Complex sentence: Bajadas are common in dry climates (i.e. the Southwestern US) where flash floods deposit sediment over time, although they are also common in wetter climates where streams are nearly continuously depositing sediment.
Split into simpler sentences: Bajadas are common in dry climates (i.e. the Southwestern US) where flash floods deposit sediment over time. Though they are also common in wetter climates where streams are nearly continuously depositing sediment.