Experts say serious flood frequency may increase - Time will tell if the record floods of 2008 are an aberration or the beginning of a trend. But some experts say the likelihood of serious floods in Iowa is increasing in frequency. Increases in Iowa's annual precipitation, coupled with anticipated precipitation increases linked to global warming, greatly increase the likelihood of more frequent and severe flooding. Since 1950, Iowa's annual precipitation has increased by 10 percent, which in turn has doubled the amount of water carried by rivers in the state. A 10 percent increase in precipitation equates to roughly 3 more inches per year, making rivers six times more prone to flooding because it all runs off. What had been considered a 100-year flood is now a 17-year flood. Though the parameters of a 100-year and 500-year floods have increased dramatically, the odds of another flood like the one in June are about 1 in 250 in a given year. There was a lot of rain, but the rain was not as extraordinary as the flood. The timing and spacing of the rainfall, combined with drainage patterns within the Cedar Rapids watershed caused the runoff to converge just upstream of Cedar Rapids on June 13. That created a "traffic jam" which led to the large-scale flooding. Image: Cedar Rapids, Iowa, 2008
Adapting to the damaging effects of climate change, plants are gradually moving to where temperatures are cooler, rainfall is greater, f...