Field guide

Creek walks

Walking a creek in winter tells you more about a watershed than any amount of reading. You are looking for four things, and you can learn all four in an afternoon.

Riffles

Shallow, fast, broken water over gravel. Riffles oxygenate the creek and, when the gravel is clean and roughly the size of a walnut, they are where salmon and steelhead build redds. Gravel packed hard with fine silt is the single most common sign of an impaired watershed — and the most direct link to upstream runoff.

Pools

Deep, slow water, usually scoured out below a log jam or a boulder. Juvenile fish hold in pools through summer. A creek that has been cleared of woody debris loses its pools and, with them, its rearing habitat.

Undercut banks and shade

Overhanging alder and willow drop insects into the water and hold summer temperatures down. Bare, hard-armored banks do neither.

Large woody debris

Fallen trees in the channel look like a mess and are the opposite. They slow flows, sort gravel, and dig the pools. Leave them where they lie.