IT’S not just torrential floods that carve out river valleys. The persistent action of gentler, normal flows turns out to do a lot of the work too.
The finding helps settle a long-running argument about whether floods or normal flow cause the most erosion. Careful measurements in the Liwu River in Taiwan’s central mountain range show that while both are important, normal flow does the most digging at the bottom of the river channel (Science, vol 297, p 2036).
It still takes a big flood to cut into the valley walls and widen the stream, however, according to Rudy…
