Wet opening to August; loss of trees will result in greater stormwater impacts

1.79″ of rain has fallen through the first 7 days of August, bringing the 2 1/2 week total to 7.85″. The wet pattern is expected to continue, but no flooding is expected.

In the long-term, the combined effects of the July 23 storm, which brought down a significant number of branches and uprooted a few trees, along with the continued presence of the emerald ash borer, which is causing damage to the many ash trees in Carol Stream, will affect flooding for the worse. Healthy ash trees weakened during the severe storm will become increasingly susceptible to ash borer damage, and other diseases due to stress.

Trees prevent runoff by slowing down the rate of rainfall that hits the ground and turns into runoff, and by taking up excess water through their roots and transpiring the water into the air through evaporation. (source) This effect is measured at hundreds of gallons per day, per tree; the thick canopy of trees in Carol Stream suggests that hundreds of trees transpirate removes many tens of thousands of gallons of water from the ground every day.

With hundreds of mature trees at risk of removal in the next few years, the combined effect suggests that this natural method of runoff control and floodwater reduction will be reduced over time, unless new trees are planted.

Even so, it will be 20-30 years until the full amount of stormwater and flooding detention benefits returns to the area.

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