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For Immediate Release March 19, 2008
Heavy Rain in Southern Illinois Results in Widespread Flooding
A
storm system moving slowly through southern Illinois since March 17 has produced
rainfall totals that have already exceeded 8 inches in some places south of
Interstate 70, according to State Climatologist Jim Angel of the Illinois State
Water Survey (http://www.sws.uiuc.edu),
a division of the Illinois Department of Natural Resources.
The two largest observed totals come from Anna
with 11.64 inches and Carbondale with 8.05 inches. Radar-estimated
precipitation indicates a similar range in totals
in this region.
Generally,
rainfall totals of more than 8.8 inches in 48 hours have exceeded the 100-year design
storm for southern Illinois. The measured amount of 11.64 inches in two days at Anna exceeded the threshold;
radar estimates suggest that some other areas around Anna and Mt. Vernon
may have exceeded it as well.
"What this means is that these events are
exceptionally rare with less than a one percent chance of occurring at a
specific location in any given year," says Angel.
Rainfall totals in other parts of the southern third of Illinois
ranged from three to seven inches. As a result, the National Weather Service
has issued a flood warning throughout the area.
"Our two largest measured
precipitation totals, one at Anna and the other at Carbondale, came from our new
volunteer-driven Community Collaborative Rain, Hail, and Snow network
(CoCoRaHS). You cannot have enough rainfall observations during events like
this. These volunteers, using standard equipment and standard observing
practices, are a valuable addition to our existing observation networks. We are
always looking for new observers," concludes Angel.
To find out more about this program and to
look at rainfall maps and tables, visit http://www.cocorahs.org/.
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Last Modified: November 17, 2008
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