> -- it's hard to make meaningful predictions about human
> values 100 years from now.
A one-hundred-year event has a 1% chance of occurring in any
year. No need to wait 'til 2067. As Earl points out, our
experience is short. The recent floods in Fort Collins,
Colorado overwhelmed facilities reportedly designed against the
100-year event. The instant the floods occurred, though, the
"100-year event" was demoted and replaced with a new, more
severe one.
Working strictly with the statistics of Lee Ferry flows, we
have synthesized 1400 years of inflows for the Colorado River
system. In that 1400-year sequence, we found one _extreme_
event with an annual flow of 60-70 maf (I can't recall
exactly). That's the 1400-year event, based on roughly 70
years of record. Industrial-strength extrapolation and perhaps
lacking a physical basis. A doozy, nevertheless.
One of the less-appreciated effects of climate warming (whether
anthropic or natural) is an increased frequency of extreme
precipitation events. This is because a warmer atmosphere can
hold more water vapor, which in turn stores energy. Just like
building bigger dynamite warehouses increases the frequency of
bigger booms, more severe storms should result from a warmer
climate.
> In practical terms, what this means is that truly unrunnable
> rapids wil develop, which further implies either 1) human
> intervention to open them up (explosives), or 2) the river will
> be closed to all boats that can't be portaged. Number 1) is at
> this point unlikely,
In about '76 or '77 I was at the Interagency Whitewater
Committee meeting, a confab was held annually for all federal
river managers and at the same time and the same place as the
annual Western River Guides Association meeting. It was
winter, maybe January, and word came back that a science trip
had encountered a rock fall in the 20's (Tiger Wash, maybe) and
that it was impassable to outriggers. Discussions of "human
intervention" followed.
Ben
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