarkable palimpsest of culture and fluvial geomorphology.
This first example is from Afghanistan:
This huge example is from nearby Turkmenistan:
Of course, Xinjiang Uygur has some excellent examples:
Including this particulary pathological, almost cubist, palimpsest scene: