More on rapid Texan canyon as research student writes: Your article on the “new canyon” reminded me of the birth of the Salton Sea nearly a century ago. If I remember correctly, the out-of-control Colorado River cut out a new channel even faster than one mile a day – and for much longer than three days. Indeed, the Colorado would have changed course permanently if it hadn’t been for the desperate (and very costly) efforts of American civil engineers.

Incidentally, a rule of thumb in civil engineering is that the erosive power of a stream is proportional to the third power of velocity. Thus, doubling the flow-speed increases its erosive power eight-fold. This cubic-power law also works for wind-generated electricity within the limits of engineering design (e.g. for winds up to a maximum of 50-60 km/h). From Nathaniel Jewell, PhD student, School of Mathematical Sciences, The University of Adelaide, Australia.

Evidence News 28 November 2007