Bridges damaged in Seneca, people rescued from vehicles, serious flooding as more than 6 inches of rain falls in 3 hours

Bridges were damaged and motorists had to be rescued from high floodwaters in the Seneca area, about 75 miles southwest of Chicago, when more than 6 inches of rain fell in a period of about three hours late Monday into Tuesday, forecasters said.

The National Weather Service in Chicago issued a flash flood warning at 8:42 p.m. Monday evening and upgraded it to a “considerable” threat at 10:07 p.m. Heavy showers were expected, but meteorologist Ricky Castro said the rainfall was incredibly localized, affecting eastern LaSalle County into western Grundy County.

“There were some other pockets of downpours, in much smaller areas and not nearly the intensity as in the Seneca area,” Castro said. “Sometimes it’s what happens in summertime — we get these really localized events. We’ll have one little area there that gets a pretty incredible amount of rain and outside that area is almost nothing.”

Part of a bridge at River Road and Illinois Route 170 collapsed from one side of the roadway to the other, and the driver of a pickup stuck above the gap where the collapse happened had to be pulled from the truck.

The person got out safely with help from neighbors in the area, Seneca Mayor Jeff Olson said.

“(The) driver was very lucky that his vehicle didn’t go into the creek,” Seneca police Officer Kelsey Kowalski said. “He was uninjured; he seemed fine, a little shook up.”

Part of another bridge nearby washed out.

Emergency responders said there were at least three water rescues at the intersection of West Dupont and Kinsman roads. “At least three vehicles stuck in the flooded roadway,” an agency told the weather service.

Outside the immediate area, rainfall totals were in the 1- to 3-inch range. But in that specific portion of LaSalle County, “It just sat over them,” Castro said. There were reports of 4 to 7 inches locally, he said.

Castro said a personal weather station said there had been 6.19 inches of rain in Seneca, where authorities said a bridge along River Road collapsed.

“That was the hardest-hit area, for sure,” Castro said. “There were reports of 6 to 12 inches of standing water in spots.

Authorities in Seneca warned residents to stay home during the storm and advised some roads and subdivisions were “severely flooded.”

A trained weather spotter said there was more than a foot of standing water at the intersection of South Kinsman and West Grand Ridge roads.

According to the weather service, there were several meteorological factors that contributed to the storm, including high atmospheric moisture, a slow-moving pressure system, a near-stationary warm front that had lifted north during the day and “was parked in the area of the heavy rain on Monday evening.”

Chicago will continue to see chances of showers and storms this week. There is severe storm and flood potential late with a possibility of strong winds and hail Wednesday evening and overnight, according to Lee Carlaw of the weather service’s Chicago-area office. Localized heavy rainfall may lead to flash flooding.

Storms and showers are forecast to continue Thursday afternoon, followed by a possibility of scattered storms and showers Friday.

“We’re getting into our peak flash flood time of the year,” Carlaw said. “It’s moist and unstable and we get weather disturbances that are able to set off showers. It’s not at all unusual to get localized flooding.”

For more details and an updated forecast, check the Tribune’s weather page.

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