How a river ages

A Lake District beck in spate and the Mississippi in flood are the same machine at different stations: steep and narrow, then lazy and wide.

A waterfall is a nick point walking upstream.

When the water slows, the load sits down: slip-off slope, levée, floodplain, delta, estuary.

A more aggressive neighbour can steal a headwater. The elbow is the scar.

Rain is the input. The river’s reply has a rising limb, a peak, a lag, a falling limb.