ABSTRACT
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. As Heraclitus said: “You cannot step in the same river twice, because the second time it is not the same river.” Rivers are part of a larger landscape, veins in a network that carries water, sediment, and wood, and through which fish migrate—most famously, salmon to their natal spawning grounds.
