Recently, the media reported an ecclesiastical forecast of the end of the earth. Dubbed the “rapture,” most of us are thankful it was inaccurate. But the same source, likely using the same information updated with one piece of hard fact—the non-event—now forecasts the rapture for Oct. 21, 2011. This typifies the great uncertainty in forecasting extreme events. Photo by Tom Sawyer for ENR Damage in northern Japan following the tsunami. Related Links: Tom Sawyer's ENR Report From the Disaster in Northern Japan The past decade has seen a number of lesser but quite extreme events, including Hurricane Katrina, earthquakes in
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.