Bigger storms are happening more often
May 21, 2012
A pair of environmental groups has put out a report
saying that severe downpours are happening more often
in Iowa and around the Midwest than they did 50 years ago. The organizations involved aren't neutral on their conclusions -- they specifically advocate about environmental issues, and specifically tie "extreme weather" to climate change
. But a Federal report from half a century ago
illustrating rainfall frequency maps shows most of Iowa and Nebraska under a contour that would make a one-hour, 3" or 4" downpour a once-in-a-century event, and that any storm dropping 5" to 7" in 24 hours would have qualified as a once-in-a-century event as well. But we know from our own local experience that Dubuque had a 15" downpour in 18 hours
last July, central Nebraska had a one-day storm with 8" to 11" of rain in 2005
, and 2.5" and 3" one-hour downpours
aren't uncommon. So it's indisputable that extreme rainfall is happening more than the old models predicted.
This highlights the importance of stormwater management
. Good stormwater management is a tricky subject for many communities: It requires a lot of spending on infrastructure as an insurance policy against a low-frequency but high-impact event. (Big flash floods don't happen often, but when they do, they often affect lots of people and do lots of damage.) That can make it difficult for elected officials to risk their political futures by asking taxpayers to invest in stormwater management, since they aren't likely to be hailed as heroes for having done the right thing -- if a stormwater control system works right, few people are going to acknowledge the foresight of the planners and officials who implemented the controls; they're only likely to punish those who appear to be at fault if something goes wrong. This is an important industry issue for the water/wastewater sector, and one with no obvious "magic bullet" solution.
Related items: flood cleanup pumps
• water-control gates
• portable engine-driven pumps for bypass