We may say that rivers have distinct personalities: forms and
habits determined by their geologic setting, their flow regime-
those seasonal and year-to-year patterns of floods and dry-
season low flows-and their sediment load, that is, how
much mud, sand, or gravel they transport. Rivers are naturally
dynamic, changing in response to wet years and dry, the seasons,
the odd landslide, and even the trees that fall in the channel.