DELHI, Iowa – The flood that ravaged human-built structures last month along the Maquoketa River may have even longer lasting repercussions on the natural environment.

“The flood has had a negative impact. How severe it will be and how long it will last remain to be seen,” said Dan Kirby, the Department of Natural Resources fisheries biologist who manages the Maquoketa — one of Iowa’s premier streams, flowing through one of its most scenic valleys.

Trees along the river below the failed Lake Delhi dam have been festooned with boats, docks, picnic tables and other ruined accouterments of life on a lake that no longer exists.

The river’s banks have been harshly eroded, choked with stacks of uprooted trees and buried under thick deposits of mud and sand.

Though it’s too soon to tell, those same deposits also may cover portions of the rocky stream bed, which for generations has nurtured the state’s foremost smallmouth bass fishery in a 4.5-mile-long, bluff-walled gorge below the dam.

While the debris can eventually be removed, Kirby said, sedimentation will be a chronic problem that threatens the long-term health and beauty of a river long popular with anglers, kayakers, canoeists, hikers, bird watchers and hunters.

The lake bed consists of deep layers of silt deposited since the dam was built more than 80 years ago. As the river channel cuts into the bed and whenever heavy rains fall upon the bed, more silt will wash into the river, Kirby said.

Nearly four weeks after the catastrophic dam failure, the river still runs the color of chocolate milk, preventing biologists from documenting the amount of rocky substrate that has been covered with silt.

The river’s cloudiness is partly from additional rains that have fallen on the watershed since a July 22 cloudburst dumped more than a foot of rain on parts of Delaware County. The deluge raised the river to record heights that two days later washed away an earthen portion of the Delhi dam, unleashing a wall of water that battered the valley below.
“It’s really scary. I have serious doubts that the river will bounce back to its former condition in my lifetime,” said Mike Jacobs, 54, of Monticello, who has fished the waters below the dam scores of times in the past 15 years.

Jacobs said he believes as much as 75 percent of the formerly rocky stream bed will be covered with sand and silt.

“A lot of sediment has been delivered, and I assume a fair amount of the river’s rocky bottom has been covered,” Kirby said.

The effort to quantify the damage won’t begin until mid-October when DNR fisheries personnel conduct their annual survey of fish stocks in the river.

The survey will help biologists understand river-bottom conditions and the proportion of fish that survived the onslaught.

Efforts to clean up the debris will likely wait until next year, said Garlyn Glanz, director of the Delaware County Conservation Department.

The department owns and manages the Shearer and Lyle Retz public recreation areas, the two principal public accesses below the dam.

Glanz said the debris cleanup has a lower priority than restoring the county’s flood-damaged camping and day-use parks.

Cleanup also will be complicated by extremely limited river access for vehicles and equipment, and delayed by the need for the owners of the damaged and destroyed property to document their losses for insurance purposes, he said.