Take action against street flooding in your community
The expression “when it rains, it pours” apparently became a more accurate description of rainfall events in Illinois the past three decades.
New research to update Bulletin 70, which measures rainfall frequency distribution and hydroclimatic characteristics of heavy rainstorms, found rain events increased in intensity across much of the state the past three decades. And, the trend continues.
Jim Angel, recently retired state climatologist who spent 34 years at the Illinois State Water Survey, released the latest findings after conducting the original research for Bulletin 70 in the 1980s. “We’re seeing more intense and more extensive storms. Getting things like 2-, 4- or 6-inch rain events are becoming much more common than they used to be,” Angel said. “And it covers a much larger area,” he noted. “Several events this year already covered parts of the entire state, whereas normally you think of a heavy rainfall from a big thunderstorm covering part of a county.”
The latest rainfall frequency research, which used data from 1948 to the present at 180 stations around the state, prompted an upward adjustment for historic storms, such as the occurrence of 50- or 100-year rainfall events. Those baselines were established to help city engineers design infrastructure capable of handling big rain events. “It’s no surprise the new numbers in many cases are much higher,” Angel said. “We’re seeing a trend of wetter conditions across Illinois, especially with heavy rainfall events. As a result, our expectation of what those 100-year storms look like increased over time.”
Why do some areas endure multiple 50- or 100-year rain events in shorter periods of time? “It’s an unfortunate carryover of the terminology, that we expect them to occur every 100 years on average,” Angel said. “Really, a better way to think about it is as a 1 percent chance of that storm any given year. And they can be clumped together, especially when we get an extended wet period.”
Angel said the rise in rainfall frequency findings are most pronounced in northern Illinois with a modest boost in central Illinois. And, while parts of southern Illinois experienced significant flooding this season, rainfall frequency there actually remains close to the same in recent decades. This past winter was the sixth-wettest on record, following the 19th-wettest September on record in the state.
In fact, stronger rainstorms and flood events typically cause more damage than any other natural disaster in Illinois.
“This is probably the biggest impact of climate change of any sort we’ve seen in Illinois, if you add up the dollar amounts,” since the 1980s, said Angel, who recently received the Prairie Research Institute’s research scientist career achievement award.
Since there’s not much we can do to prevent storm flooding, it’s crucial to prevent the stormwater system from becoming overwhelmed. To do so, our neighborhoods must be committed to: (1) reducing the amount of rain that goes down the storm drain and (2) giving stormwater runoff a clear path to flow through on its way through the system.
Just think of it like the drain in your kitchen sink: If you poured a cup of water into the sink it would drain in seconds, right? But what about a 5 gallon bucket of water? The sink isn’t able to process 5 gallons of water as quickly as a cup of water. This, in a nutshell, is what happens when too much rain falls on hard surfaces (i.e. roofs, sidewalks, roadways, parking lots, etc.) and runs off into the stormwater system. Finding other ways to manage stormwater runoff is so important to flood prevention.
Now, imagine you’re back at your sink only this time the drain is clogged. When you pour the cup of water into the sink it will not drain as quickly as before. And it would empty even slower with 5 gallons of water! Yard waste like grass clippings and fallen leaves as well as everyday litter are frequent offenders for clogs in the stormwater system that contribute to flooding.
Here’s what you can do to take action against street flooding in your community:
Install a rain barrel to capture rainwater that can be used for outdoor watering.
Divert gutters towards rain gardens, flower beds and grassy areas so water has a chance to soak up.
Plant more flowers and trees – they soak up water better than turf grass, bare spots and concrete!
Support green infrastructure projects in your community that will reduce both flooding and water pollution.
Keep your gutters and downspouts clean and free flowing.
Don’t litter and pickup trash around your community – even if it isn’t yours.
Keep your roadside curb and ditch clear of litter and overgrown vegetation.
Only put rain down the drain. Grass clippings and fallen leaves cause troublesome clogs in storm drains, pipes and ditches.