Water from the Des Plaines River, backed up behind an ice jam in the bend of the river near the Riverside Public Library, overflowed the banks and poured into Swan Pond Park late Tuesday night, once again flooding the area.
But unlike flooding that occurred in the park twice during January and February of 2014, it’s unlikely the flooding this time caused the kind of damage to the landscape that is still evident two years later.
“This was a quite drastically different event than 2014,” said Riverside Public Works Director Edward Bailey. “In 2014, both of the floods were preceded by longer cold snaps and the ice on the river became thicker. And then we had an inch of rain, which really blew up the river and those big pieces of ice started flowing through Swan Pond.”
This time around, by daybreak on Wednesday, Feb. 17, Swan Pond Park resembled a smooth sheet of ice, while a narrow channel had been cut by water through the icy river, quickly allowing the level of the river to recede to normal.
About 2 p.m. on Monday, Feb. 15, the National Weather Service gauge on the Des Plaines River near the Barrypoint bridge recorded a crest of 7.37 feet, which is slightly above flood level.
The river never threatened homes in Riverside or even in Riverside Lawn. The crest held for about 24 hours and then began to fall after about 2 p.m. on Feb. 16 as the water began seeping and then pouring into Swan Pond Park.
Between 2 p.m. on Feb. 16 and 8 a.m. on Feb. 17, the river level fell to 2.7 feet as the ice jam broke.
Bailey said the river water overtopped the retaining wall of Swan Pond Park in a couple of low spots about halfway between the bottom of the Burling Road sledding hill and the former site of the Fairbank Dam.
He observed some erosion on the stream side of the walking path closer in, near the vicinity of the drainage culvert, but there was no evidence that any major damage had been done to the park.
“It’s not as severe as in the past,” Bailey said. “I wouldn’t expect near the amount of damage as last time. Maybe some surface erosion by the culvert.”
Bailey said the drainage culvert appeared to be working as intended and said he didn’t see any evidence that water back-flowed into the park from the culvert.
What does the future hold?
A critical question for the future use of Swan Pond Park, however, remains. The park has flooded routinely in recent years. After a rain of any significance, water pools in the low area in front of the new drainage culvert and ice jams have caused winter-time floods three times within the past two years.
Floods from ice jams, anecdotally at least, are not remembered as common prior to 2012, when both the Hofmann Dam (formerly located west of the Barrypoint bridge) and the smaller Fairbank Dam (formerly located about 350 yards downstream of the Hofmann Dam) were removed.
Could the removal of the dams have changed the hydrology of the river downstream, resulting in ice jamming at the river bend near the library?
It’s hard to say, said Jeff Zuercher, project engineer for the U.S. Army Corps of Engineers, who was closely involved in the dam removal project in 2012.
Certainly, January and February in 2014 were unusual in that a large amount of snow fell on the area, which then entered a prolonged, deep freeze. Ice on the Des Plaines was easily 10 inches to a foot thick. A warm-up, combined with heavy rains, then resulted in violent flooding in Swan Pond as storm runoff ran up against the thick ice jams in Riverside.
But this week’s situation was different. Temperatures got cold, but ice was only a couple of inches thick, there was little in the way of rain, and the warm-up wasn’t drastic. Still, the ice jammed and the river flooded.
Zuercher said he talked with an Army Corps hydrologist about the situation, but they couldn’t arrive at a conclusive theory.
“We can’t definitively rule out that removal of the dams has changed the location or formation of ice jams on the Des Plaines River,” Zuercher said. “It is possible that removal of the Fairbank Dam and/or Hofmann Dam has made enough of a difference that ice jams are now forming at the bend in the river. … We also could not definitively say that these ice jams are caused by these actions either.”
Whatever is happening in that area Zuercher attributes to nature taking its course. It was clear that the removal of the dams would change the river. Just how it’s changing we’re starting to find out.
“We are confident that returning the river to its natural state will allow it to seek a natural balance where in the future it will create its own path around this issue,” Zuercher said.
What does the future hold for the park? Will it ever be considered again for active recreation — at one time the Parks and Recreation Department used it for youth soccer — or will it come to be viewed as a natural wetlands area.
The Riverside Landscape Advisory Commission, which is in the midst of finalizing its Landscape Master Plan for the village, calls out Swan Pond Park specifically as needing attention.
Cathy Maloney, chairwoman of the commission, called Swan Pond Park “a priority.”
“Whatever solution is developed for Swan Pond, it must consider the likely occurrence of flooding,” Maloney wrote in an email to the Landmark.
The draft landscape plan addresses Swan Pond and its propensity for flooding specifically.
“Swan Pond is a high-profile and much-beloved Riverside landscape, but it is continually threatened by major flooding and winter ice damage,” the plan states. “Funds must be directed to relocate the plants that were moved by the flooding/ice. Once those plants are properly placed, public works and the LAC should evaluate the landscape effect of the floodplain-habitable plants and reassess possibilities.”
The plan also talks about the ridge that surrounds the park and the need to control invasive species that all but obscure views of Swan Pond during the summer. And it calls for a solution to the walking path along the river and the growth adjacent to it on the river side.
“A shoreline restoration consultant may be needed to help develop alternatives to long-term maintenance of the planted areas adjacent to the walking trail,” the plan states. “While the floodplain and hills of Swan Pond can be treated with a more naturalistic approach, a suitable solution for the walkway that accounts for frequent flood events needs to be developed.”